Papers by Author: Er Yu Shao

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Authors: Ying Xia Yu, Bo Lin He, Er Yu Shao
Abstract: The contact fatigue tests were carried out using three kind of steel(45, 42CrMo, 40CrNi2Mo) which were quenched and tempered to the same medium hardness(HRC37±1). The experimental equipment is JPM-1 type contact fatigue tester. During the experiment process, the contact stress is 1600MPa and the surface roughness is 0.4 um. The crack initiation and the crack propagation direction were observed by using SEM. The contact fatigue failure mechanism was also analyzed. The experimental results were analyzed by using Weibull distribution. The experimental results show that the contact fatigue crack was initiated in the roller surface. With increasing of the cycle, the initiated crack propagates into subsurface and becomes to pitting. The pitting becomes bigger and bigger and leads to failure finally. The maximum shear stress is the main driving force for the crack propagation. The contact fatigue life increases in sequence of 45, 42CrMo, 40CrNi2Mo. The contact fatigue life has the relationship with the shearing resistant stress Тk. About the same carbon content, the value of the shearing resistant stress Тk becomes greater with increasing the alloying elements. The best material used for making heavy duty gear is 40CrNi2Mo steel.
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Authors: Bo Lin He, Ying Xia Yu, Er Yu Shao
Abstract: The effect of undissolved ferrite amount on bending fatigue properties and failure mechanism were studied by using 42CrMo steel with subcritical quenching process The amount of undissolved ferrite were 0%, 10% and 15%, respectively. The hardness of the specimen was treated to medium hardness. The experimental results show that the existence of undissolved ferrite can not only change the microstructure, but also increase the bending fatigue life. The bending fatigue life elongates with increasing of amounts of undissolved ferrite. The grains can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased because of undissolved spheroidal carbide. The martensite and carbide can also be changed using subcritical quenching process. Stress relaxation due to the move of dislocations inside the ferrite and the promotion of strength due to occurring of plastic deformation and enwinded dislocations are main reasons of improving the bending fatigue life. The bending fatigue life elongates with the increase of amounts of undissolved ferrite before the amount of undissolved ferrite reaches 10%. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the bending fatigue life will be the longest.
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Authors: Bo Lin He, Ying Xia Yu, Er Yu Shao
Abstract: The effect of undissolved ferrite amount on impact fatigue properties and failure mechanism were studied by using 42CrMo steel with subcritical quenching process The amount of undissolved ferrite were 0%, 10% and 15%, respectively. The experimental results show that the existence of undissolved ferrite can not only change the microstructure, but also increase the impact fatigue life The impact fatigue life elongates with increasing of amounts of undissolved ferrite The grain can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased because of undissolved spheroidal carbide. The martensite and carbide form can also be changed by using subcritical quenching process The stress relaxation due to the moving of dislocations inside the ferrite and the promotion of strength due to occurring of plastic deformation and the enwinded dislocations are main reasons of improving the impact fatigue life. The impact fatigue life elongates with the increase of amounts of undissolved ferrite before the amount of undissolved ferrite reaches 10%. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the impact fatigue life will be the longest.
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