Crack patterns in cylinders explosively loaded at an hemispherical end
01 Dec 1983-International Journal of Fracture (Springer Science and Business Media LLC)-Vol. 23, Iss: 4, pp 271-279
TL;DR: In this paper, the final crack and fracture damage found in hemispherically-ended "Perspex" (PMMA) rods loaded explosively by electrical detonators at their hemispherical end is described.
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.
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TL;DR: A combination of laboratory and numerical experiments examines the role of shear localization in subsurface damage following very oblique (15-30°) hypervelocity impacts as mentioned in this paper.
Abstract: A combination of laboratory and numerical experiments examines the role of shear localization in subsurface damage following very oblique (15–30°) hypervelocity impacts. Laboratory experiments reveal subsurface damage planes (“blades”) parallel to the impact trajectory for highly oblique impacts (15–30°), which are characterized by unique surface textures relative to other failure regions. Observations of growth rate and surface texture of the damage planes combined with three-dimensional CTH simulations indicate that the blades are the result of frictional processes during localized shear deformation. Laboratory experiments also reveal that impact angle and projectile failure play a role in the development of these blades: aluminum projectiles result in distinct along-trajectory blades for both 15° and 30° impacts, whereas the blades are weakly developed for Pyrex projectiles and nonexistent for planar polymethylmethacrylate projectiles. The blades form early in the cratering process and are signatures of the projectile momentum being transferred into the target. Based on the growth rate, and melting seen along the surface of these damage planes, the blades may provide an analog for the generation of pseudotachylytes during the early stages of impact crater formation.
4 citations
TL;DR: In this paper, crack and fracture damage in paraboloidal-ended cylindrical rods of Perspex due to stress waves initiated by explosive point loading at the flat end of a rod with a detonator is discussed and the controlling mechanisms are considered.
3 citations
TL;DR: In this article, 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 the energy distribution of incident waves when reflected from this boundary.
2 citations
01 Jan 1985
TL;DR: In this paper, the formation of cracks and fracture damage in solids of axisymmetric shapes subjected to surface explosive loading is described and the controlling mechanisms are considered. And the results are used to verify the predictions of ray theory.
Abstract: The formation of cracks and fracture damage in solids of axisymmetric shapes subjected to surface explosive loading is described and the controlling mechanisms are considered. High speed photography of model perspex specimens was employed to observe the initiation and growth of the internal fissures. The results are used to verify the predictions of ray theory. The location and the rate of growth of the cracks are found to depend mainly upon the geometry of the surface of the specimens. Solids of spherical, cylindrical, paraboloidal, hyperboloidal and elliptical shapes are considered.
1 citations
01 Jan 1986
TL;DR: In this paper, the interaction between elastic stress waves and static or running cracks, mixedmode crack propagation, dynamic contact of impacting bodies and stress wave focussing effects is discussed.
Abstract: High-speed recording techniques in conjunction with methods of photomechanics serve as a means for visualizing the highly complex interaction processes between elastic stress waves and geometrical discontinuities such as boundaries, interfaces, cracks and contact surfaces. Four topics of importance and general interest will be addressed here: the interaction between elastic stress waves and static or running cracks, mixed-mode crack propagation, dynamic contact of impacting bodies and stress wave focussing effects. Experimentally recorded isochromatic fringe patterns and sequences of caustics assist and confirm numerical and analytical computations.
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Book•
24 Sep 1993TL;DR: In this article, the authors present a unified continuum, microstructural and atomistic treatment of modern day fracture mechanics from a materials perspective, focusing on the basic elements of bonding and microstructure that govern the intrinsic toughness of ceramics.
Abstract: This is an advanced text for higher degree materials science students and researchers concerned with the strength of highly brittle covalent–ionic solids, principally ceramics. It is a reconstructed and greatly expanded edition of a book first published in 1975. The book presents a unified continuum, microstructural and atomistic treatment of modern day fracture mechanics from a materials perspective. Particular attention is directed to the basic elements of bonding and microstructure that govern the intrinsic toughness of ceramics. These elements hold the key to the future of ceramics as high-technology materials - to make brittle solids strong, we must first understand what makes them weak. The underlying theme of the book is the fundamental Griffith energy-balance concept of crack propagation. The early chapters develop fracture mechanics from the traditional continuum perspective, with attention to linear and nonlinear crack-tip fields, equilibrium and non-equilibrium crack states. It then describes the atomic structure of sharp cracks, the topical subject of crack-microstructure interactions in ceramics, with special focus on the concepts of crack-tip shielding and crack-resistance curves, and finally deals with indentation fracture, flaws, and structural reliability.
3,550 citations
Book•
01 Jun 1972TL;DR: In this article, a compilation of information and analytical methods on the subject of impact strength of materials is presented, dealing with elementary one-dimensional elastic stress waves in long uniform bars due to impact.
Abstract: This book presents a compilation of information and analytical methods on the subject of the impact strength of materials. It contains ten chapters dealing with: 1, elementary one-dimensional elastic stress waves in long uniform bars due to impact; 2, applications of elementary one-dimensional stress wave theory; 3, elastic stress waves: more general considerations; 4, plasticity theory and some quasi-static analyses; 5, one dimensional elastic-plastic stress waves in bars; 6, impulsive loading of beams; 7, dynamic loading of rings and frames; 8, dynamic plastic deformation of plates; 9, plastic deformation in a semi-infinite medium due to impact; and 10, plastic deformation in plates due to impact. Two appendices contain: 1, useful conversion factors; and 2, text tables in SI units. (TRRL)
646 citations
224 citations
TL;DR: In this article, a high speed photographic study has been made as part of a detailed investigation of the impact of small steel spheres (∼ 800 and 1000 μm diameter) on Pyrex and soda-lime glasses.
Abstract: A high speed photographic study has been made as part of a detailed investigation of the impact of small steel spheres (∼ 800 and 1000 μm diameter) on to Pyrex and soda-lime glasses. The velocity of the spheres was varied from 20 to 300 m sec−1 and the fracturing process during the complete impact cycle was followed. Observations revealed substantial differences in the behaviour of the two glasses, particularly at higher velocities; Pyrex behaved as though indented by a sphere, whereas soda lime glass behaved as though indented with a pointed indenter. As with quasi-static pointed indentations, cracking was observed during the unloading cycle. It was also found that the angle of the Hertzian cone crack in Pyrex glass varied in a systematic manner with velocity. Rebound velocity, time of contact and extent of flattening of the steel spheres were also recorded. The relevance of these observations to impact erosion and strength degradation of brittle materials is pointed out.
206 citations