• Title/Summary/Keyword: Longitudinal Control

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Buckling and free vibration analysis of tapered FG- CNTRC micro Reddy beam under longitudinal magnetic field using FEM

  • Mohammadimehr, M.;Alimirzaei, S.
    • Smart Structures and Systems
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    • v.19 no.3
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    • pp.309-322
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    • 2017
  • In this paper, the buckling, and free vibration analysis of tapered functionally graded carbon nanotube reinforced composite (FG-CNTRC) micro Reddy beam under longitudinal magnetic field using finite element method (FEM) is investigated. It is noted that the material properties of matrix is considered as Poly methyl methacrylate (PMMA). Using Hamilton's principle, the governing equations of motion are derived by applying a modified strain gradient theory and the rule of mixture approach for micro-composite beam. Micro-composite beam are subjected to longitudinal magnetic field. Then, using the FEM, the critical buckling load, and natural frequency of micro-composite Reddy beam is solved. Also, the influences of various parameters including ${\alpha}$ and ${\beta}$ (the constant coefficients to control the thickness), three material length scale parameters, aspect ratio, different boundary conditions, and various distributions of CNT such as uniform distribution (UD), unsymmetrical functionally graded distribution of CNT (USFG) and symmetrically linear distribution of CNT (SFG) on the critical buckling load and non-dimensional natural frequency are obtained. It can be seen that the non-dimensional natural frequency and critical buckling load decreases with increasing of ${\beta}$ for UD, USFG and SFG micro-composite beam and vice versa for ${\alpha}$. Also, it is shown that at the specified value of ${\alpha}$ and ${\beta}$, the dimensionless natural frequency and critical buckling load for SGT beam is more than for the other state. Moreover, it can be observed from the results that employing magnetic field in longitudinal direction of the micro-composite beam increases the natural frequency and critical buckling load. On the other hands, by increasing the imposed magnetic field significantly increases the stability of the system that can behave as an actuator.

A Study on the Behavior Characteristics of Residual Stress of the Thin Butt Weldment by Mechanical Tensioning Method (인장법에 의한 박판 판계 용접부의 잔류 응력 거동 특성에 관한 연구)

  • Kim, Ha-Keun;Kim, Kyung-Ku;Shin, Sang-Beom
    • Proceedings of the KWS Conference
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    • 2010.05a
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    • pp.57-57
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    • 2010
  • For thin panel welded structure, the various welding distortions were found due to the low resistance against welding deformation. Especially, buckling distortion induced in the thin panel welded structure produce severe problems related to cost in production stage and safety in service life. So, many researches including mechanical and thermal tensioning method for preventing the occurrence of buckling distortion in the production stage have been performed. The purpose of this study is to identify the behavior of longitudinal residual stress at the SA butt weldment with thin plate of 6mm thickness under tension load by 3 dimensional FEA. For it, mesh design for 3D FEA was constructed with 20 nodes brick element for butt weldment and 8 nodes shell element for base metal. According to FEA results, the longitudinal compressive strain inducing tensile residual stress at the butt weldment decreased. It was because the compressive thermal strain in way of weldment was reduced by tension load. The control effect of residual stress increased with an increase in tension load. So, if the amount of tension load applied to the weldment exceeds 1.5 times of longitudinal shrinkage force, the amount of longitudinal residual stress decreased below the critical value inducing the buckling distortion at the SA butt weldment. Its validity was verified by experiment.

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Analytical Study on the Reinforced Details of Orthotropic Steel Deck Bridge (강바닥판 교량의 보강상세에 관한 해석적 연구)

  • Kyung, Kab-Soo;Shin, Dong-Ho;Kim, Kyo-Hoon;Park, Kyung-Jin
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.4
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    • pp.443-451
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    • 2007
  • The improvement of stiffness by the increase of thickness of deck plate or the reinforcement of longitudinal rib is one method among the effective methods to control fatigue damages occurring in orthotropic steel deck. It is likely that the increase of stiffness is effective to restrain local deformation caused by axial load in the steel deck. Therefore, in this study, the parameter studies for the reinforced structural details such as the bulk-head plate and vertical rib which is established to reduce the resultant stresses in the connection parts of the longitudinal rib and floor beam were performed with FE analysis. From the results, it was known that the reinforced structural detail with the bulk-head plate in the longitudinal ribs reduced overall the principal stresses at the connection parts, but the stress concentration increased in the weld toe parts which are occurring fatigue cracks. Also, it was estimated that the reinforced structural detail with the vortical rib in the longitudinal ribs because of the reduction of stress concentration in the weld toe parts is more effective details than the bulk-head plate.

Wind Tunnel Test of an Unmanned Aerial Vehicle (UAV)

  • Chung, Jin-Deog;Lee, Jang-Yeon;Sung, Bong-Zoo;Koo, Sa-Mok
    • Journal of Mechanical Science and Technology
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    • v.17 no.5
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    • pp.776-783
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    • 2003
  • A low speed wind tunnel test was conducted for full-scale model of an unmanned aerial vehicle (UAV) in Korea Aerospace Research Institute (KARI) Low Speed Wind Tunnel(LSWT). The purpose of the presented paper is to illustrate the general aerodynamic and performance characteristics of the UAV that was designed and fabricated in KARI. Since the testing conditions were represented minor portions of the load-range of the external balance system, the repeatability tests were performed at various model configurations to confirm the reliability of measurements. Variations of drag-polar by adding model components such as tails, landing gear and test boom are shown, and longitudinal and lateral aerodynamic characteristics after changing control surfaces such as aileron, flap, elevator and rudder are also presented. To explore aerodynamic characteristics of an UAV with model components build-up and control surface deflections, lift curve slope, pitching moment variation with lift coefficients and drag-polar are examined. The discussed results might be useful to understand the general aerodynamic characteristics and drag pattern for the given UAV configuration.

Slender piezoelectric beams with resistive-inductive electrodes - modeling and axial wave propagation

  • Schoeftner, Juergen;Buchberger, Gerda;Benjeddou, Ayech
    • Smart Structures and Systems
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    • v.18 no.2
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    • pp.335-354
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    • 2016
  • This contribution presents an extended one-dimensional theory for piezoelectric beam-type structures with non-ideal electrodes. For these types of electrodes the equipotential area condition is not satisfied. The main motivation of our research is originated from passive vibration control: when an elastic structure is covered by several piezoelectric patches that are linked via resistances and inductances, vibrational energy is efficiently dissipated if the electric network is properly designed. Assuming infinitely small piezoelectric patches that are connected by an infinite number of electrical, in particular resistive and inductive elements, one obtains the Telegrapher's equation for the voltage across the piezoelectric transducer. Embedding this outcome into the framework of Bernoulli-Euler, the final equations are coupled to the wave equations for the longitudinal motion of a bar and to the partial differential equations for the lateral motion of the beam. We present results for the wave propagation of a longitudinal bar for several types of electrode properties. The frequency spectra are computed (phase angle, wave number, wave speed), which point out the effect of resistive and inductive electrodes on wave characteristics. Our results show that electrical damping due to the resistivity of the electrodes is different from internal (=strain velocity dependent) or external (=velocity dependent) mechanical damping. Finally, results are presented, when the structure is excited by a harmonic single force, yielding that resistive-inductive electrodes are suitable candidates for passive vibration control that might be of great interest for practical applications in the future.

Control Law Design for a Tilt-Duct Unmanned Aerial Vehicle using Sigma-Pi Neural Networks (Sigma-Pi 신경망을 이용한 틸트덕트 무인기의 제어기 설계연구)

  • Kang, Youngshin;Park, Bumjin;Cho, Am;Yoo, Changsun
    • Journal of Aerospace System Engineering
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    • v.11 no.1
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    • pp.14-21
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    • 2017
  • A Linear parameterized Sigma-Pi neural network (SPNN) is applied to a tilt-duct unmanned aerial vehicle (UAV) which has a very large longitudinal stability ($C_{L{\alpha}}$). It is uncontrollable by a proportional, integral, derivative (PID) controller due to heavy stability. It is shown that the combined inner loop and outer loop of SPNN controllers could overcome the sluggish longitudinal dynamics using a method of dynamic inversion and pseudo-control to compensate for reference model error. The simulation results of the way point guidance are presented to evaluate the performance of SPNN in comparison to a PID controller.

Longitudinal Developmental Paths of Preschooler's External Problem Behaviors: Focusing on Maternal Depression, Marital Conflict, Maternal Social Parenting Style and Preschooler's Effortful Control in Infancy (유아기 외현화 문제행동의 종단적 발달경로: 영아기 어머니의 우울, 부부갈등, 어머니의 사회적 양육행동과 영아기 의도적 통제를 중심으로)

  • Moon, Youngkyung
    • Human Ecology Research
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    • v.57 no.3
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    • pp.431-444
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    • 2019
  • This study explored the longitudinal developmental paths of preschooler's external problem behaviors from infancy. Subjects consisted of 205 preschoolers (106 boys, 99 girls aged 4) and their mothers recruited for the 2009 in-depth Panel Study on Korean Children. Data were analyzed by descriptive statistics, correlations, and structural equation modeling using SPSS 18.0 (SPSS Co., Chicago, IL, USA), Amos 18.0 (SPSS Co., Chicago, IL, USA). The results were as follows: Maternal depression at preschooler's age 0 had a direct effect on maternal social parenting style at preschooler's age 0. Maternal social parenting style at preschooler's age 0 had a direct effect on preschooler's effortful control at age 1. Preschooler's effortful control at age 1 had a direct effect on preschooler's external problem behaviors at age 4. Marital conflict at preschooler's age 0 did not have a direct effect on preschooler's effortful control at age 1. The direct effects of maternal depression at preschooler's age 0 on preschooler's effortful control at age 1, and on preschooler's external problem behaviors at age 4 were not significant. In addition, direct effect of maternal social parenting style at preschooler's age 0 on preschooler's external problem behaviors at age 4 was not significant. This study showed that maternal psychological characteristics, marital conflict, maternal social parenting style and preschooler's effortful control in infancy should be considered simultaneously to explain the effect on preschooler's external problem behaviors.

An Longitudinal Analysis of Changing Beliefs on the Use in IT Educatee by Elaboration Likelihood Model (정교화 가능성 모형에 의한 IT 피교육자 신용 믿음 변화의 종단분석)

  • Lee, Woong-Kyu
    • Asia pacific journal of information systems
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    • v.18 no.3
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    • pp.147-165
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    • 2008
  • IT education can be summarized as persuading the educatee to accept IT. The persuasion is made by delivering the messages for how-to-use and where-to-use to the educatee, which leads formulation of a belief structure for using IT. Therefore, message based persuasion theory, as well as IT acceptance theories such as technology acceptance model(TAM), would play a very important role for explaining IT education. According to elaboration likelihood model(ELM) that has been considered as one of the most influential persuasion theories, people change attitude or perception by two routes, central route and peripheral route. In central route, people would think critically about issue-related arguments in an informational message. In peripheral route, subjects rely on cues regarding the target behavior with less cognitive efforts. Moreover, such persuasion process is not a one-shot program but continuous repetition with feedbacks, which leads to changing a belief structure for using IT. An educatee would get more knowledge and experiences of using IT as following an education program, and be more dependent on a central route than a peripheral route. Such change would reformulate a belief structure which is different from the intial one. The objectives of this study are the following two: First, an identification of the relationship between ELM and belief structures for using IT. Especially, we analyze the effects of message interpretation through both of central and peripheral routes on perceived usefulness which is an important explaining variable in TAM and perceived use control which have perceived ease of use and perceived controllability as sub-dimensions. Second, a longitudinal analysis of the above effects. In other words, change of the relationship between interpretation of message delivered by IT education and beliefs of IT using is analyzed longitudinally. For achievement of our objectives, we suggest a research model, which is constructed as three-layered. While first layer has a dependent variable, use intention, second one has perceived usefulness and perceived use control that has two sub-concepts, perceived ease of use and perceived controllability. Finally, third one is related with two routes in ELM, source credibility and argument quality which are operationalization of peripheral route and central route respectively. By these variables, we suggest five hypotheses. In addition to relationship among variables, we suggest two additional hypotheses, moderation effects of time in the relationships between perceived usefulness and two routes. That is, source credibility's influence on perceived usefulness is decreased as time flows, and argument quality's influence is increased. For validation of it, our research model is tested empirically. With measurements which have been validated in the other studies, we survey students in an Excel class two times for longitudinal analysis. Data Analysis is done by partial least square(PLS), which is known as an appropriate approach for multi-group comparison analysis with a small sized sample as like this study. In result. all hypotheses are statistically supported. One of theoretical contributions in this study is an analysis of IT education based on ELM and TAM which are considered as important theories in psychology and IS theories respectively. A longitudinal analysis by comparison between two surveys based on PLS is also considered as a methodological contribution. In practice, finding the importance of peripheral route in early stage of IT education should be notable.

Experimental Investigations of Flow Characteristics by Wing Type Vortex Generators Set up Behind a Circular Cylinder in a Rectangular Channel (사각채널내 와동발생기가 부착된 원형실린더 하류 유동 특성에 대한 실험적 연구)

  • 이상민;하홍영;양장식;이기백
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.5
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    • pp.1076-1085
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    • 2001
  • Experimental investigations of the longitudinal vortices, which are produced by wing type vortex generators set up behind a circular cylinder in a rectangular channel, are presented. When the circular cylinder is set up in the rectangular channel, a horseshoe vortex is formed just upsteam of the circular cylinder. It generates a turbulent wake region behind the circular cylinder. Therefore, the region of the pressure loss behind the circular cylinder in increased and the size of the wake is small. These problems can be achieved by longitudinal vortices which are generated by wing-type vortex generator. In order to control the strength of longitudinal vortices, the angle of attack of the vortex generators is varied from 20 degree to 45, but the spacing between the vortex generators is fixed 6cm. The 3-dimensional mean velocity measurements are made using a five-hole probe. The vorticity field and streamwise velocity contour are obtained from the velocity field. The following results are obtained. Circulation strength is the maximum value when the angle of attack($\beta$) is $30^{\circ}$, and the vorticity field and streamwise velocity contour in case of $\beta$=$20^{\circ}$ show the trend similar to these in case of $\beta$=$30^{\circ}$, but do not in case of $\beta$=$45^{\circ}$.

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Behavior of a tunnel face reinforced with longitudinal pipes - laboratory investigation (실내실험에 의한 수평보강재로 보강된 터널막장의 거동)

  • Yoo, Chung-Sik;Yang, Ki-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.2
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    • pp.91-100
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    • 2002
  • This paper presents the results of laboratory investigation on the deformation behavior of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests was carried out to investigate the effect of reinforcement layout on the tunnel face axial displacement as well as the surface settlement. Among other things, the results of the model tests indicate that the axial displacement of tunnel face as well as the ground surface settlement can significantly be reduced by pre-reinforcing the tunnel face with longitudinal pipes, suggesting that the pre-reinforcing technique may effectively be used as a positive ground control method in the urban environments. Also illustrated is that the reinforcing effect is significantly influenced by the reinforcement layout. The implications of the findings from this study are discussed in a great detail.

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