基于熵权-Topsis的车体动应力时域外推方法

Time-Domain Extrapolation of Dynamic Stresses in Car Body Based on Entropy Weight-Topsis

摘要

为了对车辆进行结构疲劳分析，有必要将短时间所测得的动应力时域信号利用外推技术外推成更长时间的历程。以某型机车车体的部分测点为例，提出了基于熵权法和Topsis方法确定最优阈值的方法。首先，将初始时域信号进行去零漂等前处理后，采用熵权法对超阈值（POT）模型阈值评价指标进行权重分配；其次，采用多指标的Topsis方法进行综合评价，对比相对接近度获得最优阈值。对峰谷值超出量进行广义帕累托（Pareto）分布参数拟合，进行极值重构并替换原始样本，最终得到外推后的样本。从P-P图、Q-Q图可以看到，峰谷值样本拟合效果较好；从累积分布图可以看到，外推5倍和10倍后的样本极值变大，且曲线与实际样本曲线接近。对外推后的时域信号进行损伤计算后发现，疲劳寿命评估方法更偏于安全。

Abstract

In order to perform structural fatigue analyses of vehicles, it is necessary to extrapolate the time-domain signals of dynamic stresses measured over a short period of time into a longer history using extrapolation techniques. Taking some measurement points of a certain locomotive body as an example, a method to determine the optimal threshold based on the entropy weight method and the Topsis method is proposed. Firstly, after the initial time-domain signal is pre-processed by de-zero drifting and other pre-processing, the entropy weighting method is used to assign weights to the threshold evaluation indexes of the peak-over-threshold (POT) model; secondly, the Topsis method of multiple indexes is used to conduct a comprehensive evaluation, and the optimal threshold is obtained by comparing the relative proximity. The parameters of generalized Pareto distribution were fitted to the excess of peak and valley values, and the extreme value was reconstructed and replaced the original samples to finally obtain the extrapolated samples. From the P-P and Q-Q plots, it can be seen that the peak and valley samples are fitted better; from the cumulative distribution plot, it can be seen that the extreme value of the sample after extrapolation by a factor of 5 and 10 becomes larger, and the curve is close to the actual sample curve. After the damage calculation of the time-domain signal after extrapolation, it is found that the fatigue life assessment method is more biased towards safety.

关键词

时域外推 / 超阈值 / GPD拟合 / 损伤计算

Key words

time domain extrapolation / POT / GPD fitting / damage calculation

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基金资助

江西省自然科学基金优青项目(20252BAC210001)

国家自然科学基金青年项目(52202468)

江西省研究生创新专项基金项目(YC2024-S422)