Dissection and removal of lesion areas are fundamental operations in brain surgeries. Therefore, damage and fracture models are needed to simulate dissection and removal operations. Generally, brain tissues show strong ductility; however, conventional fracture or damage models cannot reproduce ductile fractures well. In this paper, a simple damage and fracture model of brain parenchyma is proposed for real-time haptic surgery simulations. Although the proposed model does not require iterative calculation, it can reproduce ductile fracture while maintaining sufficient accuracy. The finite element method (FEM) is used to perform numerical simulations. In the proposed damage model, it is assumed that micro-damage begins when von Mises stress exceeds a certain threshold in an element, and the micro-damage grows with increased von Mises stress. The stiffness decreases as the micro-damage grows. When the integrity of an element becomes smaller than a certain threshold, the element is removed to express the occurrence of a fracture. These steps were formulated algorithmically. In order to verify the proposed damage and fracture model, tensile tests were conducted using porcine brain parenchyma. Parameters for the proposed damage model were identified using the results of the tensile tests. Tensile test simulations were performed using the identified parameters. The simulations effectively reproduced the stress-strain curves obtained in the tensile tests using porcine brain tissues.
2016 by The Japan Society of Mechanical Engineers