Laser Shock Experiments to Investigate Fragmentation at Extreme Strain Rates
Résumé
Laser‐driven shocks can be used to investigate the processes over ranges of very high strain rates, high loading pressures, small spatial scales and very short duration of pressure application. This chapter provides an overview of some experimental work on spall fracture, microspall and microjetting, involving complementary techniques including fast shadowgraphy, time‐resolved velocimetry, ultrafast in situ radiography and post‐recovery analyses of both samples and ejecta. Dynamic fragmentation is a safety issue for a variety of applications, such as pyrotechnics/high‐speed machining, in which materials and structures are subjected to high‐rate thermo‐mechanical loading. Laser‐driven shock experiments with appropriate instrumentation can be used to study dynamic damage and fragmentation at very high loading rates. The chapter presents examples covering a variety of materials including copper, tin, iron, single‐crystal magnesium and a bulk metallic glass, focus more specifically on the ballistic properties of shock‐generated fragments resulting from spall fracture, microspall after shock‐induced melting and microjetting from surface defects.