Research On Fatigue Performance Of 304 Stainless Steel With Different Rolling Quantity

304 stainless steel has excellent comprehensive properties and has become one of the most widely used materials in aviation,military and other fields..In the research of fatigue failure of 304 stainless steel,many achievements have been made in many aspects,but there are not many related literatures and reports in the research of different rolling quantities.Therefore,this article takes 304 stainless steel with different rolling volume as the research object.Firstly,by analyzing the stress-strain curve from tensile tests,fracture section observations and the numerical simulation combined with the Tyson polygon method,the static strength of 304 stainless steel with different grains was explored.Then,the paper had made fatigue tests and TEM observations to figure out the internal factors which influenced cycle-stress curves of304 stainless steel and fatigue strength from different perspectives.In addition,from finite element analysis,stress-life curves of steel samples with various kinds of defects had been predicted.finally,the method of combining fracture mechanics and fracture analysis was used to explore the difference in fatigue strength of 304 stainless steel from experimental observation and theoretical calculation.This paper focused on fatigue characteristic of 304 stainless steel with different grain sizes by mechanical basic experiments,micro-observation and finite element simulation,conclusions have drawn as follows:(1)The rolled 304 stainless steel produces a large number of fine grains,which strengthens the internal dislocations of the material and increases the strength of the material.The Tyson polygon and cohesion model can simulate the stretching process and crack initiation of the material.(2)Due to the different Schmid factors between different grains,the formation of a large number of dislocation cells and deformation twins forms a barrier in the direction of the dislocation movement,which hinders the movement of the dislocation and makes the degree of rolling increase;(3)With Goodman correction as the leading factor,the fatigue life SN curves of the initial,30% and 70% rolled stainless steels in the three states of stress ratios of 0.1,0.2 and 0.3 are obtained.It is observed that the tip stress intensity factor will change during the fatigue crack growth process.Under different conditions of rapid expansion and stable expansion,the distribution of stress intensity factors is different.