Influence of Manufacturing Processes on the Structural Behavior of Truck Frame Rail Sections

The sequence of manufacturing processes involved in the making of truck frame rail sections leave a certain amount of imperfections in the form of plastic deformation and residual stresses in it. These residual stresses along with the externally induced loading stresses together should not be allowed to cross the yield limit of the frame material as it leads to premature failure of frame rail before giving its expected life. One such manufacturing process inducing premature failure is studied in detail using experimental analyses and presented in this paper. The kink bending process employed on the already formed and bolt hole punched C section frame rail, leads to plastic deformation and material crowding around the bolt hole located near the kink bend area of the frame flange. Experimental techniques such as Three Dimensional (3D) Laser Scanning and X-Ray Diffraction (XRD) were employed to assess the extent of plastic deformation and the residual stresses around the bolt hole surface respectively. It was observed that there is a significant loss of surface contact around the deformed bolt hole area and the presence of tensile residual stresses crossing the yield limit of the material on the bolt hole surface, which in turn lead to early initiation of frame crack on the bolt hole surface during proving ground trials. Hence, it is inferred from the study that any automotive designer should look for eliminating those processes inducing imperfections in critical areas or at least relocate the bolt holes/bolted joints away from those critical areas to avoid premature failure of truck frame rail sections.