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The fatigue and wear characteristics of AISI VIM-VAR M50 steel were evaluated using three fully formulated synthetic ester-based lubricants. Tests were conducted using a rolling contact fatigue test rig of the ball-on-rod type at a cyclic maximum hertzian stress level of 4.83 GPa (700 klbf in −2 ) and temperatures of 23°C (74°F) and 177°C (350°F). The lubricants evaluated included three polyol...
This paper describes laboratory simulation of rolling contact fatigue (RCF) defects using a rail/wheel rolling contact testing machine and its test results. The results have confirmed the findings about the behaviour of RCF defects obtained from earlier experiments. Multiple regression analysis of test results has shown that the correlation between tangential force and longitudinal residual stress...
The paper presents the results of the stress analysis of rail rolling contact fatigue cracks. The basis of the model used in the analysis is the finite element approach which enables the crack tip stress environment to be described by the fracture mechanics crack tip stress intensity factors (SIFs) K I , K II , and K III . The results for a semi-elliptical crack...
The fatigue and wear characteristics of AISI VIM-VAR M50 steel were evaluated using two high-temperature synthetic turbine engine lubricants. Rolling contact fatigue (RCF) tests were conducted on a ball-on-rod type rig at a cyclic Hertzian contact stress of 4.8 GPa (700 ksi) and temperatures of 177°C (350°F) and 274°C (525°F). The two lubricants tested included a five-ring polyphenylether (MIL-L-87100,...
The surface-initiated rolling contact fatigue behavior of two pearlitic and three bainitic steels has been investigated over a contact pressure range of 850 to 2300 MPa under water-lubricated conditions. The relationship between rolling contact fatigue life and contact pressure is nonlinear, with a transition in behavior occurring close to the theoretical shakedown limit. Above the limit, failure...
This study is aimed at the deterioration of rolling contact fatigue (RCF) life of pearlitic rail steel, under rolling-sliding conditions, where the wet phase of the test is preceded by different numbers of dry cycles. It is shown that initial dry cycles above a critical number causes sudden and significant deterioration in RCF life. This effect has been explained using the argument of plastic strain...
In the present paper, prediction of the coating fatigue behaviour of coated cylindrical specimens during the ball-on-rod rolling contact fatigue (RCF) test is introduced. The prediction is based on a non-linear finite element method (FEM) simulation, considering analytically the experimentally determined coating fatigue properties. During the RCF test, coated rods are subjected to rolling contact...
The effect of hard coatings on the fatigue life of rolling elements subject to cyclic concentrated contact loading (such as bearing races or gears) is studied theoretically. Approximate analytical formulae are derived that can be used to estimate the coating thickness required to protect the substrate effectively from the small-scale contact stress spikes produced by surface roughness, and thus prevent...
A non-destructive experimental approach using an X-ray diffraction technique was used to investigate the generation of residual stresses in thermally sprayed rolling elements. The rolling elements were detonation gun coated balls and high velocity oxy-fuel coated cones. A modified four ball machine was used to perform rolling contact fatigue (RCF) tests on tungsten carbide cobalt (WC-Co) coated samples...
With the increase of speeds and axle-loads in railway transportation, the fatigue life of the wheels has become an important issue with respect to economy and safety. A deeper understanding of the fatigue mechanisms and a better prediction of lifetimes should be of interest to both manufacturers and operators.In this paper, a refined equivalent-stress criterion is developed and is implemented in a...
The rolling contact fatigue and wear characteristics of uncoated and diamond-like carbon coated VIM-VAR M50 bearing steel were investigated at room temperature and 177°C (350°F) and a Hertzian stress level of 4.8 GPa (700 ksi). The coatings were deposited via ion beam enhanced deposition and were approximately 33 nm thick. Rolling fatigue and wear tests were conducted using a ball-on-rod type tester...
The rolling contact fatigue (RCF) behaviour of thermally sprayed WC-Co coatings with nominal compositions of WC-12%Co, WC-10%Co-4%Cr and WC-17%Co was studied with a two-roll configuration roll-against-roll testing apparatus under 420-600 MPa Hertzian contact stresses in unlubricated pure rolling conditions. The coatings were prepared by atmospheric plasma spray (APS) and two high-velocity oxyfuel...
This experimental study describes the Rolling Contact Fatigue (RCF) performance and the failure mechanisms of plasma sprayed tungsten carbide cobalt (WC-15%Co) coatings. The advancements of plasma spray coatings due to higher velocity and temperature of the impacting lamella call for investigations into new applications. One possible application is the rolling element bearing. A modified four ball...
The use of silicon nitride applied to rolling element bearings shows some practical advantages over traditional bearing steels. The contribution of this present study is to provide understanding of surface crack defect characteristics and the subsequent rolling fatigue modes of failure. Surface defects such as pressing faults and ring cracks are characterised using light microscopy. Experimental bench...
A study into effects of surface defects on rolling contact fatigue of 60/40 brass under a maximum contact pressure of 600 MPa and a slide-roll ratio of -1% was undertaken on a twin-disc rolling-sliding test machine. Furrows (transverse and longitudinal) and dents (conical and diamond) were artificially introduced into a disc surface, and surface microcracks and pits were monitored by means of surface...
This experimental study addresses the failure modes of plasma sprayed coatings in rolling contact. A high velocity plasma spraying system was used to deposit WC-15%Co coatings on the surface of 15 mm diameter 440-C bearing steel cones. These coatings were deposited in two different thickness. Rolling contact fatigue (RCF) tests were conducted using a modified four ball machine in conventional steel...
Ball-on-rod rolling contact fatigue experiments were performed using M50-M50 all-steel and Si 3 N 4 -M50 hybrid components, respectively. Experiments were performed using a jet turbine engine lubricant in the as-received condition or with particulate contaminants added. The added particulate contaminants were Arizona test dust or glycothermally synthesized α-Al 2 O 3 ...
The influence of ring crack location within the contact path on rolling contact fatigue failure has been studied using numerical fracture analysis. The numerical calculations are based on a three-dimensional model for the ring crack propagation. The ring crack is considered as a conic shape with a curved line as the crack front. The rolling contact loading is simulated by repeated Hertzian point contact...
This paper presents an experimental study of the influences of ring crack location within the contact path on the rolling contact fatigue failure. The rolling contact tests are performed on silicon nitride/steel elements. Silicon nitride ball surfaces are examined before testing using a dye-penetrant technique and light microscopy. The surfaces during testing, post-test and after failure are examined...
Silicon nitride has been found to have the optimum combination of properties which are suitable for rolling element bearing applications to withstand high loads, severe environments, and high speeds. Surface ring cracks are difficult to detect but are found on the surface of silicon nitride balls. These ring crack defects decrease the rolling contact fatigue life considerably. This paper presents...
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