Deformation Resistance in Soft Tissue Cutting: A Parametric Study

Estimation and modeling of soft tissue deformation during cutting is important for developing a reality based haptic interaction model for surgical training and simulation. In this paper, we are interested in understanding the effect of parameter changes, such as the cutting speed and the angle of cutting, to develop a predictive model that is self consistent with the experimental observations. The parametric study of deformation resistance in soft tissue (ex-vivo) cutting involves characterizing the cutting forces versus displacement plot at various cutting speeds (ranging from 0.1cm/sec-2.54cm/sec) and cutting angles (for 0 degree and 45 degree cutting angle). The force-displacement data in all these studies reveals that the cutting process consists of a sequence of intermittent localized fracture (localized crack extension in the tissue). The deformation resistance to the cutting blade was determined through offline computation of the local effective Young’s modulus (LEYM). For cutting at 45 degree cutting angle, LEYM was consistent and varying within close bounds for a given cutting speed. Our analysis shows that, the plot of LEYM versus cutting speed is linear at 0 degree cutting angle and nonlinear at 45 degree cutting angle. Furthermore, for a given cutting speed, we observe a decrease in the local effective Young’s modulus as the cutting angle is varied from 0 degrees to 45 degrees. The results from plane-stress and planestrain finite element analyses reveal that the magnitude of the self-consistent LEYM varies within close bounds for all our experimental observations.