基于非参数雨流外推法的车架载荷谱与疲劳寿命分析

Load spectrum and fatigue life analysis of frame based on non-parametric rainflow extrapolation method

针对农用机械工况复杂,受力多变,对结构件寿命影响很大的问题,以蔬菜田间作业动力机械车架为研究对象,对车架载荷谱及疲劳寿命情况进行研究。采用有限元分析方法,对车架进行应力分析并选取测点;采取建立由应变片、应变调理仪、信号采集仪等组成的应力载荷测试系统进行载荷测试试验,测得犁地和路面行驶2种典型工况下应力时间历程;拟用傅里叶变换频率检验和离散自函数平稳性分析方法,确定信号符合随机载荷信号特征;采用数据处理方法消除信号干扰因素。对测得应力载荷数据进行非参数雨流外推,基于外推结果编制车架应力载荷谱并进行疲劳寿命预测研究。结果表明:损伤值最大的测点寿命预估结果为1.043×1013 h,满足使用要求,该方法适用于农业机械结构载荷谱编制及疲劳寿命预测,可为农业机械结构载荷谱编制及疲劳寿命预估提供参考。

Aiming at the problem of complex working condition of farm machinery,variable stress and great influence on the life of structural parts,the load spectrum and fatigue life of the frame of vegetable tool carrier were studied.The stress of the frame was analyzed by finite element method and the measuring points were selected.The load test was carried out by establishing the stress load test system composed of strain gauge,strain adjuster,signal acquisition device,and the stress time history under two typical working conditions of ploughing and road driving was measured.The Fourier transform frequency test and discrete self-function stationarity analysis method were used to determine that the signal conforms to the signal characteristics of random load.Data processing method was adopted to eliminate signal interference factors.Non-parametric rain flow extrapolation was carried out for the measured stress load data.Based on the extrapolation results,the stress load spectrum of the frame was compiled and the fatigue life prediction research was conducted.The results showed that the estimated life of the measuring point 5 with the maximum damage value was 1.043×1013 hours,which met the requirements of service and use.This study provided references for the establishment of load spectrum of agricultural machinery structure and the estimation of fatigue life.