Numerical Modeling and Evaluation of Fatigue Life of Composite Cables for Robot Arms

Abstract

Industrial robots in the automotive and precision equipment industries have been dramatically increasing in recent years, and the industrial robot arms have structures of composite cables made by twisted strands. There are many design parameters for composite cables such as total number and diameter of a strand, the number and diameter of filaments in a strand, a twisting direction and a pitch length of a strand, etc. It is time-consuming to estimate the fatigue life of composite cables based on experiments considering effects of design parameters on mechanical behaviors. Therefore, a numerical modeling method for composite cables with various twist patterns and pitches was proposed by using Python code in this study. Furthermore, a hybrid model of a strand was developed with beam and solid elements of the finite element method. The fatigue life of composite cables was estimated based on numerical analysis with hybrid models and fatigue test of a single filament. The numerical results showed that the mechanical characterization of the rung twist pattern was inferior to that of the normal twist pattern, and the fatigue life was inferior as the twist pitch became shorter. The proposed numerical modeling and evaluation method of the fatigue life are useful for the design and development of composite cables in robotic arms.