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Ana Pavlovic

Università di Bologna, Dipartimento di Ingegneria Industriale DIN, Adjunct

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Address: Via Risorgimento 2, 40136 Bologna

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Fundação Zoobotânica do RS

Cristiano Fragassa

Università di Bologna

Milos Mladenovic

Miroslav Zivkovic

University of Kragujevac

Zorana Pašalić

University of Banja Luka

IJRASET Publication

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Papers by Ana Pavlovic

Additive Manufacturing of Functional Parts Based on Material Extrusion Technology

Contemporary Materials, 2016

This paper presents the advantages and the process of making of complex functional parts using ad... more This paper presents the advantages and the process of making of complex functional parts using additive manufacturing technology. Design and manufacturing of components were performed at the Laboratory for Technology of Plasticity and Processing Systems at the Faculty of Mechanical Engineering in Banja Luka. The parts were designed using SolidWorks and Catia software packages. Then, CatalystEX and Simplify3D software packages were used to process the CAD model and to prepare it for 3D printing, which included defining of the process parameters, generating layers and support. Functional parts were produced on 3D printers based on the principle of material extrusion. The results of this study show that additive manufacturing technology, specifically technology based on material extrusion, enables very fast production of complex functional parts, with high accuracy and much lower costs and development time compared to conventional technologies.

Analysis of the suspension design evolution in solar cars

FME Transaction, 2017

The contrast between modern mobility alternatives and the seek for sustainability has been an ess... more The contrast between modern mobility alternatives and the seek for sustainability has been an essential concern for industry in the last decades, boosted by technologies that have been progressively narrowing this gap. Among them, solar cars represent a contemporary trend to supply this need. Given the complexity embraced by this technology, the attainment of an efficient design demands the improvement of every aspect of the vehicle, including its mechanics. Performing a critical role on the vehicle's stability, the suspension system of solar cars is thoroughly investigated in this work, in particular the evolution of the structural part directly responsible for undertaking the forces subjected to the wheel hub. Three different shapes made out of carbon fiber reinforced plastic are analysed and compared through static and modal finite element analysis: two front forks meant to be coupled to a wishbone joint, and a wheel hub connected to a novel sliding hub system.

Merging Theory and Experiments in a Total Quality Approach for Improving the Reliability of Large-Mass Industrial Products

In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the ... more In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the aim at improving the reliability of large-mass industrial products far beyond the product specifications demanded at the end-customer level. A stricter correlation between standard quality methods and experimental tests has to be also realized as a modern integrated tool for design and process validation

Improving Performance and Applicability of Green Composite Materials by Hybridization

Contemporary Materials, 2015

A growing concern over environmental issues and the common interest to find a viable alternative ... more A growing concern over environmental issues and the common interest to find a viable alternative to the use of glass or carbon composite reinforcements has led to an increased attention in ecologically sustainable polymer composites. These „green” materials are made by natural fibers, as reinforcement, filled with natural-organic fillers, i.e. derived from renewable or biodegradable sources. At the same time, this relatively new class of materials faces several limits in comparison to traditional composites especially regarding the properties of resistance. This paper investigates the advantages of use of combination of natural fibers for improving mechanical proprieties of „green” composite materials. At the moment, the prevailing opinion is that green composites are not usable in structural applications, and, as a consequence, have to be relegated to unworthy applications (as fillers). On the contrary, there are several evidences that mixing different natural fibers (in practice u...

Osnove Proizvodnih Tehnologija Introduction in Production Technologies Einfuehrung in Die Produktionstechnologie

Numerical modelling the ballistic impacts on flexible curtains used as safety protection in woodworking

by Ana Pavlovic and Cristiano Fragassa

DOI: 10.1177/0954406216646401, Apr 2016

Numerical control boring and routing machines use curtains made from resistant, but flexible mate... more Numerical control boring and routing machines use curtains made from resistant, but flexible materials to protect end-users from the projection of wood chips and tool pieces. These curtains allow the work piece to gently pass through, but firmly stop every small sharp piece or fragment ejected at the highest speed by fast drilling tools. Nowadays curtains are commonly made in flexible thermoplastic materials as polyamide, polyurethane, polyvinyl chloride or similar materials. Safety issues to be addressed related to the risk of projection of parts during processing are defined by EN 847-1 and EN 847-2 standards, both collecting practical experiences from manufactures and users. The effectiveness of these curtains were investigated by technical observations, experiments and even numerical simulations, but conclusive results are not available at the moment. This independent research, where ballistic impacts on flexible curtains were simulated using finite element (FE) methods, aims at verifying the effectiveness of specific protective barriers when realized and used in accordance with the UNI EN 848-3 standard. Numerical simulations permitted to verify the congruity of the main barrier’s characteristics (materials, shape, depth, mass, cost..) in relation to the projectile parameters (shape, mass, speed, direction…) identifying their mutual influence. Outcomes from this research provide useful information toward the definition of a new way for the design of efficient curtains. A comparison between numerical simulations and experimental results coming from ballistic tests was also realized, permitting to validate this predictive methodology.

Compacted and Spheroidal Graphite Irons: Experimental Evaluation of Poisson's Ratio

by Cristiano Fragassa and Ana Pavlovic

Vol. 44, No. 4: 327-332, Jun 2016

Spheroidal Graphite cast Iron (SGI), also known as ductile iron, represents a perfect material fo... more Spheroidal Graphite cast Iron (SGI), also known as ductile iron, represents a perfect material for a very large range of modern applications. It is successfully used wherever optimal strength, stiffness and even low costs are required: high values of tensile strength and Young's modulus are between its most appreciable propеrties. At the same time, nowadays, a different cast iron, known as Compacted Graphite Iron (CGI) or vermicular graphite iron, is taking the first steps in replacing SGI respect to some specific applications. It depends on a better castability, machinability and thermal resistance. CGI is an ideal cast iron in the case of components under simultaneous mechanical and thermal loadings, such as cylinder blocks and heads. Unfortunately, while SGI benefits of a wide scientific literature, CGI is a relatively unknown material. Moreover, dut to its particular microstructure, the production of CGI presents additional difficulties and it is not easy to obtain stable properties in the CGI alloy. This paper illustrates a way for the experimental evaluation of the Poisson's ratio by tensile specimens, comparing this propriety in the case of SGI and CGI.

Combining Additive Manufacturing and Vacuum Casting for an Efficient Manufacturing of Safety Glasses

by Cristiano Fragassa and Ana Pavlovic

Vol. 44, No. 4: 393-397, Jul 2016

This paper presents the possibility of integration of modern techniques of additive manufacturing... more This paper presents the possibility of integration of modern techniques of additive manufacturing and vacuum casting in the rapid manufacturing of complex parts. The prototype of safety glasses was directly developed from a CAD model, which is used as a main model for making moulds in a vacuum casting process. The development stages, which include additive production of glasses and the process of vacuum casting with the definition of material components, preheating temperature, the forming of silicone mould, the casting process, hardening and other parameters are presented in this paper. It is proved that by using this technique it is possible to produce complex functional parts quickly, with high precision, accuracy and surface quality, while significantly reducing costs of development and production compared to other similar technologies.

$Research paper thumbnail of Tribological aspects of cast iron investigated via fracture toughness$

Tribological aspects of cast iron investigated via fracture toughness

by Cristiano Fragassa and Ana Pavlovic

Vol. 38, No. 1: pp 1-10, Jan 2016

Linear-elastic plane-strain fracture toughness of metallic materials is a method which covers the... more Linear-elastic plane-strain fracture toughness of metallic materials is a method which covers the determination of the strain fracture toughness (KIC) of metallic materials by increasing-force test of fatigue precracked specimens. This method has been applied for investigating the fracture behaviour of cast iron. Two groups of cast alloys, Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) have been investigated. While SGI benefits of a wide scientific literature, CGI is a relatively unknown material despite of its large potentialities in industrial applications.

Comparison of mechanical properties in compacted and spheroidal graphite irons

by Cristiano Fragassa and Ana Pavlovic

Vol. 38, No. 1: pp 49-59, Jan 2016

Mechanical properties of cast irons are governed by the size, distribution and shape of the incor... more Mechanical properties of cast irons are governed by the size, distribution and shape of the incorporated graphite particles. In a set of experiments, two groups of cast alloys, Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were investigated. Even if the processes used for their production could be apparently considered quite similar, these two materials are characterized by a net difference in graphite particles and, as consequence, in final properties. Adding, while SGI benefits of a wide scientific literature supporting its large use, CGI is a relatively unexplored.

Improvements in wood thermoplastic composite materials properties by physical and chemical treatments.

by Cristiano Fragassa and Ana Pavlovic

Vol. 10, No. 1: pp 205-218, Feb 2016

This paper presents a short overview of the developments made in the field of wood thermoplastic ... more This paper presents a short overview of the developments made in the field of wood thermoplastic composites in terms of surface treatment, flammability, matrix/reinforcement model, properties and application of recycled polymer matrices. The usage of lignocellulosic fibers as reinforcement in composite materials demands well formed interface between the fiber and the matrix. Because of the different nature of reinforcement and matrix components some physical and chemical treatment methods which improve the fiber matrix adhesion were introduced, as well as the improvements of lignocellulosic fibers and thermoplastic polymer matrix based composites flammability characteristics. These physical and chemical treatments influence the hydrophilic character of the lignocellulosic fibers, and therefore change their physical and mechanical properties.

Analysis of flexible barriers used as safety protection in woodworking

by Cristiano Fragassa and Ana Pavlovic

Vol. 10, No. 1: pp 71-88

Machine tools use physical barriers, made by flexible thermoplastic materials, to protect the env... more Machine tools use physical barriers, made by flexible thermoplastic materials, to protect the environment and the operators against the projections of wood chips and parts of cutting tools. These barriers constitute a partial closure and allow the passage of the workpiece, being simultaneously able to contain sharp fragments projected at high speed. The present research was conducted with the aim to evaluate the real effectiveness of these barriers, to investigate their dynamic behaviour by numerical simulations. Results showed that these barriers, if properly considered, could retain heavier masses and higher speeds. The research also allowed, in fact, to investigate the influence of several factors in design, selection and use, as material, shape, position, assemblages and many others, highlighting weaknesses and identifying possible measures to increase its effectiveness.

General considerations on regulations and safety requirements for quadricycles

by Ana Pavlovic and Cristiano Fragassa

Vol. 9 - N. 4: pp. 657–674, Oct 2015

In recent years, a new class of compact vehicles has been emerging and wide-spreading all around ... more In recent years, a new class of compact vehicles has been emerging and wide-spreading all around Europe: the quadricycle. These four-wheeled motor vehicles, originally derived from motorcycles, are a small and fuel-efficient mean of transportation used in rural or urban areas as an alternative to motorbikes or city cars. In some countries, they are also endorsed by local authorities and institutions which support small and environmentally-friendly vehicles. In this paper, several general considerations on quadricycles will be provided including the vehicle classification, evolution of regulations (as homologation, driver licence, emissions, etc), technical characteristics, safety requirements, most relevant investigations, and other additional useful information (e.g. references, links). It represents an important and actual topic of investigation for designers and manufacturers considering that the new EU regulation on the approval and market surveillance of quadricycles will soon enter in force providing conclusive requirements for functional safety environmental protection of these promising vehicles.

Experimental analysis of mechanical properties of composites reinforced by flax and basalt fibres

by Cristiano Fragassa and Ana Pavlovic

Vol. 39: pp. 68-73

Modelling the Viscoelasticity of Ceramic Tiles by Finite Element

by Ana Pavlovic and Cristiano Fragassa

1736, 020174 (2016); doi: 10.1063/1.4949749, Jun 2016

This research details a numerical method aiming at investigating the viscoelastic behaviour of a ... more This research details a numerical method aiming at investigating the viscoelastic behaviour of a specific family of ceramic material, the Grès Porcelain, during an uncommon transformation, known as pyroplasticity, which occurs when a ceramic tile bends under a combination of thermal stress and own weight. In general, the theory of viscoelasticity can be considered extremely large and precise, but its application on real cases is particularly delicate. A time-depending problem, as viscoelasticity naturally is, has to be merged with a temperature-depending situation. This paper investigates how the viscoelastic response of bending ceramic materials can be modelled by commercial Finite Elements codes.

Improving performance and applicability of green composite materials by hybridization

by Ana Pavlovic, Cristiano Fragassa, Milan Sljivic, and Jovica Ilic

The growing concern over environmental issues and the common interest to find a viable alternativ... more The growing concern over environmental issues and the common interest to find a viable alternative to the use of glass or carbon composites reinforced has led to an increased attention about ecologically sustainable polymer composites. These “green” materials are made by natural fibers as reinforce, filled with natural-organic fillers, hence derived from renewable or biodegradable sources. At the same time, this relatively new class of materials faces several limits in comparison to traditional composites especially regarding the proprieties of resistance. This paper investigates the advantages on use a combination of natural fibers for improving the mechanical proprieties of “green” composite materials. At the moment, the common opinion is that green composites are not usable in structural applications, and, as consequence, have to be relegated to unworthy applications (as fillers). On the contrary, there are several evidences that mixing different natural fibers (in a practice usually called as “hybridization”) leads to increase these material proprieties. Even if usually quite limited in term of percentage, from time to time these improvements permit a net enlargement in the fields of applications for green composites. Following a large State of Arts on green composites, including potential benefits and limits of these materials, the paper proposes several examples of hybridization showing its effect on mechanical proprieties.

Simulazione di Impatto Balistico su Barriere Mobili Utilizzate come Sistemi di Protezione nelle Macchine Utensili

by Cristiano Fragassa and Ana Pavlovic

A. Pavlovic, C. Fragassa, M. Mazza, M. Zivkovic, Sep 2014

Questo studio descrive la procedura di simulazione impiegata per analizzare ed ottimizzare il com... more Questo studio descrive la procedura di simulazione impiegata per analizzare ed ottimizzare il comportamento di barriere protettive flessibili, utilizzate nelle macchine utensili, per la protezione dell'ambiente esterno e dei lavoratori dalla proiezione incidentali di utensili oppure parti di essi. In particolare si è analizzato il comportamento dinamico di bandelle flessibili quando colpite da proiettili ad alta velocità. Queste bandelle sono utilizzate comunemente come sistema di protezione offrendo un ottimo compromesso tra fattori quali: efficienza di protezione, semplicità realizzativa, basso costo. Inizialmente si fornirà una breve introduzione sulle motivazioni che hanno portato a studiare questo sistema di protezione. Si descriveranno le varie ipotesi di parametrizzazione del modello di urto per il calcolo. Sarà poi presentata una comparazione dei risultati ottenuti al variare dei principali parametri fisici. Saranno anche brevemente descritti tutti i passi operativi necessari allo svolgimento delle analisi dinamiche mediante il metodo degli elementi finiti: definizione del materiale, realizzazione della mesh, applicazione di carichi e vincoli. I risultati saranno infine comparati con le prove sperimentali.

Use of simulation to optimize a vertical axis wind turbine

by Ana Pavlovic and Cristiano Fragassa

A. Pavlovic, C. Fragassa, Aug 2012

This activity is part of an Italian national research project, named "De Urbis Vento", concerning... more This activity is part of an Italian national research project, named "De Urbis Vento", concerning new solutions for improving performance in a vertical axis wind turbine (VAWT) used in urban contexts. VAWT has the main advantage to operate independently by the wind direction, permitting to obtain a reasonable efficiency even in the urban turbulence flows. The geometrical shape of blades determines the airfoil and how the wind energy is conversed to forces on the blade. Consequently there is a strict interrelation between blade shape and produced energy. According to the geometry of blade, VAW Turbines can be classified in lift driven (Darrieus) and drag driven (Savonius). Since their higher efficiency, more attention is focused on the lift driven turbines. This study aims at comparing several common airfoil shapes by computational fluid dynamic (CFD) obtaining a valid solution for VAWTs to be manufactured, installed (as prototype) and tested in urban context. The simulation program uses 2D airfoil data to calculate the VAWT performance. Several standard NACA profiles have been used as references in comparison. Profiles will be also experimentally measured and optimized to improve the performance.

Ballistic impact simulation for the safety in tool machines

by Ana Pavlovic and Cristiano Fragassa

A. Pavlovic, C. Fragassa , Oct 2012

Numerical control (CNC) boring and routing machines use curtains made from resistant, but flexibl... more Numerical control (CNC) boring and routing machines use curtains made from resistant, but flexible materials to protect end-users from the projection of tool pieces. These curtains allow the work piece to gently pass through, but have to firmly stop every small sharp piece or fragment ejected by fast drilling tools at the highest speed. Nowadays curtains are made in flexible thermoplastic materials: polyamide, polyurethane, polyvinyl chloride or similar materials. Safety issues to be addressed related to the risk of projection of parts during processing are defined by EN 847-1 and EN 847-2 standards, both collecting practical experiences from manufactures and users. However, the effectiveness of these barriers has been compromised by several experts and this state of uncertainty has led to new technical observations, experiments and numerical simulations, but no conclusive results are available at the moment. This independent research, realized by ballistic impact simulation, aims at verifying the effectiveness of protection provided by barriers installed on CNC boring and routing machines. These barriers consist of curtains realized on the basis of the standard UNI EN 848-3. As additional goal, the study optimizes the barrier parameters (e.g. materials, shape, depth, mass, cost,..) in relation to the projectile parameters (shape, mass, speed, direction…) identifying their mutual influence. Additional outcomes lead to the formulation of a practical methodology for design and evaluation of protection efficacy.

Merging Theory and Experiments in a Total Quality Approach for Improving the Reliability of Large-Mass Industrial Products

by Cristiano Fragassa and Ana Pavlovic

C. Fragassa, A. Pavlovic, S. Massimo, May 23, 2014

In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the ... more In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the aim at improving the reliability of large-mass industrial products far beyond the product specifications demanded at the end-customer level. A stricter correlation between standard quality methods and experimental tests has be also realized as a modern integrated tool for design and process validation

Additive Manufacturing of Functional Parts Based on Material Extrusion Technology

Contemporary Materials, 2016

This paper presents the advantages and the process of making of complex functional parts using ad... more This paper presents the advantages and the process of making of complex functional parts using additive manufacturing technology. Design and manufacturing of components were performed at the Laboratory for Technology of Plasticity and Processing Systems at the Faculty of Mechanical Engineering in Banja Luka. The parts were designed using SolidWorks and Catia software packages. Then, CatalystEX and Simplify3D software packages were used to process the CAD model and to prepare it for 3D printing, which included defining of the process parameters, generating layers and support. Functional parts were produced on 3D printers based on the principle of material extrusion. The results of this study show that additive manufacturing technology, specifically technology based on material extrusion, enables very fast production of complex functional parts, with high accuracy and much lower costs and development time compared to conventional technologies.

Analysis of the suspension design evolution in solar cars

FME Transaction, 2017

The contrast between modern mobility alternatives and the seek for sustainability has been an ess... more The contrast between modern mobility alternatives and the seek for sustainability has been an essential concern for industry in the last decades, boosted by technologies that have been progressively narrowing this gap. Among them, solar cars represent a contemporary trend to supply this need. Given the complexity embraced by this technology, the attainment of an efficient design demands the improvement of every aspect of the vehicle, including its mechanics. Performing a critical role on the vehicle's stability, the suspension system of solar cars is thoroughly investigated in this work, in particular the evolution of the structural part directly responsible for undertaking the forces subjected to the wheel hub. Three different shapes made out of carbon fiber reinforced plastic are analysed and compared through static and modal finite element analysis: two front forks meant to be coupled to a wishbone joint, and a wheel hub connected to a novel sliding hub system.

Merging Theory and Experiments in a Total Quality Approach for Improving the Reliability of Large-Mass Industrial Products

In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the ... more In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the aim at improving the reliability of large-mass industrial products far beyond the product specifications demanded at the end-customer level. A stricter correlation between standard quality methods and experimental tests has to be also realized as a modern integrated tool for design and process validation

Improving Performance and Applicability of Green Composite Materials by Hybridization

Contemporary Materials, 2015

A growing concern over environmental issues and the common interest to find a viable alternative ... more A growing concern over environmental issues and the common interest to find a viable alternative to the use of glass or carbon composite reinforcements has led to an increased attention in ecologically sustainable polymer composites. These „green” materials are made by natural fibers, as reinforcement, filled with natural-organic fillers, i.e. derived from renewable or biodegradable sources. At the same time, this relatively new class of materials faces several limits in comparison to traditional composites especially regarding the properties of resistance. This paper investigates the advantages of use of combination of natural fibers for improving mechanical proprieties of „green” composite materials. At the moment, the prevailing opinion is that green composites are not usable in structural applications, and, as a consequence, have to be relegated to unworthy applications (as fillers). On the contrary, there are several evidences that mixing different natural fibers (in practice u...

Osnove Proizvodnih Tehnologija Introduction in Production Technologies Einfuehrung in Die Produktionstechnologie

Numerical modelling the ballistic impacts on flexible curtains used as safety protection in woodworking

by Ana Pavlovic and Cristiano Fragassa

DOI: 10.1177/0954406216646401, Apr 2016

Numerical control boring and routing machines use curtains made from resistant, but flexible mate... more Numerical control boring and routing machines use curtains made from resistant, but flexible materials to protect end-users from the projection of wood chips and tool pieces. These curtains allow the work piece to gently pass through, but firmly stop every small sharp piece or fragment ejected at the highest speed by fast drilling tools. Nowadays curtains are commonly made in flexible thermoplastic materials as polyamide, polyurethane, polyvinyl chloride or similar materials. Safety issues to be addressed related to the risk of projection of parts during processing are defined by EN 847-1 and EN 847-2 standards, both collecting practical experiences from manufactures and users. The effectiveness of these curtains were investigated by technical observations, experiments and even numerical simulations, but conclusive results are not available at the moment. This independent research, where ballistic impacts on flexible curtains were simulated using finite element (FE) methods, aims at verifying the effectiveness of specific protective barriers when realized and used in accordance with the UNI EN 848-3 standard. Numerical simulations permitted to verify the congruity of the main barrier’s characteristics (materials, shape, depth, mass, cost..) in relation to the projectile parameters (shape, mass, speed, direction…) identifying their mutual influence. Outcomes from this research provide useful information toward the definition of a new way for the design of efficient curtains. A comparison between numerical simulations and experimental results coming from ballistic tests was also realized, permitting to validate this predictive methodology.

Compacted and Spheroidal Graphite Irons: Experimental Evaluation of Poisson's Ratio

by Cristiano Fragassa and Ana Pavlovic

Vol. 44, No. 4: 327-332, Jun 2016

Spheroidal Graphite cast Iron (SGI), also known as ductile iron, represents a perfect material fo... more Spheroidal Graphite cast Iron (SGI), also known as ductile iron, represents a perfect material for a very large range of modern applications. It is successfully used wherever optimal strength, stiffness and even low costs are required: high values of tensile strength and Young's modulus are between its most appreciable propеrties. At the same time, nowadays, a different cast iron, known as Compacted Graphite Iron (CGI) or vermicular graphite iron, is taking the first steps in replacing SGI respect to some specific applications. It depends on a better castability, machinability and thermal resistance. CGI is an ideal cast iron in the case of components under simultaneous mechanical and thermal loadings, such as cylinder blocks and heads. Unfortunately, while SGI benefits of a wide scientific literature, CGI is a relatively unknown material. Moreover, dut to its particular microstructure, the production of CGI presents additional difficulties and it is not easy to obtain stable properties in the CGI alloy. This paper illustrates a way for the experimental evaluation of the Poisson's ratio by tensile specimens, comparing this propriety in the case of SGI and CGI.

Combining Additive Manufacturing and Vacuum Casting for an Efficient Manufacturing of Safety Glasses

by Cristiano Fragassa and Ana Pavlovic

Vol. 44, No. 4: 393-397, Jul 2016

This paper presents the possibility of integration of modern techniques of additive manufacturing... more This paper presents the possibility of integration of modern techniques of additive manufacturing and vacuum casting in the rapid manufacturing of complex parts. The prototype of safety glasses was directly developed from a CAD model, which is used as a main model for making moulds in a vacuum casting process. The development stages, which include additive production of glasses and the process of vacuum casting with the definition of material components, preheating temperature, the forming of silicone mould, the casting process, hardening and other parameters are presented in this paper. It is proved that by using this technique it is possible to produce complex functional parts quickly, with high precision, accuracy and surface quality, while significantly reducing costs of development and production compared to other similar technologies.

$Research paper thumbnail of Tribological aspects of cast iron investigated via fracture toughness$

Tribological aspects of cast iron investigated via fracture toughness

by Cristiano Fragassa and Ana Pavlovic

Vol. 38, No. 1: pp 1-10, Jan 2016

Linear-elastic plane-strain fracture toughness of metallic materials is a method which covers the... more Linear-elastic plane-strain fracture toughness of metallic materials is a method which covers the determination of the strain fracture toughness (KIC) of metallic materials by increasing-force test of fatigue precracked specimens. This method has been applied for investigating the fracture behaviour of cast iron. Two groups of cast alloys, Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) have been investigated. While SGI benefits of a wide scientific literature, CGI is a relatively unknown material despite of its large potentialities in industrial applications.

Comparison of mechanical properties in compacted and spheroidal graphite irons

by Cristiano Fragassa and Ana Pavlovic

Vol. 38, No. 1: pp 49-59, Jan 2016

Mechanical properties of cast irons are governed by the size, distribution and shape of the incor... more Mechanical properties of cast irons are governed by the size, distribution and shape of the incorporated graphite particles. In a set of experiments, two groups of cast alloys, Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were investigated. Even if the processes used for their production could be apparently considered quite similar, these two materials are characterized by a net difference in graphite particles and, as consequence, in final properties. Adding, while SGI benefits of a wide scientific literature supporting its large use, CGI is a relatively unexplored.

Improvements in wood thermoplastic composite materials properties by physical and chemical treatments.

by Cristiano Fragassa and Ana Pavlovic

Vol. 10, No. 1: pp 205-218, Feb 2016

This paper presents a short overview of the developments made in the field of wood thermoplastic ... more This paper presents a short overview of the developments made in the field of wood thermoplastic composites in terms of surface treatment, flammability, matrix/reinforcement model, properties and application of recycled polymer matrices. The usage of lignocellulosic fibers as reinforcement in composite materials demands well formed interface between the fiber and the matrix. Because of the different nature of reinforcement and matrix components some physical and chemical treatment methods which improve the fiber matrix adhesion were introduced, as well as the improvements of lignocellulosic fibers and thermoplastic polymer matrix based composites flammability characteristics. These physical and chemical treatments influence the hydrophilic character of the lignocellulosic fibers, and therefore change their physical and mechanical properties.

Analysis of flexible barriers used as safety protection in woodworking

by Cristiano Fragassa and Ana Pavlovic

Vol. 10, No. 1: pp 71-88

Machine tools use physical barriers, made by flexible thermoplastic materials, to protect the env... more Machine tools use physical barriers, made by flexible thermoplastic materials, to protect the environment and the operators against the projections of wood chips and parts of cutting tools. These barriers constitute a partial closure and allow the passage of the workpiece, being simultaneously able to contain sharp fragments projected at high speed. The present research was conducted with the aim to evaluate the real effectiveness of these barriers, to investigate their dynamic behaviour by numerical simulations. Results showed that these barriers, if properly considered, could retain heavier masses and higher speeds. The research also allowed, in fact, to investigate the influence of several factors in design, selection and use, as material, shape, position, assemblages and many others, highlighting weaknesses and identifying possible measures to increase its effectiveness.

General considerations on regulations and safety requirements for quadricycles

by Ana Pavlovic and Cristiano Fragassa

Vol. 9 - N. 4: pp. 657–674, Oct 2015

In recent years, a new class of compact vehicles has been emerging and wide-spreading all around ... more In recent years, a new class of compact vehicles has been emerging and wide-spreading all around Europe: the quadricycle. These four-wheeled motor vehicles, originally derived from motorcycles, are a small and fuel-efficient mean of transportation used in rural or urban areas as an alternative to motorbikes or city cars. In some countries, they are also endorsed by local authorities and institutions which support small and environmentally-friendly vehicles. In this paper, several general considerations on quadricycles will be provided including the vehicle classification, evolution of regulations (as homologation, driver licence, emissions, etc), technical characteristics, safety requirements, most relevant investigations, and other additional useful information (e.g. references, links). It represents an important and actual topic of investigation for designers and manufacturers considering that the new EU regulation on the approval and market surveillance of quadricycles will soon enter in force providing conclusive requirements for functional safety environmental protection of these promising vehicles.

Experimental analysis of mechanical properties of composites reinforced by flax and basalt fibres

by Cristiano Fragassa and Ana Pavlovic

Vol. 39: pp. 68-73

Modelling the Viscoelasticity of Ceramic Tiles by Finite Element

by Ana Pavlovic and Cristiano Fragassa

1736, 020174 (2016); doi: 10.1063/1.4949749, Jun 2016

This research details a numerical method aiming at investigating the viscoelastic behaviour of a ... more This research details a numerical method aiming at investigating the viscoelastic behaviour of a specific family of ceramic material, the Grès Porcelain, during an uncommon transformation, known as pyroplasticity, which occurs when a ceramic tile bends under a combination of thermal stress and own weight. In general, the theory of viscoelasticity can be considered extremely large and precise, but its application on real cases is particularly delicate. A time-depending problem, as viscoelasticity naturally is, has to be merged with a temperature-depending situation. This paper investigates how the viscoelastic response of bending ceramic materials can be modelled by commercial Finite Elements codes.

Improving performance and applicability of green composite materials by hybridization

by Ana Pavlovic, Cristiano Fragassa, Milan Sljivic, and Jovica Ilic

The growing concern over environmental issues and the common interest to find a viable alternativ... more The growing concern over environmental issues and the common interest to find a viable alternative to the use of glass or carbon composites reinforced has led to an increased attention about ecologically sustainable polymer composites. These “green” materials are made by natural fibers as reinforce, filled with natural-organic fillers, hence derived from renewable or biodegradable sources. At the same time, this relatively new class of materials faces several limits in comparison to traditional composites especially regarding the proprieties of resistance. This paper investigates the advantages on use a combination of natural fibers for improving the mechanical proprieties of “green” composite materials. At the moment, the common opinion is that green composites are not usable in structural applications, and, as consequence, have to be relegated to unworthy applications (as fillers). On the contrary, there are several evidences that mixing different natural fibers (in a practice usually called as “hybridization”) leads to increase these material proprieties. Even if usually quite limited in term of percentage, from time to time these improvements permit a net enlargement in the fields of applications for green composites. Following a large State of Arts on green composites, including potential benefits and limits of these materials, the paper proposes several examples of hybridization showing its effect on mechanical proprieties.

Simulazione di Impatto Balistico su Barriere Mobili Utilizzate come Sistemi di Protezione nelle Macchine Utensili

by Cristiano Fragassa and Ana Pavlovic

A. Pavlovic, C. Fragassa, M. Mazza, M. Zivkovic, Sep 2014

Questo studio descrive la procedura di simulazione impiegata per analizzare ed ottimizzare il com... more Questo studio descrive la procedura di simulazione impiegata per analizzare ed ottimizzare il comportamento di barriere protettive flessibili, utilizzate nelle macchine utensili, per la protezione dell'ambiente esterno e dei lavoratori dalla proiezione incidentali di utensili oppure parti di essi. In particolare si è analizzato il comportamento dinamico di bandelle flessibili quando colpite da proiettili ad alta velocità. Queste bandelle sono utilizzate comunemente come sistema di protezione offrendo un ottimo compromesso tra fattori quali: efficienza di protezione, semplicità realizzativa, basso costo. Inizialmente si fornirà una breve introduzione sulle motivazioni che hanno portato a studiare questo sistema di protezione. Si descriveranno le varie ipotesi di parametrizzazione del modello di urto per il calcolo. Sarà poi presentata una comparazione dei risultati ottenuti al variare dei principali parametri fisici. Saranno anche brevemente descritti tutti i passi operativi necessari allo svolgimento delle analisi dinamiche mediante il metodo degli elementi finiti: definizione del materiale, realizzazione della mesh, applicazione di carichi e vincoli. I risultati saranno infine comparati con le prove sperimentali.

Use of simulation to optimize a vertical axis wind turbine

by Ana Pavlovic and Cristiano Fragassa

A. Pavlovic, C. Fragassa, Aug 2012

This activity is part of an Italian national research project, named "De Urbis Vento", concerning... more This activity is part of an Italian national research project, named "De Urbis Vento", concerning new solutions for improving performance in a vertical axis wind turbine (VAWT) used in urban contexts. VAWT has the main advantage to operate independently by the wind direction, permitting to obtain a reasonable efficiency even in the urban turbulence flows. The geometrical shape of blades determines the airfoil and how the wind energy is conversed to forces on the blade. Consequently there is a strict interrelation between blade shape and produced energy. According to the geometry of blade, VAW Turbines can be classified in lift driven (Darrieus) and drag driven (Savonius). Since their higher efficiency, more attention is focused on the lift driven turbines. This study aims at comparing several common airfoil shapes by computational fluid dynamic (CFD) obtaining a valid solution for VAWTs to be manufactured, installed (as prototype) and tested in urban context. The simulation program uses 2D airfoil data to calculate the VAWT performance. Several standard NACA profiles have been used as references in comparison. Profiles will be also experimentally measured and optimized to improve the performance.

Ballistic impact simulation for the safety in tool machines

by Ana Pavlovic and Cristiano Fragassa

A. Pavlovic, C. Fragassa , Oct 2012

Numerical control (CNC) boring and routing machines use curtains made from resistant, but flexibl... more Numerical control (CNC) boring and routing machines use curtains made from resistant, but flexible materials to protect end-users from the projection of tool pieces. These curtains allow the work piece to gently pass through, but have to firmly stop every small sharp piece or fragment ejected by fast drilling tools at the highest speed. Nowadays curtains are made in flexible thermoplastic materials: polyamide, polyurethane, polyvinyl chloride or similar materials. Safety issues to be addressed related to the risk of projection of parts during processing are defined by EN 847-1 and EN 847-2 standards, both collecting practical experiences from manufactures and users. However, the effectiveness of these barriers has been compromised by several experts and this state of uncertainty has led to new technical observations, experiments and numerical simulations, but no conclusive results are available at the moment. This independent research, realized by ballistic impact simulation, aims at verifying the effectiveness of protection provided by barriers installed on CNC boring and routing machines. These barriers consist of curtains realized on the basis of the standard UNI EN 848-3. As additional goal, the study optimizes the barrier parameters (e.g. materials, shape, depth, mass, cost,..) in relation to the projectile parameters (shape, mass, speed, direction…) identifying their mutual influence. Additional outcomes lead to the formulation of a practical methodology for design and evaluation of protection efficacy.

Merging Theory and Experiments in a Total Quality Approach for Improving the Reliability of Large-Mass Industrial Products

by Cristiano Fragassa and Ana Pavlovic

C. Fragassa, A. Pavlovic, S. Massimo, May 23, 2014

In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the ... more In this paper the Total Quality Management (TQM) approach is proposed, refined and used with the aim at improving the reliability of large-mass industrial products far beyond the product specifications demanded at the end-customer level. A stricter correlation between standard quality methods and experimental tests has be also realized as a modern integrated tool for design and process validation

Introduction in production technologies

by Cristiano Fragassa, Ana Pavlovic, and Milan Sljivic

Proceedings of the 1st International Symposium on Multidisciplinary Studies of Design in Mechanical Engineering

by Cristiano Fragassa and Ana Pavlovic

After the success of the EU TEMPUS Project: “Multidisciplinary Studies of Design in Mechanical En... more After the success of the EU TEMPUS Project: “Multidisciplinary Studies of Design in Mechanical Engineering”, the 1st edition of the MS.DESIGN Symposium was organized as a valid occasion for a deep comparison between different models and approaches to Design and Engineering. The purpose of this Symposium is the same that funded the ending Project: to provide “a Common Area for Industrial Designers”, a social and scientific environment to researchers, engineers, artists and students in the field of Industrial Design to present and discuss the current state of their work and to evaluate the impact of the discipline on the scientific development and modern organisation of the industrial world. Personal knowledge and common life experiences are a great added value for the young and less young generations in order to strength the spirit of incoming epochal enlargement of new Nations in the European Union.

Basics of Manufacturing Technologies

L’innovazione tecnologica nel settore legno: Linee guida per il trasferimento tecnologico e stati dell’arte

This Guidelines, also published with the original English name of “How to ‘Bridge the Gap’ betwee... more This Guidelines, also published with the original English name of “How to ‘Bridge the Gap’ between
University and Business”, has been developed inside the project “ADRIA-HUB- Bridge technical differences
and social suspicions contributing to transform the Adriatic area in a stable hub for a sustainable
technological development” and financed by the EU IPA-ADRIATIC Cross Border Cooperation Programme
2007-2013.

5 mm... di totale sicurezza

by Ana Pavlovic and Cristiano Fragassa

Utilizzare i materiali costruttivi vicino ai propri limiti di resistenza meccanica consente prest... more Utilizzare i materiali costruttivi vicino ai propri limiti di resistenza meccanica consente prestazioni elevate e competitive, ma è anche un rischio da accettare solo potendo prevedere la risposta dei materiali in condizioni inusuali... soprattutto evitando una riduzione dello spessore progettazione Utilizzare i materiali costruttivi vicino ai propri limiti di resistenza meccanica è una scelta progettuale che consente di raggiungere prestazione elevate e competitive, ma è anche un rischio da accettare solo qualora si disponga di un knowhow adeguato a prevedere la risposta dei materiali anche in condizioni inusuali. Si pensi, ad esempio, a come la progres-siva riduzione dello spessore delle lamiere possa condurre ad effetti imprevisti di instabilità e al rapido collasso della struttura. Una eventualità che non può neppure essere immaginata quando si ha l'obiettivo di realizzare una piattaforma aerea come quelli che i vigili del fuoco in tutto il mondo manovrano con sicurezza in ogni condizione di emergenza e pericolo.

Una molla nel motore

by Ana Pavlovic and Cristiano Fragassa

DAL PROTOTIPO AL PEZZO IN 48 ORE... NPASSANDO DALLO STAMPO

N Stampi • febbraio 2014 38 Materiali compositi/fi bra di carbonio DAL PROTOTIPO AL PEZZO IN 48 O... more N Stampi • febbraio 2014 38 Materiali compositi/fi bra di carbonio DAL PROTOTIPO AL PEZZO IN 48 ORE… PASSANDO DALLO STAMPO La realizzazione di un particolare in materiale composito (fi bra di carbonio, kevlar, vetro ecc..) è una procedura complessa che attraversa diverse fasi. In questo articolo, si descrive nel dettaglio come passare dal prototipo al pezzo fi nito in fi bra di carbonio in meno di 48 ore

Il Programma Nazionale della Ricerca in aiuto alle imprese

giugno 2011 46 finanziamenti Il programma, presentato dal MIUR (Ministero dell'Istruzione, dell'U... more giugno 2011 46 finanziamenti Il programma, presentato dal MIUR (Ministero dell'Istruzione, dell'Università e della Ricerca) e disponibile in tutte le sue 173 pagine sul sito uffi ciale http://www.miur.it/ Documenti/ricerca/pnr_2011_2013/ PNR_2011-2013_23_MAR_2011_ web.pdf, agisce come componente strutturale di politica economica, puntando sulla progressiva integrazione tra offerta e domanda di ricerca, sulla costruzione di una rete di piattaforme e infrastrutture tecnologiche aperte al contributo e partecipazione del sistema produttivo, sull'incremento di redditività degli investimenti in ricerca.

Il ruolo cruciale delle aziende per lo sviluppo dell’Europa

l'Unione Europea conta 27 stati membri, è il primo Paese al mondo per PIL (stimato in 10.335 mili... more

Investimenti italiani IN SERBIA

Dall’Europa un forte incentivo alla ricerca per le PMI

Research for SMEs" è un Programma Europeo di ricerca che incentiva la partecipazione delle Piccol... more Research for SMEs" è un Programma Europeo di ricerca che incentiva la partecipazione delle Piccole e Medie Imprese (PMI) con alte capacità innovative ma con limitate strutture di ricerca e/o laboratori, attraverso misure che permettano di esternalizzare (outsourcing) lo svolgimento delle attività di ricerca e di sviluppo. Le misure previste mirano inoltre ad incoraggiare l'acquisizione delle competenze (know how) Dall'Europa un forte incentivo alla ricerca per le PMI Ana Pavlovic L'Unione Europea offre alle PMI un'ampia rosa di opportunità. Eppure, sono numerosi i fattori che potrebbero scoraggiare dal prenderle in considerazione. In esclusiva per "Lamiera", una piccola guida alle diverse opportunità necessarie per migliorare la propria competitività a livello internazionale. Il programma di finanziamento supporta piccoli gruppi di PMI dal forte contenuto di innovazione durante una attività biennale di ricerca e sviluppo che mira a risolvere i problemi tecnologici delle aziende e permettere loro di acquisire un know-how tecnologico esclusivo. I progetti devono partire dalle esigenze di innovazione e di competitività delle aziende e devono concretizzarsi attraverso contratti di consulenza con università e centri di ricerca. Questo passaggio è ritenuto fondamentale per garantire che le aziende acquisiscano quelle conoscenze tecnologiche necessarie a rafforzare le proprie posizioni sul mercato. I progetti devono mettere in chiara evidenza le ricadute potenziali e i benefici economici che le imprese godranno dal loro coinvolgimento. In questa linea di finanziamento, le imprese sono infatti viste come le beneficiarie uniche e dirette dei risultati, ma devono essere loro le prime ad investire acquistando tecnologia. Dovranno farlo muovendosi attraverso le attività di consulenza dei centri di ricerca e ricevendo indietro quel know-how che le metterà in grado di sviluppare nuovi prodotti, sistemi, processi o servizi oppure di migliorare significativamente quelli esistenti. In tal caso, l'Unione finanzia completamente i costi di consulenza e una piccola parte degli altri costi.

IL PONTE FRA UNIVERSITÀ' E LA IMPRESA

Fonderia, Nov 2013

L e università e l'intero sistema di formazione superiore rappresentano risorse fondamentali per ... more L e università e l'intero sistema di formazione superiore rappresentano risorse fondamentali per le società industriali avanzate a garanzia dello sviluppo della ricerca scientifica e del trasferimento di tali conoscenze verso le imprese. Per questo motivo le università e gli enti di ricerca pubblici, considerati nel loro triplice ruolo di fornitori dei massimi livelli d'istruzione, di ricerca avanzata e di innovazione di avanguardia, sono al vertice del triangolo della conoscenza in Europa in relazione al ruolo cruciale che svolgono in vista di una efficace transizione verso un'economia e verso una società basate sulla conoscenza.

LINEE GUIDA PER LA GESTIONE DEGLI ODORI

Fonderia, Sep 2013

inquinamento odorigeno, cioè l'immissione in atmosfera di sostanze inquinanti in generale non dir... more inquinamento odorigeno, cioè l'immissione in atmosfera di sostanze inquinanti in generale non direttamente nocive alla salute ma caratterizzate da odore intenso o sgradevole (emissioni da discariche, allevamenti, industrie) rappresenta una causa importante di disagio ambientale in quanto responsabile di un abbassamento spesso signifi cativo della godibilità dell'ambiente (sia a livello abitativo sia lavorativo) e di insorgenza di malessere psicofi sico con conseguente peggio-ramento della qualità della vita. L'odore è causato dalle molecole odoranti dissolte in aria ed è quindi un senso chimico in quanto utilizza, come informatori, le specifi che sostanze chimiche. La vasta gamma degli odori deriva dai vari tipi di residui organici emanati, che entrano in contatto e vengono recepite dal naso. In generale, i residui inorganici non hanno odori, ma esistono alcune sostanze inorganiche, quali il solfuro d'idrogeno e l'ammoniaca, che producono invece odori caratteristici. La percezione di un odore avviene essenzialmente in due modi, uno strettamente fi siologico; l'altro psicologico. Il processo

Verso una nuova economia della conoscenza

Fonderia, Jun 2014

Si tratta di un corso post-laurea triennale a cui si accede per concorso, tradizionalmente fi nal... more Si tratta di un corso post-laurea triennale a cui si accede per concorso, tradizionalmente fi nalizzato a fornire a giovani laureati (ovvero i dottorandi) le necessarie competenze per esercitare attività di ricerca di alto livello presso università ed enti di ricerca pubblici. Il dottorato può contribuire alla creazione di fi gure professionali altamente qualifi cate da inserire nelle imprese per aumentare la capacità di ricerca delle stesse e rispondere alle esigenze di innovazione tecnologica. L'ammissione ai corsi di dottorato avviene mediante valutazione comparativa pubblica dei candidati. La selezione dei can-didati si basa di solito sulla valutazione dei titoli e/o su un progetto di ricerca, su una prova scritta, un colloquio o su una combinazione tra tali modalità. I dottorandi devono essere in possesso di una laurea del vecchio ordinamento oppure di una laurea specialistica, di laurea magistrale, o di analogo titolo accademico conseguito all'estero. Non ci sono limiti di età e di cittadinanza. Il dottorando è in grado di risolvere specifi ci problemi che richiedono un'attività di ricerca (come per esempio lo sviluppo di un nuovo prodotto, l'evoluzione di un prodotto esistente, l'ottimizzazione di un processo produttivo, e altro ancora). L'impresa

MEASURING TEMPERATURE AND VELOCITY WITH TEMPERATURE ANEMOMETRY

There are a lot of that have been developed to measurement temperature and velocity of fluid. Mos... more There are a lot of that have been developed to measurement temperature and velocity of fluid. Most of them are using for measuring velocity in flows that are not turbulent. Only a few can be used for measuring turbulence itself. This paper describe us the basic principles of measurement in fluid mechanics and will focus on TA (Thermal Anemometry). They measure the fluid velocity by sensing the changes in the heat transfer from a small, electrical heated sensor exposed to the fluid motion. This technique is suitable if the flow is isothermal and does not show strong pressure gradients. Measurement of the velocity may have been difficult because of changing the other parameters. If we want to measure more than just a velocity we will take more than one sensor. Experimental points will give the closely results with theory points.

STRESS AND DEFORMATION DISTRIBUTION IN THE PLANAR ISOTROPIC FIELD REDUCED WITH HOLES

This paper describes the stress and deformation distribution in planar isotropic field. Especiall... more This paper describes the stress and deformation distribution in planar isotropic field. Especially, panel was being studied with rectangular and ellipse holes. Panels are stretched in the Ox-direction with force F. Purpose of this paper is to follow effect of the profile of holes on the stress and deformation distribution. According to the [1], [2]...all methods can be divided on analytical and numerical methods. Analitical methods are based on Theory of Elasticity and Strenght of Materials. Numerical methods are approximately methods, but they are very practical becouse they enble to finde the solution in very shorte time. Especcialy important method is Method of Final Elements, who allude on dicretization in fisical model. Final result can be obtain with solution of algebraic sistem equations.

FEM SIMULATION FOR COMPREHENSION OF EXPERIMENTA

Electro-mechanic devices for the automatic changing of gear were tested by company using the same... more Electro-mechanic devices for the automatic changing of gear were tested by company using the same accelerated life testing procedures in different stages of the product development. All the tested prototypes satisfied the experimental conditions for accelerated life tests, while 50% of components coming from the first sample of serial production showed crack phenomena during the same testing procedure. This situation can be related to a large number of undefined factors: from the variability of material proprieties or in production process parameters to accidentally different conditions in testing. The complete list of all the possibilities of variance was to complex to be defined, recognized and verified by new sets of experimental tests. FEM calculation permitted a fast simulation of the component response under the complex experimental testing conditions, modifying the interpretation of some experimental results and correctly driving the designer toward quick improvements of product.

STRENGTH ANALYSIS OF SAFETY CAGE

by Ana Pavlovic and Snezana Vulovic

Safety cage represent one of the most important part of equipment in sport cars. It has to be mad... more Safety cage represent one of the most important part of equipment in sport cars. It has to be made in the way to absorb kinetic energy and on that way reduce contusion of driver. Initiation world standards of safety cage, in car production, in one of our companies were the main motivation for this work. During the race, cars with safety cage (common name: roll bar) have to be completely safety, especially in the case of turning over or crash. In this case we didn’t have acceleration life test and any improve that structures is going to resist impact. Structures had to be modeled in CATIA software like a shell. Geometrical and material non linear analysis was done using software PAK [1]. Using displacement control method we got critical forces for structure. Those results gave necessary safety factor and strength, and acceptable results were obtained using material with better properties. Procedure that was used in this work reduced the number of experimental testing and their costs.

GEOMETRY OPTIMIZATION OF THE AUTOMATIC CHANGING GEAR; SELE-SPEED BY FEM SIMULATION

Sele-speed is the commercial named used for a widespread electro-mechanic devices for the automat... more Sele-speed is the commercial named used for a widespread electro-mechanic devices for the automatic changing of gear, realized by Magneti Marelli Powertrain (FIAT Group) and fitted up the high-class motorcars of different companies. It was tested by company using the same accelerated life testing procedures in different stage of the product development.

MEHANIZAM ZA SAMOPODEŠAVANJE RUČNE KOČNICE

Zbog habanja kočnih obloga zadnje kočnice, kao i zbog istezanja čeličnog užeta komande ručne kočn... more Zbog habanja kočnih obloga zadnje kočnice, kao i zbog istezanja čeličnog užeta komande ručne kočnice u toku eksploatacije vozila, u prenosnom mehanizmu ručne kočnice dolazi do povećanja predefinisanih zazora, odnosno do povećanja praznog hoda ručice komande. Ovaj prazan hod može da se poveća do te mere da ugrozi normalno funkcionisanje sistema za kočenje. Iz tog razloga, svi sistemi ručne kočnice sadrže mehanizme za podešavanje zazora. Na većini vozila ovo podešavanje se obavlja ručno, što podrazumeva povremeno povlačenje vozila iz eksploatacije zbog servisiranja. Iz tog razloga, počelo se sa primenom različitih mehanizama za samopodešavanje ručne kočnice, u toku same eksploatacije vozila.
U ovom radu prikazana je jedna konstrukcija mehanizma za kontinualno samopodešavanje ručne kočnice, bez povlačenja vozila iz eksploatacije.

QUALITY FUNCTION DEPLOYMENT IN THE AESTHETIC DESIGN OF A NEW TRENDY HANDPIECE FOR BEAUTY-FARM

Quality Function Deployment (QFD) is a powerful development methodology with a wide range of appl... more Quality Function Deployment (QFD) is a powerful development methodology with a wide range of applications. This paper presents a basic application of QFD for the esthetical design of a new, high-fashion, handpiece, a fundamental tool for beauty care. This methodology is not proposed, here, showing revolution concepts, but as a
practical method able to orient the development of new product lines and to quickly compare
different design choices. By QFD a modern design process is introduced in the Factory, able to
support designers toward the optimal solution for every given environment and conditions.

COMPARATIVE ANALYSIS OF THROTTLE BODY SPRINGS IN FATIGUE CONDITIONS

This paper describes a theoretical and experimental approach used for the complete fatigue streng... more This paper describes a theoretical and experimental approach used for the complete fatigue strength validation and
testing of double torsion springs for a throttle body. By theorized design formulas, FEM simulations and experimental
confirmations on a large number of torsion springs, an all-around review was performed giving addition and helpful
information for a conscious use of this critical part.

Gear Wear Accelerated testing Device with Reverse motion - Design and Application -

Gear wear testing is an extensive laboratory process in conditions similar to service ones. To ap... more Gear wear testing is an extensive laboratory process in conditions similar to service ones. To apply the obtained results for the design of the new gearing structures, it is necessary to identify an additional indicator: the wear probability. In this case reverse gear motion is an additional condition which is necessary to simulate along the laboratory testing. Design, including 3D model of testing device structure for the purpose of plastic gear wear testing, is presented and analyzed. The application for wear probability testing of gears with reverse motion, together with experimental data processing, is presented. The application of those results in design process of the new gear structures is discussed. Gear system for air flow and combustion control in the car engines is used as an example for testing and design. Plastic gears transform control motion and load by resistance torque of the spring for reverse motion. Service life and reliability of this system, including its design using reliability as design constraint, needs experimental data obtained by designed testing device.

Investigations of application of composite materials in packing machines

The paper presents analysis of mechanical behaviour of components of packing machines in which st... more The paper presents analysis of mechanical behaviour of components of packing machines in which steel parts are replaced by parts made of metal matrix composite materials (MMCM). In this purpose, linear analytical and numerical analyses were applied for calculation of stiffness of the parts, and nonlinear numerical analysis of functional behaviour of the components was performed. Besides, flexible dynamic analysis was applied for consideration of impact behaviour. The results show that, while masses of the parts are reduced around 25%, desired adhesive properties and impact resistance are achieved.

TORSIONAL STIFFNESS OF MULTIPLE-UNITS RAILWAY VEHICLE WITH LINEAR AND SYMMETRIC ACTION OF SUSPENSION SYSTEM

by Ana Pavlovic and Nebojša Bogojević

This paper presents analytical expression for torsional stiffness of railway vehicles which consi... more

DESIGN AND OPTIMIZATION OF MECHANICAL SOLUTIONS FOR HIGH SPEED COMPONENTS IN PACKAGING MACHINES

The paper presents the results of a study on optimization of mechanical solutions focused on a ve... more

EXPERIMENTAL TESTING METHODS AS FUNDAMENTAL APPROACH FOR IMPROVING THE RELIABILITY OF LARGE-MASS INDUSTRIAL PRODUCTS

Experimental tests are a fundamental practice for improving the reliability and the functionality... more Experimental tests are a fundamental practice for improving the reliability and the functionality of mass- oriented products. But, since the high level of quality of modern commercial components (e. g., less than 5PPM of failures in the automotive field), accelerated life tests have to be properly integrated by advanced tools for reliability deployment based on failure models and statistical evaluations. On one side, Design of Experiments (DOE) can be used for planning the accelerated experiments; Analysis of Variance (ANOVA) for reducing the variability of measurements; failure models for interpreting the physic of phenomena of damage. On the other side, Failure Reporting, Analysis, Corrective Action System (FRACAS) and Failure Mode and Effect Analysis (FMEA) are irreplaceable to highlight on which criticalities to focus the experimental research, Fault Tree Analysis (FTA) and Reliability Analysis of in-service failure Data (RDA) to foresee the theoretical and authentic behavior of reliability. Only strictly joining the Design for Experiments techniques (DOE, ANOVA, etc.) to the Design for Quality methodologies (FRACAS, FTA, FMEA, RDA) is possible to manage an integrated approach of Total Quality (TQ) and the reliability move besides the current limits.

FATIGUE STRENGTH VALIDATION FOR A DOUBLE TORSION SPRING

by Cristiano Fragassa and Ana Pavlovic

This work relates the reliability testing and improvements for a critical double torsion spring i... more This work relates the reliability testing and improvements for a critical double torsion spring installed inside an automotive throttle body. The double torsion action realized by the spring can be functionally divided in two loading phases, under and over a defined position, called limp-home (LH), and the fast, complete returning stroke to the initial, preloaded zero-position. Different components failed during the experimental validation tests under a combination of fast opening-closing movements, temperature cycles and vibration stresses. This paper describes some specific technical solutions used to design and realized an experimental equipment able to perform, at the same time, fatigue tests on a large number of torsion springs. Statistical tools are used to evaluate the fatigue strength.

Characterization of impact behavior of composite car components

Impact resistance of composite components is usually investigated through series of experimental ... more Impact resistance of composite components is usually investigated through series of experimental probes in which the component is hit by impactor, and the impact resistance is described by forces that cause creation of fractures and perforation in the investigated structure. However, these forces depend on characteristics of impactor and the impact, and therefore, do not inherently represent characteristics of the investigated structure. This paper presents analysis of results obtained by experimental studies of impact tests of air-intake manifold made from composite material PA6.6 with 35% of glass fibers. The analysis consists of calculation of various kinematic and dynamic quantities during the experimental impact, with the ultimate aim to investigate alternative possibilities for description of impact resistance of composite structures.

Design and Application of Gear Wear Accelerated Testing Device with Reverse Motion

Gear wear testing is an extensive laboratory process in which gears are moved by special equipmen... more Gear wear testing is an extensive laboratory process in which gears are moved by special equipment in conditions similar to exploitation ones. For application of information obtained by the tests in practice, for example for the design of new gearing structures, it is necessary to determine the failure probability of gear teeth wear. In that purpose, it is necessary to simulate reverse gear motion, which is an additional condition imposed on the design of testing equipment. From the point of view of statistics, minimum set for the estimation of the failure probability consists of eight assemblies. For that reason, the device should enable simultaneous testing of at least eight assemblies of gears.

DYNAMIC ANALYSIS OF POLYCROWNED GEAR

New technology and development of new software have been enabled a big step in research of mechan... more New technology and development of new software have been enabled a big step in research of mechanical systems and their components. Porous of this paper is to show us dynamical analysis of polycrowned gear. Dynamical forces have much more affect than static on efficient work of a system and therefore, this paper is dedicated to that analysis. The exploitation show that the level of noise and vibration also depend on this kind of load. The efficiency and precision of one mechanical part depends on well checked dynamic analysis. For this analysis have been used various software for modeling (Autodesk-Mechanical Desktop, Autodesk Inventor Professional 9) and construction analysis (COSMOS/M, ANSYS).

QUALITY CONTROL OF CONTOUR VERIFIER USING PHOTOGRAMMETRIC MEASURING SYSTEMS

Photogrammetric measuring systems provide precision compatible or better than the accuracy achiev... more Photogrammetric measuring systems provide precision compatible or better than the accuracy achieved by the coordinate measurement systems for high-precision measurement of large volumes. Quality control by contour verifier is carried out using method of light gap. Therefore, it is important that the contours of the equipment have made precise geometric entities. Objects’ size of control devices is varying from a few tens of millimeters to a few meters. Sometimes it is necessary to perform on site measurements which give photogrammetric measuring systems a great advantage compared to conventional systems.

BUCKLING ANALYSIS OF A TELESCOPIC ARM: NUMERICAL SIMULATION AND EXPERIMENTAL TESTING

n mechanical structures, materials are pushed closer to their critical limits due to the continuo... more n mechanical structures, materials are pushed closer to their critical limits due to the continuous improvement of the requested performances, so structural resistance and sensitivity to instability phenomena increase their importance. In this paper, numerical and experimental analyses of a telescopic arm were performed to investigate the elasto-plastic behavior and the local buckling effects on the structure. A complete FEM analysis has been realized By ANSYS WB ver.11, considering different load and boundary configurations according to the real use conditions. Simulations were driven by analytical theories and results were compared with experimental testing with a good coincidence. The whole structure remained within the elastic limit, except localized zones. Linear buckling techniques showed that the critical loads and the corresponding bucking modes were higher than the extreme working conditions.
FEM simulation permitted to reduce the experimental testing time and costs offering a fast methodology for further improvements.

GREEN COMPOSITES: A REVIEW OF STATE OF ART

The rising concern towards environmental issues and the need to find a realistic alternative to g... more The rising concern towards environmental issues and the need to find a realistic alternative to glass reinforced composites has led to increase interest about polymer composites filled with natural-organic fillers, that comes from renewable and biodegradable sources. The aim of the project is to raise people awareness regarding the scientific and technological knowledge of green composite materials in order to support a larger application in whole industry sectors. This short review briefly illustrates the main paths and results of research (both academic and industrial) on this topical subject, providing a quick overview.