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前文已述及,用扭矩法拧紧高强度螺栓时,扭矩与螺栓预拉力存在着以下关系:M=KNd。必须给出准确的扭矩系数K值,才能确定施工扭矩M值,进而才能保证螺栓准确地达到设计预拉力N值。因此,如何精确确定扭矩系数是保证高强度螺栓施拧质量的关键问题。扭矩系数是个综合系数。与螺栓螺纹之间的摩擦系数及螺母和垫圈之间的摩擦系数有关。而影响这些系数的因素较多,如润滑程度、加工精度、加工光洁度、脏污程度及有无锈蚀等。因此,扭矩系数的离散性较大,不进行足够数量的试验,是得不出准确的数值的。
As mentioned earlier, torque tightening high-strength bolts, the torque and the bolt pre-tension there is the following relationship: M = KNd. Must give accurate torque coefficient K value, in order to determine the value of construction torque M, and thus can guarantee the bolt to accurately reach the value of pre-design N value. Therefore, how to accurately determine the torque coefficient is to ensure the quality of high-strength bolt screw the key issue. Torque coefficient is a composite coefficient. The coefficient of friction between the thread and the bolt and the coefficient of friction between the nut and washer are related. The factors that affect these factors are more, such as the degree of lubrication, machining accuracy, machining finish, dirt level and whether the rust and so on. Therefore, the torque coefficient of the larger discrete, without a sufficient number of tests is not accurate value.