scholarly journals Localization of Small Anomalies via the Orthogonality Sampling Method from Scattering Parameters

Electronics ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1119
Author(s):  
Seongje Chae ◽  
Chi Young Ahn ◽  
Won-Kwang Park
Keyword(s):  
Material Properties ◽  
Born Approximation ◽  
Sampling Method ◽  
Bessel Functions ◽  
Synthetic Data ◽  
Indicator Function ◽  
Hankel Function ◽  
Scattering Parameters ◽  
Antenna Configuration ◽  
Simulation Results

We investigate the application of the orthogonality sampling method (OSM) in microwave imaging for a fast localization of small anomalies from measured scattering parameters. For this purpose, we design an indicator function of OSM defined on a Lebesgue space to test the orthogonality relation between the Hankel function and the scattering parameters. This is based on an application of the Born approximation and the integral equation formula for scattering parameters in the presence of a small anomaly. We then prove that the indicator function consists of a combination of an infinite series of Bessel functions of integer order, an antenna configuration, and material properties. Simulation results with synthetic data are presented to show the feasibility and limitations of designed OSM.

scholarly journals Development of Elastoplastic-Damage Model of AlFeSi Phase for Aluminum Alloy 6061

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 954
Author(s):  
Hailong Wang ◽  
Wenping Deng ◽  
Tao Zhang ◽  
Jianhua Yao ◽  
Sujuan Wang
Keyword(s):  
Aluminum Alloy ◽  
Constitutive Model ◽  
Material Properties ◽  
Damage Model ◽  
Scratch Test ◽  
Aluminum Alloy 6061 ◽  
Ultra Precision ◽  
Simulation Results ◽  
Alloy 6061 ◽  
Elastoplastic Damage

Material properties affect the surface finishing in ultra-precision diamond cutting (UPDC), especially for aluminum alloy 6061 (Al6061) in which the cutting-induced temperature rise generates different types of precipitates on the machined surface. The precipitates generation not only changes the material properties but also induces imperfections on the generated surface, therefore increasing surface roughness for Al6061 in UPDC. To investigate precipitate effect so as to make a more precise control for the surface quality of the diamond turned Al6061, it is necessary to confirm the compositions and material properties of the precipitates. Previous studies have indicated that the major precipitate that induces scratch marks on the diamond turned Al6061 is an AlFeSi phase with the composition of Al86.1Fe8.3Si5.6. Therefore, in this paper, to study the material properties of the AlFeSi phase and its influences on ultra-precision machining of Al6061, an elastoplastic-damage model is proposed to build an elastoplastic constitutive model and a damage failure constitutive model of Al86.1Fe8.3Si5.6. By integrating finite element (FE) simulation and JMatPro, an efficient method is proposed to confirm the physical and thermophysical properties, temperature-phase transition characteristics, as well as the stress–strain curves of Al86.1Fe8.3Si5.6. Based on the developed elastoplastic-damage parameters of Al86.1Fe8.3Si5.6, FE simulations of the scratch test for Al86.1Fe8.3Si5.6 are conducted to verify the developed elastoplastic-damage model. Al86.1Fe8.3Si5.6 is prepared and scratch test experiments are carried out to compare with the simulation results, which indicated that, the simulation results agree well with those from scratch tests and the deviation of the scratch force in X-axis direction is less than 6.5%.

scholarly journals Cramér-Rao Bound Study of Multiple Scattering Effects in Target Separation Estimation

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Edwin A. Marengo ◽  
Paul Berestesky
Keyword(s):  
Multiple Scattering ◽  
Born Approximation ◽  
Single Scattering ◽  
Scattering Data ◽  
Approximation Model ◽  
Scattering Parameters ◽  
Helmholtz Operator ◽  
Scattering Effects ◽  
Cramer Rao Bound ◽  
Multiple Scattering Effects

The information about the distance of separation between two-point targets that is contained in scattering data is explored in the context of the scalar Helmholtz operator via the Fisher information and associated Cramér-Rao bound (CRB) relevant to unbiased target separation estimation. The CRB results are obtained for the exact multiple scattering model and, for reference, also for the single scattering or Born approximation model applicable to weak scatterers. The effects of the sensing configuration and the scattering parameters in target separation estimation are analyzed. Conditions under which the targets' separation cannot be estimated are discussed for both models. Conditions for multiple scattering to be useful or detrimental to target separation estimation are discussed and illustrated.

FEMLIB: An Object-Oriented Framework for Optimization and Simulation

1995 ◽  
Author(s):  
Michael M. Tiller ◽  
Jonathan A. Dantzig
Keyword(s):  
Material Properties ◽  
Object Oriented ◽  
The Finite Element Method ◽  
Simulation And Optimization ◽  
Gradient Based ◽  
Level Problem ◽  
Simulation Results ◽  
Optimization And Simulation ◽  
High Level ◽  
Simulation Parameters

Abstract In this paper we discuss the design of an object-oriented framework for simulation and optimization. Although oriented around high-level problem solving, the framework defines several classes of problems and includes concrete implementations of common algorithms for solving these problems. Simulations are run by combining these algorithms, as needed, for a particular problem. Included in this framework is the capability to compute the sensitivity of simulation results to the different simulation parameters (e.g. material properties, boundary conditions, etc). This sensitivity information is valuable in performing optimization because it allows the use of gradient-based optimization algorithms. Also included in the system are many useful abstractions and implementations related to the finite element method.

Development of Parametric Kelvin Structures will Closed Cells

2016 ◽  
Vol 254 ◽  
pp. 49-54 ◽  
Author(s):  
Dan Andrei Şerban ◽  
Emanoil Linul ◽  
Sorin Sărăndan ◽  
Liviu Marşavina
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Relative Density ◽  
Material Properties ◽  
Cell Diameter ◽  
Rigid Polyurethane Foam ◽  
Loading Direction ◽  
Convergence Study ◽  
Simulation Results ◽  
Mesh Convergence

This work presents the design of a parametric Kelvin structure in which the relative density of the geometry can be varied by adjusting three parameters: cell diameter, cell wall thickness and cell chamfer radius, the structure consistsing of a tessellation of hollow truncated octahedral. The developed model was evaluated in terms of compressive stiffness for the case of a rigid polyurethane foam of 0.256 relative density. Three models were analyzed in order to determine the influence of geometric characteristics on mechanical properties: a model that presented no chamfer a model that presented a medium-sized chamfer and a model that presented a large chamfer. A mesh convergence study was performed which analyzed the results in terms of accuracy and time expenses for three element sizes for both linear and quadratic elements. Due to the orthotropic nature of the model, its response on both possible loading directions was investigated. Simulation results were compared with experimental results and yielded accurate results for one loading direction, when using the material properties for solid polyurethane described in literature.

The Numerical Simulation of Effective Elastic Response for WC-Co Cemented Carbide

2015 ◽  
Vol 1096 ◽  
pp. 417-421
Author(s):  
Pei Luan Li ◽  
Zi Qian Huang
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Finite Element ◽  
Theoretical Model ◽  
Material Properties ◽  
Cemented Carbide ◽  
Elastic Response ◽  
The Finite Element Method ◽  
Simulation Results ◽  
Element Method

By the use of finite element method, this paper predicts the effects of the shapes of reinforcements with different ductility (Co) on the effective elastic response for WC-Co cemented carbide. This paper conducts a comparative study on the material properties obtained through theoretical model, numerical simulation and experimental observations. Simulation results indicate that the finite element method is more sophisticated than the theoretical prediction.

A New Sampling Approach for the Multi-Scale Design of Metallic Materials

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Pinar Acar
Keyword(s):  
Material Properties ◽  
Sampling Method ◽  
Solution Space ◽  
Computational Time ◽  
Polycrystalline Materials ◽  
Microstructure Design ◽  
Multi Scale ◽  
Generate Property ◽  
Scale Design ◽  
Sampling Approach

Abstract We present a new sampling method for the multi-scale design of polycrystalline materials, which improves the computational time efficiency compared to the existing computational approaches. The solution strategy aims to find microstructure designs that optimize component-scale mechanical properties. The microstructure is represented with a probabilistic texture descriptor that quantifies the volume fractions of different crystallographic orientations. However, the original microstructure design space is high-dimensional and thus optimization in this domain is not favorable. Instead, we generate property closures, which are the reduced spaces of volume-averaged material properties that are computed in terms of the microstructural texture descriptors. We observe that the traditional design approaches which are based on sampling in the original microstructure space and sampling on the property closure are inefficient as they lead to highly concentrated design samples in the solution space. Therefore, we introduce a new sampling method in the property closure, which creates simplexes using the triangulation of the property hull and then generating samples for each simplex. Example problems include the optimization of Galfenol and α-titanium microstructures to improve non-linear material properties. The new sampling approach is shown to obtain better solutions while decreasing the required computational time compared to the previous microstructure design methods.

scholarly journals Experimental and simulation investigation on spring-in deformation for L-shape component

2019 ◽  
Vol 6 (1) ◽  
pp. 169-180 ◽  
Author(s):  
Tushar Gajjar ◽  
Dhaval B. Shah ◽  
S. J. Joshi ◽  
K. M. Patel
Keyword(s):  
Material Properties ◽  
Composite Laminates ◽  
Coefficient Of Thermal Expansion ◽  
Spring Back ◽  
Composite Part ◽  
Autoclave Process ◽  
Temperature Heat ◽  
Testing Techniques ◽  
Simulation Results ◽  
Key Parameter

AbstractThe angular deformation is key parameter in composite manufacturing for curvature surfaces. Process Induced Distortions (PID’s) are a major problem while manufacturing a composite part using autoclave process. Spring-back or spring-in is one of the PID in autoclave process. Spring-in effect either increase or decrease at angled section during curing of composite laminates. In this paper, L-shaped composite part has been manufactured using autoclave process. The material properties like glass transition temperature, heat reaction, crystallization temperature, Coefficient of Thermal Expansion have been measured for the cured component by using various testing techniques. Spring-in angle has been found for various number of layers and layup orientation. The simulation has been performed in ABAQUS software along with the COMPRO plug-in for each component. The variation of spring-in angle has been observed with changing material properties. The experimental results have been compared with simulation results. The percentage variation of spring-in deformation for experimental and simulation results has been found in the range of 5-7%.

Research on the Micro-Mechanical State at Tip of Environmentally Assisted Cracking Based on Latin Hypercube Sampling Method

2019 ◽  
Vol 795 ◽  
pp. 74-78
Author(s):  
Kuan Zhao ◽  
He Xue ◽  
Ling Yan Zhao
Keyword(s):  
Oxide Film ◽  
Material Properties ◽  
Nuclear Power ◽  
Power Plants ◽  
Sampling Method ◽  
Latin Hypercube Sampling ◽  
Primary Circuit ◽  
Mechanical State ◽  
Latin Hypercube ◽  
Environmentally Assisted Cracking

Environmentally assisted cracking (EAC) of nickel-based alloys is one of the most significant potential safety hazards in the primary circuit of nuclear power plants. To understand the influence of randomness on micro-mechanical state at tip of EAC, Latin hypercube sampling method is applied to analyze the uncertainty of stress-strain in the oxide film at the EAC tip considering the uncertainties of load and material properties of base metal and oxide film. Meanwhile, to improve the efficiency of numerical analysis, MATLAB is employed in the secondary development for ABAQUS. With the help of finite element numerical simulation and Latin hypercube sampling method, the uncertainty of mechanical properties at tip of EAC in one-inch compact tension specimen is simulated and analyzed in this study. The results show that the randomness of material properties and load markedly affect the uncertainty of micro-mechanical state. Among the variables, The randomness of load has the greatest influence on uncertainty of strain, and Poisson`s ratio of oxide film is the smallest effect.

scholarly journals Iterative Analysis of Dielectric Constant of Patch Antenna Substrate at UHF Band

2018 ◽  
Vol 7 (2.16) ◽  
pp. 7
Author(s):  
Amish Kumar Jha ◽  
Bharti Gupta Gupta ◽  
Preety D Swami
Keyword(s):  
Dielectric Constant ◽  
Material Properties ◽  
Patch Antenna ◽  
Dielectric Materials ◽  
Substrate Material ◽  
Frequency Range ◽  
Shape Model ◽  
Iterative Analysis ◽  
Working Frequency ◽  
Simulation Results

This paper presents an investigation of effect of substrate material properties on the performance of antenna. The simulations are tested for 30 different dielectric materials on the basic RPA antenna model as well as on the most common U shape model using CST Microwave Studio. Two designs are proposed. On the basis of simulation results it has been concluded that for the first design the best material is which has a dielectric constant of 2.7 (𝜀r = 2.7) with bandwidth improvements of around 69.33% to 88.6% as compared to the most frequently used materials at present. For the second design the best result is obtained for the material that has dielectric constant in the range 2.0 to 2.7.  For a material having dielectric constant of 2.1 (𝜀r = 2.1) bandwidth improvement of around 11.74% with respect to RT Duroid was observed. For the second design, radiations from all other materials were not available in the working frequency range of 1GHz to 6GHz.  

Do attractive scattering potentials concentrate particles at the origin in one, two and three dimensions? III. High energies in quantum mechanics

1983 ◽  
Vol 388 (1795) ◽  
pp. 445-456 ◽  
Keyword(s):  
Quantum Mechanics ◽  
Born Approximation ◽  
Enhancement Factor ◽  
Bessel Functions ◽  
Particle Density ◽  
Incident Beam ◽  
Three Dimensions ◽  
Incident Momentum ◽  
High Energies ◽  
Factor Α

The enhancement factor α D ≡ 1+ δα D is defined (in D dimensions) as the ratio of the particle density at the origin to the density far upstream in the incident beam. At high incident momentum p (and for regular potentials) the first Born approximation is known to be adequate in 3D and 1D, and is assumed to be adequate also in 2D; it entails δα 1 = ─δα 3 if U ( r ) in 3D equals U ( x ) in 1D when r = x . For central potentials U ( r ) with U (0) finite, previous work implies δα 3 ~ ─δα 1 ~ ─ mU (0)/ p 2 , and δα 2 = 0 to the same order h °. It is shown that if U ( r →0) ~ U (0) + r U' (0) + ..., then δα 2 ~ (2 m U' (0) h / p 3 )(π/16), the value of U (0) being irrelevant. If U ( r →0) ~ ─ C / r q , with 0 < q < 2, then δα 3 ~ ─δα 1 ~ (2 mC / h q p 2- q ) π ½ Γ(1-½ q )/2Γ(½+½ q ); and, with -1 < q < 2, δα 2 ~ (2 m C / h q p 2- q )π ½ Γ 2 (1-½ q )/2Γ(½ q )Γ(3/2-½ q ). The only mathematics needed in 3D and 1D is the standard asymptotic estimation of Fourier integrals; but in 2D one needs to develop corresponding methods for integrals where the sine or cosine has been replaced by a product J 0 Y 0 of two Bessel functions.

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