• Title/Summary/Keyword: deflection

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The Practice of Bending Deflection using Non-destructive MOE of Glulam (비파괴 탄성계수를 이용한 집성재의 휨변형 예측)

  • Park, Jun-Chul;Hong, Soon-Il
    • Journal of the Korean Wood Science and Technology
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    • v.37 no.1
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    • pp.48-55
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    • 2009
  • In the glulam beam deflection it is necessary to check the reliability of theory formula, because of wood anisotropy and wood qualities (knot, slop of grain). In this experiment, when bending stress occurred on glulam, practice deflection of glulam measuring with AICON DPA-Pro 3D system were compared with prediction deflection calculated as substituting MOE through non-destructive testing and static MOE through bending test in differential equation of deflection curve. MOE using ultrasonic wave tester of laminae, MOE using natural frequencies of longitudinal vibrations ($E_{cu}$, $E_{cf}$), MOE using ultrasonic wave tester of glulam ($E_{gu}$) and MOE using natural frequencies of longitudinal vibrations ($E_{gf}$) were substituted in this experiment. When practice deflection measured by 3D system was compared with prediction deflection calculated with differential equation of deflection curve, within proportional limit the ratio of practice deflection and prediction deflection was similar as 1.12 and 1.14, respectively. Deflection using ultrasonic wave tester was 0.89 and 0.95, Deflection using natural frequencies of longitudinal vibrations was 1.07 and 1.10. The results showed that prediction deflection calculated by substituting using non-destructive MOE of glulam having anisotropy in differential equation of deflection curve was agreed well with practice deflection.

Minimization of Initial Deflection of Multi-Layered Micro-Actuator with Step-Up Structure (Step-Up 구조를 갖는 다층박막 초소형 구동소자의 초기변형 최소화에 관한 연구)

  • Lee, Hee-Joong;Kang, Shin-Ill
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.11
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    • pp.2415-2420
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    • 2002
  • In the present study, a new anchor design was proposed to minimize the initial deflection of micro multi-layer cantilever beam with step-up structure, which is a key component of thin film micro-mirror array. It is important to minimize the initial deflection, caused by residual stress, because it reduces the performance of the actuation. Theoretical and experimental studies were conducted to examine the cause of the initial bending deflection. It was found that the bending deflection at the anchor of the cantilever beam was the primary source of initial deflection. Various anchor designs were proposed and the initial deflections for each design were calculated by finite element analysis. The analysis results were compared with experiments. To reduce the initial deflection a secondary support was added to the conventional structure. The optimal shapes were obtained by simulation and experiment. It was found from the analysis that the ratio or horizontal and vertical dimensions of secondary support was the governing factor, which affected the initial deflection.

The Sensitivity Enhancement for the Deflection Sensor of the Marine Gyrocompass Follow-up System (자이로콤파스 추종계통 편각검출기에 관한 연구)

  • 이상집;이은방
    • Journal of the Korean Institute of Navigation
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    • v.12 no.2
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    • pp.33-42
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    • 1988
  • As a basic study for enhancing the sensitivity of the follow-up system of the marine gyrocompass, the geometric characteristics of the deflection sensor were investigated and the theoretical model of it was formulated. The output signal voltage of the deflection sensor was esamined by changing the attitude of gyrosphere against follow-up container. The characteristics of the output are found to be indentical with those of the distance difference versus the relative azimuthal deflection of the gyrosphere against the follow up container. On the base of the theoretical model, some useful points for the design of the deflection sensor are suggested as following : 1. When the difference between semidiamter of gyrophere and that of the follow-up container decreases, the sensitivity of deflection sensor increases. 2. If the semidiameter difference of two spheres is constant, the sensitivity of deflection sensor is proportional to the magnitude of the semidiamter of each sphere. 3. The farther the gyrosphere is deviated from the center of follow-up container, the higher the sensitivity of deflection sensor is. 4. It is recommendable that the value of the datum deflection of the electrodes on the gyrosphere should be within the range between $4^{\circ}$ and $16^{\circ}$deviated from north-south line.

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Tool Deflection Estimation in Micro Flat End-milling Using Finite Element Method (유한요소법을 이용한 마이크로 평엔드밀링에서의 공구변형 예측)

  • Lim, Jeong-Su;Cho, Hee-Ju;Seo, Tae-Il
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.4
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    • pp.498-503
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    • 2010
  • The main purpose of this study strongly concerned micro machining error estimation by using FEM analysis of tool deflection shapes in micro flat end-milling process. For the precision micro flat end-milling process, analysis of micro cutting errors is mandatory. In general, tool deflection is a major factor which causes cutting error and limits realization of the high-precision cutting process. Especially, in micro end-milling process, micro tool deflection generates very serious problems in contrast to macro tool deflection. Methods which deal with compensation of cutting error by tool deflection in macro end-milling process have been studied plentifully but, few researches transact with micro scaled cutting tool deflection in micro cutting process. Therefore, the trend of micro tool deflection was estimated by using FEM analysis in this paper. Cutting forces were acquired by micro dynamometer and these were utilized in FEM analysis. In order to verify FEM analysis results, micro machining processes were carried out and real machined profiles were compared with FEM results. Finally through the proposed approach well suited FEM results were obtained.

Investigation of Live Load Deflection Limit for Steel Cable Stayed and Suspension Bridges

  • Park, Ki-Jung;Kim, Do-Young;Hwang, Eui-Seung
    • International journal of steel structures
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    • v.18 no.4
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    • pp.1252-1264
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    • 2018
  • Long span bridges such as steel cable stayed and suspension bridges are usually more flexible than short to medium span bridges and expected to have large deformations. Deflections due to live load for long span bridges are important since it controls the overall heights of the bridge for securing the clearance under the bridge and serviceability for securing the comfort of passengers or pedestrians. In case of sea-crossing bridges, the clearance of bridges is determined considering the height of the ship master from the surface of the water, the trim of the ship, the psychological free space, the tide height, and live load deflection. In the design of bridges, live load deflection is limited to a certain value to minimize the vibrations. However, there are not much studies that consider the live load deflection and its effects for long span bridges. The purpose of this study is to investigate the suitability of live load deflection limit and its actual effects on serviceability of bridges for steel cable-stayed and suspension bridges. Analytical study is performed to calculate the natural frequencies and deflections by design live load. Results are compared with various design limits and related studies by Barker et al. (2011) and Saadeghvaziri et al. (2012). Two long span bridges are selected for the case study, Yi Sun-Sin grand bridge (suspension bridge, main span length = 1545 m) and Young-Hung grand bridge (cable stayed bridge, main span length = 240 m). Long-term measured deflection data by GNSS system are collected from Yi Sun-Sin grand bridge and compared with the theoretical values. Probability of exceedance against various deflection limits are calculated from probability distribution of 10-min maximum deflection. The results of the study on the limitation of live load deflection are expected to be useful reference for the design, the proper planning and deflection review of the long span bridges around the world.

Compensation Control of Mechanical Deflection Error on SCARA Robot with Constant Pay Load Using Neural Network (일정한 가반 하중이 작용하는 스카라 로봇에 대한 신경망을 이용한 기계적 처짐 오차 보상 제어)

  • Lee, Jong-Shin
    • Journal of Institute of Control, Robotics and Systems
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    • v.15 no.7
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    • pp.728-733
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    • 2009
  • This paper presents the compensation of mechanical deflection error in SCARA robot. End of robot gripper is deflected by weight of arm and pay-load. If end of robot gripper is deflected constantly regardless of robot configuration, it is not necessary to consider above mechanical deflection error. However, deflection in end of gripper varies because that moment of each axis varies when robot moves, it affects the relative accuracy. I propose the compensation method of deflection error using neural network. FEM analysis to obtain the deflection of gripper end was carried out on various joint angle, the results is used in neural network teaming. The result by simulation showed that maximum relative accuracy reduced maximum 9.48% on a given working area.

Deflection Estimation of a PSC Railroad Girder using Long-gauge Fiber Optic Sensors (Long-gauge 광섬유 센서를 이용한 철도교 PSC 거더의 처짐유추)

  • Chung Won-Seok;Kim Sung-Il;Kim Nam-Sik;Lee Hee-Up
    • Journal of the Korean Society for Railway
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    • v.9 no.4 s.35
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    • pp.467-472
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    • 2006
  • This paper deals with the applicability of long-gauge deformation fiber optic sensors (FOS) to prestressed concrete structures. A main motivation is the desire to monitor the deflection of the railway bridges without intervenes of the signal intensity fluctuations. A 25 m long, 1.8 m deep PSC girder was fabricated compositely with 22 cm thick reinforced concrete deck. Two pairs of 3 m long-gauge sensors are attached to the prestressed concrete girder with parallel topology. Using the relationship between curvature and vortical deflection and the quadratic regression of curvatures at the discrete point, it is possible to extrapolate the deflection curve of the girder. The estimated deflection based on the developed method is compared with the results using conventional strain gauges and LVDTS. It has been demonstrated that the proposed instrumentation technique is capable of estimating the vertical deflection and neutral axis position of the prestressed concrete girder up to weak nonlinear region.

Study of Deflection around Hydropierced Hole with Experiment (하이드로 피어싱 시험을 통한 구멍 주위의 꺼짐 현상 분석)

  • Han, S.S.;Kang, Y.S.;Kim, G.H.
    • Transactions of Materials Processing
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    • v.16 no.3 s.93
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    • pp.157-162
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    • 2007
  • The hydropiercing process gives a lot of advantages to the tube hydroforming such as cost reduction and high productivity. However it has a drawback, the amount of deflection around the hole is bigger than that of conventional die piercing process. The deflection can cause the problem at the assembly process of stamped parts and hydroformed part. Therefore the reduction of deflection is one of the most important issues for hydropiercing process. In this study, the deflection around hydropierced hole was investigated by experiment. As a result of investigation, the amount of deflection is influenced by the internal pressure, the material thickness' and the size of hole. Especially the hole size is most influencing factor on the deflection around the hydropierced hole.

Dynamic Behavior of Plane Parabolic Arches with Initial Deflections (초기 처짐을 갖는 평면 포물선 아치의 동적 거동)

  • Cho , Jin-Goo;Park, Keun-Soo
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.2
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    • pp.67-75
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    • 2004
  • This study aims to investigate the dynamic behaviour of a parabolic arch with initial deflection by using the elasto-plastic finite element model where the von-Mises yield criteria have been adopted. The initial deflection of arch was assumed by the high order polynomial of ${\omega}_i$ = ${\omega}_o$${(1-{(2x/L)}^m)}^n$) and the sinusoidal profile of ${\omega}_i$ = ${\omega}_o$$\sin$(n$\pi$x/L). Several numerical examples were tested considering symmetric initial deflection modes when the maximum initial deflection of an arch is fixed as L/500, L/1000, L/2000 or L/5000. The effects of polynomials order on the dynamic behavior of arch were not conspicuous. The most unfavorite dynamic response occurs when the maximum initial deflection varies from L/1000 to L/4000 if the initial deflection mode is represented by high order polynomials.

Long-term deflection of high-strength fiber reinforced concrete beams

  • Ashour, Samir A.;Mahmood, Khalid;Wafa, Faisal F.
    • Structural Engineering and Mechanics
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    • v.8 no.6
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    • pp.531-546
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    • 1999
  • The paper presents an experimental and theoretical study on the influence of steel fibers and longitudinal tension and compression reinforcements on immediate and long-term deflections of high-strength concrete beams of 85 MPa (12,300 psi) compressive, strength. Test results of eighteen beams subjected to sustained load for 180 days show that the deflection behavior depends on the longitudinal tension and compression reinforcement ratios and fiber content; excessive amount of compression reinforcement and fibers may have an unfavorable effect on the long-term deflections. The beams having the ACI Code's minimum longitudinal tension reinforcement showed much higher time-dependent deflection to immediate deflection ratio, when compared with that of the beams having about 50 percent of the balanced tension reinforcement. The results of theoretical analysis of tested beams and those of a parametric study show that the influence of steel fibers in increasing the moment of inertia of cracked transformed sections is most pronounced in beams having small amount of longitudinal tension reinforcement.