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This paper reviews earlier work and describes a photographic investigation of damage produced in glasses, polymers and crystals by Q-switched and non-Q-switched laser pulses. The cameras used in the study include a Wollensak Fastax WF3 camera, a Beckman & Whitley (model 189) rotating mirror camera, and a Beckman & Whitley (model 501) image converter camera. The formation of internal disc-type cracks with the non-Q-switched pulse was studied in detail. The use of these cracks for fracture energy studies is demonstrated. Photographic sequences show the production of micro-plasmas associated with damage, and stress waves formed during irradiation in both solids and liquids. A recent development is that of digital holography which adds phase and intensity information to the more conventional photographic techniques. This technique is used here to study laser ablation and wave propagation in water. The photographic data shows the processes taking place in the laser interaction with a wide range of materials and should be of interest to modellers. [ABSTRACT FROM AUTHOR]

High-speed photography has been used in Cambridge to study dynamic events since the 1940s. In the early years, Courtney-Pratt both developed and used such cameras. More recently, there has been interaction between camera manufacturers and the Cavendish, but the main emphasis has been on using high-speed photographic techniques to obtain data on explosive ignition and propagation, fracture and impact processes. In many situations, it is important to acquire data at both high time and high spatial resolution. Optical techniques which allow this are reviewed. Most recently, the interest has been in obtaining data from inside solids, including opaque ones. This has been made possible by fabricating samples to include a random array of dense particles on a plane within a specimen and then obtaining images using X-rays. [ABSTRACT FROM AUTHOR]

The application of speckle metrology to high strain rate materials characterisation, through the use of appropriate high-speed photography, provides an exciting opportunity for measurements to be performed on materials, and in loading configurations, which were not previously possible. In particular, a full understanding of the mechanical properties of inhomogeneous materials such as composites, geological and biological materials at high strain rates, requires more data than has previously been provided by the split Hopkinson pressure bar, which only gives a measure of average specimen response. Following from a separate paper by Siviour and Grantham describing the application of speckle metrology to the Hopkinson bar, this paper discusses recent experiments in which this application was used to make previously unobtainable measurements of specimen response. Results are presented from experiments performed on a polymer bonded explosive simulant and long polymer rods. These experiments were designed to evaluate the technique in a number of different configurations, as well as providing useful experimental data on these materials. In addition, we revisit the use of speckle metrology in the high strain rate Brazilian test. [ABSTRACT FROM AUTHOR]

Six fracture surfaces have been observed extending at velocities between c R (the Rayleigh wave velocity) and 1.3 c R in high-speed photographs of four diamond specimens. The diamonds were embedded in a transparent polymer and shocked in plate impact experiments. The measured velocities exceed limiting velocities proposed in theoretical and practical studies of single mode I cracks in diamond. The fracture surfaces probably extend by initiation and coalescence of multiple tensile fractures along a single cleavage plane. This mechanism is dependent on the suppression of cracks branching from the {111} growth plane in diamond and considers the population of flaws near a propagating crack tip. [ABSTRACT FROM AUTHOR]

Digital speckle radiography is a measurement technique which is capable of visualizing internal flow fields within an opaque material undergoing a ballistic impact. This recent development has been successfully applied to the study of polyester, cement, sand and glass targets. The technique is based on digital speckle photography but, instead of producing the required speckle pattern by traditional means, the specimen is seeded with a layer of X-ray opaque filings. By utilizing two X-ray heads and varying the delays and position of the seeded layer, a full three-dimensional displacement map can be built up. The theories behind the technique are introduced, and results presented from two-dimensional displacement measurements on sand subjected to rod impact and three-dimensional measurements of cement being impacted by a shaped charged jet. [ABSTRACT FROM AUTHOR]

Lithium fluoride in its single-crystal form is an interesting material for investigating the development of fracture by multiple liquid impact owing to its well characterized crystal structure. The development of fracture during liquid impact is attributed to the extension of short circumferential cracks produced around the loaded area by the passing Rayleigh stress wave after the impact event. The damage threshold of single-crystal lithium fluoride is developed using the Cavendish Laboratory's multiple impact jet apparatus as a result of identifying the characteristic fracture annulus associated with liquid impact during a controlled experimental procedure. The observation of damage produced in solids by liquid impact has practical significance in the problems with supersonic aircraft flying through rain and in the erosion of turbine blades moving at high speeds through wet steam. [ABSTRACT FROM AUTHOR]