Prediction of Contact Temperature Distribution during Fretting Fatigue in Titanium Alloys

Abstract

Fretting is a critical problem to the manufacturers and operators of turbine engines, reducing the useful life of fan, compressor, and turbine blade components. The fretting action between the two components in contact leads to temperature rise, which in most cases, may be significant enough to cause a number of adverse effects. The knowledge of the temperature profiles inside the material is very important because it enables the prediction of possible oxide formation and the development of thermal stresses. To this end, the temperature profile for Ti-6Al-4V alloys has been predicted in this work utilizing a heat flow channel (HFC) model. The model requires as input the material constants (thermal conductivity, thermal diffusivity, and flow stress), the material surface characteristics (roughness and asperity spacing), the frictional conditions between the two surfaces, as well as the external parameters (frequency, amplitude of oscillation, magnitude of contact area). The analysis enabled the determination of the temperature field as a function of time and the three spatial coordinates. The model showed that the temperature increases quite rapidly at the beginning of the process and reaches an essentially constant value after approximately 1000 cycles. The predictions revealed a rapid decay of temperature with the thickness of the specimen, while the temperature drop was found to be much smoother in the other two specimen directions. Additionally, a first-order validation of the model was achieved by determining the oxygen concentration in fretting-fatigued Ti-6Al-4V specimens, where it was found that an increased oxygen concentration existed in the fretting area compared to the non-contact and stick areas.

KEY WORDS:

• Fretting Fatigue
• Titanium Alloys
• Ti-6Al-4V
• EDS
• Heat Conduction