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Non-linear elastic characterisation of a high strength bainitic roller bearing steel
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).ORCID iD: 0000-0001-6896-1834
2013 (English)In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 68, 1-15 p.Article in journal (Refereed) Published
Abstract [en]

A small but not negligible non-linear elastic behaviour was detected when investigating cyclic uniaxial push-pull experiments on a high strength bainitic steel. Cyclic torsion experiments led to the conclusion that the shear modulus was relatively constant. A non-linear elastic model was implemented where the bulk modulus was extended with a second order term related to the elastic dilatation and where the shear modulus was constant. The material presented a strength differential effect (SDE), with larger yield stress in compression than in tension. Consequently, the non-linear elastic model was combined with a plasticity model that incorporated a Drucker-Prager yield surface, non-associated flow rule and combined non-linear hardening. Expressions that include non-linear elasticity were derived for the elastic-plastic hardening and the compliance tensors. The extended material model predicted the elastic-plastic results from cyclic push-pull experiments. Also, a phenomenological analysis of the cyclic elastic response showed isotropic damage in the elastic moduli. The steady-state damage increased linearly with the cyclic plastic strain range.

Place, publisher, year, edition, pages
Elsevier, 2013. Vol. 68, 1-15 p.
Keyword [en]
Non-linear elasticity, High strength steel, Bainite, Strength differential effect, Cyclic experiments, Isotropic damage
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-121617DOI: 10.1016/j.ijmecsci.2012.11.008ISI: 000316974800001ScopusID: 2-s2.0-84875225907OAI: diva2:620215

QC 20130508

Available from: 2013-05-08 Created: 2013-05-03 Last updated: 2016-04-18Bibliographically approved
In thesis
1. Mechanical behaviour of a roller bearing steel: Strength differential effect, low temperature creep and propagation of short cracks
Open this publication in new window or tab >>Mechanical behaviour of a roller bearing steel: Strength differential effect, low temperature creep and propagation of short cracks
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fatigue cracks in bearings either initiate from the surface or from an inclusion below the rolling contact surface. Then, short cracks start to propagate. Short crack grow at considerably faster rates than long cracks subjected to a nominally equivalent stress intensity factor range. One of the explanations for the difference in growth behaviour between short and long cracks is the development of plastic deformation at the advancing crack tip. In order to investigate this effect, the analysis of short crack propagation at bearing loads requires understanding of the fundamental material behaviour. This thesis presents the material characterisation of a bainitic high strength bearing steel, where the yield stress in tension was lower than in compression. This phenomenon is called strength differential effect (SDE). The work studies the influence of the SDE on the cyclic plastic properties, the elastic behaviour of the material, low temperature creep. These mechanical properties are quantified and modelled using continuum models.

Paper A focused on the characterisation of the SDE which was modelled using a Drucker-Prager yield surface and a non-associated flow rule. The cyclic mechanical properties were quantified and modelled using combined non-linear hardening.

In paper B the elastic behaviour of the material was studied; the material showed non-linear elastic behaviour in uniaxial tension and compression. The elastic modulus was higher in compression than in tension at high stress levels. On the other hand, the cyclic torsion experiments showed that the stress-strain elastic relation in shear was linear. A non-linear elastic model was proposed.

Low temperature creep was studied in Paper C, where the creep strains were quantified in tension and compression. The material showed higher creep strains in tension than in compression for the same stress level and the influence of the SDE in low temperature creep was analysed.

The short crack growth in the bainitic steel was analysed through simulations in Paper D. The material model described in Paper A was implemented in a material subroutine. The simulations captured the development of plastic strains as the short crack becomes long. The material model could qualitatively describe the experiment results, where the change in rate as the crack advanced from short to long was ascribed to the growing plastic zone ahead of the crack tip.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 37 p.
TRITA-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0573
National Category
Mechanical Engineering
urn:nbn:se:kth:diva-163231 (URN)978-91-7595-493-6 (ISBN)
Public defence
2015-04-21, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 09:00 (English)

QC 20150331

Available from: 2015-03-31 Created: 2015-03-30 Last updated: 2015-03-31Bibliographically approved

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