International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 06 | June 2019 www.irjet.net p-ISSN: 2395-0072 © 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 1048 EVALUATION OF FATIGUE LIFE OF SUSPENSION KNUCKLE USING MULTIBODY SIMULATION TECHNIQUE Chandra Kush Chauhan 1 , Shreshtha Bandhu Rastogi 2 , Ushpendra Kumar 3 1 Chandra Kush Chauhan, Dept. of Mech. Engineering, TMU University, Moradabad, UP, India 2 Shreshtha Bandhu Rastogi, Lecturer, Dept. of Mech. Engineering, TMU University, Moradabad, UP, India 3 Ushpendra Kumar, Asst. Prof, Dept. of Mech. Engineering, TMU University, Moradabad, UP, India -----------------------------------------------------------------------***-------------------------------------------------------------------------- ABSTRACT:- Suspension is part of automotive systems, providing both vehicle control and passenger comfort. The knuckle is an important part within the suspension system, constantly encountering the cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using multibody simulation (MBS) techniques. Load time history extracted from the MBS is used for stress analysis. An actual road profile of road bumps was used as the input to MBS. The stress fluctuations for fatigue simulations are considered with the road profile. The strain-life method is utilized to assess the fatigue life. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. Mesh sensitivity analysis has been performed. The results show that the steering link in the knuckle is found to be the most susceptible region for fatigue failure. The number of times the knuckle can manage a road bump at 40 km/hr is determined to be approximately 371 times with a 50% certainty of survival. The proposed method of using the loading time history extracted from MBS simulation for fatigue life estimation is found to be very promising for the accurate evaluation of the performance of suspension system components. Keywords: Fatigue, multibody simulation, suspension system, knuckle, strain-life method, maximum principal stress. INTRODUCTION Suspension systems support the weight of the car and make it possible for the vehicle to travel on irregular surfaces with the minimum disturbance transferred to the passengers. It also allows the vehicle to corner with minimal rolling and to maintain the traction between the tires and road, thus providing control and safety. It consists of a knuckle, spring, shock absorber and control arms. The knuckle constantly faces time-varying loads during its service life. There are various points of application of structural loads to be applied in different directions at the same time, resulting in complex stress and strain fields. Due to these variable loads it is essential to predict the safe design life of the component in real-world loading conditions. METHODOLOGY A methodology is developed to use the load time history for fatigue life prediction when a road bump profile is considered as the input loading. Linear elastic analysis is performed using ANSYS software where the loads are the forces calculated from MBS. The ncode Design life software is used for fatigue life estimation. The suspension of a Proton SAGA is used in this study, and the material of the knuckle considered is FCD500-7. Fatigue properties for the fatigue life simulations are taken from ASTM A-536, which is equivalent to FCD500. Multi Body Simulation Multi body simulations are carried out to study of the kinetic/kinematic behavior of mechanisms. The motion and forces required, and the forces, moments, accelerations and position of each component of the assembly can be calculated and monitored in three dimensions. The components of assemblies are considered as rigid bodies, so their shape is not changed due to the application of forces during the simulations. For deformation and stresses produced in the components due to dynamic loads, a separate FE simulation is required; for which the instantaneous loads can be extracted from the MBS results.