scholarly journals Numerical simulation of laser-generated ultrasonic waves in steel with gradient changes of near-surface elastic property

2007 ◽  
Vol 56 (12) ◽  
pp. 7058
Author(s):  
物理学报
Keyword(s):  
Numerical Simulation ◽  
Elastic Property ◽  
Ultrasonic Waves ◽  
Near Surface

The Compliance Method for Measurement of Near Surface Residual Stresses—Analytical Background

1994 ◽  
Vol 116 (4) ◽  
pp. 550-555 ◽  
Author(s):  
M. Gremaud ◽  
W. Cheng ◽  
I. Finnie ◽  
M. B. Prime
Keyword(s):  
Numerical Simulation ◽  
Residual Stresses ◽  
Random Errors ◽  
Residual Stress Field ◽  
Near Surface ◽  
Surface Residual Stresses ◽  
Zero Shift ◽  
Stress States ◽  
The Stability ◽  
Piecewise Functions

Introducing a thin cut from the surface of a part containing residual stresses produces a change in strain on the surface. When the strains are measured as a function of the depth of the cut, residual stresses near the surface can be estimated using the compliance method. In previous work, the unknown residual stress field was represented by a series of continuous polynomials. The present paper shows that for stress states with steep gradients, superior predictions are obtained by using “overlapping piecewise functions” to represent the stresses. The stability of the method under the influence of random errors and a zero shift is demonstrated by numerical simulation.

CREEPING SURFACE LONGITUDINAL ACOUSTIC WAVE: MAIN PROPERTIES AND APPLICATION POSSIBILITIES

2021 ◽  
pp. 4-12
Author(s):  
V. G. Shevaldykin
Keyword(s):  
Critical Angle ◽  
Flaw Detection ◽  
Ultrasonic Signal ◽  
Ultrasonic Waves ◽  
Concave Surface ◽  
Ultrasonic Tomography ◽  
Transverse Waves ◽  
Near Surface ◽  
The Third ◽  
Creeping Wave

Creeping ultrasonic waves have long been successfully used for flaw detection of near-surface and near-bottom zones of metal products. However, due to the fact that the creeping wave generates a lateral transverse wave directed into the metal volume at the third critical angle, it is also possible to test internal defects in principle. At known velocities of propagation of longitudinal and transverse waves in the metal, the third critical angle is easily calculated. Therefore, the time of propagation of the ultrasonic signal along any trajectory between points on the surface and in the volume of the metal can be calculated. Usually, creeping waves are used to test products of plane-parallel shape. There are no cases of their application on curved surfaces in the literature. It is possible that the creeping wave can also propagate over a concave surface. The aim of the article is to test experimentally new ways of using creeping waves. The propagation trajectories of the creeping and lateral transverse waves were studied on a steel plate. The time of passage of the ultrasonic signal along such trajectories of different lengths was measured, and the measurement results were compared with the calculated time values. The measured and calculated values coincided with accuracy sufficient for the coherent accumulation of echo signals that passed through the metal part of the path by the creeping wave and another part of the path by the lateral transverse wave.The propagation of the creeping wave over a concave surface was studied on a steel sample with cylindrical faces of different radii. As a result, it turned out that on a concave surface, the creeping wave propagates at the same speed of longitudinal waves as on a flat surface, but it decays much more strongly with distance. Studies have shown that creeping waves can be used in ultrasonic tomography, where a preliminary calculation of the propagation trajectories of ultrasonic signals is required. The propagation of creeping waves over concave surfaces extends the capabilities of the TOFD method to the area of intube testing

Quantitative Short-pulse Acoustic Microscopy and Application to Materials Characterization

2000 ◽  
Vol 6 (1) ◽  
pp. 59-67
Author(s):  
Theodore E. Matikas
Keyword(s):  
Elastic Property ◽  
Acoustic Waves ◽  
Short Pulse ◽  
Surface Acoustic Waves ◽  
Tone Burst ◽  
Acoustic Microscopy ◽  
Near Surface ◽  
Microscopy Technique ◽  
Setup Phase ◽  
Additional Reference

Abstract A new acoustic microscopy method was developed for providing near-surface elastic property mapping of a material. This method has a number of advantages over the traditional V(z) technique. First, it enables one to perform measurements in an automated mode that only requires user intervention in the setup phase. This automated mode makes it feasible to obtain quantitative microscopy images of the elastic property over an area on the material being tested. Also, it only requires a conventional ultrasonic system operating in pulsed mode for collecting the data, rather than a specialized tone-burst system, which is needed in the traditional quantitative scanning acoustic microscopy technique. Finally, unlike the traditional method, the new experimental process does not require calibration of the systems electronics or additional reference data taken under hard-to-duplicate identical conditions from a material that does not exhibit surface acoustic waves.

GPU-based solution of Biot’s elastodynamic equations to account for fluid pressure diffusion

2020 ◽  
Author(s):  
Yury Alkhimenkov ◽  
Lyudmila Khakimova ◽  
Ludovic Raess ◽  
Beatriz Quintal ◽  
Yury Podladchikov
Keyword(s):  
Numerical Simulation ◽  
Diffusion Process ◽  
Diffusion Processes ◽  
Absorbing Boundary Conditions ◽  
Fast Wave ◽  
Time Step ◽  
Near Surface ◽  
Mechanical Coupling ◽  
Slow Diffusion ◽  
Fluid Diffusion

<p> <span>Elastodynamic hydro-mechanical coupling based on Biot’s theory describes an upscaling of the fluid-solid deformation at a porous scale. Examples of applications of this theory are near surface geophysics, CO2 monitoring, induced seismicity, etc. The dynamic response of a coupled hydro-mechanical system can produce fast and slow compressional waves and shear waves. In many earth materials, a propagating slow wave degenerates into a slow diffusion mode on orders of magnitude larger time scales compared to wave propagation. In the present work, we propose a new approach to accelerate the numerical simulation of slow diffusion processes. We solve the coupled Biot elastodynamic hydro-mechanical equations for particle velocity and stress in the time domain using the finite volume method on a rectangular grid in three dimensions. The MPI-based multi-GPU code is implemented using CUDA-C programming language. We prescribe a fluid injection at the center of the model that generates a fast propagating wave and a significantly slower fluid-diffusion event. The fast wave is attenuated due to absorbing boundary conditions after what the slow fluid-diffusion process remains active. A Courant stability condition for the fast wave controls the time-step in the entire simulation, resulting in a suboptimal short time step for the diffusion process. Once fast waves are no longer present in the model domain, the hydro-mechanical coupling vanishes in the inertial terms allowing for an order of magnitude larger time steps. We accelerate the numerical simulation of slow diffusion processes using a pseudo-transient method that permits to capture the transition in time step restrictions. This latest development enables us to simulate quasi-static and dynamic responses of two-phase media. We present benchmarks confirming the numerical efficiency and accuracy of the novel approach. The further development of the code will capture inelastic physics starting from the dynamic events (earthquake modeling) to quasi-static faulting. </span></p>

Sign in / Sign up

Export Citation Format

Share Document