Strain-injection and crack-path field techniques for 3D crack-propagation modelling in quasi-brittle materials

This paper presents a finite element approach for modelling three-dimensional crack propagation in quasi-brittle materials, based on the strain injection and the crack-path field techniques. These numerical techniques were already tested and validated by static and dynamic simulations in 2D classical benchmarks [Dias et al., in: Monograph CIMNE No-134. International Center for Numerical Methods in Engineering, Barcelona, (2012); Oliver et al. in Comput Methods Appl Mech Eng 274:289–348, (2014); Lloberas-Valls et al. in Comput Methods Appl Mech Eng 308:499–534, (2016)] and, also, for modelling tensile crack propagation in real concrete structures, like concrete gravity dams [Dias et al. in Eng Fract Mech 154:288–310, (2016)]. The main advantages of the methodology are the low computational cost and the independence of the results on the size and orientation of the finite element mesh. These advantages were highlighted in previous works by the authors and motivate the present extension to 3D cases. The proposed methodology is implemented in the finite element framework using continuum constitutive models equipped with strain softening and consists, essentially, in injecting the elements candidate to capture the cracks with some goal oriented strain modes for improving the performance of the injected elements for simulating propagating displacement discontinuities. The goal-oriented strain modes are introduced by resorting to mixed formulations and to the Continuum Strong Discontinuity Approach (CSDA), while the crack position inside the finite elements is retrieved by resorting to the crack-path field technique. Representative numerical simulations in 3D benchmarks show that the advantages of the methodology already pointed out in 2D are kept in 3D scenariosPeer ReviewedPostprint (author's final draft

Crack-path field and strain-injection techniques in computational modeling of propagating material failure

The work presents two new numerical techniques devised for modeling propagating material failure, i.e. cracks in fracture mechanics or slip-lines in soil mechanics. The first one is termed crack-path-field technique and is conceived for the identification of the path of those cracks, or slip-lines, represented by strain-localization based solutions of the material failure problem. The second one is termed strain-injection, and consists of a procedure to insert, during specific stages of the simulation and in selected areas of the domain of analysis, goal oriented specific strain fields via mixed finite element formulations. In the approach, a first injection, of elemental constant strain modes (CSM) in quadrilaterals, is used, in combination of the crack-path-field technique, for obtaining reliable information that anticipates the position of the crack-path. Based on this information, in a subsequent stage, a discontinuous displacement mode (DDM) is efficiently injected, ensuring the required continuity of the crack-path across sides of contiguous elements. Combination of both techniques results in an efficient and robust procedure based on the staggered resolution of the crack-path-field and the mechanical failure problems. It provides the classical advantages of the “intra-elemental” methods for capturing complex propagating displacement discontinuities in coarse meshes, as E-FEM or X-FEM methods, with the non-code-invasive character of the crack-path-field technique. Numerical representative simulations of a wide range of benchmarks, in terms of the type of material and the failure problem, show the broad applicability, accuracy and robustness of the proposed methodology. The finite element code used for the simulations is open-source and available at http://www.cimne.com/compdesmat/.Postprint (published version

Strain injection techniques for modeling 3D crack propagation

This work presents some novel results obtained by using the strain injection techniques for modeling crack propagation in challenging 3D benchmark tests. The techniques were already tested and validated by static and dynamic simulations in 2D [1-4], so the main goal of this paper is to verify if the most important advantages of the method, low computational cost and independence of the results on the finite element mesh, are kept in 3D. The methodology, implemented in the finite element framework, consists essentially in injecting those elements that are going to capture the cracks with some enhanced strain modes for improving the performance of the elements for modeling propagating material failure.Peer ReviewedPostprint (author's final draft

Strain injection techniques for modeling 3D crack propagation

This work presents some novel results obtained by using the strain injection techniques for modeling crack propagation in challenging 3D benchmark tests. The techniques were already tested and validated by static and dynamic simulations in 2D [1-4], so the main goal of this paper is to verify if the most important advantages of the method, low computational cost and independence of the results on the finite element mesh, are kept in 3D. The methodology, implemented in the finite element framework, consists essentially in injecting those elements that are going to capture the cracks with some enhanced strain modes for improving the performance of the elements for modeling propagating material failure.Peer Reviewe

Studies at the DNA level of human properdin

SIGLEAvailable from British Library Document Supply Centre- DSC:D173859 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Glycosaminoglycans in gingival crevicular fluid in relation to bone resorption

SIGLEAvailable from British Library Document Supply Centre- DSC:DX173937 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Crack path field and strain injection techniques in dynamic fracture simulations

Dynamic fracture phenomena are studied employing low cost computational tools based on Finite Elements with Embedded strong discontinuities (E-FEM). Fracture nucleation and propagation are accounted for through the injection of discontinuous strain and displacement modes inside the finite elements. The Crack Path Field technique is employed to compute the trace of the strong discontinuity during fracture propagation. Unstable crack propagation and crack branching are observed upon increasing loading rates. The variation in terms of crack pattern and energy dissipation is studied and a good correlation is found between the maximum experimental crack speed and maximum dissipation at the onset of branching. Comparable results are obtained against simulations employing supraelemental techniques, such as phase-field and gradient damage models, considering coarser discretizations which can differ by two orders of magnitude