Mechanical Behavior Laboratory University of Nevada, Reno


[J45] Zhang, M., Jiang, Y., and Lee, C.-H., 2007, "Finite Element Modeling of Self-Loosening of Bolted Joints," ASME Journal of Mechanical Design, Vol.129, pp.218-226 doi: 10.1115/1.2406092

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Paper Abstract

A three-dimensional finite element (FE) model with the consideration of the helix angle of the threads was developed to simulate the second stage self-loosening of a bolted joint. The second stage self-loosening refers to the gradual reduction in clamping force due to the back-off of the nut. The simulations were conducted for two plates jointed by a bolt and a nut and the joint was subjected to transverse or shear loading. An M12x1.75 bolt was used. The application of the preload was simulated by using an orthogonal temperature expansion method. FE simulations were conducted for several loading conditions with different preloads and relative displacements between the two clamped plates. It was found that due to the application of the cyclic transverse load, microslip occurred between the contacting surfaces of the engaged threads of the bolt and the nut. In addition, a cyclic bending moment was introduced on the bolted joint. The cyclic bending moment resulted in an oscillation of the contact pressure on the contacting surfaces of the engaged threads. The microslip between the engaged threads and the variation of the contact pressure were identified to be the major mechanisms responsible for the self-loosening of a bolted joint. Simplified finite element models were developed that confirmed the mechanisms discovered. The major self-loosening behavior of a bolted joint can be properly reproduced with the FE model developed. The results obtained agree quantitatively with the experimental observations.


Paper Figures

Fig. 2

Fig. 2. Finite element results and experimental observations (Download data).

Fig. 3

Fig. 3. Clamping force reduction with the influence of Δδ/2, P0=25 kN) (Download data).

Fig. 4

Fig. 4. Nut rotation with the influence of Δδ/2, (P0=25 kN) (Download data).

Fig. 5

Fig. 5. Influence of preload (Δδ/2=0.45 mm) (Download data).

Fig. 6

Fig. 6. Influence of friction coefficient between the clamped plates on the FE results (Download data).

Fig. 8

Fig. 8. Variations of contact pressure of three nodes with loading cycles (Download data).

Fig. 9

Fig. 9. Variations of contact pressure distribution with loading along the arc ABCED (Download data).

Fig. 10

Fig. 10. Amplitude and mean value of the contact pressure distribution (Download data).

Fig. 11

Fig. 11. Microslip amplitude along the contact surface of the first engaged thread (Download data).

Fig. 12

Fig. 12. Distribution of microslip amplitude in the bolt axial direction (Download data).

Fig. 15

Fig. 15. Simulation result from the microslip model (Fig. 14) (Download data).

Fig. 18

Fig. 18 Simulation result from the slip-stick model (Fig. 16) (Download data).

Fig. 19

Fig. 19 Evolution of the slip-stick conditions in the contact area with the variation of the bending moment (refer to Fig. 17 for B, C, D in the bending history): (a) slip-stick condition when the bending moment reached 10 Nm; (Download data) (b) slip-stick condition after the bending moment returned zero from 10 Nm; (Download data) and (c) slip-stick condition after the bending moment reached -10 Nm (Download data).