Material removal mechanism thermal model

As a general rale, visco-plastic material behavior is specified for FEM simulation of chip removal. Thermo-mechanically coupled calculations are used. For describing material behavior, the use of the Johnson-Cook equation (Eq. 4) is preferred. Another semiempiiical model presented by Zerilli and Armstrong considers micro-mechanical effects in relation to the thermal activation behavior of face-centered (fee) and body-centered cubic (bcc) structures of the workpiece material. Other constitutive material laws are formulated by Oxley, Clifton Hensel-Spittel, and El-Magd, respectively, whereas the stress s is determined by different linear or exponential procedures within the equation terms. 

Understanding the mechanisms of polar order decay is crucial for the tailoring of new exploitable active materials. In contrast with crystals, polymers containing oriented molecules tend to evolve towards a randomization of dipole orientation when the field is removed. Relaxation in such poled systems, following the molecular statistical model, arises from thermal reorientation whose rate is governed by the mobility of the molecules in the matrix. The mobility is in turn determined by a number of parameters including, in particular, glass transition temperature (Tg) and the amount of free volume in the polymer. 

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