Effect of copper on the cyclic crack resistance and heat resistance of graphitic steels

We study the effect of copper content (0.05–3.45 mass %) on the structure of the matrix and graphitic phase of graphitic steels (GS) annealed for globular perlite. It has been established that the effect of copper content on the physicomechanical characteristics of GS is ambiguous. An increase in the copper content up to 2.3–2.9% is accompanied by an increase in the characteristics of thermal conductivity, strength, cyclic crack resistance, and heat resistance. The thermal conductivity of GS grows with increase in the copper content (if it is more than 3%), but the mechanical characteristics fall. Thus, the heat resistance of GS is mainly determined by their crack resistance.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 3, pp. 109–112, May–June, 2004.     

Statistical Criteria and Estimation Results for Regularities of Gas-Dynamic Phenomenon Distribution in Potash Deposits

An analysis and estimate are performed for possible schemes of spatial distribution of gas-dynamic phenomena in potash deposits by the methods of mathematical statistics. The problem stated is solved by comparing the numerical characteristics of the events observed and those obtained on the basis of the theoretical model developed.     

Influence of Microstructure on the Strength and Cyclic Crack Resistance of Cast Irons

We study the influence of microstructure of high-strength cast irons of ferritic, ferritic-pearlitic, and pearlitic classes on the characteristics of strength and cyclic crack resistance and establish the relationship between the characteristics of strength and cyclic crack resistance and the chemical composition and microstructural parameters of the matrix and graphite inclusions of high-strength cast irons. Indeed, the ultimate strength _u = 750–850 MPa, fatigue threshold K _th = 8–10 MPa , and cyclic fracture toughness K _fc = 50–60 MPa are guaranteed by the pearlitic matrix and the following parameters of the graphite phase: the content of graphite f _p 10%, the degree of its spheroidization of about 95%, the size of globules d _gl 20–50 m, and the distance between them 40–70 m, obtained in high-strength cast irons containing (wt.%): 3.2–3.5 C, 1.9–2.5 Si, 0.35–0.4 Mn, and 0.05 Mg.     

Electrochemical evaluation of the in-service degradation of an aircraft aluminum alloy

We show that changes in the mechanical properties of an aluminum alloy as a result of its operation or in-laboratory aging are accompanied by a substantial change in its electrochemical properties, which can be used for control of the in-service degradation of the material. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 2, pp. 87–91, March–April, 2008.     

Temperature dependence of mechanical characteristics of wheel steels

We investigate the influence of high temperatures (to 800°C) on the mechanical characteristics of medium- and high-strength wheel steels. It is shown that the lower the austenization temperature and the sharper the increase in the plasticity, which is caused by the dissolution of vanadium carbides and carbonitrides in a high-strength steel, the more favorable the conditions of formation of flat-type defects on the rolling surface of high-strength wheels (of KP-T type) against those for medium-strength wheels (of KP-2 type).     

Degradation of materials and fatigue durability of aircraft constructions after long-term operation

We consider a complex of problems of evaluating the residual lifetime of aircraft constructions after long-term operation. Some results of static and fatigue tests of a D16T-type aluminum alloy (in the as-delivered condition as well as after simulated and operating degradation) in air and a corrosive medium (3% NaCl solution) are presented. We have established characteristics that are the most sensitive to the degradation of constructional materials in the course of long-term operation. We also describe a new approach and correction factors for evaluating the fatigue durability of elements of aircraft constructions with regard for the degradation of materials. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 4, pp. 5–16, July–August, 2006.