• 한국정밀공학회지
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• 제18권1호
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• pp.98-103
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• 2001

Machining is the commonly used process in the manufacturing of prototypes. This process offers several advantages, such as rigidity of the machine, precision of the machine, precision of the operation and specially a quick delivery. The weight and immobility of the machine support and immobilize the part during the operation. However, despite these advantages it shows, machining still presents several limitations. The immobilization, location and support of the part are referred to as fixturing or workholding and present the biggest challenge for time efficient machining. So it is important to select and design the appropriate fixturing assembly. This assembly depends on the complexity of the part and the tool paths and may require the construction of dedicated fixtures. With traditional techniques, the range of fixturable shapes is limited and the identification of suitable fixtures in a given setup involves complex reasoning. To solve this limitation and to apply the automation, this paper presents the Reference Free Part Encapsulation(RFPE) and implementation of the encapsulation system. The feature-based modeling system and the encapsulation system are implemented. The small part of which it is difficult to find out the appropriate fixturing assembly is made by this system.

• 한국해양공학회지
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• 제29권1호
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• pp.34-44
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• 2015

A hydraulic tensile test machine (HSTM) is one of the devices used to obtain the flow stress of a material during high-speed elongation. This paper first describes some features of a newly built HSTM. The improvement histories of the upper and lower jigs, which are the most vital parts of the HSTM, are also presented. We have frequently witnessed test failures with 1st generation jigs and specimens due to slip between the jig and specimen. 2nd generation jigs provide more stable test results, but the use of a longer upper jig induces excessive vibration and consequently makes it difficult to attach an environment chamber. 3rd generation jigs have some advances in terms of the symmetric fastening between the upper jig and specimen, as well as an exemption from direct contact between the lower jig and specimen. The performance of an environment chamber is verified by high and low temperature tests. A high-speed displacement measurement system is introduced based on a high-speed camera and motion-tracking software with aid of a surface grid device for the specimen.

• 한국기계가공학회지
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• 제12권5호
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• pp.50-56
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• 2013

Machine tools are the cores of industrial development in recent period. It is difficult to develop a system which can do cutting and grinding process in the one system. Hybrid Vertical Grinding System is capable of processing in a single apparatus cutting or grinding. The modal analysis and structural analysis for the development of Hybrid Vertical Grinding System is the first time of domestic work. In this study, Hybrid Vertical Grinding System bed was designed and analyzed by using SS401 and FC300 as materials. And by using Finite Element Methods, the design and material of the bed was analysed. Finally, we can make a better choice of structure and material of the bed by comparing the analysis results.

• 한국가스학회지
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• 제25권2호
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• pp.64-71
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• 2021

수소연료전지자동차를 비롯한 자동차 분야에서 성형 가공성과 기계적 특성이 우수한 고분자 복합수지에 대한 연구는 특정 기계적 특성을 갖춘 재료의 설계지원을 위한 Computer-Aided Engineering (CAE)으로 확대되고 있다. CAE 자동화는 소재의 기계적 특성 및 거동 예측이 선행되어야 하는데, 고분자 복합수지의 기계적 물성 예측은 단일물질과 달리, 바탕재와 보강재 간의 관계로만 설명하기에는 물성 거동이 복잡하기에, 수식으로 설명하기 어렵다. 본 연구에서는 큰 소성 구간과 조성에 예민하여 예측이 어려웠던 고분자 복합수지의 조성에 따른 응력-변형률 선도를 데이터의 기계학습을 기반으로 예측하였다. 개발모델은 바탕재, 보강재 종류 및 조성간의 복잡한 상관관계를 찾아, 학습한 시험 데이터가 없는 조건에서도 전체 응력-변형률 곡선을 의미있게 예측한다. 학습하지 않은 조성과 구성에 대해서도 고분자 복합수지의 기계적 특성을 예측하는 개발 모델을 기반으로 향후 소재 설계 AI 시스템을 완성할 수 있을 것으로 기대한다.

• 대한치과보철학회지
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• 제44권1호
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• pp.20-28
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• 2006

Statement of problem: The titanium has advantages of a high biocompatibility, a corrosion resistence, low density, and cheep price, so it is focused as a substituted alloy But it is quite difficult to cast with the tranditional method due to the high melting point, reacivity with element at, elevated temperature. By using the CAD-CAM system for the crown construction, it is possible to reduce the errors while proceeding the wax-up, investing, and casting procedure Purpose: The purposes of this study were to measure the marginal adaptation of the casting titanium coping and machine-milled titanium coping according to the casting methods and the marginal configurations. Material and method: The marginal configurations were used chamfer shoulder, and beveled shoulder. The total 30 copings were used, and these are divided into 6 groups according to the manufacturing method and marginal configuration. The gap between margin of the model and the restoration was measured with 3-dimensional measuring microscope. Results: The following results were obtained; 1. casting gold coping demonstrated the best marginal seal, followed by casting titanium coping finally machine-milled titanium copings. 2. In casting titanium coping, chamfer demonstrated the best marginal seal, followed by shoulder and beveled shoulder. There was no significantly difference in shoulder and beveled shoulder. But all margin form has clinically acceptable 3. In machine-milled titanium copings, chamfer demonstrated the best marginal seal, followed by shoulder and beveled shoulder. Beveled shoulder show large and uneven marginal gap Conclusions: Above result revealed that marginal adaptation of the titanim coping is avail able in the clinical range, it can be used as an alternative metal and it is prefered especially in chamfer or shoulder margin during implant superstructure fabrication. But there should be more research on machine-milled titanium in order to use it in the clinics.

• Journal of Welding and Joining
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• 제28권6호
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• pp.35-39
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• 2010

Generally, ceramic material is very difficult to machine due to high strength and hardness. However, ceramic material can be machined at high temperature by plastic flow as metallic material due to the deterioration of the grain boundary glassy phase. Recently, a new method was developed to execute cutting process with CBN cutting tool by local heating of surface with laser. There are various parameters in LAM because it is a complex process with laser treatment and machining. During laser assisted machining, high power results in reducing of cutting force and increasing tool life, but excessive power brings oxidation of the surface. The effect of laser power, feed rate, cutting depth and etc. were investigated on the life of cutting tool. Chips were observed to find out suitable machining conditions. Chips of SSN had more flow-types than HIPSN. It means SSN is easier to machining. The life of cutting tool was increased with increasing laser power and decreasing feed rate and cutting depth.

• 한국정밀공학회지
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• 제28권6호
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• pp.701-708
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• 2011

Although Titanium material has superior properties, it belongs to difficult-to-machine materials. The present research applies magnetic abrasive finishing to precision machining of internal-face of titanium pipes, and analyzed & assessed the influence of grinding conditions on magnetic abrasive effects through the removed amount and surface roughness of materials. There was the influence on grinding properties according to change of rotational speed, a total input of mixed powder and an input of grinding liquid, and when the total input, rotational speed and ratio of electrolytic iron versus magnetic abrasives are 8g and 1000rpm, it was most advantageous in aspects of surface roughness and material removal amount, and the grinding liquid remarkably improved the surface roughness and material removal amount only with addition of trace amounts of light oil rather than dry machining conditions. And a result of considering the influence on grinding properties by using an inert gas (Argon gas) for improving grinding properties of the internal-face of titanium pipe, the present research has obtained improvement effects in the removal amount and surface roughness through utilization of an inert gas.

• 한국기계가공학회지
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• 제17권4호
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• pp.76-82
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• 2018

3D formed Electrical Discharge Machining (EDM) and hole EDM were conducted for die and mold manufacturing with electrodes which were made by mechanical machining and wire EDM. It is difficult to machine the hardened material after heat treatment and quenching with traditional machining. The only method of machining hardened material is die-sinking EDM. In this research, hole EDM was conducted for heat-treated cold-worked tool steel (SKD11) for use as a die material. The EDM surfaces were analyzed by pulse-on time and peak current of EDM current, according to the machining conditions of EDM. The EDM surface profiles were affected by the peak current. The contribution of each factor is peak current (91.63%) and pulse-on time (0.93%). The best surface roughness was obtained with a $130{\mu}s$ pulse-on time and a 14.2 A peak current. With uniform EDM processing, the surface deteriorated with increasing pulse-on time and peak current. The thickness of the solidified layer induced by EDM was increased as the peak current, crater shapes, and erupted shapes of EDM surfaces were increased. Therefore, microcracking gaps induced by surface tension were increased.

• Smart Structures and Systems
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• 제29권2호
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• pp.361-374
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• 2022

As civil infrastructure has continued to age worldwide, its structural integrity has been threatened owing to material deteriorations and continual loadings from the external environment. Structural Health Monitoring (SHM) has emerged as a cost-efficient method for ensuring structural safety and durability. As SHM research has gradually addressed an increasing number of structure-related problems, it has become difficult to understand the changing research topic trends. Although previous review papers have analyzed research trends on specific SHM topics, these studies have faced challenges in providing (1) consistent insights regarding macroscopic SHM research trends, (2) empirical evidence for research topic changes in overall SHM fields, and (3) methodological validations for the insights. To overcome these challenges, this study proposes a framework tailored to capturing the trends of research topics in SHM through a bibliometric and network analysis. The framework is applied to track SHM research topics over 15 years by identifying both quantitative and relational changes in the author keywords provided from representative SHM journals. The results of this study confirm that overall SHM research has become diversified and multi-disciplinary. Especially, the rapidly growing research topics are tightly related to applying machine learning and computer vision techniques to solve SHM-related issues. In addition, the research topic network indicates that damage detection and vibration control have been both steadily and actively studied in SHM research.

• 한국주조공학회지
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• 제26권4호
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• pp.184-190
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• 2006

Presence of inclusions in Ti castings imparts detrimental effects on the mechanical performance of castings. However, actual inclusions do not occur very frequently and they are difficult to locate. As a result, acquirement of specimens for mechanical tests and thus in-depth research of the adverse influence of inclusions are challenging. To address this problem, artificial inclusion seeding methodology is developed to emulate actual inclusions in Ti investment castings. Firstly, to validate that this new methodology does not result in inherent mechanical property degradation, Ti specimens with machined, backfilled and HIPed holes are produced and compared to control (unaltered), cast Ti material. Fatigue test results indicate that this 'machine-and-HIP methodology without seeding' does not result in any fundamental mechanical property alteration, which would bias ensuing comparative results. Secondly, based on this result, validation of the artificially seeded inclusions being equivalent to 'as cast' inclusions is performed by comparing their fatigue behaviors. Test specimens created by the novel artificial inclusion seeding methodology are equivalent to Ti casting specimens containing actual cast-in inclusions, and an adverse effect of inclusions in investment castings is confirmed.