Abstract

Bolted connections are widely used in various mechanical structures due to their superior fastening properties. However, vibration and fatigue loads in the structure are likely to cause fatigue failure of the bolted joints, especially those under high temperature, such as in aero-engines. This paper mainly studies the low-cycle fatigue life of the pre-tightened bolts working at a high temperature. A novel test fixture is designed for fatigue tests, and low cycle fatigue tests of pre-tightened bolts are conducted at the temperatures of 550 °C and 650 °C, respectively. Furthermore, a new low cycle fatigue model that is based on the Von Mises equivalent stress/strain criterion is proposed. Meanwhile, the proposed model is used to predict the high-temperature low cycle fatigue life of pre-tightened bolts according to the stress/strain results obtained by finite element analysis. There is good agreement between the experimental results and those obtained by theoretical prediction, which validates the accuracy of the proposed fatigue model. Research results will provide a theoretical basis for the low cycle fatigue life prediction of pre-tightened bolts.

Highlights

  • Bolt-nut connections, as one of the most important and basic fastening elements, are widely used in common and special mechanical structures

  • Research results will provide a theoretical basis for the low cycle fatigue life prediction of pre-tightened bolts

  • The distributions of the stress and strain of the the structure being pre-tightened are obtained through element analysis, the stress structure afterafter being pre-tightened are obtained through finitefinite element analysis, and and the stress and and strain distribution contours are shown in strain distribution contours are shown in Figures 9 and 10, respectively

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Summary

Introduction

Bolt-nut connections, as one of the most important and basic fastening elements, are widely used in common and special mechanical structures. Pre-tightened bolts play an important role in the security and reliability of the whole structural system, as the failure of the bolts (e.g., fracture, looseness, etc.) may cause a catastrophic accident [1,2]. Most of the failures that are encountered in practice are caused by fatigue of material. It is, important to search for a proper method to predict the fatigue life of the pre-tightened bolts accurately. The main contents include analysis of the serious stress concentration at the root of threads [3], elasto-plastic stress and strain distributions within bolt-nut connections [3,4,5,6], and fatigue life estimation of the bolt [7,8,9]. Ifergane et al [10]

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