Loosening and sliding behaviour of bolt-nut fastener under transverse loading

Abstract

Considering the efficient productivity and maintainability, most of machine and products has many joints (e.g., fastening, welding and adhesive joints). Especially, the bolted joints have been frequently used for these purposes as machine elements. However, many troubles such as loosening or fatigue failure of bolted joints were often experienced. More attentions must be paid on the improvement of the strength and the reliability of these bolted joints. It is generally said that the relative slippage between nuts and fastened body under the transverse loading will generate the rotation of nuts and cause the loosening of bolted joints. [1, 2]. For example, the thermal expansion due to temperature change between jointed members may cause these slippage and loosening problems. The aim of this present research is to clarify the mechanical behavior of bolted joints under transverse loadings, and present the critical relative slippage (Scr), more than this slippage the loosening will occur. To derive this critical relative slippage (Scr), at first the resistant bending moment between bolt/nut contact interface (Mn),and equivalent stiffness on bolt head/fastened body contact interface(kw) were derived.. Then the validity of resistant bending moment between bolt/nut contact interface (Mn),and equivalent stiffness on bolt head/fastened body contact interface(kw) were confirmed by the quasi-static loading test. Finally, the validity of critical relative slippage (Scr) was confirmed by the repeated cyclic loading test.

Keywords

• bending deformation of bolt
• bolt-nut fastener
• critical relative slippage
• loosening criteria