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조인식(Insik Cho),전용호(Yongho Jeon),신충식(Choongshig Shin),곽동호(Dongho Kwak),이지용(Jiyong Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Due to the extensive long service life for aero-space components, the behavior of very high cycle fatigue(VHCF) is gained attention. For this reason, the newly developed piezoelectric ultrasonic fatigue test (UFT) system by Mbrosiatec Co. Ltd is used to investigate the high cycle fatigue (HCF) strength of Ti-6Al-4V alloy. The hourglass-shaped specimens are investigated in the range of 10<SUP>6</SUP> to 10<SUP>9</SUP> cycles at room temperature under completely reversed loading conditions R=-1. Scanning electron microscopy(SEM) analysis revealed that failures occur right up to the gigacycle regime, with the fractures being found to initiate from the surface unlike in steels. In addition, SEM micrographs showed that micro-cracks were transformed into intergranular fracture. Additionally, this test method can be applicable on commercialized parts of automotive and rail road which are required high cycle fatigue. In addition, SEM micrographs showed that micro-cracks were transformed into intergranular fracture.
조인식(InSik Cho),박중철(JungCheol Park),구병춘(ByeongChoon Goo) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Evaluation of the test is based on the ultrasonic fatigue test method for a material which requires high cycle fatigue life and basic fatigue tests with standard KS B ISO 1099 and is designated as ASTM E 466 and the main difference is in the way of the load based on the load and the load added by using an ultrasonic acoustic resonance. UFT utilizes a piezoelectric oscillator(piezoelectric actuator) to generate an ultrasonic waves train at a frequency of 20 ㎑ and it amplifies the amplitude to which a fatigue test can be performed. In UFT, the maximum displacement occurs at the end of the specimen, while the maximum stress amplitude occurs in the center of the specimen. Dynamic Young`s modulus is required in order to obtain the maximum stress amplitude which can be obtained from acoustic test according to the ASTM E1875 standard. Therefore, the evaluation method of UFT machine and test methods and processes, related fields overseas research trends and technological level and reliability need to be standardized.
조인식(Insik Cho),이창순(Changsoon Lee),편영식(Youngshik Pyoun),박인규(Ingyu Park),김병훈(Byounghoon Kim) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
An ultrasonic fatigue testing device, capable of fracturing the tested materials at an ultrasonic frequency of 20 ㎑ is demonstrated. Such a testing device, operating at high frequencies, not only reduces the testing time to far less than that of conventional testing machines, but may also better simulate extremely high-frequency loading and the strong influence of strain rate on the fatigue behavior of the tested materials. This makes the development of an ultrasonic fatigue testing device for testing materials is an important endeavor. Very high cycle fatigue of Al 6061-T6 alloy was investigated using accelerated ultrasonic fatigue testing at 20 ㎑ under completely reserved loading conditions (R=-1) on a piezoelectric machine which was developed by DaeJin Science Co., Ltd. In this study, the ultrasonic fatigue tests were conducted in the range of 10?~10? fatigue fracture cycles, while testing maximum amplitude stress (S) was 117.76 ㎫ at gigacycle. Scanning electron microscopy (SEM) analyses were carried out and the results show that three crack fracture modes were observed.
경량 데이터베이스를 이용한 칼로리 관리 애플리케이션 설계 및 구현
홍지혜 ( Jihye Hong ),조인식 ( Insik Cho ),이영구 ( Young-koo Lee ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.1
최근 헬스케어에 대한 관심이 급증하면서, 운동을 통한 칼로리 관리 애플리케이션 연구들이 진행되고 있다. 기존의 연구들은 행위 인식 모델이 정교하지 못할 뿐만 아니라, 기초적인 행위 인식 기술을 사용하여 정확한 운동량을 측정하기 어렵다. 또한, 파일 시스템을 이용하여 센서, 행위, 칼로리 등의 다양한 데이터를 효과적으로 관리하기 어렵다. 본 논문에서는 경량 데이터베이스를 이용하여 개인의 칼로리 섭취량 및 소모량을 관리해주는 시스템을 제안한다. 제안하는 시스템은 스마트폰용 경량 데이터베이스에 저장된 데이터를 활용하여 효과적으로 칼로리를 관리하며, 칼로리 소모량 측정 정확도를 높이기 위해 계층적 행위 인식 모델을 제시한다.
피로강도 향상 및 경량화와 마찰손실 저감을 위한 초음파나노표면개질기술 응용연구
편영식(Youngsik Pyoun),조인식(Insik Cho),홍정화(Junghwa Hong),이창순(Changsoon Lee),박인규(Ingyu Park),서창민(Chang-Min Suh),조인호(Inho Cho),김창식(Changsik Kim) 한국자동차공학회 2007 한국자동차공학회 Symposium Vol.- No.-
Reductions of fuel consumption and CO₂ emission are main goals of recent vehicle development. Increasing fatigue strength, weight and friction reduction of power train components are very effective methods for this goal. Peening technology which induces compressive residual stress on the surface is very efficient technology. Modification of surface topology into micro dimples is a new technology to reduce friction coefficient. Brief introduction of these technologies are presented with comparison of their characteristics and effects. UNSM(Ultrasonic Nano crystal Surface Modification) technology induces a large amount of compressive residual stress in the subsurface, refines the grain size into 50~200 ㎚, and modifies the surface into micro dimple structure which reduces the friction coefficient about 50% simultaneously. Introduction and successful examples of UNSM application are presented. Application results to hub bearing and application idea to crankshaft are also presented. How to satisfy cost criteria is also considered.