ENDOFEM INTEGRATED METHODOLOGY FOR FATIGUE CRACK GROWTH

摘要

In this paper, the FEM with the incremental endochronic cyclic plasticity (EndoFEM) and the r_c controlled node-released strategy are employed to study the fatigue crack opened/closed load (P_(op)) of Al 2024-T3 CCT specimens provided by Mageed and Pandey under several crack lengths and the constant amplitude with various load ratio (R). After statisfactory results are achieved by comparisons of computed P_(op) values and cited experimental data, the simulations will be extended to the crack lengths with significant bending effect due to short ligaments or high peak (P_(max)) or high positive or very low negative R cyclic loads. Through these simulations, the complete map of P_(op)/P_(max) vs. K_(max) and R can be constructed and thereafter its correspondant empirical formulae can be proposed. Using these formulae and selecting the traditional fatigue crack growth parameter ΔK_(eff), the Al 2024-T3 fatigue crack growth rate da/dN vs. ΔK and R data, provided by Hiroshi and Schijve, can be employed to proposed empirical formulae of da/dN vs. ΔK_(eff) and R. After integration, fatigue-crack-growth length a vs. N curves computed by EndoFEM can be obtained. The results are agreed very well with the existing experimental curves. According to the above procedures of simulation and steps of comparions with experiment, this paper may provides an integrate methodology of numerical simulation in the studies of fatigue crack growth for academic and industrial researches and design analysis.