On thermoelastic deformation of a transversally isotropic medium in 3D construction printing

A three-dimensional dynamic model of a thermoelastic transversely isotropic medium is used to describe the thermoelastic deformation of materials with anisotropy of elastic properties with a selected direction of anisotropy. Such materials are layered and composite materials used in construction, mechanical engineering, aircraft and shipbuilding, soils in permafrost conditions, glaciers, as well as rocks (basalt, sandstone, marble, limestone, shale, and others). The study of this model, in particular, is relevant in connection with the use of 3D printers in construction. This is due to the fact that it is necessary to select the heating mode of the 3D printer head, in which cracks will not form during the cooling of the polystyrene concrete layers.We study this model using the group analysis methods, which is one of the most powerful and effective tools for obtaining exact solutions. The group stratification of the system of second-order differential equations defining this model is carried out. A system of first-order differential equations is obtained, which is equivalent to the equations of the original model. The solution describing a traveling wave for this system is obtained, that depends on arbitrary elements: parameters and function. For the specific sets of these elements, we study a deformation of a sphere and cube located inside a thermoelastic transversely isotropic medium with increasing time is found. The corresponding graphs are given.

Photo-acoustic response and optical features of 2D-TlGaSe2 and GaAs semiconductors

The paper focuses on investigation of the acoustic-optical properties of 2D-TlGaSe2 and GaAs semiconductors using laser pulses. We present the photo-darkening experiments performed by using CW light in spectral ranges below the band gap of TlGaSe2. The data provides evidence that photo-acoustic signals (PAS) for the above band gap are significantly stronger and linear in 2D-TlGaSe2 while they are distorted by nonlinear processes in isotropic GaAs. The comparison discloses characteristic parameters of TlGaSe2, namely a high factor and a negative sign in the refraction coefficient with pressure, a low absorption coefficient and absence of band filling; all guarantee stabile energy conversion by thermoelastic deformation mechanism. Below the band gap range, we found a new kind of PAS in TlGaSe2 on near surfaces. Likewise, we demonstrate that in such spectral range the giant Stark effect in TlGaSe2 is created by focused CW beams. The Stark effect produces local optical darkening which can provide explosion at extreme light power. Likely, both effects could be related to the planar stacking faults in 2D-TlGaSe2, which produce a spontaneous charge separation on layers.

SPECIFIC FEATURES OF OPTICAL FIBER CABLE OPERATION DURING TENSION AND CHANGE OF AMBIENT TEMPERATURE

This article examines the effect of longitudinal and thermoelastic deformation of an optical module on the technological reserve of an optical fiber. Analytical expressions are given for determining the lower limit of the technological margin of an optical fiber for various types of fiber-optic cable section along the axis.