Study Of Fatigue Properties Of Clinched Joint

In recent years, the consumption of the global non-renewable energy resources increased dramatically can't satisfy the industrialization demand developing rapidly already, especially outstanding in automobile manufacturing industry consuming oil. Energy saving automobile manufacturing industry, there is an increasing need to achieving structure lightweight, using new light material. The use of lightweight materials such as aluminum alloys has increased to reduce the weight of the automobile body. It is difficult to join aluminum by welding because of its high thermal conductivity and the natural surface oxide layer. For spot welding connection producing a large amount of heat, will destroy material surface coating, similar to the new light material that can't use the traditional spot welding or riveting technology, clinching connection as a new connection technology of sheet metal to overcome the above shortcomings, opening up new ways for the car body structure lightweight, and presenting the new trend of development.Using FEM and test methods studied the static performance dynamic performance and fatigue strength of clinched joints. Making statics analysis for clinched joints by ANSYS got the joints'stress and stress contour plot to obtain the maximum stress location of the clinched joints, where the clinching occurred easily shear failure and peel failure. Using ANSYS/LS-DYNA explicit dynamic simulation software got technological process numerical simulation of the clinching. In the software made modal analysis for the cantilevered clinched joints finite element model. By the software analyzed the influence of parameter combination of different elastic modulus, density and passions'ratio on modal natural frequency of clinching. The model analysis shows that the transverse natural frequencies of single lap-jointed clinched joints increase significantly as the Young's modulus and the density of the sheets increase, but only slight changes encountered for variations of Passion's ratio.In this paper introduced the basic theory of fatigue strength and modern anti-fatigue design method, and described the character of the fatigue failure and the three stages of fatigue crack that was initiation, propagation and instability fracture of the crack. Based on metallographic organization chart of the clinching determined the fatigue eruption type of the clinched joints. By ANSYS/LS-DYNA analyzed the process of the fatigue crack propagation and the factor influenced on crack growth rate, the influencing factor including average cyclic stress. Stress ratio, loading frequency and amplitude changeless.