النتائج (
العربية) 1:
[نسخ]نسخ!
When the first material is semitransparent to the laser wavelength (due to a crystalline structureor to the presence of pigments within their matrix), in establishing the energetic and geometricalcharacteristics of the heat source at the interface, a quantification of the laser beam scattering isnecessary. Since the use of classical approximation based on the Beer-Lambert law can lead toinaccurate results in the case of scattering media, a new approach is used. Its detail description is givenin previous works [8] [9]. Basically, it involves two steps: (a) based on measurements of thetransmitted intensity (in % from the incident one) for three thickness of the same semitransparentmaterial, the scattering characteristics of the media (particles diameter, the relative refractive index andthe particle concentration) are computed by applying an inverse algorithm. This allows obtaining anequivalent material which produces the same attenuation and broadening of the laser beam as the realone. In the second step, the laser beam profile within the semi-transparent material is determined byusing a numerical model based on Mie theory and Monte Carlo method.For the ABS plates, the measurements of the transmitted intensity (table 2) indicate anequivalent material having the following scattering characteristics: particle diameter d=0.46μm,relative refractive index nparticle/nmatrix=1.42 and particle concentration c=0.44%. Using thesecharacteristics as input data in the numerical model (Mie +Monte Carlo), the transmitted laser beamprofile was obtained. In spite the fact that the incident laser beam has a rectangular shaped profile witha uniform distribution of the energy (figure 3-a) the transmitted beam has an elliptical spot and aGaussian energy distribution (figure 3-b,c), the polymer acting like an optical filter. The characteristicradii (the radius where the laser beam intensity decreases with 1/e2) for the elliptical spot were rx=2.5mm and ry=2.69 mm
يجري ترجمتها، يرجى الانتظار ..
