A methodology for crack tip mesh design

Menandro, Fernando César Meira; Moyer, E. T.; Liebowitz, Harold

doi:10.1016/0013-7944(94)e0056-m

Cited by 12 publications

(6 citation statements)

References 4 publications

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“…The possible errors due to the choice in extrapolation range are therefore most likely considerably lower than those mentioned above. This indicates a considerable weakness in the displacement extrapolation technique however, which is rarely emphasized in relevant reviews …”

Section: Resultsmentioning

confidence: 99%

“…However, when the displacement extrapolation technique is used, a finer crack tip mesh is required, and few general recommendations exist. Menandro et al optimized the crack tip mesh design for this technique for three basic problems, and some of those recommendations were taken into account here.…”

Section: Fe Analysismentioning

confidence: 99%

“…If the interaction integral method is used to extract the stress intensity factor, the crack tip mesh may be relatively coarse, and sizing recommendations may be found, eg, in Cook et al 36 However, when the displacement extrapolation technique is used, a finer crack tip mesh is required, and few general recommendations exist. Menandro et al 46 optimized the crack tip mesh design for this technique for three basic problems, and some of those recommendations were taken into account here.…”

Section: Fe Modellingmentioning

confidence: 99%

“…Eight elements were used in each half ring in the crack tip mesh, as stated to be optimal by Menandro et al 46 This also enables an effective transition to the structured mesh away from the crack tip, as shown in Figure 4. The number of rings was adjusted to keep a smooth transition in element size.…”

Section: Fe Modellingmentioning

confidence: 99%

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Stress intensity factors for circumferential through‐wall cracks in thin‐walled cylindrical shells subjected to tension and torsion

Rege

Pavlou

2019

Fatigue Fract Eng Mat Struct

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In order to assess the structural integrity of tubular members or pipes containing circumferential through‐wall cracks, their stress intensity factor solutions are required. While stress intensity factors for tension and bending are available, few solutions exist for the case of torsion, even though these components may also be subjected to torque. In this paper, the finite element method is used to compute the stress intensity factors for this geometry under tension and torsion. Shell elements are employed to compute the results for thin shells by the means of the displacement extrapolation technique. The computed results indicate that the available analytical solution for torsional loading, which is based on shallow shell theory, is nonconservative for long cracks in thin shells. Shallow shell theory is in general not applicable to long cracks, and the present work is therefore able to provide solutions for a wider range of crack lengths than what is currently available.

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Section: Resultsmentioning

confidence: 99%

Section: Fe Analysismentioning

confidence: 99%

Section: Fe Modellingmentioning

confidence: 99%

Section: Fe Modellingmentioning

confidence: 99%

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Stress intensity factors for circumferential through‐wall cracks in thin‐walled cylindrical shells subjected to tension and torsion

Rege

Pavlou

2019

Fatigue Fract Eng Mat Struct

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“…When used at the crack tip, these so-called "quarter-point elements" [24] have a reasonably accurate stiffness, but the local values of stress and displacement within the quarter-point elements are poor [22]. The nodal displacements for these elements should therefore be omitted when calculating K. Recommendations for generating a suitable mesh with quarter-point elements for evaluating K I by the displacement method have been given by Menandro, et al [25] and Guinea, et al [26], and a typical example of the crack tip mesh is shown in Figure 2. Note that the quarter-point (8-node quadratic rectangle) elements are collapsed down to triangles, where each element has three nodes located at the crack tip.…”

Section: Finite Elements At the Crack Tipmentioning

confidence: 99%

A review of fatigue crack propagation modelling techniques using FEM and XFEM

Rege

Lemu

2017

IOP Conf. Ser.: Mater. Sci. Eng.

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The study of the dissipation heat flow and the acoustic emission during the fatigue crack propagation in the metal A N Vshivkov, A Yu Iziumova, I A Panteleev et al. noAbstract. Fatigue is one of the main causes of failures in mechanical and structural systems. Offshore installations, in particular, are susceptible to fatigue failure due to their exposure to the combination of wind loads, wave loads and currents. In order to assess the safety of the components of these installations, the expected lifetime of the component needs to be estimated. The fatigue life is the sum of the number of loading cycles required for a fatigue crack to initiate, and the number of cycles required for the crack to propagate before sudden fracture occurs. Since analytical determination of the fatigue crack propagation life in real geometries is rarely viable, crack propagation problems are normally solved using some computational method. In this review the use of the finite element method (FEM) and the extended finite element method (XFEM) to model fatigue crack propagation is discussed. The basic techniques are presented, together with some of the recent developments. IntroductionComponents which are subjected to fluctuating loads are found virtually everywhere: Vehicles and other machinery contain rotating axles and gears, pressure vessels and piping may be subjected to pressure fluctuations (e.g. water hammer) or repeated temperature changes, structural members in bridges are subjected to traffic loads and wind loads, while those in ships and offshore structures are subjected to the combination of wind loads, wave loads and currents. If the components are subjected to a fluctuating load of a certain magnitude for a sufficient amount of time, small cracks will nucleate in the material. Over time, the cracks will propagate, up to the point where the remaining cross-section of the component is not able to carry the load, at which the component will be subjected to sudden fracture [1]. This process is called fatigue, and is one of the main causes of failures in structural and mechanical components [2]. In order to assess the safety of the component, engineers need to estimate its expected lifetime. The fatigue life is the sum of the number of loading cycles required for a fatigue crack to nucleate/initiate, and the number of cycles required for the crack to propagate until its critical size has been reached [2,3]. In this paper, computational methods to estimate the lifespan of a propagating crack whose initial geometry is known will be considered.Estimations of the fatigue crack propagation rate, da/dN, are normally based on a relation with the range of the stress intensity factor, ΔK, which is a linear elastic fracture mechanics (LEFM) parameter for quantifying the load and geometry of the crack. Paris, Gomez and Anderson [4] first proposed the existence of such a relation in 1961, and its simplest form is the Paris law [5]:

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