• Geomechanics and Engineering
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• v.9 no.5
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• pp.645-667
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• 2015

Single treatment and staged treatments in vertical wells are widely applied in sandstone and mudstone thin interbedded (SMTI) reservoir to stimulate the reservoir. The keys and difficulties of stimulating this category of formations are to avoid hydraulic fracture propagating through the interface between shale and sand as well as control the fracture height. In this paper, the cohesive zone method was utilized to build the 3-dimensional fracture dynamic propagation model in shale and sand interbedded formation based on the cohesive damage element. Staged treatments and single treatment were simulated by single fracture propagation model and double fractures propagation model respectively. Study on the changes of fracture vicinity stress field during propagation is to compare and analyze the parameters which influence the interfacial induced stresses between two different fracturing methods. As a result, we can prejudge how difficult it is that the fracture propagates along its height direction. The induced stress increases as the pumping rate increasing and it changes as a parabolic function of the fluid viscosity. The optimized pump rate is $4.8m^3/min$ and fluid viscosity is $0.1Pa{\cdot}s$ to avoid the over extending of hydraulic fracture in height direction. The simulation outcomes were applied in the field to optimize the treatment parameters and the staged treatments was suggested to get a better production than single treatment.

• Journal of Korean Orthopaedic Sports Medicine
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• v.9 no.2
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• pp.114-120
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• 2010

Anterior tibial diaphyseal stress fracture have a propensity for delayed union or nonunion and have risk of complete fracture after minor trauma. So, careful evaluation and optimal management are mandatory to succeed in treatment. It is also important to decide the point of time of return to full activity. We report experience of treatment for complete fracture of the delayed union of anterior tibial diaphyseal stress fracture as an athletic injury.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.1
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• pp.41-51
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• 2004

FRP re-bar in concrete structures could be used as a substitute of steel re-bars for that cases in which aggressive environment produce high steel corrosion, or lightweight is an important design factor, or transportation cost increase significantly with the weight of the materials. But FRP fibers have only linearly elastic stress-strain behavior; whereas, steel re-bar has linear elastic behavior up to the yield point followed by large plastic deformation and strain hardening. Thus, the current FRP re-bars are not suitable concrete reinforcement where a large amount of plastic deformation prior to collapse is required. The main objectives of this study in to evaluate the tensile behavior and the fracture mode of hybrid FRP re-bar. Fracture mode of hybrid FRP re-bar is unique. The only feature common to the failure of the hybrid FRP re-bars and the composite is the random fiber fracture and multilevel fracture of sleeve fibers, and the resin laceration behavior in both the sleeve and the core areas. Also, the result of the tensile and interlaminar shear stress test results of hybrid FRP re-bar can provide its excellent tensile strength-strain and interlaminar stress-strain behavior.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2109-2115
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• 2001

Miniaturized specimen technology is useful to characterize the mechanical behavior when it is difficult to sample the material enough for the test. In this study, two kinds of miniaturized Charpy impact specimens(i.e., miniaturized specimen with side groove and without side groove) of aged 1Cr- lMo-0.25V steel were prepared and tested. The relationship between the extent of degradation in terms of ductile brittle transition temperature(DBTT) and the fracture stress of 1Cr-1Mo-0.25V steel was established. The fracture stress obtained from miniaturized specimen without side groove turned out to be linearly related with the DBTT of standard specimen. Therefore the fracture toughness of aged turbine rotor steel might be evaluated by the fracture stress. In addition, the correlation between DBTT of standard specimen and that of miniaturized specimen was investigated. As the results of normalizing DBTT by maximum elastic tensile stress, the normalized DBTT of miniaturized specimen without side groove allows one to estimate that of standard specimen.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2090-2095
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• 1997

The plane stress fracture toughness for thin aluminum alloy(2024-T3 and 7075-T6) specimens are characterized by using compact-tension (CT) specimens. Anti-buckling plates were fabricated on both sides of the thin CT specimens to prevent the buckling phenomena which caused by the 45.deg. C plastic yielding at the crack tip under the plane stress condition. The plane stress fracture toughnesses determined by three different procedures are compared with each others. The plane stress fracture toughnesses are also compared with a few published values which were determined by using center-cracked panel specimens.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.6 no.2
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• pp.79-85
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• 2011

Objectives : The Purpose of this study is to investigate the clinical application of conservative treatment for femoral neck stress fracture developed in avascular necrosis of the femoral head. Methods : Patient is hospitalized at Dept. of Oriental Rehabilitation Medicine, Bu-Chun Jaseng Oriental Medicine Hospital, diagnosed as femoral neck stress fracture developed in avascular necrosis of the femoral head and treated by herbal medicine, acupuncture and moxibustion. This study was measured by Visual Analogue Scale(VAS) score, range of motion and walking time. Results : After conservative treatment, the patient's pain was controlled and VAS score was decreased. Range of motion and walking time were improved. Conclusions : As seen in this one case, Oriental conservative treatment has a positive effect to control pain with femoral neck stress fracture developed in avascular necrosis of the femoral head.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.86-94
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• 2009

A three dimensional rock joint element was developed considering fracture mechanics and subcritical crack growth to simulate non-linear behavior and the progressive failure of rock joints. Using this 3-D joint element, joint shear tests of rock discontinuities were simulated by a numerical method. The asperities on the joint surface began to fail at stress levels lower than the rock fracture toughness and continued progressively due to subcritical crack growth. As a result of progressive failing in each and every asperity, the joint showed non-linear stress-time behavior including stress hardening/softening and the reaching of a residual stress.

• Journal of Veterinary Clinics
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• v.35 no.3
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• pp.83-87
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• 2018

The aim of this study was to evaluate the biomechanical behavior of xenogenic bone plate system (equine bone) using a three-dimensional finite element ulna fracture model. The model was used to calculate the Von Mises stress (VMS) and stress distribution in fracture healing periods with metallic bone plate and xenogenic bone plate systems, which are installed while the canine patient is standing. Bone healing rate (BHR) (0%) and maximum VMS of the xenogenic plate was similar to the yield strength of equine bone (125 MPa). VMS at the ulna and fracture zones were higher with the xenogenic bone plate than with the metallic bone plate at BHRs of 0% and 1%. Stress distributions in fracture zone were higher with the xenogenic bone plate than the metallic bone plate. This study results indicate that the xenogenic bone plate may be considered more beneficial for callus formation and bone healing than the metallic bon plate. Xeonogenic bone plate and screw applied in clinical treatment of canines may provide reduced stress shielding of fractures during healing.

• Geomechanics and Engineering
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• v.7 no.4
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• pp.403-430
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• 2014

Shale gas formations exhibit strong mechanical and strength anisotropies. Thus, it is necessary to study the effect of anisotropy on the hydraulic fracture initiation pressure. The calculation model for the in-situ stress of the bedding formation is improved according to the effective stress theory. An analytical model of the stresses around wellbore in shale gas reservoirs, in consideration of stratum dip direction, dip angle, and in-situ stress azimuth, has been built. Besides, this work established a calculation model for the stress around the perforation holes. In combination with the tensile failure criterion, a prediction model for the hydraulic fracture initiation pressure in the shale gas reservoirs is put forward. The error between the prediction result and the measured value for the shale gas reservoir in the southern Sichuan Province is only 3.5%. Specifically, effects of factors including elasticity modulus, Poisson's ratio, in-situ stress ratio, tensile strength, perforation angle (the angle between perforation direction and the maximum principal stress) of anisotropic formations on hydraulic fracture initiation pressure have been investigated. The perforation angle has the largest effect on the fracture initiation pressure, followed by the in-situ stress ratio, ratio of tensile strength to pore pressure, and the anisotropy ratio of elasticity moduli as the last. The effect of the anisotropy ratio of the Poisson's ratio on the fracture initiation pressure can be ignored. This study provides a reference for the hydraulic fracturing design in shale gas wells.

• Journal of Korean Neurosurgical Society
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• v.38 no.1
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• pp.77-79
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• 2005

We report a case of early stress fracture of the pelvic ring following an extension of a multilevel instrumented lumbosacral fusion in an osteopenic female. Surgeons should be aware of possibilities of pelvic complications in osteopenic patients with lumbosacral arthrodesis and should take care when harvesting iliac bone graft.