Unloading Wave in a Cylindrical Net

2019 ◽  
Vol 54 (8) ◽  
pp. 1138-1143
Author(s):  
J. H. Agalarov ◽  
T. J. Gasanova ◽  
G. A. Mamedova
Keyword(s):  
Unloading Wave

Elastic Waves Created During Tensile Fracture: The Phenomenon of a Second Fracture

1953 ◽  
Vol 20 (1) ◽  
pp. 122-130
Author(s):  
Julius Miklowitz
Keyword(s):  
Cross Sections ◽  
Tensile Tests ◽  
Analog Computer ◽  
Tensile Fracture ◽  
Strain Waves ◽  
Unloading Wave ◽  
Second Fracture ◽  
Wave Compression ◽  
Initial Fracture ◽  
The Moment

Abstract In some tensile tests with brittle materials, it was noted that fractures were produced at two different cross sections of the specimen when the rupture load was reached. The phenomenon of the second fracture prompted the present investigation. It is believed that the second fracture is caused by the destructive action of the elastic strain waves created during the first of the two fractures. The analytical and experimental work carried out was focused on describing the character of these waves. Consideration of the mechanics involved reduces the problem to that of a vibrating cantilever beam with time-dependent boundary conditions. Two types of waves are shown to exist. The first is a longitudinal unloading wave (compression). The other is a group of flexural strain waves caused by the moment that develops at the initial fracture section. The methods of operational mathematics and the electric-analog computer have been employed in the analytical study.

Velocity of an elastic unloading wave in steel

1986 ◽  
Vol 18 (9) ◽  
pp. 1225-1228
Author(s):  
G. V. Stepanov ◽  
V. I. Zubov
Keyword(s):  
Unloading Wave ◽  
Elastic Unloading

Finite elastic wave propagation in rubber

1963 ◽  
Vol 272 (1350) ◽  
pp. 315-330 ◽  
Keyword(s):  
Wave Propagation ◽  
Natural Rubber ◽  
Essential Feature ◽  
Finite Amplitude ◽  
Force Extension ◽  
Synthetic Rubber ◽  
Unloading Wave ◽  
Wave Forms ◽  
Fixed End ◽  
Relevant Range

A detailed experimental study has been made of the free retraction which occurs when one end of a stretched rubber filament is released. The essential feature of the retraction process is the passage of an unloading wave of finite amplitude from the point of release to the fixed end of the filament. Cine films taken at 2500 frames per second showed that for natural rubber the unloading wave proceeded without dispersion at a velocity increasing from about 40 m/s for low extensions to 85 m/s at an extension of 300 %; at higher extensions the unloading wave showed dispersion, the initial stages of unloading proceeding several times more rapidly than the later stages. A hysteretic synthetic rubber (butyl rubber) showed considerable dispersion even for low extensions. An explanation of the observed phenomena is given from which it follows that finite wave-propagation without dispersion is a consequence of the linearity of the force-extension relation in the relevant range of strain. As a test of the theory the technique is modified to demonstrate that (i) unloading waves of different wave forms show no dispersion in natural rubber at extensions up to 250 %. (ii) the predicted dispersion of both stress and strain waves is in agreement with observation, and (iii) the predicted behaviour of a rubber strip on loading by displacing one end at constant velocity is in agreement with observation. A method is proposed for obtaining load-extension relations at high rates of strain using microflash photography.

Boiling liquid model

2020 ◽  
Author(s):  
В.С. Суров
Keyword(s):  
Speed Of Sound ◽  
Liquid Fraction ◽  
Analytical Formula ◽  
Saturation Temperature ◽  
Vapor Concentration ◽  
Characteristic Analysis ◽  
Boiling Liquid ◽  
Nodal Method ◽  
Unloading Wave ◽  
Differential Relations

Представлена модель вскипающей жидкости, построенная на базе ранее предложенной автором обобщенно-равновесной модели смеси. В модели учтена сжимаемость жидкой фракции. Проведен характеристический анализ уравнений модели и показана их гиперболичность. Приведены расчетные формулы узлового метода характеристик, с использованием которого рассчитано течение при распаде произвольного разрыва во вскипающей жидкости. A model of a boiling liquid is presented, built on the basis of a one-speed two-temperature mixture model previously proposed by the author, in which the forces of interfractional interaction are taken into account. The liquid fraction was considered compressible. A characteristic analysis of the equations of the model is carried out and their hyperbolicity is shown. Relations for characteristic directions and differential relations along these lines are written. An analytical formula for calculating the speed of sound in a boiling liquid is obtained. It is noted that the speed of sound in a liquid when taking into account phase transformations is somewhat lower than is predicted by the Wood formula. The calculation formulas of the iterative algorithm of the nodal method of characteristics are presented, which implies that the flow is calculated during the decay of an arbitrary rupture in a boiling liquid. In the calculations, it was assumed that the phase transition during the boiling process occurs under conditions of an overheated state, when the temperature of the liquid exceeds the saturation temperature. It is shown that taking phase transformation into account leads to a significant increase in the vapor concentration in the unloading wave, as well as to a small increase in both the speed of the mixture and pressure. The concentration of the vapor fraction behind the shock front decreases.

scholarly journals Mechanochemical mechanism for reaction of aluminium nano- and micrometre-scale particles

2013 ◽  
Vol 371 (2003) ◽  
pp. 20120215 ◽  
Author(s):  
Valery I. Levitas
Keyword(s):  
Diffusion Mechanism ◽  
Quantitative Agreement ◽  
Oxide Shell ◽  
Fast Reaction ◽  
Fast Heating ◽  
Current Trends ◽  
Dispersion Mechanism ◽  
Unloading Wave ◽  
Theoretical Predictions ◽  
Hoop Stresses

A recently suggested melt-dispersion mechanism (MDM) for fast reaction of aluminium (Al) nano- and a few micrometre-scale particles during fast heating is reviewed. Volume expansion of 6% during Al melting produces pressure of several GPa in a core and tensile hoop stresses of 10 GPa in an oxide shell. Such stresses cause dynamic fracture and spallation of the shell. After spallation, an unloading wave propagates to the centre of the particle and creates a tensile pressure of 3–8 GPa. Such a tensile pressure exceeds the cavitation strength of liquid Al and disperses the melt into small, bare clusters (fragments) that fly at a high velocity. Reaction of the clusters is not limited by diffusion through a pre-existing oxide shell. Some theoretical and experimental results related to the MDM are presented. Various theoretical predictions based on the MDM are in good qualitative and quantitative agreement with experiments, which resolves some basic puzzles in combustion of Al particles. Methods to control and improve reactivity of Al particles are formulated, which are exactly opposite to the current trends based on diffusion mechanism. Some of these suggestions have experimental confirmation.

Melting and evaporation of metals in an unloading wave

1975 ◽  
Vol 15 (3) ◽  
pp. 417-420 ◽  
Author(s):  
A. A. Leont'ev ◽  
V. E. Fortov
Keyword(s):  
Unloading Wave
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