Since 10 years it has been trying to develop an innovative welding technique for titanium. The di... more Since 10 years it has been trying to develop an innovative welding technique for titanium. The difficulties encountered are mainly related to the need of developing a joint free from defects (e.g. undercut and porosity). The attention of the researchers passed from the traditional TIG welding to Laser Beam Welding [1]. The laser technology, while achieving a better coupling, requires a great deal of energy, especially the high-power Nd:YAG lasers [2]. Adjusting the parameters of the laser, welds almost free of defects can be obtained, so it would be necessary to plan the experiment using a DoE [3]. This is not possible for laser welding because this type of technology has limitations that do not allow for proper planning. The aim of this study is to provide a welding process that could produce high quality joints. Static tensile tests showed a high resistance joints, fatigue strength is strongly influenced by the presence of undercut, so it is important to work in conditions where s...
The present work shows a model to evaluate machining accuracy in turning of a multi-diameter bar.... more The present work shows a model to evaluate machining accuracy in turning of a multi-diameter bar. The proposed model has been applied to the most common turning schemes related to workpiece fixturing. Some numerical examples have been computed using the proposed model to predict the diameter error along the workpiece and the cutting force along the workpiece axis.
The paper surveys the current status of the models for representing, manipulating and analyzing d... more The paper surveys the current status of the models for representing, manipulating and analyzing dimensioning and tolerancing data behind the major computer-aided tolerancing (CAT) systems, now commercially available. The solid models and tolerance models that these systems adopt, and their implications for the successful integration of CAT and CAD/CAM are discussed. There are two main purposes. First, the attention is focused on the theoretical backgrounds of every CAT system analyzed, for understanding its limits and its usefulness in design and manufacturing practice. The other purpose is to present a comparison among these systems to support the designer and the manufacturing engineer, as well as the researchers, in the choice of the system will be more proper to everyone. Finally, the research work that remains to be carried out, to improve the future CAT systems and their integration with CAD/CAM is sketched out.
ABSTRACT Tensile properties of AA6156-T4 friction stir welded joints were studied in the as-welde... more ABSTRACT Tensile properties of AA6156-T4 friction stir welded joints were studied in the as-welded and T62 post-weld heat treated condition. To analyze the influence of rotating and welding speed on the 0.2 % proof stress and tensile strength of the two classes of joints, a complete full factorial design with three levels for each studied parameter was performed. Statistical analyses were carried out to establish empirical models of the tensile properties of the joints as a function of the studied welding parameters. The obtained models were validated by statistical tools such as Mallow's CP, S, R2 and R2(adj). The developed regression models can be effectively used to predict the mechanical properties of the joints at 95 % confidence level.
ABSTRACT Nowadays the fiber reinforced materials are finding more and more widespread use in aero... more ABSTRACT Nowadays the fiber reinforced materials are finding more and more widespread use in aeronautic field due to their features of lightness, high strength and flexibility of manufacturing systems. The only way for metals to remain competitive for the aerospace applications is to improve new technologies and alloys in order to realize lighter and more resistant structures. The development of new alloys (lighter and stronger) and technologies will allow to use metals also in the future for aerospace applications. In this scenario the research activity has a fundamental importance, and the key point is to work simultaneously on both innovative materials and new technologies that allow to obtain the best performances with the innovative alloys. Welding is nowadays playing a fundamental role in transport industry thanks to the important advantages it allows. Friction Stir Welding (FSW) [1] is one of the most promising welding techniques, particularly suitable for applying to light alloys. FSW in butt joint configuration allows to achieve very high mechanical performances, often absolutely superior to those achievable with all other joining techniques, and lots of researches and results are now available [2]. The AA 2139 is an innovative Al-Cu-Ag alloy that has higher mechanical performances than the conventional 2xxx series aluminum alloys. The AA 2139 is designed to work in service in T8 temper condition, but is simplest to work in T3 temper condition. The aim of this work is to compare the performances of AA 2139 butt joints welded in T8 temper conditions, presented in a previous work [3], with the ones of joints welded in T3 condition and heat treated post welding in order to achieve the T8 temper condition.
Since 10 years it has been trying to develop an innovative welding technique for titanium. The di... more Since 10 years it has been trying to develop an innovative welding technique for titanium. The difficulties encountered are mainly related to the need of developing a joint free from defects (e.g. undercut and porosity). The attention of the researchers passed from the traditional TIG welding to Laser Beam Welding [1]. The laser technology, while achieving a better coupling, requires a great deal of energy, especially the high-power Nd:YAG lasers [2]. Adjusting the parameters of the laser, welds almost free of defects can be obtained, so it would be necessary to plan the experiment using a DoE [3]. This is not possible for laser welding because this type of technology has limitations that do not allow for proper planning. The aim of this study is to provide a welding process that could produce high quality joints. Static tensile tests showed a high resistance joints, fatigue strength is strongly influenced by the presence of undercut, so it is important to work in conditions where s...
The present work shows a model to evaluate machining accuracy in turning of a multi-diameter bar.... more The present work shows a model to evaluate machining accuracy in turning of a multi-diameter bar. The proposed model has been applied to the most common turning schemes related to workpiece fixturing. Some numerical examples have been computed using the proposed model to predict the diameter error along the workpiece and the cutting force along the workpiece axis.
The paper surveys the current status of the models for representing, manipulating and analyzing d... more The paper surveys the current status of the models for representing, manipulating and analyzing dimensioning and tolerancing data behind the major computer-aided tolerancing (CAT) systems, now commercially available. The solid models and tolerance models that these systems adopt, and their implications for the successful integration of CAT and CAD/CAM are discussed. There are two main purposes. First, the attention is focused on the theoretical backgrounds of every CAT system analyzed, for understanding its limits and its usefulness in design and manufacturing practice. The other purpose is to present a comparison among these systems to support the designer and the manufacturing engineer, as well as the researchers, in the choice of the system will be more proper to everyone. Finally, the research work that remains to be carried out, to improve the future CAT systems and their integration with CAD/CAM is sketched out.
ABSTRACT Tensile properties of AA6156-T4 friction stir welded joints were studied in the as-welde... more ABSTRACT Tensile properties of AA6156-T4 friction stir welded joints were studied in the as-welded and T62 post-weld heat treated condition. To analyze the influence of rotating and welding speed on the 0.2 % proof stress and tensile strength of the two classes of joints, a complete full factorial design with three levels for each studied parameter was performed. Statistical analyses were carried out to establish empirical models of the tensile properties of the joints as a function of the studied welding parameters. The obtained models were validated by statistical tools such as Mallow's CP, S, R2 and R2(adj). The developed regression models can be effectively used to predict the mechanical properties of the joints at 95 % confidence level.
ABSTRACT Nowadays the fiber reinforced materials are finding more and more widespread use in aero... more ABSTRACT Nowadays the fiber reinforced materials are finding more and more widespread use in aeronautic field due to their features of lightness, high strength and flexibility of manufacturing systems. The only way for metals to remain competitive for the aerospace applications is to improve new technologies and alloys in order to realize lighter and more resistant structures. The development of new alloys (lighter and stronger) and technologies will allow to use metals also in the future for aerospace applications. In this scenario the research activity has a fundamental importance, and the key point is to work simultaneously on both innovative materials and new technologies that allow to obtain the best performances with the innovative alloys. Welding is nowadays playing a fundamental role in transport industry thanks to the important advantages it allows. Friction Stir Welding (FSW) [1] is one of the most promising welding techniques, particularly suitable for applying to light alloys. FSW in butt joint configuration allows to achieve very high mechanical performances, often absolutely superior to those achievable with all other joining techniques, and lots of researches and results are now available [2]. The AA 2139 is an innovative Al-Cu-Ag alloy that has higher mechanical performances than the conventional 2xxx series aluminum alloys. The AA 2139 is designed to work in service in T8 temper condition, but is simplest to work in T3 temper condition. The aim of this work is to compare the performances of AA 2139 butt joints welded in T8 temper conditions, presented in a previous work [3], with the ones of joints welded in T3 condition and heat treated post welding in order to achieve the T8 temper condition.
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