Microscopic Analysis And Mechanical Property Research On Clinched Joint

With the rapid growth of energy consumption, transportation industry encounters various challenges such as the energy shortage, environment pollution and so on. The use of lightweight materials such as aluminium alloys, magnesium alloys replacing steel has increased to reduce the weight of the automobile body. As these new materials cannot be jointed effectively, one of alternative joining technology is clinching which can join them firmly. With the purpose of studying on the bearing capacity and failure mechanism of clinching and establishing knowledge hierarchy completely, this essay focused on clinching process, the strength of clinched joint and microstructure obtained from simulation and experiment.Firstly, a finite element simulation about the forming principle and the process of clinched joint with segmented die was conducted, comparing with the simulation of integrate die and analyzing the metal flow in segmented die during clinching process. It was concluded that the simulation with segmented die obtained a better neck thickness and undercut, showing a good agreement with experimental result.Secondly, an effective and low cost microscopic test method about5052aluminum alloy was proposed, which could obtain clear metallographic image. Anodizing the membrane was used to make the specimen and DIC was used for observing the microstructure of clinched joint to analyze the metal flow in microscopic view. It was concluded that the flowing direction of metallographic examination was consistent with simulation. Clinching did not change the essence of materials, but produced working hardening on the local region, meanwhile improving the strength of clinched joint.Thirdly, a tensile test was performed to analyze the strength and the failure type of clinched joint. Through the simulation of the tensile process and the position of crack formation in a microscope, analyzed crack initiation, crack propagation and the neck fracture in the process of tensile. A research was conducted, which was about clinching with different precast angle. The test showed that the joint with zero angle could bear the largest tensile load; the bigger the angle the less the load. According to the test, a new formula was proposed to predict the maximum damage strength of clinched joint.Finally, a fatigue test about the clinched joints under different load levels was performed based on the tensile-shear test, for analyzing the failure type and fatigue life. Fatigue test showed that the clinched joint had a good fatigue behavior. Fatigue crack of clinched joint in SPCC was found at the edge of blind hole, and vertical with the load direction. Subsequently, the failure was occurred at the region of joint. Under the different load levels, the number of fatigue cycles of clinched joint in5052aluminium alloy all exceeded2,000,000. Results were supported by FEM analyses showing that the failure type and location in fatigue test was consistent with simulation.