Shock wave decay and spall strength in laser-matter interaction

International audienceDynamic fragmentation of shock-loaded metals is an issue of considerable importance for both basic science and a variety of technological applications, such as inertial confinement fusion, which involves high energy laser irradiation of thin metallic shells. In this context, we present an experimental and numerical study of debris ejection in laser shock-loaded metallic targets (aluminum, gold, and iron) where fragmentation is mainly governed by spall fracture occurring upon tensile loading due to wave interactions inside the sample. Experimental results consist of time-resolved velocity measurements, transverse optical shadowgraphy of ejected debris, and postshock observations of targets and fragments recovered within a transparent gel of low density. They are compared to numerical computations performed with a hydrodynamic code. A correct overall consistency is obtained

Section: Introductionmentioning

confidence: 99%

Ejection of spalled layers from laser shock-loaded metals

Lescoute¹,

Rességuier²,

Chevalier³

et al. 2010

“…11,12 This diagnostic technique provides an accurate, continuous measurement of the surface velocity, which has the advantage of not interfering with the motion of the shocked target. Before the introduction of time resolved interferometry for measuring the dynamic fracture, many of the experimental studies on laser driven spallation 13 were based on the examination of recovered samples. However, this last method imposes certain limits on the loading pressures and strain rates that can be explored.…”

Section: Introductionmentioning

confidence: 99%

Measurements of laser driven spallation in tin and zinc using an optical recording velocity interferometer system

Moshe¹,

Eliezer²,

Dekel³

et al. 1999

Self Cite

Measurements of the dynamic strength, in tin and zinc, shocked by a high power pulsed laser to tens of kilobars pressures are reported. The strain rates in these experiments are of the order of 107 s−1, higher by two-to-three orders of magnitude than those reached with conventional shock generators like plane impacts or explosives. The free surface velocity time history, which is related to the spallation process, was measured with an optical recording velocity interferometer system. This diagnostic technique is noninterfering and provides a highly accurate continuous measurement in time. The spall strength estimated from the free surface velocity profile was compared with the theoretical upper limit for the spall strength, calculated from a wide range equation of state for metals.

“…One of them is spallation, which has been studied for decades, using plate impact, detonation of explosive device, 1,2 and more recently, energy deposition by high-power proton beam 3 or pulsed laser. [4][5][6][7][8] The latter technique has the advantage to be less destructive than the other methods. It consists in focusing a high-power laser pulse on the target set in a vacuum chamber.…”

mentioning

confidence: 99%

Skew photonic Doppler velocimetry to investigate the expansion of a cloud of droplets created by micro-spalling of laser shock-melted metal foils

Loison

Rességuier

Dragon

et al. 2012

International audienceDynamic fragmentation in the liquid state after shock-induced melting, usually referred to as micro-spallation, is an issue of great interest for both basic and applied sciences. Recent efforts have been devoted to the characterization of the resulting ejecta, which consist in a cloud of fine molten droplets. Major difficulties arise from the loss of free surface reflectivity at shock breakout and from the wide distribution of particle velocities within this cloud. We present laser shock experiments on tin and aluminium, to pressures ranging from about 70 to 160GPa, with complementary diagnostics including a photonic Doppler velocimeter set at a small tilt angle from the normal to the free surface, which enables probing the whole cloud of ejecta. The records are roughly consistent with a one-dimensional theoretical description accounting for laser shock loading, wave propagation, phase transformations, and fragmentation. The main discrepancies between measured and calculated velocity profiles are discussed in terms of edge effects evidenced by transverse shadowgraphy