Elasto-Viscoplastic Dispersive Waves in Silicon Wafers

2007 ◽  
Author(s):  
Li Liu ◽  
C. Steve Suh
Keyword(s):  
Stress Wave ◽  
High Temperatures ◽  
Nonlinear Function ◽  
Low Frequency ◽  
Propagation Model ◽  
Constitutive Law ◽  
Stress Wave Propagation ◽  
Thickness Variation ◽  
Low Frequencies ◽  
Induced Stress

This paper provides the required knowledge base for establishing Laser Induced Stress Wave Thermometry (LISWT) as a viable alternative to current infrared technologies for temperature measurement up to 1000°C with ±1°C resolution. A stress wave propagation model having a complex, temperature-dependent elasto-viscoplastic constitutive law is developed. Investigated results show that wave group velocity is a nonlinear function of temperature. Nonlinearity becomes more prominent at high temperatures and low frequencies. As such, for LISWT to achieve better thermal resolution at high temperatures, low frequency components of the induced stress wave should be exploited. The results also show that the influence of temperature on attenuation is relatively small. It is not recommended to use attenuation for resolving temperature variation as small as several degrees Celsius. In addition to temperature, geometry also is found to have an impact on wave dispersion and attenuation. The influence of thickness on wave velocity is significant, thus suggesting that for LISWT to achieve high temperature resolution, wafer thickness must be accurately calibrated in order to eliminate all possible errors introduced by thickness variation.

Research on Attenuation of Shock Induced Stress Wave in Multi-Layered Thin Cylindrical Rods

2018 ◽  
Vol 878 ◽  
pp. 35-40
Author(s):  
Fei Peng ◽  
Zhi Guang Yang ◽  
Li Peng Wang
Keyword(s):  
Stress Wave ◽  
Wave Attenuation ◽  
Impact Load ◽  
Layered Media ◽  
One Dimension ◽  
Stress Wave Propagation ◽  
Propagation Theory ◽  
Induced Stress ◽  
The One ◽  
Wave Induced

The attenuation of stress wave induced by impact load in multi-layered thin cylindrical rods has been investigated and analyzed. Firstly, based on stress wave propagation theory, the one dimension solution of the response of stress wave in three-layered media has been given. Secondly, a three-layered thin cylindrical rod has been established through FEM, and the propagation and attenuation of stress wave in it has been analyzed. The analytical and numerical results showed that the stress wave attenuation could be achieved by using multi-layered media.

scholarly journals Full-waveform inversion with extrapolated low-frequency data

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. R339-R348 ◽  
Author(s):  
Yunyue Elita Li ◽  
Laurent Demanet
Keyword(s):  
Waveform Inversion ◽  
Low Frequency ◽  
Velocity Model ◽  
Propagation Model ◽  
Full Waveform Inversion ◽  
Frequency Data ◽  
Local Minima ◽  
Bandwidth Extension ◽  
Low Frequencies ◽  
Full Waveform

The availability of low-frequency data is an important factor in the success of full-waveform inversion (FWI) in the acoustic regime. The low frequencies help determine the kinematically relevant, low-wavenumber components of the velocity model, which are in turn needed to avoid convergence of FWI to spurious local minima. However, acquiring data less than 2 or 3 Hz from the field is a challenging and expensive task. We have explored the possibility of synthesizing the low frequencies computationally from high-frequency data and used the resulting prediction of the missing data to seed the frequency sweep of FWI. As a signal-processing problem, bandwidth extension is a very nonlinear and delicate operation. In all but the simplest of scenarios, it can only be expected to lead to plausible recovery of the low frequencies, rather than their accurate reconstruction. Even so, it still requires a high-level interpretation of band-limited seismic records into individual events, each of which can be extrapolated to a lower (or higher) frequency band from the nondispersive nature of the wave-propagation model. We have used the phase-tracking method for the event separation task. The fidelity of the resulting extrapolation method is typically higher in phase than in amplitude. To demonstrate the reliability of bandwidth extension in the context of FWI, we first used the low frequencies in the extrapolated band as data substitute, to create the low-wavenumber background velocity model, and then we switched to recorded data in the available band for the rest of the iterations. The resulting method, extrapolated FWI, demonstrated surprising robustness to the inaccuracies in the extrapolated low-frequency data. With two synthetic examples calibrated so that regular FWI needs to be initialized at 1 Hz to avoid local minima, we have determined that FWI based on an extrapolated [1, 5] Hz band, itself generated from data available in the [5, 15] Hz band, can produce reasonable estimations of the low-wavenumber velocity models.

scholarly journals Subsection Forward Modeling Method of Blasting Stress Wave Underground

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Bo Yan ◽  
Xinwu Zeng ◽  
Yuan Li
Keyword(s):  
Finite Element ◽  
Stress Wave ◽  
Source Region ◽  
Stress Waves ◽  
Nonlinear Finite Element ◽  
Stress Wave Propagation ◽  
Local Structures ◽  
Nonlinear Responses ◽  
Induced Stress ◽  
Material Nonlinear

The generation of stress waves induced by explosions underground is governed by material nonlinear responses of materials surrounding explosions and affected by source region mediums and local structures. A nonlinear finite element (NFE) method can simulate the generation efficiently. However, the calculation using the NFE to observational distances, where motions are elastic, is computationally challenging. In order to tackle this problem, we present a subsection numerical simulating method for forward modelling the generation and propagation of stress waves with a hybrid method coupling the NFE and a linear finite element (LFE). The subsection idea is developed based on previous works; calculating steps of the subsection method as well as techniques of passing motions from a source region to an elastic region are discussed. 3D numerical simulations of stress wave propagation in rock generated by decoupled explosion underground with two methods for comparison are carried out. The accuracy of the subsection method is demonstrated with simulated results. The demand of PC memory and the calculating time are investigated. The subsection method provides another approach for modeling and understanding the generation and propagation of explosion-induced stress waves, though, currently, studies are preliminary.

Stress Wave in Gelatin from Temporary Cavity

2013 ◽  
Vol 423-426 ◽  
pp. 347-350
Author(s):  
Gen Lin Mo ◽  
Zhi Lin Wu
Keyword(s):  
Stress Wave ◽  
Radial Stress ◽  
Stress Waves ◽  
Propagation Model ◽  
Elastic Region ◽  
Stress Wave Propagation ◽  
Cavity Pressure ◽  
Steel Sphere ◽  
Temporary Cavity ◽  
Theoretical Results

To study the injury mechanism of stress wave from temporary cavity in gelatin, a stress wave propagation model is established. Based on experimental phenomena, gelatin around the trajectory is divided into fail region and elastic region. In the fail region, gelatin is considered to be incompressible and loop stress is zero. Gelatin in the elastic region is assumed to be plane-strain. Moving equations in the two regions are built. A 4.8 mm steel sphere is fired into gelatin at 720 m/s. Displacements of the temporary cavity are obtained from the experiment. By solving the moving equations with boundary conditions, amplitude of cavity pressure, radial stress distribution in gelatin are obtained. The theoretical results can be used to explain stress waves produced by temporary cavity.

Physics of laser-induced stress wave propagation, cracking, and cavitation in biological tissue

1994 ◽  
Author(s):  
Jonathan Schaffer ◽  
Irving Itzkan ◽  
Douglas Albagli ◽  
Marta Dark ◽  
Charles von Rosenberg ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Stress Wave ◽  
Biological Tissue ◽  
Stress Wave Propagation ◽  
Induced Stress
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