Aspects of the stress and fatigue performance of threaded connectors.

摘要

Threaded connectors have been used in a variety of engineering structures forudhundreds of years. Although stress analysis of threaded connectors has beenudperformed since the early 1900's, there are still areas that are not fully understood.udThe way in which eccentricity affects the fatigue performance and stressuddistribution is one such area, and is the main area of research described in thisudthesis.udThe techniques of photoelasticity and fatigue testing were used to determine theudeffect of eccentricity on the stresses and fatigue performance of bolts. The resultsudshow that eccentric loading has a significant effect on the fatigue performance, butudthat this effect can be quantified if the local stress amplitude is considered. Theudphotoelastic analysis results show the eccentricity slightly increases the stressudintensity factors at the crack tip.udA number of two-dimensional and three-dimensional finite element models wereudcreated to detennine the salient characteristics of the models. The models wereudvalidated against the resuh from the photoelastic analysis and the results agreedudwell. Accurate results can be obtained from a two-dimensional model, but theudinformation obtained is limited unless many models are created. However, if audthree-dimensional model is created more information can be obtained, but the nutudthread run-out must be accurately modelled to obtain the correct stressuddistribution.udThe shape of cracks occurring in cyclically loaded steel bolts and the effect ofudcrack shape on the stress distribution was also investigated. The photoelasticudanalysis of cracked bolts failed to predict the shapes of cracks occurring inudcyclically loaded bolts. It is suggested that the inability of photoelasticity toudmodel plasticity is the cause of this failure and this is supported by results from anudelastic-plastic finite element model.