We study the deformation and haptic feedback of soft tissue in virtual surgery based on a liver model by using a force feedback device named PHANTOM OMNI developed by SensAble Company in USA. Although a significant amount of research efforts have been dedicated to simulating the behaviors of soft tissue and implementing force feedback, it is still a challenging problem. This paper introduces a kind of meshfree method for deformation simulation of soft tissue and force computation based on viscoelastic mechanical model and smoothed particle hydrodynamics (SPH). Firstly, viscoelastic model can present the mechanical characteristics of soft tissue which greatly promotes the realism. Secondly, SPH has features of meshless technique and self-adaption, which supply higher precision than methods based on meshes for force feedback computation. Finally, a SPH method based on dynamic interaction area is proposed to improve the real time performance of simulation. The results reveal that SPH methodology is suitable for simulating soft tissue deformation and force feedback calculation, and SPH based on dynamic local interaction area has a higher computational efficiency significantly compared with usual SPH. Our algorithm has a bright prospect in the area of virtual surgery.

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Abstract. The cutting mechanical properties of impregnated diamond bit depend on the performance of its cutting elements. Aiming at the factors affecting the cutting element performance of impregnated diamond bit, the laboratory rock breaking experiment of impregnated micro bit is carried out. The results show that the breaking work ratio and unit wear first decrease and then increase with the increase of diamond particle size and concentration when drilling sandstone; the rock breaking efficiency and wear resistance are the highest when the concentration is 125 %. The breaking work ratio first decreases and then increases with the increase of diamond particle size when drilling limestone; the rock cutting efficiency is the highest when the concentration is 100 %. With the increase of diamond particle size, the breaking work ratio increases and the unit wear decreases when drilling granite; the rock cutting efficiency and wear resistance are the highest when the concentration is 150 %.

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