X.C. Zhang

Vehicle crash accident reconstruction based on the analysis 3D deformation of the auto-body

The objective of vehicle crash accident reconstruction is to investigate the pre-impact velocity. Elastic-plastic deformation of the vehicle and the collision objects are the important information produced during vehicle crash accidents, and the information can be fully utilized based on the finite element method (FEM), which has been widely used as simulation tools for crashworthiness analyses and structural optimization design. However, the FEM is not becoming popular in accident reconstruction because it needs lots of crash simulation cycles and the FE models are getting bigger, which increases the simulation time and cost. The use of neural networks as global approximation tool in accident reconstruction is here investigated. Neural networks are used to map the relation between the initial crash parameter and deformation, which can reduce the simulation cycles apparently. The inputs and outputs of the artificial neural networks (ANN) for the training process are obtained by explicit finite element analyses performed by LS-DYNA. The procedure is applied to a typical traffic accident as a validation. The deformation of the key points on the frontal longitudinal beam and the mudguard could be measured according to the simulation results. These results could be used to train the neural networks adapted back-propagation learning rule. The pre-impact velocity could be got by the trained neural networks, which can provide a scientific foundation for accident judgments and can be used for vehicle accidents without tire marks.

Architecture of collaborative design grid and its application based on LAN

Abstract To solve the resource sharing problems in collaborative design, computer supported collaborative design (CSCD) technology and grid technology are integrated. The application of grid technology in collaborative design is presented. Concept of collaborative design grid (CDG) is put forward for product design and simulation, and its corresponding architecture is set up based on grid middleware. Task management and resource management in the grid environment are discussed. Grid services are realized based on globus toolkit 3.0. Grid portal of the CDG based on web is developed, and advanced graphical interfaces are provided for potential users. A prototype test bed is established via a case study of a sightseeing lift. It validates the resource sharing and cooperative work through customizing design and parameterized analysis in the CDG. Finally, the performance of the CDG test bed is analyzed and concluded.

Analytical modeling of edge effects on the residual stresses within the film/substrate systems. I. Interfacial stresses

Several analytical models have been developed to derive the closed-form solutions for the residual stresses at the interface when a film was overlaid on a substrate. In these models, the film edge effects on the interfacial stresses were analyzed. However, some of the existing models do not yield good results, and sometimes, they err in a fundamental manner in the prediction of the interfacial stress distribution. In this paper, an analytical model is developed to derive the closed-form solutions for the interfacial stress distributions along the film width. Compared to the existing analytical models, the present model is more rigorous and the analytical results agree better with the finite element results.

Residual stress relaxation in the film/substrate system due to creep deformation

An analytical model is developed to estimate the effect of creep deformation on the stress relaxation and distribution in the film/substrate bilayer structure during prolonged exposure to high temperature. In the model, either the film or the substrate subjecting to high-temperature creep is considered. Closed-form solutions for the residual stresses in the film and the substrate are derived. A relationship between the stress relaxation rate in the film/substrate system and the relaxation time is obtained. Case studies show that the ratios of the biaxial modulus and the thickness of the film to those of the substrate, the creep parameters, and the exposure temperature have significant influence on the residual stress relaxation rate.