基于弯矩等效的装载机外载荷当量与载荷谱编制

External load equivalent and load spectrum compilation of loader based on moment equivalent

为了编制装载机工作装置载荷谱进行结构疲劳性能研究,提出了一种基于动臂截面弯矩等效的装载机外载荷当量方法,将装载机铲装物料时所受外载荷简化为一个作用在铲斗上的集中载荷并进行载荷谱编制。以动臂前后两端铰点连线为基准构建动臂局部坐标系,将铲斗铰点实测载荷转化为局部坐标系下动臂铰点载荷,研究铲掘姿态下动臂截面弯矩和装载机外载荷的同步对应关系,确定了外载荷作用点位置和作用方向,利用动臂最大弯矩截面的弯矩等效建立了装载机外载荷的当量数学模型。由实测的铲斗铰点载荷时间历程和装载机外载荷当量模型得到ZL50G装载机当量外载荷的时间历程,采用雨流计数得到典型作业介质下当量外载荷均值、幅值、频次的统计特性,编制多工况合成的工作装置疲劳试验程序载荷谱。结果表明:基于动臂截面弯矩等效方法能够获取固定姿态下装载机当量外载荷作用位置和作用方向;利用动臂最大弯矩截面的弯矩得到当量载荷时间历程,且在当量载荷与实测载荷下动臂截面弯矩变化规律和大小保持一致;当量载荷均值服从正态分布、幅值服从三参数威布尔分布,利用雨流计数和参数外推法编制的适用于工作装置疲劳试验的变均值加速加载程序载荷谱,缩短了疲劳台架试验的加载时间。提出的基于动臂截面弯矩等效的装载机外载荷当量模型以及载荷谱编制方法,可为装载机工作装置疲劳寿命评估和台架试验规范的制定提供依据。

To study the fatigue performance of the load spectrum of loader working device, an equivalent method of loader external load based on the bending moment section was suggested. When the loader loads the material, the load on the working device was simplified as a concentrated external load acting on the bucket and compiled the load spectrum. A boom coordinate system was constructed based on a hinge line at the front and rear ends of the moving arm, and the actual load of the bucket hinge point was transformed into a hinge load on the boom structure under the boom coordinate system. The synchronous relationship between the moment of the boom section and the external load of the working device was studied, and the action point position and direction of the external force was determined. The external load equivalent model of the working device based on the bending moment of the maximum bending moment section of the boom was established. Considering the load equivalent load of the bucket hinge point under typical working condition of the ZL50G loader working device as the basis, the statistical characteristics of mean load, frequency, and amplitude were obtained by rain flow counting. The load spectrum of the fatigue test program under various working conditions was determined. The results show that the position and direction of the equivalent external load on the working device can be accurately obtained based on the bending moment section equivalent method. The time history of the equivalent load is obtained by the bending moment section of the maximum bending moment section of the boom, and the value and change rule of the boom bending moment section are coincident under the conditions of equivalent load and measured load. The mean of the equivalent load is fit to the normal distribution and the amplitude is fit to the three-parameter Weibull distribution. The variable mean load spectrum for the fatigue test of the working equipment of the loader is compiled using rain flow counting and parameter extrapolation, and the loading time of the fatigue bench test is minimized. The proposed equivalent load model based on the bending moment section equivalent and the proposed method of compiling the load spectrum of the loader working device provide basis for the accurate evaluation of structural reliability and establishment of scientific indoor bench test specifications. 7 tabs, 9 figs, 19 refs.