头部支撑面角对连杆螺栓与大头盖接触应力的影响

Influence of the head support surface angle on the contact stressbetween the connecting rod bolt and cap

国标六角法兰面螺栓对螺栓支撑面角度范围提出设计指导,但没有具体指出最佳角度,且其对螺栓预紧力及支撑面应力的影响尚无明确结论。通过建立发动机连杆螺栓的精细拧紧有限元仿真模型,并利用Yamamoto解析法验证了连杆螺栓有限元模型的准确性。研究了螺栓头部支撑面角对拧紧载荷下连杆螺栓预紧力和应力分布的影响,同时通过计算疲劳安全系数对螺栓头部支撑面的结构可靠性进行综合评估。结果表明:螺栓头部支撑面角取0.5°为最佳;提出了带有U型沉割槽的连杆螺栓结构模型,优化后的螺栓结构在螺栓头部与螺杆结合处的平均应力下降16.2%,平均疲劳安全系数提高19.6%。

The national standard hexagonal flange bolt provides design guidance for the angle range of the bolt support surface,but it does not specify which angle is the best,and there is no clear conclusion on its influence on the bolt preload and the stress of the support surface.The finite element simulation model of fine tightening of engine connecting rod bolt is built,and the accuracy of the finite element model of connecting rod bolt is verified by Yamamoto analytical method.The impactof the bolt head support surface angle on the pre-tightening force and stress distribution of the connecting rod bolt under the tightening load is studied.Meanwhile,the structural reliability of the bolt head support surface is thoroughly evaluated by calculating the fatigue safety factor.Ourresults show the bolt head support surface angle of 0.5°is the best.The structure model of connecting rod bolt with U-shaped cutting groove is proposed.The average stress of the optimized bolt structure at the joint of bolt head and screw decreases by 16.2%,and the average fatigue safety factor increases by 19.6%.