Multichannel Strain and Temperature Measurement System for Structural Elements

he paper describes a 32-channel system for studying full-scale structures developed with the use of the state-of-the-art components. It provides continuous long-term measurement of strains and temperatures up to + 350°C and accumulation and storage of measurement data. The system was used to record the elastic strains and temperatures of a welded joint of the hot collector to the PGV-1000 steam generator nozzle in the period between the preventive maintenances. The measurement results reveal a complex pattern of strain and temperature distribution different from the axisymmetric one.     

Isochoric Heat Capacity Measurements for 0.5 H2O+0.5 D2O Mixture in the Critical Region

The isochoric heat capacity C _V of an equimolar H₂O+D₂O mixture was measured in the temperature range from 391 to 655 K, at near-critical liquid and vapor densities between 274.05 and 385.36 kgm^–3. A high-temperature, high-pressure, nearly constant-volume adiabatic calorimeter was used. The measurements were performed in the one- and two-phase regions including the coexistence curve. The uncertainty of the heat-capacity measurement is estimated to be ±2%. The liquid and vapor one- and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from the experimental data for each measured isochore. The critical temperature and the critical density for the equimolar H₂O+D₂O mixture were obtained from isochoric heat capacity measurements using the method of quasi-static thermograms. The measurements were compared with a crossover equation of state for H₂O+D₂O mixtures. The near-critical isochoric heat capacity behavior for the 0.5 H₂O+0.5 D₂O mixture was studied using the principle of isomorphism of critical phenomena. The experimental isochoric heat capacity data for the 0.5 H₂O+0.5 D₂O mixture exhibit a weak singularity, like that of both pure components. The reliability of the experimental method was confirmed with measurements on pure light water, for which the isochoric heat capacity was measured on the critical isochore (321.96 kgm^–3) in both the one- and two-phase regions. The result for the phase-transition temperature (the critical temperature, T _{C, this work}=647.104±0.003 K) agreed, within experimental uncertainty, with the critical temperature (T _{C, IAPWS}=647.096 K) adopted by IAPWS.     

Estimation of the Characteristics of Multiflow Models with Fixed Number of Retrials

For the cases of overload and limited number of retrials of the blocked message, an algorithm for approximate evaluation of the service indices of the multiflow model of a digital line was presented. The calculation procedure is based on the assumption that the arrival of repeated calls is Poissonian, which enabled one to reduce the evaluation procedure to a loss model for which there exists an efficient algorithm to calculate the characteristics by the convolution algorithm.     

Tests of Sheet Materials for Structural Elements in Transverse Shear

An experimental procedure to evaluate the energy spent for fracture of a circular-clamped thin plate in transverse shear, induced by impact loading with a flat-face body, is briefly outlined. Test results for the specimens of the three materials: mild steel, thickness = 1.0 mm, a D16T aluminum alloy, = 0.75 mm, and a PA6 shock-resistant composite, = 2.0 mm, are given. The analysis of experimental and calculated stress-strain data (within the circular area between the clamping contour and the loading surface) demonstrates the qualitative relation between the energy spent for deformation to fracture and dynamic strength and plasticity. Test results allow one to compare different materials by the energy spent for their fracture under impact loading. The specific work of deformation in shear characterizes this value more comprehensively than that determined in flexure, induced by impact of a spherical body, and is applicable over an expanded range of loading rates.     

Effect of strain-heat treatment on the tendency for corrosion cracking of pipe steel under stress

Strain-heat treatment conditions were found to affect the overall properties and structural state of 06G1NDB steel, which in turn affect resistance of the steel to stress corrosion cracking. The technique used in this paper enables strain-heat treatment conditions to be ranked by their effect on stress corrosion cracking of type 06G1NDB steel. Type 06G1NDB steel was found to have relatively high resistance to stress corrosion cracking for all strain-heat treatment conditions studied. This arises out of the fact that the chemical composition of the steel and all strain-heat treatment conditions used led to the formation of steel structure with highly disperse grains, high homogeneity, and a lack of banding or well-defined structurally inhomogeneous zones (axial liquation).     

Simulation of high-density pulse current-induced stress relaxation

The phenomenological equation relating pulse current-induced relaxation of elastic tensile stresses to current density, initial stresses, and temperature is proposed. The equation allows approximation of experimental data on positive and negative tensile stress relaxation with the above parameters. Translated from Problemy Prochnosti, No. 2, pp. 113–120, March–April, 2007.     

Specific features of kinetics of molecular beam epitaxy of compounds in the GaN-AlN system

The effect of growth conditions (V/III ratio, substrate temperature) on the properties of materials in AlN-GaN systems is discussed. A concept of the growth of the AlN/AlGaN/GaN multilayer heterostructure, which provides the improvement of crystal quality and surface morphology of the layers, is suggested and realized. The improvement of the properties of GaN in the AlN/AlGaN/GaN/AlGaN multilayer heterostructure is confirmed by a considerable increase in electron mobility in the two-dimensional electron gas formed at the upper heterointerface GaN/Al_0.3Ga_0.7N.     

Self-similar solution of the problem of a strong explosion in a perfect gas. Lagrangian description

The problem of a strong one-dimensional explosion in a perfect gas has been considered. The analytical solution of self-similar equations describing the dynamics of the explosion and the propagation of a strong shock wave has been obtained in Lagrangian mass coordinates. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, pp. 83–89, January–February, 2007.     

Coal mixtures for coke production: Patent errors revisited

A recent patent regarding the preparation and composition of coal batch is analyzed.