절삭률-공구수명 특성 곡선을 이용한 고속가공 공정의 최적하에 관한연구

최용철,김동우,장윤상,조명우,허영무 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-

With the recent development of machining technology, high speed machining process is widely used for the mold and difficult-to -cut-materials machining since it allows achieving high productivity and surface quality. However, during the high speed machining process, high cutting speed and feed rate can cause abrupt tool life decrease due to rapid rising of the cutting tool temperature. Such situation may cause increase of machining cost. Thus, in this study, developed optimization algorithm is applied to determine optimal machining variables for multiple high speed machining. The R-T characteristic curve for machining economics problems with a linear-lorarithmic tool life model is determined by applying sensitivity analysis. Finally, a series of high speed machining experiments are performed to determine the desired optimal machining variables, and the results are analyzed.

집속 이온빔에 의한 3차원 가공 시스템

박철우,이종항 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-

There is great difficulty in machine below 10 micrometers by conventional machining methods, such as micro-EDM. However, ultra micro machining using focused ion beam(FIB) is able to machine to 50 nanometers. Die & moulds techniques are better than one-to-one machining techniques in regards to production costs in the mass production of ultra size structures. Also, it is advantageous to machine die & moulds to the 10 micrometers level by FIB technique rather than other techniques. It is difficult to machine the three dimensional machining, such as micro lens, using FIB system because of their machining characteristics. In this paper, three dimensional machining techniques were properly introduced, and also experiments showed effectiveness of their techniques.

An Analysis Framework for Characterization of Electrical Power Data in Machining

Yulin Wang,Yan He,Yufeng Li,Ping Yan,Libin Feng 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Electrical power data of machining has become more and more vital due to the increasing concerns on the energy efficiency. As a kind of easily available real-time signal, electrical power data in machining involves diverse characteristics related to technical specification and operational production of machine tools and workpieces. To efficiently exploit the various characteristics involved in electrical power data, this paper proposes a framework to analyze characteristics of electrical power data in machining. Firstly, the sample experiment for turning the round stock on a lathe is carried out to investigate the characteristics implied in the real-time electrical power data. Based on it, a framework is derived to analyze characteristics from three aspects, energy-specific characteristic of machining, state-specific characteristic of machine tools and operation-specific characteristic of workpieces. The case with three scenarios is presented to demonstrate the potential applications of the framework, which is effectively utilized in analyzing energy consumption of machining, monitoring states of machine tools and automatically identifying the types of machining workpieces.

The finite element analysis of machining characteristics of titanium alloy in ultrasonic vibration assisted machining

Dexiong Chen,Jinguo Chen,Huasen Zhou 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8

Titanium alloy Ti6Al4V, an alpha-beta alloy, possesses many advantageous properties, such as high special strength, good resilience and resistance to high temperature and corrosion, fracture resistant characteristics and so on, being widely used in aerospace, biomedical and chemical industry. However, its machinability is still a challenge due to its low thermal conductivity, low elastic modulus and high chemical reactivity. As a novel and effective machining method, ultrasonic vibration assisted machining (UVAM) can effectively improve the machining performance of workpieces, which is widely used in the field of titanium alloy machining. A two-dimensional cutting finite element modeling methodology for orthogonal cutting titanium alloy Ti6Al4V was established to analyze the comparisons between conventional machining (CM) and ultrasonic vibration assisted machining and the effects of frequency and amplitude. The simulation results showed that (1) UVAM more easily formed serrated chip than that of CM. The chip segmentation coefficient G S which could quantitatively characterize the segmentation degree of chip showed an increasing trend with the increase of amplitude. (2) The cutting force curve of UVAM had periodic pulse fluctuation due to the effects of vibration in x-direction and y-direction. The main cutting force and the thrust force of UVAM showed the further decrease trend with the increase of frequency and x-direction amplitude. However, the y-direction amplitude made the contrary trend for the cutting force. (3) Meanwhile, with the increase of y-direction amplitude, the plastic and friction dissipation energies increased obviously. The introduction of ultrasonic vibration results in complex changes in the tool-chip contact, mechanical and temperature characteristics of the workpiece. Choosing the suitable vibration parameters will contribute to improving the machinability of titanium alloys.

Ti-6Al-4V 합금의 절삭특성과 FEM 해석 비교에 관한 연구

김남용,홍우표,이동주 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.6

The cutting characteristics of Ti-6Al-4V alloy and tool wear when machining Ti-6Al-4V alloy was studied to understand the machining characteristics. This material is one of the strong candidate materials present and future aerospace or medical applications. Nowadays their usage has already been broaden to commercial applications such as golf club head, finger rings and many decorative items. Anticipating the general use of this material and development of the titanium alloy in domestic facilities, the review and the study of the machining parameters for those alloys are deemed necessary. This study is concentrated to the machining parameters of the Ti-6A1-4V alloy due to their dominant position in the production of titanium alloys.

Thermal Characteristic Analysis of a High-Precision Centerless Grinding Machine for Machining Ferrules

Seok-Il Kim,Jae-Wan Cho 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.1

The outer diameter finishing grinding process required for ferrules, which are widely used as fiber optic connectors, is carried out by high-precision centerless grinding machines. In this study, the thermal characteristics of such a machine, for example, the temperature distribution, temperature rise, and thermal deformation, were estimated based on a virtual prototype and the heat generation rates of heat sources related to normal operating conditions. The prototype consisted of a concrete-filled bed, hydrostatic grinding wheel (GW) and regulating wheel (RW) spindle systems, a hydrostatic RW feed mechanism, a RW swivel mechanism, and on-machine GW and RW dressers. The reliability of the predicted results was demonstrated using temperature characteristics measured from a physical prototype. The predicted and measured results indicated that this particular high-precision centerless grinding machine had very stable thermal characteristics.

Laser-Assisted Milling of Turbine Blade Using Five-Axis Hybrid Machine Tool with Laser Module

Wan-Sik Woo,이춘만 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.3

Laser-assisted machining (LAM) is known to be an innovative hybrid technique to enhance the machinability of difficult-to-cut materials. LAM is a method of machining with cutting tools after the machinability is improved by laser preheating. Most studies of LAM have focused mainly on turning methods. Laser-assisted milling (LAMill) processes, including grinding and drilling, are still in the early stages of research and are limited, as the laser heat source must be able to move continuously ahead of the tool. In recent years, some research has concentrated on processing simple three-dimensional (3D) shapes using LAMill, but more innovative research must be done before this method can be commercialized. Therefore, the objective of this study is to manufacture a turbine blade using a five-axis hybrid machine tool with a laser module to make progress toward the goal of the commercialization of LAMill. The manufacturing of the turbine blade using a five-axis LAMill method is attempted for the first time in this study. A thermal analysis was conducted to determine the cutting depth for LAMill. The machining procedure was divided into roughing and finishing steps in order to process the rectangular titanium alloy specimens into a blade shape. The experiments were performed under identical conditions to verify the effectiveness of LAMill compared to CM. The cutting force, surface roughness and hardness were measured and a surface analysis was conducted to compare the machining characteristics after machining.

Manufacture of microscale random pattern using indentation machining technology

Je-Ryung Lee,Seung Hwan Moon,Tae-Jin Je,Doo-Sun Choi,Hwi Kim,Eun-chae Jeon 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.6

The display industries recently demand new microscale dot-type patterns for thinner and brighter displays with high energy efficiency, which are randomly distributed with irregular separation distances and have uniform optical characteristics. We developed a new program to generate the coordinates of the controlled microscale random patterns considering their diameter and the distance to the nearest pattern for preventing overlap of each pattern. Then the microscale random patterns were machined on a metal mold using the indentation machining which is a simple and low-cost machining method. We decreased the total machining time by the optimization of machining order of the random patterns. The coordinates, the diameter and the fi ll-factor of the machined patterns by the indentation machining were much consistent to the designed values. The controlled microscale random patterns had uniform optical characteristics over all areas of the manufactured optical fi lm. Moreover, if optical films have the same diameters and fi ll-factor, they showed the same optical characteristics even they have totally different coordinates of random microscale patterns. This technology is expected to reduce the number of the optical films and the light sources in the display, which can save much energies.

기계번역 활용 한국어 쓰기 수업에서 나타난 학습자 인식과 번역문의 특징

박수진 한국교양교육학회 2023 교양교육연구 Vol.17 No.3

This study examined how Korean learners perceive machine translation in Korean writing class, what the characteristics of machine-translated texts are, and what patterns appear depending on the level of Korean proficiency. Based on these results, this study aimed to suggest how machine translation in Korean writing class would help both of instructors and students. According to a survey of 77 Korean learners, 96% use machine translation and about 90% find it convenient. For beginners, most used machine translation when translating their native language into Korean, while intermediate and advanced learners used machine translation when translating Korean into their native language. Machine translation was mainly used for learning written language. In the second survey of same population, more than 98% of learners recognized that machine translation was convenient but inaccurate, and 97% required that there would be activities to use machine translation which could also provide feedback during class time. In sum, advanced level learners reviewed and modified machine-translated results more carefully than beginners and intermediate level learners, while beginners reviewed and modified less carefully than intermediate and advanced level learners. Thus based on this study, the teaching and learning methods for using machine translation in the writing class were presented as ‘1) finding problems and correcting one’s own language knowledge through self-correction after using machine translation, 2) discovering the differences between one’s mother tongue and Korean through back-translation activities, 3) discovering and using ways to reduce machine translation errors, where 4) the instructor should guide learners to discover cultural elements and provide explicit feedback., discovering various translations according to translation purpose and intention through cooperative activities.’ 이 연구에서는 한국어 쓰기 교양 수업에서 한국어 학습자들이 기계번역에 대해 어떻게 인식하는지, 기계번역을 활용하여 생성한 번역문의 특징은 어떠한지, 한국어 수준에 따라 어떤 양상이 나타나는지에 대해 살펴보았다. 그리고 이를 바탕으로 기계번역 활용 한국어 쓰기 수업의 교수⋅학습 방안을 제시하였다. 한국어 학습자 77명의 설문 조사 결과, 96%가 번역기를 사용하고 있고 90% 정도가 번역기 사용이편리하다고 하였다. 초급 학습자의 경우, 대다수가 모국어를 한국어로 번역할 때 기계번역을 사용하는 반면에 중급, 고급 수준의 학습자들은 한국어를 모국어로 번역할 때 기계번역을 사용하였다. 주로 문어 학습에 기계번역을 많이 사용하였다. 2차 설문 조사 결과, 98% 이상의 학습자들이 기계번역사용은 편리하나 부정확한 것으로 인식하였고 97%의 학습자들이 수업 시간에 기계번역을 사용하고 피드백하는 활동이 있기를 희망하였다. 초급 수준의 학습자보다 중급 학습자가, 그리고 중급보다 고급학습자가 기계번역 결과물을 더 세밀하게 검토하고 수정하는 것을 알 수 있었다. 초급 학습자들은 자기 수정 빈도가 가장 적게 나타났으며 기계번역 결과를 그대로 수용하는 경향이 강했으며 수정 시 문체에 집중하는 것을 알 수 있었다. 중급 학습자는 자기 수정의 성공률과 실패율이 고급 수준의 학습자와 큰 차이가 나타나지 않았으나 고급 수준의 학습자들은 기계번역 산출물의 대부분을 수정하였고 문장을 재구성하여 의미를 상세히 나타내려고 하였다. 이를 바탕으로 기계번역 활용 수업의 교수⋅학습 방안을 ‘1) 기계번역 활용 후 자기 수정을 통해 문제점을 찾고 자신의 언어지식 수정하기, 2) 역번역활동을 통해 학습자 스스로 모국어와 한국어의 차이 발견하기, 3) 기계번역 오류를 줄이는 방법을 발견하고 사용하기, 이때 4) 교수자는 특히 문화적 요소를 학습자들이 발견하도록 유도하고 명시적 피드백하기, 5) 협력 활동을 통해 번역 목적, 의도에 따른 다양한 번역문 발견하기’로 제시하였다.

Classification method for failure modes of RC columns based on key characteristic parameters

Bo Yu,Zecheng Yu,Qiming Li,Bing Li 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.1

An efficient and accurate classification method for failure modes of reinforced concrete (RC) columns was proposed based on key characteristic parameters. The weight coefficients of seven characteristic parameters for failure modes of RC columns were determined first based on the support vector machine-recursive feature elimination. Then key characteristic parameters for classifying flexure, flexure-shear and shear failure modes of RC columns were selected respectively. Subsequently, a support vector machine with key characteristic parameters (SVM-K) was proposed to classify three types of failure modes of RC columns. The optimal parameters of SVM-K were determined by using the ten-fold cross-validation and the grid-search algorithm based on 270 sets of available experimental data. Results indicate that the proposed SVM-K has high overall accuracy, recall and precision (e.g., accuracy>95%, recall>90%, precision>90%), which means that the proposed SVMK has superior performance for classification of failure modes of RC columns. Based on the selected key characteristic parameters for different types of failure modes of RC columns, the accuracy of SVM-K is improved and the decision function of SVM-K is simplified by reducing the dimensions and number of support vectors.