B. J. Walters

Bio: B. J. Walters is an academic researcher from University of Cambridge. The author has contributed to research in topics: Fracture mechanics. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

Crack patterns in cylinders explosively loaded at an hemispherical end

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.

Discrete shear failure planes resulting from oblique hypervelocity impacts

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.

Fracturing of explosively loaded solids

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.

Topics in Photomechanics

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.