Digital Repository, ECF14, Cracow 2002

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The Behaviour of Kinked RCF Cracks in Contact

Last modified: 2013-02-10


Shallow angle cracks nucleated in rolling contact area can propagate incoplanar direction as well as branch upwards or downwards, depending on loadingconditions. The direction of growth and the tendency for branching, in general depend onthe crack geometry and the possible kinds of load, such as: contact normal load, residualstresses, traction forces, bending stresses and thermal stresses. Additionally, frictionconditions at the crack faces and liquid if present in the crack interior can influence crackbranching. All mentioned above kinds of load are not constant and conditions are not thesame during operation. Loads can act in various combinations and magnitudes. Thefriction conditions can also vary. Even the crack itself creates continuously new geometrychanging its length and shape during the growth. These factors indicate on varyingpreferences for the growth direction, which can be "chosen" by the crack during the periodof exploitation. Finally, the original plane crack can be accompanied by a branch or anumber of branches leading to the so-called "kinked" crack, which is a subject of analysisin this paper. The cracks with single and double branches were analysed and the resultswere compared with those for the straight, coplanar crack. To predict the behaviour ofsuch cracks, the loading histories were determined (SIF variations) for all their possiblefronts and then the growth rates for all directions were estimated.

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