New algorithm of cuff-tissue-artery system modeled as the space axisymmetric problem

In this paper, mathematical models for cuff-tissue-artery system are developed and simplified into an axisymmetric problem in space. It is nonlinear properties of cuff and artery wall that make it difficult to solve elastic equations directly with the finite element method, hence a new iteration algorithm derived from principle of virtual work is designed to deal with nonlinear boundary conditions. Numerical accuracy is highly significant in numerical simulation, so it is necessary to analyze the influence different finite elements and grid generation on numerical accuracy. By dimensional analysis, it is estimated that numerical errors must be $O(10^{-5})cm$ or less. To reach desired accuracy, the number of grids using higher order elements becomes one-fourth as large as that using low order elements by convergence rate analysis. Moreover, dealing with displacement problem under specific blood pressure needs much small grid size to make numerical errors sufficiently small, which is not taken seriously in previous papers. However, it only takes a quarter of grids or less for displacement change problem to guarantee numerical accuracy and reduce computing cost.