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Most studies on self-loosening behaviour of bolted joints under relative transverse movement of the clamped parts are limited to a single bolt joint. In this paper a comprehensive assessment is performed for the loosening behaviour of a multi-bolted joint with two bolts. Design influences such as material of clamped part and geometrical distance between bolts are investigated experimentally and using three dimensional finite element analysis. The importance of studying the component influence on self-loosening behaviour is highlighted using different cross sections of the clamped part. Influence of component deformation behaviour on self-loosening behaviour of the bolts are illustrated by experimental and simulation results. Risks of decomposing a multi-bolted joint into a single bolt joint for experimental investigation, such as in Junker’s test are highlighted.

This paper shows an approach developed to cover in detail different behaviour of threaded fasteners with a robust test setup for multibolted joints and numerical simulations by means of finite element analysis (FEA). Resulting from this combination, it is possible to monitor the axial, torsion and bending stress in fasteners themselves. Importance is given to interpretation of the measurement signals of strain gauge bolts. Integrity of the complete structure can be better interpreted with this approach. This depends on the modelling of bolts for FEA and the quality of the measured signals from experiments. For FE modelling the general purpose non-linear solver Abaqus is used, for preload measurement strain gauges are integrated into metric bolts. Simulation and experimental results from this unique test setup with several bolts are shown.

Self-loosening of bolted connections is a crucial failure mode for joints under transverse dynamic load. For some years, three dimensional finite element analysis has been enabled for avoiding experimental investigations of self-loosening. The aim of this paper is to emphasize the effect of joint design on the self-loosening of bolted connections, which is important for product development in early design stage. Joints consisting of internally threaded nut components are often heavier and stiffer as compared with light weight designs consisting of a separate nut. The difference of self-loosening is significant between arrangements with nut thread component and separate nut, although the design versions only contain slight modifications. Hence it is necessary to evaluate the effect of light weight design on self-loosening.