Comparison And Analysis Of Actual Measurement Of Screw Coefficient Of Threaded F
When the torque coefficient method is used to tighten high-strength bolts, the average value of the torque coefficient and the standard deviation of the torque coefficient have a great influence on the tightening effect. In addition to theoretical calculations, the torque coefficient can also be obtained by actual measurement. This article analyzes the measured torque coefficients on the basis of experiments, discusses the relationship between different experimental conditions and corresponding torque coefficients, compares the differences in torque coefficients of various spun materials, and evaluates the influence of torque coefficients and standard deviations on connection reliability. Discussion on the reuse of high-strength fasteners.
The torque coefficient method for tightening threaded fasteners is one of the most commonly used methods for tightening high-strength fasteners. This method uses a torque value to control the tightening construction. It is suitable for various specifications, and is simple to operate and easy to use. Wide range of applications. In this case, the torque coefficient is an important numerical index to quantify the tightening torque, and its reliability and dispersion determine the tightening effect. Some design manuals list the pre-tightening torque of threaded fasteners.
These values are generally calculated by theoretical analysis, based on the commonly used friction factor and the expected stress level determined in advance, and can be used when the torque factor is not specified in the technical document. Refer to selection. However, the torque value calculated with a certain friction factor often has a gap with the actual situation. It is difficult to meet the requirements when the bolt clamping force needs to be accurately controlled. At this time, a test method should be used to determine the torque of the batch of fasteners used. coefficient.
The influence of different material nuts on the torque coefficient
The materials Q345C, 42CrMo, and 45 are low-alloy high-strength structural steel, alloy structural steel and high-quality carbon structural steel respectively. The average values of the torque coefficients of these three materials become larger, but the amount of change is not large, and the results are very similar. Even though the difference between the Q345C and 45 steel nuts, the average value of the torque coefficient differs by 0.005, and the relative value is only 3.3%.
The impact of this small difference in engineering practice is very small and can generally be ignored. It can be seen that the torque coefficients of these three materials are basically at the same level, and nuts of different steels have little effect on the torque coefficient. From the standard deviation point of view, the standard deviation of 42CrMo is the smallest, and the stability of the torque coefficient of the nut of this material is slightly better; while the standard deviation of the nut of 45 steel material is the largest, which is more than twice that of 42CrMo, and its torque coefficient is stable.
After the first two materials. The standard deviation of Q345C is in the middle, slightly larger than 42CrMo and smaller than 45 steel. The stability of the torque coefficient is between 42CrMo and 45 steel. Among the three materials, the nut with 42CrMo has better tightening performance.