Three-dimensional forward and inverse models for gravity fields based on the Fast Fourier Transform

2006 ◽  
Vol 32 (6) ◽  
pp. 727-738 ◽  
Author(s):  
Young Hong Shin ◽  
Kwang Sun Choi ◽  
Houze Xu
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Three Dimensional ◽  
Inverse Models ◽  
Gravity Fields

A Fast Method for Solving Contact Plasticity in a Half Space

2011 ◽  
Author(s):  
Zhanjiang Wang ◽  
Xiaoqing Jin ◽  
Shuangbiao Liu ◽  
Leon M. Keer ◽  
Jian Cao ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Residual Stresses ◽  
Fast Fourier Transform ◽  
Half Space ◽  
Three Dimensional ◽  
New Method ◽  
Fast Method ◽  
Discrete Convolution ◽  
Influence Coefficients ◽  
The One

This paper presents a new method of contact plasticity analysis based on Galerkin vectors to solve the eigenstresses due to eigenstrain. The influence coefficients relating eigenstrains to eigenstresses thus can be divided into four terms the one due to the eigenstrains in the full space, others due to the mirrored eigenstrains in the mirror half space. Each term can be solved fast and efficient by using the three-dimensional discrete convolution and fast Fourier transform (DC-FFT) or the three-dimensional discrete correlation and fast Fourier transform (DCR-FFT). The new method is used to analyze the contact plastic residual stresses in half space.

Fast Fourier Transform Based Numerical Methods for Elasto-Plastic Contacts of Nominally Flat Surfaces

2008 ◽  
Vol 75 (1) ◽  
Author(s):  
W. Wayne Chen ◽  
Shuangbiao Liu ◽  
Q. Jane Wang
Keyword(s):  
Fourier Transform ◽  
Numerical Methods ◽  
Fast Fourier Transform ◽  
Analytical Solutions ◽  
Three Dimensional ◽  
Stress And Strain ◽  
Two Dimensional ◽  
Response Functions ◽  
Strain Fields ◽  
Flat Surfaces

This paper presents a three-dimensional numerical elasto-plastic model for the contact of nominally flat surfaces based on the periodic expandability of surface topography. This model is built on two algorithms: the continuous convolution and Fourier transform (CC-FT) and discrete convolution and fast Fourier transform (DC-FFT), modified with duplicated padding. This model considers the effect of asperity interactions and gives a detailed description of subsurface stress and strain fields caused by the contact of elasto-plastic solids with rough surfaces. Formulas of the frequency response functions (FRF) for elastic/plastic stresses and residual displacement are given in this paper. The model is verified by comparing the numerical results to several analytical solutions. The model is utilized to simulate the contacts involving a two-dimensional wavy surface and an engineering rough surface in order to examine its capability of evaluating the elasto-plastic contact behaviors of nominally flat surfaces.

scholarly journals Two- and Three-Dimensional Fast Intrawall Imaging with Microwave Tomographic Algorithm

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Wenji Zhang ◽  
Ahmad Hoorfar ◽  
Christopher Thajudeen
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Real Time ◽  
Three Dimensional ◽  
Inverse Fast Fourier Transform ◽  
Real Time Processing ◽  
Time Processing ◽  
Imaging Algorithm ◽  
Reflection Model ◽  
Effectiveness And Efficiency

A fast and efficient microwave tomographic algorithm is proposed for 2-D and 3-D real-time intrawall imaging. The exploding reflection model is utilized to simplify the imaging formulation, and the half-space Green’s function is expanded in the spectral domain to facilitate the easy implementation of the imaging algorithm with the fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT). The linearization of the inversion scheme and employment of FFT/IFFT in the imaging formula make the algorithm suitable for various applications pertaining to the inspection of a large probed region and allow real-time processing. Representative numerical and experimental results are presented to show the effectiveness and efficiency of the proposed algorithm for real-time intrawall characterization.

Stress Analysis of Layered Elastic Solids With Cracks Using the Fast Fourier Transform and Conjugate Gradient Techniques

2001 ◽  
Vol 68 (5) ◽  
pp. 708-714 ◽  
Author(s):  
I. A. Polonsky ◽  
L. M. Keer
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Conjugate Gradient ◽  
Protective Coatings ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Multiple Cracks ◽  
Elastic Solids ◽  
Shape Changes ◽  
Stress Analyses

The fast Fourier transform (FFT) technique has recently been applied to stress analyses of layered elastic solids, with a great deal of success. However, the existing FFT-based methods are limited to intact solids. This paper explores the possibility of using FFT for stress analyses of layered elastic solids containing cracks. A new numerical approach is developed by combining three-dimensional FFT with the theory of periodic eigenstrain and the conjugate gradient method. The new method is primarily designed for analyzing complex three-dimensional crack patterns in layered solids, such as those produced in thin protective coatings by roughness-induced contact stresses. The method should be particularly advantageous for studying crack propagation in coatings, as it does not require remeshing when the crack shape changes. Numerical examples illustrating advantages as well as limitations of the method are presented. Some unexpected results that were obtained for multiple cracks in a thin coating are discussed.

Three-dimensional magnetic field analysis of micromotor by fast Fourier transform

1999 ◽  
Vol 35 (5) ◽  
pp. 3685-3687 ◽  
Author(s):  
Mingsheng Zhang ◽  
Bingcu Cai ◽  
Xiaolin Zhao ◽  
Zongguang Wang
Keyword(s):  
Magnetic Field ◽  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Three Dimensional ◽  
Field Analysis ◽  
Magnetic Field Analysis
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