• Structural Engineering and Mechanics
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• v.74 no.2
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• pp.283-296
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• 2020

The coupled hydro-mechanical loading conditions commonly occur in the geothermal and petroleum engineering projects, which is significantly important influence on the stability of rock masses. In this article, the influence of flaw inclination angle of fracture behaviors in rock-like materials subjected to both mechanical loads and internal hydraulic pressures is experimentally studied using the 3-D X-ray computed tomography combined with 3-D reconstruction techniques. Triaxial compression experiments under confining pressure of 8.0 MPa are first conducted for intact rock-like specimens using a rock mechanics testing system. Four pre-flawed rock-like specimens containing a single open flaw with different inclination angle under the coupled hydro-mechanical loading conditions are carried out. Then, the broken pre-flawed rock-like specimens are analyzed using a 3-D X-ray computed tomography (CT) scanning system. Subsequently, the internal damage behaviors of failed pre-flawed rock-like specimens are evaluated by the 3-D reconstruction techniques, according to the horizontal and vertical cross-sectional CT images. The present experimental does not only focus on the mechanical responses, but also pays attentions to the internal fracture characteristics of rock-like materials under the coupled hydro-mechanical loading conditions. The conclusion remarks are significant for predicting the rock instability in geothermal and unconventional petroleum engineering.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.279-285
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• 2012

In this paper a computational method for a homogenized peridynamics description of unidirectional fiber-reinforced composites is presented. For these materials, dynamic brittle fracture and damage are simulated with the proposed peridynamic model. Compared with observations from dynamic experiments by Coker et al.(2001), the peridynamic computational model can reproduce various characteristics of dynamic fracture and supersonic or intersonic crack growth in asymmetrically loaded unidirectional fiber-reinforced composite plates. Also we analyze the same model in the symmetric loading condition and figure out that the asymmetric loading leads to a much higher propagation speed. Consistent results have been reported in the experiments.

• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.31-41
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• 2019

Structural integrity assessment of piping components is of paramount important for remaining life prediction, residual strength evaluation and for in-service inspection planning. For accurate prediction of these, a reliable fracture parameter is essential. One of the fracture parameters is stress intensity factor (SIF), which is generally preferred for high strength materials, can be evaluated by using linear elastic fracture mechanics principles. To employ available analytical and numerical procedures for fracture analysis of piping components, it takes considerable amount of time and effort. In view of this, an alternative approach to analytical and finite element analysis, a model based on relevance vector machine (RVM) is developed to predict SIF of part through crack of a piping component under fatigue loading. RVM is based on probabilistic approach and regression and it is established based on Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Model for SIF prediction is developed by using MATLAB software wherein 70% of the data has been used for the development of RVM model and rest of the data is used for validation. The predicted SIF is found to be in good agreement with the corresponding analytical solution, and can be used for damage tolerant analysis of structural components.

• Journal of Veterinary Clinics
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• v.36 no.1
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• pp.82-84
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• 2019

A common kestrel (Falco tinnunculus) was presented with inability to stand and fly at Chungnam Wild Animal Rescue Center. The kestrel showed non-weight bearing ambulation on both legs and crepitation with no external wound. Radiographs revealed a fracture on mid-diaphysis of right tibiotarsus and a distal end fracture of left femur. Intramedullary pinning was chosen for reduction of both fractures. The right tibiotarsal fracture was corrected first, and left femur was repaired 5 days later. The kestrel was managed with a specially designed sling to prevent further iatrogenic damage for 2 weeks. Three weeks after the surgery, the kestrel was able to stand and found to perch in 4 weeks. On 5 weeks, The kestrel could fly free at outdoor aviary and was released through rehabilitation for 3 months finally.

• Journal of the Korean Orthopaedic Association
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• v.55 no.6
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• pp.457-471
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• 2020

Fingers are body parts with a complex structure and essential functions that are the most prone to trauma. The principle of treatment for finger fractures is to determine the balance between obtaining stable fracture fixation and early joint movement. Despite proper treatment, there are many cases of functional and cosmetic problems caused by stiffness or deformation as complications. This review article introduces the latest knowledge in the treatment of finger fractures focusing on fractures and dislocations around the interphalangeal joints, including joint surface damage, which is difficult to treat and leads to poor results. This article consists of fracture cases and describes the methods and solutions to address these complications.

• Computers and Concrete
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• v.11 no.2
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• pp.123-148
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• 2013

The nonlinear finite element method with eight noded isoparametric quadrilateral element for concrete and two noded element for reinforcement is used for the prediction of the behavior of reinforcement concrete structures. The disturbed state concept (DSC) including the hierarchical single surface (HISS) plasticity model with associated flow rule with modifications is used to characterize the constitutive behavior of concrete both in compression and in tension which is named DSC/HISS-CT. The HISS model is applied to shows the plastic behavior of concrete, and DSC for microcracking, fracture and softening simulations of concrete. It should be noted that the DSC expresses the behavior of a material element as a mixture of two interacting components and can include both softening and stiffening, while the classical damage approach assumes that cracks (damage) induced in a material treated acts as a void, with no strength. The DSC/HISS-CT is a unified model with different mechanism, which expresses the observed behavior in terms of interacting behavior of components; thus the mechanism in the DSC is much different than that of the damage model, which is based on physical cracks which has no strength and interaction with the undamaged part. This is the first time the DSC/HISS-CT model, with the capacity to account for both compression and tension yields, is applied for concrete materials. The DSC model allows also for the characterization of non-associative behavior through the use of disturbance. Elastic perfectly plastic behavior is assumed for modeling of steel reinforcement. The DSC model is validated at two levels: (1) specimen and (2) practical boundary value problem. For the specimen level, the predictions are obtained by the integration of the incremental constitutive relations. The FE procedure with DSC/HISS-CT model is used to obtain predictions for practical boundary value problems. Based on the comparisons between DSC/HISS-CT predictions, test data and ANSYS software predictions, it is found that the model provides highly satisfactory predictions. The model allows computation of microcracking during deformation leading to the fracture and failure; in the model, the critical disturbance, Dc, identifies fracture and failure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.309-316
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• 2010

This paper proposed a nonlocal anisotropic damage model to simulate the behavior of plain and reinforced concrete structures that are predominantly tensile and compressive load. This model based on continuum damage mechanics, used a symmetric second-order tensor as the damage variable. For quasi-brittle materials, such as concrete, the damage patterns were different in tension and in compression. These two damage states were modeled by damage evolution laws ensuring a damage tensor rate proportional to the total strain tensor in terms of principal components. To investigate the effectiveness of proposed model, the double edge notched specimen experimented by nooru-mohamed and reinforced concrete bending beam were analyzed using the implementation of the proposed model. As the results for the simulation, the nonlocal anisotropic damage model with an adequate control of rupture correctly represented the crack propagation for mixed mode fracture. In the structural failure of reinforced concrete bending beam, the proposed model can be showed up to a very high damage level and yielding of the reinforcements.

• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.476-484
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• 2002

The aim of this study is to investigate the ductile fracture behavior under mixed mode (I/II) loading using SA533B pressure vessel steel. Anti-symmetric 4-point (AS4P) bending tests were performed to obtain the J-R curves under two different mixed mode (I/II) loadings. In addition, finite element analysis using Rousselier Ductile Damage Theory was carried out to predict the J-R curves under mixed mode (I/II) loadings. In conclusions, the J-R curves under. Mixed Mode (I/II) loading were located between those of Mode I and Mode II loading. When the mixity of mixed mode (I/II) loading was high, the J-R curve of mixed mode (I/II) loading approached that of pure mode I loading after some amount of crack propagation. In contrast with the above fact, if the mixity was low, the J-R curve took after that of pure mode II loading. Finally, it was found that the predicted J-R curves made a good agreement with the test data through the tuning procedures of $\beta$ values at the different mixed mode (I/II) loading.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.289-295
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• 2001

The aim of this study is to investigate the ductile fracture behaviour under pure Mode II loading using A533B pressure vessel steel. Single punch shear(SPS) test was performed to obtain the J-R curve under pure Mode II loading which was compared with that of the Model I loading. Simulation using Rousellier Ductile Damage Theory(RDDT) was carried out with 4-node quadrilateral element(L(sub)c=0.25mm). For the crack advance, the failed element removal technique was adopted with a $\beta$ criterion. Through the $\beta$ value tuning-up procedures, $\beta$(sub)crit(sup)II was determined as 1.5 in contrast with $\beta$(sub)crit(sup)I=5.5. In conclusion, it was found that the J-R curve under Mode II loading was located at lower part than that under Mode I loading obtained from the previous study and that the $\beta$ values strongly depended on the loading type. In addition, the predicted result using RDDT showed a good agreement with the SPS experimental one under pure Mode II loading.

• Transactions of Materials Processing
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• v.21 no.5
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• pp.285-290
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• 2012

In spite of progress in predicting ductile failure, the development of a macroscopic yield criterion to describe damage evolution in HCP (hexagonal close-packed) materials remains a challenge. HCP materials display strength differential effects (i.e., different behavior in tension versus compression) in their plastic response due to twinning. Cazacu and Stewart(2009) developed an analytical yield criterion for porous material containing randomly distributed spherical voids in an isotropic, incompressible matrix that shows tension-compression asymmetry. The goal of the calculations in this paper is to investigate the effect of the tension-compression asymmetry on necking induced by void nucleation, evolution and consolidation. In order to investigate the effect of the tension-compression asymmetry of the matrix on necking and fracture initiation, three isotropic materials A, B, and C were examined with different ratios of tension-compression asymmetry. The various types of material had BCC, FCC, and HCP crystal structures, respectively. The ratio between tension and compression in plastic flow significantly influences the fracture shape produced by damage propagation as well as affecting the localized neck.