ICS-01: Fretting Fatigue Strength and Life Estimation Considering the Fretting Wear Process(ICS-I: INTERFACES AND CONTACT SURFACE MECHANICS)

In continuously coupled blade structures, fretting fatigue and wear have to be considered as supposed failure modes at the contact surface of the shroud cover, which is subject to steady contact pressure from centrifugal force and the vibratory load of the blade. We did unique fretting tests that modeled the structure of the shroud cover, where the vibratory load is only carried by the contact friction force, i.e., a type of friction. What was investigated in this study are fretting fatigue strength, wear rate, and friction characteristics, such as friction coefficient and slip-range of 12%-Cr steel blade material. The friction-type tests showed that fretting fatigue strength decreases with the contact pressure and a critical normal contact force exists under which fretting fatigue failure does not occur at any vibratory load. This differs from knowledge obtained through pad-type load carry tests that fretting fatigue strength decreases with the increase of contact pressure and that it almost saturates under a certain contact pressure. Our detailed observation in the friction-type tests clarified that this mechanism was the low contact pressure narrowing the contact area and a resulting high stress concentration at a local area. The fretting wear rate was explained by the dissipated energy rate per cycle obtained from the measured hysteresis loop between the relative slip range and the tangential contact force. This fretting wear rate per cycle is almost the same as the general adhesion wear rate when energy dissipation per cycle is high, and the former is smaller than the latter as the dissipated energy decreases. Finally, to prevent fretting fatigue and wear, we propose an evaluation design chart of the contact surface of the shroud cover based on our friction-type fretting tests.

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Experimental Validation of Fretting Fatigue Strength and Fretting Wear Rate at Contact Surface of Turbine-Blade-Shroud Cover

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4025833 ◽

2013 ◽

Vol 136 (4) ◽

Cited By ~ 1

Author(s):

Kunio Asai ◽

Takeshi Kudo ◽

Hideo Yoda

Keyword(s):

Fatigue Strength ◽

Wear Rate ◽

Contact Pressure ◽

Contact Force ◽

Contact Surface ◽

Fretting Fatigue ◽

Fretting Wear ◽

Dissipated Energy ◽

Normal Contact ◽

Vibratory Load

In continuously coupled blade structures, fretting fatigue and wear have to be considered as supposed failure modes at the contact surface of the shroud cover, which is subject to steady contact pressure from centrifugal force and the vibratory load of the blade. We did unique fretting tests that modeled the structure of the shroud cover, where the vibratory load is only carried by the contact friction force, i.e., a type of friction. What was investigated in this study are fretting fatigue strength, wear rate, and friction characteristics, such as friction coefficient and slip-range of 12%-Cr steel blade material. The friction-type tests showed that fretting fatigue strength decreases with the contact pressure and a critical normal contact force exists under which fretting fatigue failure does not occur at any vibratory load. This differs from knowledge obtained through pad-type load carry tests that fretting fatigue strength decreases with the increase of contact pressure and that it almost saturates under a certain contact pressure. Our detailed observation in the friction-type tests clarified that this mechanism was the low contact pressure narrowing the contact area and a resulting high stress concentration at a local area. The fretting wear rate was explained by the dissipated energy rate per cycle obtained from the measured hysteresis loop between the relative slip range and the tangential contact force. It was found that the fretting wear rate is smaller than the wear rate obtained by one-way sliding tests, and the former is much smaller than the latter as the dissipated energy decreases. Finally, to prevent fretting fatigue and wear, we propose an evaluation design chart of the contact surface of the shroud cover based on our friction-type fretting tests.

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ICS-05: Effect of Hydrogen Gas Environment on Fretting Fatigue Strength(ICS-I: INTERFACES AND CONTACT SURFACE MECHANICS)

The Proceedings of the JSME Materials and Processing Conference (M&P) ◽

10.1299/jsmeintmp.2005.4_1 ◽

2005 ◽

Vol 2005 (0) ◽

pp. 4

Author(s):

M. KUBOTA ◽

N. NOYAMA ◽

C. SAKAE ◽

Y. KONDO

Keyword(s):

Fatigue Strength ◽

Contact Surface ◽

Fretting Fatigue ◽

Hydrogen Gas ◽

Gas Environment ◽

Surface Mechanics

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Coupling fractal model for fretting wear on rough contact surfaces

Journal of Tribology ◽

10.1115/1.4049256 ◽

2020 ◽

pp. 1-32

Author(s):

Yi Wang ◽

Gang Liang ◽

Shuo LIU ◽

Yi Cui

Keyword(s):

Contact Surface ◽

Fractal Theory ◽

Three Dimensional ◽

Parameter Analysis ◽

Fretting Wear ◽

Wear Depth ◽

Contact Parameter ◽

Wear Process ◽

Actual Surface ◽

Fractal Parameters

Abstract In this paper, a fretting damage model based on fractal theory is proposed. The Weierstrass-Mandelbrot function of fractal theory is used to represent the rough contact surface, and a corresponding contact parameter analysis method is also established. Based on neural network algorithm, the values of fractal parameters are fitted, and the fitting accuracy has been greatly improved compared with traditional methods. According to the fractal parameters of the actual surface, the fretting wear process of the rough contact surface is analyzed based on theory of adhesive and three body abrasive wear. A generic program for the analysis of three-dimensional fretting wear problems is also proposed. Compared with material tests, the prediction error of fretting wear simulation model is 13.4% for wear depth and 16.7% and 3.9% for width and length of wear scar in stable wear stage. The prediction results show that the model can be applied to the prediction of the actual three-dimensional fretting wear model.

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Multiaxial High Cycle Fretting Fatigue

MATEC Web of Conferences ◽

10.1051/matecconf/201930002002 ◽

2019 ◽

Vol 300 ◽

pp. 02002

Author(s):

José Alexander Araújo ◽

Gabriel Magalhães Juvenal Almeida ◽

Fábio Comes Castro ◽

Raphael Araújo Cardoso

Keyword(s):

Fretting Fatigue ◽

Accurate Estimate ◽

Multiaxial Fatigue ◽

Fretting Wear ◽

Critical Plane ◽

Life Estimation ◽

Wide Range ◽

Tools And Techniques ◽

Critical Direction ◽

High Cycle Fretting Fatigue

The aim of this work is to show that multiaxial fatigue can be successfully adpted to model fretting problems. For instance, the paper presents (i) the critical direction method, as an alternative to the critical plane concept, to model the crack initiation path under fretting conditions and (ii) studies on size effects considering the influence of incorporating fretting wear on the life estimation. A wide range of new data generated by a two actuators fretting fatigue rig considering Al 7050-T7451 and of Ti-6Al-4V aeronautical alloys is produced to validate these analyses. It is shown that, the development of appropriate tools and techniques to incorporate the particularities of the fretting phenomenon into the multiaxial fatigue problem allow an accurate estimate of the fretting fatigue resistance/life in the medium high cycle regime. Such tools and techniques can be extended to the design of other mechanical components under similar stress enviroments.

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