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Using the previously constructed equations of the theory of the plane multi-layer beams with a thin-layer structure in thickness, based on a discrete-structural model, a linear problem on the formation of the initial (subcritical) stress-strain state in test specimens of a unidirectional laminated composites with the [90°]s structure was given in shear tensile-compression tests. A numerical method was developed for solving the formulated problem, based on the reduction of the original problem to a system of integro-algebraic equations and the construction of their solution by the method of finite sums. The properties of the constructed equations are investigated and numerical experiments are carried out on the basis of the developed method. It is shown that in the test specimens of the laminated composite of the considered structure at their tension (compression) in the direction across the fibers and in shear, predominantly normal tensile (compression) stresses are formed, which are constant along the length and width of the specimen, and the tangential stresses in these directions are variable. [ABSTRACT FROM AUTHOR]

The paper deals with the numerical solution of acoustic wave propagation plane problem. Being formed by sound source in a high-pressure chamber, the acoustic wave propagates through a deformable thin plate, which radiates the sound wave in a lowpressure chamber. The considered problem represents the mathematical modelling of the experimental setup used to find soundinsulating properties of thin-walled structures realized by the method of adjacent reverberation chambers in acoustic test laboratories. Based on two dimensional approximation of wave equations, two problem schemes are introduced. These problems differ in terms of sound source specification in the high-pressure chamber. Present study shows that both of the considered problems lead to virtually same results when determining the plate's sound reduction index. The results of theoretical and experimental investigations are compared. [ABSTRACT FROM AUTHOR]

In this paper, the coupled problem of planar acoustic wave propagation through the double-layer composite plate containing the second layer from damping material with high logarithmic decrement is examined. Aerohydrodynamic interaction between plate and external acoustic environment is defined by three-dimensional wave equations, whilst mechanical behaviour of doublelayered plate is examined with model based on classical Kirchhoff-Love's hypothesis. Exact analytical solutions are given for plates with simply supported edges. On the basis of given solutions, parameters for second layer, which lead substantially damping of plate vibrations are found in the case of acoustic loading at resonant modes. [ABSTRACT FROM AUTHOR]

Theoretical-experimental method is proposed in this paper for determining the logarithmic decrement of vibrations based on the measurement of tip amplitude of the flat cantilever test samples during their damped vibrations at first resonance mode. Significant effect of external aerodynamic forces on logarithmic decrement is observed. Extensive theoretical and experimental studies were performed on the aerodynamic component of damping of oscillated flat strip plates. For the assessment of its contribution to overall damping of test samples during their free vibrations, large number of numerical experiments were carried out on two dimensional flow dynamics around the plate, in the light of which an approximated empirical formula is found. Present study is also covering the method to identify the elastic properties and amplitude dependencies of logarithmic decrement on deformation in accordance with the data of physical experiments performed with various series of test samples. [ABSTRACT FROM AUTHOR]

On the basis of the linearized equations consistent theory of curvilinear bars the buckling problem of rectilinear short and long laminated fiber reinforced specimens under the three‐point bending conditions has formulated. Based on the method of finite sums in the embodiment of integrating matrices numerical method for solving the above problem has developed. It was shown that the failure of the composite specimens under the three‐point bending conditions is due to the implementation of non‐classical shear buckling mode. On the basis of the linearized equations consistent theory of curvilinear bars the buckling problem of rectilinear short and long laminated fiber reinforced specimens under the three‐point bending conditions has formulated. Based on the method of finite sums in the embodiment of integrating matrices numerical method for solving the above problem has developed. It was shown that the failure of the composite specimens under the three‐point bending conditions is due to the implementation of non‐classical shear buckling mode. [ABSTRACT FROM AUTHOR]