The Influence Of The Corrosion On The Fatigue Life And Crack Growth Rate Of The Low-Carbon Steels

That metal component are failed because of the fatigue failure is one of the most popular and common form. The low-carbon steels are used widely in the engineering. They are corroded and damaged easily because of the complex service environment. And the local failure often leads to a huge loss of catastrophic damage. So it will have the great practical significance that the influence of the corrosion on the fatigue life and crack growth rate of the low-carbon steels.Based on the research on fatigue cracks and crack propagation in the vast literature, a rapid electrochemical corrosion is used to simulate the corrosion the low carbon steels in the natural environment, and to make the fatigue and smooth specimens and compact tension specimens. And their rate of corrosion in different fatigue life and the behavior of crack growth are researched. The specific studies and results are as followings:The rapid development of the electrochemical corrosion testing device developed in this paper can simulate corrosion of the low-carbon steels under natural conditions in a short time. The treatment technology of "chrome-automatic painting" on the surface of the corroded specimens will make crack more clear to be observed and recorded in the test. The results prove that these methods are effective.The crack growth formula (da)/(dN)=Ca~k proposed can describe the fatigue crack growth law of the low carbon substrate under various corrosion rates.Corrosion rate has little effect on the fatigue crack growth. The plastic zone appears at the crack tip during the crack growing. Coarse grain fibrous tissue in plastic zone promotes the production of Oxide and appears the phenomenon of the fatigue crack closure, and plastic deformation appears because of corrosion. All of above result in the increase of the plastic extension amount at the crack tip and the extent of crack closure. Meantime, the resistance of fatigue fracture is improved by the roughness of the crack surface which caused by the corrosion. The little effect of the corrosion rates on the fatigue crack growth rate is the result of above factors.Experimental research on fatigue life and crack growth shows that crack initiation life is the main part of Fatigue Life,can each to 90%,while crack propagation life is a very little part. Corrosion has great influence on crack initiation life and no obvious effect on crack Growth Rate...