某汽车在可靠性道路试验中，前桥横置板簧发生了断裂。通过宏观分析、微观分析、化学成分分析、硬度测试、金相检验等方法，对板簧的断裂原因进行了分析。结果表明：板簧表面存在由喷丸工艺不当引起的微小折叠缺陷，折叠部位存在应力集中，为疲劳裂纹萌生创造了条件，在可靠性道路试验时，板簧处于反复交变弯曲载荷作用下，裂纹不断扩展，最终导致板簧发生了疲劳断裂。

In the reliability road test of an automobile, the transverse leaf spring of front axle broke. By means of macro analysis, micro analysis, chemical composition analysis, hardness test and metallographic examination, the fracture causes of the leaf spring were analyzed. The results show that there was a small folding defect on the surface of the leaf spring caused by improper shot peening process, and there was a stress concentration in the folding part, which created condition for fatigue cracks initiation. In reliability road test, the leaf spring was subjected to repeated alternating bending loads, and the cracks continued to expanded, which eventually led to the fatigue fracture of the leaf spring.