Variable amplitude fatigue test of M30 high-strength bolt in bolt-sphere joint grid structures

Bin Qiu,Honggang Lei,Xu Yang,Zichun Zhou,Guoqing Wang 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.3

Fatigue failure of a grid structure using bolt-sphere joints is liable to occur in a high-strength bolt due to the alternating and reciprocal actions of a suspension crane. In this study, variable amplitude fatigue tests were carried out on 20 40 Cr steel alloy M30 high-strength bolts using an MTS fatigue testing machine, and four cyclic stress amplitude loading patterns, Low-High, High- Low, Low-High-Low, and High-Low-High, were tested. The scanning electron microscope images of bolt fatigue failure due to variable amplitude stress were obtained, and the fractographic analysis of fatigue fractures was performed to investigate the fatigue failure mechanisms. Based on the available data from the constant amplitude fatigue tests, the variable amplitude fatigue life of an M30 high-strength bolt in a bolt-sphere joint was estimated using both Miner's rule and the Corten-Dolan model. Since both cumulative damage models gave similar predictions, Miner's rule is suggested for estimating the variable-amplitude fatigue life of M30 high-strength bolts in a grid structure with bolt-sphere joints; the S-N fatigue curve of the M30 high-strength bolts under variable amplitude loading was derived using equivalent stress amplitude as a design parameter.

초고해상 탄성파 탐사를 위한 3차원 역시간 구조보정 프로그램 개발

김대식,신정균,하지호,강년건,오주원 한국지구물리.물리탐사학회 2022 지구물리와 물리탐사 Vol.25 No.3

The computational efficiency of reverse time migration (RTM) based on numerical modeling is not secured due to the high-frequency band of several hundred Hz or higher for data acquired through a three-dimensional (3D) ultra-high-resolution (UHR) seismic survey. Therefore, this study develops an RTM program to derive high-quality 3D geological structures using UHR seismic data. In the traditional 3D RTM program, an excitation amplitude technique that stores only the maximum amplitude of the source wavefield and a domain-limiting technique that minimizes the modeling area where the source and receivers are located were used to significantly reduce memory usage and calculation time. The program developed through this study successfully derived a 3D migration image with a horizontal grid size of 1 m for the 3D UHR seismic survey data obtained from the Korea Institute of Geoscience and Mineral Resources in 2019, and geological analysis was conducted.

Fabrication Uncertainty and Noise Issues in High-Precision MEMS Actuators and Sensors

Cho, Young-Ho,Lee, Won-Chul,Han, Ki-Ho The Institute of Electronics and Information Engin 2002 Journal of semiconductor technology and science Vol.2 No.4

We present technical issues involved in the development of actuators and sensors for applications to high-precision Micro Electro Mechanical System (MEMS). The technical issues include fabrication uncertainty and noise disturbance, causing major difficulties for MEMS to achieve high-precision actuation and detection functions. For nano-precision actuators, we solve the fabrication instability and electrical noise problems using digital actuators coupled with nonlinear mechanical modulators. For the high-precision capacitive sensors, we present a branched finger electrodes using high-amplitude anti-phase sensing signals. We also demonstrate the potential applications of the nanoactuators and nanodetectors to high-precision positioning MEMS.

저변형률하 불포화 이암풍화토의 동적거동

허경한,정충선,배중선,Huh,Kyung-Han,Chung,Choong-Sun,Bae,Joong-Seon 한국방재학회 2004 한국방재학회논문집 Vol.4 No.2

본 연구는 정적은 물론 동적 거동에 관한 연구가 거의 없는 포항지역의 이암풍화토에 대하여 저변형률하에서의 동적 거동 파악을 위하여 수행되었다. 동적 거동에 영향을 미치는 요소들로는 간극비, 포화도 그리고 구속압 등 3가지의 변수를 설정하였다. 그 중 간극비와 포화도를 달리하여 공시체를 제작하고 구속압을 단계적으로 증가시켜가며 저변형률하에서의 전단탄성계수와 감쇠비의 거동을 고찰하였다. 이러한 저변형률하에서의 시험을 실시하기 위해 공진주 시험장치를 사용하였으며, 시험에서 얻어진 결과값들을 이용하여 이암풍화토의 동적 거동을 분석하였다. 연구결과에 의하면 저변형률하에서 이암풍화토의 최적포화도가 <TEX>$32{\sim}37%$</TEX> 나타났다. 이는 주광물의 비율과 형상뿐만 아니라 세립분의 함유량 차이로 인하여 화강풍화토보다 크게 나타났다. The interest in the dynamic properties of soils has increased strongly because of earthquake, heavy traffic, and foundations undergo high amplitude of vibrations. Most of soils in Korean peninsula are composed of granite soils, especially the decomposed mudstone soils are widely spread in Pohang areas, Kyong-buk province. Therefore, it is very important to investigate the dynamic properties of these types of soils. The most important soil parameters under dynamic loadings are shear modulus and material dampings. Furthermore, few definitive data exist that can evaluate the behavior of unsaturated decomposed mudstone soils under dynamic loading conditions. The investigations described in this paper is designed to identify the shear modulus and damping ratio due to a surface tension for the unsaturated decomposed mudstone soils under low and high strain amplitude. For this purpose, the resonant column test and the cyclic triaxial test were performed. Test results and data have shown that the optimum saturated degree of decomposed mudstone soils under low and strain amplitude is <TEX>$32{\sim}37%$</TEX> which is higher than that of decomposed granite due to the amount of fine particles as well as the type and proportion of chief rock-forming minerals.

대진폭 조화 운동을 하는 잠수구에 의한 비선형 조파문제의 시간영역 해석

김용직(YONG-JIG KIM),하영록(YOUNG-ROK HA) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.6

A high-order spectral/boundary-element method is newly adapted as an efficient numerical tool. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated and hydrodynamic forces also can be calculated in time-domain. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved by using the high-order spectral method and body potential is solved by using the high-order boundary element method. By the combination of these two methods, the wave-making problems by a submerged sphere oscillating with large amplitude under the free-surface are solved in time-domain. Through the example calculations, nonlinear effects on free-surface profiles and hydrodynamic forces are shown and discussed.

Simple Signal Detection Algorithm for 4+12+16 APSK in Satellite and Space Communications

이재윤,윤동원,현광민 한국우주과학회 2010 Journal of Astronomy and Space Sciences Vol.27 No.3

A 4+12+16 amplitude phase shift keying (APSK) modulation outperforms other 32-APSK modulations in a nonlinear additive white Gaussian noise (AWGN) channel because of its intrinsic robustness against AM/AM and AM/PM distortions caused by the nonlinear characteristics of a high-power amplifier. Thus, this modulation scheme has been adopted in the digital video broadcasting-satellite2 European standard. And it has been considered for high rate transmission of telemetry data on deep space communications in consultative committee for space data systems which provides a forum for discussion of common problems in the development and operation of space data systems. In this paper, we present an improved bits-to-symbol mapping scheme with a better bit error rate for a 4+12+16 APSK signal in a nonlinear AWGN channel and propose a simple signal detection algorithm for the 4+12+16 APSK from the presented bit mapping.

멀티베이스라인 인터페로미터 시스템에서의 자체 교정 방향 탐지 방법

김지태(Ji Tae Kim),김영수(Young Soo Kim),강종진(Jong-Jin Kang),이득영(Duk-Yung Lee),노지현(Ji Hyun Roh) 한국전자파학회 2010 한국전자파학회논문지 Vol.21 No.4

본 논문에서는 멀티베이스라인 인터페로미터 방향 탐지 시스템에서 진폭 및 위상 부정합 오차를 보정할 수 있는 공분산행렬 기반 자체 교정 알고리즘을 제안한다. 제안된 기법은 비용함수를 정의한 후 제한 조건을 갖는 비선형 최소화 방법으로서, 공간 섹터를 이용하여 부정합 오차를 획기적으로 교정하는 알고리즘이다. 다만 공간섹터를 선정하기 위하여 초기 추정각을 요구하는 단점이 있으나, 이는 일반적인 비선형 최소화 문제의 공통적인 단점이다. 적절한 공간 섹터 간격을 선정하여 시뮬레이션한 결과, 제안된 방법이 기존 인터페로미터 방식보다 표본바이어스, 표본표준편차, 평균제곱오차면에서 획기적으로 우수한 통계적 성능을 보여주었다. 더구나 섹터간격이 도래각과 5° 이내일 경우에, 30 ㏈의 진폭 부정합 및 50° 이상 큰 값의 위상 부정합이 발생하는 경우에도 획기적인 보정 능력을 보여주었으며, 신호대 잡음비에도 덜 민감한 특징을 나타내었다. In this paper, self-calibration algorithm based on covariance matrix is proposed for compensating amplitude/phase mismatch in multi-baseline interferometer direction finding system. The proposed method is a solution to nonlinear constrained minimization problem which dramatically calibrate mismatch error using space sector concept with cost function as defined in this paper. This method, however, has a drawback that requires an estimated initial angle to determine the proper space sector. It is well known that this type of drawback is common in nonlinear optimization problem. Superior calibration capabilities achieved with this approach are illustrated by simulation experiments in comparison with interferometer algorithm for a varitiety of amplitude/phase mismatch error. Furthermore, this approach has been found to provide an exceptional calibration capabilities even in case amplitude and phase mismatch are more than 30 ㏈ and over 50°, respectively, with sector spacing of less than 5°.

고성능 병렬 유한요소 솔버를 이용한 3차원 주시와 진폭계산

양동우 ( Dong Woo Yang ),김정호 ( Jung Ho Kim ) 한국지구물리·물리탐사학회 2004 지구물리와 물리탐사 Vol.7 No.4

초고속 카메라를 이용한 스페클 패턴 기반 미소 진동 분석

박태정,한성민,양희란,최장훈,송준영,최성록,이치범 한국소음진동공학회 2024 한국소음진동공학회 논문집 Vol.34 No.3

In this study, we present a method for measuring small amplitude vibrations using a high-speed camera. We project a laser onto an object to generate a speckle pattern that is then magnified using a lens and analyzed using a steerable pyramid. This vibration measurement method allows us to separate and measure vibrations based on the direction of the image. We demonstrated the effectiveness of our method by comparing it with traditional methods that do not generate a speckle pattern. Furthermore, we confirmed the validity of our methodology through frequency comparison experiments with a piezo accelerometer that is commonly used for vibration measurements. This novel approach to vibration measurement methodology can significantly advance research in this field.

경추통 환자에 대한 신장운동과 도수치료가 즉각적인 통증과 ROM에 미치는 효과

형인혁,김형수,이상열,Hyong, In-Hyouk,Kim, Hyoung-Su,Lee, Sang-Yeol 대한물리치료학회 2009 대한물리치료학회지 Vol.21 No.4

Purpose: Cervical pain is caused mainly by a static position, lasting work, bad habits and stress, and is accompanied by pain in the upper trapezius. Traditionally, heat and traction, exercise, mobilization, manipulation have been used to treat cervical pain. This study examined the effect of stretching and manipulation (high-velocity low-amplitude: HVLA) on the pain and ROM in women with chronic cervical and upper shoulder pain. Methods: Fifty-two women diagnosed with chronic cervical and upper shoulder pain were enrolled in this study. Among them, 26 patients (experiment group) were managed by passive stretching and manipulation, and another 26 patients (control group) were treated with physical therapy intervention (hat pack: HP, transcutaneous electrical nerve stimulation: TENS, ultra sound: US). Each group made use of a Visual Analogue Scale (VAS) and the highly reliable (flextion: 0.92, extention: 0.99) cervical range of motion (CROM) to compare the possible changes in pain and ROM in the two groups after treatment. Results: In the experimental group, the pain decreased and the ROM has increased in all directions. In the control group, the pain decreased but the ROM was not changed in all directions. Conclusion: According to the results, passive stretching and manipulation is effective for increasing the ROM and decreasing the level of pain. Moreover, physical therapy intervention (HP, TENS, US) is effective for immediately decreasing the pain but has little effect on the ROM.