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Journal ArticleDOI

Internal Fractures in Spheres Due to Stress Wave Focusing

01 Jan 1977-International Journal of Solids and Structures (Pergamon)-Vol. 13, Iss: 11, pp 1007-1017

Abstract: The locations and times of occurrence of internal fractures in Perspex spheres subjected to localized explosive loading are investigated. An analysis of stress wave reflection from free boundaries based on the method of geometrical acoustics is found to give predictions which are in good agreement with results obtained from high speed photographs.
Citations
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Journal ArticleDOI
Abstract: Stress waves that develop following the rapid uniform heating of linear-elastic spheres and long cylindrical rods display a stress-focusing effect as they proceed radially toward the center in these geometries. The stress-focusing effect is the phenomenon that, under a rapid uniform heating, stress waves reflected from the free surface of the spheric or the cylindrical rod result in very high stresses at the center even though the initial thermal stress might be relatively small. This phenomenon may be observed in the solid spheres subjected to the spherical symmetric heating and in the cylindrical rods subjected to the cylindrical symmetric heating. This type of heating may be caused by the absorption of infrared rays radiation or electromagnetic radiant energy. This article reviews recent extensions of the analytical methods for the problem of thermal shock in spheres and cylindrical rods, especially for the problem of the thermal stress-focusing effect in spheres and cylindrical rods. First, considering the problem of thermal shock in a hollow sphere subjected to the rapid uniform heating, if the ratio of the outer radius to the inner radius of the sphere increases, the peak tangential stress at the internal surface becomes higher and higher. In the limit case, for a solid sphere, it might be possible to observe the stress-focusing effect. Next, as for the analysis of a cylindrical rod due to the rapid uniform heating, stress waves also show the stress-focusing effect. Hence, the major accomplishment of this study is in gaining a better understanding of the thermal stress-focusing effect in solid spheres and cylindrical rods.

13 citations


Journal ArticleDOI
D. J. Williams1, B. J. Walters1, W. Johnson1Institutions (1)
Abstract: The final crack and fracture damage found in hemispherically-ended ‘Perspex’ (PMMA) rods loaded explosively by electrical detonators at their hemispherical end is described. The mechanisms of the formation of the major features are also considered.

5 citations


Book ChapterDOI
01 Jan 1981
Abstract: Internal fractures in spherical, paraboloidal, hyperboloidal and elliptical solids subjected to concentrated surface explosive loading are investigated. The initiation and growth of the internal fractures are associated with the focusing effect of P and S wave fronts reflected from the curved boundaries. High speed photography on perspex specimen is used for the verification of predictions of simple methods of geometrical optics and propagation of discontinuities. The speed with which these internal fractures grow are found to depend upon the geometry of the surface of the solid.

2 citations


Journal ArticleDOI
Abstract: Spall development in perspex spheres due to stress waves initiated by explosive point loading from a detonator in a medium of atmospheric air is discussed. An attempt has been made to explain the form and the location of the spalls in terms of stress wave optics considering first and second reflections of the incident waves at the spherical boundary and in terms of the energy distribution of the incident waves when reflected from this boundary.

2 citations


Journal ArticleDOI
V. I. Kovtun1, Myroslav Karpets1, V. V. Garbuz1, S. M. Zakharov1  +4 moreInstitutions (1)
Abstract: Powders TiO2, CuO, Cu2O, and CoO mixed with inert filler are subjected to shock waves in cylindrical preservation devices. The shock waves are generated by the explosion of TG40 charge at a detonation speed of 7.8 km/sec and detonation wave pressure of 28 GPa. It is established that shock-wave processing of oxide powders leads to changes in particle-size distribution since coarse and medium particles are crushed, coherent scattering regions become smaller, and concentration of phase distortions increases. Phase transformation of rutile into denser orthorhombic modification occurs in TiO2, and the content of phases with higher oxygen amount increases in Cu2O and CoO.

1 citations


Cites background from "Internal Fractures in Spheres Due t..."

  • ...According to [8, 9 ], shock waves are reflected from the free surface of particles in spherical bodies and they disintegrated at places where these waves are located....

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References
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Journal ArticleDOI
T. C. T. Ting1, E. H. Lee2Institutions (2)
Abstract: : The propagation of an initially sharp plane pressure pulse through a linear elastic composite medium is analysed. Wave front and ray theory analogous to geometrical optics is shown to determine the change in shape of the leading wave front and also the stresses immediately behind it. For certain circumstances the stress amplitudes on this front, or the corresponding tensile stresses on its reflection at the free back surface of a slab, may be critical in design. Examples are presented of an initially sharp plane pressure pulse transmitted through an elastic circular cylinder and an elastic spherical inclusion. The method can be applied to more general composite configurations, and can be extended to determine the stress gradient behind the front. For the latter, general formulae are derived by which the reflection and transmission coefficients can be determined for the stress gradient and the higher order derivatives at an arbitrary interface.

19 citations


Journal ArticleDOI
Abstract: : Separation at the interface of a circular inclusion embedded in a matrix of lower characteristics impedance and subjected to incident compressive waves is investigated, both experimentally and analytically. In the experiment, the compressive waves were generated by small explosive charges. The qualitative analytical treatment is based on the methods of propagating stress discontinuities. It is shown that a compressive stress wave is converteed into a tensile wave after a refraction and a reflection inside the inclusion. The results of this paper apply to the behavior of fiber-reinforced composites under dynamic loading conditions. (Author, modified-PL).

16 citations


Journal ArticleDOI
Abstract: The internal fracturing of a Perspex sphere due to a localised explosive loading on its surface has been investigated both analytically and experimentally. The locations and times of occurrence of the fractures are predictable from an analysis of stress wave reflection from the free surface based on the methods of geometrical acoustics. High-speed photography was used to measure and note the order in time at which the different fractures occurred.

15 citations


Journal ArticleDOI
E. Lovell1, S.T.S. Al-Hassani2, W. Johnson2Institutions (2)
Abstract: The results of an experimental study of the fracture of solid spheres and circular disks due to the explosion of a detonator on the surface are presented and a simple analysis is developed which reasonably explains the nature of the characteristic fracture patterns encountered.

14 citations


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