Papers by Keyword: Formability

Abstract: Elongation properties of car roof interior fabric were studied in this article.The FM02-11 type universal material testing machine was employed to test the static and dynamic elongation properties of warp knitted napped fabric 1,2,3,warp knitted fabric 1,2,pile composite fabric A1,A2,A3 and sponge composite fabric C1,C2,C3,C4. The results indicated all can meet the general standard for car interior ceiling fabric.According to the dynamic elongation, the bigger the deformation ratio, the better the formability.

Abstract: In the last ten years, the automotive sector presents large interest for light alloys tubes for structural and body car parts to reduce CO₂ emissions. Tubes hydroforming is one of the most popular processes to obtain complex parts by using liquids as active part of the dies (i.e. water-or oil-based emulsions) with reduced costs of equipment and machines. However, when elevated temperatures should be used to increase the material formability, hydroforming processes are strongly limited due to the boiling point of liquids. The use of gas at elevated temperature in the so-called Hot Metal Gas Forming process (HMGF) has shown promising capabilities thanks to the increased formability and the possibility to form parts with lower pressures. The paper focuses on a novel experimental set-up to evaluate the tubes formability at high temperatures. Tubes are heated by electric current and air in pressure is used to form the material. Aluminium alloy AA6060 tubes specimens were used to test the experimental equipment and evaluate temperature and pressure ranges able to shape the material.

Abstract: The lightweight metal alloy Ti-6Al-4V is widely used in the aeronautical industry due to its excellent mechanical properties. However, it is known the difficulty to deform Ti-6Al-4V sheets at room temperature because of its microstructure conditions. The present work focuses on the evaluation of formability of Ti-6Al-4V sheets using hot single point incremental forming (SPIF) process which it seems appropriate to produce small batches of parts due to its flexibility as it allows a significant reduction of costs and lead times. In order to characterize the SPIF of Ti-6Al-4V under hot forming conditions, a set of forming trials evaluation tests was carried out. The obtained results have allowed identifying the key process features and have demonstrated the potential of the proposed approach to hot form of small amounts of Ti-6Al-4V parts.

Abstract: Aluminium is a potential light weight alternative to steel for deep drawn sheet components, but generally does not compare well to steels in terms of formability. Research in polycrystalline plasticity indicates applying shear to rolled fcc alloys improves their deep drawability by favourably modifying their crystallographic texture. Such processing could be realised industrially by cold asymmetric rolling (ASR), but in order to gain detailed understanding of the influence of process parameters on the evolution and through thickness homogeneity of the texture a validated full field multi-scale model of the process is required. This study examines the ability of a hierarchical multi-scale approach to predict evolved textures for aluminium sheet subjected to a mechanical test exhibiting a deformation mode relevant for ASR, namely simple shear. The homogeneity of the deformation field is assessed with full field strain measurement by digital image correlation, and macrotexture is measured by x-ray diffraction. The discrepancies are discussed and further work to validate the modelling approach for simulation of texture evolution in the ASR process is briefly outlined.

Abstract: In this paper the effects of shape and tool material on the output parameters on spinning of aluminum sheets are investigated. To achieve this purpose, four kinds of roller tools with the same shapes and with different materials including mild steel, ertalon, polyamid and caoutchouc were used and some parts were spun by the same geometric form; moreover, in order to investigate the effects of roller nose radius on output parameters such as surface smoothness and thickness distribution, three caoutchouc roller tools with different nose radius were used at the same condition. The results show that using a caoutchouc roller tool for spinning of aluminum sheets leads to the best surface smoothness, while using a steel tool because of its roughness is not suitable. Ertalon and polyamid roller tool have a high rate of wearing. Furthermore, in the constant feedrate by increasing of roller nose radius the contact area between roller and workpiece is increased and surface smoothness is followed, relatedly.

Abstract: Present work focusses on the effect of stress relaxation on the tensile behaviour of two commercially pure titanium alloys of different strength levels (Grade 1 and Grade 4) subjected to tensile tests at room temperature. The stress relaxation tests were performed by interrupting the tensile tests at regular strain intervals of 5% in the plastic region of the tensile curve and compared to the monotonic tensile tests at different strain rates ranging from 10^-4 to 10^-1s^-1. To understand the effect of anisotropy, samples were taken along 0° and 90° to rolling direction (RD) for both the alloys. Improvement in ductility of different levels at all the strain rates was observed in both the alloys when stress relaxation steps were introduced as compared to monotonic tests. However there is not much change in the flow stress as well as in strain hardening behaviour of the alloys. The true stress-true strain curves of Grade 4 samples taken in 90° to RD exhibited discontinuous yielding phenomenon after the yield point, which is termed as a yield-point elongation (YPE). The improvement in ductility of the Cp-Ti alloys can be linked to recovery process occurring during the stress relaxation steps which resulted in the improvement in ductility after repeated interrupted tensile tests. The paper presents and summarise the results based on the stress relaxation for the two different alloys.

Abstract: ATI 425^® Alloy, nominal composition Ti-4.0Al-2.5V-1.5Fe-0.25O, is a new alpha/beta Ti alloy of significant commercial interest as a viable replacement for Ti-6Al-4V, CP-Ti, and other titanium alloys in a variety of aerospace applications. ATI 425^® Alloy offers properties comparable to Ti-6Al-4V alloy with significant improvements in formability, both at room and elevated temperatures. The reasons for the improved formability, particularly at low temperatures, are not well understood. The development of a thorough understanding is complicated by the wide array of phases, microstructures, and deformation paths available via thermomechanical processing in alpha/beta titanium alloys. In this paper, theories of strengthening and dislocation mobility in titanium and HCP metals will be reviewed and applied to better understand why ATI 425^® Alloy offers a unique combination of strength and formability not obtainable by conventional alpha/beta titanium alloys. Subsequently, the application of the improved formability to a range of product forms including sheet, tubing, and forgings will be discussed.

Abstract: Currently magnesium alloys are used for different applications in the transportation industry where cast magnesium alloys dominate the market. Although cast alloys predominate over wrought products such as extrusions, forgings, sheet and plate, the latter are also being used in a variety of different applications. Recently, a growing interest in the automotive industry in looking at potential applications for magnesium turned back towards wrought alloys. Typically, applications of magnesium sheets are sought in automotive or aeronautics industry. However, the spectrum of potential applications can be significantly expanded. For example, body protection systems for civil services like police, custom officers and prison personnel currently include anatomically shaped aluminium alloy sheets. Replacement of aluminium alloys by magnesium to result in substantial weight savings up to 30%.

Abstract: Cosma R&D investigated a low temperature warm forming process by which a magnesium ZEK 100 door inner part with a single-stage draw depth of 144 mm was successfully formed. The warm forming process is comprised of three steps: 1) heating pre-lubricated blanks in an oven at temperatures ranging from 215°C to 260 °C, 2) robotic transfer of the heated blank to a mechanical stamping press, 3) forming of the panel in room temperature stamping die at speed of about 160 mm/s. The effect of process parameters on the formability of the part, as well as, the post-forming properties including the mechanical properties, microstructure evolution and deformation thinning are also presented. The result indicates that Magnesium ZEK 100 exhibits superior low temperature warm formability over Magnesium AZ31B, and the developed warm forming process is promising and potential for volume production of magnesium automotive parts.

Abstract: Three examples involving size effects are presented with implications concerning the formability: small Ni-20wt.%Cr resistive bridges, magnetic micro-sensors performed with (Ni, Co, Fe) based alloys and copper clad aluminum thin wires. The mechanical properties are directly linked to the ratio thickness over grain size (t/d ratio) of the parts. These metallurgical considerations must be taken into account when we are concerned by the numerical simulation of the process of such components. It is shown that the simulations can correctly reproduce the softening effect linked to a decrease in thickness and in number of grains across the thickness: the quality of the final shape strongly depends on the number of grains across the thickness. Finally the effect of a moderate increase in temperature on these results will be briefly reported.