A Calculation of the Main Load Coefficient in Threaded Connections

Threaded connections of machine parts are widely used in various technical devices. The needs of modern machines stimulate the development of accurate methods for calculating and assembling threaded connections. The problem of calculating the strength of the connection is associated with determining the coefficient of the main load that affects the distribution of the external load between the bolt and the machine parts. One part of the load falls on the bolt; the other part unloads the connection elements. Until recently, when calculating the coefficient of the main load, approximations or recommendations to take its value in the range of 0.2–0.3 have been used. This paper refines the calculations and presents specific mathematical expressions for a computer program developed for calculating the coefficient of the main load. The calculation results show that the value of coefficient of the main load varies over a wide range depending on the bolt diameter, thickness, material of the parts, etc. An analysis of the results of programming and the construction of the regression dependence of the coefficient of the main load on the thickness of the connection for a given series of standard bolts is carried out using the statistical package Statgraphic Plus. Regression simplifies the calculation of the coefficient of the main load for any thickness of parts with a slight decrease in accuracy.

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