scholarly journals A Refinement-by-Superposition Approach to Fully Anisotropic hp-Refinement for Improved Efficiency in CEM

2021 ◽  
Author(s):  
Jeremiah Corrado ◽  
Jake Harmon ◽  
Branislav Notaros
Keyword(s):  
Degrees Of Freedom ◽  
Industrial Applications ◽  
Test Case ◽  
Mesh Adaptivity ◽  
Singular Behavior ◽  
Anisotropic Mesh ◽  
Great Ease ◽  
Continuous Galerkin ◽  
Galerkin Formulation ◽  
Theoretical Considerations

We present an application of fully anisotropic hp-adaptivity over quadrilateral meshes for H(curl)-conforming discretizations in Computational Electromagnetics (CEM). Traditionally, anisotropic h-adaptivity has been difficult to implement under the constraints of the Continuous Galerkin Formulation; however, Refinement-by-Superposition (RBS) facilitates anisotropic mesh adaptivity with great ease. We present a general discussion of the theoretical considerations involved with implementing fully anisotropic hp-refinement, as well as an in-depth discussion of the practical considerations for 2-D FEM. Moreover, to demonstrate the benefits of both anisotropic h- and p-refinement, we study the 2-D Maxwell eigenvalue problem as a test case. The numerical results indicate that fully anisotropic refinement can provide significant gains in efficiency, even in the presence of singular behavior, substantially reducing the number of degrees of freedom required for the same accuracy with isotropic hp-refinement. This serves to bolster the relevance of RBS and full hp-adaptivity to a wide array of academic and industrial applications in CEM<br>

scholarly journals A Refinement-by-Superposition Approach to Fully Anisotropic hp-Refinement for Improved Efficiency in CEM

2021 ◽  
Author(s):  
Jeremiah Corrado ◽  
Jake Harmon ◽  
Branislav Notaros
Keyword(s):  
Degrees Of Freedom ◽  
Industrial Applications ◽  
Test Case ◽  
Mesh Adaptivity ◽  
Singular Behavior ◽  
Anisotropic Mesh ◽  
Great Ease ◽  
Continuous Galerkin ◽  
Galerkin Formulation ◽  
Theoretical Considerations

We present an application of fully anisotropic hp-adaptivity over quadrilateral meshes for H(curl)-conforming discretizations in Computational Electromagnetics (CEM). Traditionally, anisotropic h-adaptivity has been difficult to implement under the constraints of the Continuous Galerkin Formulation; however, Refinement-by-Superposition (RBS) facilitates anisotropic mesh adaptivity with great ease. We present a general discussion of the theoretical considerations involved with implementing fully anisotropic hp-refinement, as well as an in-depth discussion of the practical considerations for 2-D FEM. Moreover, to demonstrate the benefits of both anisotropic h- and p-refinement, we study the 2-D Maxwell eigenvalue problem as a test case. The numerical results indicate that fully anisotropic refinement can provide significant gains in efficiency, even in the presence of singular behavior, substantially reducing the number of degrees of freedom required for the same accuracy with isotropic hp-refinement. This serves to bolster the relevance of RBS and full hp-adaptivity to a wide array of academic and industrial applications in CEM<br>

Updating of Finite Element Models Based on a Double Condensation Procedure Using Frequency Response Functions Data

1995 ◽  
Author(s):  
Rémi Berriet ◽  
René Fillod ◽  
Noureddine Bouhaddi
Keyword(s):  
Frequency Response ◽  
Degrees Of Freedom ◽  
Noise Pollution ◽  
Test Case ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Modal Damping ◽  
Applied Forces ◽  
Definition Of

Abstract In order to take into account information from test data, not only at the resonances, but also in the other parts of the measured frequency spectrum, it is of interest to use directly measured Frequency Response Functions (FRF) instead of modal data. We also avoid by this way an experimental modal analysis. In return we have to introduce damping terms into the analytical model, we have to weight the FRF data in a systematic manner and to compute simultaneously a large amount of data. The presented procedure analyses overall these three aspects: definition of modal damping parameters, definition of weighted FRF data and condensation of the problem. This last notion is particularly pointed out. The condensation is performed in two steps : a static condensation of the model on the degrees of freedom corresponding to the location of the sensors, and a simultaneous condensation of experimental and analytical FRF data by a common transformation matrix. The first applications are performed on a simulated test case with large stiffness, mass and modal damping perturbations introduced in the initial model as well as strong noise pollution of measured responses and applied forces.

scholarly journals Skew Rolling of Rods from Scrap Rail Heads

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2970 ◽  
Author(s):  
Tomczak ◽  
Pater ◽  
Bulzak
Keyword(s):  
Experimental Tests ◽  
Rolling Process ◽  
Industrial Applications ◽  
Experimental Investigations ◽  
Longitudinal Rolling ◽  
Rolling Mills ◽  
Second Stage ◽  
New Process ◽  
Skew Rolling ◽  
Theoretical Considerations

This paper presents the results of theoretical and experimental investigations of a new process of rolling rods from scrap rail heads. First, the industrial applications of scrap railway rails and methods of their recycling are discussed, and then the concept of two-stage rolling of rods from heads cut off from scrap rails is proposed. In the first stage of the process, a rail head preform was rolled in a hexagonal pass of a longitudinal rolling mill. Then in the second stage, the hexagonal bar was skew rolled into a rod in a helical roll pass. Theoretical considerations were based on finite element numerical modelling. The rolling process was simulated under 3D deformation using Forge NxT v.1.1 software developed by Transvalor Company. Calculations were carried out to determine the material flow kinematics, strength, and thermal parameters of the process and to identify the phenomena that might constrain its implementation. The numerical results were verified in experimental tests, during which preforms and rods were formed from scrap rail heads. The tests were conducted in longitudinal and skew rolling mills. The results indicate that rods can be effectively formed from scrap rail heads in just two steps. Rods obtained using the proposed method can be used as full-featured, semifinished products for the manufacture of various types of machine parts.

scholarly journals Nuclear data adjustment using Bayesian inference, diagnostics for model fit and influence of model parameters

2020 ◽  
Vol 239 ◽  
pp. 13003
Author(s):  
D. Kumar ◽  
S. B. Alam ◽  
H. Sjöstrand ◽  
J.M. Palau ◽  
C. De Saint Jean
Keyword(s):  
Bayesian Inference ◽  
Degrees Of Freedom ◽  
Nuclear Data ◽  
Information Criteria ◽  
Least Square ◽  
Model Fit ◽  
Adjustment Process ◽  
Model Parameters ◽  
Test Case ◽  
Bayesian Approximation

The mathematical models used for nuclear data evaluations contain a large number of theoretical parameters that are usually uncertain. These parameters can be calibrated (or improved) by the information collected from integral/differential experiments. The Bayesian inference technique is used to utilize measurements for data assimilation. The Bayesian approximation is based on the least-square or Monte-Carlo approaches. In this process, the model parameters are optimized. In the adjustment process, it is essential to include the analysis related to the influence of model parameters on the adjusted data. In this work, some statistical indicators such as the concept of Cook’s distance; Akaike, Bayesian and deviance information criteria; effective degrees of freedom are developed within the CONRAD platform. Further, these indicators are applied to a test case of 155Gd to evaluate and compare the influence of resonance parameters.

Thermogasodynamic Analysis of the Segmented Annular Seal

2020 ◽  
Vol 143 (7) ◽  
Author(s):  
Samia Dahite ◽  
Mihai Arghir
Keyword(s):  
Parametric Study ◽  
Thermal Effects ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Leading Edge ◽  
Test Case ◽  
Isothermal Model ◽  
Pocket Depth ◽  
Annular Seal ◽  
Three Degrees Of Freedom

Abstract The present work deals with the thermogasodynamic analysis of the segmented annular seal provided with Rayleigh pockets. The paper is a continuation of the work presented Arghir, M., and Mariot, A. (2017, “Theoretical Analysis of the Static Characteristics of the Carbon Segmented Seal,” ASME J. Tribol., 139(6), p. 062202.) where an isothermal model of the segmented annular seal was first presented. Each segment had three degrees-of-freedom, and its static position was obtained by solving the nonlinear equations of equilibrium. Thermal effects are now introduced by considering a simplified form of the energy equation in the thin gas film coupled with the three dimensional heat transfer in a segment of the seal and in the rotor. An efficient numerical algorithm is developed. A parametric study was performed for a segmented annular seal with pockets taken from the literature and operating with air. First, a test case proved the necessity of considering three degrees-of-freedom for the segment and not only its radial displacement. The parametric study was then performed for two different pocket depths, two pressure differences, and different rotation speeds. The results showed a non-uniform heating with larger temperatures at the leading edge of the segment where the minimal film thickness occurs. Heating is proportional to the pocket depth that lowers the lift force of the segment and to the pressure difference that closes the seal.

Range of Variability in the Dynamics of Semi-Cylindrical Friction Dampers for Turbine Blades

2008 ◽  
Author(s):  
Stefano Zucca ◽  
Daniele Botto ◽  
Muzio M. Gola
Keyword(s):  
Degrees Of Freedom ◽  
Turbine Blades ◽  
Numerical Test ◽  
Forced Response ◽  
Numerical Code ◽  
Test Case ◽  
Force Coefficient ◽  
System A ◽  
Flat Side ◽  
Fatigue Failures

Under-platform dampers are used to reduce resonant stresses in turbine blades to avoid high cycle fatigue failures. In this paper a model of semi-cylindrical under-platform damper (i.e. with one flat side and one curved side) for turbine blades is described. The damper kinematics is characterized by three degrees of freedom (DOFs): in-plane translations and rotation. Static normal loads acting on the damper sides are computed using the three static balance equations of the damper. Non-uniqueness of normal pre-loads acting on the damper sides is highlighted. Implementation of the model in a numerical code for the forced response calculation of turbine blades with under-platform dampers shows that non-uniqueness of normal pre-loads leads to non-uniqueness of the forced response of the system. A numerical test case is presented to show the capabilities of the model and to analyze the effect of the main system parameters (damper mass, excitation force, coefficient of friction and damper rotation) on the damper behavior and on the system dynamics.

scholarly journals Rapid estimation of notch stress intensity factors in 3D large-scale welded structures using the peak stress method

2018 ◽  
Vol 165 ◽  
pp. 17004 ◽  
Author(s):  
Alberto Campagnolo ◽  
Giovanni Meneghetti
Keyword(s):  
Stress Intensity ◽  
High Performance ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Peak Stress ◽  
Industrial Applications ◽  
Mode I ◽  
Present Contribution ◽  
Notch Stress ◽  
Welded Structure

The Peak Stress Method (PSM) is an engineering, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which takes advantage of the singular linear elastic peak stresses from FE analyses with coarse meshes. Originally, the PSM was calibrated to rapidly estimate the NSIFs by using 3D, eight-node brick elements, taking advantage of the submodeling technique. 3D modelling of large-scale structures is increasingly adopted in industrial applications, thanks to the growing spread of high-performance computing (HPC). Based on this trend, the application of PSM by means of 3D models should possibly be even more speeded up. To do this, in the present contribution the PSM has been calibrated under mode I, II and III loadings by using ten-node tetra elements, which are able to directly discretize complex 3D geometries without the need for submodels. The calibration of the PSM has been carried out by analysing several 3D mode I, II and III problems. Afterwards, an applicative example has been considered, which is relevant to a large-scale steel welded structure, having overall size on the order of meters. Two 3D FE models, having global size of tetra elements equal to 5 and 1.66 mm, have been solved by taking advantage of HPC, being the global number of degrees of freedom equal to 10 and 140 millions, respectively. The NSIFs values estimated at the toe and root sides according to the PSM have been compared with those calculated by adopting a shell-to-solid technique.

scholarly journals Component Mode Synthesis Using Undeformed Interface Coupling Modes to Connect Soft and Stiff Substructures

2013 ◽  
Vol 20 (1) ◽  
pp. 157-170 ◽  
Author(s):  
Eskil Lindberg ◽  
Nils-Erik Hörlin ◽  
Peter Göransson
Keyword(s):  
Degrees Of Freedom ◽  
Component Mode Synthesis ◽  
Vehicle Suspension ◽  
Synthesis Methods ◽  
Test Case ◽  
Rotation Axes ◽  
Acoustic Modelling ◽  
Stiffness Properties ◽  
Rubber Bushing ◽  
Vehicle Suspension System

Classical component mode synthesis methods for reduction are usually limited by the size and compatibility of the coupling interfaces. A component mode synthesis approach with constrained coupling interfaces is presented for vibro-acoustic modelling. The coupling interfaces are constrained to six displacement degrees of freedom. These degrees of freedom represent rigid interface translations and rotations respectively, retaining an undeformed interface shape. This formulation is proposed for structures with coupling between softer and stiffer substructures in which the displacement is chiefly governed by the stiffer substructure. Such may be the case for the rubber-bushing/linking arm assembly in a vehicle suspension system. The presented approach has the potential to significantly reduce the modelling size of such structures, compared with classical component mode synthesis which would be limited by the modelling size of the interfaces. The approach also eliminates problems of nonconforming meshes in the interfaces since only translation directions, rotation axes and the rotation point need to be common for the coupled substructures. Simulation results show that the approach can be used for modelling of systems that resemble a vehicle suspension. It is shown for a test case that adequate engineering accuracy can be achieved when the stiffness properties of the connecting parts are within the expected range of rubber connected to steel.

scholarly journals The Development of a Hybrid Underwater Micro Biped Robot

2006 ◽  
Vol 3 (3) ◽  
pp. 143-150 ◽  
Author(s):  
S. Guo ◽  
Y. Okuda ◽  
W. Zhang ◽  
X. Ye ◽  
K. Asaka
Keyword(s):  
Degrees Of Freedom ◽  
Biped Robot ◽  
Input Voltage ◽  
Industrial Applications ◽  
Structure And Motion ◽  
Miniature Device ◽  
Micro Robot ◽  
Voltage Frequency ◽  
Ion Conducting ◽  
Ion Conducting Polymer

There has been a great demand, in the medical field and in industrial applications, for a novel micro biped robot with multiple degrees of freedom that can swim smoothly in water or in aqueous medium. The fish-like micro-robot studied is a type of miniature device that is installed with sensing and actuating elements. This article describes the new structure and motion mechanism of a hybrid type of underwater micro-robot using an ion-conducting polymer film (ICPF) actuator, and discusses the swimming and floating characteristics of the micro-robot in water, measured by changing the voltage frequency and the amplitude of the input voltage. Results indicate that the swimming speed of the proposed underwater micro-robot can be controlled by changing the frequency of the input voltage, and the direction (upward or downward) can be manipulated by changing the frequency of the electric current applied and the amplitude of the voltage.

Algorithmic path planning of static robots in three dimensions using configuration space metrics

Robotica ◽  
2010 ◽  
Vol 29 (2) ◽  
pp. 295-315 ◽  
Author(s):  
Debanik Roy
Keyword(s):  
Path Planning ◽  
Configuration Space ◽  
Heuristic Algorithm ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Three Dimensions ◽  
Task Space ◽  
Articulated Robot

SUMMARYCollision-free path planning for static robots is a demanding manifold of contemporary robotics research, vastly due to the growing industrial applications. In this paper, a novel ‘visibility map’-based heuristic algorithm is used to generate near-optimal safe path for a three-dimensional congested robot workspace. The final path is obtainable in terms of joint configurations, by considering the Configuration Space of the task space. The developed algorithm has been verified initially by considering representative 2D workspaces, cluttered with different obstacles with regular geometries and then after with the spatial endeavour. A case study reveals the effectiveness of the developed modules of the configuration space mapping, pertaining to a five degrees-of-freedom low payload articulated robot.

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