Fatigue Performance and Residual Stress of Carburized Gear Steels Part II: Fatigue Performance

2008 ◽  
Vol 1 (1) ◽  
pp. 709-717 ◽  
Author(s):  
Justin John ◽  
Keyu Li ◽  
Huaxin Li
Keyword(s):  
Residual Stress ◽  
Fatigue Performance ◽  
Carburized Gear ◽  
Gear Steels

scholarly journals Bending Fatigue Behaviour and Fatigue Endurance Limit Prediction of 20Cr2Ni4A Gear Steel after the Ultrasonic Surface Rolling Process

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2516
Author(s):  
Zhiyuan Wang ◽  
Yangfei Huang ◽  
Zhiguo Xing ◽  
Haidou Wang ◽  
Debin Shan ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Properties ◽  
Cross Section ◽  
Rolling Process ◽  
Fatigue Performance ◽  
Material Surface ◽  
Bending Fatigue ◽  
Surface Strengthening ◽  
Gear Steel ◽  
Carburized Gear

To study the effect of the surface properties on the bending fatigue performance of heavy-duty gear steel, the authors of this paper used the ultrasonic surface rolling process (USRP) to strengthen 20Cr2Ni4A carburized gear steel. USRP is a novel technique in which the ultrasonic technology is incorporated into the concept of conventional deep rolling. In this study, we illustrated how the surface properties and cross-section mechanical property influence the three-point bending fatigue life of the samples before and after USRP treatment. At the same time, the predicted failure probability-stress-number of cycles (P-S-N) curve was drawn, and the fatigue fracture was analysed. The results show that the fatigue limit increased from 651.36 MPa to 918.88 MPa after USRP treatment. The fatigue source is mainly from the sample interior or surface scratches, and the fatigue performance is positively correlated with the results of the material surface roughness, surface residual stress and surface hardness. At the same time, combined with the change in the phase structure, dislocation structure, residual stress and hardness of the cross section of the material, it is found that the USRP process turns the steel into a gradient material with five layers. Finally, the coupling mechanism between the ultrasonic surface strengthening deformation layer and the carburized layer of 20Cr2Ni4A carburized gear steel is presented, and the grain structure distribution diagram of the section of the 20Cr2Ni4A model after surface strengthening treatment was simulated. The mechanism that influenced the fatigue performance after USRP treatment is explained from the perspectives of the surface and cross section of the samples.

Evaluation of contact fatigue life of a wind turbine carburized gear considering gradients of mechanical properties

2018 ◽  
Vol 28 (8) ◽  
pp. 1170-1190 ◽  
Author(s):  
Wei Wang ◽  
Huaiju Liu ◽  
Caichao Zhu ◽  
Zhangdong Sun
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Heavy Duty ◽  
Initial Residual Stress ◽  
Contact Fatigue Life ◽  
Carburized Gear ◽  
Load Conditions

Case hardening processes such as carburizing are extensively applied in heavy-duty gears used in wind turbines, ships, high-speed rails, etc. Contact fatigue failure occurs commonly in engineering practice, thus reduces reliabilities of those machines. Rolling contact fatigue life of a carburized gear is influenced by factors such as the gradients of mechanical properties and profile of initial residual stress. In this regard, the study of contact fatigue life of carburized gears should be conducted with the consideration of those aspects. In this study, a finite element elastic–plastic contact model of a carburized gear is developed which takes the gradients of hardness and initial residual stress into account. Initial residual stress distribution and the hardness profile along the depth are obtained through experimental measurements. The effect of the hardness gradient is reflected by the gradients of yield strength and fatigue parameters. The modified Fatemi–Socie strain-life criterion is used to estimate the rolling contact fatigue life of the heavy-duty carburized gear. Numerical results reveal that according to the Fatemi–Socie fatigue life criterion, rolling contact fatigue failure of the carburized gear will first initiate at subsurface rather than surface. Compared with the un-carburized gear, the rolling contact fatigue lives of the carburized gear under all load conditions are significantly improved. Under heavy load conditions, the carburized layer significantly reduces the fatigue damage mainly due to the benefit to inhibit the accumulation of plasticity. Influence of the residual stress is also investigated. Under the nominal load condition, compared with the residual stress-free case, the existence of the tensile residual stress causes remarkable deterioration of the rolling contact fatigue life while the compressive residual stress with the same magnitude leads to a moderate growth of the rolling contact fatigue life. As the load becomes heavier when plasticity becomes notable, the influence of the initial residual stress on the life is somewhat weakened.

Analysis of the Fatigue Performance of Thick T-Joint Samples Considering Residual Stresses

2016 ◽  
Author(s):  
J. A. Esnaola ◽  
I. Ulacia ◽  
D. Ugarte ◽  
A. Lopez-Jauregi ◽  
I. Torca ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Life Prediction ◽  
Fatigue Performance ◽  
T Joints ◽  
Thick Plates ◽  
Stress Load ◽  
Real Value ◽  
Number Of Passes ◽  
Different Thickness

Residual stress (RS) pattern of thick T-joint welds, which directly affects fatigue life, varies considerably depending on the thickness and number of passes. Nowadays, most approaches to predict fatigue life do not consider RS real value due to the difficulty of estimating them, hence, they tend to be conservatives. However, recent works have demonstrated that considering RS the conservative error in life prediction can be reduced down to around 15%. In the present work, the fatigue performance of multipass T-joints of S275JR plates for a thickness range from 20 to 60mm is evaluated considering RS. It is observed that maximum RS value for thick plates decreases progressively (down to 66% of yield stress). Consequently, fatigue performance of different thickness T-joint samples subjected to the same stress load cycles varies considerably in the HCF regime.

scholarly journals Pitting and Bending Fatigue Evaluations of a New Case-Carburized Gear Steel

2007 ◽  
Author(s):  
Timothy Krantz ◽  
Brian Tufts
Keyword(s):  
Power Density ◽  
Fatigue Testing ◽  
Surface Hardness ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Surface Fatigue ◽  
Gear Steel ◽  
Single Tooth ◽  
Carburized Gear ◽  
Gear Steels

The power density of a gearbox is an important consideration for many applications and is especially important for gearboxes used on aircraft. One approach to improving power density of gearing is to improve the steel properties by design of the alloy. The alloy tested in this work was designed to be case-carburized with surface hardness of Rockwell C66 after hardening. Test gear performance was evaluated using surface fatigue tests and single-tooth bending fatigue tests. The performance of gears made from the new alloy was compared to the performance of gears made from two alloys currently used for aviation gearing. The new alloy exhibited significantly better performance in surface fatigue testing, demonstrating the value of the improved properties in the case layer. However, the alloy exhibited lesser performance in single-tooth bending fatigue testing. The fracture toughness of the tested gears was insufficient for use in aircraft applications as judged by the behavior exhibited during the single tooth bending tests. This study quantified the performance of the new alloy and has provided guidance for the design and development of next generation gear steels.

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