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Currently, dual-layer tubes play a pivotal role in sectors like nuclear, oil, gas, and steam generation. Recent research focuses on enhancing energy absorption in these tubes using the spinning forming process. This thin-walled nature benefits their application as efficient energy absorbers in transportation like trains and aircraft. A novel approach integrates coarse and fine-threaded ridges between steel and aluminum layers to create a mechanical interlock using the spinning forming technique. This interlock enhances the bond through flow forming, resulting in robust dual-layer tubes. Interlayer connection strength is rigorously tested through shear tests, pre and post flow forming, indicating a significant post-flow forming enhancement. This process substantially bolsters the overall structural integrity of dual-layer tubes. In crush tests, both single-layer and dual-layer steel and aluminum tubes undergo pressing through flow forming. Comparative analysis of energy absorption parameters—specific energy and crushing percentage—reveals notable performance differences. An annealed version of the tube with an aluminum layer is also included due to prior aluminum layer failures. Among dual-layer samples, the flow formed variant with fine-threaded ribs exhibits superior energy absorption and bonding. Finite element simulation of the pressed dual-layer sample demonstrates an 8.42 % deviation between simulated and experimental energy absorption outcomes. The study highlights that tightly bonded layers result in enhanced bonding characteristics.

This study introduces a new rotary draw bending method that utilizes a variable curvature bending die. Unlike traditional methods that bend tubes with a fixed radius, this method gradually deforms the tube from a large to a small radius. The curvature of the bending die is determined by using an involute curve as the equation for the geometric location of the variable curvature. Hydroforming technology, utilizing fluid under pressure, replaces the mandrel in the rotational tensile bending process. The research was conducted using a thin-walled AA6063 tube with a 13.88 diameter-to-thickness ratio. The bending process was examined at critical bending ratios of 1 and 1.6 times the diameter, with a 90° bending angle. The maximum pressure that can be applied in any bend radius ratio was predicted using the necking criterion. The simulation and experimental tests analyzed the effects of internal fluid pressure and bend die curvature on defects such as wall thinning in the outer curvature of the bend, thickening of the wall in the inner curvature of the bend, and cross-section non-roundness. The results indicate that, at constant pressure, the amount of thinning and thickening of the bent tube is significantly improved when using the variable radius bending die compared to the fixed radius die.

In this study, the plastic deformation of a metallic bipolar plate with a serpentine flow field was investigated during the stamping process. The strain path and thickness distribution in 304 stainless steel bipolar plates with a thickness of 0.1 mm were determined. To achieve this purpose, the process was simulated by the ABAQUS commercial finite element code, and the validity of the results was evaluated by experimental tests under simple and lubricated conditions. According to the results, the flow of material has a significant effect on the thickness distribution of the central and lateral channels, and the thickness reduction percentage of the central channel in the longitudinal, diagonal, and transverse directions is higher than the lateral one. The maximum thickness reduction in the central channels is observed in the longitudinal direction, while the diagonal direction is considered as a critical direction for lateral channels. Due to the existence of the equibiaxial tension strain path in the diagonal direction, significant thickness reduction is observed in both the side and the rib zone of the channels. However, using lubricant led to a decrease in the thickness reduction percentage by improving the flow of material into the die cavity. Moreover, under lubricated conditions, the critical area is transferred from the side area of the channel in the longitudinal direction to the rib area in the diagonal direction