Impact of technological and operational deviations of the thread flank angle on the fatigue life of the tool joint

Abstract

The total effect of technological and operational factors can lead to various types of deviations of the flank angle of the tool joint thread profile, which are uneven along the axis. It is shown that uneven deviations of the flank angle appear when tapered threading with a lathe tool with a non-zero rake angle. To analyse the effect of these deviations on the fatigue strength of the joint, a parametric axisymmetric finite element model of the ZN-80 tool joint was developed in Abaqus/CAE. In the fe-safe program, dependences of the fatigue life in the thread roots on the deviations of the flank angle of the pin thread were obtained. The box thread has not been changed. To increase the fatigue strength of the pin, in most of the cases considered, negative deviations of the flank angle of the short flank of the pin thread should be avoided, and preference should be given to positive ones. Negative relative deviations of both flanks usually worsen the fatigue strength of the pin due to the "wedge" effect. Types of deviations have been found that significantly increase fatigue strength and have an “anti-wedge” effect or equalize the load in the thread. They need detailed studies and can be the basis for optimizing the values of flank angle deviations on each turn.