scholarly journals Modal testing and modelling the dynamic characteristics of a plate with bolted joints

2021 ◽  
Vol 15 (4) ◽  
pp. 8555-8564
Author(s):  
A.R. Bahari ◽  
M. A. Yunus ◽  
M.N. Abdul Rani ◽  
A.A. Prakasam
Keyword(s):  
Thin Plate ◽  
Dynamic Characteristics ◽  
Degrees Of Freedom ◽  
Normal Modes ◽  
Bolted Joints ◽  
Modal Testing ◽  
Mode Shapes ◽  
Fe Model ◽  
Six Degrees Of Freedom ◽  
Alternative Approach

Modelling the dynamic characteristics of the bolted joints in a complex assembled structure with a high accuracy is very challenging due to the assumptions and uncertainties in the input data of the FE model. In this paper, the identification of the dynamic characteristics of the bolted joints structure using the CBUSH element connector is proposed. Modal testing and normal modes analysis are conducted on a thin plate assembled structure with bolted joints. In the simulation work, the CBUSH element connector is employed and the stiffness coefficient for six degrees of freedom is computed based on four flexibility formulae. The predicted natural frequencies and their corresponding mode shapes are compared against the results of the experimental work. A good agreement of the FE model is achieved by using the coefficient of stiffness as represented in the Swift flexibility formula. The study justifies that the dynamic characteristics of the bolt joints could be accurately modelled by using the CBUSH element connector. The obtained findings provided an alternative approach to modelling the dynamic characteristics of a thin plate assembled structure with bolted joints.

A Screw Theory-Based Semi-Analytical Approach for Elastodynamics of the Tricept Robot

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Chenglin Dong ◽  
Haitao Liu ◽  
Tian Huang ◽  
Derek G. Chetwynd
Keyword(s):  
Lower Order ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Analytical Approach ◽  
Screw Theory ◽  
Mode Shapes ◽  
Fe Model ◽  
Six Degrees Of Freedom ◽  
Static Condensation ◽  
Elastodynamic Modeling

Taking the well-known Tricept robot as an example, this paper presents a semi-analytical approach for elastodynamic modeling of five or six degrees of freedom (DOF) hybrid robots composed of a 3-DOF parallel mechanism plus a 2- or 3-DOF wrist. Drawing heavily on screw theory combined with structural dynamics, the kinetic and elastic potential energies of the parallel mechanism and of the wrist are formulated using the dual properties of twist/wrench systems and a static condensation technique. This results in a 9-DOF dynamic model that enables the lower-order dynamic behavior over the entire workspace to be estimated in a very efficient and accurate manner. The lower-order natural frequencies and mode shapes estimated by the proposed approach are shown to have very good agreement with those obtained by a full-order finite element (FE) model. It thus provides a very time-effective tool for optimal design within a virtual prototyping framework for hybrid robot-based machine tools.

A Regression Approach to Generate Aircraft Predictor Information

1977 ◽  
Vol 19 (6) ◽  
pp. 549-555 ◽  
Author(s):  
Paul D. Gallaher ◽  
Roger A. Hunt ◽  
Robert C. Williges
Keyword(s):  
Degrees Of Freedom ◽  
Fast Time ◽  
Control Input ◽  
Least Squares Regression ◽  
Time Model ◽  
Six Degrees Of Freedom ◽  
Advantages And Disadvantages ◽  
Alternative Approach ◽  
Regression Approach ◽  
Aircraft Motion

A contact analog aircraft display is described in which an airplane-like predictor symbol depicts future airplane position and orientation. The standard method for obtaining the predictor information is to use a complete, fast-time model of the controlled vehicle. An alternative approach is presented in this paper in which least-squares regression approximations for each of the six degrees of freedom of aircraft motion were calculated. Thirteen predictor variables representing changes in positions and rates of change of positions were selected as parameters for these prediction equations. The accuracy of the regression approach is evaluated both at various prediction times and at various control input durations. The advantages and disadvantages of such a regression procedure for generating predictor symbols are discussed.

Dynamic Characteristics of Plastic Plates With Bolted Joints

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Akira Saito ◽  
Hideyoshi Suzuki
Keyword(s):  
Dynamic Characteristics ◽  
Vibration Mode ◽  
Acrylonitrile Butadiene Styrene ◽  
Bolted Joints ◽  
Modal Testing ◽  
Analytical Models ◽  
Plate Motion ◽  
Tightening Torque ◽  
Modeling Strategy ◽  
Torque Values

Abstract This paper discusses the dynamic characteristics of plastic plates with bolted joints. The effects of tightening torque on the modal properties of the plates are investigated. Experimental and numerical modal analyses have been conducted on the plates made of acrylonitrile butadiene styrene (ABS), that are clamped by bolted joints. First, the effect of tightening torque on the vibration mode of the plates is investigated by experimental modal analyses. Modal testing has been conducted for various tightening torque values, and the relationships between the modal parameters and the tightening torques are discussed. Second, the effects of tightening torque on the vibration mode are studied by using analytical models for the bolted joints based on the finite element method (FEM). Based on the comparisons between the experimental and the numerical results, a modeling strategy for the boundary conditions between the plates is introduced and its validity is discussed. From both experimental and numerical studies, it is shown that the natural frequencies of the structures with bolted joints tend to converge to specific values as tightening torque increases. Moreover, it is also shown that when modeling the bolted plates by FEM, the inter-plate motion should be constrained by a boundary condition to properly suppress the out-of-phase motion of the plates.

Output-Only Modal Analysis of an Internal Unreachable Module Embedded in a Space Electronic Equipment

2012 ◽  
Author(s):  
Lassaad Ben Fekih ◽  
Georges Kouroussis ◽  
David Wattiaux ◽  
Olivier Verlinden ◽  
Christophe De Fruytier
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Transverse Direction ◽  
Mode Shapes ◽  
Fe Model ◽  
Fe Method ◽  
Numeric Model ◽  
Stiffness Matrices ◽  
Output Only

An approach is proposed to identify the modal properties of a subsystem made up of an arbitrary chosen inner module of embedded space equipment. An experimental modal analysis was carried out along the equipment transverse direction with references taken onto its outer housing. In parallel, a numerical model using the finite element (FE) method was developed to correlate with the measured results. A static Guyan reduction has led to a set of master degrees of freedom in which the experimental mode shapes were expanded. An updating technique consisting in minimizing the dynamic residual induced by the FE model and the measurements has been investigated. A last verification has consisted in solving the numeric model composed of the new mass and stiffness matrices obtained by means of a minimization of the error in the constitutive equation method.

Vibrations

2017 ◽  
pp. 44-93
Keyword(s):  
Degrees Of Freedom ◽  
Normal Modes ◽  
Mode Shapes ◽  
Continuous Systems ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Mdof Systems ◽  
Parametric Coupling ◽  
Bending Modes ◽  
Stability Concepts

Vibration concepts are reviewed. Single degree-of-freedom vibration (SDOF) are analyzed. Subsequently, the analysis is extended to two degrees-of-freedom (2DOF) systems and coupling in a 2DOF system. The analysis of parametric coupling is introduced. Two sections on energy flow and the modeling of damping follow. Normal modes and mode shapes for systems with multiple degrees-of-freedom (MDOF) will then be considered. By generalizing MDOF systems to continuous systems, we can analyze bending modes in plates. Experimental modal analysis is introduced to prepare the reader for later application of this technique to full-scale operational gates. The second section of this chapter reviews fundamental concepts of fluid-structure systems with resonance. The chapter concludes with a short discussion of stability concepts.

Effects of Inline Rotating Component on Piping System Dynamic Characteristics

2003 ◽  
Author(s):  
Zakaria N. Ibrahim
Keyword(s):  
Dynamic Characteristics ◽  
Degrees Of Freedom ◽  
Normal Modes ◽  
Degree Of Freedom ◽  
System Dynamic ◽  
Piping System ◽  
Problem Solution ◽  
Rotating Shaft ◽  
Eigen Value ◽  
Quick Assessment

Piping system dynamic characteristics are determined utilizing the classical Eigen-Value problem solution. Systems with integrated inline rotating components would experience some changes in these characteristics. The intensity of these changes depends on the relative magnitudes of their rotational momentums. Pseudo single degree of freedom ‘SDOF’, systems that include gyroscopic momentum of a rotating shaft are formulated and are subjected to seismic base excitations. The comparative responses of these SDOF are investigated. The gyroscopic inertia significantly alters their predicted seismic responses. For multi-degree of freedom system, simplified methodology is formulated to provide quick assessment of including the gyroscopic effects of the rotating components. The lumped parameters of the inline-rotating component within the piping system require the velocity degrees of freedom to be included in the analysis. This results in the non-classical Eigen-Value problem type of formulation. The latter is simplified utilizing the classical Eigen-Value solution conventionally termed as normal modes extraction. The normal modes synthesis reduces the number of degrees of freedom for the non-classical Eigen-Value problem to a manageable level. The concept of mode shape utilization coefficient ‘MSUC’, is introduced to provide quick assessment of the system. The gyroscopic inertia does not dominate the system dynamic characteristics. Low to moderate rotational momentums, typically installed by the industry, slightly affect the piping system dynamic characteristics. This justifies the industry practice of ignoring the rotational momentums within the piping systems routine analysis. It is also found that very high rotational momentums are artificially required to dramatically change the system dynamic characteristics.

Dynamic Characteristics Analysis of Simulator Six-DOF Platform

2014 ◽  
Vol 651-653 ◽  
pp. 716-719 ◽  
Author(s):  
Yong Qiu Liu ◽  
Ying Xin Zhai ◽  
Xiao Feng Liu
Keyword(s):  
Dynamic Characteristics ◽  
Degrees Of Freedom ◽  
Good Control ◽  
Control Effect ◽  
Motion Platform ◽  
Fuzzy Pid Control ◽  
Six Degrees Of Freedom ◽  
Characteristics Analysis ◽  
Six Dof ◽  
Six Degree Of Freedom

Six degrees of freedom motion platform is an important part of the flight simulator. To study the dynamic characteristics of the simulator, the paper carried a six degree of freedom motion platform dynamics analysis, and proposed fuzzy PID control strategy, and through the ADAMS software to establish a simulation model of six degrees of freedom motion platform, simulation results show that the use of strategy has good control effect for the simulator is designed to provide some reference.

Analysis of the Human Middle Ear Dynamics Through Multibody Modeling

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Diego Calero ◽  
Lucas Lobato ◽  
Stephan Paul ◽  
Júlio A. Cordioli
Keyword(s):  
Frequency Response ◽  
Middle Ear ◽  
Degrees Of Freedom ◽  
Flexible Structures ◽  
Rigid Body Dynamics ◽  
Mode Shapes ◽  
Velocity Versus ◽  
Strong Impact ◽  
Fe Model ◽  
Human Middle Ear

Abstract The dynamics of the human middle ear (ME) has been studied in the past using several computational and experimental approaches in order to observe the effect on hearing of different conditions, such as conductive disease, corrective surgery, or implantation of a middle ear prosthesis. Multibody (MB) models combine the analysis of flexible structures with rigid body dynamics, involving fewer degrees-of-freedom (DOF) than finite element (FE) models, but a more detailed description than traditional 1D lumped parameter (LP) models. This study describes the reduction of a reference FE model of the human middle ear to a MB model and compares the results obtained considering different levels of model simplification. All models are compared by means of the frequency response of the stapes velocity versus sound pressure at the tympanic membrane (TM), as well as the system natural frequencies and mode shapes. It can be seen that the flexibility of the ossicles has a limited impact on the system frequency response function (FRF) and modes, and the stiffness of the tendons and ligaments only plays a role when above certain levels. On the other hand, the restriction of the stapes footplate movement to a piston-like behavior can considerably affect the vibrational modes, while constraints to the incudomalleolar joint (IMJ) and incudostapedial joint (ISJ) can have a strong impact on the system FRF.

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