Spring-back Prediction Study In Sheet Metal Bend Of L-Shaped Based On Numerical Simulation

The spring-back is not only one of the most common defects in the sheet metal forming, but also one of the hardest to control deficiencies, especially in the bending process. In recent years, Numerical simulation technology has become an important means to spring-back prediction. At present, the results of spring-back prediction of sheet metal forming are not satisfied and research on improving spring-back prediction of sheet metal forming is still difficult point and hotspot.In this paper, it regard the spring-back of the L-shape as research object, the spring-back prediction of the L-shape part is completed based on the numerical simulation of technology and the test optimization of technology. Experiment results show that the new prediction method can control the rebound forecast error within a certain range, the compensate measures has been achieved good results. The main contents of this dissertation are as follows:1. Taking into account the complexity of the spring-back factors, the article elaborate the theory of sheet metal spring-back and the theory of its numerical simulation before carrying out of forming spring-back prediction, and analyze the effects various process and numerical simulation factors on sheet metal spring-back.2. The spring-back simulation is finished by FEM in sheet metal stamping. Here, the dynamic explicit method is adopted to calculate the forming and the static implicit method is used for calculating the spring-back after forming process.3. Using orthogonal experimental design and the uniform design method to arrange the multi-factor and multi-level experimental conditions about numerical simulation programs of sheet metal spring-back of L-shaped. According to data analysis results can be drawn:the uniform design is more suitable for spring-back prediction of L-shaped, it can more levels within the range of experiments, and which can express the characteristics and discipline of various levels more accurately,and can find out process conditions more reliable.4. The impact of the number of integration points on the rebound was the most significant; relative bending radius and die gap on spring-back take second place; and the friction coefficient on the rebound effect is not obvious. Optimum range from various factors: the number of thickness integration points to the range of 2 to 5; die gap range is 0.98t to 1.02t; relative bending radius range from R/t≤3; friction coefficient range from 0.10 to 0.16. 5. The regression model of spring-back compensation of L-shaped parts be established, using genetic algorithms to optimize the quadratic nonlinear regression equation, the best value of each factor are obtained within range when the regression model to obtain minimum.6. The optimal combination of level of various factors are simulated, select the optimized simulation prediction of spring-back angleθmin as the spring-back compensation amount of mold geometric surface, and design die machining of L-shaped compensation film. Through the actual verification, the predictions are satisfied with forming and spring-back of compensation parts, to improve the forming precision of parts.