• Title/Summary/Keyword: Force curve

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Evaluation of Age-Hardening Characteristics of Squeeze-Cast A356 Alloy by Using Micro/Nano Indenter with AFM (나노/마이크로 인덴터와 AFM을 이용한 스퀴즈 캐스트 A356 합금의 시효경화특성 평가)

  • Youn S.W.;Kim K.D.;Kang C.G.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.1398-1401
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    • 2005
  • The nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in squeeze-cast A356 alloy were investigated using nano/micro-indentation and mechanical scratching, combined wit optical microscopy and atomic force microscope(AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. In addition, the eutectic region showed lower pile-up and higher elastic recovery than the primary Al region. The aging responses of the eutectic regions in the squeeze-cast A356 alloys aged at $150^{\circ}C$ for different times(0, 2, 4, 8, 10, 16, 24, 36 and 72 h) were investigated. As the aging time increased, acicular Si particles in the eutectic regions gradually came to a fine structure. Both Vickers hardness ($H_V$) and indentation ($H_{IT}$) test results showed almost the same trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.

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A Study on Structural Safety of a Urethane Wheel Using FEM (유한요소법을 이용한 우레탄 휠의 구조 안전성에 관한 연구)

  • 송하종;정일호;이수호;박태원;박중경;이형;조동협;김혁;이경목
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.1042-1047
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    • 2004
  • Urethane is a high polymeric and elastic material useful in designing mechanic parts that cannot be molded in rubber or plastic material. Especially, urethane is high in mechanical strength and anti-abrasive. Hereby, an urethane coated aluminum wheel is used for supporting of OHT vehicle moving back and forth to transport products. For the sake of verifying the safety of the vehicle, structural safety for applied maximum dynamic load on a urethane wheel needs to be carefully examined while driving. Therefore, we have performed the dynamic simulation on the OHT vehicle model. Although the area definition of applied load can be obtained from the previous study of Hertzian and Non-Hertzian contact force model when having exact properties of contact material, static analysis is simulated, since the proper material properties of urethane have not been guaranteed, after we have performed the actual contact area test for each load. In case of this study, the method of distributing load for each node is included. Finally, in comparison with result of analysis and load-displacement curve obtained from the compression test, we have defined the material properties of urethane. In the analysis, we have verified the safety of the wheel. After all, we have performed a mode analysis using the obtained material properties. With the result, we have the reliable finite element model.

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A Response to Postural Response to Sine Curve Vestibular Electric Stimulation during Standing (기립자세동안 전정기관에 인가된 정현파 전류자극에 대한 자세균형 응답)

  • Lee, Ah-Reum;Yu, Mi;Kim, Jin-Ho;Kim, Dong-Wook;Kim, Jung-Ja
    • Journal of Biomedical Engineering Research
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    • v.31 no.3
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    • pp.210-216
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    • 2010
  • This study is vestibular electric stimulation applied between the mastoids during quiet standing elicits postural sway. The aim of this study was to characterize the postural sway response to continuous sinusoidal vestibular electric stimulation across various stimulus frequencies and amplitudes. Binaural bipolar sinusoidal vestibular electric stimulation was applied to the skin overlying the mastoid processes of 10 subjects while they stood on a force plate. The position of the center of pressure(COP) and signals at the feet are obtained on an force plate, while the head and whole body center of mass(COM) was measured with motion analysis system. The stimulus conditions included eight frequencies (1/64, 1/32, 1/16, 1/8, 1/4, 1/2, 1, and 2Hz) and six peak amplitudes (0.1, 0.25, 0.5, 0.7, 1 and 2mA). Each subject experienced one trial at each amplitude-frequency pair. The stimuli elicited sway in lateral plane in all subjects, as evidenced by changes in the stimulus frequency. Our results demonstrate that the vestibular system is sensitive to vestibular electric stimulation intensity changes and responds by altering the magnitude of the response accordingly.

Geometric and Material Nonlinear Analysis of Single Layer Dome using ABAQUS (유한요소 해석을 이용한 단층 래티스 돔의 비선형비탄성 해석)

  • Kim, Yeon-Tae;Jeong, Mi-Roo;Lee, Jae-Hong
    • Proceeding of KASS Symposium
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    • 2008.05a
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    • pp.119-124
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    • 2008
  • Space structure is a appropriate shape that resists external force only with in-plane force by reducing the influence of bending moment, and it maximizes the effectiveness of structure system. The space structure should be analized by nonlinear analysis regardless static and dynamic analysis because it accompanies large deflection for member. To analyze the structure of the space structure exactly generally geometrically nonlinear and material nonlinear, complex nonlinear analysis are considered. To settle the weakness that geometric nonlinear problem does not consider nonlinear as per trait and position of the structure material and that the nonlinear matter of structure material also does not consider nonlinear as per geometric form. Therefore, In this paper, analysis is considered geometric nonlinear and material nonlinear simultaneous conditioning, and traced load-deflection curve by using ABAQUS which is the general purpose of the finite element program.

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An Exploratory Study on the Possibility of Quantitative Measurement during Abdominal Examinations - A Preliminary Study on the Development of a Diagnostic Device for Abdominal Examinations (한의복진법의 정량화를 위한 탐색적 임상연구 - 한의 복진기기 개발을 위한 예비 연구 -)

  • Lee, Jae-hong;Kim, Sang-jin;Ko, Seok-jae;Park, Jae-woo
    • The Journal of Internal Korean Medicine
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    • v.37 no.6
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    • pp.940-948
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    • 2016
  • Objectives: This exploratory trial evaluated the possibility of quantitatively measuring several aspects during the "abdominal examination" of traditional Korean medicine. The main results of this study will be used to develop a new diagnostic device for abdominal examinations. Methods: Fifteen healthy volunteers were recruited for this study. Three certified Korean medical doctors assessed the existence of pressure pain, the elasticity of the abdominal muscle, and the tonus at CV12 as gold standards. Then, 2 well-trained investigators measured the pressure pain threshold (PPT), the indentation depth of a bar, and repelling force by pressing CV12. Each investigator measured the above 3 variables 2 times at 1 min intervals using a modified digital algometer. Reliability and validity tests of the 3 variables were performed. Results: There were statistically significant coefficients of intraclass correlation on the 3 variables both between and within the investigators (P<0.001). Also, PPT and repelling force showed statistically significant high sensitivity and specificity in a ROC curve. However, the indentation depth of the bar presented relatively low sensitivity. Conclusions: This new diagnostic method using a modified digital algometer could be a useful tool for quantitative measurement in "abdominal examinations". However, future rigorous clinical studies with a large population will be needed for the verification of its usefulness.

A Study on the Goal Setting Method for Increasing the Holed Probability in Slope Putting Stroke on an Artificial Putting Surface

  • Park, Jin;Kim, Ji Hyeon;Jung, Jong Min
    • Korean Journal of Applied Biomechanics
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    • v.27 no.4
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    • pp.269-278
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    • 2017
  • Objective: The purpose of this study was to develop a goal setting method for increasing the probability of a holed in a side inclined putting stroke. Method: Three-dimensional video data was recorded at a frequency of 120 hz per second after synchronizing 19 infrared motion capture systems (Qualisys, Gothenburg, Sweden). Putting green used a polycarbonate plate ($1.2{\times}2.4{\times}0.01meter$) with coefficient of friction (${\mu}=0.062$) and a real curve of the actual hole. Results: The velocity ratio between the club and the ball was 1:1.6 under various ball speed conditions in this study. The overall position of the break is 1 m to 1.4 m from the point where the ball leaves. If there is a slope, the ball follows the target line by the straightening force, and when it reaches 1 m position, the straightening force decreases by 30~50% and reaches to the deviation (break) point which is severely influenced by the slope. From here, the ball is aimed in a direction other than the target, and the size is affected by the slope. Conclusion: If there is a side slope, the ball moves away from the straight line, and the larger the slope, the closer the break point is to the starting point of the ball. Therefore, it is necessary to calculate the degree of departure according to the slope carefully, and it is preferable that the slower the speed is, the more the influence of the slope becomes. It is preferable to use the center of the hole as a reference when calculating the departure.

A Smart Damper Using Magnetic Friction And Precompressed Rubber Springs (자력 마찰과 기압축 고무 스프링을 이용한 스마트 댐퍼)

  • Choi, Eun Soo;Choi, Gyu Chan
    • Journal of Korean Society of Steel Construction
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    • v.28 no.4
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    • pp.223-229
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    • 2016
  • This study proposes a new technology for a smart damper with flag-shaped behavior using the combination of magnetic friction and rubber springs. The magnet provides friction and, thus, energy dissipation, and the rubber springs with precompression contribute to present self-centering capacity of the damper. To verify their performance, this study conducts dynamic tests of magnet frictional dampers and precompressed rubber springs. For the purpose, hexahedron Neodymium (NdFeB) magnets and polyurethane rubber cylinders are used. In the dynamic tests, loading frequency varies from 0.1 to 2.0 Hz. The magnets provide almost perfect rectangular behavior in force-deformation curve. The rubber springs are tested without or with precompression. The rubber springs show larger rigid force with increasing precompression. Lastly, this study discusses combination of rigid-elastic behavior and friction to generate 'flag-shaped' behavior for a smart damper and suggests how to combine the magnets and the rubber springs to obtain the flag-shaped behavior.

Performance Test and Numerical Model Development of Restoring Viscous Damper for X-type Damper System (X형 감쇠시스템을 위한 복원성 점성 감쇠기 성능 실험 및 수치모형 개발)

  • Kim, David;Park, Jangho;Ok, Seung-Yong;Park, Wonsuk
    • Journal of the Korean Society of Safety
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    • v.31 no.6
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    • pp.52-57
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    • 2016
  • In this study, a restoring viscous damper is introduced for X-type damper system which is designed for the seismic response control of large spatial structures. A nonlinear numerical model for its behavior is developed using the result of dynamic loading tests. The X-type damper system is composed of restoring viscous dampers and connecting devices such as adjustable wire bracing, where the damping capacity of the system is controllable by changing the number of the dampers. The restoring viscous damper is devised to exert main damping force in tension direction, which is effective to prevent the buckling of bracing subjected to compressive axial force. To evaluate the performance of the proposed damper, dynamic cyclic loading tests are performed by using manufactured dampers at full scale. In order to construct the numerical model of the damper system, its model parameters are first identified using a nonlinear curve fitting method with the test data. The numerical simulations are then performed to validate the accuracy of the numerical model in comparison with the experimental test results. It is expected that the proposed system is effectively applicable to various building structures for seismic performance enhancement.

Analog active valve control design for non-linear semi-active resetable devices

  • Rodgers, Geoffrey W.;Chase, J. Geoffrey;Corman, Sylvain
    • Smart Structures and Systems
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    • v.19 no.5
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    • pp.487-497
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    • 2017
  • Semi-active devices use the building's own motion to produce resistive forces and are thus strictly dissipative and require little power. Devices that independently control the binary open/closed valve state can enable novel device hysteresis loops that were not previously possible. However, some device hysteresis loops cannot be obtained without active analog valve control allowing slower, controlled release of stored energy, and is presents an ongoing limitation in obtaining the full range of possibilities offered by these devices. This in silico study develops a proportional-derivative feedback control law using a validated nonlinear device model to track an ideal diamond-shaped force-displacement response profile using active analog valve control. It is validated by comparison to the ideal shape for both sinusoidal and random seismic input motions. Structural application specific spectral analysis compares the performance for the non-linear, actively controlled case to those obtained with an ideal, linear model to validate that the potential performance will be retained when considering realistic nonlinear behaviour and the designed valve control approach. Results show tracking of the device force-displacement loop to within 3-5% of the desired ideal curve. Valve delay, rather than control law design, is the primary limiting factor, and analysis indicates a ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, relating valve performance to structural period and overall device performance under control. Overall, the results show that active analog feedback control of energy release in these devices can significantly increase the range of resetable, valve-controlled semi-active device performance and hysteresis loops, in turn increasing their performance envelop and application space.

A Study on Structural Safety of a Urethane Wheel Using FEM (유한요소법을 이용한 우레탄 휠의 구조 안전성에 관한 연구)

  • Song Ha Jong;Jong Il Ho;Yoon Ji Won;Jun Kab Jin;Park Joong Kyung;Lee Hyung;Park Tae Won
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.10 s.175
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    • pp.114-120
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    • 2005
  • Urethane is a high polymeric and elastic material useful in designing mechanic parts that cannot be molded with rubber or plastic material. In particular, urethane is high in mechanical strength and anti-abrasive. Hereby, a urethane coated aluminum wheel is used to support of the OHT vehicle moving back and forth to transport products. For the sake of verifying the safety of the vehicle, structural safety fur applied maximum dynamic load on a urethane wheel must be examined carefully while driving. Therefore, we performed a dynamic simulation on the OHT vehicle model and we determined the driving load. The area definition of applied load may be obtained from the previous study of Hertzian and Non-Hertzian contact force model having exact properties of contact material. But the static analysis is simulated after we have performed the actual contact area test for each load since the proper material properties of urethane have not been guaranteed. In this study, the method of distributing loads for each node is included. Finally, in coMParison with the results of analysis and load-displacement curve obtained from the compression test, we have defined the material properties of urethane. In the analysis, we verified the safety of the wheel. Finally, we performed a mode analysis using the obtained material properties. With these results, we presented a reliable finite element model.