PART 2. PLANE STRAIN E. V. Vorob'ev UDC 539.3 The regularities of repeated necking have been studies on flat specimens of alloys for cryogenic engineering in the case of effect of low-temperature discontinuous yield. It has been shown that in contrast to cylindrical specimens, in this particular case there is a considerable deviation of the stressed state from linear stress, which affects greatly the mechanical characteristics determined and does not allow flat specimens to be recommended for standard mechanical tensile tests of metals at temperatures below 30 K.Keywords: low-temperature discontinuous yield, specimen, neck, stress system, stress state rigidity, mechanical characteristics, standard method for the tensile testing of metals.As in the case of axisymmetric deformation [1], the stressed state in the neck of a flat specimen may be represented as a sum of two stress systems: constant stress σ z c and fluctuating (hydrostatic tensile) stress σ h [2]. In the central point of the neck of flat specimen (Fig. 1), σ h reaches the maximum value σ h 0 :