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Aiming to reveal the changing law of modeling accuracy of grey Verhulst model resulted from the small perturbation of primitive sequence, we took the spectrum condition number of matrix as a tool of measuring the morbidity of this model and analyzed the value of conditions of coefficient matrix. The research result shows that only when the first data point of original data sequence be a constant (constant >0) and the rest of data points be all 0, this model will appear to be a serious morbid problem, however, at this time, it is meaningless to build a grey Verhulst model by using a raw data sequence with an inherent law for prediction. The research conclusion suggests that grey Verhulst model has no morbidity. [ABSTRACT FROM AUTHOR]

In view of the uncertainties in .material and manufacturing process, and for enhancing the efficiency of robustness analysis on vehicle crashworthiness, a robustness analysis scheme based on kriging metamodel is adopted to investigate the effects of material uncertainty on the crashworthiness of the front side rail in a car. The results demonstrate that the material uncertainty highly affects the peak crash force of front side rail, and the accuracy and efficiency of robustness analysis using kriging metamodel are higher than that with FE model. [ABSTRACT FROM AUTHOR]

Existing studies on the grinding mechanism of ingle-scratch method cannot reflect the interaction between multiple scratches Educed by the random distribution of multiple abrasive grains. In order to exudate the effect of the metrication of multiple scratches on the material removal mechanism during the grinding process of smile-crystal germanium, multiple-scratch experiments were carried out on single-crystal germanium with different scratching forces using a Cube dents. Combining the geometry of the Cube indenter and the elastic recovery of the scribed surface, a scratch hardness model was established, and the scratch depth, stress field, elastic recovery, scratch hardness, and friction characteristics n the second scratching were analyzed to investigate the effect of the load change during the first scratching on the subsequent scratching. The results show that the critical load, critical depth, plastic recovery rate and scratch hardness of the brittle-plastic translation of single-crystal germanrnm n the second scratching decrease why the increase of the first scratching load; the accuracy of the power function tit to the tangential and normal forces and the depth of scratching decreases; and the maximum principal stress increases, which results n the continuous expansion of cracks and ultimately causes brittle fracture of the material. [ABSTRACT FROM AUTHOR]

A procedure of forward concept design of car body for frontal crash is proposed. First of all, topology optimization is conducted on the original styling surface of a car to get a better topology structure, with its effectiveness quickly verified by a simplified beam element model built. Then size optimization is performed for quasi-static loading conditions, and the initial dimensions of the main components of car body are obtained as the basis of frontal crash simulation. Finally, with a rectangular thin-walled straight beam as the objective of study, crashworthiness concept design for frontal impact is carried out with an equivalent beam element model. As a result, the preliminary dimension of car body is determined as the base of detailed structural design. The results show that the procedure is feasible and easy to implement, being able to lay a foundation for car body to achieve all expected performances. [ABSTRACT FROM AUTHOR]

For obtaining a rational load bearing structure of electric car body in conceptual design phase, a multi-objective topology optimization is performed with consideration of both static and dynamic characteristics. Based on solid isotropic material with punishment (SIMP) theory, the objective functions for multi-static-conditions and dynamic vibration frequency are defined by compromise programming and average frequency methods respectively and are normalized to eliminate the discrepancy in the order of magnitude. The optimality criteria method is. used to update design variables, and a topological structure of electric car body meeting both requirements of static stiffness and dynamic vibration frequency is finally obtained by optimization iteration. [ABSTRACT FROM AUTHOR]