Investigation to enhance the mechanical properties of damaged flat-clinching joints by reconditioning processes

Joint damage could reduce component reliability and safety. In this paper, a simple and convenient reconditioning process for flat-clinching joints was proposed. The damaged joint was compressed by applying reconditioned force through the upper and lower flat dies to improve the mechanical properties. Compared to other exiting research, the process is easy to operate and requires no additional attachments. Meanwhile, the damage status of the loaded joint, material flow and the causes of improving mechanical properties were illustrated. In addition, the effect law of various reconditioned forces on the mechanical properties of the joints was also investigated. The results show that the flat-clinching joints are damaged when loaded beyond the shear load. However, the mechanical properties can be reconditioned when the interlocking structure remains unbroken. The main reason is that the reconditioning process reconstructs the interlocking structure and increases the neck thickness. Besides, the joint bulge height is also reduced by the reconditioning process. With increased reconditioning forces, the mechanical properties improve. The best mechanical properties are obtained at the recondition force of 40 kN. Compared to the original damaged joints, the shear force and energy absorption of the 40 kN reconditioned joints increased by 33.5% and 70.2%. This is important to promote the development of reconditioning processes and ensure part safety.