scholarly journals Use of Electromagnetic Acoustic Resonance Method to Detect Micro-Voids Via Evaluation of Ultrasonic Wave Attenuation Coefficient of SUS304 Steel Fabricated by Hot Isostatic Press.

2001 ◽  
Vol 44 (1) ◽  
pp. 8-16
Author(s):  
Hidetaka NISHIDA ◽  
Hiroshi YAMAGUCHI ◽  
Masashi YOSHIDA
1997 ◽  
Vol 503 ◽  
Author(s):  
M. Hirao ◽  
H. Ogi ◽  
T. Ohtani ◽  
T. Morishita

ABSTRACTMethod of electromagnetic acoustic resonance (EMAR) was applied to the noncontact measurement of the shear wave attenuation during the creep test of 2.25Cr-1Mo steels. Two electromagnetic acoustic transducers were manufactured for this purpose, which generate the polarized shear waves through the magnetostriction effect. The attenuation coefficient increased with the creep deformation. The evolution range of the attenuation was beyond 0.1 μs−1 before the failure, which was much larger than the attenuation variation among the samples.


1983 ◽  
Vol 44 (C9) ◽  
pp. C9-337-C9-340 ◽  
Author(s):  
R. L. Smith ◽  
W. N. Reynolds ◽  
S. Perring

Author(s):  
V.I. Tarasevych ◽  
◽  
Yu.G. Gasan ◽  
V.B. Dolgoshey ◽  
◽  
...  

The paper considers the issues of studying the structure formation of binders during hardening to determine the optimal moments of mechanical action on gypsum concrete specimens, which makes it possible to optimize the technology of their impregnation with sulfur melt. The time dependence of the elastic modulus of a hardening, binder is its important physicochemical characteristic, since it is used to objectively identify the stages of structure formation, to simulate the processes occurring at each of the stages. It is noted that the method of acoustic resonance of bending vibrations, in the case of hardening binders, needs correction with respect to the measurement technique and interpretation of the results obtained. The kinetics of the resonance frequency of a sample consisting of a rigid cell and a dispersion poured into it is a function of the elastic properties of the cell, the dispersion itself, the contact zone of the dispersion with cell and therefore cannot be used for either qualitative or quantitative analysis of the kinetics of hardening. Taking into account the elasticity of cuvette is necessary to obtain reliable information. It has been established that in the presence of shrinkage or significant expansion of the binder, the study of structure formation by the resonance method should be carried out in plastic cuvettes. Regardless of shrinkage, the use of a cuvette requires compulsory consideration of its elastic properties. It is advisable to objectively distinguish the stages of structure formation on the basis of the kinetics of not the dynamic modulus of elasticity itself, but the rate of its change. The time dependence of the logarithmic damping decrement is also an important characteristic of the concrete structure. The studies carried out make it possible to obtain serogypsum composites with the necessary performance characteristics and to manufacture elements of architectural décor, wall fencing products of increased aesthetics, durability and reliability from them.


Geophysics ◽  
2007 ◽  
Vol 72 (1) ◽  
pp. D9-D19 ◽  
Author(s):  
Yaping Zhu ◽  
Ilya Tsvankin

Orthorhombic models are often used in the interpretation of azimuthally varying seismic signatures recorded over fractured reservoirs. Here, we develop an analytic framework for describing the attenuation coefficients in orthorhombic media with orthorhombic attenuation (i.e., the symmetry of both the real and imaginary parts of the stiffness tensor is identical) under the assumption of homogeneous wave propagation. The analogous form of the Christoffel equation in the symmetry planes of orthorhombic and VTI (transversely isotropic with a vertical symmetry axis) media helps to obtain the symmetry-plane attenuation coefficients by adapting the existing VTI equations. To take full advantage of this equivalence with transverse isotropy, we introduce a parameter set similar to the VTI attenuation-anisotropy parameters [Formula: see text], [Formula: see text], and [Formula: see text]. This notation, based on the same principle as Tsvankin’s velocity-anisotropy parameters for orthorhombic media, leads to concise linearized equations for thesymmetry-plane attenuation coefficients of all three modes (P, [Formula: see text], and [Formula: see text]).The attenuation-anisotropy parameters also allow us to simplify the P-wave attenuation coefficient [Formula: see text] outside the symmetry planes under the assumptions of small attenuation and weak velocity and attenuation anisotropy. The approximate coefficient [Formula: see text] has the same form as the linearized P-wave phase-velocity function, with the velocity parameters [Formula: see text] and [Formula: see text] replaced by the attenuation parameters [Formula: see text] and [Formula: see text]. The exact attenuation coefficient, however, also depends on the velocity-anisotropy parameters, while the body-wave velocities are almost unperturbed by the presence of attenuation. The reduction in the number of parameters responsible for the P-wave attenuation and the simple approximation for the coefficient [Formula: see text] provide a basis for inverting P-wave attenuation measurements from orthorhombic media. The attenuation processing must be preceded by anisotropic velocity analysis that can be performed (in the absence of pronounced velocity dispersion) using existing algorithms for nonattenuative media.


Author(s):  
Shank S. Kulkarni ◽  
Alireza Tabarraei ◽  
Pratik Ghag

Abstract This work studies the damping property of Nanocomposites through simulating wave propagation using the Finite Element Method (FEM). For this purpose Representative Volume Element (RVE) of the composite material is created using Random Sequential Absorption (RSA) algorithm. Damping property is represented using the wave attenuation coefficient. The matrix material is assumed to be isotropic visco-elastic in nature with randomly dispersed stiff elastic spherical fillers. In order to model mechanical imperfections at the boundary of fillers and matrix, the interphase layer is modeled surrounding the spherical fillers. Determining the thickness and stiffness of this interphase region is a challenging task. Therefore this study aims at investigating the effect of variation in thickness and stiffness values of the interphase region on damping property of whole composite using sensitivity analysis. Two specific cases with a volume fraction of 5 % and 8.6 % are selected for sensitivity analysis. It has been found that both the thickness and stiffness of the interphase region plays an important role in deciding the damping properties of the polymer composite. Value of attenuation coefficient is more sensitive to the thickness of interphase than stiffness and hence it is important to choose the value of thickness correctly for accurate predictions.


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