乔云杰，周逢春，吕磊，韩毅

（常州南车柴油机零部件有限公司，江苏常州 213011）

    摘要：介绍了机车及船用中速柴油机组合活塞的连接方式以及螺栓的预紧方法；对比分析了常用螺栓拧紧方法的精度；着重介绍了螺栓扭紧扭矩与预紧力之间的关系，列举了不同规格螺栓的扭矩系数；通过预紧对比试验，详细分析了螺栓预紧过程中显著因素对扭矩系数的影响；根据目前国内螺栓连接的现状，提出了避免螺栓连接失效的参考意见。

    关键词：组合活塞；螺栓；扭矩；预紧力；伸长量

    Abstract: The joint types and bolt initial tightening methods of composite piston which used in engine and marine medium-speed diesel was introduced; and the precision of different bolt tightening methods was compared; and the relationship between bolt toque and tightening force was focused on, torque coefficients for different bolts was listed; different initial tightening methods was tested, and the process which notable factors impacted the torque coefficients was analyzed; based on the domestic present situation in bolt joint, the advisory opinion used for  avoiding bolt failure was proposed.

    Key words: composite piston; bolts; torque; initial tightening force; elongation