Prediction of the Mechanical Properties of Metals After Cold Pressing
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PREDICTION OF THE MECHANICAL PROPERTIES OF METALS AFTER COLD PRESSING V. A. Ogorodnikov1 and T. F. Arkhipova1, 2
UDC 621.774: 621.919
We propose a procedure for the evaluation of plasticity of the prestrained metal of blanks. This procedure uses the model of fracture based on the tensor description of the accumulation of defects under the conditions of cold plastic deformation. If the mechanical characteristics and plasticity diagrams are known, then this procedure makes it possible to analyze plastic properties of prestrained blanks for all kinds of the stressed state. The procedure was tested under the condition of production of strongly bent branches by method of pulling of a presewn pipe. We observed satisfactory agreement between the computed and experimental data. Keywords: pressure treatment, plasticity, technological inheritance, damage tensor, consumed resource of plasticity.
Introduction The technological inheritance, i.e., residual stresses, strength, strain gradient, residual plasticity, and other factors affecting the in-service properties of the products is revealed after various modes of pressure treatment of metals. For the quantitative evaluation of these factors, it is necessary to develop the corresponding method. Most of these factors were taken into account [1]. However, some of them (e.g., the level of plasticity of prestrained blanks) require additional analysis. The aim of the present work is to develop a method for the evaluation of the anisotropy of plasticity of prestrained metals for various types of stressed states. Procedure of Investigations As a measure of plasticity at the time of fracture of the material of a blank in the region of finite strains, we can use the intensity of accumulated strains (Odquist’s parameter), which is called the limit intensity:
ep =
τp
∫ ε! u dτ , 0
(1)
where ε! u is the intensity of strain rate. The plasticity of metals is determined by the temperature, strain rate, type of the stressed state, history of deformation, strain gradient, and other factors. The dependence of plasticity on the type of stressed state under 1 2
Vinnitsa National Technical University, Vinnitsa, Ukraine. Corresponding author; e-mail: [email protected].
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 55, No. 1, pp. 61–65, January–February, 2019. Original article submitted February 14, 2017. 1068-820X/19/5501–0063
© 2019
Springer Science+Business Media, LLC
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V. A. OGORODNIKOV
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AND
T. F. ARKHIPOVA
the conditions of simple deformation for fixed temperature and rate conditions is called the diagram of plasticity. To construct this diagram, the material is tested in various stressed states under the conditions of simple loading when the components of the stress tensor are proportional to a single parameter. As usual, the stressed state is characterized by its parameter. In particular, according to Smirnov-Alyaev [2], this parameter takes the form
η=
I1 (Tσ ) σ + σ2 + σ3 = 1 , σ1 3I 2 (Dσ )
(2)
where I1 (Tσ ) is the first invariant of the stress ten
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