scholarly journals Evaluation Method for Cohesive Crack Propagation in Fragile Locations of RCC Dam Using XFEM

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 58
Author(s):  
Erfeng Zhao ◽  
Bo Li
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Evaluation Method ◽  
Crack Tip ◽  
Displacement Function ◽  
Cohesive Crack ◽  
Propagation Path ◽  
Dam Failure ◽  
Strong Discontinuity ◽  
Term Operation

Roller compacted concrete (RCC) dams own a large number of horizontal construction layers, which can easily lead to weak joints among layers and generate interlayer joints with different scales to reduce the dam bearing capacity. In this study, extended finite element method (XFEM) is used to simulate crack propagation, the finite element description is first taken on the strong discontinuity. Subsequently, the displacement function of the crack-tip in the quadrilateral element and the geometric determination method of the crack-tip strengthening region are established. Afterwards, the discrete form of the governing equation is derived and the XFEM increment discretization method of the cohesive crack with the crack-tip reinforcement is proposed using the virtual node method to represent the discontinuity of the fracture element. These methods are validated through simulating mixed-mode cracking of one-sided notched asymmetric four-point bending beam. Eventually, the proposed methods are applied to RCC gravity dam to study the development rule and propagation path of the interlayer joints, so as to evaluate the effect of different lengths of the interlayer joints on the dam structural performance. The estimated critical values of dam deformation are helpful to prevent the dam failure during long term operation.

scholarly journals Vector form Intrinsic Finite Element Based Approach to Simulate Crack Propagation

2017 ◽  
Vol 33 (6) ◽  
pp. 797-812 ◽  
Author(s):  
Y. F. Duan ◽  
S. M. Wang ◽  
R. Z. Wang ◽  
C. Y. Wang ◽  
E. C. Ting
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Integral Method ◽  
Crack Tip ◽  
Cohesive Crack ◽  
Vector Form ◽  
Mass Particle ◽  
Integral Methods ◽  
Stiffness Matrices ◽  
Cohesive Crack Propagation

AbstractThis paper presents a new approach to simulate the propagation of elastic and cohesive cracks under mode-I loading based on the vector form intrinsic finite element method. The proposed approach can handle crack propagation without requiring global stiffness matrices and extra weak stiffness elements. The structure is simulated by mass particles whose motions are governed by the Newton's second law. Elastic and cohesive crack propagation are simulated by proposed VFIFE-J-integral and VFIFE-FCM methods, respectively. The VFIFE-J-integral method is based on vector form intrinsic finite element (VFIFE) and J-integral methods to calculate the stress intensity factors at the crack tips, and the VFIFE-FCM method combines VFIFE and fictitious crack models (FCM). When the stress state at the crack tip meets the fracture criterion, the mass particle at the crack tip is separated into two particles. The crack then extends in the plate until the plate splits into two parts. The proposed VFIFE-J-integral method was validated by elastic crack simulation of a notched plate, and the VFIFE-FCM method by cohesive crack propagation of a three point bending beam. As assembly of the global stiffness matrix is avoided and each mass particle motion is calculated independently, the proposed method is easy and efficient. Numerical comparisons demonstrate that the present results predicted by the VFIFE method are in agreement with previous analytical, numerical and experimental works.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

scholarly journals Modeling of Hydraulic Fracture of Concrete Gravity Dams by Stress-Seepage-Damage Coupling Model

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Sha Sha ◽  
Guoxin Zhang
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Hydraulic Fracture ◽  
Carrying Capacity ◽  
Damage Model ◽  
Coupling Model ◽  
Propagation Path ◽  
Concrete Dams ◽  
Gravity Dams ◽  
Concrete Gravity Dams

High-pressure hydraulic fracture (HF) is an important part of the safety assessment of high concrete dams. A stress-seepage-damage coupling model based on the finite element method is presented and first applied in HF in concrete dams. The coupling model has the following characteristics: (1) the strain softening behavior of fracture process zone in concrete is considered; (2) the mesh-dependent hardening technique is adopted so that the fracture energy dissipation is not affected by the finite element mesh size; (3) four coupling processes during hydraulic fracture are considered. By the damage model, the crack propagation processes of a 1 : 40 scaled model dam and Koyna dam are simulated. The results are in agreement with experimental and other numerical results, indicating that the damage model can effectively predict the carrying capacity and the crack trajectory of concrete gravity dams. Subsequently, the crack propagation processes of Koyna dam using three notches of different initial lengths are simulated by the damage model and the coupling model. And the influence of HF on the crack propagation path and carrying capacity is studied. The results reveal that HF has a significant influence on the global response of the dam.

Analytical Prediction Model for Fatigue Crack Propagation Rate under Tension-Compression Loading

2013 ◽  
Vol 842 ◽  
pp. 455-461
Author(s):  
Yu Sha ◽  
Shi Gang Bai ◽  
Ya Hui Wang
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Plastic Zone ◽  
Crack Propagation ◽  
Compressive Stress ◽  
Fatigue Crack Propagation ◽  
Crack Tip ◽  
Plastic Zone Size ◽  
Zone Size ◽  
Compression Loading

Elastic–plastic finite element analyses have been performed to study the compressive stress effect on fatigue crack growth under applied tension–compression loading. The near crack tip stress, crack tip opening displacement and crack tip plastic zone size were obtained for a kinematic hardening material. The results have shown that the near crack tip local stress, displacement and reverse plastic zone size are controlled by the maximum stress intensity factors Kmax and the applied compressive stress σmaxcom under tension–compression. Based on the finite element analysis results, a fatigue crack propagation model using Kmax and σmaxcom as a parameters under tension–compression loading has been developed.The models under tension–compression loading agreed well with experimental observations.

scholarly journals Analysis of Crack Propagation Path on the Anisotropic Bi-Material Rock

2010 ◽  
Vol 2010 ◽  
pp. 1-22
Author(s):  
Chao-Shi Chen ◽  
Chia-Huei Tu ◽  
Chen-Cheng Yang
Keyword(s):  
Integral Equation ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Domain Boundary ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Boundary Integral ◽  
Propagation Path ◽  
Disk Specimen ◽  
Fortran Code

This paper presents a single-domain boundary element method (SDBEM) for linear elastic fracture mechanics analysis in the 2D anisotropic bimaterial. In this formulation, the displacement integral equation is collocated on the uncracked boundary only, and the traction integral equation is collocated on one side of the crack surface only. The complete fundamental solution (Green's function) for anisotropic bi-materials was also derived and implemented into the boundary integral formulation so the discretization along the interface can be avoided except for the interfacial crack part. A special crack-tip element was introduced to capture exactly the crack-tip behavior. A computer program with the FORTRAN code has been developed to effectively calculate the stress intensity factors, crack initiation angle, and propagation path of an anisotropic bi-material. This SDBEM program has been verified having a good accuracy with the previous researches. In addition, a rock of type (1)/(2) disk specimen with a central crack was made to conduct the Brazilian test under diametrical loading. The result shows that the numerical analysis can predict relatively well the direction of crack initiation and the path of crack propagation.

Effect of centrifugal load on crack path in thin-rimmed and webbed gears

2015 ◽  
Author(s):  
F. Curà ◽  
A. Mura ◽  
C. Rosso
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Root Zone ◽  
Crack Nucleation ◽  
Numerical Models ◽  
Propagation Path ◽  
Initiation Point ◽  
Centrifugal Load ◽  
Bending Load ◽  
Uncertainty Zone

Thin rimmed and webbed gears are used in particular applications to reduce systems weight. This kind of gears need an accurate and fail safe design. As a matter of fact, a possible failure, due to bending fatigue, consists in crack nucleation and consequent growth, in particular in the tooth root zone. These cracks may propagate through the tooth or through the rim. Crack propagation direction is basically influenced by the wheel geometry parameters, above all the rim thickness. Studies available in literature emphasize three ranges for the backup ratio values, involving different behaviors. These ranges are related to the crack propagation paths; respectively through the tooth, through the rim and in an unforeseeable way. This last uncertainty zone depends on other parameters, related to both geometry and loading conditions. In this work the effect of wheel speed related to the bending load has been investigated. The investigation has been carried out by means of numerical models involving both 2D finite element and extended finite element models (XFEM). Results shows that both crack initiation point and crack propagation path are strongly influenced by centrifugal load; this effect is mainly evident in the uncertainty zone of the backup ratio.

Surface Cracking in Elastic-Plastic Multi-Layered Media Due to Repeated Sliding Contact

2004 ◽  
Vol 126 (4) ◽  
pp. 655-663 ◽  
Author(s):  
Z.-Q. Gong ◽  
K. Komvopoulos
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Layered Media ◽  
Growth Increment ◽  
Propagation Direction ◽  
Sliding Contact ◽  
Propagation Path ◽  
Surface Cracking ◽  
Crack Propagation Direction

Surface cracking in a multi-layered medium due to sliding of a rigid asperity was analyzed using linear elastic fracture mechanics and the finite element method. Overlapping of the crack faces and assumptions about the distributions of surface tractions were avoided by using special contact elements. The main objectives of this study were to obtain solutions for the tensile and shear stress intensity factor (SIF) and to determine the crack propagation path in the first layer due to repetitive sliding. The crack propagation direction was predicted based on the maximum (tensile or shear) SIF range. The effects of the crack length, sliding friction, and crack-face friction on the SIF and crack propagation direction are discussed in the context of finite element solutions. Simulation results demonstrate the effects of crack growth in the elastic surface layer on the accumulation of plastic strain in the elastic-plastic underlying layer and the significance of the crack growth increment on the propagation path. It is shown that the surface crack propagates toward the layer interface at an angle of ∼57° from the original crack plane, independent of the crack growth increment, in fair agreement with experimental observations. Based on the obtained results, a general fatigue approach for surface cracking is derived for multi-layered media subjected to repetitive sliding contact.

The Role of Residual Stresses in Particulate Composite with Glass Matrix

2015 ◽  
Vol 665 ◽  
pp. 173-176 ◽  
Author(s):  
Zdeněk Majer ◽  
Luboš Náhlík ◽  
Pavel Hutař
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Glass Matrix ◽  
Particulate Composite ◽  
Element Model ◽  
Propagation Path ◽  
Particulate Composites ◽  
Stress Criterion ◽  
Finite Element Software

The particulate composites with glass matrix are widely used in many engineering applications. The mismatch of coefficients of thermal expansion during the fabrication process usually causes the presence of the residual stresses around particles. The influence and the understanding of the effects of residual stresses on the material response is required. The main aim of the present paper was to create a two-dimensional finite element model to analyze the influence of residual stresses on micro-crack behavior of glass and ceramics-based particulate composites. The maximum tangential stress criterion (MTS) was used to predict the direction of the micro-crack propagation. The modelled material was a kind of Low Temperature Co-fired Ceramics (LTCC) containing alumina particles embedded in a glass matrix. The influence of the micro-crack length and magnitude of loading on the micro-crack propagation path were investigated. The finite element software ANSYS was used. Conclusions of this paper can contribute to a better understanding of the propagation of micro-cracks in particulate composites in the field of residual stresses.

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