Studying and optimizing the effects of different design options on the performance of crash absorbers with diaphragms

Crash absorbers are structures that are used to ensure passenger safety by absorbing the energy generated during vehicular accidents through controlled plastic deformation. These structures are commonly used in front and rear ends of trains and automobiles. In this study, the performance of a crash absorber with diaphragms was improved through various design changes. These changes include changing the outer wall and diaphragm thickness of the crash absorber, changing the diaphragm placement and changing the crash absorber geometry by defining a taper angle. In optimization problems, initial peak crash force (IPCF) was minimized, and specific energy absorption (SEA) was maximized as objective functions. Crash analyzes were done using finite element method. The finite element model was created and validated based on another study in the literature. Finite element analyzes were performed using LS-DYNA finite element software package. Optimization problems were solved with a surrogate model based optimization approach. In each optimization problem, sampling points were created using the validated finite element model, and surrogate models were created using all surrogate model methods mentioned above over the created sampling points. The accuracies of these surrogate models were measured with test points created separately for each optimization model using the validated finite element model. Optimum design variables were obtained for all surrogate models and the optimum results were verified with the finite element model. The best result obtained from these finite element analysis results was determined as the optimum result of the study. As a result of the studies, the specific energy absorption (SEA) was increased by 69.4% and the initial peak crushing force (IPCF) was reduced by 24.7%. Optimal tube and diaphragm dimensioning resulted in 59.2% increase, optimum diaphragm placement resulted in 7.7% more increase, and tapering resulted 2.5% further increase in SEA. Similarly, optimal tube and diaphragm dimensioning resulted in 23.4% reduction, optimum diaphragm placement resulted in 1.3% further reduction in IPCF, whereas optimizing taper angle did not result in an extra IPCF reduction.