Design Optimization Of C-frame Of Riveting Equipment

With the increase of climate change and environmental pollution,as the main way of saving energy and reduce emissions of vehicles,lightweighting has become an important means for automobile manufacturers all over the world to take on social responsibility and improve their competitiveness.The use of lightweight materials such as aluminum alloy and high-strength steel on the body in white is an effective way to achieve lightweighting of automobiles.Self-piercing riveting is a cold connection technology for connecting two or more sheets.It is increasingly used in the connection of lightweight materials in automotive bodies.The C-frame of self-piercing riveting equipment is the main bearing structure.In order to ensure the reliability and stability of the process,it is necessary to improve the stiffness of the C-frame and avoid excessive displacement and deflection under loads.In addition,in order to be held by the robot arm for flexible production,the C-frame can't be too heavy.Therefore,based on structure optimization theory and finite element method,this paper carried out the structure design optimization of the C-frame of self-piercing riveting equipment.The main research work of the thesis is as follows:1)Based on the rational modeling of the problem,different structural optimization methods are explored in the design of C-frame of self-piercing riveting equipment.Based on traditional methods,the application of the homogenization method of topology optimization and shape optimization method in the plane multi-thickness structure is proposed.The penalty function is used to constrain the topological optimization results to the discrete thickness,and the Lagrangian method is applied to solve the shape derivative for the external and internal boundaries during shape optimization.The structure optimization design is then carried out by establishing an optimization process.2)Introducing the shape deflection as the optimization objective function,based on the NSGA-II algorithm,the genetic algorithm is applied in two different ways in the optimization design of the C-frame of selfpiercing riveting equipment.First,the Voronoi diagram is used to represent the plane multi-thickness structure.With designed crossover and mutation method for Voronoi sites,the topology optimization is carried out with less a priori information.Then,the characteristics of C-frame structure are summarized to apply the genetic algorithm to find the optimal shape parameters.Benefiting from the characteristics of multi-objective optimization of genetic algorithm,both methods have obtained a series of non-inferior solutions on the Pareto front,which have different advantages in weight or stiffness.3)With Hyper Mesh software,static and dynamic simulation is carried out using the finite element method to verify the improvement of the stiffness of the optimization results.Through modal analysis and transient response analysis,the optimization results are analyzed and compared.It is found that the holes on the neck of the C-frame can improve the coaxiality of the die and the punch in the process of structural vibration.4)Combined with the characteristics of the new process of friction selfpiercing riveting,the optimization design is reinforced under torque conditions using the free-shape optimization method,by adding reinforcing ribs and adjusting the shape of the holes.