Loading...
Search for:
mehmanparast--ali
0.005 seconds
Effects of Laser Peening with Different Coverage Areas on Residual Stress and Fatigue Crack Growth
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor) ; Mehmanparast, Ali (Co-Advisor)
Abstract
Failure due to fatigue loading is one of the main reasons for the wear out of parts in the industry. Prevention of failure and improving the fatigue life of materials have been studied by many researchers. Desirable compressive residual stress have important effect on improving the lifetime of materials. Laser peenning leads to increase fatigue life of metals by creating compressive residual stress at the surface of the pieces.This study investigates the effect of different laser coverage areas on residual stresses using finite element method and also investigates the fatigue crack growth experimentally.Simulation results show that increasing the laser peening rows impart the residual...
Effect of Different Defects of Spot Welded Joint in Automotive Body on Fatigue Strength: Experimental and Numerical Investigation
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor) ; Mehmanparast, Ali (Supervisor) ; Reza Kashyzadeh, Kazem (Co-Supervisor)
Abstract
On average there are to resistance spot welding connections per vehicle. The quality of these welding directly affects the quality of the finished product and the strength of the vehicle against various loads, including road roughness, different maneuvers and even sudden impacts from accidents. During the spot welding process, unintentional failures occur due to the wrong choice of current, force and time. The aim of this study is to investigate the fatigue strength of three-sheets welding joints in numerical and laboratory methods, considering the defects of (Undersize weld, Stick, edge of sheet metal and Edge of sheet metal-SECANT) . For this purpose, a healthy spot welding model was first...
Reliability of Components Operating under Creep- Fatigue Conditions
, Ph.D. Dissertation Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor) ; Wang, Bin (Co-Supervisor) ; Mehmanparast, Ali (Co-Supervisor)
Abstract
The probabilistic behavior and the reliability of high-temperature defective components under creep-fatigue conditions have been assessed, considering different sources of uncertainty in “material behavior”, “geometric parameters” and “operation conditions”. For this purpose, deterministic calculations of creep-fatigue crack growth have been derived based on the R5 procedure, and then these relationships have been used at the heart of the probabilistic assessments. One of the aims of this dissertation was to present a procedure for assessing the reliability of defective components operating under creep-fatigue conditions. This procedure has been implemented on a benchmark problem, i.e....