室温下C/SiC复合材料螺纹紧固件的拧紧特性

探讨了C/SiC陶瓷基复合材料螺纹紧固件在室温下的拧紧特性。试验测试了紧固件在拧紧和拧松过程中, 力矩与预紧力两者的对应关系, 记录了预紧力在短时、 长时内的减小比率, 并用显微镜观察了螺纹面的磨损情况。另外, 分析了材料非线性拉伸行为对拧紧状态所造成的影响。结果表明: 拧紧、 拧松力矩与预紧力之间近似呈线性关系, 螺纹面和支承面的平均摩擦系数分别为0.52和0.46; 随拧紧力矩增大, 螺纹面产生一定程度磨损, 螺纹之间的相互嵌入作用减弱, 因此预紧力在拧紧后的降幅减小, 稳定性提高; 对螺栓进行适当的预拉伸处理, 提高材料的弹性极限后, 可提高紧固件的抗松弛能力。

Tightening characteristic of C/SiC composite threaded fasteners at room temperature

The tightening characteristic of threaded fasteners made of C/SiC ceramic matrix composite at room temperature was investigated.Through experiment the relationship between torque and clamping force was measured during tightening and loosening process,meanwhile,the loss rate of clamping force in short or long time was recorded and the condition of wear on the thread surface was observed using microscope.In addition,the effect of material’s nonlinear tensile behavior on the tightening state was also analyzed.The results indicate that there is an approximately linear relationship between clamping force and tightening or loosening torque,and the average friction coefficients of thread and bearing surfaces are 0.52 and 0.46,respectively.As the tightening torque increasing,some wear abrasion occurs on the thread surfaces which,however,will weaken the effect of embedment process between engaged threads,and hence reduces the loss rate of clamping force and promotes its stability after assembly.After proper pre-tension treatment on the bolt in order to increase the elastic limit of the material,the anti-loosening capacity of the fastener can be improved.