Fatigue life of the welding seam of a tracked vehicle body structure evaluated using the structural stress method

Abstract The supporting roller is an important component in the driving systems of tracked vehicles. Through the bracket structure, the supporting roller is bolted to the vehicle body welded with a reinforced metal plate, providing vertical support and lateral guidance of the track. The strengthening weld structure between the bottom plate and the vehicle body is the root of the cantilever beam, where stress is concentrated and fatigue damage is easily accumulated. The fatigue life of the whole vehicle is affected by the fatigue damage in this part. This paper proposes a structural stress method to evaluate the fatigue life of the welding seam of a tracked vehicle body. Further, the proposed method is evaluated under typical road-load spectra. Initially, the base-metal and weld structures were subjected to monotonic tensile and cyclic plastic deformation tests. The tensile strength of the weld sample was approximately half of that of the base metal. Next, the welded structure of the supporting roller bracket was simulated using a finite element model. The calculated stresses were consistent with the fatigue crack locations in the welded structure. The structural stress was not dependent on the grid density. Subsequently, multibody dynamic simulations of the whole tracked vehicle were performed on four standard road surfaces constructed using the harmony superposition method. The road-load spectra at the axle head of the supporting roller were calculated under four pavement conditions, and the fatigue life of the weld structure of the supporting roller bracket was determined. The calculated fatigue life was considerably lower than the designed fatigue life. Finally, the initial weld structure was redesigned by increasing the size of the strengthening metal plate and the weld length. The fatigue life of the redesigned structure was considerably longer than that of the original structure, indicating that the proposed method can effectively analyze the fatigue life of the welding seam and that it can be used to optimize the design scheme.