In this paper, the kinematic characteristic analysis and optimization design of a minivan MacPherson-strut suspension system are performed. Design requirements of a minivan suspension system are described first, and then the design process is presented. A typical MacPherson suspension model of the minivan is conducted. Through the established model, the simulation of parallel wheel travel of the suspension system of the minivan is carried out and analyzed. After initial analysis, wheel alignment parameters especially the toe angle and camber angles need to be optimized to meet the requirements of the desired design value. The characteristic curves of wheel alignment parameters are drawn and the corresponding non-ideal characteristics are found. The optimization objective is to reduce the variation of the unreasonable alignment parameters, and the design variables are given through the sensitivity analysis. The design parameters are reasonably grouped according to different kinematic characteristics, thus, a unified objective function is established by direct weighing combination method. Finally, the established objective function is optimized and designed with neighborhood cultivation genetic algorithm. By comparing the original and optimized results, the better wheel alignment parameters are obtained and the system performances of suspension are further improved.
Thin-walled structures with graded property have been paid more attention in recent years due to their significant balance between lightweight and crashworthiness. However, few studies have been focused on energy absorption capacity of thin-walled conical tubes with graded diameters. In this paper, the thin-walled conical aluminum tubes with nonlinearly-graded diameters are introduced and their corresponding crashing characteristics are performed. The diameters are assumed to nonlinearly vary according to a power-law distribution function primarily determined by a graded exponent n. It is found that the total weight of thin-walled conical tubes decreases with the increasing of the gradient exponent. The energy-absorbed performances such as specific energy absorption, initial peak crashing force, and mean crashing force of those graded tubular structures are numerically analyzed. And then the effects of various geometric parameters such as the gradient exponent, deformation distance, and diameter range on crashing behaviors are further evaluated. It is observed that those parameters especially the gradient exponent has significantly obvious effects on crashworthiness of the proposed nonlinearly graded tubes. It is also noted that the straight conical structure with gradient n = 1.0 may not show the best energy absorption characteristics compared with other gradients. The work could provide valuable information for effective design of thin-walled energy-absorbing structures with variable geometrical parameters.
The electric truck frame as a vital load-bearing component has aroused growing attentions due to its enormous potential in lightweight. However, few systematic studies have been performed on the multi-objective topological design of the frame attributable to its complexity on loading and conflicting objectives. This paper aims to develop a multi-objective topology optimization strategy of the electric truck frame based on the hybrid decision making method combining orthogonal test design (OTD) and analytic hierarchy process (AHP). The hybrid strategy is performed to obtain a new set of weight ratio combination from objective data and subjective judgment. The topological results show that the overall performance of the optimal frame is better than any of the methods applied alone. By comparing, it is found that the strength and stiffness of the optimal frame is higher than that of the original frame from the perspective of static conditions, and the low-order natural frequency of the optimal frame is significantly improved. It demonstrates that the proposed approach could be as an effective tool for multi-objective topology optimization of the electric truck frame in seeking lightweight and comprehensive mechanical performance. The hybrid strategy might be expected to provide some guidance for more complicated engineering problems. INDEX TERMS Electric truck frame, multi-objective design, topology optimization, orthogonal test, analytic hierarchy process.
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