Determining deformation resistance in cutting soft tissue with nonuniform thickness

Understanding soft tissue response during tool tissue interaction is important for developing a reality based haptic interaction model for surgical training and simulation. In this work, experiments were conducted to cut liver specimens with nonuniform thickness. Three cutting speeds ranging from 0.1 cm/sec-2.54 cm/sec were used. The cutting forces, cutting tool displacement, and tool/tissue imaging via stereo camera system were collected. The time varying depth-of-cut in the thickness-varying specimen was then determined using image analysis. The force-displacement data revealed that the cutting process consisted of a sequence of repeating units each comprising of a localized deformation phase followed by localized crack extension phase in the tissue. Based on depth-of-cut normalized cutting force, the deformation resistance of the tissue during the localized deformation phases was determined. The deformation resistance was characterized via the local effective modulus (LEM) of the soft tissue. The effect of cutting speed on the deformation resistance of the soft tissue was determined.