A. Di Ilio - Academia.edu (original) (raw)

Papers by A. Di Ilio

International Journal of Machine Tools and Manufacture, 2000

The subject of this paper is concerned with an experimental study on the grindability of metal ma... more The subject of this paper is concerned with an experimental study on the grindability of metal matrix composites. Machining by abrasive tools of these materials has been investigated by means of experimental tests carried out with different types of grinding wheels, made with both conventional abrasives and superabrasives. It has been found that the decrease in cutting ability of the

Journal of Manufacturing Processes, 2020

A hybrid non-linear numerical model of the thermal field produced during Friction Assisted Joinin... more A hybrid non-linear numerical model of the thermal field produced during Friction Assisted Joining process of Metal-polymers hybrid joints is developed. The model uses experimental processing loads (plunging load and torque) measured during an experimental campaign as inputs. A hybrid approach was used to simulate the contact between the tool and the metal sheet. Indeed, the plunging load was simulated as a prescribed load acting on the punch while the friction heat owing to the interaction of the rotating tool with the metal sheet was simulated as a distributed heat flux over the tool-metal contact surface. This enabled a dramatic reduction of the complexity of the model along with a short simulation runtime. During experimental tests, an IR camera was used to measure the real temperature evolution. These data were used to calibrate and validate the FE model. The results indicated that the developed model can accurately predict the temperature field on the upper metal surface. Thus, it can be readily used to forecast the temperature evolution and distribution and the metalpolymer interface, which is the most influencing factor that determines the mechanical behavior of this type of joints.

The International Journal of Advanced Manufacturing Technology, 2019

Friction stir joining (FSJ) process was preformed to produce hybrid joints between amorphous ther... more Friction stir joining (FSJ) process was preformed to produce hybrid joints between amorphous thermoplastic (polycarbonate) and carbon fiber-reinforced plastic (CFRP) with thermosetting matrix in lap configuration. The influence of the pin plunging depth (within the CFRP) and the tool shoulder plunging depth (within the polycarbonate) was studied to determine the suitability of FSJ process for these types of materials. Single-lap shear tests were conducted to determine the mechanical characteristics of the joints. Results indicated that the strength of the joints was significantly affected by the tool plunging depth, while it was marginally influenced by the tool shoulder plunging depth. The toughness of the joints is greatly influenced by the tool shoulder plunging depth. Morphological characterization and fracture surface analysis clarified the influence of these process parameters on the mechanical characteristics of the joints. The results from this study highlight the high mechanical properties of the joints (up to 12 MPa) due to the replacement of the original epoxy matrix of the composite by means of the polycarbonate.

Procedia Engineering, 2017

In the recent years, high efforts have been spent concerning the development of fast mechanical j... more In the recent years, high efforts have been spent concerning the development of fast mechanical joining processes. This is due to the growing employment of materials that are difficult to weld and hybrid structures involving different materials. Mechanical clinching enables to solving the major concerns in this field. However, the formability of the materials represent a limitation to the successful employment of the process. The present research illustrates a new concept of clinching, namely friction clinching that differs from the conventional process by the employment of a rotating tool, which heats up the sheet (by friction) during the process leading to an increase in the material formability. Preliminary tests were performed to verify the feasibility of the process and determine a sound processing window. The process was applied to join thin aluminium sheets and Carbon Fibre Reinforced Plastic (CFRP) laminate. Morphological analysis and mechanical characterization of the joints was performed in order to evaluate the suitability of such the rotating tool to increase the material formability and thus the aluminium sheet integrity. According to the achieved results, the employment of the rotating tool enables to avoid crack formation in the metal sheet, improves the material flow and reduces the joining forces.

Procedia CIRP, 2017

In this work, the authors present an investigation on technological parameters affecting the flow... more In this work, the authors present an investigation on technological parameters affecting the flow forming process of aluminum alloy 6060 tubular structures and to discuss about the tools maintenance. Flow forming tests were carried out by mounting a single roller on a lathe machine. A 3D thermo-mechanical finite element model was developed to analyze the interaction between the roller and the workpiece in terms of forces, strains and thermal distribution. The effects of friction conditions were investigated through the FE model results and comparing them with acquired thermal maps. The model was validated by comparing the geometrical characteristics of the workpieces, such as the axial elongation, the inner and outer tube diameter. Aluminum spring-back was taken into account with material model adopted in the numerical algorithm. Once collected a complete information on the process parameters, some thermal images were acquired on roller in order to find a parameters set able to reduce the stresses acting on it as far as to obtain the maximum elongation with the minimum number of passes.

The International Journal of Advanced Manufacturing Technology, 2016

This study investigates the influence of the plunging force in friction spot stir welding of poly... more This study investigates the influence of the plunging force in friction spot stir welding of polycarbonate sheets on the mechanical behavior of the welds. Experimental tests were carried out by varying the tool geometry and the applied plunging force. Mechanical tests based on single-lap shear tests were carried out for mechanical characterization of the welds. Thus, the morphology of the welds was analyzed to clarify the influence of the plunging force on geometry and defects of the welds. According to the achieved results, the control of the plunging force allows improving the mechanical behavior of the welds up to 37 % without requiring for additional energy during the welding process or affecting the process production time. The increase of the weld strength is due to the reduction of porosities developing at the interface between the stirred zone and the surrounding material. However, excessive plunging force results in weaker welds due to excessive thinning of the punch-sided sheet. Under optimal conditions, the shear strength of the welds was 34.5 MPa that yields that of the base material.

The International Journal of Advanced Manufacturing Technology, 2016

This study investigates the influence of the tool dimensions on the mechanical behavior of fricti... more This study investigates the influence of the tool dimensions on the mechanical behavior of friction stir spot welds performed on polycarbonate sheets. Different tools were used by varying the pin geometry (cylindrical and tapered) and the diameters of the tool pin and that of the tool shoulder. Morphological analysis was conducted to determine the extension of the welded zone and main defects of the welds. Single lap shear tests were carried out to determine the influence of the tool dimension on the mechanical behavior of the welds. The onset and evolution of failure during the shear tests was analyzed. Five different failure modes were identified which showed both a brittle and ductile behavior. According to the achieved results, the strength of the welds reduced with increasing the pin diameter and taper angle. On the other hand, the strength increased with increasing the tool shoulder diameter. However, the highest specific strength, calculated as the ratio of the shear strength by the tool area, reduced with increasing the shoulder diameter. Under the optimal processing conditions, the strength of the joints reached up to 88 % of the shear strength of the base material.

The International Journal of Advanced Manufacturing Technology, 2015

Laser forming is an incremental sheet-metal forming process that offers the advantages of high fl... more Laser forming is an incremental sheet-metal forming process that offers the advantages of high flexibility, requires no hard tooling, no external forces and easy clamping systems. The main limit of the process lies in small angles produced per pass that dramatically affects the process productivity. Actually, long time should be waited between consecutive passes to avoid surface oxidation either material melting. The present work analyses the productivity in multi-pass laser forming. Single and multi-pass laser forming experimental tests were conducted using a high power diode laser to assess the influence of the main process parameters, i.e. laser power, scanning speed, cooling media and number of irradiations on bending angle and cooling time. An artificial neural network was trained with experimental data to determine the optimal processing conditions that minimize the processing time required to produce a given bending angle. From the achieved results, it is shown the importance of considering the cooling time while choosing the processing conditions in multi-pass laser bending; actually, the study demonstrates that processing conditions that maximize the bending angle per pass do not necessarily correspond to those that reduce the processing time.

The International Journal of Advanced Manufacturing Technology, 2015

The present investigation analyses the force and torque developing during friction stir spot weld... more The present investigation analyses the force and torque developing during friction stir spot welding (FSSW) of thermoplastic sheets varying the main process parameters. In addition, measurements of the tool temperature and those of the material close to the welding region were carried out to better understand the variation of the forces during FSSW and quality of the joints. Experimental tests involving an instrumented drilling machine were performed on polycarbonate sheets. The study involved the variation of dwell time, tool plunge rate and rotational speed. Mechanical characterization and dimensional analysis of the joints were performed in order to assess the influence of the process parameters on the joint quality under considered processing conditions. According to the achieved results, using low values of the plunging speed has beneficial effects on both the process (reduction in the force and torque) and the mechanical behaviour of the joints. Increasing the tool rotational speed results in reduced processing forces and higher material mixing and temperature. The dwell time has a negligible effect on developing forces while it highly influences the material temperature, dimension of the welded region and consequently the mechanical behaviour of the joint.

The International Journal of Advanced Manufacturing Technology, 2014

The joinability of aluminium alloy sheets with reduced ductility produced by mechanical clinching... more The joinability of aluminium alloy sheets with reduced ductility produced by mechanical clinching is analyzed. A modified tool set geometry was developed to reduce the localization and magnitude of plastic strain. Sheets preheating was adopted to increase the material formability. Optical microscopy and scanning electron microscopy were utilized to observe possible presence of cracks in clinched connections and to perform dimensional analysis. Mechanical characterization tests comprising micro-hardness test and single lap shear tests were conducted to evaluate the influence of the processing conditions on joints strength.

The International Journal of Advanced Manufacturing Technology, 2015

ABSTRACT The present investigation is aimed at analysing the influence of the processing speeds a... more ABSTRACT The present investigation is aimed at analysing the influence of the processing speeds and processing times on mechanical behaviour of Friction Stir Spot Welding (FSSW) joints produced on polycarbonate sheets. The analysis involved the variation of rotational speed, tool plunge rate, pre-heating time, dwell time and waiting time. Mechanical characterization of joints was carried out by means of single lap shear test. Experimental tests were conducted according to two full factorial designs. First, an exploratory 25 full factorial plan was carried out to determine the most influencing factors determining the mechanical behaviour of FSSW joints. Then, a 33 optimization plan was performed by varying the most relevant process parameters among three levels. Therefore, analytical models were developed to predict the mechanical behaviour of welds (maximum shear strength, stiffness and absorbed energy) produced under different processing conditions. In addition, an Artificial Neural Network (ANN) model was developed to improve the matching between experimental measurements and model predictions. On the basis of the achieved results, a framework for improving the mechanical performances of thermoplastic joints was established. According to the achieved results, tool plunge rate, dwell time and waiting time are the most influencing parameters for the joint strength and weld extension. On the other hand, pre-heating time and tool rotational speed have lower influence on the mechanical behaviour of FSSW joints.

Journal of Energy Resources Technology, 1995

Major drilling characteristics of Aramid fiber-reinforced plastics are experimentally investigate... more Major drilling characteristics of Aramid fiber-reinforced plastics are experimentally investigated. The chip appears highly deformed and tends to smear on the tool. Forces and, mainly, torque are more influenced by the tool diameter than by the feed rate and cutting speed. On the contrary, the specific cutting energy strongly depends upon the feed rate due to size effects of the tool tip. The damage in the work, i.e., delamination at entry and exit side, can be controlled by taking into account the relationships between machining parameters and forces and torque. Generally, the tool fails by gross brittle failure at the periphery rather than by generalized land wear.

Journal of Materials Processing Technology, 2015

The present investigation is carried out to assess the suitability of the clinching process for p... more The present investigation is carried out to assess the suitability of the clinching process for production of plastic-metal hybrid joints. To this end, a prototypal apparatus was developed to preheat the sheets before joining. A campaign of experimental tests was carried out on aluminium alloy AA5053 and polystyrene. Experimental tests were conducted by varying the main process parameters, i.e. pre-heating conditions (heating time and temperature of heating air) and forming pressure. The joints produced under different operating conditions were observed using optical and stereoscope microscope. In addition, the mechanical behaviours of joints were assessed by conducting single lap shear tests on single joints. Based on the achieved results, the main failure modes were identified and the effect of process parameters on mechanical behaviours of the joints were clarified.

Procedia CIRP, 2013

Laser hardening is a surface treatment process characterized by a high level of performance. The ... more Laser hardening is a surface treatment process characterized by a high level of performance. The resulting physical, chemical, and mechanical properties of the surface layers can be accurately designed by modifying the process parameters i.e., scanning speed, frequency and laser power. Thus, the development of the laser hardening technology requires considerable preliminary work, including the determination of the range of components that may be hardened, the selection of proper treatment conditions and the identification of optimized strategies to employ such a technology for real industrial components. The present research aimed to provide a deep understanding of the laser hardening process. The effect of process parameters i.e., the laser power, the scanning speed, the number of scans and the overlapping, has been assessed by means of a campaign of experimental tests. Thus, an attempt to predict the effect of process parameters of treated components was carried out by developing an expert system using a neural network.

Thin-Walled Structures, 2014

An experimental investigation has been conducted on mechanically clinched joints, produced with f... more An experimental investigation has been conducted on mechanically clinched joints, produced with fixed and extensible dies with different forming forces. Mechanical testing involving single lap shear tests, both with one and two joining points, and peeling tests were conducted under quasi-static conditions to assess the different mechanical behaviors of these joints. The effect of the processing conditions on the main mechanical response of the joints, namely the maximum strength, stiffness and absorbed energy, was investigated. The results showed that the joints produced with the extensible die exhibited a similar strength as compared to those produced with the fixed die in single lap shear tests, while they are characterized by a higher strength (up to 40%) when loaded during the peeling test because of a larger interlock. In addition, the employment of extensible dies allows a drastic reduction of the forming loads as compared to those required by adopting the fixed dies.

Composites, 1985

Abstract Composites of aramid, graphite and glass cloth-reinforced polyester have been cut by a l... more Abstract Composites of aramid, graphite and glass cloth-reinforced polyester have been cut by a laser and the morphology of the cut surfaces examined by scanning electron microscopy. The results are examined using a numerical thermal model and a mechanism for the laser-induced thermal changes observed in the composites is proposed. The thermal properties of the fibres and matrix are the principal factors which affect cutting performance. For the range of experimental parameters used in this study, the quality of the cut surfaces obtained depends on the type of composite being cut.

Composites, 1984

Abstract The results of a study on the behaviour of glass cloth/polyester panels under low veloci... more Abstract The results of a study on the behaviour of glass cloth/polyester panels under low velocity impact are reported. The experimental load/time curve in the elastic region showed good agreement with that predicted by a simple analytical model, based on energy considerations, using elastic properties obtained by static tests. The structural rigidity of the panels was not significantly affected by premature local shear damage, due to the concentration of load, even after first fibre failure. The strength of the material was found to be strongly rate-dependent; as a consequence the response of the structure in the post-elastic region cannot be predicted from the results of static tests.

International Journal of Machine Tools and Manufacture, 2000

The subject of this paper is concerned with an experimental study on the grindability of metal ma... more The subject of this paper is concerned with an experimental study on the grindability of metal matrix composites. Machining by abrasive tools of these materials has been investigated by means of experimental tests carried out with different types of grinding wheels, made with both conventional abrasives and superabrasives. It has been found that the decrease in cutting ability of the

Journal of Manufacturing Processes, 2020

A hybrid non-linear numerical model of the thermal field produced during Friction Assisted Joinin... more A hybrid non-linear numerical model of the thermal field produced during Friction Assisted Joining process of Metal-polymers hybrid joints is developed. The model uses experimental processing loads (plunging load and torque) measured during an experimental campaign as inputs. A hybrid approach was used to simulate the contact between the tool and the metal sheet. Indeed, the plunging load was simulated as a prescribed load acting on the punch while the friction heat owing to the interaction of the rotating tool with the metal sheet was simulated as a distributed heat flux over the tool-metal contact surface. This enabled a dramatic reduction of the complexity of the model along with a short simulation runtime. During experimental tests, an IR camera was used to measure the real temperature evolution. These data were used to calibrate and validate the FE model. The results indicated that the developed model can accurately predict the temperature field on the upper metal surface. Thus, it can be readily used to forecast the temperature evolution and distribution and the metalpolymer interface, which is the most influencing factor that determines the mechanical behavior of this type of joints.

The International Journal of Advanced Manufacturing Technology, 2019

Friction stir joining (FSJ) process was preformed to produce hybrid joints between amorphous ther... more Friction stir joining (FSJ) process was preformed to produce hybrid joints between amorphous thermoplastic (polycarbonate) and carbon fiber-reinforced plastic (CFRP) with thermosetting matrix in lap configuration. The influence of the pin plunging depth (within the CFRP) and the tool shoulder plunging depth (within the polycarbonate) was studied to determine the suitability of FSJ process for these types of materials. Single-lap shear tests were conducted to determine the mechanical characteristics of the joints. Results indicated that the strength of the joints was significantly affected by the tool plunging depth, while it was marginally influenced by the tool shoulder plunging depth. The toughness of the joints is greatly influenced by the tool shoulder plunging depth. Morphological characterization and fracture surface analysis clarified the influence of these process parameters on the mechanical characteristics of the joints. The results from this study highlight the high mechanical properties of the joints (up to 12 MPa) due to the replacement of the original epoxy matrix of the composite by means of the polycarbonate.

Procedia Engineering, 2017

In the recent years, high efforts have been spent concerning the development of fast mechanical j... more In the recent years, high efforts have been spent concerning the development of fast mechanical joining processes. This is due to the growing employment of materials that are difficult to weld and hybrid structures involving different materials. Mechanical clinching enables to solving the major concerns in this field. However, the formability of the materials represent a limitation to the successful employment of the process. The present research illustrates a new concept of clinching, namely friction clinching that differs from the conventional process by the employment of a rotating tool, which heats up the sheet (by friction) during the process leading to an increase in the material formability. Preliminary tests were performed to verify the feasibility of the process and determine a sound processing window. The process was applied to join thin aluminium sheets and Carbon Fibre Reinforced Plastic (CFRP) laminate. Morphological analysis and mechanical characterization of the joints was performed in order to evaluate the suitability of such the rotating tool to increase the material formability and thus the aluminium sheet integrity. According to the achieved results, the employment of the rotating tool enables to avoid crack formation in the metal sheet, improves the material flow and reduces the joining forces.

Procedia CIRP, 2017

In this work, the authors present an investigation on technological parameters affecting the flow... more In this work, the authors present an investigation on technological parameters affecting the flow forming process of aluminum alloy 6060 tubular structures and to discuss about the tools maintenance. Flow forming tests were carried out by mounting a single roller on a lathe machine. A 3D thermo-mechanical finite element model was developed to analyze the interaction between the roller and the workpiece in terms of forces, strains and thermal distribution. The effects of friction conditions were investigated through the FE model results and comparing them with acquired thermal maps. The model was validated by comparing the geometrical characteristics of the workpieces, such as the axial elongation, the inner and outer tube diameter. Aluminum spring-back was taken into account with material model adopted in the numerical algorithm. Once collected a complete information on the process parameters, some thermal images were acquired on roller in order to find a parameters set able to reduce the stresses acting on it as far as to obtain the maximum elongation with the minimum number of passes.

The International Journal of Advanced Manufacturing Technology, 2016

This study investigates the influence of the plunging force in friction spot stir welding of poly... more This study investigates the influence of the plunging force in friction spot stir welding of polycarbonate sheets on the mechanical behavior of the welds. Experimental tests were carried out by varying the tool geometry and the applied plunging force. Mechanical tests based on single-lap shear tests were carried out for mechanical characterization of the welds. Thus, the morphology of the welds was analyzed to clarify the influence of the plunging force on geometry and defects of the welds. According to the achieved results, the control of the plunging force allows improving the mechanical behavior of the welds up to 37 % without requiring for additional energy during the welding process or affecting the process production time. The increase of the weld strength is due to the reduction of porosities developing at the interface between the stirred zone and the surrounding material. However, excessive plunging force results in weaker welds due to excessive thinning of the punch-sided sheet. Under optimal conditions, the shear strength of the welds was 34.5 MPa that yields that of the base material.

The International Journal of Advanced Manufacturing Technology, 2016

This study investigates the influence of the tool dimensions on the mechanical behavior of fricti... more This study investigates the influence of the tool dimensions on the mechanical behavior of friction stir spot welds performed on polycarbonate sheets. Different tools were used by varying the pin geometry (cylindrical and tapered) and the diameters of the tool pin and that of the tool shoulder. Morphological analysis was conducted to determine the extension of the welded zone and main defects of the welds. Single lap shear tests were carried out to determine the influence of the tool dimension on the mechanical behavior of the welds. The onset and evolution of failure during the shear tests was analyzed. Five different failure modes were identified which showed both a brittle and ductile behavior. According to the achieved results, the strength of the welds reduced with increasing the pin diameter and taper angle. On the other hand, the strength increased with increasing the tool shoulder diameter. However, the highest specific strength, calculated as the ratio of the shear strength by the tool area, reduced with increasing the shoulder diameter. Under the optimal processing conditions, the strength of the joints reached up to 88 % of the shear strength of the base material.

The International Journal of Advanced Manufacturing Technology, 2015

Laser forming is an incremental sheet-metal forming process that offers the advantages of high fl... more Laser forming is an incremental sheet-metal forming process that offers the advantages of high flexibility, requires no hard tooling, no external forces and easy clamping systems. The main limit of the process lies in small angles produced per pass that dramatically affects the process productivity. Actually, long time should be waited between consecutive passes to avoid surface oxidation either material melting. The present work analyses the productivity in multi-pass laser forming. Single and multi-pass laser forming experimental tests were conducted using a high power diode laser to assess the influence of the main process parameters, i.e. laser power, scanning speed, cooling media and number of irradiations on bending angle and cooling time. An artificial neural network was trained with experimental data to determine the optimal processing conditions that minimize the processing time required to produce a given bending angle. From the achieved results, it is shown the importance of considering the cooling time while choosing the processing conditions in multi-pass laser bending; actually, the study demonstrates that processing conditions that maximize the bending angle per pass do not necessarily correspond to those that reduce the processing time.

The International Journal of Advanced Manufacturing Technology, 2015

The present investigation analyses the force and torque developing during friction stir spot weld... more The present investigation analyses the force and torque developing during friction stir spot welding (FSSW) of thermoplastic sheets varying the main process parameters. In addition, measurements of the tool temperature and those of the material close to the welding region were carried out to better understand the variation of the forces during FSSW and quality of the joints. Experimental tests involving an instrumented drilling machine were performed on polycarbonate sheets. The study involved the variation of dwell time, tool plunge rate and rotational speed. Mechanical characterization and dimensional analysis of the joints were performed in order to assess the influence of the process parameters on the joint quality under considered processing conditions. According to the achieved results, using low values of the plunging speed has beneficial effects on both the process (reduction in the force and torque) and the mechanical behaviour of the joints. Increasing the tool rotational speed results in reduced processing forces and higher material mixing and temperature. The dwell time has a negligible effect on developing forces while it highly influences the material temperature, dimension of the welded region and consequently the mechanical behaviour of the joint.

The International Journal of Advanced Manufacturing Technology, 2014

The joinability of aluminium alloy sheets with reduced ductility produced by mechanical clinching... more The joinability of aluminium alloy sheets with reduced ductility produced by mechanical clinching is analyzed. A modified tool set geometry was developed to reduce the localization and magnitude of plastic strain. Sheets preheating was adopted to increase the material formability. Optical microscopy and scanning electron microscopy were utilized to observe possible presence of cracks in clinched connections and to perform dimensional analysis. Mechanical characterization tests comprising micro-hardness test and single lap shear tests were conducted to evaluate the influence of the processing conditions on joints strength.

The International Journal of Advanced Manufacturing Technology, 2015

ABSTRACT The present investigation is aimed at analysing the influence of the processing speeds a... more ABSTRACT The present investigation is aimed at analysing the influence of the processing speeds and processing times on mechanical behaviour of Friction Stir Spot Welding (FSSW) joints produced on polycarbonate sheets. The analysis involved the variation of rotational speed, tool plunge rate, pre-heating time, dwell time and waiting time. Mechanical characterization of joints was carried out by means of single lap shear test. Experimental tests were conducted according to two full factorial designs. First, an exploratory 25 full factorial plan was carried out to determine the most influencing factors determining the mechanical behaviour of FSSW joints. Then, a 33 optimization plan was performed by varying the most relevant process parameters among three levels. Therefore, analytical models were developed to predict the mechanical behaviour of welds (maximum shear strength, stiffness and absorbed energy) produced under different processing conditions. In addition, an Artificial Neural Network (ANN) model was developed to improve the matching between experimental measurements and model predictions. On the basis of the achieved results, a framework for improving the mechanical performances of thermoplastic joints was established. According to the achieved results, tool plunge rate, dwell time and waiting time are the most influencing parameters for the joint strength and weld extension. On the other hand, pre-heating time and tool rotational speed have lower influence on the mechanical behaviour of FSSW joints.

Journal of Energy Resources Technology, 1995

Major drilling characteristics of Aramid fiber-reinforced plastics are experimentally investigate... more Major drilling characteristics of Aramid fiber-reinforced plastics are experimentally investigated. The chip appears highly deformed and tends to smear on the tool. Forces and, mainly, torque are more influenced by the tool diameter than by the feed rate and cutting speed. On the contrary, the specific cutting energy strongly depends upon the feed rate due to size effects of the tool tip. The damage in the work, i.e., delamination at entry and exit side, can be controlled by taking into account the relationships between machining parameters and forces and torque. Generally, the tool fails by gross brittle failure at the periphery rather than by generalized land wear.

Journal of Materials Processing Technology, 2015

The present investigation is carried out to assess the suitability of the clinching process for p... more The present investigation is carried out to assess the suitability of the clinching process for production of plastic-metal hybrid joints. To this end, a prototypal apparatus was developed to preheat the sheets before joining. A campaign of experimental tests was carried out on aluminium alloy AA5053 and polystyrene. Experimental tests were conducted by varying the main process parameters, i.e. pre-heating conditions (heating time and temperature of heating air) and forming pressure. The joints produced under different operating conditions were observed using optical and stereoscope microscope. In addition, the mechanical behaviours of joints were assessed by conducting single lap shear tests on single joints. Based on the achieved results, the main failure modes were identified and the effect of process parameters on mechanical behaviours of the joints were clarified.

Procedia CIRP, 2013

Laser hardening is a surface treatment process characterized by a high level of performance. The ... more Laser hardening is a surface treatment process characterized by a high level of performance. The resulting physical, chemical, and mechanical properties of the surface layers can be accurately designed by modifying the process parameters i.e., scanning speed, frequency and laser power. Thus, the development of the laser hardening technology requires considerable preliminary work, including the determination of the range of components that may be hardened, the selection of proper treatment conditions and the identification of optimized strategies to employ such a technology for real industrial components. The present research aimed to provide a deep understanding of the laser hardening process. The effect of process parameters i.e., the laser power, the scanning speed, the number of scans and the overlapping, has been assessed by means of a campaign of experimental tests. Thus, an attempt to predict the effect of process parameters of treated components was carried out by developing an expert system using a neural network.

Thin-Walled Structures, 2014

An experimental investigation has been conducted on mechanically clinched joints, produced with f... more An experimental investigation has been conducted on mechanically clinched joints, produced with fixed and extensible dies with different forming forces. Mechanical testing involving single lap shear tests, both with one and two joining points, and peeling tests were conducted under quasi-static conditions to assess the different mechanical behaviors of these joints. The effect of the processing conditions on the main mechanical response of the joints, namely the maximum strength, stiffness and absorbed energy, was investigated. The results showed that the joints produced with the extensible die exhibited a similar strength as compared to those produced with the fixed die in single lap shear tests, while they are characterized by a higher strength (up to 40%) when loaded during the peeling test because of a larger interlock. In addition, the employment of extensible dies allows a drastic reduction of the forming loads as compared to those required by adopting the fixed dies.

Composites, 1985

Abstract Composites of aramid, graphite and glass cloth-reinforced polyester have been cut by a l... more Abstract Composites of aramid, graphite and glass cloth-reinforced polyester have been cut by a laser and the morphology of the cut surfaces examined by scanning electron microscopy. The results are examined using a numerical thermal model and a mechanism for the laser-induced thermal changes observed in the composites is proposed. The thermal properties of the fibres and matrix are the principal factors which affect cutting performance. For the range of experimental parameters used in this study, the quality of the cut surfaces obtained depends on the type of composite being cut.

Composites, 1984

Abstract The results of a study on the behaviour of glass cloth/polyester panels under low veloci... more Abstract The results of a study on the behaviour of glass cloth/polyester panels under low velocity impact are reported. The experimental load/time curve in the elastic region showed good agreement with that predicted by a simple analytical model, based on energy considerations, using elastic properties obtained by static tests. The structural rigidity of the panels was not significantly affected by premature local shear damage, due to the concentration of load, even after first fibre failure. The strength of the material was found to be strongly rate-dependent; as a consequence the response of the structure in the post-elastic region cannot be predicted from the results of static tests.