Thermal transport in shock wave-compressed solids using pulsed laser heating.

B M La Lone,W D Turley,G Capelle,L R Veeser,G D Stevens

doi:10.1063/1.4886615

B M La Lone, W D Turley + Show 3 more

Open Access

https://doi.org/10.1063/1.4886615

Copy DOI

Abstract

A pulsed laser heating method was developed for determining thermal transport properties of solids under shock-wave compression. While the solid is compressed, a laser deposits a known amount of heat onto the sample surface, which is held in the shocked state by a transparent window. The heat from the laser briefly elevates the surface temperature and then diffuses into the interior via one-dimensional heat conduction. The thermal effusivity is determined from the time history of the resulting surface temperature pulse, which is recorded with optical pyrometry. Thermal effusivity is the square root of the product of thermal conductivity and volumetric heat capacity and is the key thermal transport parameter for relating the surface temperature to the interior temperature of the sample in a dynamic compression experiment. Therefore, this method provides information that is needed to determine the thermodynamic state of the interior of a compressed metal sample from a temperature measurement at the surface. The laser heat method was successfully demonstrated on tin that was shock compressed with explosives to a stress and temperature of ~25 GPa and ~1300 K. In this state, tin was observed to have a thermal effusivity of close to twice its ambient value. The implications on determining the interior shock wave temperature of tin are discussed.

Highlights

Dynamic compression techniques, such as plate impact, explosive detonation, and magnetically driven compression, are laboratory methods available for generating high stresses (>10 GPa) in millimeter-size or larger samples
A pulsed laser heating method was developed for determining the thermal transport properties of explosively compressed metals
Thermal effusivity is a useful quantity for shock wave temperature measurements because it relates the measured surface temperature to the bulk interior sample temperature, which differs because of heat flow across the interface

Summary

Introduction

Dynamic compression techniques, such as plate impact, explosive detonation, and magnetically driven compression, are laboratory methods available for generating high stresses (>10 GPa) in millimeter-size or larger samples. In a dynamic compression experiment, the interior longitudinal stress and volume of a shocked sample are usually calculated from velocity measurements of surfaces and interfaces. Emissivity measurements, interface temperatures have been determined with 20 K uncertainty with the pyrometric technique in dynamic compression experiments.2 It is the temperature in the interior of the sample that is the most useful for thermodynamic studies, and the interface temperature differs from the interior temperature for several reasons.. Following shock wave arrival is a gradual decrease in radiance caused by the time-dependent Taylor wave release in stress, which lowers the entire tin sample temperature. The recorded velocity profile mimics the shape of the stress release This underlying temperature-stress decrease is characteristic of explosively driven shock waves and is not caused by thermal conduction. The laser pulse arrives at 0.09 μs and causes additional heating of the tin surface, resulting in an abrupt increase in thermal radiance followed by radiance decay as the surface heat is conducted into the metal sample

Methods

Results

Discussion

Conclusion