The emphasis of this work lies in the development of a numerical method which is capable of representing the complex physical phenomena arising in the case of crack branching in brittle materials. In abaqusstandard plain concrete can also be analyzed with the smeared crack concrete model described in an inelastic constitutive model for concrete, section 4. Experiments on dynamic fracture in brittle amorphous materials have produced results1 that agree with theoretical predictions for. Sluys, a numerical study on crack branching in quasibrittle materials with a new effective ratedependent nonlocal damage. We address the simulation of dynamic crack propagation in brittle materials using a regularized phasefield description, which can also be interpreted as a damagegradient model. Using statistical arguments to establish relationships between the energies associated with crack branching and the mott parameters that.
Most such techniques involve one of two mechanisms. The model rests on a scenario of crack branching based on reasonable assumptions and on exact dynamic results for the antiplane branching problem. Dynamics of crack propagation in brittle materials. If cracks are branching it indicates that the stress is high and the material is unable to. Based on the results of the singleedge notch test it is concluded that branching does not occur at a specific, material dependent, crack velocity. In abaqusstandard plain concrete can also be analyzed with the smeared crack concrete model described in an inelastic constitutive model for concrete.
We explain under what conditions the crack propagation speed depends on the horizon size. Confirming the continuum theory of dynamic brittle. The objective of this paper is to provide further evidence in support of the dynamic crack branching criterion advanced by the authors. A schematic illustration for the case of microscale crack branching is shown in fig. Brittle materials are at greater risk of being exposed to abrupt fractures caused by the nucleation and development of numerous microcracks. In these materials, crack branching andor crack deflection is readily produced.
We are analyzing the continuum scale modeling of crack branching and damage mechanism transitions that occur during dynamic fracture of textile composites. The problem of dynamic symmetric branching of an initial single brittle crack propagating at a given speed under plane loading. The griffith energy criterion and the principle of local symmetry provide necessary conditions. Aug 21, 2017 understanding brittle crack behaviors to design stronger materials. Theoryofdynamiccrackbranchinginbrittlematerials arxiv. Griffiths energy criterion and the principle of local symmetry are used to determine the cracks paths. This phenomenological model is mesh objective and reproduces the major phenomena associated with crack propagation and branching in quasi brittle materials. We demonstrate that a number of longstanding questions in the dynamic fracture of amorphous, brittle materials may be understood in this picture. The mechanism and patterns of rapid crack propagation and branching in an amorphous polymer were studied on the fracture of flat samples of polymethylmethacrylate with an initial side notch under tension at room and low temperatures. An example of crack branching in a nominally brittle material homalite is addressed and we show that crack branching takes place without wave interaction. We first present a picture of fracture in which numerous effects commonly observed in dynamic fracture may be understood as resulting from an intrinsic microbranching instability of a rapidly moving crack. Why are cracks in ductile materials said to be stable, but.
Read dynamic crack branching and curving in brittle polymers, international journal of solids and structures on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Comparisons with experimentally obtained values are made for the crack tip propagation speed with three different peridynamic horizons. Fiber reinforced composites are quasi brittle materials with a highly heterogeneous microstructure. The problem of dynamic symmetric branching of a tensile crack propagating in a brittle material is studied within linear elastic fracture mechanics theory. The crack branching criterion on the other hand, requires a critical stress intensity factor to trigger crack branching and a crack curving criterion for predicting the crack branching angle 4,6. The stress needed to fracture bulk glass is around 100 mpa 15,000 psi. Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. Crack branching and fracture mirror data of glasses and. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the materials resistance to fracture. Crack branching and fracture mirror data of glasses and advanced ceramics 0 sung r. If tensile force is applied, these materials can be stretched into a wire, but if compressive force is applied, they can be deformed. A numerical study on crack branching in quasibrittle. Studies of dynamic crack propagation and crack branching with.
Study on crack curving and branching mechanism in quasibrittle. Dec 01, 2016 read dynamic crack branching and curving in brittle polymers, international journal of solids and structures on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. We explain under what conditions the crack propagation speed depends on the horizon size and the role of incident stress waves on this speed. Comparisons with experimentally obtained values are made for the cracktip propagation speed with three different peridynamic horizons.
The problem of dynamic symmetric branching of an initial single brittle crack propagating at a given speed under plane loading conditions is studied within a continuum mechanics approach. It was established that crack branching occurs when the critical level of fracture stress is achieved. Brittle fracture dynamics with arbitrary paths iii. Although this brittle cracking model can also be useful for other materials, such as ceramics and brittle rocks, it. Theory of dynamic crack branching in brittle materials springerlink. We investigate the capacity of such a simple model to reproduce specific. This principle generalizes to other classes of material. Predicting their dynamic failure behavior is a major challenge. The proposed phenomenological model is mesh objective and reproduces the major phenomena associated with crack propagation and branching in quasi brittle materials.
Theory of dynamic crack branching in brittle materials. Studies of dynamic crack propagation and crack branching. Among these are the transition to crack branching, roughness and the origin of nontrivial fracture. Keywords dynamic fracture crack branching brittle fracture peridynamics nonlocal methods meshfree methods 1 introduction 1.
Note that as load increases the point of first crack branching gets closer to initial crack tip position. Although this brittle cracking model can also be useful for other materials, such as ceramics and brittle rocks, it is primarily intended to model plain concrete. Naturally brittle materials, such as glass, are not difficult to toughen effectively. Sluys, a numerical study on crack branching in quasi brittle materials with a new effective ratedependent nonlocal damage model, engineering fracture mechanics, 182, 689, 2017. Theory of dynamic crack branching in brittle materials 2008.
Fiber reinforced composites are quasibrittle materials with a highly heterogeneous microstructure. They have the tendency to hold the deformation that occurs in the plastic region. Griffiths energy criterion and the principle of local. In this paper a systematic analysis of the branching problem is made, and due to rea. To elucidate this mechanism, the team plans to investigate the 3d phenomenon of micro branching, when the main crack splits into many microcracks, to understand its origins in bulk samples of brittle materials. Choi cleveland state university cleveland, ohio 44115 and john p. Griffiths work was motivated by two contradictory facts. Ductile materials are materials that can be plastically twisted with no crack.
Sep 05, 2006 the results are interesting since they explain within a continuum mechanics approach the main features of the branching instabilities of fast cracks in brittle materials, i. The mechanism for the characteristics of crack branching at different propagation speeds. Crack branching and fracture mirror data of glasses and advanced ceramics sung r. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. This particular setup is typically used by experimentalists to measure the dynamic fracture properties of brittle materials using imaging techniques and. Theory of dynamic crack branching in brittle mater ials 247 for the sake of clearness, the second section of this paper summarizes the results obtained for the branching problem. The fracture process is accompanied by the formation of. Peridynamics, which is a reformulation of contin uum mechanics silling 2000. In amorphous solids, by contrast, the lack of a crystalline structure results in a conchoidal fracture, with cracks proceeding normal to the applied tension. Theory of dynamic crack branching in brittle materials core. Fracture is the separation of an object or material into two or more pieces under the action of stress. Microstructural observations of brittle materials indicated that a variety of microdefect events can be responsible not only for inelastic behaviour, but also for macroscopic crack front irregularity.
Keywords dynamic fracture crack branching brittle materials phase eld model damagegradient model 1 introduction understanding the various mechanisms governing the dynamic propagation of a crack in a brittle medium is still a challenge. Sep 24, 2017 all these are mechanisms in which quasi brittle materials dissipate energy. Peridynamics, which is a reformulation of continuum mechanics silling 2000. To elucidate this mechanism, the team plans to investigate the 3d phenomenon of microbranching, when the main crack splits into many microcracks, to understand its. Ill deviate from this by showing a little of the mathematics. The fractal effect of irregularity of crack branching on. Dynamic crack branching and curving in brittle polymers. Pdf theory of dynamic crack branching in brittle materials. Branchingu i da126 444 further studies i nrshington univ. Fracture mechanics was developed during world war i by english aeronautical engineer a. A cracking model for concrete and other brittle materials. Understanding brittle crack behaviors to design stronger materials. Crack propagation is the basic mechanism of materials failure. Branched cracks are often observed in brittle materials and structures.
This contribution presents a numerical study towards the propagation and branching of cracks in quasibrittle materials, using a new effective ratedependent damage model, enhanced by a stressbased nonlocal sbnl regularization scheme. Confirming the continuum theory of dynamic brittle fracture. Atomistic aspects of crack propagation in brittle materials. The dynamics of rapidly moving tensile cracks in brittle. All these are mechanisms in which quasibrittle materials dissipate energy. This irregularity produces an increase in the fracture toughness of the material. Polycrystalline minerals most fundamental research on crack propagation behaviour has been directed towards cleavage fracture in single crystals or crack propagation in brittle amorphous materials.
The di culty lies in the strong interaction between stress concentrations at the crack tip. The problem of dynamic symmetric branching of a tensile crack propagating in a brittle material is studied within linear elastic fracture. Various microscopy tools are used to examine features on the fracture surfaces of brittle materials that are the direct consequence of crack perturbations during propagation. Understanding brittle crack behaviors to design stronger. Cyclic crack growth occurs only in intergranular fracturetype ceramics, as described above. Jan 20, 2010 in this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement mconvergence and under decreasing the peridynamic horizon. Theory of dynamic crack branching in brittle materials 247 for the sake of clearness, the second section of this paper summarizes the results obtained for the branching problem. Citeseerx document details isaac councill, lee giles, pradeep teregowda. In brittle crystalline materials, fracture can occur by cleavage as the result of tensile stress acting normal to crystallographic planes with low bonding cleavage planes. Effect of loading magnitude on dynamic crack propagation. Pdf atomistic aspects of crack propagation in brittle. Dynamic crack propagation with a variational phasefield. In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement mconvergence and under decreasing the peridynamic horizon. Microbranching instability and the dynamic fracture of.
This phenomenological model is mesh objective and reproduces the major phenomena associated with crack propagation and branching in quasibrittle materials. Crack branching characteristics at different propagation speeds. The griffith energy criterion and the principle of local symmetry provide necessary conditions for the onset of dynamic branching instability and for the. If a displacement develops perpendicular to the surface of displacement, it is called a normal tensile crack or simply a crack. Benefiting from a variational framework, the dynamic evolution of the mechanical fields are obtained as a succession of energy minimizations. Others here have presented the physical bases in their answers. Our results reproduce within a simplified 2d continuum mechanics approach the main experimental features of the branching instability of fast cracks in brittle materials. Griffith thus the term griffith crack to explain the failure of brittle materials. The phenomenology of bilttle fragmentation was examined previously, and a simple model was developed utilizing the concept of crack branching. The fractal effect of irregularity of crack branching on the. The mechanism of crack curving and branching in quasibrittle materials under dynamic biaxial loading is investigated.
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