朱晓卉

（青岛船舶检验局,山东 青岛 266071）

摘要：装备在某船型上的TBD620V12型柴油机摇臂座固定螺栓由于受到高频交变应力冲击的影响，多次出现螺栓断裂事故，严重影响柴油机的安全运行。本研究采用强度和金相分析、形位及表面精度检测以及可靠性校核等方法对其进行分析研究，发现螺栓选型不当以及紧固方法不合理是螺栓断裂的主要原因；提出改用性能等级为12.9、硬度为HRC39-44的新螺栓；螺栓紧固时，预紧30N·m,然后再拧紧100°。经过改进后,该船没有再发生同样事故,说明研究方法合理，处理方法正确，提出的改进措施也具有一定的推广意义。

关键词：柴油机；螺栓；断裂；可靠性；预紧力

Abstract：Rocker seat fixing bolt is a mechanical part of gas exchange system of TBD620V12 diesel engines. Due to the impact of high frequency alternating stress, the bolt fracture accidents occurred repeatedly in ships equipped with the diesel engines, which seriously affected the safe operation of diesel engines. In this paper, the strength and metallographic analysis, shape and surface accuracy detection and reliability checking methods were induced to study the reasons of bolt facture. The results show that the bolt model was unreasonable and fastening method was inappropriate. A new type bolt with performance level of 12.9,HRC39-44 hardness was proposed to replace the existing ones. A new preload moment of 30N·m and rotation angle of 100°of bolts were determined. After the improvement, the accident was eliminated, indicating that the research method was reasonable and the results were correct. The proposed improvement measures also have some significance.

Key words：Diesel engine；bolt；fracture； reliability；preload