Extended finite element method for three-dimensional crack modelling

Stress intensity factors for cracks in grooved rolls used for hot-rolling

On the calculation of stress intensity factors for surface cracks in welded pipe–plate and tubular joints

Weight function method for three dimensional crack problems—II. Application to surface cracks at a hole in finite thickness plates under stress gradients

Methods of calculating stress intensity factors for nozzle corner cracks

A method is developed to evaluate the stress intensity factors (SIFs) for semi-elliptical circumferential cracks located at the inner wall of a pipe under arbitrary welding residual stress distribution. To accomplish this, at first, the three-dimensional finite element analysis (FEA) is performed employing singular elements along the crack front. Next, the weight function (WF) is incorporated in conjunction with the finite element results to predict the SIFs of semi-elliptical circumferential cracks in pipes. Then, the presented WF is extended to estimate the SIFs of fully circumferential cracks in pipes. Moreover, a closed-form formulation of SIFs is presented as a function of arbitrary loading condition and crack geometry. Finally, the closed-form relation has been used to predict the stress intensity factors of circumferential cracks under highly nonlinear residual stress fields. Comparison of the results and those in the literature shows an acceptable agreement.

This paper describes the application of the complex variable meshless manifold method (CVMMM) to stress intensity factor analyses of structures containing interface cracks between dissimilar materials. A discontinuous function and the near‐tip asymptotic displacement functions are added to the CVMMM approximation using the framework of complex variable moving least‐squares (CVMLS) approximation. This enables the domain to be modeled by CVMMM without explicitly meshing the crack surfaces. The enriched crack‐tip functions are chosen as those that span the asymptotic displacement fields for an interfacial crack. The complex stress intensity factors for bimaterial interfacial cracks were numerically evaluated using the method. Good agreement between the numerical results and the reference solutions for benchmark interfacial crack problems is realized.

Computation of stress intensity factors for interfacial cracks

2D weight functions of stress intensity factors for high aspect ratio semi-elliptical surface cracks in finite thickness plate

Perturbation mapping method for sensitivity analysis of three-dimensional cracks near a free surface

In this study, mode I stress intensity factors for a three-dimensional finite cracked body with arbitrary shape and subjected to arbitrary loading is presented by using the boundary weight function method. The weight function is a universal function for a given cracked body and can be obtained from any arbitrary loading system. A numerical finite element method for the determination of weight function relevant to cracked bodies with finite dimensions is used. Explicit boundary weight functions are successfully demonstrated by using the least-squares fitting procedure for elliptical quarter-corner crack and embedded elliptical crack in parallelepipedic finite bodies. If the stress distribution of a cut-out parallelepipedic cracked body from any arbitrary shape of cracked body subjected to arbitrary loading is determined, the mode I stress intensity factors for the cracked body can be obtained from the predetermined boundary weight functions by a simple surface integration. Comparison of the calculated results with some available solutions in the published literature confirms the efficiency and accuracy of the proposed boundary weight function method.

Development and industrial applications of X-FEM axisymmetric model for fracture mechanics

A procedure is formulated to derive approximate stress intensity factors for both part-through and through-the-thickness cracks originating at open holes and holes containing either loaded or unloaded close tolerance fasteners. The procedure is checked with known solutions for stress intensity factors of one or two through-the-thickness cracks emanating from an open hole in a plate subjected to uniaxial or biaxial loading. Stress intensity factors computed from this procedure for the above mentioned cases agree within seven percent of known results for the crack length to hole radius ratios, L/r, of 0.05 ≤ L/r < ∞. The procedure is then used to derive stress intensity factors for through cracks at loaded close tolerance fasteners in a plate, and for semi-elliptical cracks at open holes and at loaded and unloaded close tolerance fastener filled holes in a thick plate. Stress intensity factors for these part-through cracks are presented in graphical forms as a function of position around the crack periphery, for various crack aspect ratios and crack length to hole radius ratios. Finally, these stress intensity solutions for semi-elliptical cracks at a fastener hole in a thick plate are used to estimate stress intensity factors for quarter-elliptical cracks originating at a fastener hole in a finite thickness plate.

Stress intensity factors for axial semi-elliptical surface cracks and embedded elliptical cracks at longitudinal butt welded joints of steel-lined pressure tunnels and shafts considering weld shape

Stress intensity factors and weight functions for high aspect ratio semi-elliptical surface cracks in finite-thickness plates

A straight-forward method for calculating the stress intensity factors (or the energy release rate and mode mixity) for interfacial cracks in bi-materials has been developed. An existing method for homogeneous materials, based on the computation of the energy release rate from the nodal forces and displacements given by a finite element analysis, was modified to include the mismatch in material properties. Thick thermal barrier coatings usually fail as a result of cracking near the interface. The influence of the thickness and the edge angle of the coating on the energy release rate and mode mixity for a small edge crack at the interface of a TBC system subjected to thermal loading was investigated. It was established that the high energy release rates obtained for thick coatings can be reduced by decreasing the edge angle of the coating. Additionally a comparison with energy release rates given by J-integral computations has been done.