• 대한기계학회논문집A
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• 제34권7호
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• pp.911-917
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• 2010

본 연구에서는 열적-기계적 주기하중을 받고 있는 엔진 배기매니폴드에 대해서 열응력 해석방법과 열피로수명 예측과정을 제시하였다. 즉, 파손현상이 복잡한 배기시스템의 효율적인 유한요소 모델링 방법과 온도 의존성 재료의 시험결과를 이용한 해석 데이터 구성, 그리고 열사이클 하중에 대한 열응력 및 파손 예측방법을 디젤엔진의 배기매니폴드에 대해서 나타내었다. 일반적으로 배기매니폴드의 파손 취약부에서는 고온영역에서 큰 압축소성변형이 발생하고 냉각시에는 인장의 잔류응력이 나타난다. 따라서 이같은 응력과 변형률의 이력곡선으로부터 소성변형의 진폭 또는 소성에너지의 크기를 얻을 수 있으며 이를 통해서 피로수명을 예측할 수 있다.

• Archives of Reconstructive Microsurgery
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• 제20권1호
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• pp.1-7
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• 2011

The aim of extremity reconstruction has focused on early wound coverage and functional recovery but rarely aesthetics. As the quality of life improves, however, the request for aesthetics has been growing. The authors has conducted retrospective reviews on the 86 cases that had extremity reconstruction using free flap, considering the characteristics of parts that had been assessed in primary operation between May 1996 and December 2010. Aesthetic grading was performed in four categories; color, texture, contour and marginal scar. Recipient sites were 42 hands, 19 feet, 14 lower extremities excluding feet and 10 upper extremities apart from the hand. Types of free flap were 16 latissimus dorsi free flaps, 13 anterolateral thigh free flaps, 12 dorsalis pedis free flaps, 8 transvers rectus abdominis free flaps, 7 gracillis free flaps, and 5 superficial temporal fascia free flaps. Total flap necrosis was seen in 8 cases(9.3%) and partial necrosis in 5 cases(5.8%). Secondary revision was done in 24 cases(27.9%) and the most common revision, debulking was done in 14 cases(16.3%). The authors has considered cosmetic aspects along with wound coverage and functional recovery in primary reconstruction. The results of aesthetic grading was 16.2 out of 20, and the secondary revision rate was reduced.

• Archives of Plastic Surgery
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• 제39권6호
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• pp.643-648
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• 2012

Background Aggressive treatment of sternoclavicular joint (SCJ) infection involves systemic antibiotics, surgical drainage and resection if indicated. The purpose of this paper is to describe a classification of post resectional SCJ defects and highlight our reconstructive algorithm. Defects were classified into A, where closure was possible often with the aid of topical negative pressure dressing; B, where parts of the manubrium, calvicular head, and first rib were excised; and C, where both clavicular, first ribs and most of the manubrium were resected. Methods Twelve patients (age range, 42 to 72 years) over the last 8 years underwent reconstruction after SCJ infection. There was 1 case of a type A defect, 10 type B defects, and 1 type C defect. Reconstruction was performed using the pectoralis major flap in 6 cases (50%), the latissimus dorsi flap in 4 cases (33%), secondary closure in 1 case and; the latissimus and the rectus flap in 1 case. Results All wounds healed uneventfully with no flap failure. Nine patients had good shoulder motion. Three patients with extensive clavicular resection had restricted shoulder abduction and were unable to abduct their arm past $90^{\circ}$. Internal and external rotation were not affected. Conclusions We highlight our reconstructive algorithm which is summarised as follows: for an isolated type B SCJ defect we recommend the ipsilateral pectoralis major muscle for closure. For a type C bilateral defect, we suggest the latissimum dorsi flap. In cases of extensive infection where the thoracoacromial and internal mammary vessels are thrombosed, the pectoralis major and rectus abdominus cannot be used; and the latissimus dorsi flap is chosen.

• 대한두개안면성형외과학회지
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• 제18권3호
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• pp.179-185
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• 2017

Background: The use of leeches can effectively increase the salvage rate of flap congestion. However, the first reaction from patients and carers in using leeches in clinical fields is strong aversion. This can be due to the fact that development of our culture from agriculture to industrial society, coming across leeches became fairly rare. Also because of the biological traits that leeches carry; staying attached to a leg or other body parts of the host, sucking blood, and leaving wounds. Methods: This study was conducted through questionnaires, divided into many subgroups. We scaled the compliance of the two therapies, with or without leech. Maximum scale of 10 showing no rejective response to the therapy and minimum scale of 0 showing the greatest rejective response. Results: Overall subjects' compliance was improved after explaining the benefits of hirudotherapy. Irrelevant to the explanation, there was no significant difference in general compliance between male and female. Young-aged group and medical personnel or people studying medicine showed higher compliance over older-aged group and the general public. Conclusion: In the terms of general social cognition, recognizing leech as a therapeutic material may not be welcomed at first, but provided with proper information and explanations, overall compliance of patients and carers can be improved and consequently result in superior outcomes in flap salvage.

• 대한두개안면성형외과학회지
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• 제18권3호
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• pp.166-171
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• 2017

Background: Localized scleroderma is characterized by a thickening of the skin from excessive collagen deposits. It is not a fatal disease, but quality of life can be adversely affected due to changes in skin appearance, joint contractures, and, rarely, serious deformities of the face and extremities. We present six cases of localized scleroderma in face from our surgical practice. Methods: We reviewed six localized scleroderma cases that were initially treated with medication and then received follow-up surgery between April 2003 and February 2015. Six patients had facial lesions. These cases presented with linear dermal sclerosis on the forehead, oval subcutaneous and dermal depression in the cheek. Results: En coup de sabre (n=4), and oval-shaped lesion of the face (n=2) were successfully treated. Surgical methods included resection with or without Z-plasty (n=3), fat graft (n=1), dermofat graft (n=1), and adipofascial free flap (n=1). Deformities of the affected parts were surgically corrected without reoccurrence. Conclusion: We retrospectively reviewed six cases of localized scleroderma that were successfully treated with surgery. And we propose an algorithm for selecting the best surgical approach for individual localized scleroderma cases. Although our cases were limited in number and long-term follow-up will be necessary, we suggest that surgical management should be considered as an option for treating scleroderma patients.

• 한국가스학회지
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• 제12권2호
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• pp.57-62
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• 2008

배관 엘보우의 내호면(intrados)의 과 내부에 국부적으로 두께 감육이 발생한 경우, 내압과 엘보우를 닫는 방향으로의 굽힘하중을 부가하여 파손 모드를 연구하였다. 탄소성해석 시 반력-변위 곡선이 세 그룹으로 나뉘므로 각 그룹의 한 경우씩을 해석하여 소성붕괴에 의한 파손모드의 차이를 확인하였다. 이를 위해 주요 부위에서 하중-국부적응력 곡선이 어떻게 변화하는지 결정하여, 이로부터 관찰된 파손모드와 비교하여 설명하였다. 감육폭이 $90^{\circ}$인 경우 배관은 엘보우 측면부터 소성붕괴가 시작되었으며, $360^{\circ}$인 경우 내호면으로부터 소성변형이 시작되어 서로 다른 파손모드를 보여주었다. 배관의 감육측정에 의한 건전성 평가 시 이와 같은 파손 모드의 차이점을 고려하여 평가를 실시하여야 한다.

• Archives of Plastic Surgery
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• 제38권4호
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• pp.552-554
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• 2011

Purpose: Though its general usage, traditional tie-over dressing using suture has a few drawbacks such as difficulty in re-fixation after its opening especially when hematoma or seroma has occurred. It is rather difficult to maintain a stable dressing on curvy parts of body like flank, buttocks and that leads to unsatisfactory results of the surgery. Authors recommend a quick and repeatedly doable method, tie-over dressing that incorporates the usage of hooks and rubber bands. Methods: Debridement was done at a recipient site to be able to do skin graft. A right size of skin graft was prepared and placed upon the defect site with suture. Enough number of hooks were attached using Blue nylon at the normal skin of the edge of grafted area. We Applied dressing with ointment and fluffy gauze then fixed the dressing by attaching a rubber band at the hook to give a certain amount of tension. One or two days after the surgery, we opened the tie-over dressing and repeated the tie-over dressing by reusing the hooks and rubber band. Results: The skin grafts were all successfully taken and by repeating tie-over dressing using hooks and rubber, we could take the advantage of shortened the dressing time and eliminate the inconvenience of the patient and the surgeon by using bandages and fixing tapes. Conclusion: The advantage of tie over dressing using hooks and rubber bsnds are its easy re-doability early detection of probable complications, preventability of reoccurence of hematoma and seroma. Therefore, authors report this as considering the tie-over dressing using hooks and rubber bands is recommendable.

• 소성∙가공
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• 제31권6호
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• pp.365-375
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• 2022

The microstructure and high-temperature plastic deformation behavior of the modified Al-0.7Mn alloy were investigated and compared with the conventional Al-0.3Mn (Al3102) alloy. α-Al (matrix) and Al₆(Mn, Fe) phases were identified in both alloys. As a result of microstructure observation, both alloys showed equiaxed grains, and Al-0.7Mn alloy showed larger grain size and higher Al₆(Mn, Fe) fraction than Al-0.3Mn alloy. High temperature compressive tests, the deformation temperatures of 410℃, 450℃, 490℃, 530℃ and strain rats of 10^-2/s, 10^-1/s, 1/s, 10/s, were conducted using Gleeble equipment. The flow stress values of Al-0.7Mn alloy were higher than that of Al-0.3Mn alloy at all strain rates and temperature conditions. Constitutive equations were presented using the flow stresses obtained from experimental results and the Zener-Hollomon parameter. In the true stress-true strain curves of the two alloys, the experimental and predicted values were in good agreement with each other. Based on the dynamic material model, eutectic deformation maps of Al-0.7Mn and Al-0.3Mn alloys were suggested, and the plastic instability region was presented. The modified Al-0.7Mn alloy showed a wider plastic instability region than that Al-0.3Mn alloy. Based on the process deformation maps, the MPE tube parts could be manufactured through the actual extrusion process using the suggested conditions.

• Tribology and Lubricants
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• 제37권4호
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• pp.144-150
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• 2021

The most cost-effective method of reducing abrasive wear in mechanical parts is increasing their hardness with thin hard coatings. In practice, the composite hardness of the coated substrate is more important than that of the substrate or coating. After full unloading of the load applied to an indenter, its indentation hardness evaluated based on the dent created on the test piece was almost dependent on plastic deformation of the substrate. Following the first part of this study, which proposes a new Brinell hardness test method for a coated surface, the remainder of the study is focused on practical application of the method. Indentation analyses of a rigid sphere and elastic-perfect plastic materials were performed using finite element analysis software. The maximum principal stress and plastic strain distributions as well as the dent shapes according to the substrate yield stress and coating thickness were compared. The substrate yield stress had a significant effect on the dent size, which in turn determines the Brinell hardness. In particular, plastic deformation of the substrate produced dents regardless of the state of the coating layer. The hardness increase by coating behaved differently depending on the substrate yield stress, coating thickness, and indentation load. These results are expected to be useful when evaluating the composite hardness values of various coated friction surfaces.

• 대한두개안면성형외과학회지
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• 제19권4호
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• pp.254-259
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• 2018

Background: The esthetic and functional outcomes of periorbital defect reconstruction are very important because of the complex anatomy and specialized functions of this region. The orbicularis oculi myocutaneous (OOMC) flap is useful for the reconstruction of periorbital defects. But, according to the location and depth of the defects, the reconstruction using OMC flaps with various techniques is rare. The authors have used various kinds of OOMC flaps in various situations and we present an analysis of our experiences. Methods: From November 2001 to July 2017, we used 36 OOMC flaps to reconstruct 30 periorbital defects in 25 patients. We analyzed the cause of the defect, its location, the type of concomitant surgery, the method of flap movement, and complications. Results: Of the 30 defects, basal cell carcinoma was the most common cause, accounting for 20 cases. When the used OOMC flap was classified according to the location of the defects, the switch flap was used in nine cases among 15 defects of lower eyelid, and the V-Y advancement flap was mainly used for other parts. As surgical methods according to the depth of defect were classified, all cases involving the tarsal plate were reconstructed with a composite graft. In case of skin and muscles, they were reconstructed only with OOMC flap or with full-thickness skin graft. Conclusion: The OOMC flap provides good skin quality that is very similar to that of the defect tissue. Depending on the location and depth of the defect, the OOMC flap may be used properly in a variety of ways to achieve good results.