Physical Realization of Generic-Element Parameters in Model Updating

2002 ◽  
Vol 124 (4) ◽  
pp. 628-633 ◽  
Author(s):  
H. Ahmadian ◽  
J. E. Mottershead ◽  
M. I. Friswell
Keyword(s):  
Model Updating ◽  
Finite Element Models ◽  
Physical Realization ◽  
Governing Equations ◽  
Stiffness Matrices ◽  
Model Predictions ◽  
Physical Effects ◽  
Realization Process ◽  
Physical Phenomena ◽  
Selection Of

The selection of parameters is most important to successful updating of finite element models. When the parameters are chosen on the basis of engineering understanding the model predictions are brought into agreement with experimental observations, and the behavior of the structure, even when differently configured, can be determined with confidence. Physical phenomena may be misrepresented in the original model, or may be absent altogether. In any case the updated model should represent an improved physical understanding of the structure and not simply consist of unrepresentative numbers which happen to cause the results of the model to agree with particular test data. The present paper introduces a systematic approach for the selection and physical realization of updated terms. In the realization process, the discrete equilibrium equation formed by mass, and stiffness matrices is converted to a continuous form at each node. By comparing the resulting differential equation with governing equations known to represent physical phenomena, the updated terms and their physical effects can be recognized. The approach is demonstrated by an experimental example.

Selection of M-dwarfs using Gaia, WISE, and 2MASS

2019 ◽  
Vol 490 (3) ◽  
pp. 4107-4120
Author(s):  
J Bentley ◽  
C G Tinney ◽  
S Sharma ◽  
D Wright
Keyword(s):  
Absolute Magnitude ◽  
Contamination Rate ◽  
M Dwarfs ◽  
Sky Survey ◽  
Model Predictions ◽  
Galaxy Model ◽  
M Dwarf ◽  
Different Sources ◽  
Sources Of Contamination ◽  
Selection Of

ABSTRACT We present criteria for the selection of M-dwarfs down to G < 14.5 using all-sky survey data, with a view to identifying potential M-dwarfs, to be confirmed spectroscopically by the FunnelWeb survey. Two sets of criteria were developed. The first, based on absolute magnitude in the Gaia G passband, with MG > 7.7, selects 76,392 stars, with 81.0 per cent expected to be M-dwarfs at a completeness of >97 per cent. The second is based on colour and uses Gaia, WISE, and 2MASS all-sky photometry. This criteria identifies 94,479 candidate M-dwarfs, of which between 29.4 per cent and 47.3 per cent are expected to be true M-dwarfs, and which contains 99.6 per cent of expected M-dwarfs. Both criteria were developed using synthetic galaxy model predictions, and a previously spectroscopically classified set of M- and K-dwarfs, to evaluate both M-dwarf completeness and false-positive detections (i.e. the non-M-dwarf contamination rate). Both criteria used in combination demonstrate how each excludes different sources of contamination. We therefore developed a final set of criteria that combines absolute magnitude and colour selection to identify 74,091 stars. All these sets of criteria select numbers of objects feasible for confirmation via massively multiplexed spectroscopic surveys like FunnelWeb.

Validating and Updating Finite Element Models Using Experimental Measurements of Dynamics

1990 ◽  
Vol 204 (1) ◽  
pp. 45-50
Author(s):  
C F McCulloch ◽  
P Vanhonacker ◽  
E Dascotte
Keyword(s):  
Finite Element ◽  
Structural Dynamics ◽  
Model Updating ◽  
Measured Data ◽  
Physical Parameters ◽  
Experimental Measurements ◽  
Finite Element Models ◽  
Data Sets ◽  
Modal Data ◽  
Modelling Assumptions

A method is proposed for updating finite element models of structural dynamics using the results of experimental modal analysis, based on the sensitivities to changes in physical parameters. The method avoids many of the problems of incompatibility and inconsistency between the experimental and analytical modal data sets and enables the user to express confidence in measured data and modelling assumptions, allowing flexible but automated model updating.

Symmetric Model Correction of Mechanical Systems

1993 ◽  
Author(s):  
Marca Lam ◽  
Daniel J. Inman ◽  
Andreas Kress
Keyword(s):  
Analytical Model ◽  
Model Updating ◽  
Symmetric Model ◽  
Simple Method ◽  
Modal Data ◽  
Model Correction ◽  
Systems Model ◽  
Modal Damping ◽  
Stiffness Matrices ◽  
Damped Systems

Abstract This work examines the model updating problem for simple nonconservative proportionally damped systems. Model correction, also called model updating, refers to the practice of adjusting an analytical model until the model agrees with measured modal data. The specific case examined here assumes that natural frequencies and modal damping ratios are available from vibration tests and that the measured data disagrees in part with the modal data predicted by an analytical model. Most model correction schemes tend to produce updated damping and stiffness matrices which are asymmetric. The simple method presented here focuses on retaining the desired symmetry in the updated model.

Application of a FRF Based Model Updating Technique for the Validation of Finite Element Models of Components of the Automotive Industry

1995 ◽  
Author(s):  
Stefan Lammens ◽  
Marc Brughmans ◽  
Jan Leuridan ◽  
Ward Heylen ◽  
Paul Sas
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Automotive Industry ◽  
Stiffness Matrix ◽  
Model Updating ◽  
Dynamic Stiffness ◽  
Element Model ◽  
Model Parameters ◽  
Finite Element Models ◽  
Analytical Dynamic

Abstract This paper presents two applications of the RADSER model updating technique (Lammens et al. (1995) and Larsson (1992)). The RADSER technique updates finite element model parameters by solution of a linearised set of equations that optimise the Reduced Analytical Dynamic Stiffness matrix based on Experimental Receptances. The first application deals with the identification of the dynamic characteristics of rubber mounts. The second application validates a coarse finite element model of a subframe of a Volvo 480.

scholarly journals Unified theory of beam bending within flexoelectricity with including piezoelectricity

2020 ◽  
Vol 310 ◽  
pp. 00063
Author(s):  
Vladimir Sladek ◽  
Jan Sladek
Keyword(s):  
Shear Deformation ◽  
Deformation Theory ◽  
Shear Deformation Theory ◽  
Electric Polarization ◽  
Unified Theory ◽  
Key Factors ◽  
Governing Equations ◽  
Proper Selection ◽  
Beam Bending ◽  
Selection Of

The behaviour of small size dielectric elastic beams is described within higher-grade theory with including electric polarization. The coupling between strain gradients and polarization is incorporated into the constitutive laws in the form of flexoelectricity, while piezoelectricity is involve in the classical form. Both the governing equations and boundary conditions are derived using variational formulation for electro-elastic continuous media and deformation assumptions employed in three various beam bending theories such as the classical theory (Euler-Bernoulli theory), the 1st order shear deformation theory (Timoshenko theory) and 3rd order shear deformation theory. The unified formulation allows switching between theories with various bending assumptions by a proper selection of two key factors.

Comparison of Molecular Simulation and Pseudo-Rigid-Body Model Predictions for a Carbon Nanotube–Based Compliant Parallel-Guiding Mechanism

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Christopher M. DiBiasio ◽  
Martin L. Culpepper ◽  
Robert Panas ◽  
Larry L. Howell ◽  
Spencer P. Magleby
Keyword(s):  
Rigid Body ◽  
Molecular Simulation ◽  
Moment Of Inertia ◽  
Bulk Deformation ◽  
Body Model ◽  
Kinematic Behavior ◽  
Model Predictions ◽  
Rigid Body Model ◽  
Simulation Results ◽  
Selection Of

We report on the accuracy of the pseudo-rigid-body model (PRBM) in predicting the behavior of a nanoscale parallel-guiding mechanism (nPGM) that uses two single-walled (5,5) carbon nanotubes (CNTs) as the flexural guiding elements. The nPGM has two regions of behavior: region 1 is governed by the bulk deformation of the nanotubes, and region 2 is characterized by hingelike flexing of four “kinks” that occur due to buckling of the nanotube walls. PRBM parameters for (5,5) CNTs are proposed. Molecular simulation results of region 1 behavior match PRBM predictions of (1) kinematic behavior with less than 7.3% error and (2) elastomechanic behavior with less than 5.7% error. Although region 1 is of more interest because of its well-defined and stable nature, region 2 motion is also investigated. We show that the PRBM parameters are dependent on the selection of the effective tube thickness and moment of inertia, the lesson being that designers must take care to consider the thickness and moment of inertia values when deriving PRBM constants.

The Role of Conceptualization and Design in Product Realization

2011 ◽  
Author(s):  
Mohamed E. M. El-Sayed
Keyword(s):  
Product Development ◽  
Physical Realization ◽  
Development Cycle ◽  
Virtual Realities ◽  
Design And Manufacturing ◽  
Product Development Cycle ◽  
Realization Process ◽  
Product Realization ◽  
The Physical Realization

The term Product realization is usually used to describe the physical realization of a product in the product development cycle. Therefore, the term may or may not include conceptualization and design phases. Considering that product realization means bringing a product to reality, it is important to study the concept of reality to understand the role of conceptualization, design, and manufacturing in product realization. In this paper, the concept of reality is expanded to include the perceptual and virtual realities as integral parts of the product realization process. This paper discusses the three phases of realization and their interactions. It also addresses the key roles of conceptualization, design and manufacturability in the realization process. To illustrate the concepts, presented in the paper, some examples are included.

Control of Jets by Very Small Signals

2003 ◽  
Author(s):  
N. Ogawa
Keyword(s):  
Arc Discharge ◽  
Jet Flow ◽  
Flow Fields ◽  
Control Flow ◽  
Small Signal ◽  
Control Methods ◽  
Thin Cylinder ◽  
Impact Position ◽  
Physical Phenomena ◽  
Selection Of

It is very important that a very small signal can control flow fields for selection of various control methods. Author developed a method to control the jets by very small signal in process of investigating flow fields of turbulent opposed jets. That is to say, a very thin cylinder in the jet center can control an impact position and also turbulence in the jet center play an important role. Many methods are acceptable to produce the turbulence in the jet center. And we can select various physical phenomena for input to control the jet flow fields. Here I propose a method using an arc discharge to control the axisymmetric jets.

Computational Analysis of Fiber Dynamics in Human Nasal Cavity

2020 ◽  
Author(s):  
Jiawei Ma ◽  
Jiyuan Tu ◽  
Lin Tian ◽  
Goodarz Ahmadi
Keyword(s):  
Nasal Cavity ◽  
Transport Processes ◽  
Upper Respiratory Tract ◽  
Governing Equations ◽  
Aspect Ratios ◽  
Model Predictions ◽  
Fiber Dynamics ◽  
Upper Respiratory ◽  
Rotational Motions ◽  
Insight Into

Abstract Elongated particles, such as asbestos and mineral fibers, are considered severe inhalation hazards due to their ability to penetrate into the deep lung. Frequently the dynamic behavior of the fibrous particles is attributed to their unique needle-like geometry. Therefore, understanding the interactions of the inhaled elongated particles with the airflow environment is of great significance. In this study, the transport and deposition of elongated micro-fibers in a realistic human nasal cavity is investigated numerically. The motion of the micro-fiber is resolved by solving the system of equations governing its coupled translational and rotational motions. The governing equations included the drag, the hydrodynamic torques that were evaluated using the Jeffrey model. The influence of the shear lift force was also included in these simulations. The no-slip wall boundary condition for airflow in the airways was used. Since the surface of airways is covered with mucus, when a fiber touches the surface, it was assumed to be deposited with no rebound. The study allows a close look at the non-spherical particle-flow dynamics with respect to the translation, rotation, coupling, and how the rotation affects the particle’s macroscopic transport and deposition properties. A series of simulations for different microfiber diameters and aspect ratios were performed. The simulation results are compared with the existing experimental data, and earlier computational model predictions and good agreements were obtained. The present study also seeks to provide additional insight into the transport processes of microfibers in the upper respiratory tract.

Correlation of Power Cylinder Modeling to Empirical Measurements in a John Deere 6135H 13.5L I-6 Engine

2009 ◽  
Author(s):  
Max Maschewske ◽  
Erich Rabassa ◽  
Kimm Karrip ◽  
Greg Vander Veen ◽  
Randy Lunsford ◽  
...  
Keyword(s):  
Correlation Study ◽  
Oil Consumption ◽  
Power Cylinder ◽  
Development Cycle ◽  
Model Predictions ◽  
Correlation Parameters ◽  
Analytical Tools ◽  
Physical Phenomena ◽  
Land Pressure ◽  
Gas Pressures

Motivated by the need to achieve greater efficiency in the product development cycle, engine manufacturers in the heavy-duty industry are relying more and more on analytical tools to help resolve performance issues, minimize testing costs and reduce time to market. This is particularly the case in the area of power cylinder development, since the physical phenomena occurring within the cylinders are difficult to observe and quantify. However, analytical tools are useful only if they are able to accurately represent the physical systems that they are supposed to simulate. It therefore becomes critical to establish a correlation between model predictions and empirical measurements. To this end, a correlation study was initiated comparing power cylinder analytical modeling results to empirical measurements in a John Deere 6135H 13.5L I-6 engine. The engine test measurements that were carried out included cylinder pressure, piston land pressure, engine blowby, and lube oil consumption. The correlation parameters considered in the study included piston land gas pressures, power cylinder contribution to engine blowby, and lube oil consumption mechanisms.

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