A Novel Experimental Technique for Dynamic Friction StudiesAlejandro J. Patanella, M.Sc., Purdue University, 1998.
Major Professor: Dr. Horacio D. Espinosa.
To understand the dynamic response of bodies in contact, dynamic (kinetic) friction is investigated. A novel experimental technique, which provides a normal static load and a tangential dynamic load independently applied, is developed by modifying the split Hopkinson Torsional Bar method. Torsional stress wave propagation along an input bar, pressing statically against an output bar, is analyzed and experimentally verified. Static and kinetic friction coefficient of Ti 6Al-4V sliding against Steel 1080, Al 6061-T6 sliding against Steel 1080, and Al 6061-T6 sliding against Al 7075-T6 with different surface characteristics were investigated at sliding velocities up to 5 m/s. Surface roughness was varied to understand its role on the frictional response of the sliding materials. The dependence of friction coefficient on material strain-rate sensitivity was also assessed. Measured friction coefficients compared well with values reported in the literature, using different techniques and different experimental conditions. This shows the validity of the newly developed apparatus. Moreover, shear band studies at strain rates up to 1000 s-1 in Ti 6Al-4V and Al 6061-T6 were conducted to validate the behavior of the modified Kolsky bar. The developed experimental technique provides a robust method for direct measurement of the static and dynamic (kinetic) friction coefficient with a simple configuration and data analysis.