Investigation for Small Shear-Mode Fatigue Cracks in Bearing Steels

2013 ◽  
Vol 750 ◽  
pp. 236-239
Author(s):  
Saburo Okazaki ◽  
Atsushi Kusaba ◽  
Hisao Matsunaga ◽  
Masahiro Endo
Keyword(s):  
Fatigue Crack ◽  
High Speed ◽  
Fatigue Testing ◽  
Fatigue Cracks ◽  
Testing Machine ◽  
Rolling Contact ◽  
Installation Space ◽  
Shear Mode ◽  
Testing Method ◽  
Small Shear

Flaking and spalling caused by rolling contact fatigue associate with a small crack, and a special testing method and machine are required to study the small fatigue crack behavior under shear mode loading. It was found by authors that the behaviors of small shear-mode fatigue cracks from the inclusions and the artificial defects could be successfully observed by applying the fully-reversed torsion coupled with static axial compressive stress. However, the servo-hydraulic fatigue testing machine is quite expensive for purchase and maintenance, and large installation space is necessary for the hydraulic and cooling systems. Moreover, the presence of axial compression significantly lowers the frequency of torsional loading, which consequently results in low testing speed. In this study, a cost-effective, space-saving and high-speed fatigue testing method was newly proposed, and the shear-mode fatigue crack growth tests were carried out by using the developed machine. Based on the obtained experimental data, the potential of the new testing machine is discussed.

A New Fatigue Testing Machine for Investigating the Behavior of Small Shear-Mode Fatigue Cracks

2016 ◽  
Vol 40 (3) ◽  
pp. 1065-1073 ◽  
Author(s):  
M. Endo ◽  
S. Okazaki ◽  
H. Matsunaga ◽  
S. Moriyama ◽  
K. Munaoka ◽  
...  
Keyword(s):  
Fatigue Testing ◽  
Fatigue Cracks ◽  
Testing Machine ◽  
Shear Mode ◽  
Small Shear

DESIGNING OF A TESTING MACHINE FOR SHEAR-MODE FATIGUE CRACK GROWTH

2012 ◽  
Vol 06 ◽  
pp. 318-323
Author(s):  
A. KUSABA ◽  
S. OKAZAKI ◽  
M. ENDO ◽  
K. YANASE
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
High Performance ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Shear Mode ◽  
Mode Iii ◽  
Research Activity ◽  
Testing Speed

As recognized, flaking-type failure is one of the serious problems for railroad tracks and bearings. In essence, flaking-type failure is closely related to the growth of the shear-mode (Mode-II and Mode-III) fatigue crack. In our research group, it is demonstrated that a shear-mode fatigue crack can be reproduced for cylindrical specimens by applying the cyclic torsion in the presence of the static axial compressive stress. However, a biaxial servo-hydraulic fatigue testing machine is quite expensive to purchase and costly to maintain. The low testing speed (about 10Hz) of the testing machine further aggravates the situation. As a result, study on shear-mode fatigue crack growth is still in the nascent stage. To overcome the difficulties mentioned above, in this research activity, we developed a high-performance and cost-effective testing machine to reproduce the shear-mode fatigue crack growth by improving the available resonance-type torsion fatigue testing machine. The primary advantage of using the resonance-type torsion fatigue testing machine is cost-efficiency. In addition, the testing speed effectively can be improved, in comparison with that of a biaxial servo-hydraulic fatigue testing machine. By utilizing the newly-designed testing machine, we have demonstrated that we can successfully reproduce the shear-mode fatigue crack.

scholarly journals Fatigue crack initiation and propagation of 100Cr6 steel under torsional loading in very high cycle regime

2018 ◽  
Vol 165 ◽  
pp. 20003
Author(s):  
Hongqian Xue ◽  
Tao Gao ◽  
Zhidan Sun ◽  
Xianjie Zhang
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Testing ◽  
Fatigue Cracks ◽  
Maximum Shear Stress ◽  
Testing Machine ◽  
Fatigue Crack Initiation ◽  
Longitudinal Direction ◽  
Torsional Fatigue ◽  
Very High

Cyclic torsional fatigue properties of a high strength steel 100Cr6 are investigated using an ultrasonic torsional fatigue testing machine, and the results are compared with those obtained with fatigue tests under axial loading. Fatigue crack initiation and growth under torsion loading are observed in the very high cycle regime. Results show that fatigue cracks initiated from specimen surface as well as subsurface inclusions under torsion loading. However, subsurface MnS inclusions play a dominant role in crack initiation under torsion loading in the very high cycle regime. The initiation and early propagation of fatigue cracks are mostly controlled by the direction of the maximum shear stress. For surface crack initiation, cracks initiated in parallel to the longitudinal direction of the specimens. Once the shear crack propagated to a crack length of about 20-30 μm, crack branched to the angle close to the direction perpendicular to the remote maximum principal stresses. As for the subsurface fatigue crack initiation, the cracks parallel to the longitudinal direction of the specimens could not be observed, and crack propagation followed a spiral shape on a plane with an orientation of 45° with respect to the loading direction, which corresponds to the maximum principal stress plane.

Surface Durability of Spur Gears at Hertzian Stresses Over Shakedown Limit

1974 ◽  
Vol 96 (2) ◽  
pp. 359-372 ◽  
Author(s):  
Akira Ishibashi ◽  
Taku Ueno ◽  
Shigetada Tanaka
Keyword(s):  
Fatigue Testing ◽  
Testing Machine ◽  
Carbon Steels ◽  
Rolling Contact ◽  
Hertzian Contact ◽  
Load Testing ◽  
Short Period ◽  
Hertzian Contact Stress ◽  
Surface Durability ◽  
Shakedown Limit

Using a new type of gear-load testing machine and a disk-type rolling fatigue testing machine designed and made by the authors, the upper limits of Hertzian contact stress allowable on rolling contact surfaces were investigated. It was shown conclusively that gears and rollers made of soft carbon steels could be rotated beyond 108 revolutions at Hertzian stresses over shakedown limit (≈ 0.4 HB). In the case of gears, pits having a pitting area ratio of 0.04 percent occurred during 1.16 × 108 rotations at a Hertzian stress of 0.50 HB. However, no pitting occurred on the roller rotated through 1.20 × 108 revolutions at a Hertzian stress of 0.71 HB, although appreciable changes in texture were observed at the subsurface. In order to rotate gears or rollers at Hertzian stresses over shakedown limit, their surface must either be very smooth initially or after a short period of running, and an oil film must be formed between contacting surfaces.

Effect of Slag Composition on Fatigue Life of High Speed Wheel Steel

2013 ◽  
Vol 675 ◽  
pp. 264-269
Author(s):  
Yu Tang
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Oxide Inclusion ◽  
Wheel Steel ◽  
Al2o3 Content ◽  
Confocal Laser ◽  
Composition Analysis ◽  
In Situ Observation

In order to improve fatigue life of wheel steel, secondary-refining process was done with Al-deoxidation and slag of high basicity, high Al2O3 content and low oxidizing property. By morphology observation and composition analysis with FESEM, it is found that during LF-VD process, by slag-steel-inclusion interaction, Al2O3 inclusions could transform to MgO-Al2O3 spinel, and later on to CaO-MgO-Al2O3 inclusions, which are inclined to be eliminated by floatation, lowering T[O] content to 0.0007%, enhancing fatigue life of wheel steel. By In-Situ observation with CONFOCAL laser scanning microscope, it is found that MnS precipitates during solidification process, which would core oxide inclusion to form MnS-oxide complex inclusion, contributing to fatigue life improvement of wheel steel. By INSTRON fatigue testing machine, it is found that by successful inclusion control, tested samples achieve ultra-high cycle of 108 above, realizing experimental purpose of improving fatigue life of wheel steel, boosting domestic production process of CRH high speed wheel steel.

Effect of Lubricant on Surface Rolling Contact Fatigue Cracks

2010 ◽  
Vol 97-101 ◽  
pp. 793-796 ◽  
Author(s):  
Khalil Farhangdoost ◽  
Mohammad Kavoosi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Cracks ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Hertzian Contact ◽  
Element Analysis ◽  
Crack Face ◽  
Hertzian Contact Stress ◽  
Model Of Friction

This study performed the finite element analysis of the cycle of stress intensity factors at the surface initiated rolling contact fatigue crack tip under Hertzian contact stress including an accurate model of friction between the faces of the crack and the effect of fluid inside the crack. A two-dimensional model of a rolling contact fatigue crack has been developed with FRANC-2D software. The model includes the effect of Coulomb friction between the faces of the crack. The fluid in the crack was assumed not only to lubricate the crack faces and reduce the crack face friction coefficient but also to generate a pressure.

Development of a New Fatigue Testing Machine for High Frequency Fatigue Damage Assessment

2013 ◽  
Author(s):  
Naoki Osawa ◽  
Tetsuya Nakamura ◽  
Norio Yamamoto ◽  
Junji Sawamura
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Fatigue Testing ◽  
Low Cost ◽  
Plate Thickness ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Frequency Effect ◽  
Wave Load ◽  
Out Of Plane

A new simple fatigue testing machine, which can carry out fast and low-cost fatigue tests of welded joints subject to wave with high frequency vibration, has been developed. This machine is designed for plate bending type fatigue tests, and wave load is applied by using motors with eccentric mass. Springing vibration is superimposed by attaching an additional vibrator to the test specimen, and whipping vibration is superimposed by an intermittent hammering. Fatigue tests which simulate springing and whipping by a conventional servo-type fatigue testing machines are very expensive and use a large amount of electricity. If one uses these conventional machines, it is difficult to simulate superimposed stress wave forms at high speed, and it takes long hours of testing to examine the high frequency effect. In contrast, it is found that fatigue tests can be carried out in fast, i.e. waves with 10Hz or higher frequency for out-of-plane gusset welded joint specimens with 12mm plate thickness by using the developed machine. The electricity to be used for fatigue tests could be minimal, for example one thousandth of that needed for conventional machines. These results demonstrate the superiority of the developed machine.

Numerical Simulation and Result Interpretation of Large Scale Fatigue Testing of Tubular X-Joint Close to Resonance Frequency

2019 ◽  
Author(s):  
Philippe Thibaux ◽  
Jeroen Van Wittenberghe ◽  
Maarten Van Poucke
Keyword(s):  
Resonance Frequency ◽  
Large Scale ◽  
Fatigue Testing ◽  
Hot Spot ◽  
Fatigue Cracks ◽  
Probability Of Failure ◽  
Local Geometry ◽  
Testing Method ◽  
Resonance Frequencies ◽  
Resonance Test

Abstract Fatigue testing of tubular joints is normally performed at a low frequency, making the tests typically very long. Recently, a new testing method has been developed where a specimen is excited close to its resonance frequency, making it possible to achieve testing frequencies higher than 20Hz. In the present investigations, different nodes representing an X-joint (diameter of the brace 711mm, wall thickness 20mm) were tested until failure in the resonance test set-up. The new testing method allows to load the full circumference of the weld with a nominal stress following an elliptic profile, such that the fatigue cracks can be initiated at many locations around the weld with similar probability of failure. The paper will present the strategy for the design of the specimen, aiming to achieve similar resonance frequencies for in-plane and out-of-plane bending and similar probability of failure along the welds. After reception of the specimen and testing, new finite element simulations were run and compared to the experimental response of the specimen. The influence of different aspect of the modelling will be discussed, with their influence on the identified resonance frequency and strain gauge readings. The investigation proves that it is possible to obtain a reasonably homogeneous hot spot values along the weld, resulting in the initiation of cracks not anymore dictated by the hot spot values, but by the local geometry of the weld.

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