共查询到18条相似文献，搜索用时 15 毫秒
1.
Kyoungsoo Park Glaucio H. Paulino Waldemar Celes Rodrigo Espinha 《International journal for numerical methods in engineering》2012,92(1):1-35
Adaptive mesh refinement and coarsening schemes are proposed for efficient computational simulation of dynamic cohesive fracture. The adaptive mesh refinement consists of a sequence of edge‐split operators, whereas the adaptive mesh coarsening is based on a sequence of vertex‐removal (or edge‐collapse) operators. Nodal perturbation and edge‐swap operators are also employed around the crack tip region to improve crack geometry representation, and cohesive surface elements are adaptively inserted whenever and wherever they are needed by means of an extrinsic cohesive zone model approach. Such adaptive mesh modification events are maintained in conjunction with a topological data structure (TopS). The so‐called PPR potential‐based cohesive model (J. Mech. Phys. Solids 2009; 57 :891–908) is utilized for the constitutive relationship of the cohesive zone model. The examples investigated include mode I fracture, mixed‐mode fracture and crack branching problems. The computational results using mesh adaptivity (refinement and coarsening) are consistent with the results using uniform mesh refinement. The present approach significantly reduces computational cost while exhibiting a multiscale effect that captures both global macro‐crack and local micro‐cracks. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
2.
Zhengyu Zhang Glaucio H. Paulino Waldemar Celes 《International journal for numerical methods in engineering》2007,72(8):893-923
Dynamic crack microbranching processes in brittle materials are investigated by means of a computational fracture mechanics approach using the finite element method with special interface elements and a topological data structure representation. Experiments indicate presence of a limiting crack speed for dynamic crack in brittle materials as well as increasing fracture resistance with crack speed. These phenomena are numerically investigated by means of a cohesive zone model (CZM) to characterize the fracture process. A critical evaluation of intrinsic versus extrinsic CZMs is briefly presented, which highlights the necessity of adopting an extrinsic approach in the current analysis. A novel topology‐based data structure is employed to enable fast and robust manipulation of evolving mesh information when extrinsic cohesive elements are inserted adaptively. Compared to intrinsic CZMs, which include an initial hardening segment in the traction–separation curve, extrinsic CZMs involve additional issues both in implementing the procedure and in interpreting simulation results. These include time discontinuity in stress history, fracture pattern dependence on time step control, and numerical energy balance. These issues are investigated in detail through a ‘quasi‐steady‐state’ crack propagation problem in polymethylmethacrylate. The simulation results compare reasonably well with experimental observations both globally and locally, and demonstrate certain advantageous features of the extrinsic CZM with respect to the intrinsic CZM. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
Habeun Choi Kyoungsoo Park 《International journal for numerical methods in engineering》2019,120(9):1047-1070
To remove mesh bias and provide an accurate crack path representation in mixed-mode investigation, a novel stress recovery technique is proposed in conjunction with a domain integral and element splits. Based on a domain integral and stress recovery technique, a maximum strain energy release rate is estimated to determine a crack path direction. Then, for a given crack path direction, continuum elements are split, and a cohesive surface element is adaptively inserted. One notes that the proposed stress recovery technique provides a more accurate stress field than a standard stress evaluation procedure. The proposed computational framework is verified and validated by solving mode-I and mixed-mode examples. Computational results demonstrate that the domain integral with the stress recovery accurately evaluates a crack path, even with a lower-quality mesh and under a biaxial stress state. Furthermore, the cohesive surface element approach, with the element split in conjunction with the stress recovery and the domain integral, predicts mixed-mode fracture behaviors while removing mesh bias in the crack path representation. Additionally, the condition numbers of stiffness matrices are within the same order of magnitude during cohesive fracture simulation. 相似文献
4.
Fracture characterization under mode I loading of a cement‐based material using the single‐edge‐notched beam loaded in tree‐point‐bending was performed. A new method based on beam theory and crack equivalent concept is proposed to evaluate the Resistance‐curve, which is essential to determine fracture toughness with accuracy. The method considers the existence of a stress relief region in the vicinity of the crack, dispensing crack length monitoring during experiments. A numerical validation was performed by finite element analysis considering a bilinear cohesive damage model. Experimental tests were performed in order to validate the numerical procedure. Digital image correlation technique was used to measure the specimen displacement with accuracy and without interference. Excellent agreement between numerical and experimental load–displacement curves was obtained, which validates the procedure. 相似文献
5.
The present work studies a self‐similar high‐speed expanding crack of mode‐I in a ductile material with a modified cohesive zone model. Compared with existing Dugdale models for moving crack, the new features of the present model are that the normal stress parallel to crack faces is included in the yielding condition in the cohesive zone and traction force in the cohesive zone can be non‐uniform. For a ductile material defined by von Mises criterion without hardening, the present model confirms that the normal stress parallel to crack face increases with increasing crack speed and can be even larger than the normal traction in the cohesive zone, which justifies the necessity of including the normal stress parallel to the crack faces in the yielding condition at high crack speed. In addition, strain hardening effect is examined based on a non‐uniform traction distribution in the cohesive zone. 相似文献
6.
F. Perales S. Bourgeois A. Chrysochoos Y. Monerie 《Engineering Fracture Mechanics》2008,75(11):3378-3398
This paper presents a new computational approach dedicated to the fracture of nonlinear heterogeneous materials. This approach extends the standard periodic homogenization problem to a two field cohesive-volumetric finite element scheme. This two field finite element formulation is written as a generalization Non-Smooth Contact Dynamics framework involving Frictional Cohesive Zone Models. The associated numerical platform allows to simulate, at finite strain, the fracture of nonlinear composites from crack initiation to post-fracture behavior. The ability of this computational approach is illustrated by the fracture of the hydrided Zircaloy under transient loading. 相似文献
7.
Lin Chen Bin Li René de Borst 《International journal for numerical methods in engineering》2019,120(4):433-446
The analysis of (dynamic) fracture often requires multiple changes to the discretisation during crack propagation. The state vector from the previous time step must then be transferred to provide the initial values of the next time step. A novel methodology based on a least-squares fit is proposed for this mapping. The energy balance is taken as a constraint in the mapping, which results in a complete energy preservation. Apart from capturing the physics better, this also has advantages for numerical stability. To further improve the accuracy, Powell-Sabin B-splines, which are based on triangles, have been used for the discretisation. Since continuity of the displacement field holds at crack tips for Powell-Sabin B-splines, the stresses at and around crack tips are captured much more accurately than when using elements with a standard Lagrangian interpolation, or with NURBS and T-splines. The versatility and accuracy of the approach to simulate dynamic crack propagation are assessed in two case studies, featuring mode-I and mixed-mode crack propagation. 相似文献
8.
Hyunil Baek Chulmin Kweon Kyoungsoo Park 《International journal for numerical methods in engineering》2020,121(24):5719-5741
In this study, a computational framework is proposed to investigate multiscale dynamic fracture phenomena in materials with microstructures. The micro- and macro-scales of a composite material are integrated by introducing an adaptive microstructure representation. Then, the far and local fields are simultaneously computed using the equation of motion, which satisfies the boundary conditions between the two fields. Cohesive surface elements are dynamically inserted where and when needed, and the Park-Paulino-Roesler cohesive model is employed to approximate nonlinear fracture processes in a local field. A topology-based data structure is utilized to efficiently handle adjacency information during mesh modification events. The efficiency and validity of the proposed computational framework are demonstrated by checking the energy balances and comparing the results of the proposed computation with direct computations. Furthermore, the effects of microstructural properties, such as interfacial bonding strength and unit cell arrangement, on the dynamic fracture behavior are investigated. The computational results demonstrate that local crack patterns depend on the combination of microstructural properties such as unit cell arrangement and interfacial bonding strength; therefore, the microstructure of a material should be carefully considered for dynamic cohesive fracture investigations. 相似文献
9.
薄膜/基底结构是微电子学和材料科学中广泛应用的典型结构。由于加工工艺中材料力学、热学性能失配等原因导致的薄膜中出现的残余应力,是界面裂纹的萌生和扩展的重要原因。采用三参数(Γ0, /σy,t)的修正的断裂过程区结合力模型,讨论了在塑性氛围下裂尖解理断裂的过程,裂尖应力分布,裂尖形貌和表征裂纹尖端断裂过程区特征参数对断裂过程的影响,并应用到均质金属薄膜/陶瓷基底结构中残余应力导致界面裂纹起裂和扩展的全过程分析中。 相似文献
10.
Leonardo Snozzi Jean‐François Molinari 《International journal for numerical methods in engineering》2013,93(5):510-526
We present a model that combines interface debonding and frictional contact. The onset of fracture is explicitly modeled using the well‐known cohesive approach. Whereas the debonding process is controlled by a new extrinsic traction separation law, which accounts for mode mixity, and yields two separate values for energy dissipation in mode I and mode II loading, the impenetrability condition is enforced with a contact algorithm. We resort to the classical law of unilateral contact and Coulomb friction. The contact algorithm is coupled together to the cohesive approach in order to have a continuous transition from crack nucleation to the pure frictional state after complete decohesion. We validate our model by simulating a shear test on a masonry wallette and by reproducing an experimental test on a masonry wall loaded in compression and shear. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
11.
X. J. Fang Q. D. Yang B. N. Cox Z. Q. Zhou 《International journal for numerical methods in engineering》2011,88(9):841-861
We demonstrate that traditional cohesive zone (CZ) elements cannot be accurate when used in conjunction with solid elements with arbitrary intra‐element cracking capability, because they cannot capture the load transfer between cohesive interfaces and the solid elements when crack bifurcation or coalescence occurs. An augmented cohesive zone (ACZ) element based on the augmented finite element method formulation is therefore proposed. The new element allows for arbitrary separation of the cohesive element in accordance with the crack configuration of the abutting solid elements, thus correctly maintaining the non‐linear coupling between merging or bifurcating cracks. Numerical accuracy and effectiveness of the proposed ACZ element are demonstrated through several examples. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
12.
T. Pannachet L. J. Sluys H. Askes 《International journal for numerical methods in engineering》2009,78(5):528-563
Discontinuous failure is simulated via the introduction of a geometrical discontinuity. The cohesive zone is modelled via the use of the partition‐of‐unity property of the finite element interpolation. By this approach, a crack can pass through the elements without any restriction to the underlying mesh. Despite such a feature, it has been confirmed that a sufficiently fine mesh discretization still needs to be ensured in order to obtain a correct crack path and mechanical response. The p‐adaptive scheme, driven by error in an energy norm measure or a goal‐oriented measure, has been examined due to its implementational simplicity. The results have shown that, if considering only increasing the polynomial degree, the p‐approach can greatly improve the results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
13.
14.
Umberto De Maio Fabrizio Greco Lorenzo Leonetti Raimondo Luciano Paolo Nevone Blasi Sabrina Vantadori 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(2):221-241
In this work, a refined interelement diffuse fracture theoretical model, based on a cohesive finite element approach, is proposed for concrete and other quasibrittle materials. This model takes advantage of a novel micromechanics‐based calibration technique for reducing the artificial compliance associated with the adopted intrinsic formulation. By means of this technique, the required values for the elastic stiffness parameters to obtain nearly invisible cohesive interfaces are provided. Furthermore, the mesh‐induced toughening effect, essentially related to the artificial crack tortuosity caused by the different orientations of the interelement cohesive interfaces, is numerically investigated by performing comparisons with an additional fracture model, newly introduced for the purpose of numerical validation. These comparisons are presented to assess the reliability and the numerical accuracy of the proposed fracture approach. 相似文献
15.
Yang Jiao Jacob Fish 《International journal for numerical methods in engineering》2015,104(11):1008-1037
A methodology aimed at addressing computational complexity of analyzing delamination in large structural components made of laminated composites is proposed. The classical ply‐by‐ply discretization of individual layers may increase the size of the problem by an order of magnitude in comparison with the laminated shell or plate element meshes. The paper features delamination indicators that pinpoint the onset and propagation of delamination fronts with striking accuracy. Once the location of delamination has been identified, the discrete solution space of the classical laminated plate/shell element is hierarchically enriched by a combination of weak and strong discontinuities to adaptively track the evolution of delamination fronts. The so‐called adaptive s‐method proposed herein is equivalent in terms of approximation space to the extended finite element method but offers sparser matrices and added flexibility in transitioning from weak to strong discontinuities. Numerical examples suggest that despite an overhead that comes with adaptivity, the adaptive s‐method is computationally advantageous over the classical ply‐by‐ply discretization, especially as the problem size increases. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
16.
S. H. SONG M. P. WAGONER G. H. PAULINO W. G. BUTTLAR 《Fatigue & Fracture of Engineering Materials & Structures》2008,31(10):850-856
Recent work with fracture characterization of asphalt concrete has shown that a cohesive zone model (CZM) provides insight into the fracture process of the materials. However, a current approach to estimate fracture energy, i.e., in terms of area of force versus crack mouth opening displacement (CMOD), for asphalt concrete overpredicts its magnitude. Therefore, the δ25 parameter, which was inspired by the δ5 concept of Schwalbe and co‐workers, is proposed as an operational definition of a crack tip opening displacement (CTOD). The δ25 measurement is incorporated into an experimental study of validation of its usefulness with asphalt concrete, and is utilized to estimate fracture energy. The work presented herein validates the δ25 parameter for asphalt concrete, describes the experimental techniques for utilizing the δ25 parameter, and presents three‐dimensional (3D) CZM simulations with a specially tailored cohesive relation. The integration of the δ25 parameter and new cohesive model has provided further insight into the fracture process of asphalt concrete with relatively good agreement between experimental results and numerical simulations. 相似文献
17.
N. Nourbakhshnia G. R. Liu 《International journal for numerical methods in engineering》2011,88(5):473-492
In the edge‐based smoothed finite element method (ES‐FEM), one needs only the assumed displacement values (not the derivatives) on the boundary of the edge‐based smoothing domains to compute the stiffness matrix of the system. Adopting this important feature, a five‐node crack‐tip element is employed in this paper to produce a proper stress singularity near the crack tip based on a basic mesh of linear triangular elements that can be generated automatically for problems with complicated geometries. The singular ES‐FEM is then formulated and used to simulate the crack propagation in various settings, using a largely coarse mesh with a few layers of fine mesh near the crack tip. The results demonstrate that the singular ES‐FEM is much more accurate than X‐FEM and the existing FEM. Moreover, the excellent agreement between numerical results and the reference observations shows that the singular ES‐FEM offers an efficient and high‐quality solution for crack propagation problems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
18.
P. Moonen L. J. Sluys J. Carmeliet 《International journal for numerical methods in engineering》2010,84(9):1009-1037
A macroscopic framework for the simulation of physical degradation processes in quasi‐brittle porous materials is proposed. The framework employs the partition of unity (PU) concept and introduces a cohesive zone model, capturing the entire failure process starting from the growth and coalescence of micro‐defects until the formation of macro‐cracks. The framework incorporates the interaction between the failure process and the heat and mass transfer in the porous medium. As an example, physical degradation of an outside render is studied. The analysis illustrates that both material and interface failure can be investigated with this formulation. Depending on the boundary conditions, either one dominant crack or a network of small cracks is formed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献