| Design for Quality |
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| Failure analysis and test specification development of mudguard assembly of commercial vehicles |
| ZHANG Zong-yang1,2, WANG Kai1, SUN Lei1, ZHANG Hai-ming3, LIU Zhan-qiang2 |
1.Technical Center, China National Heavy Duty Truck Group Co., Ltd.,Jinan 250101,China
2.School of Mechanical Engineering, Shandong University,Jinan 250061,China
3.JIER Machine-Tool Group Co., Ltd.,Jinan 250022,China |
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Abstract Aiming at the problems that the failure reason is not easy to obtain and the release is not easy to control for the mudguard assembly of commercial vehicles, a fatigue failure solution for a single degree-of-freedom vibration system based on the measured load spectrum is proposed. Firstly, the failure mode, fracture morphology and road load spectrum of a commercial vehicle mudguard assembly were analyzed, and the failure type and system model were determined. Through the data analysis, the mudguard assembly was simplified into a single degree-of-freedom vibration system, and its equivalent stiffness was the series stiffness of the fixed bolt and mudguard bracket. Then, theZ-direction acceleration power spectral density （PSD） at the frame （the installation position of the mudguard assembly） and the end of the mudguard bracket, and the frequency response function and the coherence coefficient between them were analyzed, and the working mode of mudguard assembly was obtained. Finally, in order to improve the quality of mudguard assembly, an endurance test specification for mudguard assembly was developed based on shock response spectrum (SRS) and fatigue damage spectrum (FDS). The results showed that when the frequency was 22.0 Hz, the response of the mudguard assembly was the largest, and theZ-direction accelecation power spectral density of the frame was lower, and the coherence coefficient betweem them was only 0.6, which indicated that the failure of mudguard assembly was mainly due to its own excitated mode. While the main working mode of mudguard assembly was the third-order mode (f = 22.26 Hz), its vibration shape was anti-phase swing up and down, which was consistent with the test result. The failure mode of mudguard assembly was reproduced scientifically by bench test based on mudguard assembly endurance test specification, and the rationality of test specification was verified. Follow-up tests show that the failure rate of the improved mudguard assembly is greatly reduced and the after-sales feedback is good. The research indicates that the solution can significantly shorten the development cycle of new products, and realize the rapid release of improved products and subsequent new products.
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Received: 29 September 2019
Published: 28 February 2020
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商用车挡泥板总成失效分析与试验规范制定
针对商用车挡泥板总成失效原因不易获取、释放不易控制等问题，提出了一种基于实测载荷谱的单自由度振动系统疲劳失效解决方案。首先，分析了某商用车挡泥板总成的失效模式、断口形貌和道路载荷谱，确定了其失效类型和系统模型，通过数据分析得到该挡泥板总成可简化为单自由度振动系统，其等效刚度为固定螺栓和挡泥板支架的串联刚度。然后，分析了车架（挡泥板总成安装位置）和挡泥板支架尾端处Z向加速度功率谱密度(power spectral density，PSD)以及两者之间的频响函数和相干系数，得到了挡泥板总成的工作模态。最后，为提升挡泥板总成的质量，基于冲击响应谱（shock response spectrum, SRS）和疲劳损伤谱（fatigue damage spectrum, FDS）制定了挡泥板总成耐久试验规范。结果表明：当频率f =22.0 Hz时，挡泥板总成的响应最大，车架的Z向加速度功率谱密度较小，且两者之间的相干系数仅为0.6，说明挡泥板总成失效主要是因为其自身的某阶模态被激励；当挡泥板总成的主要工作模态为第3阶模态（f=22.26 Hz）时，其振型为反相位上下摆动，与测试结果相符；基于挡泥板总成耐久试验规范的台架试验科学地复现了挡泥板总成的失效模式，验证了试验规范的合理性。后续试验跟踪显示，改进后挡泥板总成的失效率大幅降低，售后反馈良好。研究表明该解决方案可大幅缩短新产品的开发周期，实现了改进产品和后续新产品的快速释放。
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