• Title/Summary/Keyword: Nonlinear Vibration Analysis

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Thermal frequency analysis of FG sandwich structure under variable temperature loading

  • Sahoo, Brundaban;Mehar, Kulmani;Sahoo, Bamadev;Sharma, Nitin;Panda, Subrata Kumar
    • Structural Engineering and Mechanics
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    • v.77 no.1
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    • pp.57-74
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    • 2021
  • The thermal eigenvalue responses of the graded sandwich shell structure are evaluated numerically under the variable thermal loadings considering the temperature-dependent properties. The polynomial type rule-based sandwich panel model is derived using higher-order type kinematics considering the shear deformation in the framework of the equivalent single-layer theory. The frequency values are computed through an own home-made computer code (MATLAB environment) prepared using the finite element type higher-order formulation. The sandwich face-sheets and the metal core are discretized via isoparametric quadrilateral Lagrangian element. The model convergence is checked by solving the similar type published numerical examples in the open domain and extended for the comparison of natural frequencies to have the final confirmation of the model accuracy. Also, the influence of each variable structural parameter, i.e. the curvature ratios, core-face thickness ratios, end-support conditions, the power-law indices and sandwich types (symmetrical and unsymmetrical) on the thermal frequencies of FG sandwich curved shell panel model. The solutions are helping to bring out the necessary influence of one or more parameters on the frequencies. The effects of individual and the combined parameters as well as the temperature profiles (uniform, linear and nonlinear) are examined through several numerical examples, which affect the structural strength/stiffness values. The present study may help in designing the future graded structures which are under the influence of the variable temperature loading.

A Study for Damping Application to Response-controlled Structure

  • Shinozaki, Yozo;Mogi, Yoshihiro;Ota, Masaaki;Yoshikawa, Hiroaki
    • International Journal of High-Rise Buildings
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    • v.10 no.2
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    • pp.149-164
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    • 2021
  • Most of high-rise buildings in Japan*1 are structure with damping systems recently. The design procedure is performance-based design (PBD), which is based on the nonlinear response history procedure (NRHP) using 2 or 3-dimentional frame model. In addition, hysteretic property of steel plates or velocity-dependent property of viscous dampers are common practice for the damping system. However, for the selection of damping system, the easy dynamic analysis of recent date may lead the most of engineers to focus attention on the maximum response only without thinking how it shakes. By nature, the seismic design shall be to figure out the action of inertia forces by complex & dynamic loads including periodic and pulse-like characteristics, what we call seismic ground motion. And it shall be done under the dynamic condition. On the contrary, we engineers engineers have constructed the easy-to-use static loads and devoted ourselves to handle them. The structures with damping system shall be designed considering how the stiffness & damping to be applied to the structures against the inertia forces with the viewpoint of dynamic aspect. In this paper we reconsider the role of damping in vibration and give much thought to the basic of shake with damping from a standpoint of structural design. Then, we present some design examples based on them.

Mitigation of seismic pounding between two L-shape in plan high-rise buildings considering SSI effect

  • Ahmed Abdelraheem Farghaly;Denise-Penelope N. Kontoni
    • Coupled systems mechanics
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    • v.12 no.3
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    • pp.277-295
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    • 2023
  • Unsymmetrical high-rise buildings (HRBs) subjected to earthquake represent a difficult challenge to structural engineering, especially taking into consideration the effect of soil-structure interaction (SSI). L-shape in plan HRBs suffer from big straining actions when are subjected to an earthquake (in x- or y-direction, or both x- and y- directions). Additionally, the disastrous effect of seismic pounding may appear between two adjacent unsymmetrical HRBs. For two unsymmetrical L-shape in plan HRBs subjected to earthquake in three different direction cases (x, y, or both), including the SSI effect, different methods are investigated to mitigate the seismic pounding and thus protect these types of structures under the earthquake effect. The most effective technique to mitigate the seismic pounding and help in seismically protecting these adjacent HRBs is found herein to be the use of a combination of pounding tuned mass dampers (PTMDs) all over the height (at the connection points) together with tuned mass dampers (TMDs) on the top of both buildings.

Vibrations and stress analysis of perforated functionally graded rotating beams

  • Alaa A. Abdelrahman;Hanaa E. Abd-El-Mottaleb;Mohamed G. Elblassy;Eman A. Elshamy
    • Steel and Composite Structures
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    • v.49 no.6
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    • pp.667-684
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    • 2023
  • In the context of finite element method, a computational simulation is presented to study and analyze the dynamic behavior of regularly perforated functionally graded rotating beam for the first time. To investigate the effect of perforation configurations, both regular circular and squared perforation patterns are studied. To explore impacts of graded material distributions, both axial and transverse gradation profiles are considered. The material characteristics of graded materials are assumed to be smoothly and continuously varied through the axial or the thickness direction according the nonlinear power gradation law. A computational finite elements procedure is presented. The accuracy of the numerical procedure is verified and compared. Resonant frequencies, axial displacements as well as internal stress distributions throughout the perforated graded rotating cantilever beam are studied. Effects of material distributions, perforation patterns, as well as the rotating beam speed are investigated. Obtained results proved that the graded material distribution has remarkable effects on the dynamic performance. Additionally, circular perforation pattern produces more softening effect compared with squared perforation configuration thus larger values of axial displacements and maximum principal stresses are detected. Moreover, squared perforation provides smaller values of nondimensional frequency parameters at most of vibration modes compared with circular pattern.

Bending and Vibration Analysis of Elastic and Viscoelastic Laminated Composite Structures using an Improved Higher-order Theory (개선된 고차이론을 이용한 복합재료 적층구조물의 탄성 및 점탄성적 휨, 진동해석)

  • Han, Sung Cheon;Yoo, Yong Min;Park, Dae Yong;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.14 no.1
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    • pp.1-12
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    • 2002
  • To obtain more accurate responses of laminated composite structures, the effect of transverse shear deformation, transverse normal strain/stress and a nonlinear variation of in-plane displacements with respect to the thickness coordinate need to be considered in the analysis. The improved higher-order theory is used to determine the deflections and natural frequencies of laminated composite structures. A quasi-elastic method is used for the solution of viscoelastic analysis of the laminated composite plates and sandwiches. Solutions of simply-supported laminated composite plates and sandwiches are obtained and the results are compared with those by the 3D elasticity theory and other theories. The improved theory proposed in this paper is shown to predict the deflections and natural frequencies more accurately than all other theories.

Study on the Determination of Fatigue Damage Parameter for Rubber Component under Multiaxial Loading (다축하중이 작용하는 방진고무부품 피로손상 파라미터 결정에 관한 연구)

  • Moon, Seong-In;Woo, Chang-Su;Kim, Wan-Doo
    • Elastomers and Composites
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    • v.47 no.3
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    • pp.194-200
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    • 2012
  • Rubber components have been widely used in automotive industry as anti-vibration components for many years. These subjected to fluctuating loads, often fail due to the nucleation and growth of defects or cracks. To prevent such failures, it is necessary to understand the fatigue failure mechanism for rubber materials and to evaluate the fatigue life for rubber components. The objective of this study is to develop the durability analysis process for vulcanized rubber components, which is applicable to predict fatigue life at initial product design step. The determination method of nonlinear material constants for FE analysis was proposed. In order to investigate the applicability of the commonly used damage parameters, fatigue tests and corresponding finite element analyses were carried out and strain energy density was proposed as the fatigue damage parameter for rubber components. The fatigue analysis for automotive rubber components was performed and the durability analysis process was reviewed.

Non-linear Shimmy Analysis of a Nose Landing Gear with Free-play (유격을 고려한 노즈 랜딩기어의 비선형 쉬미 해석)

  • Yi, Mi-Seon;Hwang, Jae-Up;Bae, Jae-Sung;Hwang, Jae-Hyuk
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.10
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    • pp.973-978
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    • 2010
  • In this paper, we studied the shimmy phenomena of an aircraft nose landing gear considering free-play. Shimmy is a self-excited vibration in lateral and torsional directions of a landing gear during either the take-off or landing. This phenomena is caused by a couple of conditions such as low torsional stiffness of the strut, friction and free-play in the gear, wheel imbalance, or worn parts, and it may make an aircraft unstable. Free-play non-linearity is linearized by the described function for a stability analysis in a frequency domain, and time marching is performed using the fourth-order Runge-Kutta method. We performed the numerical simulation of the nose landing gear shimmy and investigated its linear and nonlinear characteristics. From the numerical results, we found limit-cycle-oscillations at the speed under linear shimmy speed for the case considering free-play and it can be concluded that the shimmy stability can be decreased by free-play.

A Frequency Domain Analysis of Corneal Deformation by Air Puff (Air puff에 의한 각막 변형의 주파수 영역 분석)

  • Hwang, Ho-Sik;Lee, Byeong Ha;Lee, Chang Su
    • Journal of IKEEE
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    • v.18 no.2
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    • pp.240-247
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    • 2014
  • Intraocular pressure is measured after a cornea air puff by observing biomechanical properties such as thickness or displacement of the cornea. In this paper, we deal with a frequency domain analysis of corneal deformation in the air puff tonometry that is used to diagnose glaucoma or lasik. We distinguish the patient from the normal by measuring the oscillation frequency in the neighborhood of the central cornea section. A binary image was obtained from the video images, and cornea vertical oscillation profile was extracted from the difference between the vertical displacement data and the curve fitting. In terms of Fourier transform, a vibration frequency of 479.2Hz for the patient was obtained as well as more higher 702.8Hz for the normal due to stiffness. Hilbert-Huang transform's empirical mode decomposition generally describes local, nonlinear, and nonstationary data. After the data were decomposed into intrinsic mode functions, a spectrum and power were analysed. Finally, we confirm that the patient has 6 times more higher power ratio for the specific intrinsic mode function between the patient and the normal.

Development of Airframe Structure for Disaster and Public Safety Multicopter UAV (재난치안용 멀티콥터 무인기 기체구조 개발)

  • Shin, Jeong Woo;Lee, Seunggyu;Noh, Jeong Ho
    • Journal of Aerospace System Engineering
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    • v.14 no.3
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    • pp.69-77
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    • 2020
  • Airframe structure development of the 35 kg class 'Disaster and Public Safety Multicopter' UAV is described in this paper. To reduce the airframe weight, T-700 grade CFRP composite material was used, and the fuselage was designed with the semi-monocoque structure and plate installed with the control and communication devices designed in a sandwich structure. The specimen tests for the laminated plate and pipe were conducted to verify the strength and stiffness of the designed parts. The stacking sequence of composite materials was determined by the static strength and vibration analysis, and landing gear strut was designed by the nonlinear analysis with decent speed and ground clearance requirements. The static strength test was performed to evaluate the structural integrity and to verify the landing gear behavior.

Design of Sliding Mode Fuzzy Controller for Vibration Reduction of Large Structures (대형구조물의 진동 감소를 위한 슬라이딩 모드 퍼지 제어기의 설계)

  • 윤정방;김상범
    • Journal of the Earthquake Engineering Society of Korea
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    • v.3 no.3
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    • pp.63-74
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    • 1999
  • A sliding mode fuzzy control (SMFC) algorithm is presented for vibration of large structures. Rule-base of the fuzzy inference engine is constructed based on the sliding mode control, which is one of the nonlinear control algorithms. Fuzziness of the controller makes the control system robust against the uncertainties in the system parameters and the input excitation. Non-linearity of the control rule makes the controller more effective than linear controllers. Design procedure based on the present fuzzy control is more convenient than those of the conventional algorithms based on complex mathematical analysis, such as linear quadratic regulator and sliding mode control(SMC). Robustness of presented controller is illustrated by examining the loop transfer function. For verification of the present algorithm, a numerical study is carried out on the benchmark problem initiated by the ASCE Committee on Structural Control. To achieve a high level of realism, various aspects are considered such as actuator-structure interaction, modeling error, sensor noise, actuator time delay, precision of the A/D and D/A converters, magnitude of control force, and order of control model. Performance of the SMFC is examined in comparison with those of other control algorithms such as $H_{mixed 2/{\infty}}$ optimal polynomial control, neural networks control, and SMC, which were reported by other researchers. The results indicate that the present SMFC is an efficient and attractive control method, since the vibration responses of the structure can be reduced very effectively and the design procedure is simple and convenient.

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