Finite element analysis of threaded connections

Abstract

The purpose of thesis thesis was to accurately model threaded connections using finite element analysis. This was accomplished by machining and loading an experimental test assembly, then comparing the overall spring rate of the test assembly to results obtained by finite element analysis. Part One of the thesis is the experimental portion. Included in this area are the test procedure, data and results. From the results, an overall effective spring rate of the test assembly was derived. Part Two of the thesis is the finite element analysis. The important aspect of the finite element analysis was the method of transmitting the forces from the crew threads to the nut threads. A specific type of element, called a gap element was utilized to transmit fore from the screw threads to the nut threads. The particular gap element used has an assigned stiffness and transmits a force only when compressed. Presented in the paper are the results obtained from various finite element models. It will be shown that a threaded connection can be reasonably modeled using gap elements between the screw and nut threads to transmit forces. The stiffness values for these gap elements can simply be either near rigid or unassigned. No method of simulating the spring rate of the thread is necessary. It will be shown that this method will distribute the percent of load to each thread in accordance with known findings. Included is a comparison of the finite element results to theoretical analysis on the non threaded portions of the model. Finally, recommendations for further work are presented.