• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.830-838
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• 2000

The paper addresses an application of molecular dynamics technique for fracture mechanics. Molecular dynamics simulation is an atomistic approach, while typical numerical methods such as finite element methods are macroscopic. Using the potential functions, which express the energy of a molecular system, a virtual specimen with molecules is set up and the trajectory of every molecule can be calculated by Newton's equation of motion. Several three-dimensional models with various types of cracks are considered. The stress intensity factors, the sizes of plastic zone as well as the dislocation emission are sought to be compared with the analytical solutions, which result in good agreement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.2
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• pp.101-109
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• 1981

균일 인장하중하에 있는 고체 내부에 고립된 제 1형 탄소성 크랙의 반취성 파괴를 경사슬립밴드모델(inclined slip band model)로서 연속크랙전위(conticuum crack dislocation) 및 연속격자 전위(continum lattice dislocation)을 이용하여 이론적으로 연구하였다. 크랙전위 및 격자전위에 관한 힘평형을 나타애는 연립특이적분방정식의 해는크랙전위 및 격자전위에 관한 적정밀도함수를 가지고 특이함을 해소하는 조건을 부가하여 얻는다. 이특이항 해소조건의 타당성은 처음으로 소성영역의 크기를 그 판단기준으로 검토되었으며, 그결과 합당한 것으로 확인되었다. 또한 상기방법으로부터 산출된 COD는 소규모 성역을 넘어서도 선형적으로 .KAPPA.$^{2}$.EPSILON..sigma.$_{Y}$ 에 따라 변화함을 알게 된다. 상기모델에서 위축적분경로(Shrunk path) 상의 J 적분치를 J=.delta..sigma.$_{Y/}$sin2.theta.의 형태로 유도하였는데, 이것은 J 적분에 관한 Eshelby의 힘개념을 구체적으로 표현한다: J는 크랙전파방향으로 탄소성크랙정점에 작용하는 가상적인 힘이며, 1/2 J의 한 슬립편면상에서의 분력은 그 슬립정면사으이 보든 격자전위에 작용하는 전단력의 총화와 같다. 같다.

• Clinics in Shoulder and Elbow
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• v.26 no.2
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• pp.205-207
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• 2023

A Monteggia fracture is a proximal ulnar fracture with proximal radioulnar ligamentous instability. While there is no precise definition, Monteggia-equivalent fractures are generally considered Monteggia fractures accompanied by radial head fractures. These are rare. In this study, we report a rare variation of a Bado type IV Monteggia-equivalent lesion (fracture of proximal ulnar shaft, proximal radial shaft, and radial head) and its management.

• Journal of Korean Neurosurgical Society
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• v.41 no.5
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• pp.295-300
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• 2007

Objective : Unilateral facet dislocation of the cervical spine occurs by flexion and rotation injuries and cannot be easily reduced by axial traction. We analyzed 14 consecutive patients with unilateral facet dislocation of the cervical spine to increase knowledge about anatomical reduction of locked facet and factors for successful reduction. Methods : Fourteen patients [10 men and 4 women] with unilateral facet dislocation of the cervical spine were retrospectively analyzed. Plain X-ray, computerized tomography scan, and magnetic resonance imaging were performed. All patients underwent manual reduction and surgery with anterior interbody fusion and plate fixation. The manual reduction was performed by neck flexion and rotation to the opposite side of dislocation, followed by rotation and flexion of the head toward the side of dislocation and extension with relaxation of traction. Mean follow-up period was 17 months. The level of spine, amount of subluxation, combined facet fracture, and time from injury to initial reduction were analyzed using the data obtained from medical records. Results : Thirteen [93%] patients were reduced successfully. Immediate reduction was achieved in 7 patients but failed in 7 patients. Seven patients underwent delayed closed reduction under general anesthesia, and successful reduction was achieved in 6 patients. Only one patient with bone chips between articular facets failed to achieve anatomical reduction. Conclusion : In order to reduce the locked facet more easily and safely, we recommend manipulative traction with anterior interbody fusion and plate fixation under general anesthesia after being aware of spinal cord injury with magnetic resonance imaging.

• Structural Engineering and Mechanics
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• v.67 no.3
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• pp.277-281
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• 2018

The analytical solution of two functionally graded layers with Volterra type screw dislocation is investigated under anti-plane shear impact loading. The energy dissipation of FGM layers is modeled by viscous damping and the properties of the materials are assumed to change exponentially along the thickness of the layers. In this study, the rate of gradual change ofshear moduli, mass density and damping constant are assumed to be same. At first, the stress fields in the interface of the FGM layers are derived by using a single dislocation. Then, by determining a distributed dislocation density on the crack surface and by using the Fourier and Laplace integral transforms, the problem are reduce to a system ofsingular integral equations with simple Cauchy kernel. The dynamic stress intensity factors are determined by numerical Laplace inversion and the distributed dislocation technique. Finally, various examples are provided to investigate the effects of the geometrical parameters, material properties, viscous damping and cracks configuration on the dynamic fracture behavior of the interacting cracks.

• Nuclear Engineering and Technology
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• v.38 no.7
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• pp.619-638
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• 2006

Low temperature irradiation can significantly harden metallic materials and often lead to strain localization and ductility loss in deformation. This paper provides a review on the radiation effects on the deformation of metallic materials, focusing on microscopic and macroscopic strain localization phenomena. The types of microscopic strain localization often observed in irradiated materials are dislocation channeling and deformation twinning, in which dislocation glides are evenly distributed and well confined in the narrow bands, usually a fraction of a micron wide. Dislocation channeling is a common strain localization mechanism observed virtually in all irradiated metallic materials with ductility, while deformation twinning is an alternative localization mechanism occurring only in low stacking fault energy(SFE) materials. In some high stacking fault energy materials where cross slip is easy, curved and widening channels can be formed depending on dose and stress state. Irradiation also prompts macroscopic strain localization (or plastic instability). It is shown that the plastic instability stress and true fracture stress are nearly independent of irradiation dose if there is no radiation-induced phase change or embrittlement. A newly proposed plastic Instability criterion is that the metals after irradiation show necking at yield when the yield stress exceeds the dose-independent plastic instability stress. There is no evident relationship between the microscopic and macroscopic strain localizations; which is explained by the long-range back-stress hardening. It is proposed that the microscopic strain localization is a generalized phenomenon occurring at high stress.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.590-599
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• 1994

A work on the brittle to ductile transition (BDT) in single crystal alumina has been performed to understand and assess the dynamics of dislocation mobility around crack tip of brittle material. The critical stress intensity factor and yield strengths were obtained from bending test using precracked specimens at elevated temperatures. It was found that the BDT temperature was dependent on strain rate and orientation of specimen : for (1120) fracture surface, $1034^{\circ}C$, $1150^{\circ}C$ for $4.2 \times 10^{-6}$, $4.2 \times 10^{-7}s^{-1}$ respectively. Under a 4 point bending test, the moving distance of dislocation generated near crack front in ductile range is determined by an etch pits method. The velocity of dislocation in sapphire obtained from the double etching method was applied to modelling study.

• Clinics in Shoulder and Elbow
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• v.6 no.2
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• pp.149-160
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• 2003

Purpose: to determine the results after open intramedullary nailing and tension band suture technique in proximal humerus fracture for improving the stability and decreasing the complications. Materials and Method: Authors reviewed 27 patients treated by open intramedullary nailing and tension band suture technique. Mean follow-up period was 39 months (24-59months). Surgical neck fracture were 6 cases, surgical neck fracture with shaft fracture were 3 cases, three part fracture with greater tuberosity fracture were 17 cases, four part fracture was 1 case and fracture and dislocation were 2 cases Results: We got the bony union in 26 cases. Average pain scale was 1 point (0-6), Neer score was 86 point(45-99) and ASES score was 85 point(40-100). We separate all cases in two groups based on age (65 years), L-spine t-score (-2.5) and Neer classification (2 and 3 part). There is no significance in pain scale, Neer score and ASES score between each group. Conclusion: As a method of surgical treatment on severe proximal humeral fractures, we recommend intramedullary nailing and tension band suture technique and it may have particular advantages in early exercise and satisfactory functional outcome.

• Clinics in Shoulder and Elbow
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• v.1 no.2
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• pp.154-159
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• 1998

Medial dislocation of the long head of the biceps brachii is a rare condition that usually occurs in association with tears of the subscapularis, chronic impingement, capsular defects or a fracture of the lesser tuberosity. Less commonly, a biceps tendon dislocation may occur after an acute traumatic event. Following a dislocation, the biceps tendon will assume either an intra- or extra-articular position depending on whether or not the subscapularis tendon detaches from its humeral insertion. Magnetic resonance imaging has been found to provide valuable information concerning the location of the biceps tendon and the integrity of the subscapularis tendon. We present a patient with a traumatic dislocation of the biceps brachii tendon in which the diagnosis remained elusive for an extended period of time. In this case, he was evaluated using MRI and reconstruction was performed by restoring the tendon to its anatomical position.

• Clinics in Shoulder and Elbow
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• v.14 no.1
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• pp.20-26
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• 2011

Purpose: The purpose of this study is to investigate the accompanying lesions of humerus greater tuberosity fracture with anterior shoulder dislocation and to analyze its clinical results. Materials and Methods: From May 2005 to November 2008, arthroscopy was performed on a total of 30 selected patients who were diagnosed with humerus greater tuberosity fracture with anterior shoulder dislocation and who were also under the age of 40. The preoperative and postoperative Constant and Rowe scores were compared. Results: There was a total of 21 cases of anteroinferior labral lesions: 2 Bankart lesions, 4 bony Bankart lesions, 4 Perthes lesions, 2 free ALPSA lesions, 3 GLAD lesions and 6 capsular tears. For other lesions, 5 rotator cuff partial tears, 3 SLAP lesions and 1 biceps tendon rupture were found. The constant scores were increased from 56.3 to 94.43 points (p=0.034), and the Rowe scores were increased from 52.56 to 91.76 points (p=0.026). Conclusion: For humerus greater tuberosity fracture with anterior shoulder dislocation, the accompanying lesion was identified and the fracture was treated using arthroscopy. Good clinical results and bone union were achieved. According to the secondary arthroscopic findings, all of the Perthes lesion, the free ALPSA lesion, the GLAD lesion and the capsular tear spontaneously healed or they did not progress to extended rupture although arthroscopic suture was not performed. Any postoperative secondary instability was not observed.