Constitutive analysis of biomedical grade Co-27Cr-5Mo alloy at high strain rates

Cobalt Chrome is used extensively within the biomedical industry for hip, knee and shoulder prostheses. These components are manufactured using a range of different processes which includes machining. In order to develop Finite Element Models of machining processes, it is necessary to develop the constitutive model of the workpiece material at high strain rates over different temperatures. During this research, Split Hopkinson Pressure Bar tests were conducted over a wide processing domain of temperatures (298-873 K) and strain-rates (600-1400 s−1) to predict the constitutive model of biomedical grade Cobalt Chrome based on modified Zerilli-Armstrong, modified Johnson-Cook and strain compensated Arrhenius-type models. The prediction capability of these models was evaluated in terms of average absolute relative error and correlation coefficient between predicted and experimental flow stress values. Results demonstrated that the modified Zerilli-Armstrong model can track the deformational behaviour more accurately throughout the entire processing domain investigated compared to the other models. The model recorded an average absolute relative error of 2.71% and a correlational coefficient of 0.98.