Papers by Keyword: Sheet Forming

Abstract: To address the challenges met in the manufacturing of state-of-the-art multi-material structures, this work employs a novel one-shot stamping process with single-stamp forming of advanced high-strength steels (AHSS)-based multi-material structures consisting of dual-phase steel (DP780) and low-cost glass fibre-reinforced polyamide 6 (GF/PA6). The effects of DP780 surface treatment and forming temperature on interfacial bonding with GF/PA6 were first assessed using double cantilever beam (DCB) tests, alongside tensile tests of DP780 to assess post-stamping performance. Sandblasting on DP780 significantly improved bonding strength compared to non-treated surface, while the interfacial fracture energy (G_C) increased with forming temperature up to 350 °C before decreasing at higher temperatures, which is attributed to PA6 squeeze-out and DP780 surface oxidation. Although the tensile strength for DP780 decreased with increasing temperature, the yield strength peaked at 350 °C, identifying sandblasting and a forming temperature of 350 °C as the optimal processing conditions for DP780. Based on the optimal conditions determined, high-quality U-shaped demonstrator components were successfully produced with good surface finish, minimal polymer squeeze-out, and no observable defects, via further optimisation of the forming conditions.

Abstract: To produce functional cups by press forming, clad cups with a corrugated structure with voids like the cross section of corrugated cardboard were formed. Deep drawing, which is one type of press forming, is a plastic processing technology that forms thin sheets into three-dimensional containers. In the experiment, pure titanium TP270 and ultra-low carbon steel SPCC were used as test materials. The blank sheet thickness was 0.3 mm and the diameter was 80 mm to 90 mm. To form the corrugated cup, the roller ball die with steel balls installed on the shoulder of the die was prototyped. The steel balls were made of bearing steel JIS-SUJ2 and had diameters of 6.4 mm and 7.5 mm. The corrugated clad cup was formed by the composite die combined with a conventional die. Three conventional dies and two roller ball dies were used to obtain two corrugated layers with voids. The lubricant was a tool oil containing molybdenum disulfide powder. The sheet thickness strain distribution and residual stress distribution of the cup were evaluated. No destruction of the cup occurred during deep drawing. A regular wavy structure was observed in the cross section of the cup. The maximum reduction in the cup thickness was approximately 10 %. The residual stress on the outside of the cup was tensile stress from the bottom to the opening of the cup. The composite die made it possible to form a functional cup.

Abstract: High-speed roll casting of AC2A aluminum alloys for casting was performed at speeds from 20 to 40 m/min using an unequal-diameter twin-roll caster to investigate the improvement of ductility and sheet forming with roll-cast strips. The width of the cast strips was 100 mm. The roll-cast strips were homogenized and cold rolled to a thickness of 1 mm, and the resulting cold-rolled strips were then annealed before tensile testing, deep drawing, V-bending, and three-roll bending. Tensile testing was also performed for a T6 heat-treated test piece. The microstructure was observed using optical microscopy.

Abstract: In this paper the issues of modeling the process of forming sheet materials using method of incremental forming for the manufacture of thin-walled non-axisymmetric parts. The proposed method of forming implemented by deformation of sheet material by providing the required trajectory of movement of the working tool in order to obtain the surface of a product of a given shape. Simulation and analysis of all experiment results are carried out.

Abstract: The existing double sided incremental forming (DSIF) mostly uses two tools with the same diameter as the upper/lower tools, which is not conducive to improve the forming quality and forming efficiency. In this paper, the influence of the different combination of the upper and lower tool head diameters on the thickness distribution and the contour dimension accuracy of the formed part is studied by using ANSYS / LS-DYNA software and by taking the model with bidirectional convex features as the research object. It is found that the reasonable combination of different diameters of the upper/lower tools based on the characteristics of the parts to be formed can improve the forming quality and forming efficiency.

Abstract: In order to analysis the effect of the sheet metal postures on the forming thickness, the horizontal sheet posture, the multidirectional sheet postures with the inclined angle of , and the multidirectional sheet postures obtained after optimization were respectively used for comparative analysis through the numerical simulation against the same model. The result shows that the optimized multidirectional sheet metal postures can reduce the overall thickness difference of the formed part and realize the thickness uniformity.

Abstract: Single Point Incremental Forming (SPIF) technology has become popular and familiar in sheet materials forming, especially in single manufacturing, prototype manufacturing and in the medical field.... However, sheet materials with high hardness and durability are difficult to deform and shape because of their high properties. In that case, when we determine the main logical technological parameters such as forming temperature T (°C), speed of forming V_xy tool (mm/min), depth tool feeding z (mm) and tool diameter D (mm) tool, it is possible to apply HOT SPIF technology at high temperature to form these materials. The paper presents a study of optimization the main technology parameters when processing non-alloy Titanium sheet materials with HOT SPIF technology to get the smallest depth dimension error ΔH.

Abstract: Sheet forming of galvanized metals presents a great challenge for automobile industry. This is partially caused by a significant induced plastic deformation and high contact friction during forming, which results in pulverization, flaking and failure seen in the zinc layer. Cupping tests is used to study the formability of the galvanized sheets, for a better understanding of microscopic failure mechanisms of the zinc layer. The results show that during the cupping of the galvanized sheet, the zinc layers of each deformed zone encounter varying degrees of failure behaviors. The regions next to the fillets of the punch and the blank holder ring are more serious. In these severe failure areas, the residual stresses in the zinc layer are shown as tensile in nature; and increase with the degree of deformation increasing. The galvanized layers rupture prematurely prior to any damage seen in the steel substrate; thus leading to chalking, flaking and final failure. The results provide a theoretical guidance for improving formability of galvanized sheets.

Abstract: Formability in sheet forming processes are usually analyzed by standardized tests, which often requires different test equipment associated with high initial investment cost. The present study purposes a flexible test tooling system for hydraulic bugle test apparatus that allows to evaluate the impact of size effect on the formability of thin metallic sheets. Finite Element Method was used for concept and design of the tooling system and experimental tests were carried out with thin sheets of SUS316L stainless steel to assess the overall performance of the tooling system.

Abstract: Cladding is the bonding together of dissimilar metals. One of clad products is the titanium clad steel sheet. It is effective to cover with pure titanium sheet to improve the corrosion resistance of the steel sheet. Titanium clad steel sheets are often achieved by rolling sheets together under high pressure. In the current study, the blank comprising three laminar non-bonded sheets, such as the titanium/steel/titanium sheet, is arranged in the die. The formability of pure titanium clad sheet by multistage deep drawing was investigated to enhance corrosion resistance of steel cup. In the experiment, the blanks were pure titanium sheets JIS1-TP270, JIS2-TP340, ultralow-carbon steel SPCC, and stainless steel SUS316L. The initial thickness of the sheet was 0.2 to 0.5 mm in thickness. The blank diameter was 70 mm. The blanks are merely adjacent sheet; however, not joined with each other. In the deep drawing process, a hydraulic press was used in the experiment and the forming speed for the press was about 10 mm/min. The lubricant used was the solid powders of molybdenum disulfide. For the prevention, pure titanium blank was treated by oxide coating. The conditions of heat treatment were annealed at 973 K for 3.6 ks to 7.2 ks. By oxide coating, the titanium sheet has sufficient ability in preventing the seizure in multistage deep drawing. The drawn cups of the three-layer laminated sheet were formed. The seizure did not cause. The oxidatively-treated titanium sheets have sufficient ability in preventing the seizure. In addition, the clad cups until 6th stage were formed by multistage deep drawing. Long clad cups were successfully formed in multistage deep drawing process.