Equivalent loading method for the thin-walled floors of armored vehicles with bottom explosion impacts

The high cost and low efficiency of full-scale vehicle experiments and numerical simulations limit the efficient development of armored vehicle occupant protection systems. The floor-occupant-seat local simulation model provides an alternative solution for quickly evaluating the performance of occupant protection systems. However, the error and rationality of the loading of the thin-walled floor in the local model cannot be ignored. This study proposed an equivalent loading method for the local model, which includes two parts: the dimensionality reduction method for acceleration matrix and the joint optimization framework for equivalent node coordinates. In the dimensionality reduction method, the dimension of the acceleration matrix was reduced based on the improved kernel principal component analysis (KPCA), and a dynamic variable bandwidth was introduced to address the limitation of failing to effectively measure the similarity between acceleration data in conventional KPCA. In addition, a least squares problem with forced displacement constraints was constructed to solve the correction matrix, thereby achieving the scale restoration process of the principal component acceleration matrix. The joint optimization framework for coordinates consists of the error assessment of response time histories (EARTH) and Bayesian optimization. In this framework, the local loading error of the equivalent acceleration matrix is taken as the Bayesian optimization objective, which is quantified and scored by EARTH. The expected improvement acquisition function was used to select the new set of the equivalent acceleration node coordinates for the self-updating optimization of the observation dataset and Gaussian process surrogate model. We reduced the dimension of the acceleration matrix from 2256 to 7, while retaining 91% of the information features. The comprehensive error score of occupant's lower limb response in the local model increased from 58.5% to 80.4%. The proposed equivalent loading method provides a solution for the rapid and reliable development of occupant protection systems.