Study of Curing Processes in PDMS at Various Stoichiometric Ratios by Longitudinal Ultrasonic Waves

1989 ◽  
Vol 177 ◽  
Author(s):  
A. Shefer ◽  
G. Gorodetsky ◽  
M. Gottlieb
Keyword(s):  
Wave Propagation ◽  
Bulk Modulus ◽  
Longitudinal Wave ◽  
Wave Velocity ◽  
Ultrasonic Waves ◽  
Gel Point ◽  
Longitudinal Wave Velocity ◽  
Stoichiometric Ratios ◽  
Longitudinal Ultrasonic Waves

ABSTRACTCuring reactions of linear vinyl terminated poly(dimethylsiloxane) with a four functional hydride silane crosslinker at various stoichiometric ratios, were studied by wave propagation at ultrasonic frequencies. Longitudinal wave velocity was found to be sensitive to the covalent endlinking, and gel point in these systems.The observed changes in longitudinal wave velocity during the reaction are governed by changes in the bulk modulus of the system.

Longitudinal Wave Velocity in Auxetic Rods

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Teik-Cheng Lim
Keyword(s):  
Wave Propagation ◽  
Longitudinal Wave ◽  
Wave Velocity ◽  
Poisson’S Ratio ◽  
Propagation Model ◽  
Poisson's Ratio ◽  
Longitudinal Wave Velocity ◽  
Compressive Wave ◽  
Elementary Wave ◽  
Wave Propagation Model

This short brief develops a model for the velocity of longitudinal wave propagation in auxetic rods. Due to the large density change in auxetic solids and significant lateral deformation for Poisson's ratio between −1 and −0.5, this note takes into consideration density correction and lateral inertia. Results show that deviation from the elementary wave propagation model becomes more significant the more the Poisson's ratio of the rod material deviates from 1/4, in which the deviation of wave velocity is insignificant for Poisson's ratio in the positive range, but significant in the negative range. Specifically, the tensile and compressive wave velocity increases and decreases, respectively, for Poisson's ratio less than 1/4, but this trend reverses for Poisson's ratio greater than 1/4. In addition to showing that the elementary wave propagation model is invalid for describing the longitudinal wave velocity in auxetic rods, the results also suggest that auxetic materials are useful for applications that require slowing down and speeding up of compressive and tensile wave propagations, respectively.

Determining the Thermal Shock Elastic Behavior of Mullite Ceramic Regenerator Material by Ultrasonic Testing

2014 ◽  
Vol 633 ◽  
pp. 472-475 ◽  
Author(s):  
Tian Tian Sun ◽  
Yan Xia Wang ◽  
Hai Yun ◽  
Dong Huan Zhang ◽  
Qing Hui Shang
Keyword(s):  
Thermal Shock ◽  
Longitudinal Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Temperature Difference ◽  
Shear Wave Velocity ◽  
Modulus Of Elasticity ◽  
Longitudinal Wave Velocity ◽  
Mullite Ceramic ◽  
Mullite Ceramics

Mullite material is a material commonly used in honeycomb regenerator, because in the process of using material under big temperature difference effect, so have a great demand for its thermal shock resistance. The used mullite ceramics were made by the direct solid phase sintering method, and the modulus of elasticity of the mullite ceramics measured by ultrasonic pulse-echo method in a thermal shock and thermal fatigue experiment, respectively. In the air-cooling condition, the study found the mullite ceramic without thermal shock that the longitudinal wave velocity and shear wave velocity respectively 3970(m/s) and 2492(m/s). After 45 times thermal shock of temperature difference of 800°C, longitudinal wave velocity and shear wave velocity decreased to 3910(m/s) and 2457(m/s), and the value of the modulus of elasticity changed 1020MPa. By observing the change of the elastic modulus value rule, can know the elastic deformation of thermal shock on the material performance of thermal shock damage. Moreover, the results can provide the data basis for the calculation of the residual strength and the numerical simulation of thermal stress.

Ultrasonic Study on Crystal Orientation Effects Upon Point Defect Growth Caused by Cross Slip Under Plastic Deformation

2004 ◽  
Author(s):  
Michiaki Kobayashi
Keyword(s):  
Plastic Deformation ◽  
Longitudinal Wave ◽  
Wave Velocity ◽  
Crystal Orientation ◽  
Pure Shear ◽  
Cross Slip ◽  
Polished Surface ◽  
Longitudinal Wave Velocity ◽  
Velocity Change ◽  
Change Tendency

Concerned with the longitudinal wave velocity changes under plastic deformation in pure shear state, the experimental results of longitudinal wave velocity are categorized to two types: (i) simple decreasing change tendency at polished surface specimens, and (ii) chaotic change tendency at unpolished surface specimens. In the present paper, the effects of surface roughness and crystal orientation on the amount of cross slip under plastic deformation are studied via finite element polycrystal model (FEPM) from the viewpoint of longitudinal wave velocity change showing a sensitive response to the point defects caused by cross slip.

Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO3at Low Temperatures Using Picosecond Ultrasound Spectroscopy

2012 ◽  
Vol 51 (7S) ◽  
pp. 07GA09 ◽  
Author(s):  
Akira Nagakubo ◽  
Akihiro Yamamoto ◽  
Kenichi Tanigaki ◽  
Hirotsugu Ogi ◽  
Nobutomo Nakamura ◽  
...  
Keyword(s):  
Longitudinal Wave ◽  
Wave Velocity ◽  
Low Temperatures ◽  
Longitudinal Wave Velocity
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