Development of crack under periodically pulsed laser radiation
Abstract
An experimental study of laser-induced crack development in polymer materials was made with a periodically pulsed low-power LTIPCh-8 laser irradiating oriented polymethyl methacrylate. The laser radiation was focused on specimens already containing microcracks in pulses of 1/600 W average power at a repetition rate of 50 Hz. The crack growth was tracked by means of high-speed photography. Data on the absorption wavelength and the crack diameter as functions of time indicate that they increase with time linearly and according to a half-power law respectively. These results fit a theoretical interpretation on the basis of laser energy-pulse characteristics and gas thermodynamics, assuming that crack growth is an isothermal process and that an ideal gas is generated in the crack space with no relaxation or change in the number of gas molecules during intervals between laser pulses. Mathematical analysis leads to a linear first-order differential equation of cracking kinetics whose solution confirms the experimental results. Experiments performed by Yu. V. Sidornyy indicate that a nearly ideal gas is generated in cracks during irradiation in periodic pulses.
- Publication:
-
JPRS Report Science Technology USSR Space
- Pub Date:
- June 1987
- Bibcode:
- 1987RpScT.......48G
- Keywords:
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- Crack Propagation;
- Laser Applications;
- Microcracks;
- Polymethyl Methacrylate;
- Pulsed Lasers;
- Ideal Gas;
- Thermodynamics;
- Lasers and Masers