中文摘要：

软组织形变仿真是虚拟手术系统的关键技术.针对目前软组织形变仿真方法存在的问题，基于黏弹性力学模型提出了无网格伽辽金（EFG）与质点弹簧（MS）耦合的软组织形变仿真方法.在手术区域即大变形和拓扑改变区域采用EFG，其他区域采用MS方法，2个区域之间建立过渡单元；在过渡单元内建立过渡节点，根据过渡节点必须满足位移和力平衡条件来实现2个区域的无缝耦合.对人体肝脏的形变仿真实验结果表明，该方法是有效的.

英文摘要：

Simulation for the soft tissue deformation is a key technique in the virtual surgery. Addressing the issues existed in the simulation for the soft tissue deformation in the virtual surgery, a coupling deformable model integrating the element-free Galerkin （EFG） with the mass-spring （MS） based on viscoelastic mechanics equations was proposed. The EFG was used to model material behavior close to large deformation or topology change and the MS was used in area away from large deformation. In the interface area of two regions, some transitional elements including transitional joint points were built. Seamless connection of two regions was realized according to the balance conditions of forces and displacements that should be satisfied by transitional joint points. The experimental simulation results of the human liver show that the proposed methodology is valid.