High-frequency Rayleigh waves in materials with micro-structure and couple-stress effects

2003 ◽  
Vol 40 (10) ◽  
pp. 2501-2520 ◽  
Author(s):  
H.G. Georgiadis ◽  
E.G. Velgaki
2021 ◽  
Author(s):  
Rendi Kurniawan ◽  
Farooq Ahmed ◽  
Gun Chul Park ◽  
Tae Jo Ko

Abstract In the 2D-Vibration Assisted Cutting (2D-VAC) method, the cutting tool shakes in a 2-dimensional approach because of superimposed high-frequency modulation. This high-frequency modulation effect creates a displacement at a tiny scale of micrometers and causes an escalation in the resultant cutting speed. Consequently, 2D-VAC has superior advantages compared to traditional cutting (TC). This manuscript describes research on 2D-VAC that focuses on modeling cutting forces (mathematical model) and finite element analysis (FEA) results. The FEA results are focused on the von Mises stress, plastic strain, cutting force, cutting temperature, and residual stress. In addition, an experiment for the chip formation, micro-structure layer, and micro-hardness was also analyzed in this study. According to the modeling results, the cutting force has a comparable pattern to the FEA results. The stress contour result confirms that the 2D-VAC method has lower stress than that in the TC method during tool retraction mode. Additionally, the plastic strain in the 2D-VAC method can be higher than that in the TC method. According to the temperature results, the peak temperature in the 2D-VAC could be higher than that in the TC method. The residual stress shows that there is a compressive effect. Thus, the compressive stress is higher than that in the TC method. Micro-hardness results confirmed that there is not too much change from the original surface in the 2D-VAC method. The result of micro-structure morphology also confirmed that there is a significant shear deformation flow in case of the TC method, although less occurs in the 2D-VAC method.


2020 ◽  
Vol 110 (2) ◽  
pp. 793-802
Author(s):  
Ping Ping ◽  
Risheng Chu ◽  
Yu Zhang ◽  
Jun Xie

ABSTRACT High-frequency Rayleigh waves can be extracted from ambient seismic noises through noise correlation functions (NCFs), which provides a useful tool to image shallow structures in topographic regions, for example, landslides. Topography may affect signal-to-noise ratios (SNRs) of extracted Rayleigh waves. It is necessary to investigate the propagation features of Rayleigh waves passing a 3D topography. Based on the incident and scattered waves satisfying the free surface boundary conditions, we first derive the displacement responses of Rayleigh waves across a 3D elastic wedge. The results show that the particle motions of Rayleigh waves are an ellipse whose longer axis is always perpendicular to the topographic free surface. Therefore, the Qg component, perpendicular to the topographic free surface, is a better choice to extract high-frequency Rayleigh waves than the conventional vertical component. To verify the choice, we carry out numerical simulations to extract high-frequency NCFs for a typical 3D massif model. Finally, we apply this approach to extract high-frequency Rayleigh-wave NCFs on the Xishancun landslide in southwestern China. The NCFs obtained using the Qg component have more coherent waveforms and higher SNRs than those using the vertical component. We conclude that the Qg component has advantages in extracting high-frequency Rayleigh waves over the conventional vertical component.


2019 ◽  
Vol 286 ◽  
pp. 07002
Author(s):  
M. Mouda ◽  
M. Nabhani ◽  
M. El Khlifi

This paper presents a numerical investigation of lubricating slider bearings with conducting couple stress fluids using externally applied magnetics fields. The modified two-dimensional magnetohydrodynamic couple stress Reynolds-type equation is obtained. This governing equation is resolved numerically by using finite difference scheme, which involves the Gauss–Seidel method to compute the bearing characteristics. Numerical results using different considered values of the couple stress and Hartman number are presented. These results demonstrate that the transverse magnetic field and couple stress effects are significant.


2000 ◽  
Vol 143 (2) ◽  
pp. 365-375 ◽  
Author(s):  
U. Dutta ◽  
N. Biswas ◽  
A. Martirosyan ◽  
S. Nath ◽  
M. Dravinski ◽  
...  

2018 ◽  
Vol 150 ◽  
pp. 1-10 ◽  
Author(s):  
Ping Ping ◽  
Risheng Chu ◽  
Jiajun Chong ◽  
Sidao Ni ◽  
Yu Zhang

1972 ◽  
Vol 39 (2) ◽  
pp. 378-384 ◽  
Author(s):  
B. Rulf ◽  
B. Z. Robinson ◽  
P. Rosenau

The problem of propagation of guided elastic waves near curved surfaces and in layers of nonconstant thickness is investigated. Rigorous solutions for such problems are not available, and a method is shown for the construction of high frequency asymptotic solutions for such problems in two dimensions. The method is applied to Love waves, which are SH-waves in an elastic layer, Rayleigh waves, which are elastic waves guided by a single free surface, and Lamb waves, which are SV-waves guided in a plate or layer with two free surfaces. The procedure shown breaks the second-order boundary-value problems which have to be solved into successions of simpler problems which can be solved numerically. Some numerical examples for Rayleigh waves are carried out in order to demonstrate the utility of our method. The method shown is useful for a large variety of guided wave problems, of which the ones we treat are just examples.


2017 ◽  
Vol 22 (3) ◽  
pp. 759-767 ◽  
Author(s):  
A. Walicka ◽  
P. Jurczak ◽  
J. Falicki

AbstractThe flow of a couple-stress lubricant in a clearance of a curvilinear thrust hydrostatic bearing with impermeable walls is considered. The flow in the bearing clearance is considered with inertia forces. The equations of motion are solved by an averaged inertia method. As a result, the formulae for pressure distributions without and with inertia effects were obtained. Radial thrust bearings and spherical bearings are discussed as numerical examples. It is shown that inertia effects influence the bearing performance considerably.


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