中文摘要：

针对某铸铝箱体螺栓联接中预紧力离散度偏高的现状，在紧固件扭转-拉力试验机上进行了螺栓的拧紧试验，分析了拧紧过程中的螺栓使用次数、拧紧速度等工艺过程可控因素对扭矩系数的影响规律。试验结果表明：在螺栓拧紧过程中扭矩系数随着扭矩的增大而不断减小；拧紧速度较小时扭矩系数也相应较小，但扭矩系数离散程度明显偏高；终拧扭矩系数在首次拧紧时最小，第二次拧紧时迅速增加，之后趋于稳定。

英文摘要：

In an effort to study the actuality of great scatter of bolts preloads in one kind of cast aluminum housing, bolt tightening experiments are conducted on fastener torsion-tension test machine. Number of tightening/loosening cycles, tightening speed and other tightening process controllable factors are considered. The experimental results show that ： torque coefficient decreases con- tinuously with the increase of torque in the process of bolt tightening;with the decreases of tightening speed the average torque co- efficient decreases while its scatter is apparently greater;final torque coefficient is smallest in the first tightening, while come to second tightening/loosening cycle it rapidly increase and then with the tightening/loosening cycle＇ s increase it turns stable.