• Clinics in Shoulder and Elbow
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• 제23권1호
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• pp.27-30
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• 2020

Osborne-Cotterill lesion is an osteochondral fracture located in the posterolateral margin of the humeral capitellum, which may be associated with a defect of the radial head after an elbow dislocation. This lesion causes instability by affecting the lateral ulnar collateral ligament over its capitellar insertion, which is associated with a residual capsular laxity, thereby leading to poor coverage of the radial head, and hence resulting in frequent dislocations. We present a 54-year-old patient, a physician who underwent trauma of the left elbow after falling from a bike and suffered a posterior dislocation fracture of the elbow. The patient subsequently presented episodes of instability, and additional work-up studies diagnosed the occurrence of Osborne-Cotterill lesion. An open reduction and internal fixation of the bony lesion was performed, with reinsertion of the lateral ligamentous complex. Three months after surgery, the patient was asymptomatic, having a flexion of 130° and extension of 0°, and resumed his daily activities without any limitation. Currently, the patient remains asymptomatic 2 years after the procedure. Elbow instability includes a large spectrum of pathological conditions that affect the biomechanics of the joint. The Osborne-Cotterill lesion is one among these conditions. It is a pathology that is often forgotten and easily overlooked. Undoubtedly, this lesion requires surgical intervention.

• 한국기계가공학회지
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• 제19권4호
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• pp.1-8
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• 2020

Mechanical components that support structures in aerospace and power generation industries require high-strength materials. Particularly, in the aerospace industry, aluminum alloys, titanium alloys, and composite materials are increasingly used due to their high maneuverability and durability to withstand low temperature extreme environments; however, ultra-high-strength steel is still used in key components under heavy loads such as landing gears. In this paper, the fault cause analysis and troubleshooting of aircraft parts made of ultra-high-strength steel (300M) broken during normal operation are described. To identify the cause of the defect, a temporary inspection of the same aircraft was performed, and material testing, non-destructive inspection, microstructure examination, and fracture area inspection of the damaged parts were performed. Fracture analysis results showed that a crack in the shape of a branch developed from the tool mark in the direction of the intergranular strain. Based on the results, the cause of fracture was confirmed to be stress corrosion.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.1-6
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• 2000

FFP(Fitness For Purpose) type defect assessment methodologies based on ECA(Engineering Critical Analysis) have been established and are in use for the structural integrity evaluation of gas pipelines. ECA usually includes the fracture mechanics analysis, and it assumes that J-integral uniquely characterizes crack-tip stress-strain fields. However, it has been shown that it is not sufficient to characterize the crack-tip field under low levels of constraint with a single parameter. Since pipeline structures are made of ductile material, locally loaded in tension, cracks may experience low level of constraint, and therefore, J-dominance will be lost. For this reason, the level of constraint must be quantified to establish a precise assessment procedure for pipeline defects. The objective of this paper is to Investigate the fracture behavior of a crack in gas pipeline by quantifying the level of constraint. For this purpose, tensile tests and CTOD tests were performed at room temperature$(24^{\circ}C)$ and low temperature$(-40^{\circ}C)$ to obtain the material properties. J-Q analyses were performed for SENB and SENT specimens based on 2-D finite element analyses, in order to investigate the in-plane constraint effects on pipeline defects.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.17-25
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• 2001

This paper briefly describes the new engineering method, called the enhanced reference stress method, to estimate J (or $C^*$) for non-linear fracture mechanics analysis of defective components, recently proposed by authors. The proposed method offers significant advantages over existing methods in terms of its accuracy, simplicity and robustness. Examples of application of the proposed method to typical piping integrity problems such as through-wall cracked pipes under combined loading, and surface cracked pipes under internal pressure and bending are given. Excellent agreements between the FE J and $C^*$ results and those of the proposed method provide sufficient confidence in the use of the proposed method. One notable point is that the proposed method can be used to estimate J (or $C^*$) along the crack front of surface cracks. Moreover simplicity of the proposed method makes it easy to extend to more complex problems. Thus the proposed method is attractive to assess the significance of defects under practical situations.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1025-1032
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• 2010

Gas turbine compressor blades used in a combined cycle power plant are possibly damaged and fractured during their operation. There are two possible causes of the failure of compressor blades; one is a defect of material quality which can be detected through some microscopic inspections for the fracture section, the other is high cycle fatigue problem caused by vibration and can be diagnosed by carrying out dynamic characteristics analysis for the blades. In this paper, in order to determine the cause of the failure of compressor blades in a combined cycle power plant, examination of the fracture section and the propagation mechanism of the crack via stress analysis are performed. Dynamic characteristics analysis via FRF estimation is also performed to identify the cause of failure.

• 대한기계학회논문집
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• 제17권6호
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• pp.1441-1455
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• 1993

본 연구에서는 최신기법에 의해서 제조된 HIP제 질화규소와 지르코니아를 실험재료로 하여 무윤활하에서의 미끄럼마찰·마멸실험을 수행하여 마찰·마멸특성을 규명하고, SEM을 이용한 마멸면의 미시적 관찰을 통해서 세라믹의 마멸기구를 조사하 여 세라믹마멸기구의 마멸모델을 제시하고자 한다. 제시된 마멸모델에서 파괴역학을 도입하여 이론해석과 고찰을 수행하여 보다 실용적인 세라믹의 마멸율울 평가할 수 있 는 새로운 무차원 파라메터를 제안하고자 한다.

• 한국정밀공학회지
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• 제16권3호통권96호
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• pp.145-153
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• 1999

This study has been performed to investigate the stress distribution around defects that behave as stress concentrators and fracture mechanical analysis for cracks initiatiating at stress concentrators. The stress distribution was analyzed using Finite Element Method and non dimensional stress intensity factor was determined by the mean stress method. In addition, stress interaction effects around defects and cracks were compared.

• Restorative Dentistry and Endodontics
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• 제41권4호
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• pp.316-321
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• 2016

Although it is challenging, the early diagnosis of a vertical root fracture (VRF) is crucial in order to ensure tooth preservation. The purpose of this clinical case report was to describe reparative surgery performed to treat a tooth affected by an incomplete VRF. A 26 year old male patient was suspected to have a VRF in a maxillary left central incisor, and an exploratory flap was performed in order to confirm the diagnosis. After detecting the fracture, the lesion was surgically treated, the fracture and the infected root-end were removed, and a platelet-rich plasma membrane was used to cover the defect in order to prevent bacterial migration. A 24 month clinical and radiological follow-up examination showed that the tooth was asymptomatic and that the healing process was in progress. The surgical approach described here may be considered an effective treatment for a combined endodontic-periodontal lesion originating from an incomplete VRF and a recurrent periapical lesion.

• 한국기계가공학회지
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• 제21권3호
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• pp.12-21
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• 2022

Directed energy deposition (DED) was adopted as a metal additive manufacturing method to develop a mold for the hot stamping process. The test piece was machined from Heatvar laminate material, and results were obtained through microstructure and defect observations, as well as hardness, tensile strength, and joint strength tests. 1) Spherical pores and irregular-shaped cavities were observed as lamination defects, and columnar dendrites formed in the structure, which tended to become coarse upon heat treatment. 2) The hardness of the heat-treated material (480HV) was slightly lower than that of the non-heat-treated material (500HV). 3) In the tensile test, the maximum tensile stress and strain of the heat-treated material were 1392 MPa and 15%, respectively, which were slightly higher than the values of 1381 MPa and 13%, respectively, for the non-heat-treated material. 4) In the case of the early final fracture in the tensile test, in most cases, pores or irregularly shaped cavities were observed at the fracture surface or near the surface. 5) In the joint strength test, most of the specimens finally fractured in the laminated metal area, and the fracture surface was intragranular. In addition, dimples formed over the entire area on the fracture surface of the fractured specimen after sufficient elongation.

• Archives of Plastic Surgery
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• 제38권2호
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• pp.199-202
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• 2011

Purpose: Hyoid bone is a U-shaped bone in the anterior of the neck. Hyoid bone fractures are exceedingly rare and represent only 0.002% of all fractures because of its protective position relative to the mandible and its suspension by elastic musculature. We report a patient who presented hyoid bone fracture associated with hypoglossal nerve palsy. We also discuss the possible complication and treatment. Methods: A 69-year-old man was transferred from another institution because of persistent purulent discharge from the left chin. He had a history of trauma in which a knuckle crane grabbed his face and neck in the construction site. A CT scan at the time of the accident demonstrated a comminuted fracture of the right side of the mandible and hyoid bone fracture at the junction between body and right greater cornua. The displaced fracture of hyoid bone and fullness in the pre-epiglottic space were noted, probably indicating some edema. The patient was transferred into ICU after treatment of emergency tracheostomy because the patient showed respiratory distress rapidly. When the patient was hospitalized in our emergency room, he complained of dysphagia and pain when swallowing. On examination of oral cavity, the presence of muscle wasting with fasciculation of the tongue was noted and the tongue deviates to the left side on protruding from the mouth. Pharyngolarygoscopy was performed to make sure that there was no evidence of progressive swelling and pharyngeal laceration. Results: The patient underwent surgical removal of dead and infected tissue from the wound and reconstruction of mandibular bony defect by iliac bone grafting. Hyoid bone fracture was managed conservatively with oral analgesics, soft diet and restricted movement. Hypoglossal nerve palsy was resolved within 7 weeks after trauma without complications. Conclusion: Closed hyoid bone fracture is usually uncomplicated and thus it can be treated conservatively. Surgical intervention for hyoid bone fracture is recommended for patient with airway compromise, pharyngeal perforation and painful symptoms which show no response to conservative care. Furthermore, since respiratory distress syndrome may develop quickly, close observation is required. Besides, hypoglossal nerve palsy is a rarely recognized complication of hyoid bone fracture.