A laser shock wave is a mechanical high-pressure impulse with a duration of a few nanoseconds induced by a high power laser pulse. We performed wave pressure measurements in order to build and check mathematical models. They are used for wave applications in material science, health, and defense, to list a few. Piezoresistive methods have been shown to be highly sensitive, linear, and highly appropriate for practical implementation, compared with piezoelectric methods employed in shock wave pressure measurements. In this work, we develop a novel method to obtain the sensitivity of a piezoresistive measurement system. The results shows that it is possible to use a mechanical method to measure pressure of a laser induced shock wave in nanosecond range. Experimental pressure measurements are presented.
Strengthening techniques allows enhance metal physical properties. Laser shock peening (LSP) technique consist in a surface treatment which a high power laser pulse induces a compressive residual stress field through mechanical shock waves, increasing hardness, corrosion resistance, fatigue resistance. In comparison with the shot peening technique, LSP is a method that allows precision controlling the laser incidence on the surface under treatment increasing the surface quality in the surface under treatment. In this work, mechanical shock waves are induced in aluminum and measure using two different experimental approaches. First, using a PVDZ sensors and secondly, strain gauges are used. Experimental results are presented.
The dynamic angle limited integrated scattering (DALIS) method has been developed to examine optically smooth reflective surfaces with well-defined form. The DALIS system shows advantages over the conventional angle-resolved scattering. We propose a new configuration and results in the DALIS method by using a spherical mirror as a collecting element of the scattered light from the surface of a sample under test. Furthermore, the proposed method improves the detection of the scattered light and is suitable to be applied in workshop inspection during optical polishing processes.
The aim of this work is to propose the use of printed acetate sheets as quasi-sinusoidal diffraction gratings, as low-cost
alternative gratings for application in non-invasive optical tests. Gratings were generated with Matlab® software and
made with various models of laser printers. A study of the discretization effects that depend on the symmetry in the
sample was included, gratings were placed in the entrance pupil of a positive lens (illuminated by a collimated plane
wave) to observe their Fourier transforms. It was found that diffraction patterns of various types of semi-sinusoidal
profiles were very close to that of sinusoidal gratings. Gradual change in the size of printed ink spots was observed in
more detail through a magnification of 40x. Additionally, an atomic force microscope was used to measure the
roughness average of the impressions as to observe the behavior of the ink on the acetate.
A push-broom imaging camera with time expansion, selected for its ability to generate images with high resolution and high radiometric signal, is described for accurate site-certification from space. The imaging system providing the high resolution imaging requires a sensor with an increased dwell time to generate a high radiometric signal. This may be accomplished by pointing the camera at each pixel for a longer interval of time than that available due to the sensor motion in the push-broom imaging configuration. This is referred to as the push-broom imaging with time expansion. The use of the camera with time expansion may be applicable to any remote sensing imaging problem that requires simultaneously high spatial resolution and a high level of radiometric signal. For surveying a Martian landing site, it is necessitated by the imaging from an autonomous orbiting sensor that's speed is determined by its orbit and the planet mass.