A Three Dimensional Numerical Study of Stress Distribution in Bolt-Nut Connections

G.H. Majzoobi, A. Sadri, A. Bayat (Iran), and A.H. Mahmoudi (UK)


Unified threads, ISO threads, Withworth threads, Stress distribution, Numerical simulation.


Three dimensional simulations of bolt-nut connections have been carried out using ANSYS finite element code. Three standards, ISO, Unified and Withworth for both fine and coarse threaded connections have been used for the simulations. Stress distribution and concentration factor at the root of threads have been determined from the simulations. The results show that coarse threads are usually superior to the fine ones, as the stress concentration of fine threads is lower for majority of connections of different standards. The results also reveal that stress concentration factor may rise to 8 depending on the bolt size and standard. In nearly 70% of the cases, Unified threads enjoy the highest and Withworth threads enjoy the lowest stress concentration while no specific and regular trend can be observed for other cases.

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