A Method for Evaluating the Formability of Tailor Rolled Blank (TRB) by Means of the Forming Limit Margin Field Graph in Forming Process

Tailor rolled blank (TRB) with graded thickness has shown great potential in the automobile field. Using traditional forming limit diagrams (FLDs) to evaluate TRB formability is challenging due to thickness variations. In this paper, a 3D forming limit surface (FLS) considering the influence of thickness was obtained. A numerical model was developed to predict final strains. Moreover, a forming margin was denoted and calculated to generate the forming limit margin field graph for quantitative evaluation of the TRB formability. Results showed that as the punch travel increased, the forming margin value decreased. As the travel changed from 35.2 mm to 37.4 mm, the corresponding forming margin value changed from 0.002 to -0.024. The formability declined, and the specimen eventually cracked on the thinner side. Besides, the deformation and strain paths predicted by simulation agreed well with those measured from formed part, which indicated that the final strains used in formability evaluation were reliable. The method was suitable for quantitative evaluation of the formability and predicting the cracking position in TRB forming.

Crashworthiness analysis and optimization of different configurations multi-layered corrugated sandwich panels under crush loading

Multi-layered corrugated sandwich panels can be made up of different core shapes, different arrangements, the variable height, and variable thickness in every layer. In this paper, the crashworthiness behaviors of multi-layered corrugated sandwich panels with different configurations, which are controlled by these four factors, are analyzed and compared. The optimal configuration is found by adopting orthogonal experimental design and range analysis method. A novel multi-layered corrugated sandwich structure with functionally graded thickness is proposed and studied and is proved to better structural crashworthiness. First, finite element models of multi-layered corrugated sandwich panels are established and validated by experiment. Then, the effect of the four factors with three levels on crashworthiness is analyzed, and we obtain the main factor and the optimal configuration with the maximum specific energy absorption by using orthogonal experimental design and range analysis method. Finally, parametric studies and multi-objectives optimization of the proposed novel multi-layered corrugated sandwich structure with functionally graded thickness are conducted. The optimization is aimed at maximizing the specific energy absorption and minimizing the initial peak force under crush loading, based on the non-dominated sorting genetic algorithm and response surface method technique. These findings can provide valuable guidelines for the design of multi-layered corrugated sandwich panels with different configurations under crush loading.

THIN-WALLED STEEL TUBULAR COLUMNS WITH UNIFORM AND GRADED THICKNESS UNDER CYCLIC LOADING

Thin-walled steel tubular circular columns are widely used as cantilever bridge piers due to their geometric efficiency, aesthetic appearance, and high earthquake resistance. However, local buckling, global buckling, or interaction between both is usually the main reason of significant strength and ductility loss in these columns, which eventually leads to their collapse. This paper investigates the behavior of uniform circular (C) and graded-thickness circular (GC) thin-walled steel tubular columns under constant axial and cyclic lateral loading. The GC column with size and volume of material equivalent to the C column is introduced and analyzed under constant axial and cyclic lateral loading. The analysis carried out using a finite-element model (FEM), which considers both material and geometric nonlinearities. The accuracy of the employed FEM is validated based on the experimental results available in the literature. The results revealed that, significant improvements in strength, ductility, and post-buckling behavior of thin-walled steel columns obtained using the GC column.