A nonlinear structural experiment platform with adjustable plastic hinges: analysis and vibration control

Luyu Li,Gangbing Song,Jinping Ou 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.11 No.3

The construction of an experimental nonlinear structural model with little cost and unlimited repeatability for vibration control study represents a challenging task, especially for material nonlinearity. This paper reports the design, analysis and vibration control of a nonlinear structural experiment platform with adjustable hinges. In our approach, magnetorheological rotary brakes are substituted for the joints of a frame structure to simulate the nonlinear material behaviors of plastic hinges. For vibration control, a separate magnetorheological damper was employed to provide semi-active damping force to the nonlinear structure. A dynamic neural network was designed as a state observer to enable the feedback based semi-active vibration control. Based on the dynamic neural network observer, an adaptive fuzzy sliding mode based output control was developed for the magnetorheological damper to suppress the vibrations of the structure. The performance of the intelligent control algorithm was studied by subjecting the structure to shake table experiments. Experimental results show that the magnetorheological rotary brake can simulate the nonlinearity of the structural model with good repeatability. Moreover, different nonlinear behaviors can be achieved by controlling the input voltage of magnetorheological rotary damper. Different levels of nonlinearity in the vibration response of the structure can be achieved with the above adaptive fuzzy sliding mode control algorithm using a dynamic neural network observer.

A nonlinear structural experiment platform with adjustable plastic hinges: analysis and vibration control

Li, Luyu,Song, Gangbing,Ou, Jinping Techno-Press 2013 Smart Structures and Systems, An International Jou Vol.11 No.3

The construction of an experimental nonlinear structural model with little cost and unlimited repeatability for vibration control study represents a challenging task, especially for material nonlinearity. This paper reports the design, analysis and vibration control of a nonlinear structural experiment platform with adjustable hinges. In our approach, magnetorheological rotary brakes are substituted for the joints of a frame structure to simulate the nonlinear material behaviors of plastic hinges. For vibration control, a separate magnetorheological damper was employed to provide semi-active damping force to the nonlinear structure. A dynamic neural network was designed as a state observer to enable the feedback based semi-active vibration control. Based on the dynamic neural network observer, an adaptive fuzzy sliding mode based output control was developed for the magnetorheological damper to suppress the vibrations of the structure. The performance of the intelligent control algorithm was studied by subjecting the structure to shake table experiments. Experimental results show that the magnetorheological rotary brake can simulate the nonlinearity of the structural model with good repeatability. Moreover, different nonlinear behaviors can be achieved by controlling the input voltage of magnetorheological rotary damper. Different levels of nonlinearity in the vibration response of the structure can be achieved with the above adaptive fuzzy sliding mode control algorithm using a dynamic neural network observer.

The structure optimization of tracked ambulance nonlinear vibration reduction system

Xinxi Xu,Meng Yang,Nan Jia,Deguang Duan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

Our aim was to improve the performance of tracked ambulance nonlinear vibration reduction system by structure optimization design. The structure optimization focuses on the stretcher base. Two structure optimization schemes are proposed based on the mechanism of Dynamic vibration absorber (DVA): Linear and nonlinear structure. The linear structure optimization scheme is finally adopted by comparison of the two schemes under random vibration, and the performance of linear scheme is also verified under shock vibration. Then the global sensitivity analysis method is applied to calculate the parameter sensitivity of nonlinear vibration reduction system. Finally, the Nondominated sorting genetic algorithm II (NSGA-II) is used to optimize the performance of the nonlinear vibration reduction system. It shows that the vibration energy of the supine human body on a stretcher is reduced after above studies, which proves the validity and feasibility of the structure optimization schemes proposed and the optimization studies applied in this paper.

Strongly nonlinear free vibration of four edges simply supported stiffened plates with geometric imperfections

Zhaoting Chen,Ronghui Wang,Li Cheng,Chunguang Dong 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.8

This article investigated the strongly nonlinear free vibration of four edges simply supported stiffened plates with geometric imperfections. The von Karman nonlinear strain-displacement relationships are applied. The nonlinear vibration of stiffened plate is reduced to a one-degree-of-freedom nonlinear system by assuming mode shapes. The Multiple scales Lindstedt-Poincare method (MSLP) and Modified Lindstedt-Poincare method (MLP) are used to solve the governing equations of vibration. Numerical examples for stiffened plates with different initial geometric imperfections are presented in order to discuss the influences to the strongly nonlinear free vibration of the stiffened plate. The results showed that: the frequency ratio reduced as the initial geometric imperfections of plate increased, which showed that the increase of the initial geometric imperfections of plate can lead to the decrease of nonlinear effect; by comparing the results calculated by MSLP method, using MS method to study strongly nonlinear vibration can lead to serious mistakes.

Nonlinear bending and free vibration analyses of metal-ceramic functionally graded plates by 2-D natural element method

조진래 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.12

Metal-ceramic functionally graded materials (FGMs) have attracted much attention in the recent years thanks to their excellent properties. Accordingly the intensive studies have focused on FGMs to investigate their thermo-mechanical behaviors. However, most of studies were restricted to the linear behavior with the assumption of small strain and small amplitude. Thus, the nonlinear deformation theory is prerequisite for the problems characterized by large deflection and large amplitude. In this context, this study intends to develop a nonlinear numerical method for solving the large deflection bending and free vibration problems. The proposed method is developed in the framework of 2-D natural element method (NEM) by adopting the von Kármán type nonlinearity and the (1, 1, 0) hierarchical model. A load incremental Newton-Raphson iterative equation system is derived for nonlinear bending problems, and a three-step direct iterative scheme is proposed to solve the nonlinear free vibration. The reliability of the proposed numerical method is verified by comparing with the reference methods. And, the nonlinear characteristics of bending deformation and free vibration of metalceramic FG plates are investigated by the proposed method.

Large amplitude free vibration analysis of laminated composite spherical shells embedded with piezoelectric layers

Subrata K. Panda,Vijay K. Singh 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.5

Numerical analysis of large amplitude free vibration behaviour of laminated composite spherical shell panel embedded with the piezoelectric layer is presented in this article. For the investigation purpose, a general nonlinear mathematical model has been developed using higher order shear deformation mid-plane kinematics and Green-Lagrange nonlinearity. In addition, all the nonlinear higher order terms are included in the present mathematical model to achieve any general case. The nonlinear governing equation of freely vibrated shell panel is obtained using Hamilton\'s principle and discretised using isoparametric finite element steps. The desired nonlinear solutions are computed numerically through a direct iterative method. The validity of present nonlinear model has been checked by comparing the responses to those available published literature. In order to examine the efficacy and applicability of the present developed model, few numerical examples are solved for different geometrical parameters (fibre orientation, thickness ratio, aspect ratio, curvature ratio, support conditions and amplitude ratio) with and/or without piezo embedded layers and discussed in details.

Vibration of sandwich plates considering elastic foundation, temperature change and FGM faces

Behzad Mohammadzadeh,Eunsoo Choi,Dongkyun Kim 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.5

This study presents a comprehensive nonlinear dynamic approach to investigate the linear and nonlinear vibration of sandwich plates fabricated from functionally graded materials (FGMs) resting on an elastic foundation. Higher-order shear deformation theory and Hamilton’s principle are employed to obtain governing equations. The Runge–Kutta method is employed together with the commercially available mathematical software MAPLE 14 to solve the set of nonlinear dynamic governing equations. Method validity is evaluated by comparing the results of this study and those of previous research. Good agreement is achieved. The effects of temperature change on frequencies are investigated considering various temperatures and various volume fraction index values, N. As the temperature increased, the plate frequency decreased, whereas with increasing N, the plate frequency increased. The effects of the side-to-thickness ratio, c/h, on natural frequencies were investigated. With increasing c/h, the frequencies increased nonlinearly. The effects of foundation stiffness on nonlinear vibration of the sandwich plate were also studied. Backbone curves presenting the variation of maximum displacement with respect to plate frequency are presented to provide insight into the nonlinear vibration and dynamic behavior of FGM sandwich plates.

Large amplitude free torsional vibration analysis of size-dependent circular nanobars using elliptic functions

Reza Nazemnezhad,Mohaddese Rabiei,Pouyan Shafa’at,Mehdi Eshaghi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.4

This paper concerns with free torsional vibration analysis of size dependent circular nanobars with von kármán type nonlinearity. Although review of the literature suggests several studies employing nonlocal elasticity theory to investigate linear torsional behavior, linear/nonlinear transverse vibration and buckling of the nanoscale structures, so far, no study on the nonlinear torsional behavior of the nanobars, considering the size effect, has been reported. This study employs nonlocal elasticity theory along with a variational approach to derive nonlinear equation of motion of the nanobar. Then, the nonlinear equation is solved using the elliptic functions to extract the natural frequencies of the structure under fixed-fixed and fixed-free end conditions. Finally, the natural frequencies of the nanobar under different nanobar lengths, diameters, nonlocal parameters, and amplitudes of vibration are reported to illustrate the effect of these parameters on the vibration characteristics of the nanobars. In addition, the phase plane diagrams of the nanobar for various cases are reported.

Computational analysis of the nonlinear vibrational behavior of perforated plates with initial imperfection using NURBS-based isogeometric approach

VeisiAra Abdollah,Mohammad-Sedighi Hamid,Reza Arash 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.5

In this article, an isogeometric analysis through NURBS basis functions is presented to study the nonlinear vibrational behavior of perforated plates with initial imperfection. In this regard, the governing equations of plate dynamics, as well as the displacement–strain relations, are derived using the Mindlin–Reissner plate theory by considering von Karman nonlinearity. The geometry of the structure is formed by selecting the order of NURBS basis functions and the number of control points according to the physics of the problem. Since similar basis functions are utilized to estimate the accurate geometry and displacement field of the domain, the order of the basic functions and the number of control points are optimized for the proper approximation of the unknown field variables. By utilizing the energy approach and Hamilton principle and discretizing the equations of motion, the vibrational response of the perforated imperfect plate is extracted through an eigenvalue problem. The results of linear vibrations, geometrically nonlinear vibrations, and nonlinear vibrations of imperfect plates are separately validated by considering the previously reported findings, which shows a satisfactory agreement. Thereafter, a coefficient of the first mode shape is considered as the initial imperfection and the vibrational analysis is reexamined. Furthermore, the nonlinear vibrations of the perforated plate with initial imperfection are analysed using an iterative approach. The effects of the perforated hole, initial imperfection, and geometric nonlinearity are also addressed and discussed.

함정 추진축계 기동, 정지 시 발생하는 스틱-슬립 비선형 진동 연구

한형석(Hyungsuk Han),전수홍(Soohong Jeon),김용훈(Yonghoon Kim),이가향(Gahyang Lee) 한국소음진동공학회 2023 한국소음진동공학회 논문집 Vol.33 No.3

Nonlinear vibration problems caused by the stick-slip friction between the water lubricating bearing and shaft in naval applications occur frequently. When the stick-slip nonlinear vibration occurs in a propulsion shaft, noise and vibration in the ship structure, as well as the shaft system are generated irregularly with high amplitude. Because stick-slip nonlinear vibrations occur usually at low speeds, they should be remedied to maintain the acoustic stealth performance of the naval vessel when conducting anti-submarine operations. In addition, increased bearing wear can be experienced when stick-slip nonlinear vibrations persist. In this study, the abnormal vibration and noise occurring in a naval vessel is described when the shaft is starting and stopping, and it is investigated considering the general stick-slip nonlinear vibration characteristics. Using a 2 D.O.F numerical model for the shaft and bearing, the stick-slip mechanism is described. Accordingly, it is experimentally verified that the abnormal vibration and noise occurring in a naval vessel are caused by the stick-slip vibrations.