Study On Static Strength Of Seat Structure And Structure Optimization By FEM

Nowadays, more and more families in China have their own cars. Consequently, the comfort and safety of cars are becoming a hotspot, which are considered as one of the most important things, when someone buys a car. Being the closest part to people, seat and its comfort and safety have been paid more attention by the car drivers and the manufactures.Based on regulations and standards of other countries, such as ECE and FMVSS, a new regulation on seat system was established in 1992, which was put into practice compulsorily three years later. Therefore, all the seat manufactures have to face new challenges. By the force of the new regulation, a lot of seat manufacturing factories have put more attention on the seat safety design and made much effort to find some more efficient method in seat safety design. At the same time, the contemporary seat designer is faced with the task of creating a more efficient, lightweight structure at minimum cost. Computer-aided engineering design methodology has been developed and employed in the design of seating systems successfully in abroad. But it is still in the beginning state in seat industry in our country. The project mentioned in this paper is a task cooperated with FAW－VW, whose aim is to find a practical method which can aid the seat structure design.The seat safety is decided by the static performance and its performance during impact. Seat's static performance relates to the seat frame strength, pillow displacement and the strength of pillow under static loads. While seat's dynamic performance is focused on the issue of seatback strength requirement and on the general acceptance by the automotive design of community of occupant energy management by means of yielding seat structures. Finite Element Method was employed in this paper to predict the performance of seat structure under static loads. Using UG, Hyermesh and ABAQUS, a finite element model of seat frame was built up and some data were gotten which were certified by the tests. The main contents of this paper are described as follows:1. In order to validate the reliability of simulation results, some tests were carried out. In the test, strain gauges were used to measure the detailed strain of some points on the seat frame. After data processing, the stresses of the points were gotten. There were also some discussions about the cause of the test errors in the paper. And based on the results of discussion, some methods to improve the test were presented in the paper.2. A finite element model of seat frame was built in Hypermesh,which consisted of two kinds of section, shell section and beam section. There were 16,458 nodes and 16,188 elements in this model. Considering the loads distribution, the cover, seat cushion and some springs were ignored in the model. The seat frame was assembled by three kinds of connection, welding, bolting and riveting. In order to make the simulation easier, all the connections were defined as rigid connection in the model.3. The deflection of the pillow foam was thought to be related to the pillow deflection. For this reason, a pillow assembly FE model, which included not only the frame but also the foam, was built up and added to the seat structure model. There were 16,952 nodes and 17,190 elements in the model.4. Based on requirements in our national regulation, simulations were carried out using ABAQUS. Comparison with the test results hand shown predicted seat performance to have a high degree of accuracy with actual test data and the method used in building the FE model was reasonable. The average deviation of stress between the simulation and test was under 15%. Simultaneously, discussions about the cause of the differences between the test and simulation were presented in this paper in order to modify the model.In the pillow deflection test, a head model and a back model were required to be used to add the force. But it was too complicated for simulation. So the way of adding loads was simplified in the model and was validated by the tests. 5. It has be...