Research On Residual Stress Of 3J21 Alloy Micro Blanking Parts

Co40NiCrMn alloy(3J21 alloy) is a kind of widely used Co-based alloy with excellent comprehensive properties of high elastic, strength and hardness, high wear, corrosion and fatigue resistance and nonmagnetic. Therefore,3J21 alloy is often used to make elastic components in aerospace, instrumentation and precision machinery. Meanwhile, with the rapid development of microelectronic mechanical systems, the demand for micro parts is increasing rapidly. The miniaturization of products puts forward higher requirements for the forming precision of micro parts. As a new plastic processing technology, micro blanking has good quality in the cross section and high precision in size, so it is suitable for micro parts mass production. However, the residual stress will produce in the process of part forming, which will not disappear with the end of the forming process. And the existing residual stress has important influence on the mechanical properties and fatigue life. Therefore, the study on the residual stress of micro blanking parts has important significance to improve the service life and reveal the failure mechanism.The Nano indentation test was performed on the free-stress 3J21 alloy foil to study the indentation size effect, from which the influence of indenting depth on the load-depth curves and hardness was obtained. The models of indentation size effect were introduced to analyze the laws between the hardness of 3J21 alloy foil and the indenting depth. Finally to ensure the indenting depth that can be used to measure the residual stress of micro blanking parts based on the Nano indentation tests.Using the uniaxial tensile tests, the mechanical properties of 3J21 alloy foil were obtained. Based on the Johnson-Cook constitutive model often applied to metal material, the simplified constitutive model of 3J21 alloy foil was established. The finite element simulations were carried out for the 3J21 alloy foil micro blanking process, and the effect of blanking clearances in the micro-blanking process was studied. The variation and distribution law of stress were explored in the micro-blanking process.According to the blanking clearance obtained from the FEM results of 3J21 alloy micro blanking process, using the high precision forming equipment self-designed by the research group to blank the length of 400?m square part from the thickness of 100?m 3J21 alloy foil. The result showed that the shape of part was regular and the four parts of the blanking section were obvious, which proved that the equipment had high precision forming ability.In this dissertation, Nano indentation tests were performed on the free-stress 3J21 alloy foil and the micro blanking parts of 3J21 alloy foil. The effects of residual stress on the nano indentation parameters were researched. The results indicated that the residual stress affects only the indentation loading response. From the point of view of indentation work, analyzed the residual stress on the influence of the indentation process. Based on the concept of energy balance, established the residual stress calculation model. And the indentation process was simulated by way of pre-stressed to verify the correctness of the residual stress calculation model, finally used it to measure the residual stress of micro blanking parts.