Relation of hardeninig, fatique strength and residual stress in AISI 4140 steel

ivRELATION OF HARDENING, FATIQUE STRENGTH AND RESIDUALSTRESS IN AISI 4140 STEEL(M.Sc. Thesis)Mehmet SUBASIGAZI UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYJanuary 2005ABSTRACTIn this work, an AISI 4140 steel material having different hardness gradeshasbeen examined due to the effect of fatique strength versus residual stress usingelectro-chemical layer removing technique. The sample materials used in thework first had be en brought to 40,45,50 HRC hardness grades and then theexperiments were carried out. At the end of the experiments, the fatiquestrenghts of the materials which were turned and quenched to the HRC 40, 45,50 grades have been found to be 463,783,792 and 739 MPa respectively. Fatiguestrength has been found to be the best in 45 HRC quenched specment. At theend of the measurements of residual stresses, tensile residual stresses have beenobserved on the surface of the samples. These measurements are 210, 169, 299and 203 MPa respectively.Science code : 708.3.028Key Words : Residual stresses, hardening, electro chemical processing,fatigue strengthPage Number : 107Adviser : Assis. Prof. Dr. Çetin KARATAS