• Title/Summary/Keyword: initial deflection

Search Result 254, Processing Time 0.021 seconds

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
    • /
    • v.46 no.2
    • /
    • pp.67-75
    • /
    • 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.

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
    • /
    • v.26 no.11
    • /
    • pp.2415-2420
    • /
    • 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.

Effects of Partially Distributed Loads on Dynamic Response of Plane Parabolic Arch (부분분포하중이 평면 포물선아치의 동적응답에 마치는 영향)

  • Cho, Jin-Goo;Park, Keun-Soo
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.46 no.6
    • /
    • pp.21-28
    • /
    • 2004
  • This study aims to investigate the effects of partially distributed loads on the dynamic behaviour of steel parabolic arches by using the elasto-plastic finite element model based on the Von Mises yield criteria and the Prandtl-Reuss How rule. For this purpose, the vertical and the radial load conditions were considered as a distributed loading and the loading range is varied from 40% to 100% of arch span. Normal arch and arch with initial deflection were studied. The initial deflection of arch was assumed by the sinusoidal motile of ${\omega}_i\;=\;{\\omega}_O$ sin ($n{\pi}x/L$). Several numerical examples were tested considering symmetric initial deflection when the maximum initial deflection at the apex is fixed as L/1000. The analysis resluts showed that the maximum deflection at the apex of arch was occurred when 70% of arch span was loaded. The maximum deflection at the quarter point of arch span was occurred when 50% of arch span was loaded. It is known that the optimal rise to span ratio between 0.2 and 0.3 when the vertical or radial distributed load is applied. It is verified that the influence of initial deflection of radial load case is more serious than that of vertical load case.

Stress Relaxation Properties of Cucumber under Bending Moment (휨 모멘트에 대한 오이의 응력이완(應力弛緩) 특성(特性))

  • Song, C.H.;Kim, M.S.;Park, J.M.
    • Journal of Biosystems Engineering
    • /
    • v.18 no.3
    • /
    • pp.262-269
    • /
    • 1993
  • Stress relaxation behaviors of the cucumber under bending moment were tested with UTM at three levels of loading rate and initial deflection ratio. Sample cucumber was selected from three cultivars of cucumber, Cheongjangmadi, Baekdadagi, and Gyeousalicheongjang, because these cultivars are the most popular grown cultivars in Korea. When the bending moment was applied to the cucumber sample, the effective span between simple supports was held a constant value of 116mm with consideration of the selected sample length. The objectives of this study were to develop the rheological models such as linear and nonlinear models of the stress relaxation for the cucumber samples, and to investigate the effects of loading rate and initial deflection ratio on the stress relaxation behavior of the cucumber. The results of this study may be summarized as follows : 1. Stress relaxation behavior of the cucumber could be well described by the generalized Maxwell model for each level of deflection ratio. But the stress relaxation behavior of the sample was found to be initial deflection ratio and time dependent, and it was represented the nonlinear viscoelastic model as a function of initial deflection ratio and time. 2. Stress relaxation behavior of the cucumber samples was very highly affected by the loading rate and the initial deflection ratio. The more loading rate and initial deflection ratio resulted in the more initial bending stress and after stress relaxation progressed more rapidly. 3. At the same test conditions, it was found that the stress relaxation rate of Cheongjangmadi was faster than that of other cultivars.

  • PDF

Effect of Initial Defects on Welding Deformation and Residual Stress (강판의 초기不整이 용접변형.잔류응력에 미치는 영향)

  • 박정응
    • Journal of Welding and Joining
    • /
    • v.17 no.4
    • /
    • pp.76-84
    • /
    • 1999
  • The residual stress generated when the steel plates were produced, did not influence on the out-of-plane deformation and residual stress generated by welding. When the initial deflection shape was a concave(Type I), the out-of-plane deformation became the same shape as that of the initial deflection and its magnitude became small. When the initial deflection made a winding in the welding direction(Type III), the out-of-plane deformation became large in the plate width. The initial deflection shape did not influence on residual stress and plastic strain produced by welding.

  • PDF

Design Fabrication and Test of Piezoelectric Multi-Layer Cantilever Microactuators for Optical Signal Modulation (초기변형 최소화를 위한 광변조 압전 다층박막 액추에이터의 설계, 제작 및 실험)

  • Kim, Myeong-Jin;Jo, Yeong-Ho
    • The Transactions of the Korean Institute of Electrical Engineers C
    • /
    • v.49 no.9
    • /
    • pp.495-501
    • /
    • 2000
  • This paper presents a method to minimize the initial deflection of a multi-layer piezoelectric microactuator without loosing its piezoelectric deflection performance required for light modulating micromirror devices. The multi-layer piezoelectric actuator composed of PZT silicon nitride and platinum layers deflects or buckles due to the gradient of residual stress. Based on the structural analysis results and relationship between process conditions and mechanical properties we have modified the fabrication process and the thickness of thin film layers to reduce the initial residual stress deflection without decreasing its piezoelectric deflection performance. The modified designs fabricated by surface-micromachining process achieved the 77% reduction of the initial deflection compared with that of the conventional method based on the measured micromechanical material properties is applicable to the design refinement of multi-layer MEMS devices and micromechanical structures.

  • PDF

Ultimate strength of initially deflected plate under longitudinal compression: Part I = An advanced empirical formulation

  • Kim, Do Kyun;Poh, Bee Yee;Lee, Jia Rong;Paik, Jeom Kee
    • Structural Engineering and Mechanics
    • /
    • v.68 no.2
    • /
    • pp.247-259
    • /
    • 2018
  • In this study (Part I), an advanced empirical formulation was proposed to predict the ultimate strength of initially deflected steel plate subjected to longitudinal compression. An advanced empirical formulation was proposed by adopting Initial Deflection Index (IDI) concept for plate element which is a function of plate slenderness ratio (${\beta}$) and coefficient of initial deflection. In case of initial deflection, buckling mode shape, which is mostly assumed type in the ships and offshore industry, was adopted. For the numerical simulation by ANSYS nonlinear finite element method (NLFEM), with a total of seven hundred 700 plate scenarios, including the combination of one hundred (100) cases of plate slenderness ratios with seven (7) representative initial deflection coefficients, were selected based on obtained probability density distributions of plate element from collected commercial ships. The obtained empirical formulation showed good agreement ($R^2=0.99$) with numerical simulation results. The obtained outcome with proposed procedure will be very useful in predicting the ultimate strength performance of plate element subjected to longitudinal compression.

Estimation of the Ultimate Compressive Strength of Actual Ship Panels with Complex Initial Deflection (복잡(複雜)한 형상(形狀)의 초기(初期)처짐을 가진 실선(實船)의 Panel의 압괴강도(壓壞强度) 간이추정법(簡易推定法))

  • Paik, Jeom-K.;Kim, Gun
    • Bulletin of the Society of Naval Architects of Korea
    • /
    • v.25 no.1
    • /
    • pp.33-46
    • /
    • 1988
  • This paper describes a simplified method for estimation of the ultimate compressive strength of actual ship panels with initial deflection of complex shape. The proposed method consists of the elastic analysis using the large deflection theory and the rigid-plastic analysis based on the collapse mechanism which also includes the large deformation effect. In order to reduce the computing time for the elastic large deflection theory and the rigid-plastic analysis based on the collapse mechanism which also includes the large deformation effect. In order to reduce the computing time for the elastic large deflection analysis, only one term of Fourier series for the plate deflection is considered. The results of the proposed method are in good agreement with those calculated by the elasto-plastic large deflection analysis using F.E.M. and the computing time of the proposed method is extremely short compared with that of F.E.M.

  • PDF

A Study on the Snap-through Behaviour of Plate Elements due to the Initial Deflection Shape (초기처짐형상에 따른 판부재의 천이거동에 관한 연구)

  • Park, Joo-Shin;Lee, Kye-Hee;Ko, Jae-Yong
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.18 no.1
    • /
    • pp.13-20
    • /
    • 2005
  • Since High Tensile Steel has been widely used to thin plate on the steel structure and marine structure, It has increased possibility of buckling. Especially, initial deflection of ship structure is mainly caused by heat processing of welding or cutting etc. This initial deflection has negative effect to thin plate, which would incur a complicated nonlinear behavior accompanied with secondary buckling. If idealized initial deflection is considered in early marine structure design of secondary buckling, accuracy and reliability will be improved considerably. The measurement data of initial deflection from experiment is applied to finite element series analysis. For FEA(ANSYS), Applied nonlinear buckling analysis is used by Newton-Raphson method & Arc-length method included in this program.

A Study on the Compressive Ultimate Strength of Ship Plating with Complicated Shape of the Initial Deflection (복잡한 형상의 초기처짐을 가진 선체판의 압축최종강도에 관한 연구)

  • 고재용;박주신;이계희;박성현
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
    • /
    • 2004.04a
    • /
    • pp.83-88
    • /
    • 2004
  • Recently, High Tensile Steel is adapt to thin plate on the steel structure and marine structure is used widely. It is possible for buckling happens great. Specially, Initial deflection of ship structure happens in place absence necessarily by heat processing of welding or cutting etc. This Initial Deflection is exerted negative impact when thin plate absence complicated nonlinear behaviour accompanied secondary buckling. As a result, must idealize initial deflection that occurrence is possible to endow stability and accuracy in the hull structure or marine structure and reflect in early structure design considering secondary buckling. Longi direction of compressive load interacts and analyzed finite element series analysis that apply various kinds initial deflection shape measured actually on occasion that is arranged simply supported condition in this research. Applied ANSYS (elasto-plasticity large deformation finite element method) to be mediocrity finite element program for analysis method and analysis control used in Newton-Raphson method & Arc-length method.

  • PDF