PLASTIC ZONES FORMATION UNDER DIFFERENT TYPES OF LOADING CONDITIONS

The plastic zone formation under the fracture surface in materials pos essing a Body-Centered Cubic Lattice (BCC) structure (steel 20, 40, 45 , St 3, 15X2M Phi A) and materials posessing a Fece-Centered Cubic Lat tice (FCC) structure (aluminium alloy D16 and austenitic steels 40 Gam ma 18 Phi, 40X4 Gamma 18 Phi, 03X13A Gamma 19, 07X13H4A Gamma 20) was studied by the X-Ray Diffraction method. Specimens were tested under a static, impact, high-speed impulse, cyclic (fatigue) and impact-cycli c loading conditions at the wide temperature range. It was shown that two plastic zones were formed under all above types of loading conditi ons if the plane stress state was attained at the crack rip. Only one micro-plastic zone is formed under the plane strain deformation state. A scheme of two plastic zones formation at the crack tip of specimens tested under a static, impact and impulse types of loading conditions is presented. Besides that, it was found that both impulse and impact -cyclic loadings resulted in not only plastic zones formation but work hardening of the material of specimens.