Effect of Microstructure on the Accelerated Creep of 20CrMoV12‐1 and P 91 Steels

In the initial part the change of microstructure for steel X20 CrMoV 121 is discussed in terms of the distribution of carbide precipitates and its effects on accelerated creep resistance and hardness are presented. In the following, experimental results of microstructure and accelerated creep resistance are presented for the steels X20CrMoV 121 and P91 annealed for up to 8760 hours at 650°C and 750°C before the testing. A similar evolution of the distribution of carbide particles of a size above 102 nm is found for both steels, while the accelerated creep resistance is diminished much stronger for the steel X20CrMoV 121. This difference is due to a greater stability of NbC than that of VC precipitates, both related to the evolution of the chemical composition of complex chromium, molybdenum and iron carbide particles.     

Effect of noise on the estimate of invariants in problems of strength inspection via the acoustic-emission method

The effect of low-intensity noise on the estimate of the probability characteristics of the results of measuring the intervals between acoustic-emission events is considered. Analytic relationships for the probability density of this interval are obtained. Expressions for the invariants with allowance for noise are deduced on the basis of these relationships and allow analysis of the regularities of the influence of noise on the estimates of invariants, elaboration of recommendations for constructing the interval-measurement process, and analysis of particular calculation cases.     

Optical loss of metal coated optical fibers at temperatures up to 800°C

Temperature band of ordinary telecommunication optical fibers is −60...85°C. The developing fiber optic sensors which can work at higher temperatures, required to develop metal coated optical fibers. The Purpose of the work is a researching additional optical loss of copper alloy coated optical fibers which were drawn from low hydroxyl group contamination preforms at temperatures 20...800°C. It is reached that metal coated optical fiber worked at temperature 700°C for 7 hours, while the optical losses changed from 2 to 3 dB/km at the wavelength of λ = 1300 nm. It is not observed intensive growth of optical losses on hydroxyl groups at 800°C, which was observed in metal coated optical fiber when it was heated at 700°C.     

Production of high-alumina cement clinker by fusion in an electric furnace

Conclusions The possibility of obtaining clinker from high-alumina cement by melting a mixture of lime and technical alumina in an electric-arc furnace at the Klyuchevsk Ferroalloy Plant has been shown.The high-alumina cement obtained from fused clinker is significantly better in its physicochemical properties than the cement produced on the basis of the lime-alumina slags from the ferroalloy industry.Translated from Ogneupory, No. 5, pp. 25–27, May, 1984.     

On the critical molecular chain length of polydimethylsiloxane

Because a study of the results reported for the chain dimensions of polydimethylsiloxane (PDMS), critical for the onset of this polymer's non-Newtonian flow behavior, obtained from the viscosity-molecular weight relationships available from the literature, clearly revealed that considerable differences exist between the reported data, a detailed analysis of these data was performed together with an additional examination of 10 new PDMS samples that were selected so as to have molecular weights that would fill the gaps observed in the polymer viscosity–chain length relationship constructed from the accepted literature data. The results obtained were analyzed by using several different procedures integrated into a recently described comparative method that could allow for determination of what is called the most realistic critical value, Z_wc. The latter was determined as 930 PDMS main-chain atoms, which corresponds to this polymer's degree of polymerization of 464.5 and the weight-average molecular weight of 34,500. It is not only shown that after elimination of some clearly erroneous data points from the previously reported relationships the obtained critical chain-length values could very well fit the earlier relationships, but also that appropriate “master” relationships were constructed including 48 pairs of the old and 10 pairs of the new data points. It is suggested that this relationship be accepted as the best-fit viscosity–polymer chain-length dependence for PDMS, and it is pointed out that the obtained PDMS critical chain-length value ranks this polymer's macromolecules as the most flexible of the corresponding long-chain molecules presently known. © 1993 John Wiley & Sons, Inc.     

Viscoelastic characteristics of mixed compositions based on polyethylene and polypropylene

VNIISV, Tver'. Institute of Chemical Physics, Moscow. Translated from Khimicheskie Volokna, No. 3, pp. 42–43, May–June, 1992.     

A diffusion-relaxation model of pulverized fuel combustion

A model for pulverized fuel combustion with allowance for the microstate of the fuel is proposed. It was shown that the burning of a fuel particle having a microstructure follows the laws of external (diffusion) and internal (relaxation) kinetics. The influence of the diffusion-relaxation mechanism on the burnout time of a fuel particle with a polymeric microstructure, its stressed state, and the pulverized fuel flame length was analyzed. The ranges of pulverized-fuel combustion parameters in which the flame length is determined by the fuel combustion or the gas jet mixing mechanism were distinguished.     

Heat resistance of fused and cast baddeleyite-corundum refractories

Conclusions The heat resistance of specimens from different zones of BKCh-33 production parts was investigated by the method of radial thermal flow. Specimens the microstructure of which is distinguished by the minimum quantity of defects, a fine crystalline structure of the products of combined crystallization of baddeleyite and corundum, and uniform distribution of glassy phase have the highest heat resistance, which should be taken into consideration in the production of refractories in industry.Translated from Ogneupory, No. 4, pp. 49–53, April, 1987.