Axisymmetric finite element analysis (FEA) was performed on bolted joints to determine the effects of the threads on the bolt and member stiffnesses. For steel members, the member stiffness decreased 37.1, 37.7, 38.2, 41.0, and 49.4 percent for the 24, 20, 16, 12, and 8-mm-dia bolts, as the magnitude of the external load was increased. The external load was increased from zero to the value that caused the bolt force to equal its proof strength. The member stiffness for aluminum members decreased by 22. 7 and 29.9 percent for the 24 and 20-mm bolts. The cast iron members had decreases of 26.9 and 32.3 percent for the 24 and 20-mm bolts. Likewise, the aluminum/cast iron members decreased in stiffness by 25.5 and 30.0 percent for the 24 and 20-mm bolts. The member stiffness with no external load applied decreased by approximately 65 percent when changing from steel to aluminum members, 53 percent from steel to cast iron, and 60 percent from steel to aluminum/cast iron. Bolt stiffness varied less than 1.4 percent over the total range of the externally applied load for each of the bolted joint models. The decrease in bolt stiffness for the 24 and 20-mm-dia bolts was approximately 4 percent when changing from steel to aluminum members, 7 percent when changing from steel to cast iron members, and 8 percent when changing from steel to aluminum/cast iron members. Comparison is made to research results which did not include the influence of the threads.

Effects of bolt threads on the stiffness of bolted joints and bolt thread and head fillet stress concentration factors

An improved virtual material based acoustic model for contact stiffness measurement of rough interface using ultrasound technique

Microstructural transformation of a rail surface induced by severe thermoplastic deformation and its non-destructive monitoring via Barkhausen noise

Investigation into the interfacial stiffness ratio of stationary contacts between rough surfaces using an equivalent thin layer

At present, few scholars have studied the effect of surface roughness on assembly stiffness. The influence of the joint surface stiffness on the overall stiffness is neglected. In this paper, a new method for calculating the stiffness of bolted joints is presented. The effect of joint surface stiffness on the overall stiffness is considered. Firstly, the relationship between load and displacement between cylinder and cylinder (including the joint surface with certain roughness) is studied, and the stiffness characteristic expression of the joint surface is obtained; the results are compared with the traditional stiffness calculation theory, and then, the influence of bolt connection surface on bolt connection is studied and compared with the stiffness calculation results of traditional bolt connection. The results show that the theoretical model presented in this paper is more practical.

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Stiffness Calculation Method and Stiffness Characteristic Analysis of Bolted Connectors

Virtual material parameter acquisition based on the basic characteristics of the bolt joint interfaces

The invention discloses a bolt bonding surface real contact area measurement method and device, the device comprises a support box base, a lower test piece is fixed to the support box base, an upper test piece is connected with the lower test piece through a bolt, a through hole is arranged in the support box base, a plurality of nano-scale optic fiber displacement sensors are arranged in the through hole, the nano-scale optic fiber displacement sensors are connected with the lower test piece through regulating components, the top parts of the nano-scale optic fiber displacement sensors passes through the lower test piece and are connected with a bonding surface of the upper test piece and the lower test piece, and the bottom parts of the nano-scale optic fiber displacement sensors are connected with a computer through a signal acquisition system. According to the invention, nano-scale optic fiber displacement sensors are adopted to perform a bolt bonding surface real contact area measurement test under pretension loading, and a test of bolt bonding surface predeformation varying with pretension loading can be performed at the same time.

Yan Li

Papers

Virtual material parameter acquisition based on the basic characteristics of the bolt joint interfaces

Bolt bonding surface real contact area measurement method and device