| 316 stainless steel is widely used in complex working conditions,especially in cyclic loading condition,as its high strength,high toughness,high temperature resistance and excellent corrosion resistance.A gradient nanostructure(GNS)surface layer is formed by using shot peening treatment in the surface of engineering materials.It is beneficial to inhibition the crack initiation and prevent crack from propagation for the materials.Thus,the GNS surface layer is of great importance to improve fatigue property and fatigue life.In this paper,the low cycle fatigue with strain controlled is conducted.The strain rate of R_?=0.1 and loading frequency of 0.1 Hz are chosen.The total strain amplitude of 0.3%,0.4%and 0.5%are used in the low cycle fatigue tests.Low cycle fatigue behaviors and fatigue life affected by shot peening GNS surface layer and total strain amplitude on 316 stainless steel are investigated.The main findings of the present work are as follows:(1)The stress amplitude increases after shot peening,while the plastic strain and cyclic hardening factor decrease.With the total strain amplitude increases,the cyclic stress amplitude,cyclic hardening factor and plastic strain amplitude increase and they have the similar tendency.There is secondary hardening for the shot peening specimen under the higher total strain amplitude.(2)Shot peening can improve the low cycle fatigue life of 316 stainless steel under lower total strain amplitude.However,the fatigue life of shot peening specimen is shorter than no peening one under higher total strain amplitude due to the ductility exhaustion and residual stress relax.There is exponential relation between strain fatigue life,which can be expressed by Coffin-Manson law.Through the present research work,the effects of total strain amplitude on the low cycle fatigue behaviors and fatigue life of 316 stainless steel with GNS surface layer have been investigated.The results of this work can be a guidance for the material in engineering industry. |
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