• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.191-192
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• 2006

In these days, various kinds of rapid prototyping processes are available, such as stereo-lithography apparatus(SLA), fused deposition modeling(FDM), selective laser sintering(SLS), 3 dimensional printing(3DP), and laminated object manufacturing(LOM). For detailed informations about mechanical properties of those parts, benchmark tests are carried out. SLS and EOS part has an advantage in compressive strength, SLA has in hardness, FDM part has in impact strength, and LOM part has an advantage in tensile strength and heat resistance. The change of building direction in layered manufacturing processes of FDM and LOM severely weakens the tensile and impact strength.

• Journal of Welding and Joining
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• 제34권4호
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• pp.9-16
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• 2016

Metal parts are produced by conventional methods such as casting, forging and cutting, extrusion, etc. However, nowadays, with additive manufacturing (AM), it is possible to directly commercialize by means of stacking of equipment to the 3D drawing and use of high precision tools such as laser source. Thus, drawing of materials is an important aspect in delivering good products. AM deals with production of lighter aircraft parts and few more three-dimensional molds, it wish to manufacture special medical parts and want to steadily expand the new market area. The cost of related equipment and materials are still expensive and difficult to obtain on a mass production. However, the ability to make changes and lead the innovation in the paradigm of traditional manufacturing process is still effective. In this paper, we introduce metal AM and the principles of the related devices, metal powder production process, and their application.

• Smart Structures and Systems
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• 제29권6호
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• pp.767-775
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• 2022

Metal additive manufacturing (AM), also known as metal three-dimensional (3D) printing, produces 3D metal products by repeatedly adding and solidifying metal materials layer by layer. During the metal AM process, products experience repeated local melting and cooling using a laser or electron beam, resulting in product defects, such as warpage, cracks, and internal pores. Such defects adversely affect the final product. This paper proposes the in situ monitoring-based warpage prediction of metal AM products with experimental feature extraction. The temperature profile of the metal AM substrate during the process was experimentally collected. Time-domain features were extracted from the temperature profile, and their relationships to the warpage mechanism were investigated. The standard deviation showed a significant linear correlation with warpage. The findings from this study are expected to contribute to optimizing process parameters for metal AM warpage reduction.

• 한국분말재료학회지
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• 제29권4호
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• pp.303-308
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• 2022

The plastic deformation behavior of additively manufactured anisotropic structures are analyzed using the finite element method (FEM). Hill's quadratic anisotropic yield function is used, and a modified return-mapping method based on dual potential is presented. The plane stress biaxial loading condition is considered to investigate the number of iterations required for the convergence of the Newton-Raphson method during plastic deformation analysis. In this study, incompressible plastic deformation is considered, and the associated flow rule is assumed. The modified return-mapping method is implemented using the ABAQUS UMAT subroutine and effective in reducing the number of iterations in the Newton-Raphson method. The anisotropic tensile behavior is computed using the 3-dimensional FEM for two tensile specimens manufactured along orthogonal additive directions.

• 대한치과보철학회지
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• 제57권4호
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• pp.483-489
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• 2019

디지털치의학의 발달과 함께 computer-aided design and computer-aided manufacturing (CAD/CAM)을 이용한 3D 제작산업이 최근 급격한 성장을 하고 있다. 디지털 방식을 이용한 의치 제작 또한 최근의 디지털치의학 기술의 발전으로 증가하는 추세에 있다. CAD/CAM 제작방법은 크게 두가지 타입으로 나눌 수 있다: 절삭가공, 적층가공, 밀링과 같은 절삭가공은 블록 형태의 재료를 깎아 제조하는 기술을 토대로 하며, 3D printing과 같은 적층가공은 재료를 적층 방식으로 쌓아 올려 제조하는 기술을 토대로 한다. 적층가공은 밀링이 어려운 복잡한 구조의 제작에 적용할 수 있다. 본 증례에서, 적층가공방법이 레진상 총의치 제작에 이용되었다. 디지털방식을 적용한 의치의 사용기간동안 기능적, 심미적으로 만족할 만한 결과를 보여주었다.

• 한국콘텐츠학회논문지
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• 제20권8호
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• pp.162-175
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• 2020

본 연구는 비주얼 커뮤니케이션의 맥락에서 타이포그래피-특히 3차원 환경의 타이포그래피-와 글말의 기호성(記號性)을 시공간의 차원에서 융합하는 실천적 탐구를 다룬다. 지금까지의 타이포그래피 연구와 교육은 주로 지면(紙面)과 같은 2차원 환경과 인쇄 기술을 중심으로 이루어져 왔다. 그러나 본 연구는 지면을 벗어난 타이포그래피에 관한 프로젝트를 연구자가 직접 설계하고 수행한 결과로써 비주얼 커뮤니케이션에 쓰이는 사유와 표현의 수준을 한 차원 높이고 그 범위를 확장하는 기회를 제공한다. 프로젝트의 효율적인 진행을 위해 먼저 커뮤니케이션의 구조와 체계, 프로세스를 파악하고 비주얼 커뮤니케이션의 중추로서 2차원과 3차원 타이포그래피에 대해 고찰한다. 더불어 대표적인 3차원 타이포그래피 작품을 맥락적으로 분석하여 본 연구를 위해 진행한 프로젝트의 개념적 뼈대로 삼는다. 또한 이를 바탕으로 3차원 타이포그래피 프로젝트 연작 <수사적 공간>을 창작하여 그 가능성을 실제적이고 객관적으로 검증하고 제안한다. 나아가 문자 기반의 시각 언어와 비주얼 커뮤니케이션 디자인의 발전을 목표로 하는 아이디어의 시각화를 보다 공간적, 물리적, 그리고 입체적인 공적 환경의 영역에서 발현할 수 있는 기회로 삼고자 한다.

• Korean Journal of Radiology
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• 제22권5호
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• pp.706-713
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• 2021

Objective: To evaluate the impact of surgical simulation training using a three-dimensional (3D)-printed model of tetralogy of Fallot (TOF) on surgical skill development. Materials and Methods: A life-size congenital heart disease model was printed using a Stratasys Object500 Connex2 printer from preoperative electrocardiography-gated CT scans of a 6-month-old patient with TOF with complex pulmonary stenosis. Eleven cardiothoracic surgeons independently evaluated the suitability of four 3D-printed models using composite Tango 27, 40, 50, and 60 in terms of palpation, resistance, extensibility, gap, cut-through ability, and reusability of. Among these, Tango 27 was selected as the final model. Six attendees (two junior cardiothoracic surgery residents, two senior residents, and two clinical fellows) independently performed simulation surgeries three times each. Surgical proficiency was evaluated by an experienced cardiothoracic surgeon on a 1-10 scale for each of the 10 surgical procedures. The times required for each surgical procedure were also measured. Results: In the simulation surgeries, six surgeons required a median of 34.4 (range 32.5-43.5) and 21.4 (17.9-192.7) minutes to apply the ventricular septal defect (VSD) and right ventricular outflow tract (RVOT) patches, respectively, on their first simulation surgery. These times had significantly reduced to 17.3 (16.2-29.5) and 13.6 (10.3-30.0) minutes, respectively, in the third simulation surgery (p = 0.03 and p = 0.01, respectively). The decreases in the median patch appliance time among the six surgeons were 16.2 (range 13.6-17.7) and 8.0 (1.8-170.3) minutes for the VSD and RVOT patches, respectively. Summing the scores for the 10 procedures showed that the attendees scored an average of 28.58 ± 7.89 points on the first simulation surgery and improved their average score to 67.33 ± 15.10 on the third simulation surgery (p = 0.008). Conclusion: Inexperienced cardiothoracic surgeons improved their performance in terms of surgical proficiency and operation time during the experience of three simulation surgeries using a 3D-printed TOF model using Tango 27 composite.

• Ocean Systems Engineering
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• 제12권2호
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• pp.225-245
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• 2022

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

• 대한치과기공학회지
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• 제43권4호
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• pp.153-159
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• 2021

Purpose: The purpose of this study was to assess the fitness of anterior and posterior interim crowns fabricated by three different additive manufacturing technologies. Methods: The working model was digitized, and single crowns (maxillary right central incisor and maxillary right first molar) were designed using computer-aided design software (DentalCad 2.2; exocad). On each abutment, interim crowns (n=60) were fabricated using three types of additive manufacturing technologies. Then, the abutment appearance and internal scan data of the interim crown was obtained using an intraoral scanner. The fitness of the interim crowns were evaluated by using the superimposition of the three-dimensional scan data (Geomagic Control X; 3D Systems). The one-way analysis of variance and Tukey posterior test were used to compare the results among groups (α=0.05). Results: A significant difference was found in the fitness of the interim crowns according to the type of additive manufacturing technology (p<0.05). The posterior interim crown showed smaller root mean square value than the anterior interim crown. Conclusion: Since the fitness of the posterior interim crown produced by three types of additive manufacturing technology were all within clinically acceptable range (<120 ㎛), it can be sufficiently used for the fabrication of interim crowns.

• The Journal of Advanced Prosthodontics
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• 제13권3호
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• pp.144-151
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• 2021

PURPOSE. The purpose of this in vitro study was to investigate the wear resistance and surface roughness of three interim resin materials, which were subjected to chewing simulation. MATERIALS AND METHODS. Three interim resin materials were evaluated: (1) three-dimensional (3D) printed (digital light processing type), (2) computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and (3) conventional polymethyl methacrylate interim resin materials. A total of 48 substrate specimens were prepared. The specimens were divided into two subgroups and subjected to 30,000 or 60,000 cycles of chewing simulation (n = 8). The wear volume loss and surface roughness of the materials were compared. Statistical analysis was performed using one-way analysis of variance and Tukey's post-hoc test (α=.05). RESULTS. The mean ± standard deviation values of wear volume loss (in mm³) against the metal abrader after 60,000 cycles were 0.10 ± 0.01 for the 3D printed resin, 0.21 ± 0.02 for the milled resin, and 0.44 ± 0.01 for the conventional resin. Statistically significant differences among volume losses were found in the order of 3D printed, milled, and conventional interim materials (P<.001). After 60,000 cycles of simulated chewing, the mean surface roughness (Ra; ㎛) values for 3D printed, milled, and conventional materials were 0.59 ± 0.06, 1.27 ± 0.49, and 1.64 ± 0.44, respectively. A significant difference was found in the Ra value between 3D printed and conventional materials (P=.01). CONCLUSION. The interim restorative materials for additive and subtractive manufacturing digital technologies exhibited less wear volume loss than the conventional interim resin. The 3D printed interim restorative material showed a smoother surface than the conventional interim material after simulated chewing.