Abstract
This study has clarified mechanical and dynamic characteristics of multi-material structures based on bolted joints including magnesium alloy and established an analysis method. Magnesium alloy specimen bolted in multiple combinations with other materials, and finite element method (FEM) were used to see natural frequency, vibration modes, clamping force, and interfacial stiffness of the jointed parts. A series of hammering tests and numerical simulations were performed to clarify the relationship between the natural frequency and the clamping force, and the effect of the magnesium alloy was investigated. The numerical simulations were executed by the FEM based on a mechanical model to simulate the mechanics of the real contact area between bolted joints interfaces. The natural frequency of the bolted joints asymptotically increases to a constant value as the increments of the clamping force. This is due by the real contact area of the interfaces between the bolted plates increases as the increments of the clamping force. Compared to the other materials, the natural frequency of the magnesium alloy joint tends to increase quickly to the constant value at a lower clamping force. It considers that the low Young’s modulus of the magnesium alloy creates the real contact area increase at a higher rate even at low clamping force, because the interfacial stiffness is saturated when the real contact area becomes large enough. In addition, the natural frequency of the multi-material bolted joints is affected by the constituent materials in the case of each materials characteristics affecting the deformation shape in different vibration modes of the bolted joints. The real contact area and the material constants show strong influences on the dynamic stiffness of magnesium alloy bolted joints. The rigidity of the constituent materials has more influence on the deformation shape with many nodes and antinodes through vibration modes.
