scholarly journals Development of a New Cracked Mindlin Plate Element

2011 ◽  
Vol 2011 ◽  
pp. 1-11
Author(s):  
Chengyin Liu ◽  
John DeWolf ◽  
Jeong-Ho Kim
Keyword(s):  
Degrees Of Freedom ◽  
Mass Matrix ◽  
Elastic Strain Energy ◽  
Mindlin Plate ◽  
Plate Element ◽  
Element Analysis ◽  
Flexibility Matrix ◽  
The Finite Element Analysis ◽  
Service Conditions ◽  
Corner Node

This work addresses the development of a new four-noded rectangular Mindlin plate bending element (MP4C) with a crack which consists of three degrees of freedom (DOF) at each corner node. The crack in the element is assumed to be not closed and nonpropagating. The crack affects the elastic strain energy and the flexibility matrix of the element, whereas the mass matrix remains unchanged. The complete element stiffness matrix is constructed as the inverse of the combined flexibility matrix of both noncracked and cracked elements. To evaluate the behavior of the proposed cracked Mindlin plate element, numerical examples are provided. They are based on developing user subroutines in ABAQUS. The finite element analysis results using the developed plate element are in excellent agreement with those reported in previous work. The cracked plate element developed in this paper provides a simple and robust approach to model the real service conditions in plate-like structures.

A two degrees of freedom comb capacitive-type accelerometer with low cross-axis sensitivity

2019 ◽  
Vol 13 (3) ◽  
pp. 5334-5346
Author(s):  
M. N. Nguyen ◽  
L. Q. Nguyen ◽  
H. M. Chu ◽  
H. N. Vu
Keyword(s):  
Degrees Of Freedom ◽  
Proof Mass ◽  
Vibration Modes ◽  
Electrode Structure ◽  
Element Analysis ◽  
Mechanical Coupling ◽  
Fully Differential ◽  
Mode Effects ◽  
The Finite Element Analysis ◽  
Cross Axis

In this paper, we report on a SOI-based comb capacitive-type accelerometer that senses acceleration in two lateral directions. The structure of the accelerometer was designed using a proof mass connected by four folded-beam springs, which are compliant to inertial displacement causing by attached acceleration in the two lateral directions. At the same time, the folded-beam springs enabled to suppress cross-talk causing by mechanical coupling from parasitic vibration modes. The differential capacitor sense structure was employed to eliminate common mode effects. The design of gap between comb fingers was also analyzed to find an optimally sensing comb electrode structure. The design of the accelerometer was carried out using the finite element analysis. The fabrication of the device was based on SOI-micromachining. The characteristics of the accelerometer have been investigated by a fully differential capacitive bridge interface using a sub-fF switched-capacitor integrator circuit. The sensitivities of the accelerometer in the two lateral directions were determined to be 6 and 5.5 fF/g, respectively. The cross-axis sensitivities of the accelerometer were less than 5%, which shows that the accelerometer can be used for measuring precisely acceleration in the two lateral directions. The accelerometer operates linearly in the range of investigated acceleration from 0 to 4g. The proposed accelerometer is expected for low-g applications.

Finite Element Quarter Vehicle Suspension Model under Periodic Bump and Sinusoidal Road Excitation

2018 ◽  
Vol 880 ◽  
pp. 163-170
Author(s):  
Ștefan Cristian Castravete ◽  
Gabriel Cătălin Marinescu ◽  
Nicolae Dumitru ◽  
Oana Victoria Oţăt
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Element Model ◽  
Finite Model ◽  
Vehicle Speed ◽  
Element Analysis ◽  
Car Suspension ◽  
The Finite Element Analysis ◽  
Road Excitation ◽  
Suspension Model

The paper studies the behavior of a quarter-car suspension model under periodic road excitation: sinusoidal and bump (trapezoidal shape) for a constant vehicle speed. A theoretical and a finite element model were developed. The theoretical model has two degrees of freedom and a modal and sinusoidal excitation was performed to compare with finite model analysis. The finite element analysis consists of three parts: preload, modal analysis and deterministic external excitation. The study consists of the analysis of forces, displacements and accelerations that are transmitted to the vehicle regarding their variation in time and frequency.

Workspace Comparison Between 3-PRR and 3-RPR Micro-Manipulator

2012 ◽  
Author(s):  
Yi Dong ◽  
Feng Gao ◽  
Yi Yue ◽  
Jin Feng
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Degrees Of Freedom ◽  
The Other ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Structural Differences ◽  
Micro Manipulator

This paper presents two compliant micro-manipulators with different structures. One uses 3-PRR mechanism while the other one adopts 3-RPR mechanism. Both of the two micro-manipulators have two translational degrees of freedom (DOF) and one rotational DOF. But the properties, such as workspace, of the two micro-manipulators are not the same. In this paper, the workspaces are studied and compared. First, the structural differences are presented. Then, the stiffness derivations of the two micro-manipulators are given and the workspaces are calculated considering the properties of piezoelectric (PZT) actuators. Finally the finite element analysis and prototype experiments are performed to validate the obtained results.

Design and Analysis of a Planar Piezo-Actuated Nanopositioner with Millimeter Scale Stroke

2016 ◽  
Vol 679 ◽  
pp. 143-148
Author(s):  
Hui Tang ◽  
Jian Gao ◽  
Xin Chen ◽  
Lan Yu Zhang ◽  
Zhao He Zeng
Keyword(s):  
Degrees Of Freedom ◽  
Cross Coupling ◽  
Optimal Designs ◽  
Fast Tool Servo ◽  
Precision Manufacturing ◽  
Element Analysis ◽  
Satisfactory Performance ◽  
The Finite Element Analysis ◽  
High Bandwidth ◽  
Promising Application

In recent years, Fast Tool Servo (FTS) mechanism in precision manufacturing equipment emerges as a promising application for the piezo-actuated flexible nanopositioner. A flexible nanopositioner with large stroke, high bandwidth, high precision and multi-Degrees-of-Freedom (multi-DOFs) is really desired for this application. In order to meet this requirement, a novel 2-DOF flexible nanopositioner consists of two pairs of differential lever displacement amplifiers (DLDA) is proposed in this paper first, also, kinetostatics modeling is conducted by using the Pseudo-Rigid Body (PRB) method. After a series of mechanism optimal designs, the performance of the designed nanopositioner is verified by using the Finite Element Analysis (FEA) method. A piezoelectric (PZT) actuator with 90 µm is selected in this simulation, the experimental results indicate that the mechanism workspace can achieve around 2.1×2.1 mm2, the bandwidth can reach up to around 136 Hz, while the cross-coupling is also kept with 1%. All the results consistently prove the proposed device possesses satisfactory performance for fulfilling the practical precision manufacturing tasks.

Stability of mirror chambers and mechanics: an example of the improvement of vibrational behaviour

2010 ◽  
Vol 1 (MEDSI-6) ◽  
Author(s):  
C. Ruget ◽  
L. Nikitina ◽  
J. Nicolas ◽  
J.C. Martinez ◽  
J. Juanhuix
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Degrees Of Freedom ◽  
High Stability ◽  
Element Analysis ◽  
Detailed Design ◽  
The Finite Element Analysis ◽  
Synchrotron Light ◽  
High Level ◽  
Low Emittance

ALBA synchrotron light facility includes a 3 GeV low-emittance storage ring capable of running in the top-up mode which will feed a number of beamlines. Xaloc and CIRCE are among these beamlines. These beamlines are equipped with mirrors which need high stability. There are a lot of mirror chambers in the market and we decided to improve one of them rather than developing a new one. For this purpose, the ALBA team organized a collaboration with a supplier of beamline components. ALBA did the conceptual design of the improvements, the Finite Element Analysis (FEA) optimization and the metrology tests. The supplier provided a detailed design and the production. The improvement was implemented on several mirror chambers including actuators from two to five degrees of freedom. At the beginning of the project, the hypothesis was an excitation coming from the ground lower than 1 µm for frequencies below 45 Hz and negligible above it. The strategy[0] in terms of dynamical stability was not to amplify the ground excitation below 45 Hz or around 50 Hz. That is, to increase the frequency of the system resonances above 45 Hz (excluding the range of about 50 Hz). As a result, we obtained a high level of stability for such mirror systems and we almost met the target value for the first mode of vibration.

scholarly journals Finite elements with continuous stress fields in calculation of folded prismatic thin-walled rods and shells

2018 ◽  
Vol 196 ◽  
pp. 01018
Author(s):  
Sergey Nazarenko ◽  
Nina Blokhina
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Degrees Of Freedom ◽  
High Efficiency ◽  
Stress Fields ◽  
Displacement Fields ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Shell Finite Element ◽  
Rectangular Shell

The article deals with methods of creating a rectangular wall-beam finite element with eight degrees of freedom per node and continuous stress fields along the boundaries. This effect is achieved by specifying displacement fields in the plane of the element in forms similar to those in finite elements of Bogner, Fox, and Schmitt plate. The article provides algebraic expressions for displacement forms; methods of forming reaction and stress matrices are also considered. Test calculations carried out with the help of “Computational mechanics” FEM complex have proved high efficiency of the finite element analysis performed. A rectangular shell finite element with twelve degrees of freedom per node was developed as a combination of membrane finite element and Bogner, Fox and Schmitt plate element.

Vibration and Sensitivity Analysis of a Beam With a Lumped Mass of Translational and Rotary Inertias

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
D. Wang
Keyword(s):  
Natural Frequency ◽  
Degrees Of Freedom ◽  
Free Vibration Analysis ◽  
Rotary Inertia ◽  
Closed Form Expression ◽  
Lumped Mass ◽  
Form Expression ◽  
Element Analysis ◽  
Discrete Method ◽  
The Finite Element Analysis

The free vibration analysis of a uniform beam carrying a lumped mass with the inclusion of both translational and rotary inertias are performed, and a closed-form expression of the frequency sensitivity with respect to the attachment location of the lumped mass is formulated using the discrete method upon the finite element analysis. By virtually introducing additional degrees of freedom at the mass-attached point, the first-order derivative of the natural frequency can be determined straightforwardly. Comparisons of numerical results from two typical examples show that the rotary inertia of a lumped mass may impose important effects on the natural frequency and its sensitivity. Neglecting the rotary inertia may lead to inaccurate or even erroneous solutions of the beam’s dynamics.

A New Procedure for Structural Fault Estimation Using a Prescribed Eigen-Structure

2015 ◽  
Vol 764-765 ◽  
pp. 1015-1019
Author(s):  
Kun Nan Chen ◽  
Wen Der Ueng ◽  
Yunn Lin Hwang
Keyword(s):  
Finite Element ◽  
Structural Damage ◽  
Degrees Of Freedom ◽  
Fault Estimation ◽  
Computationally Efficient ◽  
Element Analysis ◽  
Stiffness Reduction ◽  
Stiffness Matrices ◽  
The Finite Element Analysis ◽  
Incomplete Measurement

A new method using an incomplete measurement set to locate and identify structural damage is proposed. The method is iterative yet computationally efficient and requires no sensitivity calculations. Mass and stiffness matrices, established by finite element method, are partitioned and measured partial eigenvectors are expanded to full modes. Stiffness reduction coefficients for structural elements are defined and then solved by a nonnegative least-squares solution scheme. With much less measured degrees of freedom and even less measured modes than the finite element analysis degrees of freedom, the proposed approach can still identify the damaged locations and extent of the damage in a structure. The effectiveness of the method is demonstrated by solving a numerically simulated example on the GARTEUR SM-AG19 structure.

Design and Analysis of Flexible Continuum Robot Based on Origami and Mortise-Tenon Structure (FCRBOM)

2021 ◽  
Author(s):  
Yue Yu ◽  
Lifang Qiu ◽  
Decheng Wang ◽  
Jing Zou
Keyword(s):  
Degrees Of Freedom ◽  
High Capacity ◽  
Element Analysis ◽  
Compliance Matrix ◽  
The Finite Element Analysis ◽  
Continuum Robot ◽  
Dimensional Parameters ◽  
Compliance Matrix Method ◽  
The Impact ◽  
The Continuum

Abstract The continuum robot is a soft robot with infinite degrees of freedom. Origami has a high capacity for spatial deployment. This paper proposes a flexible continuum robot based on origami and mortise-tenon structure (FCRBOM). The robot consists of some flexible hinges based on origami and mortise-tenon structure (FHBOM). The design process of the FCRBOM is given. The compliance of the FCRBOM is analyzed by the compliance matrix method. The Finite element analysis (FEA) is used to simulate and analyze the FCRBOM, and the correctness of the theoretical analysis is verified. Then a spatial FCRBOM (SFCRBOM) is designed. The impact of key dimensional parameters on the flexibility of SFCRBOM is discussed. Finally, an SFCRBOM with higher flexibility is presented.

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