Optimisation Method for Determination of Crack Tip Position Based on Gauss-Newton Iterative Technique

Abstract In the digital image correlation research of fatigue crack growth rate, accuracy tip position determines calculation stress intensity factor, thereby affecting life prediction. This paper proposes a Gauss-Newton iteration method for solving position. The conventional linear fitting provides an iterative initial solution this method, and preconditioned conjugate gradient is used to solve ill-conditioned matrix. A noise-added artificial displacement field verify feasibility which shows that all parameters can be solved with satisfactory results. actual factor case value obtained by in very close finite element result, relative error between two only ? 0.621%; Williams coefficient also better define contour plastic zone at tip, maximum test area 11.29%. defined experimental reached 26.05%. coordinates, factors, changes loading unloading phases are explored. results show change during process faster than process; under same load condition larger load, theoretical higher process.