• Title/Summary/Keyword: 재질감쇠

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Nondestructive Evaluation for Material Degradation of 2.25Cr-1Mo steel by Ultrasonic Wave (초음파를 이용한 재질열화의 비파괴적 평가)

  • 김정석;박은수;박인근;김현묵
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2000.10a
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    • pp.369-374
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    • 2000
  • This study has been achieved on the characteristics of ultrasonic wave in 2.25Cr-1Mo steel to evaluate the feasibility of ultrasonic nondestructive technique on the assessment of aging degradation. The measured values were used find a relationship between the ultrasonic propagation properties and degradation such as coarsening of carbides and precipitates. The ultrasonic attenuation coefficient was mainly affected by the grain size of prior austenitic phase as well as degradation. In this results, degradation and grain size in 2.25Cr-1Mo steel was able to cope with the changes in ultrasonic wave properties by applying the nondestructive evaluation method

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Structural and Dynamic Analysis of Mineral/glass Reinforced Polypropyolene Compound Automotive Engine Cover (Mineral/glass Reinforced Polypropylene Compound 재질 엔진 커버의 구조 및 동적 해석)

  • Kim, Beom-Keun;Kim, Heung-Seob;Kim, Yong-Su;Cho, Gyu-Chul;Jeong, Jae-Kwan
    • Composites Research
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    • v.20 no.3
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    • pp.63-66
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    • 2007
  • Structural analysis of automotive engine cover under vibration excitation is performed by finite element analysis (FEA) in order to identify the critical area of the structure. Assembly load due to the tightening of the bolts as well as the vibration excitation were considered to describe the actual loading condition. Natural frequencies of the system were extracted considering the damping effect of the structure. Dynamic analysis was performed based on the extracted natural frequency of the system. Experimental modal analysis (EMA) and measurement of strains were performed to verify the results of the analysis. Analysis results correlated closely with the experimental results. Analysis and experiments showed that contribution of the assembly load should not be ignored to predict the structural failure of the engine cover.

Bending Spring Model for Stable Strain-Based Dynamics in Triangular Meshes (삼각형 메쉬에서 안정적인 변형률 기반 동역학을 위한 굽힘 스프링 모델)

  • Kim, Jong-Hyun
    • Proceedings of the Korean Society of Computer Information Conference
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    • 2022.01a
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    • pp.341-344
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    • 2022
  • 본 논문에서는 삼각형 메쉬 기반에서 변형률 기반 동역학(Strain-based dynamics, SBD)을 안정적으로 표현할 수 있는 굽힘 스프링 구조와 감쇠 기법에 대해 설명한다. SBD는 삼각형 메쉬의 에지 길이(Edge length) 기반의 에너지 대신 변형률(Strain)을 활용하여 에너지를 모델링한다. 하지만, 비정상적인 삼각형(Degenerate triangle)인 경우 변형률이 불안정하게 계산되어 잘못된 방향으로 늘어나는 문제가 발생한다. 본 논문에서는 이러한 문제를 효율적으로 처리할 수 있는 굽힘 스프링(Bending spring) 구조에 대해 소개한다. 결과적으로 본 논문에서 제안하는 기법은 안정적으로 SBD를 처리할 수 있기 때문에 다양한 재질의 옷감 시뮬레이션을 안정적으로 표현할 수 있도록 한다.

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The Effects of Reducing a Dose on the Genital Gland at a CT Scan on the Whole Abdomen According to the Shielding Material (Whole Abdomen CT촬영 시 차폐 재료에 따른 생식선 선량 감쇠 효과)

  • Gang, Eun Bo;Park, Cheol Woo
    • Journal of the Korean Society of Radiology
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    • v.10 no.6
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    • pp.419-425
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    • 2016
  • The purpose of this study is to produce a shielding material to reduce a dose on the genital gland, one of the superficial organs, at a CT scan on the whole abdomen and hardly affect picture quality and examine its utility. This research made 22 mm silicone and 7.3 mm aluminum having the similar material quality and effect of previous bismuth. By using the non-shield, bismuth, 22 mm silicone, and 7.3 mm aluminum shielding materials, this author conducted a comparative experiment measuring the decay rate of the genital gland's exposure to radiation, change of the CT number and noise in the image, and the CT number, noise, and uniformity in the AAPM phantom. According to the results, exposure to radiation is reduced in bismuth as 29.96%, silicone 22 mm as 13.10%, and 7.3 mm aluminum as 18.27%. In bismuth, however, the image's CT number varies a lot, and uniformity is measured to be inappropriate in the AAPM phantom scan; therefore, it indicates great change in terms of picture quality in superficial organs like the genital gland. Concerning superficial organs like the genital gland, if 22 mm silicone and 7.3 mm aluminum are used as shielding materials, it will be helpful in reducing variation in picture quality and also decreasing radiation exposure to radiation.

Design and Properties of Microwave Absorbing Structures Composed of Fiber Reinforced Composites (섬유강화 복합재료로 구성된 전파흡수구조재의 설계 및 특성)

  • 김상영;김성수
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.6
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    • pp.1002-1008
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    • 2001
  • The absorbing structure composed of multi-layered fiber reinforced composite materials was designed and microwave absorbing properties are investigated. On the basis of transmission line theory, the theoretical equations to predict the reflection loss and the appropriate composite material for each functional layer are suggested. The most significant result of this study is the successful design and fabrication of triple-layered composite laminates which has the superior microwave absorbing porperties (more than 10 dB in 4∼12 GHz range), without using the ferrite filler in the impedance transforming layer. In the two-layered composite laminate (absorber/substrate), however, the use of ferrite filler (about 40 wt %) in the absorbing layer is necessary to obtain the certain level of microwave absorbance. By combining the glass-fiber composite with ferrite filler and carbon-fiber composite substrate, the microwave absorbing properties more than 10 dB in 4∼12 GHz frequencies than be obtained.

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Definition and Verification of the Dynamic Characteristics of the Anti-Vibration Mount for the Numerical Analysis (수치해석을 위한 방진 마운트의 동적 특성 결정 및 검증)

  • Han, Hyung-Suk;Park, Mi-Yoo;Cho, Heung-Gi;Kim, Joong-Gil;Im, Dong-Been
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.9
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    • pp.3190-3195
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    • 2010
  • Because the non-linear property of the rubber, the elastic modulus and damping factor of the rubber mount are dependent on the frequency. Therefore, the dynamic properties of the rubber mount should be considered when the anti-vibration mount is designed. Especially, when the numerical analysis is performed, the results can have much errors not considering the dynamic characteristics of the rubber mount. In this paper, the dynamic properties of typical standard rubber mount approved by ROK navy are defined experimentally and the results from the numerical analysis and experiment are compared for considering and non-considering the dynamic properties of the rubber mount respectively.

A Method of Analysis to Predict Sound Transmission Loss of an Extruded Aluminum Panel for Use on Railway Vehicles (철도차량용 알루미늄 압출재의 음향 투과손실 예측에 관한 연구)

  • Kim, Kwanju;Lee, Jun-Heon;Kim, Dae-Yong;Kim, Seock-Hyun
    • Journal of the Korean Society for Railway
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    • v.16 no.1
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    • pp.20-25
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    • 2013
  • The frame elements of modern high speed trains are typically fabricated with extruded aluminum panels. However, the sound transmission loss (STL) of extruded aluminum panels is less satisfactory than flat panels with the same surface density. This study proposes a method for prediction of the sound transmission loss of extruded aluminum panels using finite element analysis. The panel is modeled by finite element analysis, and the STL is calculated using a measure of Sommerfeld radiation at the specimen surface, boundary conditions, and the internal loss factor of the material. In order to verify the validity of the predicted value, intensity transmission loss was measured on the aluminum specimen according to ASTM E2249-02. The proposed method of analysis will be utilized to predict the sound insulation performance of extruded aluminum panels for railway vehicles in the design stage, and to establish measures for their improvement.

Identification of Fibers of Samsebul (Triple Buddha Statues) at Bonghwangsa in Andong (안동 봉황사 삼세불 제작에 사용된 섬유의 동정)

  • Cho, Kyoung-Sil;Baek, Young-Mee
    • Journal of Conservation Science
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    • v.28 no.4
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    • pp.297-303
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    • 2012
  • Samsebul, the altar portrait behind the statue of Buddha in the main building of Bonghwang temple in Andong, has been designated as Tangible Cultural Property No. 406. These alter portraits have significance as the standard of the research of Samsebul in Joseon period. In this study, fibre of the ground textile is identified using microscopic examination, solubility test, ATR-FT-IR, SEM, XRD. Two samples from Yaksabul(A, B), one sample from Seokgabul(C), and one sample from Amitabul(D), which were collected during the conservation process, were prepared for this study. In previous record, above samples were documented as hemp. Due to severe deterioration and accumulated dust layers on these samples, it was hard to recognize them with naked eyes, but through this study, we could identify that all samples except one from Yaksabul(A) are silk.

Efficient Sound Control Method in Virtual Environments Using Raytracing Based Diffraction

  • Kim, Jong-Hyun;Choi, Jong-In
    • Journal of the Korea Society of Computer and Information
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    • v.27 no.11
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    • pp.81-87
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    • 2022
  • In this paper, we propose diffraction-based sound control method to improve sound immersion in a virtual environment. The proposed technique can express the wave and flow of sound in a physical environment and a pattern similar to diffraction in real-time. Our approach determines whether there is an obstacle from the location of the sound source and then calculates the position of the new sound reflected and diffracted by the obstacle. Based on ray tracing, it determines whether or not it collides with an obstacle, and predicts the sound level of the agent behind the obstacle by using the vector reflected and refraction by the collision. In this process, the sound attenuation according to the distance/material is modeled by attenuating the size of the sound according to the number of reflected/refracted rays. As a result, the diffraction pattern expressed in the physics-based approach was expressed in real time, and it shows that the diffraction pattern also changes as the position of the obstacle is changed, thereby showing the result of naturally spreading the size of the sound. The proposed method restores the diffusion and diffraction characteristics of sound expressed in real life almost similarly.

On Evaluation of Material Properties in Spring Steels by Measurement of Ultrasonic Techniques (초음파법에 의한 스프링강의 재질평가에 관하여)

  • Kim, Sang-Su;Ha, Kyung-Jun;Kim, Seon-Jin
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2002.05a
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    • pp.41-46
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    • 2002
  • The general purpose of this paper is Evaluation of material properties in spring steels by investigate correlation between ultrasonic attenuation and virker's hardness, charpy impact properties, microstructures. The three test speciments of the $490{\times}90 mm$ plates and 20 mm thick are used but differ in heat treatment, one is rolled plate, the second is quenched and then tempered, and the third is quenched. ultrasonic attenuation were obtained at fifteen locations on the plates. In order to investigate the correlation between hardness ( especially, HV ) and the attenuation, the virker's hardness and the microstructures were observed for three spring steels. also the charpy impact test were carried out at the room temperature in order to investigate the relationship between impact properties and the attenuation. The experimental results obtained from three different spring related to the heat treatment conditions and attenuation coefficient is increased with increasing the hardness(HV). Ultrasonic attenuation coefficients have shawn are ability to distinguish among spring steels.

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