Punching with a slant angle - cutting surface quality

For economic or process-related reasons, punching of structural sheet metal components often has to be used for car bodies. The difference in angle of attack between punch and sheet metal component is referred to as “slant angle”. However, at the current state of the art, no precise information is available on the characteristics of cutting surfaces in relation to the slant angles. For this reason, cost-intensive slider units are used for comparatively small slant angles of around 10° in order to ensure series suitability of corresponding punching processes. In this respect, recent studies performed by the authors have shown that good cutting surface qualities can also be achieved for slant angles distinctly beyond 10°. This contribution presents an empirical test series for the characterization of cutting surface parameters when punching with a slant angle. Here, the experimental cutting surface analysis showed an asymmetric characteristic of the cutting surface along the hole circumference. Furthermore, the investigated sheet metal materials HC340LA, DP600 and DP800 revealed recurring tendencies regarding the parameters “edge draw-in”, “clean cut”, “fracture surface” and “burr height”, which had been combined to corresponding three-dimensional regression models. With these regression models, cutting simulations could be calibrated, allowing a quality prognosis of cutting surfaces achievable when punching at specific slant angles.

GMAW Welding of MPM Sheets in Active Gas

MPM sheets represent the sanwich panels consisted of two low carbon steel sheets 3 mm thick separated by a visco-elastic inner layer. It is used for dampening the structure borne sound and it replaces the structural sheet metal without taking up a considerable amount of space. The inner layer, however, makes the welding more difficult, since it burns when exposed to relatively high welding temperatures. This may cause distorsion and separation of sheet metal, as well as the loss in sound dampening properties. Therefore, it is of utmost importance that the visco-elastic inner layer remains intact as much as possible, while still maintaining a low cost and a high productivity during welding of MPM sheet housing of large industrial electric motors and generators. In this paper, gas metal arc welding (GMAW) with CO2 active gas was used in an attempt to produce suitable butt welds, welded from both sides. To prevent distorsion and burning of inner layer different butt welds were tested. Different combinations of the following welds were tested: open square weld, combined open square weld on one sheet and single V on the other side, welding in one pass on each side and welding in multiple bead segments on each side. It was found that in all cases, a full penetration was achieved. Furthermore, inner layer thickness near the weld and potential distorsion strongly depend on the welding methodology used.

Design and Optimization of an SMA-Based Self-Folding Structural Sheet With Sparse Insulating Layers

Origami inspired structures possess attractive characteristics such as the potential to be reconfigurable and the capability to be folded into compact forms for storage. Self-folding structures, which are systems able to perform folding operations without external mechanical input, are desirable in certain circumstances such as remote applications (e.g., space applications, underwater robotics). A self-folding structural sheet consisting of two outer layers of shape memory alloy (SMA) orthogonal wire meshes separated by an inner insulating layer is considered in this work. The inner layer consists of ABS plastic columns that connect the SMA wire mesh intersections of the top and bottom layers, which are co-located and co-oriented (denoted sparse middle layer/aligned meshes design). Significant reduction on the heat transfer between the SMA layers is expected in this design compared to previously considered designs with continuous or perforated elastomeric middle layers. The geometric and power input parameters of the sparse middle layer/aligned meshes design are optimized under mechanical and thermal constraints considering finite element and reduced order analytical models. The optimal folding performance of the sparse middle layer/aligned meshes design is compared to that of the previous designs. The results show that the sparse middle layer/aligned meshes design has promising characteristics as a self-folding structural sheet and provides for tighter folds compared to the designs with elastomeric middle layers.

Study on Structural Lightweight Design of Automotive Front Side Rail Based on Response Surface Method

Nowadays, vehicle lightweight design is a main topic in automotive industry. Crashworthiness, which is the most important performance of a full vehicle, must be always satisfied in the study on body lightweight design. This paper presents research, from the point of view of safety, of structural lightweight design of the front side rail of a passenger car. The response surface method is used to create mathematical models that represent the relationship between structural sheet thicknesses and absorbed energy of the entire structure in the frontal crash simulation, and the relationship between structural sheet thicknesses and the mass of the entire structure. Then an optimization process is performed, and the structural mass and original absorbed energy are defined as objective and constraint functions, respectively. Minimum mass and structural sheet thicknesses are obtained with the satisfaction of original absorbed energy of the front side rail structure. The weight reduction of the front side rail is 26.95%.