Multiscale fatigue crack growth modelling for welded stiffened panels

A B S T R A C T The influence of welding residual stresses in stiffened panels on effective stress intensity factor (SIF) values and fatigue crack growth rate is studied in this paper. Interpretation of relevant effects on different length scales such as dislocation appearance and microstructural crack nucleation and propagation is taken into account using molecular dynamics simulations as well as a Tanaka-Mura approach for the analysis of the problem. Mode I SIFs, K I , were calculated by the finite element method using shell elements and the crack tip displacement extrapolation technique. The total SIF value, K tot , is derived by a part due to the applied load, K appl , and by a part due to welding residual stresses, K res . Fatigue crack propagation simulations based on power law models showed that high tensile residual stresses in the vicinity of a stiffener significantly increase the crack growth rate, which is in good agreement with experimental results. Keywords dislocation; fatigue crack growth rate; microstructurally small cracks; residual stress. N O M E N C L A T U R E a = half crack length a 0 = initial crack length a fin = final crack length C = material constant of the Paris equation CRSS = critical resolved shear stress d = slip band length da/dN = crack growth rate E = Young's modulus F → r; t ð Þ = interatomic force F max = maximum applied force F min = minimum applied force G = shear modulus K = stress intensity factor (SIF) K appl = stress intensity factor due to the applied load K res = stress intensity factor due to weld residual stresses K th = stress intensity factor threshold K tot = total stress intensity factor m = atomic mass m = material constant of the Paris equation N = number of stress cycles for the fatigue crack propagation N f = number of stress cycles for fatigue failure N g = number of stress cycles required for crack nucleation in a single grain N ini = number of stress cycles needed for the initiation of a small crack R = stress ratio R eff = effective stress intensity factor ratio U → r ; t ð Þ = interatomic embedded atom method pair potential W c = specific fracture energy per unit area Correspondence: Ž. Božić

Multiscale Fatigue Modelling of Metals

Защита металлических материалов от коррозии имеет большое значение во многих областях, особенно когда речь заходит об охране окружающей среды. Основное внимание в книге уделяется органическим и неорганическим покрытиям, металлическим покрытиям и новым методам нанесения тонких защитных слоев. Представлены технологии нанесения покрытий и методы тестирования и оценки коррозионных свойств.Используемые программы Adobe AcrobatThe corrosion protection of metallic materials is of great importance in many fields, especially also when it comes to environmental issues. The book focuses on organic and inorganic coatings, metallic coatings and new methods for the deposition of protective thin layers. Coating techniques and methods for testing and assessing corrosion behavior are presented

CHITOSAN TREATMENT, A POSSIBILITY TO CONTROL POSTHARVEST DISEASES OF ORGANIC TABLE GRAPES.

PROC. 16TH IFOAM ORGANIC WORLD CONGRESS, MODENA, ITALY, JUNE 16-20 (ACTA HORTICULTURAE IN PRESS, SUBMITTED 28 NOVEMBER 2007)