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Research Papers: Applications

Experimental and Numerical Investigation of Torsion Fatigue of Bearing Steel

[+] Author and Article Information
John A. R. Bomidi

Graduate Research Assistant
e-mail: jbomidi@purdue.edu

Nick Weinzapfel

Graduate Research Assistant
e-mail: weinzapf@purdue.edu

Trevor Slack

Research Assistant
e-mail: tslack@purdue.edu

Sina Mobasher Moghaddam

Graduate Research Assistant
e-mail: smobashe@purdue.edu

Farshid Sadeghi

Cummins Professor of Mechanical Engineering
Fellow ASME, STLE
e-mail: sadeghi@ecn.purdue.edu
School of Mechanical Engineering,
Purdue University,
West Lafayette, IN 47907

Alexander Liebel

e-mail: liebeaex@schaeffler.com

Joerg Weber

e-mail: joerg.weber@schaeffler.com
Bearing Fundamentals, Schaeffler Technologies AG & Co. KG,
Herzogenaurach 91074, Germany

Thomas Kreis

Corporate Fundamentals and Long Term Quality,
Schaeffler Technologies AG & Co. KG,
Herzogenaurach 91074, Germany
e-mail: thomas.kreis@schaeffler.com

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the Journal of Tribology. Manuscript received October 14, 2012; final manuscript received January 30, 2013; published online April 29, 2013. Assoc. Editor: Robert L. Jackson.

J. Tribol 135(3), 031103 (Apr 29, 2013) (13 pages) Paper No: TRIB-12-1179; doi: 10.1115/1.4023807 History: Received October 14, 2012; Revised January 30, 2013

This paper presents the results of torsion fatigue of widely used bearing steels (through hardening with bainite, martensite heat treatments, and case hardened). An MTS torsion fatigue test rig (TFTR) was modified with custom mechanical grips and used to evaluate torsional fatigue life and failure mechanism of bearing steel specimen. Tests were conducted on the TFTR to determine the ultimate strength in shear (Sus) and stress cycle (S-N) results. Evaluation of the fatigue specimens in the high cycle regime indicates shear driven crack initiation followed by normal stress driven propagation, resulting in a helical crack pattern. A 3D finite element model was then developed to investigate fatigue damage in torsion specimen and replicate the observed fatigue failure mechanism for crack initiation and propagation. In the numerical model, continuum damage mechanics (CDM) were employed in a randomly generated 3D Voronoi tessellated mesh of the specimen to provide unstructured, nonplanar, interelement, and inter/transgranular paths for fatigue damage accumulation and crack evolution as observed in micrographs of specimen. Additionally, a new damage evolution procedure was implemented to capture the change in fatigue failure mechanism from shear to normal stress assisted crack growth. The progression of fatigue failure and the stress-life results obtained from the fatigue damage model are in good agreement with the experimental results. The fatigue damage model was also used to assess the influence of topological microstructure randomness accompanied by material inhomogeneity and defects on fatigue life dispersion.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Torsion fatigue test rig

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Fig. 2

Custom mechanical grip design

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Fig. 4

Optical micrograph of steel A bearing steel revealing grain structure (image courtesy of Schaeffler Technologies AG & Co. KG).

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Fig. 5

Shear stress experienced by steel A bearing steel specimen under monotonic angular displacement

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Fig. 6

S-N data for variants of through hardened and case hardened bearing steels

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Fig. 7

Observed fracture surfaces from static and fatigue tests for steel A bearing steel

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Fig. 8

Stresses due to torque on a circular cross section. (a) Magnitude and direction of the shear stress and (b) Mohr's circle for pure shear

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Fig. 9

Detailed images of a high cycle torsion fatigue specimen

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Fig. 10

Shear stress and angular displacement during a fatigue test

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Fig. 11

SEM micrographs of a high cycle torsion fatigue specimen (image courtesy of Schaeffler Technologies AG & Co. KG)

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Fig. 12

Microstructure topology model of torsion specimen

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Fig. 13

A Voronoi “grain” with (a) faces divided into triangles, which form the bases of the tetrahedra shown in (b) an exploded view

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Fig. 14

Constraint for the application of torque in the finite element model

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Fig. 15

Stress contours (a) Von Mises, (b) S12, and (c) S13 shown in order on a cut section of the torsion specimen model

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Fig. 16

S-N data for steel A bearing steel from the experiments

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Fig. 17

Predicted fatigue life and the experimental S-N curve

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Fig. 18

Sequence of fatigue crack patterns observed (a)–(d); (e) cut section of the torsion model

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Fig. 19

A double helical crack observed for a torsion specimen in a high cycle fatigue experiment

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Fig. 20

Fatigue life versus number of failed weak planes

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Fig. 21

Weibull probability of predicted fatigue lives for 43 microstructure models with homogeneous material properties (E = 200 GPa, ν = 0.3)

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Fig. 22

Gaussian distribution of elastic modulus applied to grains of the microstructure model

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Fig. 23

Comparison of the Weibull probability of the predicted fatigue lives for homogenous and heterogeneous elastic modulus

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Fig. 24

(a) Comparison of the Weibull probability of the predicted fatigue lives for pristine torsion specimens and torsion specimens with an internal void (b) YZ view of void locations

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