ADVANCED COMPUTATIONAL STRESS ANALYSIS OF A STRANDED OVERHEAD LINE CONDUCTOR UNDER FRETTING FATIGUE CONDITIONS

摘要

Fretting fatigue of stranded conductors is widely acknowledged as a critical problem in electric utilities as it contributes to significant degradation of local fatigue strength of transmission line conductors, leading to drastic reduction of their service life. However, fretting fatigue behavior of conductor wires cannot be well predicted and characterized by either experimental testing or simplified theoretical models, owing to the synthetic geometry, material and loading complexities. Therefore, reliable computational models have been long expected. Nevertheless, helically stranded cable geometries, nonlinear material properties, substantial friction effects, and comprehensive contact interactions have made the task very challenging. This paper presents the nonlinear finite element (FE) stress analysis of an ACSR conductor-clamp system to describe the detailed mechanical response of stranded conductors under fretting fatigue conditions, from an applied mechanics perspective. A 3-D elastic-plastic, large deformation, multi-body frictional contact FE model was constructed and implemented as a multiple-load-step analysis to complete the load history of one fretting cycle. The FE model comprises all structural components of the conductor-clamp system - an ACSR conductor with 33 helical wires, a suspension clamp body, and its upper keeper and U-bolt - adding up to nearly 324,000 nodes, 310,000 solid elements and 274,500 contact elements. The salient features of FE modeling and numerical solution techniques for solving this highly nonlinear large model are discussed in detail, from which a faithful modeling methodology is developed and validated. The computational results show good agreement with some experimental measurements and field observations reported in the open literature.