A Simplified Finite Element for Added Mass and Inertial Coupling in Arrays of Cylinders

1985 ◽  
Vol 107 (2) ◽  
pp. 118-125 ◽  
Author(s):  
R. E. Harris ◽  
M. A. Dokainish ◽  
D. S. Weaver
Keyword(s):  
Finite Element ◽  
Time Integration ◽  
Element Model ◽  
Added Mass ◽  
Cylindrical Structures ◽  
Beam Elements ◽  
Inertial Coupling ◽  
Fundamental Frequencies ◽  
Tube Bundles ◽  
Primary Advantage

A simplified finite element has been developed for modeling the added mass and inertial coupling arising when clusters of cylinders vibrate in a quiescent fluid. The element, which is based on two-dimensional potential flow theory, directly couples two adjacent beam elements representing portions of the adjacent cylindrical structures. The primary advantage of this approach over existing methods is that it does not require the discretization of the surrounding fluid and, therefore, is computationally much more efficient. The fundamental frequencies of tube bundles of various pitch ratios have been predicted using this method and compared with experimental data. Generally, the agreement is good, especially for the bandwidth of fluid coupled natural frequencies. The transient response of tube bundles is also examined using time integration of the finite element model. The beating phenomenon and time decay characteristics exhibited by the experimental bundles under single-tube excitation are well predicted and valuable insights are gained into the measurement of damping in tube bundles.

Finite Element Modeling of Unidirectional Non-Crimp Fabric for Manufacturing of Composites with Embedded Cabling

2013 ◽  
Vol 554-557 ◽  
pp. 484-491 ◽  
Author(s):  
Alexander S. Petrov ◽  
James A. Sherwood ◽  
Konstantine A. Fetfatsidis ◽  
Cynthia J. Mitchell
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Explicit Finite Element ◽  
Shell Elements ◽  
Beam Elements ◽  
Hybrid Finite Element ◽  
International Benchmarking ◽  
Unidirectional Glass ◽  
Forming Simulations

A hybrid finite element discrete mesoscopic approach is used to model the forming of composite parts using a unidirectional glass prepreg non-crimp fabric (NCF). The tensile behavior of the fabric is represented using 1-D beam elements, and the shearing behavior is captured using 2-D shell elements into an ABAQUS/Explicit finite element model via a user-defined material subroutine. The forming of a hemisphere is simulated using a finite element model of the fabric, and the results are compared to a thermostamped part as a demonstration of the capabilities of the used methodology. Forming simulations using a double-dome geometry, which has been used in an international benchmarking program, were then performed with the validated finite element model to explore the ability of the unidirectional fabric to accommodate the presence of interlaminate cabling.

Modeling the Dynamic Frictional Contact of Tires Using an Explicit Finite Element Code

2005 ◽  
Author(s):  
Tamer M. Wasfy ◽  
Michael J. Leamy
Keyword(s):  
Finite Element ◽  
Frictional Contact ◽  
Time Integration ◽  
Friction Model ◽  
Finite Element Code ◽  
Normal Contact ◽  
Explicit Finite Element ◽  
Beam Elements ◽  
Coulomb Friction Model ◽  
Stiffness And Damping

A time-accurate explicit time-integration finite element code is used to simulate the dynamic response of tires including tire/pavement and tire/rim frictional contact. Eight-node brick elements, which do not exhibit locking or spurious modes, are used to model the tire’s rubber. Those elements enable use of one element through the thickness for modeling the tire. The bead, tread and ply are modeled using truss or beam elements along the tire circumference and meridian directions with appropriate stiffness and damping properties. The tire wheel is modeled as a rigid cylinder. Normal contact between the tire and the wheel and between the tire and the pavement is modeled using the penalty technique. Friction is modeled using an asperity-based approximate Coulomb friction model.

Methods for Reducing a Thermal Finite Element Model Including the Advection Network Contribution

2006 ◽  
Author(s):  
Daniele Botto ◽  
Stefano Zucca ◽  
Muzio M. Gola
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Real Time ◽  
Residual Life ◽  
Mathematical Formulation ◽  
Time Integration ◽  
Element Model ◽  
Computational Time ◽  
Fatigue Damage Accumulation ◽  
Secondary Air

The life monitoring concept needs on-line calculation to evaluate stresses and temperatures on aircraft engine components, in order to asses fatigue damage accumulation and residual life. Due to the amount of computational time required it is not possible for a full finite element model to operate in real time using the on-board CPU. Stresses and temperatures are then evaluated by using simplified algorithms. In the present work Guyan reduction and component mode synthesis have been applied to a thermal finite element model, including the cooling stream flow — the so called advection network — in order to reduce the size of the solving equation system. The appropriate mathematical formulation for the advection network reduction has been developed. Two reduction methods have been performed, discussed and subsequently applied to a thermal finite element model of a real low pressure turbine disk. The reduced system includes both the disk and the correlated fluid network model, simulating turbine secondary air system. The finite element model is axi-symmetric, with constant convective coefficients. Results of time integration for the reduced and the complete models have been compared. Results show that the proposed techniques gives models with a reduced number of degrees of freedom and at the same time good accuracy in temperature calculation. The reduced models are then suitable for real time computation.

Support-Condition Analyses of Rotating Beams Under Distributed Imbalance Loading

2011 ◽  
Author(s):  
Kai Jokinen ◽  
Erno Keskinen ◽  
Marko Jorkama ◽  
Wolfgang Seemann
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Cross Section ◽  
Cross Sections ◽  
Natural Frequencies ◽  
Element Model ◽  
Mode Shapes ◽  
Constant Cross Section ◽  
Support Condition ◽  
Beam Elements

In roll balancing the behaviour of the roll can be studied either experimentally with trial weights or, if the roll dimensions are known, analytically by forming a model of the roll to solve response to imbalance. Essential focus in roll balancing is to find the correct amount and placing for the balancing mass or masses. If this selection is done analytically the roll model used in calculations has significant effect to the balancing result. In this paper three different analytic methods are compared. In first method the mode shapes of the roll are defined piece wisely. The roll is divided in to five parts having different cross sections, two shafts, two roll ends and a shell tube of the roll. Two boundary conditions are found for both supports of the roll and four combining equations are written to the interfaces of different roll parts. Totally 20 equations are established to solve the natural frequencies and to form the mode shapes of the non-uniform roll. In second model the flexibility of shafts and the stiffness of the roll ends are added to the support stiffness as serial springs and the roll is modelled as a one flexibly supported beam having constant cross section. Finally the responses to imbalance of previous models are compared to finite element model using beam elements. Benefits and limitations of each three model are then discussed.

Numerical Simulation of Galloping for Iced Quad-Bundled Conductor

2014 ◽  
Vol 1025-1026 ◽  
pp. 955-958 ◽  
Author(s):  
Jun Jie Shi ◽  
Ya Nan Li ◽  
Li Qin
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Simulation Analysis ◽  
Time Integration ◽  
Vertical Vibration ◽  
Analysis Model ◽  
Element Analysis ◽  
Beam Elements ◽  
Time Integration Method ◽  
Wake Interference

The theoretical study of galloping can effectively promote anti-galloping techniques. Cable element is utilized to imitate the bundled conductor, and beam elements are used to simulated the spacers, established galloping finite element analysis model which can consider sub-conductors wake interference. The finite element equation was solved by time integration method and the calculation program was compiled by MATLAB. Through numerical simulation analysis, compared the dancing in the case of considering the effect of the sub-conductor wake and ignoring the effect of the sub-conductor wake. The results showed that considering the effect of the wake on aerodynamic loads has a greater vertical vibration amplitude. This method can provide reference for the study of prevention technology on dancing.

Coupled Blade Bending and Torsional Shaft Vibration in Turbomachinery

1993 ◽  
Author(s):  
U. Schaber ◽  
J. F. Mayer ◽  
H. Stetter
Keyword(s):  
Finite Element ◽  
Forced Vibration ◽  
Vibration Analysis ◽  
Element Model ◽  
Electrical Network ◽  
Design Parameters ◽  
Parameter Study ◽  
Mass Relation ◽  
Turbine Generator ◽  
Beam Elements

The forced vibration of turbomachinery blading induced by torsional vibration of the rotor shaft is investigated. Torsional shaft vibrations, caused for example by disturbances in the electrical network, jeopardize the long blades in low pressure stages of steam and gas turbine generator rotors. A simple finite element model consisting of beam elements is used to calculate free and forced vibration. A parameter study has been performed to show the influence of design parameters like mass relation and eigenfrequency relation of the uncoupled system parts. The vibration analysis of a large steam turbine generator rotor is presented.

Fundamental Frequencies of Turbine Blades With Geometry Mismatch in Fir-Tree Attachments

2006 ◽  
Vol 128 (3) ◽  
pp. 512-516 ◽  
Author(s):  
Fei Qin ◽  
Liming Chen ◽  
Ying Li ◽  
Xiaofeng Zhang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Significant Influence ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Element Model ◽  
Gap Size ◽  
Fundamental Frequencies ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Geometry mismatch in a turbine blade root, which arose in manufacturing process or caused by wearing out during service, leads to contact conditions changed in fir-tree attachments. As a result, shifting of the fundamental frequencies and redistribution of stress in the blade base possibly cause failure of the blade. A three-dimensional finite element model of a blade and its fir-tree attachments have been constructed and analyzed by taking into account contact nonlinearity in the attachments and large deformation effect of the blade. The geometry mismatch was introduced into the finite element model by defining gaps between two contact surfaces in the attachments. The influence of gap configuration and gap size on contact and fundamental frequencies was investigated. Results showed that gap configuration has significant influence on fundamental frequencies of the blade, especially on its bending modes. Gap size has little influence on the frequencies but significant influence on the contact status and thus changes stress distribution in the attachments. The results also suggest that modeling contact behavior in fir-tree attachments is necessary to obtain more accurate fundamental frequencies.

AN EFFICIENT FINITE ELEMENT MODEL FOR ANALYSIS OF SINGLE WALLED BORON NITRIDE NANOTUBE-BASED RESONANT NANOMECHANICAL SENSORS

NANO ◽  
2013 ◽  
Vol 08 (01) ◽  
pp. 1350011 ◽  
Author(s):  
MITESH B. PANCHAL ◽  
S. H. UPADHYAY ◽  
S. P. HARSHA
Keyword(s):  
Finite Element ◽  
Boron Nitride ◽  
Resonant Frequency ◽  
Continuum Mechanics ◽  
Element Model ◽  
Added Mass ◽  
Simulation Approach ◽  
Attached Mass ◽  
Resonant Frequency Shift ◽  
Nanomechanical Sensors

In this paper, the dynamics analysis of single walled boron nitride nanotubes (SWBNNT) as a resonant nanomechanical sensor by using the finite element method has been reported. Molecular structural mechanics-based finite element model (FEM) has been developed by using three-dimensional elastic beams and point masses, such that the proximity of the model to the actual atomic structure of nanotube is significantly retained. Different types of armchair layups of SWBNNTs are considered with cantilevered and bridged end constraints. By implementing the finite element simulation approach, the resonant frequency shift-based mass sensitivity analysis is performed for both types of end constraints for considered armchair form of the SWBNNTs with different aspect ratios. For both types of end constraint, continuum mechanics-based analytical formulations, considering effective wall thickness of nanotubes are used to validate the present FEM-based simulation approach. The intermediate landing position of the added mass is analyzed, considering variations in resonant frequency shifts of the different fundamental modes of vibrations for both types of end constraints. The FEM-based simulation results for both types of end constraints found in good agreement with the continuum mechanics-based analytical results for the aspect ratio of range of 9–15. The mass sensitivity limit of 10-1 zg is achieved for SWBNNT-based resonant nanomechanical sensors. The resonant frequency shift for higher-order fundamental vibrational modes become stable as the attached mass moves away from the fixed ends for particular magnitude of attached mass. The present finite element-based approach is found to be effectual in terms of dealing different atomic structures, boundary conditions and consideration of added mass to analyze the dynamic behavior of the SWBNNT-based resonant nanomechanical sensors.

scholarly journals Collapse Mechanism of Single-Layer Cylindrical Latticed Shell Under Severe Earthquake

2020 ◽  
Author(s):  
Haitao Zhou ◽  
Yigang Zhang ◽  
Feng Fu ◽  
Jinzhi Wu
Keyword(s):  
Finite Element ◽  
Single Layer ◽  
Element Model ◽  
Failure Criteria ◽  
Collapse Mechanism ◽  
Structural Members ◽  
Ground Acceleration ◽  
Beam Elements ◽  
Three Stages ◽  
Theory Of Damage

In this paper, the results of finite element analyses of a single-layer cylindrical latticed shell under severe earthquake is presented. A 3D Finite Element model using fiber beam elements were used to investigate the collapse mechanism of this type of shell. The failure criteria of structural members are simulated based on the theory of damage accumulation. Severe earthquake of peak ground acceleration (PGA) of 500 gal was applied to the shell. The stress and defeomation of the shell were studied in detail. A three-stages collapse mechanism “double-diagonal -members-failure-belt” of this type of structure was discovered. Based on the analysis results, the measures to mitigate collapse of this type of structure is recomanded.

scholarly journals Application of Finite Element Method for Analysis of Nanostructures

2017 ◽  
Vol 11 (2) ◽  
pp. 116-120 ◽  
Author(s):  
Jozef Bocko ◽  
Pavol Lengvarský
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Element Model ◽  
Geometrical Parameters ◽  
The Finite Element Method ◽  
Beam Elements ◽  
Stiffness Properties ◽  
Force Displacement ◽  
The Finite Element Model ◽  
Element Method

AbstractThe paper deals with application of the finite element method in modelling and simulation of nanostructures. The finite element model is based on beam elements with stiffness properties gained from the quantum mechanics and nonlinear spring elements with force-displacement relation are gained from Morse potential. Several basic mechanical properties of structures are computed by homogenization of nanostructure, e.g. Young's modulus, Poisson's ratio. The problems connecting with geometrical parameters of nanostructures are considered and their influences to resulting homogenized quantities are mentioned.

Sign in / Sign up

Export Citation Format

Share Document