transcript
- Slide 1
- November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) Sina Mobasher Moghaddam Ph.D. Research Assistant Effect of
Mean Stress on Rolling Contact Fatigue
- Slide 2
- 2 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) Outlines Butterfly-wing formation in bearing steel
Background and Motivation Stress Analysis METL suggested theory
Results comparison and validation Effect of compressive stress on
torsion fatigue Instrument Design Fatigue life reduction Failure
mode change FEM simulation
- Slide 3
- 3 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) Butterfly Wings Detrimental Effect on RCF [1] Vincent A.,
Lormand G., Lamagnere P., Gosset L., Girodin D., From White Etching
Areas Formed Around Inclusions To Crack Nucleation In Bearing
Steels Under Rolling Contact Fatigue, ASTM International, 1998 [2]
A. Grabulov, R. Petrov, H.W. Zandbergen, 2009, EBSD investigation
of the crack initiation and TEM/FIB analyses of the microstructural
changes around the cracks formed under Rolling Contact Fatigue
(RCF) International Journal of Fatigue 32 (2010) 576 583
Butterflies Observed by Vincent [1](top) and Grabulov
[2](Bottom)
- Slide 4
- 4 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) Wing Span Debonded Region Coarse Grains 50-100 nm Crack Fine
Grains 5-10 nm ORD Butterfly Wing Characteristics Schematic of a
pair of butterfly wings
- Slide 5
- 5 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) Stress Analysis Inclusion presence induces stress
concentrations in the surrounding matrix When dealing with fatigue
problems, it is important to consider stress history
- Slide 6
- 6 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) Butterfly Wing Evolution Butterfly wing orientation,
direction, and size are consistent with the experimental
observations Color spectrum of butterfly wing formation Butterfly
formation according to Grabulov[1] Butterfly formation according to
METL model prediction [1] A. Grabulov, R. Petrov, H.W. Zandbergen,
2009, EBSD investigation of the crack initiation and TEM/FIB
analyses of the microstructural changes around the cracks formed
under Rolling Contact Fatigue (RCF) International Journal of
Fatigue 32 (2010) 576 583
- Slide 7
- 7 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) 0.7 b 0.8 b 0.38 b 0.42 b 1.1 b 0.4 b 0.6 b 1.1b [1]
M.-H.Evans,etal.,Effect of Hydrogen on Butterfly and White Etching
Crack (WEC) Formation under Rolling Contact Fatigue
(RCF),Wear(2013), http://dx.doi.org/10.1016/j.wear.2013.03.008i
Effect of Depth on Butterfly Growth
- Slide 8
- 8 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) S-N Curve for Butterfly Formation Damage equation is
calibrated by curve fitting to Torsion Fatigue data S-N curve for
butterfly formation [1] Takemura H, et al., Development of New Life
Equation for Ball and Roller Bearings, NSK Motion & Control No.
11 (October 2001)
- Slide 9
- 9 November 14, 2013 Mechanical Engineering Tribology Laboratory
(METL) Effect of Inclusion Size on Butterfly Wing Span [1] Lewis,
Tomkins, A fracture mechanics interpretation of rolling bearing
fatigue, Proc IMechE Part J: J Engineering Tribology,(2012) For
comparison, the wingspan to inclusion diameter ratio is compared
The model results lie within the bounds of the experimental results
and show the same trend
- Slide 10
- 10 November 14, 2013 Mechanical Engineering Tribology
Laboratory (METL) Schematic showing the reversal of shear in
presence of compressive stress along the inclusion- matrix
interface Debonding on Inclusion/ Matrix Interface [1] A. Grabulov,
R. Petrov, H.W. Zandbergen, 2009, EBSD investigation of the crack
initiation and TEM/FIB analyses of the microstructural changes
around the cracks formed under Rolling Contact Fatigue (RCF)
International Journal of Fatigue 32 (2010) 576 583 Areas of
debonding (A & B) and deformation (C) observed by (Grabulov[1])
METL Model prediction (bold, black arches show the debonding areas)
To find the debonding regions, stresses should be resolved along
the inclusion/ matrix interface Stress transformation formulas in
2D are employed for this purpose
- Slide 11
- 11 November 14, 2013 Mechanical Engineering Tribology
Laboratory (METL) Prediction of Crack Initiation Locations Cracks
are commonly observed on top of the upper wing and bottom of the
lower wing Mode I loading is suggested as the main factor for crack
development in vicinity of the inclusion FEM results show maximum
tensile stress during loading history is higher on top of the upper
wing and bottom of the lower wing [1] Lewis, Tomkins, A fracture
mechanics interpretation of rolling bearing fatigue, Proc IMechE
Part J: J Engineering Tribology,(2012) Maximum tensile stress
resolved along the butterfly edges
- Slide 12
- 12 November 14, 2013 Mechanical Engineering Tribology
Laboratory (METL) Effect of Compressive Stress on Torsion Fatigue
RCF is a shear dominated phenomena There is a large compressive
stress present in the contact zone A custom made set of clamps are
designed to apply high compressive stress (up to 2.5 GPa) on
torsion specimens to better simulate RCF failure Stress history at
0.5b Custom made clamps: a) exploded view b) as they appear after
assembly Schematic of Hertzian contact zone in clamp/ specimen
interface
- Slide 13
- 13 November 14, 2013 Mechanical Engineering Tribology
Laboratory (METL) Effect of Compressive Stress on Torsion Fatigue
Life Application of compressive clamps reduced the torsion fatigue
life The reduction is up to in one order of magnitude in high cycle
fatigue Steel B Steel C Steel E
- Slide 14
- 14 November 14, 2013 Mechanical Engineering Tribology
Laboratory (METL) Effect of Compressive Stress on Fracture Mode
Initiation cracks Propagation cracks As opposed to helical fracture
surfaces for pure torsion tests, broken specimens form cup &
cone pairs Initiation cracks are due to torsion while multiple
cracks grow in the propagation stage Initiation and propagation
cracks in sample failed specimens Sample failed specimens at
different load levels
- Slide 15
- 15 November 14, 2013 Mechanical Engineering Tribology
Laboratory (METL) FEM Model Life Prediction and Failure Simulation
Without compressive stress With compressive stress A user defined
subroutine is developed to apply a Hertzian pressure profile at the
center of the specimen FEM results show similar crack patterns to
experiments Life prediction is successful implementing the damage
mechanics S-N Curve: Experiment vs. FEM
- Slide 16
- 16 November 14, 2013 Mechanical Engineering Tribology
Laboratory (METL) Summary and Future Work Summary Damage mechanics
is used to model butterfly wing formation in bearing steel The
model predicts butterfly shape and size with respect to inclusion
diameter and depth successfully S-N curve for wing development is
in corroboration with experiments Effect of compressive stress on
torsion fatigue life and fracture mode is studied Future Work
Explore capabilities of damage mechanics to model DERs, WEBs, and
WECs in bearings Conduct RCF tests to expand a data base for
different types of microstructural changes in bearings Experimental
and analytical investigation of effect of steel cleanliness on
torsion fatigue and RCF