Effect of interference magnitude on ultimate strength and failure analysis of aluminium-drill-pipe-body-tool-joint-assemblies with Johnson-Cook model

Abstract

In this paper, a three-dimensional non-linear finite element model of aluminium drill pipe body and tool joint assemblies is established to analyze the effect of interference on ultimate strength and failure modes. Johnson-Cook model is selected to describe the plastic behavior and failure phenomena. For quickly meshing thread connection into hexahedron grids, grid parametric modeling program is written by Matlab software. The interference assembly is carried out by coupling the temperature field with the stress field. The accuracy of the model is verified by experiments, and the error is less than 6%. The ultimate torsional strength, ultimate tensile strength, ultimate torque under different tension, failure modes and anti-loosing ability are obtained for different interference values. The result shows that interference values have little impact on ultimate tensile strength but have positive effect on torsional strength. For the coupling action of tension and torque, the ultimate strength for larger interference value is greater than smaller interference value. Besides, critical values for failure mode transition are found under different interference values. When tension exceeds the critical value, the failure modes changes from thread body fracture to thread teeth failure. The anti-loosing ability increases with the increase of the interference, however, for the interference being greater than a critical value, the influence of the interference will be almost unchanged. The present results can help to determine the safe range of working parameters for aluminium drill pipe in practical engineering, and provide theoretical support for the optimization of interference in the production of aluminium drill pipe.