楔形螺纹连接扭拉关系理论分析及拧紧特性

Theoretical Analysis on Torque-tension Relationship and Tightening Characteristics of Wedge Threaded Connection

楔形锁紧螺母是一种应用广泛的防松结构,但是当前关于楔形螺纹连接的扭拉关系理论分析和拧紧特性因素分析的研究成果匮乏,导致楔形锁紧螺母的安装工艺一直缺少理论指导。首次建立并验证了楔形锁紧螺母拧紧过程的扭拉关系理论公式,并对其拧紧特性进行了影响因素分析。首先考虑楔形螺纹面的复杂几何形状,构建楔形斜面上任意区域的局部坐标系,通过坐标转换获得了任意楔形区域的平面方程、切向和法向矢量,在此基础上建立楔形锁紧螺母拧紧过程的扭拉关系理论公式;然后建立精确的楔形螺纹连接有限元模型,仿真了实际的拧紧过程,通过改变不同的摩擦系数、楔形角和螺距,得到拧紧扭矩-预紧力的离散数据点,通过对比理论公式所绘制的扭拉关系直线,从数值仿真角度验证了楔形螺纹连接扭拉关系理论公式的可靠性;同时,采用航空航天领域的两种典型楔形锁紧螺母作为试验对象,通过拧紧试验进一步验证理论公式的可靠性。最后系统研究了螺栓螺母材料、被压件材料、螺纹规格、螺母结构形式、拧紧次数等因素对楔形锁紧螺母扭矩系数和重复拧紧性能的影响规律。

Wedge self-locking nut is a widely used anti-loosening structure. However, currently, there is a lack of theoretical analysis on the torsion-tension relationship and tightening characteristics of wedge threaded connection, which leads to the lack of theoretical guidance on the installation of wedge self-locking nut. The theoretical formula of torsion-tension relationship during the tightening process of wedge self-locking nut is established and verified for the first time, and the influencing factors of the tightening characteristics of wedge threaded connection are analyzed. First, the complex geometry of the wedge threaded surface is considered,the local coordinate system of any region on the wedge thread surface is constructed, and the plane equation, tangential vector and normal vector of any wedge area are obtained by coordinate transformation. On this basis, the theoretical formula of the torsion-tension relationship of wedge self-locking nut is established. Second, the accurate finite element model of wedge threaded connection is established and the actual tightening process is simulated. The different discrete data points of torque-tension are obtained by changing different friction coefficients, wedge angles and pitches. These data points of torque-tension are then compared with the relationship curve of torque-tension described by the theoretical formula, based on which the reliability of the theoretical formula of torque-preload is verified. At the same time, two typical wedge self-locking nuts in aerospace field are used as test objects,and the reliability of the theoretical formula is further verified by tightening experiment. Finally, the influences of the material of bolt and nut, the material of joint, the thread specification, the structural form of nut and the number of tightening times on the torque coefficient and the repeated tightening performance of the wedge self-locking nut are studied systematically.