Measuring system for monitoring the polydimensional deformation of superstructures of bridges and over-bridges

Bridges belong to critical structures. Therefore the geodetic monitoring of their stability should be performed during their operation. Correctly and qualitatively performed control over stability of the ready-built construction increases the term and the reliability of operation of the bridge and considerably increases the safety of its use. All over the world there is a tendency to increase the length of superstructures of bridges and to use widely the flexible constructions. This makes these structures even more sensitive to dynamic loads. Based on the concept of unfolding the laser beam in the horizontal plane, the methods and devices for measuring the polydimensional deformations of superstructures of bridges and over-bridges were developed. The article examines the methods and devices for measuring the polydimensional deformation of superstructures of bridges and over-bridges with the use of deployable optical laser systems for measuring the longitudinal deformation of superstructures and an ultrasonic sensor for measuring transverse deformation. The devices use lasers with continuous radiation of a beam of a certain wavelength. Optical collimators are arranged in series with the lasers. The spinner, for example, is an engine on the shaft of which there is a mirror or a prism with a reflecting face at an angle of 45° to the laser beam, or a rotating optical wedge, due to which the laser beam is deployed in a horizontal plane. All n sequentially arranged deformation sensors and an additional photodetector for the control of the deflection of the wire on which the ultrasonic sensor is installed, are made in the form of a line of elements of a certain length, and each photodetector has the same number of elements. Each element of the photodetector is made of a certain material that transmits a laser beam without any special interference. The devices can be used in the automated system of monitoring of the deformations of the bridge structure (ASDB), which will allow the quick control of their condition, displacements and deflections resulting from the external climatic influences, as well as the amplitude of oscillation of loads from the continuous traffic with non-cyclic long-term loading of superstructures of bridges and over-bridges.

Curing of Epoxy Resin DER-331 by Hexakis(4-acetamidophenoxy)cyclotriphosphazene and Properties of the Prepared Composition

The method of optical wedge revealed that the optimum temperature for compatibility of hexakis(4-acetamidophenoxy)cyclotriphosphazene (ACP) and DER-331 epoxy resin is in the range of 220–260 °C. The interdiffusion time of components at these temperatures is about 30 min. The TGA and differential scanning calorimetry (DSC) methods revealed the curing temperature of 280 °С for this composition. IR spectroscopy confirmed that the reaction between the resin and ACP is completed within 10 min. According to the DSC data, a glass transition temperature of 130 °С was estimated for the cured resin. Combustion test UL-94 demonstrated that the obtained material can be assigned to the fireproof category of V-0. Burning droplets were not formed during the burning. The coke formed during the combustion of samples possessed a dense and porous structure. The shape of pores is closed, while their size is in the range of 0.2–200 µm.

INTRACAVITY LARGE-SCALE HETEROGENEITY AND THEIR INFLUENCE ON RADIATION PARAMETERS OF POWERFUL LASERS

Large‑scale inhomogeneities occur in the optical resonator of a high‑power laser due to uneven redistribution of heat and errors in the alignment of the circuit. Such inhomogeneities can significantly affect the characteristics of laser radiation. The paper analyzes the effect of large‑scale phase inhomogeneities associated with the separation and thermal deformation of unstable resonator mirrors on the parameters of the laser radiation – the power and angular divergence. The numerical simulation of the unstable resonator in the di‑fractional approximation is carried out, on the basis of which the quantitative effect of phase aberrations such as optical wedge (separation) and spherical lens (thermodeformation) on the power and divergence of laser radiation depending on the main characteristics of the unstable resonator‑the Fresnel number and the magnification coefficient is determined. The results of experimental studies of the effect of separation on the radiation parameters of a 100‑kilowatt CO2 gas‑dynamic laser are presented. The results of the work should be taken into account in the structural‑parametric optimization of the resonator.