November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Nathan EvansResearch Assistant

Effects of Refurbishment on the Fatigue Life of Bearings

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Presentation Outline

• Personal background• Motivation and objective• Repair options/methods• Analytical/numerical approach• Test rigs for refurbishment studies• Future work

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Personal Background

• Joined METL (August 2013)• BS in Mechanical Engineering

– Brigham Young University, 3.92 GPA (April 2013)

• Mechanical Engineering Intern– BioFire Diagnostics (May 2013 – August 2013)

• Mechanical Engineering Intern– BioFire Diagnostics (April 2012 – August 2012)

• Mechanical Engineering Intern– Navistar (June 2011 – August 2011)

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Motivation and Objective

• Refurbish vs. replace– Save money– Reduce downtime– Conserve energy and material

• Objective– Provide guidelines regarding

estimation of the remaining useful life of bearings that are refurbished

The outer race of a spherical roller bearing in need of refurbishing [1]

The outer race of a spherical roller bearing after refurbishing [1]

[1] http://www.timken.com

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Repair Options/Methods

• Type I service generally describes recertification or cleaning and inspection.

• Type II service involves reconditioning or polishing repair.

• Type III applies to bearings with extensive damage. Regrinding of races, installation of oversize rollers in order to maintain bearing geometry and clearance in bearings where radial internal clearance is critical.

Technicians measure and record internal tolerances before a bearing is refurbished [1]

[1] http://www.timken.com

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Analytical/Numerical Approach

• Develop a model to predict useful life of bearings after refurbishment• Determine the fatigue life distribution• Remove surface material while preserving damage accumulation

characteristics in the remaining material• Restart the fatigue cycling on the newly modified (yet previously

damaged) surface and study the resulting life predictions, damage modes, etc

• Include effects of residual stresses and plasticity

Material above green lines removed after original model is interrupted

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Test Rigs for Refurbishment Studies

Modified Five-Ball Test Rig

Torsion Fatigue Test RigApplied load

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November 14, 2013Mechanical Engineering Tribology Laboratory (METL)

Future Work

• Conduct fatigue testing using five-ball test rig– Develop S-N diagram– Regrind the flat specimen to simulate refurbishing

processes• Test specimens after grinding to estimate useful life

following refurbishing• Conduct similar fatigue testing using torsion test rig