The Effect of Anisotropy on the Percolation Threshold of Sealing Surfaces

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Zhimeng Yang ◽  
Jianhua Liu ◽  
Xiaoyu Ding ◽  
Feikai Zhang
Keyword(s):  
Fourier Transform ◽  
Theoretical Result ◽  
Fast Fourier Transform ◽  
Percolation Threshold ◽  
Rough Surface ◽  
Conjugate Gradient ◽  
Surface Anisotropy ◽  
Sealing Performance ◽  
The Relationship ◽  
Theoretical Results

The percolation threshold strongly affects sealing performance. This paper investigates the relationship between the percolation threshold and the rough surface anisotropy, which is represented by the Peklenik number, γ. A series of anisotropic rough surfaces were generated and the conjugate gradient-fast Fourier transform (CG-FFT) method was used to determine the percolation threshold. The percolation threshold was found to be A/A0≈0.484±0.009 (averaged over 45 surfaces) was established for an isotropic rough surface (γ=1). Furthermore, it was also found that the percolation threshold decreased from A/A0≈0.528±0.011 to A/A0≈0.431±0.008 as 1/γ increased from 0.6 to 2. Our results differ from the theoretical result of Persson et al., where A/A0=γ/(1+γ). Comparing our calculated results with the theoretical results established the presence of an intersection value of 1/γ that was related to the effect of elastic deformation on the percolation threshold. When 1/γ was smaller than the intersection value, our calculated results were lower than the theoretical ones; and when 1/γ was greater than the intersection value, our calculated results were higher than the theoretical ones.

Gas Sealing Performance Study of Metal W Shaped Seal Ring

2014 ◽  
Vol 633-634 ◽  
pp. 68-73 ◽  
Author(s):  
Min Jie Xing ◽  
Qing Xue ◽  
Shuang Fu Suo ◽  
Chun Yan Liu
Keyword(s):  
Rough Surface ◽  
Seal Ring ◽  
Performance Study ◽  
Equipment Operation ◽  
Sealing Performance ◽  
Object Based ◽  
Metal Seal ◽  
Security And Reliability ◽  
Rough Surface Contact ◽  
The Relationship

Gas sealing performance of metal seal ring directly affects the security and reliability of equipment operation. Gas static seals of W-ring is taken as a study object, based on the theory of rough surface contact model and the theory of gas average flow model in the rough surface gap, the gas sealing leakage model is established to analyze the relationship between the leakage and the sealing load and surface roughness parameters.

scholarly journals A study of acoustic characteristics of voluntary expiratory sounds produced before and immediately after swallowing

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Shoma Hattori ◽  
Shinji Nozue ◽  
Yoshiaki Ihara ◽  
Koji Takahashi
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Time Window ◽  
Maximum Amplitude ◽  
Comparison Method ◽  
Window Length ◽  
Acoustic Characteristics ◽  
The Mean ◽  
Time Waveform ◽  
The Relationship

AbstractTo evaluate the expiratory sounds produced during swallowing recorded simultaneously with videofluorographic examination of swallowing (VF) using fast Fourier transform (FFT), and to examine the relationship between dysphagia and its acoustic characteristics. A total of 348 samples of expiratory sounds were collected from 61 patients with dysphagia whose expiratory sounds were recorded during VF. The VF results were evaluated by one dentist and categorized into three groups: safe group (SG), penetration group (PG), and aspiration group (AG). The duration and maximum amplitude of expiratory sounds produced were measured as the domain characteristics on the time waveform of these sounds and compared among the groups. Time window-length appropriate for FFT and acoustic discriminate values (AD values) of SG, PG, and AG were also investigated. The groups were analyzed using analysis of variance and Scheffé's multiple comparison method. The maximum amplitude of SG was significantly smaller than those of PG and AG. The mean duration in SG (2.05 s) was significantly longer than those in PG (0.84 s) and AG (0.96 s). The AD value in SG was significantly lower than those in PG and AG. AD value detects penetration or aspiration, and can be useful in screening for dysphagia.

Multi-Symplectic Fourier Pseudospectral Method for the Kawahara Equation

2014 ◽  
Vol 16 (1) ◽  
pp. 35-55 ◽  
Author(s):  
Yuezheng Gong ◽  
Jiaxiang Cai ◽  
Yushun Wang
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Pseudospectral Method ◽  
Kawahara Equation ◽  
Fourier Pseudospectral Method ◽  
Numerical Examples ◽  
Fourier Pseudospectral ◽  
Energy And Momentum ◽  
The Relationship ◽  
Pseudospectral Scheme

AbstractIn this paper, we derive a multi-symplectic Fourier pseudospectral scheme for the Kawahara equation with special attention to the relationship between the spectral differentiation matrix and discrete Fourier transform. The relationship is crucial for implementing the scheme efficiently. By using the relationship, we can apply the Fast Fourier transform to solve the Kawahara equation. The effectiveness of the proposed methods will be demonstrated by a number of numerical examples. The numerical results also confirm that the global energy and momentum are well preserved.

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.

Sign in / Sign up

Export Citation Format

Share Document