拧螺栓和拧螺母对螺纹轴向预紧力的影响研究

Study on the influence of screwing bolts and nuts onthread axial preload

为了研究拧螺栓和拧螺母对轴向预紧力的影响,基于被连接件材料为钢-钢、钢-铝连接结构,将六角法兰面螺栓和六角法兰面螺母分别压钢状态进行拧紧试验,并利用超声波预紧力测量仪监测拧紧实现的轴向预紧力,结果表明拧螺栓较拧螺母实现的预紧力大。经分析导致该现象主要原因为螺栓法兰面实际锥度比螺母法兰面锥度小,即螺栓法兰面较螺母内外圈高度差小,导致前者支承面摩擦内径更小,同目标扭矩条件下扭矩系数小则转化的轴向预紧力更大。结合有限元分析,验证实测样件法兰面不同锥度受载条件下的应力分布情况,钢板最大应力集中位置为支承面摩擦内径,与试验结果相吻合。

In order to study the influence of bolts and nuts on the axial preload,on the basis of steel-steel and steel-aluminium joints,the hexagonal flange bolts and hexagonal flange nuts were pressed into steel separately. At the same time,the ultrasonic preload tester was used to monitor the axial preload achieved by tightening. The results show that the preload achieved by the bolts is larger. After analysis,the main reason is that the actual taper of the bolt flange surface is smaller than that of the nut flange surface,that is,the height difference between the bolt flange surface and the nut inner ring is smaller,which leads to smaller friction inner diameter of the bolt support surface,and smaller torque coefficient under the same torque condition,which leads to greater axial preload. Combined with the finite element analysis,the stress distribution of the flange surface under different taper loads is verified. The maximum stress concentration position of the steel plate is the friction inner diameter of the supporting surface,which is consistent with the experimental results.