MODELING OF NONLINEAR VIBRATION PROBLEMS WITH FLUID FLOWS THROUGH PIPELINES

2018 ◽  
pp. 44-47
Author(s):  
F.J. Тurayev
Keyword(s):  
Differential Equations ◽  
Nonlinear Vibration ◽  
Viscoelastic Properties ◽  
Construction Material ◽  
Fluid Flows ◽  
Variable Coefficients ◽  
Algebraic Equations ◽  
Flowing Liquid ◽  
Vibration Problems

In this paper, mathematical model of nonlinear vibration problems with fluid flows through pipelines have been developed. Using the Bubnov–Galerkin method for the boundary conditions, the resulting nonlinear integro-differential equations with partial derivatives are reduced to solving systems of nonlinear ordinary integro-differential equations with both constant and variable coefficients as functions of time.A system of algebraic equations is obtained according to numerical method for the unknowns. The influence of the singularity of heredity kernels on the vibrations of structures possessing viscoelastic properties is numerically investigated.It was found that the determination of the effect of viscoelastic properties of the construction material on vibrations of the pipeline with a flowing liquid requires applying weakly singular hereditary kernels with an Abel type singularity.

Method of Testing of Sound Absorption Properties of Materials Intended for Ultrasonic Noise Protection

2013 ◽  
Vol 38 (2) ◽  
pp. 191-195 ◽  
Author(s):  
Dariusz Pleban
Keyword(s):  
Sound Absorption ◽  
Free Field ◽  
Tone Burst ◽  
Mineral Wool ◽  
Frequency Range ◽  
Absorption Properties ◽  
Open Cell Foam ◽  
Properties Of Materials ◽  
Cell Foam

Abstract Efficient ultrasonic noise reduction by using enclosures requires the knowledge of absorbing properties of materials in the frequency range above 4 kHz. However, standardized methods enable determination of absorption coefficients of materials in the frequency range up to 4 kHz. For this reason, it is proposed to carry out measurements of the sound absorption properties of materials in the free field by means of a tone-burst technique in the frequency range from 4 kHz to 40 kHz at angles of incidence varying from 0° to 60°. The absorption coefficient of a material is calculated from the reflection coefficient obtained by reflecting a tone-burst from both a perfectly reflecting panel and a combination of this panel and the sample of the tested material. The tests results show that mineral wool and polyurethane open-cell foam possess very good absorbing properties in this frequency range.

scholarly journals Determination of geometric accuracy and surface roughness of small parts of circular and square sections, obtained depending on the printer location in the working space using selective laser melting technology from steel grade 12KH18N10T

2019 ◽  
pp. 59-67
Author(s):  
I. V. Gorbatov ◽  
Y. A. Orlov ◽  
V. A. Antiufeev ◽  
T. V. Telgerekova ◽  
N. Y. Orlova
Keyword(s):  
Selective Laser Melting ◽  
Physical And Mechanical Properties ◽  
Steel Grade ◽  
Geometric Accuracy ◽  
Laser Melting ◽  
Working Space ◽  
Properties Of Materials ◽  
Number Of Publications ◽  
Small Parts

The introduction of additive technologies for the manufacture of parts will significantly improve the efficiency and mobility of production. The technology of selective laser melting has the greatest accuracy in the manufacture of metal and alloyed parts. There are a number of publications on the physical and mechanical properties of such products, which often exceed the properties of materials obtained by traditional technology, but there is no data on the geometric accuracy of manufacturing. This paper provides explicit data on geometric accuracy, depending on various factors.

scholarly journals DETERMINATION OF CREEP PARAMETERS IN LAYERS OF BUILDING COMPOSITES/SLUOKSNIUOTŲJŲ STATYBINIŲ KOMPOZITŲ VALKŠNUMO PARAMETRŲ NUSTATYMAS

1998 ◽  
Vol 4 (2) ◽  
pp. 101-108 ◽  
Author(s):  
Gediminas Marčiukaitis
Keyword(s):  
Force Action ◽  
Building Product ◽  
Creep Coefficient ◽  
Deformation Properties ◽  
Linear Creep ◽  
Modulus Of Deformation ◽  
Composite Product ◽  
Properties Of Materials ◽  
Creep Deformations

Various composite building products consisting of layers of different physical-mechanical properties being tied rigidly together are manufactured and used in construction. In many cases such products curve, become flaky, crack and their thermo-insulating capability suffers. It occurs because deformation properties are not adjusted, different layers of such products deform differently under the load. And the deformation effects the behaviour of the whole structure. A correct adjustment of deformations can be achieved with allowance for creep of different layers and of the whole composite. Determination of creep parameters—creep coefficient and specific creep—depends on the orientation of layers in respect of the direction of force action. When layers are situated transverselly in respect of the direction of action of forces (stresses), creep parameters of composite depend on creep parameters of materials of separate layers and on relative volumes of these layers. Creep deformations of a composite can be described by equations describing creep of individual layers. Appropriate equations and formulas ((17)-(25)) are presented for determining such deformations. When layers are parallel to the direction of stresses, redistribution of these stresses between layers takes place. Compression stresses increase in a layer with higher modulus of deformation and decrease in that with lower modules. Proposed equations (37)-(42) enable to determine redistribution of stresses between layers, the main creep parameters of composite, their modulus of deformations and creep deformations themselves when strength of a composite product is reached, E(t0)=E(t)=const and stresses produce linear creep. Such loading of a composite product is the most common in practice. Presented formulas ((46), (52)) and diagrams show that it is possible to design a composite building product or material with creep parameters given in advance by means of appropriate distribution of product layers, selecting ratios between layers and properties of materials.

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