重型车辆转向节臂强化路耐久性断裂试验

为研究某重型车辆在试验场强化耐久路可靠性试验中发生的转向节臂锥体根部断裂问题,从材料组织结构特性和工艺装配精度角度考虑,对转向节臂断裂故障模式进行了详细分析。在断裂口附近粘贴全桥弯曲应变片并布置与转向系统关联的测试传感器,采集断裂部位的弯曲应变、侧向加速度及转向横拉杆位移等试验数据。依据缺口根部循环应力-应变滞回环曲线方程及诺伊贝尔(Neuber)原理,将测试的名义应力载荷转换成断裂部位的局部应力-应变响应,利用曼森-科芬(Manson-Coffin)平均应力修正方程计算断裂位置的疲劳寿命和损伤。分析和计算结果表明,转向节臂材料特性满足设计技术条件,而工艺装配锥度及表面粗糙度不满足图纸设计精度,转向节臂与转向节的装配接触面积只达到30%,导致转向节臂锥体根部产生局部高集中应力,最终发生弯曲低周疲劳断裂。

Durability Fracture Tests for Steering Knuckle Arm of Heavy Truck on Enhancement Roads

In order to research the fracture of cone root of steering knuckle arm occurring at the phase of durability test on the enhancement road of proving ground, and consider the characteristics of material structure and process assembly precision, the fracture model of steering arm is analyzed in detail. The full bridge strain gauge is pasted in the vicinity of fracture and the testing sensor linked to the steering system is equipped, thus the bending strain of the broken portion, lateral acceleration and displacement of steering tie rod and other load data are collected. The hysteresis loop curve equation of cyclic stress-strain and Neuber formula is applied to convert the nominal stress to the local stress-strain cycle response at the fracture location. According to Manson-Coffin equation, impact of mean stress on fatigue damage is corrected. The analysis and calculation results show that the material characteristic of steering arm meets the technical conditions, but the taper and surface finish of steering arm cannot meet the design precision in drawing, the contact area of steering arm and steering knuckle can only reach 30%, local high stress is caused at the steering knuckle and cone root of steering knuckle arm, and bending low cycle fatigue fracture will generate.