Purdue University

Purdue University

Mechanical Engineering
Tribology Laboratory

John Bomidi


  Dissertation Title: Experimental and Three-Dimensional Finite Element Investigation of  Fatigue
M.S., Purdue University, West Lafayette, 2009
B.Tech., IIT-BHU, India, 2007

email: john.bomidi@gmail.com





Materials fail at a significantly lower fluctuating load than their monotonic ultimate strength or even the yield strength due to progressive internal material degradation; commonly known as fatigue.  Moreover, the scatter in fatigue life and the stochastic fatigue failure is linked to basic microstructural effects such as random microstructure topology and the initiation/growth of cracks along Inter/Trans granular planes.  Finite three-dimensional characteristics of geometry and the microstructure can significantly influence the failure initiation and progression, thereby impacting the resulting fatigue lives.  Recognizing this connection, this study presents experimental test results and a three-dimensional modeling approach for capturing fatigue failure observed in experimental testing and for investigating fatigue of components in the framework of finite element analysis.  The following phenomena are investigated:

  • Fatigue of micro beams
    • Results of fatigue life and failure from 3D modeling of intergranular fatigue in microbeams are compared with experimental observations reported in literature
  • Tensile fatigue of thin sheets
    • A test rig with a new grip and alignment system is developed to address the challenges associated with thin sheet testing and conduct fatigue experiments
    • The 3D fatigue model is enhanced to capture the dominant transgranular fatigue observed in the experiments. The observed and modeled fatigue life and failure are compared.
  • Torsion fatigue of bearing steel variants
    • Custom grips are developed and integrated with an MTS torsion test rig to undertake torsion testing of various bearing steel variants
    • A model for torsional fatigue failure was developed and the experimental and numerical results are compared
  • Rolling contact fatigue
    • An improved 3D RCF model is developed which is computationally efficient and accurate compared to a previously published model by METL
    • The 3D fatigue model is enhanced to investigate the effects of plasticity and fatigue damage due to plastic strain accumulation on Rolling Contact Fatigue

Archival Publications

  1. Bomidi, J.A.R., Sadeghi, F., “3D Finite Element Elastic-Plastic Model for Subsurface Initiated Spalling in Rolling Contacts”, ASME Journal of Tribology, 2014 (in press)

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