Longitudinal and transverse elastic waves in 1D granular materials modeled as micromorphic continua

Wave Motion ◽  
2019 ◽  
Vol 90 ◽  
pp. 175-195 ◽  
Author(s):  
Anil Misra ◽  
Nima Nejadsadeghi
Keyword(s):  
Granular Materials ◽  
Elastic Waves ◽  
Micromorphic Continua

Characteristics of mechanical response and acoustic emission during granular shearing

2020 ◽  
Author(s):  
Yao Jiang ◽  
Gonghui Wang
Keyword(s):  
Granular Materials ◽  
Elastic Waves ◽  
High Frequency ◽  
Mechanical Response ◽  
Acoustic Emissions ◽  
Shear Plane ◽  
Geophysical Processes ◽  
Shearing Deformation ◽  
Primary Frequency ◽  
Landslides And Debris Flows

<p>The shear behavior of granular materials has drawn considerable attention due to its great potential for various geophysical processes such as landslides and debris flows. Field and remote sensing observations reveal that the progressive maturation of these geophysical events may involve different styles of movement, such as stable creep, periodic slow sliding or accelerative sliding. Laboratory experiments also suggest that the mechanical conditions of granular materials may play a significant role in controlling diverse frictional behaviors, such as shear-rate weakening or strengthening. Furthermore, the granular frictional processes may involve abrupt perturbations of internal forces and release of strain energy. Such energy release events are manifested in the generation of high frequency (kHz-MHz) elastic waves, termed acoustic emissions (AEs), which deliver important information concerning the physical processes of granular shearing deformation.</p><p>A significant, though still inconclusive, body of research has been directed toward revealing possible mechanisms of AEs occurring on rock or among granular materials in shear. These studies attributed the generation of AEs to the formation of microcracks in intact rocks, the breaking of asperities between solid surfaces or the rearrangement of grain contacts. In this study, we performed laboratory tests on granular analogues composed of spherical glass beads in a ring shear configuration under conditions of room temperature and atmospheric humidity to examine whether the AE events are correlated with mechanical response. For measurements of elastic waves, a high-frequency AE transducer was installed near the shear plane. AE signals and mechanical data were synchronously sampled at the rate of 1 MHz using an additional recoding system.</p><p>The results show that (1) there is a strong correlation between the stress drop and the main acoustic burst; (2) the primary frequency bands are in the tens of kHz ranges for acoustic signals generated during granular shearing; (3) the onset of AE amplitudes precedes the impending global mechanical failures by several milliseconds.</p>

Dissipation in granular materials

1998 ◽  
Vol 77 (5) ◽  
pp. 1413-1425 ◽  
Author(s):  
Dietrich E.Wolf, Farhang Radjai, Sabine Dipp
Keyword(s):  
Granular Materials

Remarks on nonlinear elastic waves with null conditions

2020 ◽  
Vol 26 ◽  
pp. 121
Author(s):  
Dongbing Zha ◽  
Weimin Peng
Keyword(s):  
Initial Data ◽  
Global Existence ◽  
Elastic Waves ◽  
Wave Equations ◽  
Alternative Proof ◽  
Classical Solutions ◽  
Small Initial Data ◽  
Hyperelastic Materials ◽  
Variational Structure ◽  
Nonlinear Elastic

For the Cauchy problem of nonlinear elastic wave equations for 3D isotropic, homogeneous and hyperelastic materials with null conditions, global existence of classical solutions with small initial data was proved in R. Agemi (Invent. Math. 142 (2000) 225–250) and T. C. Sideris (Ann. Math. 151 (2000) 849–874) independently. In this paper, we will give some remarks and an alternative proof for it. First, we give the explicit variational structure of nonlinear elastic waves. Thus we can identify whether materials satisfy the null condition by checking the stored energy function directly. Furthermore, by some careful analyses on the nonlinear structure, we show that the Helmholtz projection, which is usually considered to be ill-suited for nonlinear analysis, can be in fact used to show the global existence result. We also improve the amount of Sobolev regularity of initial data, which seems optimal in the framework of classical solutions.

Mechanisms and kinetics of gravity separation of granular materials

2020 ◽  
Vol 63 (6) ◽  
pp. 545-561
Author(s):  
V N Dolgunin ◽  
A N Kudi ◽  
M A Tuev
Keyword(s):  
Granular Materials ◽  
Gravity Separation ◽  
Kinetics Of

Toward the Analysis of the Structure of Granular Materials

2013 ◽  
Vol 58 (1) ◽  
pp. 32-39
Author(s):  
O.I. Gerasymov ◽  
◽  
A.G. Zagorodny ◽  
M.M. Somov ◽  
◽  
...  
Keyword(s):  
Granular Materials
Sign in / Sign up

Export Citation Format

Share Document