More often plasticity of metal characterize standard parameters. At a stretching of cylindrical or flat samples define relative lengthening б And relative narrowing of cross-section section б . Lack standard parameters that define them at the schemes of the intense condition differing from applied in technological processes OMD. Thus, plasticity of metal estimate not invariant characteristics which do not allow to define precisely enough a degree of deformation of the shift, corresponding destruction of metal. The order of carrying out of technological tests and requirements to samples are standardized. At a choice of new schemes and specification of modes of deformation, and also at the decision of questions on limiting deformations more strict account of influence on plasticity of metal of mechanical factors of technology and first of all parameters of the intense condition and character of development of deformation is necessary. Thus it is important to define plasticity and parameters influencing it invariant characteristics that will allow to use the found dependences at the analysis of various processes OMD.
Subsequently some techniques of definition of plasticity depending on the intense condition were offered. A.A.Bogatovym had been stated the offer, what plasticity of metals should be put in dependence on two independent parameters of the intense condition. This parameter together with a condition of fluidity unequivocally defines the intense condition in the sample at test. Sign-variable character of deformation reduces intensity plastic of the friable and consequently leads to increase in plasticity of metal.
The basic requirements at a choice of kinds of test of samples, are the constancy of the intense condition and preservation of monotony of deformation during all experience, high accuracy of definition of parameters of the is intense-deformed condition in a place of destruction.
Stretching of cylindrical samples. Samples apply to test smooth and with bore which form is defined by diameter d in the least cross-section section and in radius of contour R in longitudinal section of the sample. At a stretching of samples with bore plastic deformation begins in top of bore, and then gets to the middle of section of the sample. Deformation during the certain moment is localized and proceeds with formation natural шейки. Experimentally an established fact of equality and uniform distribution on all cross-section section of radial and tangential deformations . On the basis of it it is possible to assume, that in a place of break of the sample deformation proceeds monotonously, and the degree of deformation of shift is identical in all points
Relative hydrostatic pressure in nack on an axis of the sample during test changes, as there is a change of parameter d/R and owing to hardening metal resistance of deformation increases бs. Therefore for processing experimental data and definition of average value for process of test it is necessary to establish preliminary dependence d/R (б) and a curve of hardening бs (B).
The form change of the samples most often fix a method of repeated photographing of the deformable sample during test. A deposit. The degree of deformation of shift at a deposit does not reach great values and at test of samples from plastic materials it can appear insufficient for their destruction. Destruction at a deposit is not accompanied by division of the sample into parts. Therefore the certain difficulties arise in an establishment of the moment of formation of macrocracks. Limiting обжатия at a deposit depend not only on a chemical compound and structure of metal, but also from of some the factors defining a is intense-deformed condition of metal on a lateral surface of the sample. The analysis of the deformed condition on a lateral surface of the besieged cylindrical samples shows, that the degree of deformation of shift depends from обжатия and intensity Flank of formation the sample at a deposit.
At each moment of time on the basis of experimental data about parameters d0/R and б It is possible to find value of a parameter on a lateral surface of the sample. Parameters (б/T) ср and (б) ср it is possible to define by means of nomogram. For simplification of gauging of samples at definition d0/R it is expedient to calculate this parameter through the sizes easily controllable during experience.
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