A torsion pendulum for the determination of shear modulus and damping around 1 Hz

A new approach to calculation of the dissipation of mechanical energy in the environment with turbulent viscosity based on determination of the shear modulus of velocity is proposed. As an example the dynamics of Hill vortex moved in such environment is considered. The vortex radius extends linearly with the distance covered and makes up about 13% from it.

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An experimental method for the investigation of rigid polyurethane foams in shear

Journal of Cellular Plastics ◽

10.1177/0021955x18782080 ◽

2018 ◽

Vol 54 (5) ◽

pp. 851-884

Author(s):

Ilze Beverte

Keyword(s):

Shear Modulus ◽

Polyurethane Foams ◽

Shear Displacement ◽

Test Material ◽

Experimental Investigations ◽

Plastic Foams ◽

Tension Tests ◽

Different Dimensions ◽

Porous Plastic

Widespread applications of rigid polyurethane and plastic foams lead to shear deformations. Therefore, methods for ensuring shear using experimental investigations are necessary, including the possibility of determining the shear modulus, strength and limit angle. Therefore, a device that allows investigating the shear properties of highly porous plastic foams was developed. The proposed device comprises a clip-on extensometer, commonly exploited in uni-axial compression/tension tests, for the determination of the shear displacement directly on the foams’ sample, on a measurement zone of certain dimensions and location. An innovative construction of the extensometer’s legs is elaborated, permitting to investigate the shear displacement field for different dimensions of the measurement zone. Precision of the device is examined by performing a penetration test on materials of different densities: (a) polyurethane foams and (b) wood. Technology for the production of isotropic polyurethane foams as a test material is described in detail. Experimental determination of shear modulus and strength of one and the same sample, in one and the same experiment is elaborated. Displacements in different zones of sample’s work beam are investigated. Experimental data are compared with the results of mathematical modelling and a good correlation is proved to exist.

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The Elastic Coefficients of the Theory of Consolidation

Journal of Applied Mechanics ◽

10.1115/1.4011606 ◽

1957 ◽

Vol 24 (4) ◽

pp. 594-601

Author(s):

M. A. Biot ◽

D. G. Willis

Keyword(s):

Nonlinear Systems ◽

Shear Modulus ◽

Physical Interpretation ◽

Compressible Fluid ◽

Elastic Solid ◽

Fluid Content ◽

Alternate Forms ◽

Elastic Coefficients ◽

Methods Of Measurement

Abstract The theory of the deformation of a porous elastic solid containing a compressible fluid has been established by Biot. In this paper, methods of measurement are described for the determination of the elastic coefficients of the theory. The physical interpretation of the coefficients in various alternate forms is also discussed. Any combination of measurements which is sufficient to fix the properties of the system may be used to determine the coefficients. For an isotropic system, in which there are four coefficients, the four measurements of shear modulus, jacketed and unjacketed compressibility, and coefficient of fluid content, together with a measurement of porosity appear to be the most convenient. The porosity is not required if the variables and coefficients are expressed in the proper way. The coefficient of fluid content is a measure of the volume of fluid entering the pores of a solid sample during an unjacketed compressibility test. The stress-strain relations may be expressed in terms of the stresses and strains produced during the various measurements, to give four expressions relating the measured coefficients to the original coefficients of the consolidation theory. The same method is easily extended to cases of anisotropy. The theory is directly applicable to linear systems but also may be applied to incremental variations in nonlinear systems provided the stresses are defined properly.

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