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.

Thermal stress-focusing effect following rapid uniform heating of spheres and long cylindrical rods

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.

Crack patterns in cylinders explosively loaded at an hemispherical end

Fracturing of paraboloidal-ended Perspex rods explosively loaded in air and salt water

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.

https://repositorio-aberto.up.pt/bitstream/10216/64913/2/63485.pdf

Internal Fractures in Solids of Revolution Due to Stress Wave Focussing

Second reflections and spall formation in solid perspex spheres due to point explosive loading in air

https://repositorio-aberto.up.pt/bitstream/10216/64698/2/59154.pdf

S. T. S. Al-Hassani

Papers

Internal Fractures in Spheres Due to Stress Wave Focusing

Internal Fractures in Solids of Revolution Due to Stress Wave Focussing