Sandeep Kibey

Graduate Research Assistant
Department of Mechanical & Industrial Engineering
University of Illinois at Urbana Champaign , Illinois 61801 USA

Description of Research

I am doing MS in Mechanical Engineering with specialization in Computational Fracture Mechanics My advisor is Huseyin Sehitoglu, Grayce Wicall Gauthier Professor of Engineering at UIUC.My research involves finite element simulation and computational analysis of fatigue crack growth and fatigue crack closure in metals. The motivation and the objective of my research is described below in brief.

Since the last two decades, a significant volume of research on fracture mechanics has been devoted to fatigue crack closure, a phenomenon first observed by Elber (1970). One reason is that closure has been associated with a wide variety of effects on fatigue crack growth. Most of the observed effects such as effect of notches, transient loadings, in-plane biaxaility etc can be explained by the concept of fatigue crack closure.

A variety of closure mechanisms have been proposed and observed. The primary and frequently encountered mechanism is plasticity-induced crack closure, a term coined by Suresh and Ritchie (1980).This mechanism can be explained thus: material at the crack tip experiences very high stresses and so deforms plastically. When the crack tip advances, it leaves behind it a wake of tensile residual displacements normal to the crack. However, the plastic zone is constrained by the surrounding elastic material and the resultant compressive stresses cause premature closing of the crack at positive loads during fatigue cycle.Budiansky and Hutchinson (1978) used complex functions to demonstrate the existence of plasticity-induced crack closure in plane stress conditions. They employed the well-known Dugdale-Barenblatt model to assess the effects of closure on crack opening and closing loads for a range of stress/loading ratios.

The other known closure mechanisms are: roughness induced closure, transformation induced closure and oxide induced closure. A combination of these mechanisms might be operative in an actual crack depending on the loading, material, roughness and environmental conditions.

The elasto-palstic (plane stress) finite element analysis of crack closure was first done by Newman (1976).He used springs with varying stiffness to simulate contact and separation of crack faces. When the crack surfaces are in contact the stiffness is set to a very large value (ideally infinite) to simulate rigid contact and when the surfaces separate, the stiffness gradually reduces to zero. Since then, finite element simulations of crack closure have been carried out under both plane stress and plane strain conditions. In 1989,McClung and Sehitoglu critically examined the FEA models and laid down the mesh refinement criteria for closure and node release schemes. They used the code developed by Sehitoglu and Lelor (1988).A review of developments can be found in the paper by Sehitoglu (1996).

The bulk of work done has been carried out to predict the closure phenomenon for either pure mode I and pure mode II cracks. McClung and Sehitoglu (1989) have considered mode I and II together to some extent. By and large , much work remains to be done so far as inclined cracks are concerned.

An inclined crack poses a more complex but realistic situation, in terms of mode-mixity, geometry, contact interaction of the crack faces etc. An inclined crack is prone to deflection due to mode-mixity. A model describing the behavior of an inclined crack should take this into account. Presently, no such comprehensive model exists in literature.

The aim of my research is to develop a model to predict crack opening and closing behavior for an inclined fatigue crack and determine the crack driving force for this crack. The factors influencing the driving force will also be determined. It is essential that the effect of microstructure on closure be considered. We expect to come up with such a model in the due course of our investigations.

Academic and other links

Univesrity of Illinois at Urbana Champaign
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ABAQUS Consultation
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Calvin and Hobbes
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James Allen's webpage
A philosopher and a great thinker...better known as the author of 'As a Man Thinketh'
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American Society of Mechanical Engineers
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Stanford comics on Graduate school
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Joined UIUC in: Spring 2001


Graduate Teaching Assistant,Department of Mechanical & Industrial Engineering,UIUC,Spring 2001.

Research Assistant,Department of Mechanical & Industrial Engineering,UIUC,Summer 2001-till date.

GPA: 4.0/4.0


ME345 Introduction to FEA

ME457 Inelastic Design Methods

ME497 Advanced Fracture Mechanics

CEE478 Finite Elements in Solids and Structures

ME346 Failure Mechanisms in Engineering Materials

Personal Information

I am from the city of Nasik, Maharashtra.I did my BE in Mechanical Engineering from Univesrity of Pune, India (class of '99).After that I joined Siemens Ltd.,India for a period of 1 year in the capacity of an Engineering Intern(Aug 1999-July 2000).Before coming to UIUC, I had a brief association with Tata Technologies India Ltd.,Pune.(Sept 2000-Nov 2000). My family lives in Nasik.I have a younger brother who is doing BE in Electronics and Telecommunications Engg at COEP,Pune.


My primary interest is in the field of finite element analysis.I am interested in modeling and simulation of mechanical systems especially modeling of material behavior.On the lighter side, I am interested in reading,sports and music.My hobbies include playing badminton,watching movies, reading fiction and non-fiction,listening to pop,rock,hindi songs,gazals etc.