Research On Welding Seam Spacing And Rod Wall Thickness Matching Characteristic Of Coach Skeleton Joint

With the development of coach market, the quantity of coach is becoming larger and larger. Developing coach has already been the important trend of automobile industry. Self-supporting lattice structure coach which has the advantage of high stiffness, light weight is becoming the mainstream of coach structure design. In the self-supporting lattice structure coach body is the main load bearing structure as a result of the eliminating of the frame.Whether the technique of coach design is advanced or not has a significant effect on the characteristic of the structure. However, joints which bears heavy load are frequently occurred in the skeleton of the coach. Stress concentration is very common in joints like that. Stress concentration not only affects the strength of the structure, but also leads to fatigue destroy. Effective control of the stress concentration will do good to the reliability of the structure. In most circumstances, it can be improved by optimizing the joint structure. In this paper, how the welding seam spacing affects the strength of the joints is discussed. How the rod wall thickness matching affects the characteristic is also preliminarily discussed. The main contents are as follows.Based on the characteristic of the skeleton of coach, a beam-shell mixed model which is based on the super element and MPC technique is used. The actual shapes of the joints are considered using this kind of model. In order to examine the accuracy of the super element model, a shell model is also set up to make a contract between the two modeling method. By the analyzing the two models, results show that the stress and the deformation of the super element model has a very tiny error comparing to the shell model. So the super element model can totally be used in the future research. In order to analyze how the welding seam spacing affects the strength of the joints, varies welding seam spacing are set using super element model. The results show that using 7.5mm or 10mm welding seam spacing makes the joints a lower stress level. While welding seam spacing increase from 5mm to 7.5mm, the stress level of the joints decrease, while welding seam spacing increase from 7.5mm to 40mm, the stress level of the joints increase. In this part, how the welding seam spacing affects the strength of joints with different rod wall thickness matching is analyzed, for the rod wall thickness matchinges are varied in different companies and different types of coach. Base on the research above, different matches of beam wall thickness are set. And from the result we can see that the way that welding seam spacing affects the strength of the joint doesn't change while different matches of beam wall thickness is used.The author also analyzed how the rod wall thickness matching affects the strength of joints. The research choose the crossbeam, the upright pillar and the incline pillar as variable parameters to observe the strength of joints, on the condition that the total mass of the structure stay the same. The results proved that using different rod wall thickness matching can lead to different strength and the effect is obvious.The joint super element model is applied in the side wall of a coach body. Three types of different welding seam spacing are set to the joint and the joint super element model are inserted into the coach body to study whether the way how the welding seam spacing effects the strength which shows in the previous research is also correct. The results show that under the bend loading case, using the welding seam spacing of 7.5mm and 10mm can decrease the stress level 5%-30%. While under the torsion loading case, the strength of the joints varies with the change of the welding seam spacing, but it's not as significant as under the bend loading case.