• Tribology and Lubricants
• /
• v.36 no.6
• /
• pp.365-370
• /
• 2020

Recently, additive manufacturing (AM) technology has been applied to various industries such as automotive, aviation, medical, and electronics. Most prior studies are limited to the mechanical properties of printed materials, and few studies are being conducted on their tribological characteristics. However, the friction and wear characteristics of the material should be studied in order to utilize the components manufactured using AM technology as mechanical parts. In this study, the friction and wear characteristics of acrylonitrile-butadiene-styrene (ABS)-like resin printed with stereo lithography apparatus (SLA) 3D printing are evaluated according to the viscosity of silicon oil lubricant using a ball-on-disk experiment. Lubricants with a viscosity of 500, 1000, and 2000 cSt are prepared for the experiment. If silicon oil lubricants are used during the ball-on-disk test, the coefficient of friction (COF) and wear rates are significantly reduced, and the higher the viscosity of the lubricant, the lower will be the COF and wear rates. It is also verified that the temperature of the specimen owing to friction also decreases according to the viscosity of the lubricant. This is because of the silicon oil film thickness, and the higher the viscosity of the lubricant, the thicker will be the oil film. More studies on the tribological characteristics of 3D printing materials and suitable lubricants will be required to use 3D printed parts as mechanical elements.

• Ocean Systems Engineering
• /
• v.12 no.2
• /
• pp.225-245
• /
• 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.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.47 no.2
• /
• pp.311-322
• /
• 2023

In this study, the properties of various material combinations were evaluated and an ideal material for fabricating protection pads for women's army combat uniforms was determined. Eight specimens were used for the evaluation: two types of materials, namely thermoplastic polyurethane for 3D printing, T and ethylene-vinyl acetate, E; two infill densities, namely 10%, 10 and 30%, 30; two types of pad designs, i.e., without holes, A and with holes, B; 2×2×2=8 and control E. The tensile strength, flexural strength, impact absorption, and weight of these specimens were evaluated. Results revealed that E was the most flexible material; however, its tensile strength and impact absorption were very low. Protection pads made from T (T-10A, T-10B, T-30A, and T-30B) had excellent tensile strength and impact absorption; however, they had low performance in ease of movement. Alternatively, protection pad with holes and an infill density of 30% produced using a combination of T and E had a high initial tensile modulus and exhibited excellent impact absorption. Moreover, it was flexible and light, which satisfies the standards and conditions required by protection pads. However, if T-E-10A and T-E-30B exhibited low impact absorption, as required, they can be regarded as appropriate materials for protection pads.

• Journal of Sensor Science and Technology
• /
• v.28 no.6
• /
• pp.407-413
• /
• 2019

Using 3D printing technology, we created a biomimetic water strider robot that can monitor environments. We found ways to increase the bearing capacity of the fluid-driven water strider robot by conducting experiments then comparing with more stable robots. The controller of the robot is based on Arduino, and can be controlled wirelessly with a Bluetooth module. The speed of the robot is 7.37 cm/s, and the bearing capacity is 29 g. A lithium polymer battery that can be charged with a solar cell was used as a power source, and both the charging and driving times were also explored.

• Proceedings of the Korea Contents Association Conference
• /
• 2017.05a
• /
• pp.135-136
• /
• 2017

2016년부터 전면 실시된 자유학기제에서 미래 사회를 선도하는 새로운 기술을 접해보는 것은 미래를 살아가는 학생들에게 매우 중요한 부분이 될 것이다. 최근 4차 산업혁명의 일환으로 각광을 받고 있는 3D 프린팅을 다른 기술과 융합하여 학생 중심의 수업을 위한 프로그램을 개발하였다. 개발한 초안에 대하여 전문가 5인의 내용 검토를 통하여 최종 완성되었다. 발된 융합 커리큘럼은 자유학기제의 교과 및 자유학기 활동에서 활용될 수 있는 체험 활동을 중심으로 한 교육과정으로 개발되었으며 향후 자유학기 뿐 아니라 연계 자유학기, 일반학기 및 동아리 활동, 방과 후 활동 등에도 적용될 수 있을 것으로 기대된다.

• Journal of the Korean Ceramic Society
• /
• v.54 no.6
• /
• pp.470-477
• /
• 2017

Ceramic processing to fabricate 3D complex ceramic structures is crucial for structural, energy, environmental, and biomedical applications. A unique process is ceramic stereolithography, which builds ceramic green objects from CAD files from many thin liquid layers of powder in monomer, which are solidified by polymerization with a UV laser, thereby "writing" the design for each slice. This approach directly writes layers in liquid ceramic suspension and allows one to fabricate ceramic parts and products having more accurate, complex geometries and smooth surfaces. In this paper, both UV curable materials and processes are presented. We focus on the basic material principles associated with free radical polymerization and rheological behavior, cure depth and broadening of cured lines, scattering at ceramic interface and their corresponding simulation. The immediate potentials for ceramic AM to change industry fabrication are also highlighted.

• Korean Journal of Computational Design and Engineering
• /
• v.22 no.2
• /
• pp.190-201
• /
• 2017

This paper proposes how to solve a problem of FDM 3D printer's irregular output when changing volume of extrusion, adjusting movement speed of the printer's head and a way to fill new inner part. Existing slicers adjust directly to change the rotation speed of the stepper. In this method, the change of the extrusion area is delayed due to the gap between the stepper and the nozzle, so that precise control is difficult. We control the extrusion area adjusting the moving speed of the print head and making constantly the rotation speed of the stepper. Thus, the output time can be shortened by generating an efficient path having a short travel distance. For evaluation, we applied our method to lithophanes with detailed variation. Comparing existing methods, our method reduced output time at least 30%.

• Journal of Dental Anesthesia and Pain Medicine
• /
• v.20 no.5
• /
• pp.325-329
• /
• 2020

Classic anesthetic techniques for the inferior alveolar nerve, lingual nerve, and long buccal nerve blockade are achieved by estimating the intended location for anesthetic deposition based on palpation, inspection, and subsequent correlation for oral anatomical structures. The present article utilizes computed tomography (CT) data to 3D print a guide for repeatable and accurate deposition of a local anesthetic at the ideal location. This technical report aims to anatomically define the ideal location for local anesthetic deposition. This process has the potential to reduce patient discomfort, risk of nerve damage, and failed mandibular anesthesia, as well as to reduce the total anesthetic dose. Lastly, as robotic-based interventions improve, this provides the initial framework for robot-guided regional anesthesia administration in the oral cavity.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2020.07a
• /
• pp.405-407
• /
• 2020

본 연구에서는 시각장애 학습자를 위한 새로운 형태의 인터랙티브 웹 AR 시스템을 제안했다. 궁중 기록화를 3D 프린팅 과정을 거쳐 시각장애가 있는 학습자들이 활용할 수 있도록 웹 AR를 접목하여 저시력 학습자에게는 시각적 효과를 더해 미디어 기기를 활용한 학습방법을 개선하고자 하였고, 전맹 학습자에게는 회화의 선묘를 살려 프린팅하여 구성을 자세히 알아볼 수 있도록 제안했다.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.11a
• /
• pp.168-169
• /
• 2021

A hydrophobic surface increases the contact angle between water and cement paste. There are two methods to increase water contact angle, i.e. lowering the surface energy and adjusting the surface roughness of concrete. The hydrophobicity of concrete can be quantitatively evaluated according to the chemical and physical properties of the solid surface. So far, researches have shown the chemical properties of hydrophobic concrete, however it has not covered how to control surface. This study demonstrated the hydrophobic cement paste prepared by low-resolution molds printed with a 3D printer that exhibit rough surface. Thus, we presented the most hydrophobic characteristics of mold.