Abstract: For the problem of front bumper fractured in durability test of a light truck, this paper analyzes the reason of fracture from structural mode, strength and vibration fatigue. Based on the basic principle of vibration fatigue in frequency domain and the definition method of vibration fatigue load, the torsional fatigue simulation analysis model is established and the failure causes are identified. The result shows that the risk area is consistent with the real vehicle. At the same time, the structural optimization is completed for the risk position and passed the durability test, and the analysis method is verified effectiveness, the research results can provide a reference for solving similar problems of the light truck chassis structures.

Key words: Front bumper; Strength analysis; Load spectrum; Vibration fatigue; Torsional vibration condition

摘要： 针对某轻卡前保险杠在耐久试验中出现的开裂问题，文章从结构模态、强度以及振动 疲劳三方面进行原因分析。基于频域振动疲劳的基本原理及振动疲劳载荷定义方法，建立扭 振疲劳仿真分析模型并识别失效原因，结果显示风险区域与实车一致。同时，针对风险位置 完成结构优化并通过实车验证，说明分析方法的有效性，为解决轻卡底盘悬挂结构件类似问 题提供参考。

关键词: 前保险杠；强度分析；载荷谱；振动疲劳；扭振工况