This book presents a fatigue life prediction based on finite element analysis under non constant amplitude proportional loading. Parabolic spring is the vital component in a vehicle suspension system, commonly used in trucks. It needs to have excellent fatigue life and recently, manufacturers rely on constant loading fatigue data. Author thank to the faculty members of Mechanical Engineering Department of R.V.R & J. C College of Engineering for providing meritorious suggestions and full co-operation for the culmination of this book.