177,800 research outputs found
R v Shivpuri [1987] AC 1, House of Lords
No full textEssential Cases: Criminal Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in R v Shivpuri [1987] AC 1, House of Lords. The document also included supporting commentary from author Jonathan Herring.</p
Material flow and CDRX phenomena determining joint resistance in AA7075-T6 friction stir welding
No full textDesign of the friction stir welding tool using the continuum based FEM model
No full textIn friction stir welding (FSW), the welding tool geometry plays a fundamental role in obtaining desirable microstructures in the weld and
the heat-affected zones, and consequently improving strength and fatigue resistance of the joint. In this paper, a FSW process with varying pin geometries (cylindrical and conical) and advancing speeds is numerically modeled, and a thermo-mechanically coupled, rigid-viscoplastic, fully 3D FEM analysis able to predict the process variables as well as the material flow pattern and the grain size in the welded joints is performed. The obtained results allow finding optimal tool geometry and advancing speed for improving nugget integrity of aluminum alloys
Influence of geometrical ratios in forgeability of complex shapes during hot forging of Ti-6Al-4V titanium alloy
No full textAbstractTitanium alloys are considered desirable materials when both mechanical properties and weight reduction are requested at the same time. This class of materials is widely used in application fields, like aeronautical, in which common steels and light-weight materials, like aluminum alloys, are not able to satisfy all operative service conditions. Most of manufacturing processes of titanium alloy components are based on machining operations, which allow obtaining very accurate final shapes but, at the same time, are affected by several disadvantage like material waste and general production costs. During the last decade, the forging processes for titanium alloys have attracted greater attention from both industrial and scientific/academic researchers because of their potential in providing a net shaped part with minimal need for machining. In this paper, a numerical analysis of the forging process design for an Ti-6Al-4V titanium alloy aerospace component is presented that focuses on the role of material evolution during thermomechanical processing. This component geometry is characterized by thin webs and ribs, and sharp corner and fillet radii. The numerical model was tested and validated by means of comparison with real experimental forgings in order to verify the quality in the prediction of material flow and microstructure evolution. Moreover, the analysis of forgeability of the same component with more critical geometrical ratios is considered in order to test the capability of code to support the forging sequence design in the case of a complex shape component
Improving Friction Stir Welding of blanks characterized by different thickness
No full textFriction stir welding (FSW) appears to be a promising process even in the welding of blanks of different thicknesses. Actually, such particular tailor welded blanks (TWBs) are usually characterized by a reduction in ductility due to the utilized fusion welding process. In this paper the authors, starting from a preliminary feasibility study, investigate the possibility to improve the mechanical performances of friction stir welded blanks of aluminum alloy with different thicknesses. Both experiments and a FE analyses are developed for a few case studies with different thickness ratios between the blanks. The numerical investigations are performed with the aim to highlight the material temperature distribution during the process in order to determine process conditions for which an almost symmetric thermal flow is obtained in the two blanks of the joint. In this way, a few simple process design rules are derived and verified through experiments. In particular a thickness ratio up to 2 was considered and a joint resistance of about the 80% of the parent material ultimate tensile strength was observed
Influence of material characteristics on plastomechanics of the fsw process for T-joints
No full textThe potential of friction stir welding (FSW) has thoroughly been investigated by several authors, however their focus has primarily been on butt joints. T-joints are of paramount interest for transportation industries especially due to their capacity to straighten panels. Welding of T-joints is very challenging due to thin walls, poor location of the rib–web interface and the requirements for corner-fillets. This paper investigates FSW of T-joints of two popular aluminum alloys, i.e. 2024-T4 and 6082-T6, and the role played by the material characteristics on joining. First, an experimental study is carried out with specially designed fixture to determine the effect of process conditions. Then, the joints are metallurgically and mechanically evaluated. Finally using a numerical model of the process previously developed by the authors, the thermal and plastic flow fields for the two alloys are calculated and compared. It is found that the material dependent thermal and plastic fields affect the state of TMAZ, HAZ and nugget-region in the joint and that the low-strength high-work hardening alloy 6082 provides a much better joint integrity than the higher-strength low-hardening 2024 primarily due to the greater penetration of the plastic zone in the former
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