Contact geometry, friction and load variations in fretting fatigue of titanium-aluminuml-vanadium

Shyama Kumari, Purdue University

Abstract

Statistical analysis of uncertainties in constant and variable amplitude fretting fatigue life of Ti-6Al-4V due to contact surface profile and friction variations are investigated. Tractions and stresses in the contact region are functions of loads, contact surface profile, coefficient of friction and material properties. The effect of contact surface profile, friction variation and load history are studied in detail. Equivalent stress parameter combined with weakest link criteria to determine crack nucleation life is discussed. Semi-elliptical surface crack and through crack propagation are studied to determine failure of the component. Total life determination using Findley parameter at a critical depth is also investigated. A semi-empirical approach of critical depth determination with the help of Findley parameter gradient is introduced. Life predictions are compared with experimental data. For machined and worn surface profiles, statistical distribution for each set of the multiaxial stress parameter and calculated life results are investigated. The overall coefficient of variation (CV) of multiaxial equivalent stress parameter, crack nucleation life, crack propagation life and total life cycles are found less than 10%, 25%, 20% and 20%, respectively. Three different damage accumulation techniques are used to find total life of the component subjected to variable amplitude fretting fatigue loading. All the three damage accumulation techniques predict the estimated life with very little difference in terms of number of blocks of variable amplitude fretting fatigue loading.

Degree

Ph.D.

Advisors

Farris, Purdue University.

Subject Area

Aerospace materials

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