This paper describes an original implementation of a two-parameters crack growth model for 2D crack propagation simulations under general load spectrum. In such model, in order to unify the damage process, the following basic parameters are introduced for describing the overall fatigue process: K, Kmax and the internal stress contribution to Kmax. The coupled usage of Finite Element Method (FEM) and Dual Boundary Element Method (DBEM) is proposed in order to take advantage of the main capabilities of the two methods. The procedure is validated by comparison with in house obtained experimental results and its capability to predict the retardation phenomena following an overload is assessed. The numerical procedure is tested with reference to an MT aluminium specimen (2024HP-T3), whose fatigue calibration parameters had been previously determined using a CT specimen undergoing a constant amplitude load. As a matter of fact the main advantage of the aforementioned procedure is based on the simplicity of the crack growth law calibration, in fact, there is no need to calibrate on various overload levels but few constant amplitude test are sufficient. One of the main capabilities of the implemented procedure is the possibility to simulate load spectrum effects under linear elastic fracture mechanics, being the plastic effects simulated by ad hoc body loads, imposed in the BEM analysis (by means of “load lines”), without the need for any non physical calibration parameters, as in many phenomenological models aimed at load spectra allowance (Willenborg model, Wheeler model, etc.). A curvilinear crack path is simulated and reproduced experimentally: the differences between the calculated and experimental delay cycles after an overload are comparable with the typical scatter of such kind of test.

A coupled FEM-BEM approach for crack growth simulation under fatigue load spectrum

CITARELLA, Roberto Guglielmo;CRICRI', Gabriele;PERRELLA, MICHELE
2006-01-01

Abstract

This paper describes an original implementation of a two-parameters crack growth model for 2D crack propagation simulations under general load spectrum. In such model, in order to unify the damage process, the following basic parameters are introduced for describing the overall fatigue process: K, Kmax and the internal stress contribution to Kmax. The coupled usage of Finite Element Method (FEM) and Dual Boundary Element Method (DBEM) is proposed in order to take advantage of the main capabilities of the two methods. The procedure is validated by comparison with in house obtained experimental results and its capability to predict the retardation phenomena following an overload is assessed. The numerical procedure is tested with reference to an MT aluminium specimen (2024HP-T3), whose fatigue calibration parameters had been previously determined using a CT specimen undergoing a constant amplitude load. As a matter of fact the main advantage of the aforementioned procedure is based on the simplicity of the crack growth law calibration, in fact, there is no need to calibrate on various overload levels but few constant amplitude test are sufficient. One of the main capabilities of the implemented procedure is the possibility to simulate load spectrum effects under linear elastic fracture mechanics, being the plastic effects simulated by ad hoc body loads, imposed in the BEM analysis (by means of “load lines”), without the need for any non physical calibration parameters, as in many phenomenological models aimed at load spectra allowance (Willenborg model, Wheeler model, etc.). A curvilinear crack path is simulated and reproduced experimentally: the differences between the calculated and experimental delay cycles after an overload are comparable with the typical scatter of such kind of test.
978-88-95940-27-4
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/1637018
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