A hybrid method for bolted joint modeling considering multi-scale contact mechanics

Significant effects of the bolt arrangement on the contact characteristics of bolted joints have been demonstrated, which are strongly associated with the dynamic performance of mechanical structures. However, the complexity of interfacial pressure distribution and the randomness of surface microtopography bring challenges to the accurate characterization of the multi-scale contact mechanics. Herein, a hybrid method combining fractal theory with the finite element method (FT-FEM) is proposed, which formulates the interfacial contact evolution in the elastic, elastic-plastic, and fully plastic stages. The complementarity of these two methods makes it possible to reveal the contact mechanism at both micro and macro scales and overcomes difficulties in reflecting the detailed joint contact characteristics in the overall dynamic model. To explore broader implications, FT-FEM is applied to the optimal design of bolt arrangement in an ultra-precision machine tool. Good agreements in calculation results and experimental data validate the accuracy of the proposed FT-FEM and the dynamic simulation. Replacing 15-M10 bolts with 19-M8 bolts results in a 2.9% enhancement in the contact stiffness and a 2.283% attenuation in the vibration response of the workpiece. The results also show that adjusting the bolt arrangement according to the working condition can strengthen the bolted joint effectively. FT-FEM contributes to solving contact problems in various mechanical structures, and the findings have wide practical applications in bolt arrangement optimization. • A hybrid method for bolted joint modeling considering multi-scale contact mechanics. • New method combines improved fractal theory and finite element method. • Bolt arrangement optimization is carried out applying the method in dynamic analysis. • Experimental validation is done with bolted structures and machine tool.