Numerical Estimation of the Geometry of the Deposited Layers during Direct Laser Deposition of Multi-Pass Walls

Direct laser deposition (DLD) is a promising additive technology that allows for the rapid and cheap production of metal parts of complex geometry in various sectors of mechanical engineering. Thick-walled metal structures occupy a significant part in mechanical engineering. The purpose of this study was to develop and test an algorithm for predicting the geometry of deposited multi-pass walls. To achieve this goal, the main interrelated processes involved in the formation of a multi-pass wall were described—the process of laser radiation propagation, the process of heat transfer and the process of bead formation. To construct the calculation algorithm, five characteristic types of beads are identified. For these five types, the features of the bead formation and the features of the laser radiation intensity distribution are described. The calculated data were verified. A good match of the calculated data with the geometry of the deposited walls from AISI321 steel, Inconel718 and Ti-6Al-4V alloys was obtained.

The impact of laser-induced thermocoagulation effects on the optical spectra of brain tissues

In this work, the results of spectral and optical studies of the grey matter tissues of the brain by a laser hyperthermia action are presented. The coefficients of optical absorption and transport scattering in the spectral range of 250-1500 nm are determined, and the features of the spatial distribution of the laser radiation intensity in the studied objects are identified. It is shown that the coagulation effects lead to compaction and an increase in the concentration of endogenous chromophores and structural elements, which is reflected in the optical properties of biological objects.

Measurement of Silicon Nanoparticles Temperature by Raman Spectroscopy

The temperature of silicon nanoparticles under laser photo-induced heating is determined from the ratio of the intensities of the Stokes and anti-Stokes components of the Raman scattering. The obtained results of the dependence of nanoparticles temperature on the laser radiation intensity and the temperature dependence of the Raman line position maybe used to determine the optimal regimes of photo-hyperthermia enhanced by silicon nanoparticles for cancer therapy.

Фотоиндуцированная обратимая локальная деформация рельефа поверхности в объемных монокристаллах TlInSe-=SUB=-2-=/SUB=-, TlGaTe-=SUB=-2-=/SUB=- и TlSe

Giant macroscopic expansion of the surface relief, localized within a laser spot size, has been observed in bulk single crystals of TlInSe_2, TlGaTe_2, and TlSe at room temperature and laser radiation densities lower by at least two orders of magnitude than the material optical damage threshold. Quantitative estimations of the deformation magnitude in this local region were obtained using an interference dilatometer. The photon absorption length was determined with the aid of spectroscopic ellipsometry. It is established that the surface deformation amounts to 2.6 × 10^–3 at a laser radiation intensity of 19 mW/mm^2. The observed phenomenon has a thermal nature and is probably related to a low thermal conductivity of the materials studied.

Reconstruction of Function of Particles Distribution by Sizes with Laser Sensing Method Use

A laser sensing inverse task solution method without using of integral equations has been suggested in this paper and it can be used for aerosol particles’ sizes and concentration monitoring equipment creation for the real practice of the industrial production. This method is based on the laser radiation intensity weakening at a limited set of the probing laser radiation wavelengths. The computer simulation of aerosol flow parameters has been fulfilled and its results showed that during the regular operation of enterprise’s dust cleaner equipment at the certain point of the technological process the aerosol can be described by a function of particles distribution by sizes, and this function depends on finite number of parameters. The particles’ sizes distribution function is described by the logarithmic normal law after a fabric filter as a last step of the dust cleaner equipment. The laboratory setup realizing the laser sensing at the several laser radiation wavelengths possibilities simultaneously by the spectral transparency and integral light scattering methods for investigation of studied aerosol flows’ optical parameters dependence has been created. A complex refractive index of the studied substance has been investigated. The dependence between the logarithmic normal distribution function parameters and the average volume - surface diameter values received as a result of the sensing has been revealed. The suggested method of the inverse task solution can be developed for the dust gas cleaning equipment refusals detection.