Fatigue Life Estimation of Chassis Frame FESM Bracket for Commercial Vehicle

Automotive chassis is an important part of an automobile. The chassis serves as a frame work for supporting the body and different parts of the automobile it should be rigid enough to withstand the fatigue, shock, twist, vibration and other stresses. Along with strength, an important consideration in chassis design is to have adequate low damage and higher fatigue life. To improve the fatigue life and damage reduction are the two important criteria for the design of the chassis. This work deals with the analysis of the truck chassis. Structural systems like the chassis can be easily analyzed using the finite element techniques with a proper finite element model of the chassis. The work also deals with the static analysis, modal analysis of the chassis and fatigue analysis of FESM (FRONT END SUSPENSION MOUNTING) BRACKET of chassis, on the user requirements and improving its payload by changing the shape and thickness of the bracket which is attached to the present chassis frame. The FEM analysis is carried out with various alternatives. The truck chassis is modeled in CATIA V5 and the finite element modeling is carried out using Altair's pre-processing tool HYPER MESH. Static analysis is performed by using MSC NASTRAN/ANSYS to determine the high stress region, and also the maximum displacement. fatigue analysis is performed by using N-Code to determine the damage and life of the FESM bracket. The results are viewed through Altair's post-processing tool HYPER VIEW. it is observed that maximum stress induced is 155.7mpa which is less than the allowable stress of steel 205mpa, natural frequencies of six global modes were below 100 Hz, varying from 20 Hz to 90 Hz. Almost all of the truck chassis designs were based on these frequency ranges to avoid the resonance during the operating condition, the fatigue life of existed FESM bracket of the chassis is 13009.879 cycles has improved to 16857.432cycles and of damage of existed FESM bracket of the chassis is 1.149 it has been reduced to 0.602.