Structure and strain hardening of metals with a complex stressed state

Strain hardening features for steels of the austenitic, martensitic, and maraging classes in stable and metastable states in relation to structural parameters in complex biaxial loading conditions have been studied, including prior and repeated (with intermediate unloading) deformation with different principal stress ratios. The structural sensitivity of the Bauschinger effect is studied, structural dependences for yield stress with compression after prior tension are obtained, and generalization of the yield stress under repeated biaxial loading is substantiated by experiment. In the relationships presented there is quantitative consideration of the regularities revealed for the change in structural parameters of deformed metal during repeated loading in relation to the principal stress ratio. Classification of the test steels is suggested according to structural state characteristics caused by preferred isotropic and anisotropic strain hardening.From a paper given at the III All-Union symposium Strength of Materials and Structural Elements with a Complex Stressed State, Zhitomir, October 1989.Translated from Problemy Prochnosti, No. 12, pp. 15–19, December, 1990.     

Development of a method of accounting for the effect of stress concentration and residual stresses on the cyclic longevity of steel 10GN2MFA. Report 1. Analysis of material's stress—Strain state

The stress-strain state induced in a material due to a variable load and residual stresses is calculated for the elastoplastic case. The need is demonstrated and a method proposed for the accounting of residual stresses in calculations involving the cyclic longevity of structural components. The resultant relationship makes it possible to account for the material's plastic properties under static and cyclic loading.Translated from Problemy Prochnosti, No. 8, pp. 3–13, August, 1993.     

Development of a method of accounting for the effect of stress concentration and residual stress on the cyclic longevity of steel 10GN2MFA. Report 2. Prediction of cyclic longevity

The significant influence exerted on cyclic longevity by not only the static coaxial components of the cycle, but also the latter's static components perpendicular to the applied load is established on the basis of experimental data on the fatigue of specimens with a riser and residual stresses. These data are analyzed, however, using familiar limiting relationships of the principal static and variable components of the stress — strain state. The applicability of the criterion of octahedral stresses for predicting the effect of residual stresses on the cyclic longevity of specimens with a riser is established.Translated from Problemy Prochnosti, No. 10, pp. 3–19, October, 1993.     

High-temperature creep tests on specimens of single-crystal molybdenum with a complex stressed state

High-temperature (1550°C) creep tests are performed on tubular thin-walled specimens of single-crystal molybdenum loaded by internal pressure in a 1849P-1/2500 unit with a number of modifications. Strains are measured periodically in the circumferential and axial directions. Test results are processed statistically by two methods.Translated from Problemy Prochnosti, No. 7, pp. 62–64, July, 1990.     

Loss of stability for the process of plastic deformation with a complex stressed state

Basic preconditions are presented for considering the stability of the plastic deformation process in evaluating the ultimate deformation and strength properties of structural materials in tubular specimens under conditions of a complex stressed state. Calculated dependences are provided for calculating these characteristics. Results of experimental studies are analyzed for heat-resistant steels 15Kh2MFA, 15Kh2NMFA, and VK-2 (KP-100) (the latter simulates radiation embrittled steel 15Kh2NMFA) with different principal stress ratios in the temperature range 20–350°C. Calculated values of ultimate stresses and strains are compared with experimental data. The possibility of using the results of experiments carried out with stepwise loading as a basis for calculating the endurance under cyclic loading conditions with a complex stressed state is substantiated.Translated from Problemy Prochnosti, No. 10, pp. 3–8, October, 1991.