Institute of Fundamental Technological Research

The article presents a study of shock waves induced by a nanosecond laser pulse in samples in the form of steel plates. Its contents include a description of the measurement system, methods of calculations and some characteristics of the measuring instruments and materials used. The quoted formulas enabled the processing of recorded measurement signals. The influence of material used as a confining layer (glass, PMMA - Plexiglass, water) and substrate (PMMA, aluminium, steel) on the amplitude and shape of recorded pressure waves was studied. Pressure behind the shock wave measurements were conducted using piezoelectric polymer PVDF (polivinylidene fluoride) sensors. Verifications of PVDF results were conducted by the measurements of velocity of back sample surface by VISAR (Velocity Interferometer System for Any Reflector). A qualitative compliance between the PVDF's pressure and VISAR's velocity rescaled to pressure was achieved. The strains (about 0.3%) and strain rates (about 3 × 10^5 1/sec) were evaluated. The obtained results will allow for a better selection of test conditions for studying material properties by using a shock wave induced by the laser pulse.

laser pulse, shock wave, PVDF sensor, VISAR

The laser spallation technique was applied for measurement of residual stress and adhesion of thin films. Two films of different properties, ductile and soft Ti, and hard and brittle TiN, were studied. The films were produced on 304 steel substrate by PVD method. The residual stress value obtained by laser spallation technique LST were compared with stress value from X-ray diffraction method. Good agreement of stress values measured by both methods was attained. Additionally, the interface strength of the films was tested by laser adhesion spallation technique LASAT with use of VISAR system. It was shown that shock wave induced by a nanosecond laser pulse adequately determines properties of PVD thin films on metal substrate

Laser spallation technique, Residual stress, Adhesion, Thin layer, PVD, VISAR system

The paper presents result of experimental and numerical tests of plastic deformation of austenitic steel generated by a nanosecond laser pulse. The shock wave generated by the laser pulse was used to induce local plastic deformation of the material. The study examined the possibility of using the process to develop a laser forming of materials under ultra-high strain rate. It has been shown that the laser pulse with intensity 2.5 GW/cm2 induces a repeatable plastic deformation of commercially available 304 steel without thermal effects on the surface

Laser pulse, Plastic deformations, Microstructure, Numerical simulations

Obok wielu różnych zastosowań, promieniowanie laserowe jest stosowane również szeroko w przemyśle do powierzchniowej obróbki różnych materiałów z wykorzystaniem procesów ablacji laserowej. Tematyka ta jest bardzo szeroka. Zespół autorów prowadzi od wielu lat badania nad zastosowaniem powierzchniowej obróbki laserowej w tak różnych obszarach jak konserwacja zabytków (czyszczenie laserowe) czy bioinżynieria (kształtowanie powierzchni implantów). W niniejszym artykule przedstawiono pewien wycinek prac zespołu, związany z opracowaniem laserowej metody badań adhezji cienkich warstw i laserową obróbką materiałów do zastosowań w mikro-przepływach i separacji komórek krwi. W pierwszym przypadku, padające na powierzchnię intensywne promieniowanie laserowe wytwarza silną falę uderzeniową w badanych materiale, pozwalającą określić progowe wartości uszkodzenia warstw technologicznych. Badania uzupełnione są przez modelowanie teoretyczne towarzyszących zjawisk fizycznych. W drugim przypadku uwagę zwraca możliwość separacji krążących komórek nowotworowych na laserowo wykonanych mikrositach, zawierających setki tysięcy otworów o średnicach na poziomie 10 μm na obszarach o obwodzie kilkunastu mm. Wymiary mikro-sit pozwalają na ich umieszczenie w układach mikro-przepływowych.

mikro-obróbka laserowa, fale uderzeniowe, grawerowanie szkła, cięcie szafiru, wytwarzanie mikrosit

This letter describes modelling and experimental results of low and high pressure shock waves (of the order of 100 and 1000 bar, respectively) induced by pulse laser radiation. Measurements were performed using piezoelectric polymer PVDF sensors. The results of numerical calculations and their comparison with an experiment have been posted. Measured and calculated results have been used in estimation of the temporary course of signals from a fibre VISAR interferometer which measured the movement velocity of a steel plate driven by the analysed shock waves. The description is supplemented with the results of magnitude measurements of surface plastic deformation and material microstructure of samples.