Mechanical properties, strength physics and plasticity
Effect of infrared radiation on the plasticity of solid hydrogen
L. A. Alekseeva B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, Khar'kov
Abstract:
This paper reports on the first results obtained from the investigation of the effect of IR radiation on the low-temperature (1.8
$\le T\le$ 4.2 K) plasticity of solid hydrogen. It has been found that, when the samples are exposed to IR radiation, a drastic increment
$\Delta\varepsilon_{\mathrm{IR}}$ of the elongation per unit length
$\varepsilon$ (which was preliminarily achieved under a continuously applied mechanical stress
$\sigma=\operatorname{const}$) occurs without an increase in the temperature of the samples. It has been revealed that the effect observed both in the case of normal hydrogen (
$n$-H
$_2$, 75%
$o$-H
$_2$) and in the case of parahydrogen (
$p$-H
$_2$,
$\sim$0.2%
$o$-H
$_2$) only for a sufficiently high power of the IR radiation source has a threshold character. The reverse deformation of solid hydrogen is observed after the irradiation with a flux of IR photons is completed: the quantity
$\varepsilon$ rapidly decreases to values provided only by the applied load. The appearance of jumps in the increment of deformation
$\Delta\varepsilon_{\mathrm{IR}}$ is interpreted as a consequence of the existence of the fundamental IR absorption band for solid hydrogens. It has been established that, depending on the time
$t$ of exposure of the samples to IR radiation, the change in the quantity
$\Delta\varepsilon_{\mathrm{IR}}^i(t)$ obeys the logarithmic law, which is characteristic of the dislocation creep and observed in the case of unirradiated hydrogen. It has also been found that, under multiple relatively long-term exposure to IR radiation, the constant
$\alpha$ of the logarithmic creep of
$n$-H
$_2$ abruptly decreases, whereas the strength of both the
$n$-H
$_2$ and
$p$-H
$_2$ samples increases significantly, which indicates their explicit hardening (instead of the expected “superplastic” behavior due to the exposure to IR irradiation).
Received: 12.11.2010
Accepted: 22.03.2011
Fulltext:
PDF file (302 kB)
