某混凝土搅拌车上的U型夹子在使用中发生断裂。采用化学成分分析、宏观检验、力学性能测试及金相检验等方法对断裂U型夹子进行了分析。结果表明：由于螺母未紧到位产生空隙,导致压板位置松动而使U型夹子在使用过程中受到的剪切力增大,加之其显微组织存在缺陷,造成其断裂失效。

Some concrete agitation vehicle U type clip broke in use. By means of chemical composition analysis,macroscopic examination,mechanical property testing and metallographic examination,the failure reason of U type clip was analyzed. The result indicated,because the spring pad tight arriving,has not produced the crevice,the clamp position becomes less crowded,causes the shearing force which the U clip receives to increase,and the microstructure existence flaw,creates the early failure finally.