• 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.

• 한국방사선학회논문지
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• 제16권7호
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• pp.825-833
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• 2022

3D 프린팅 기술은 재료공학의 발전과 더불어 출력할 수 있는 재질이 늘어가고 있으며 방사선 분야에 이용될 수 있는 재료들 또한 증가하고 있는 추세이다. 그렇기에 사용되는 재료들의 성분과 밀도에 따라 적용되는 분야가 달라지고 응용이 될 수 있기에 재료들의 성분과 특성 또한 고려해야 한다. 본 연구는 FDM(Fused Deposition Modeling) 방식의 3D 프린터를 이용하여 각 성질이 다른 필라멘트를 10개를 선정하고 진단용 X선 발생장치를 이용하여 신호강도를 측정하고 CT를 통하여 CT number를 측정하여 뼈와 유사한 물질을 찾고자 하였다. 그 결과 뼈와 유사한 신호강도와 CT number가 측정된 Silicon carbide라는 물질을 발견하였고. 추후 연구를 통해 인체의 뼈와 유사한 밀도를 가진 다양한 연구에 기초자료로 제시될 것으로 사료된다.

• Geomechanics and Engineering
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• 제33권1호
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• pp.11-18
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• 2023

This study explores a new energy partitioning approach to determine the fracture toughness of 3-D printed pristine/recycled high density polyethylene (HDPE) blends employing the essential work of fracture (EWF) concept. The traditional EWF approach conducts a uniaxial tensile test with double-edge notched tensile (DENT) specimens and measures the total energy defined by the area under a load-displacement curve until failure. The approach assumes that the entire total energy contributes to the fracture process only. This assumption is generally true for extruded polymers that fracture occurs in a material body. In contrast to the traditional extrusion manufacturing process, the current 3-D printing technique employs fused deposition modeling (FDM) that produces layer-by-layer structured specimens. This type of specimen tends to include separation energy even after the complete failure of specimens when the fracture test is conducted. The separation is not relevant to the fracture process, and the raw experimental data are likely to possess random variation or noise during fracture testing. Therefore, the current EWF approach may not be suitable for the fracture characterization of 3-D printed specimens. This paper proposed a new energy partitioning approach to exclude the irrelevant energy of the specimens caused by their intrinsic structural issues. The approach determined the energy partitioning location based on experimental data and observations. Results prove that the new approach provided more consistent results with a higher coefficient of correlation.

• 한국기계가공학회지
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• 제18권3호
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• pp.66-73
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• 2019

Recently, FDM-type 3D printer technology has been developed, and efforts have been made to improve the output formability and characteristics further. Through this, 3D printers are used in various fields, and printer technologies are suggested according to usage, such as FDM, SLA, DLP, and SLM. In particular, the FDM method is the most widely used, and the FDM method technology is being developed further. The characteristics of the output are produced by the FDM-type 3D printer, which is determined by various factors, and particularly the perspective of the Inter-Layer Fill Factor, which is the volume ratio of the laminated material that exerts a direct influence. In this study, the Inter-Layer Fill Factor is theoretically obtained by presenting the internal space between each layer according to the laminate thickness as a cross-sectional shape model, and the cross section of the actual laminated sample is compared with the theoretical model through experiments. Then, the equation for the theoretical model is defined, and the strength change according to each condition (tensile strength of material, reduction slope, strength reduction rate, and output strength) is confirmed. In addition, we investigated the influence on the correlation and strength between laminate thickness and the Inter-Layer Fill Factor.

• 한국방사선학회논문지
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• 제15권5호
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• pp.697-704
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• 2021

3D 프린팅 FDM방식의 재료인 필라멘트 중 차폐성능을 지닌 필라멘트는 국내에 판매되지 않고 있으며 관련 연구도 미비하다. 이에 본 연구는 금속 입자가 함유된 필라멘트의 물성과 방사선의 차폐능력을 평가하여 3D 프린트를 이용한 방사선 차폐체 개발의 기초자료를 제공하고자 한다. 금속입자 강화재가 함유된 금속 필라멘트 5가지를 선정 후 ASTM의 평가방법을 이용하여 인장강도, 밀도, XRD, 무게측정 등 물성을 평가하고 방사선 차폐능력을 알아보기 위하여 한국산업표준의 방호용구류 시험방법에 따라서 방사선 차폐율을 구하였다. 인장강도는 PLA + SS가 가장 높았고 ABS + W가 가장 낮았으며 밀도는 ABS + W 가 3.13 g/cm3으로 가장 높게 나타났다. XRD결과 시편의 표면의 입자의 XRD peak 패턴이 각 입자 강화재 분말 금속의 패턴과 일치함을 확인 할 수 있어 프린트된 시편이 분말금속이 함유 되었음을 확인하였다. 3D 프린트 복합 필라멘트별 차폐효과는 ABS + W, ABS + Bi, PLA + SS, PLA + Cu, PLA + Al의 순서로 실효원자번호와 밀도에 비례하여 차폐율이 높게 나타났다. 본 연구에서는 강화재로 금속 분말이 함유된 금속입자 복합 필라멘트는 방사선의 차폐능력을 가지는 것이 확인되었으며 향후 방사선 차폐용 필라멘트의 사용가능성을 확인하였다.

• 한국전자통신학회논문지
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• 제15권2호
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• pp.313-318
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• 2020

300도 이상의 높은 용융점을 갖는 소위 엔지니어링 플라스틱은 기구적인 강성과 내화학성 및 마찰 및 마모성능이 우수하여 여러 산업에서 금속을 대체하는 소재로 각광받고 있다. 본 연구에서는 용융적층모델링 공법을 기반으로 하는 3D 프린터에서 높은 용융점을 갖는 엔지니어링 플라스틱을 조형할 수 있도록 방열특성이 우수한 3D 프린터 nozzle부의 구조를 설계하고 이를 해석적으로 검증하였다. 높은 온도로 가열되는 heat block과 필라멘트가 이송되는 nozzle상부 간의 단열 및 신속한 냉각을 위하여, 열전도계수가 낮은 열차단부(heat brake부)를 2중으로 구성하였고, 열차단부에 생성되는 열이 냉각핀을 통해 대기에 의해 냉각되는 구조를 적용하였다. 개선된 nozzle부 구조설계를 통해 종래 3D 프린터의 BCnozzle과 비교할 때, heat sink부에서의 온도를 50% 가량 낮출 수 있었으며, heat block에 직접적으로 연결된 heat brake부 최종단의 정상상태 온도를 14% 가량 낮출 수 있었다.

• 한국의류학회지
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• 제45권1호
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• pp.155-167
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• 2021

The latest innovation in the field of fashion comes in the form of 3D-printed clothing. This study explores the composition and characteristics of the shapes in the architecture of Zaha Hadid, a representative architectural designer who expresses space in three dimensions. Hadid applies his aesthetic to fashion design using these distinctive geometric shapes to create design motifs as well as develop new clothing material with 3D printing technology. The research was conducted as follows. First, the lines and arrangement of the geometric shapes in Zaha Hadid's architecture were analyzed so that his design principles could be used as a theoretical basis for this study. The study also reviewed geometric fashion designs using 3D printing technology over the last ten years. Second, we developed triangular modules with rods and tongs that could be fashioned into clothing using fused deposition modeling (FDM) 3D printers. Lastly, the 3D printing fashion design was developed to explore new silhouettes, textures, and a novel way of producing clothing. This study hopes to serve as a stepping-stone for further research on innovations that combine fashion with technology.

• Advances in aircraft and spacecraft science
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• 제9권4호
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• pp.301-318
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• 2022

This paper presents the free vibration analysis of 3D printed sandwich beams by using high-order theories based on the Carrera Unified Formulation (CUF). In particular, the component-wise (CW) approach is adopted to achieve a high fidelity model of the printed part. The present model has been used to build an accurate database for collecting first natural frequency of the beams, then predicting Young's modulus based on an inverse problem formulation. The database is built from a set of randomly generated material properties of various values of modulus of elasticity. The inverse problem then allows finding the elastic modulus of the input parameters starting from the information on the required set of the output achieved experimentally. The natural frequencies evaluated during the experimental test acquired using a Digital Image Correlation method have been compared with the results obtained by the means of CUF-CW model. The results obtained from the free-vibration analysis of the FDM beams, performed by higher-order one-dimensional models contained in CUF, are compared with ABAQUS results both first five natural frequency and degree of freedoms. The results have shown that the proposed 1D approach can provide 3D accuracy, in terms of free vibration analysis of FDM printed sandwich beams with a significant reduction in the computational costs.

• 산업식품공학
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• 제21권3호
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• pp.233-241
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• 2017

Scaffolds of cell substrates are biophysical platforms for cell attachment, proliferation, and differentiation. They ultimately play a leading-edge role in the regeneration of tissues. Recent studies have shown the potential of bioactive scaffolds (i.e., osteo-inductive) through 3D printing. In this study, rice bran-derived biocomposite was fabricated for fused deposition modeling (FDM)-based 3D printing as a potential bone-graft analogue. Rice bran by-product was blended with poly caprolactone (PCL), a synthetic commercial biodegradable polymer. An extruder with extrusion process molding was adopted to manufacture the newly blended "green material." Processing conditions affected the performance of these blends. Bio-filament composite was characterized using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Mechanical characterization of bio-filament composite was carried out to determine stress-strain and compressive strength. Biological behaviors of bio-filament composites were also investigated by assessing cell cytotoxicity and water contact angle. EDX results of bio-filament composites indicated the presence of organic compounds. These bio-filament composites were found to have higher tensile strength than conventional PCL filament. They exhibited positive response in cytotoxicity. Biological analysis revealed better compatibility of r-PCL with rice bran. Such rice bran blended bio-filament composite was found to have higher elongation and strength compared to control PCL.

• 한국기계가공학회지
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• 제19권1호
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• pp.81-88
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• 2020

In this paper, the performances of the electrical characteristics of the Fused Deposition Modeling (FDM) 3D-printed flexible resistance sensor was evaluated. The FDM 3D printing flexible resistive sensor is composed of flexible-material thermoplastic polyurethane and a conductive PLA (carbon black conductive polylactic acid) polymer. While 3D printing, polymer filaments heat up quickly before being extruded and cooled down quickly. Polymers have poor thermal conductivity so the heating and cooling causes unevenness, which then results in internal stress on the printed parts due to the rapidity of the heating and cooling. Electrical resistance measurements show that the 3D-printed flexible sensor is unstable due to internal stress, so the 3D-printed flexible sensor resistance curve does not match the increases and decreases in the displacement curve. Therefore, annealing was performed to eliminate the mismatch between electrical resistance and displacement. Annealing eliminates residual stress on the sensor, so the electrical resistance of the sensor increases and decreases in proportion to displacement. Additionally, the resistance is lowered in comparison to before annealing. The results of this study will be very useful for the fabrication of various devices that employ 3D-printed flexible sensor that have multiple degrees of freedom and are not limited by size and shape.