Development of low-temperature jumpwise deformation of metals and possibilities of its elimination
- 20 Downloads
- 3 Citations
Abstract
We propose a mathematical model of jumpwise deformation under conditions of deep cooling based on an analysis of the localized adiabatic heat release, inertial properties, and accumulated elastic energy of loading forces. The model enables one to give a qualitative description of the kinetics of intermittent flow of metals and establish quantitative estimates of the parameters of the jumps of strains, which are in reasonably good agreement with the experimental data and adequately describe the mechanical behavior of the material depending on the conditions of loading and deformation. We also consider the influence of various factors on the possibility of suppressing of the effect of mechanical instability of metals, which is of significant practical interest.
Keywords
Mechanical Instability Additional Loading Thermal Softening Intermittent Flow Deep CoolNotation
- T
absolute temperature, K
- T0
initial temperature, K
- ΔT
increment of temperature in the zone of flow, K
- C
stiffness of the specimen-machine system, N/m
- K
effective modulus of the system, MPa
- ε,\(\dot \varepsilon \), and\(\ddot \varepsilon \)
plastic component of strains, strain rate for this component, and acceleration, respectively
- σY
yield limit of the material of the specimen, MPa
- σ0
initial stress corresponding to the beginning of a jump, MPa
- μ
viscosity factor, MPa·s
- Θ
strain-hardening coefficient, MPa
- α
coefficient of linear thermal expansion, K−1
- E
elasticity modulus, MPa
- cv
specific heat capacity, J·m−3·K−1
- βp
coefficient of transformation of the work of plastic deformation into heat
- kt
coefficient of thermal softening, MPa·K−1
- τc
duration of a jump of strains, s
- t
time, s
- m
added mass, kg
- g
gravitational acceleration, m/s2
- l
length of a part of the specimen, m
- F
cross-sectional area of the specimen, m2
- ω
frequency of the exciting action, s−1
- ωλ
natural frequency of the specimen-machine system, s−1
Preview
Unable to display preview. Download preview PDF.
References
- 1.V. A. Strizhalo and E. V. Vorob’ev, “Low-temperature intermittent flow of structural alloys,”Probl. Prochn., No. 8, 37–46 (1993).Google Scholar
- 2.V. A. Strizhalo and E. V. Vorob’ev, “Low-temperature intermittent flow of hardening materials,”Probl. Prochn., No. 10, 3–8 (1994).Google Scholar
- 3.G. S. Pisarenko and V. A. Strizhalo, “Influence of deep cooling on the distinctive features of deformation of structural alloys and the choice of admissible stresses,” in:Strength of Materials and Structures at Low Temperatures [in Russian], Naukova Dumka, Kiev (1990), pp. 3–9.Google Scholar
- 4.V. A. Strizhalo, E. V. Vorob’ev, and L. S. Novogrudskii, “Influence of prestraining on the low-temperature intermittent flow of materials at a temperature of 4.2 K”,Probl. Prochn., No. 8, 12–20 (1995).Google Scholar
- 5.Z. S. Basinskii, “Instability of plastic flow of metals at very low temperatures,”Proc. Roy. Soc.,A240, 229–242 (1957).Google Scholar
- 6.V. I. Startsev, V. Ya. Il’ichev, and V. V. Pustovalov,Plasticity and Strength of Metals at Low Temperatures [in Russian], Metallurgiya, Moscow (1975).Google Scholar
- 7.G. A. Malygin, “Thermal mechanism of the unstable deformation of metals at low temperatures,”Fiz. Met. Metalloved.,65, Issue 5, 864–874 (1987).Google Scholar
- 8.I. S. Zhitomirskii and I. N. Nechiporenko, “On the theory of jumpwise plastic deformation at low temperatures,”Fiz. Nizk. Temper.,4, No. 8, 1053–1062 (1978).Google Scholar
- 9.L. P. Cubin, Ph. Spiesser, and Y. Estrin, “Computer simulation of the low-temperature instability of plastic flow,”Acta Met.,30, No. 2, 385–394 (1982).CrossRefGoogle Scholar
- 10.V. V. Demirskii and S. N. Komnik, “On the kinetics of stress jumps during plastic deformation of crystals,”Acta Met.,30, No. 12, 2227–2232 (1982).CrossRefGoogle Scholar
- 11.S. N. Komnik and V. V. Demirskii, “Relationship between the dynamics of plastic flow and mechanical instability of materials at cryogenic temperatures,” in:Cryogenic Materials and Their Welding [in Russian], Naukova Dumka, Kiev (1986), pp. 61–66.Google Scholar
- 12.A. P. Baraz and B. V. Molotilov, “Localization of sliding in the process of jumpwise deformation of monocrystals of niobium at 4.2 K,”Fiz. Nizk. Temper.,3, No. 4, 514–523 (1977).Google Scholar
- 13.E. V. Vorob’ev and V. A. Strizhalo,Installation for Testing Materials for Dynamic Tension [in Ukrainian], Inventor’s Patent of the Ukraine, No. 95073200, Issued on 01.07.1997.Google Scholar
- 14.V. A. Strizhalo and E. V. Vorob’ev, “Simulation of low-temperature intermittent flow by the method of pulsating additional loading,”Probl. Prochn., No. 3, 83–89 (1997).Google Scholar
- 15.G. P. Stepanov,Elastoplastic Deformation and Fracture of Materials under Pulsating Loading [in Russian], Naukova Dumka, Kiev (1991).Google Scholar
- 16.E. Kamke,Differentialgleichungen Lösungsmethoden und Lösungen, Leipzig (1959).Google Scholar
- 17.V. A. Strizhalo, L. S. Novogrudskii, and E. V. Vorob’ev,Strength of Alloys Used in Cryogenic Engineering under the Action of Electromagnetic Fields [in Russian], Naukova Dumka, Kiev (1990).Google Scholar
- 18.S. Z. Stasyuk and M. P. Zemtsov, “Investigation of the short-term strength of structural materials under static loading,” in:Mechanical Testing of Structural Alloys at Cryogenic Temperatures [in Russian], Naukova Dumka, Kiev (1982), pp. 5–18.Google Scholar
- 19.G. A. Malygin, “Heating of lines and slip bands in thin crystals at low temperatures,”Fiz. Tverd. Tela,20, No. 9, 2825–2827 (1978).Google Scholar