Cyclic strength of pearlitic steels under conditions of elastoplastic loading

We study the elastoplastic flow of pearlitic steels extensively used for technological purposes under the conditions of low-cycle loading at elevated temperatures and propose an equation of state for the evaluation of the accumulated level of strains as a function of the number of cycles, properties of the material, and parameters of loading. Deceased. Slavyansk State Pedagogical Institute, Slavyansk, Ukraine. Translated from Problemy Prochnosti, No. 3, pp. 133–137, May–June, 2000.     

Low-temperature deformation mechanisms in an Fe-Si-Ti alloy

The temperature and strain-rate dependence of the yield and flow stresses of an age-hardened Fe-Si-Ti alloy, and a binary Fe-Si alloy, have been investigated in the temperature range 77 to 330 K. The parameters of activated deformation have been determined as a function of the precipitate dispersion and it is concluded that these parameters are unaffected by precipitation even when particles are sheared by dislocations, implying that bcc iron alloys cannot be dispersion strengthened at room temperature without making them even stronger, and hence more brittle, at lower temperatures. Work-hardening of all alloys is due to increases in the athermal component of the applied stress. The activation enthalpy at low effective stresses is larger than that for pure iron, indicating that silicon exerts a higher lattice friction stress due to its effect on the core asymmetry of screw dislocations in iron.     

Low-temperature cyclic cracking resistance of higher strength austenitic steels

Translated from Fiziko-Khimicheskaya Meckhanika Materialov, No. 6, pp. 27–32, November–December, 1989.     

Investigation of the regularities of deformation of heat-resistant steels under conditions of creep in the complex stressed state

We study the regularities of deformation of 1Kh18N9T steel under long-term static loading along different paths of radial loading with regard for the influence of the type of stressed state. The viscoplastic properties of 08Kh18N10T-VD steel subjected to stepwise static loading under conditions of complex stressed state are analyzed.     

Vibratory stress relieving of welded sheet steels of low alloy high strength steel

Vibratory stress relieving of D6AC and D406A welding steel plates was carried out. The macro-residual stress decreased to 0±25 MPa, which is the same value as can be achieved by hot stress relief.     

Cavitation in alloy steels during superplastic deformation

A study of cavitation during superplastic tensile straining of two microduplex steels has been made using density measurements and quantitative optical metallography. The steels were of basically similar composition with the exception of a trace addition of boron made to one alloy. During deformation cavities formedα/γ boundaries and matrix-carbide interfaces; the growth and coalescence of these cavities led to failure. Density measurements showed that the extent of cavitation increased with increasing strain and decreasing strain-rate, but the level of cavitation was reduced by the presence of boron. A time dependence of overall void volume of 1.4 to 2.0 was observed. Quantitative metallographic studies of the nucleation and growth contributions to the overall rate of void formation showed that boron inhibited each of these processeS. However, both the nucleation rate and the magnitude of the time exponent of void volume increase suggested that a substantial number of voids grew from pre-existing nuclei which were probably present as non-coherent carbide-matrix interfaces.     

Criteria for determining the long-term strength under conditions of complex loading

It has been pointed out that the problem of determining the long-term strength under complex conditions of loading consists in the simultaneous choice of an equivalent stress _e and the nature of the dependency of the failure time t^* on the value of _e. This is best described by a series of experimental data taken at constant temperature. The problem can be solved by introducing a parameter D which characterizes the total discrepancy between the experimental and theoretical values of t^*, and through the use of a technique for determining the material constants which will lead to a minimum value of D. As an example of this approach, a quantitative treatment of the experimental data given by I.I. Trunin and A. A. Lebedev is presented.Moscow State University Institute of Mechanics. Translated from Problemy Prochnosti, No. 9, pp. 3–6, September, 1989.     

A method for testing pipe steels under the conditions of sulfide stress cracking

We propose a testing method for the evaluation of the threshold crack resistanceK _Issc of pipe steels under the conditions of sulfide stress corrosion cracking. The values ofK _Issc are determined for various casing tubes made of different types of steel after heat treatment. Samara State University, Russia; “Samaraneftegaz” Joint-Stock Company, Russia; VNIITNEFT Research Institute, Russia. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 4, pp. 125–128, July–August, 1999.     

大块非晶合金复杂应力状态塑性本构方程

为得到复杂应力状态下大块非晶合金的塑性本构方程,对Zr41.2Ti13.8Ni10Cu12.5Be22.5大块非晶合金进行简单拉伸、压缩和扭转实验,得到相应的一维本构关系,并应用弹塑性力学的相关理论,将一维本构方程延拓到多维应力空间.研究结果表明:该材料符合Mises屈服条件并具有强化特性;利用简单压缩和扭转实验结果可推导出材料在复杂应力状态下的塑性本构方程,且这两个塑性本构方程是一致的.