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Abstract. The current trend in automotive design is to optimize components for weight. To achieve this, automotive designers need to have complete understanding of various stresses prevalent in different areas of the component. The chassis frame assembly of a heavy truck used for long distance goods hauling application is chosen for this investigation and dynamic stress-strain response of the component due to braking and cornering maneuvers are experimentally measured and reported. A quasi-static approach that approximates the dynamic maneuvers into number of small processes having static equilibriums is followed to carry out the numerical simulation, approximating the dynamic behavior of frame rail assembly during cornering and braking. With the help of commercial finite element package ANSYS, the quasi-static numerical simulations are carried out and compared with experimental results. This study helps in understanding prevailing stresses in truck frame rails especially during cornering and braking maneuvers and brings out all geometric locations that may be potential failure initiation locations. This study makes a case for further investigation on the effects of residual and assembly stresses on frame rails.

The large numbers of bolt holes cut into truck frame side members act as joineries and points of attachments for various sub systems of the truck. While these bolt holes are unavoidable due to their primary functional importance, the near hole residual stress resulting from the type of hole cutting operation plays a significant role in deciding the fatigue performance of frame rail structures. If the residual stress is tensile in nature, this along with the surface roughness at the hole surface can lead to early initiation of fatigue cracks around bolt hole surface. In order to assess the extent of plastic deformation and resulting residual stresses in near hole areas of frame bolt holes cut using drilling, punching, laser cutting and water jet cutting processes, experimental investigation was carried out through microstructure analysis and X-ray diffraction measurements. Apart from this, an assessment of shot-peened hole surface was taken up to understand the effect of shot-peening on fatigue behavior of frame rail section with bolt holes. Also the test specimens extracted from frame rail sections were tested for comparing the fatigue life of specimens having bolt holes cut using different hole cutting operations.

One of the major applications for cold formed carbon steel ‘C’ sections is through load carrying structural frame side members in heavy road vehicles. Though it is expected that forming operations would enhance the mechanical properties of sections as a whole by strain-hardening, it leaves certain amount of residual stresses throughout the sections. It is thus necessary to account for the effect of residual stresses remaining from cold forming operations accurately, while assessing the mechanical behavior of truck side frame rail sections. In this work, an experimental investigation was carried out to assess residual stresses induced by cold forming operation of truck frame rail sections through X-ray diffraction method. Also an attempt was made to study the effect of shot-peening operation employed as a surface enhancement method on frame rail residual stresses.