AMts ALLOY CRACKING RESISTANCE, STRENGTH, STRAIN, AND ENERGY CHARACTERISTICS AT STRAIN RATES OF 10-3-10 3 SEC-l N. N. Popov, V. A. Mart'yanov, and V. A. Ponomarev UDC 620.17:669.715The literature gives little information on the effects of strain rate on the mechanical properties of alloys. 777e cracking resistance criterion K x has been determined for low-strength aluminum alloy AMts on small specimens, together with a series of standard and nonstandard strength, strain, and energ3, characteristics for plastic-strain rates of I0-3-10 s sec -1. A dynamically loaded structure such as the central tube in a spiral explosive magnetic generator should be made of AMts alloy in the heat-treated state.AMts aluminunl-magnesium alloy (1.0-1.6% Mg) has good technological features and is therefore widely used in components made by deep drawing and pressing [1]. In particular, it can be used in the central tube of a spiral explosive magnetic generator. The efficiency of such a generator is increased considerably if there are no cracks in the dynamically expanding tube [2]. It is thus necessary to estimate the cracking resistance and also the strength, strain, and energy characteristics of that alloy, over a wide strain-rate range. Usually, tile literature gives mainly standard mechanical characteristics derived in short-time static tests (strain rates up to 20 sec -l) at various temperatures such as in [1, 3].Special equipment is required to measure the force, deformational, or energy criteria of cracking resistance, which employs complicated specimens frequently containing much metal [4]. There is particular difficulty in determining cracking resistance for plastic materials of low and medium strength.Most experiments to estimate failure mechanics criteria relate to tile growth kinetics of already-formed or artificiallyproduced macroscopic cracks, which corresponds to the rising branch of the strain diagram, which characterizes the work hardening [5].A difference from these is that in [6, 7] it was proposed to determine cracking-resistance parameters t'rom the descending part of the complete strain diagram corresponding to the softening stage in the strain localization zone. This enables one to deternline the resistance parameters on specimens much smaller than those traditionally used in failure mechanics. Also, the true physical processes occurring on loading are more fully reflected in the complete strain diagram [8]. To construct that diagram with its ascending and descending branches, one needs a loading system with feedback or very rigid test machines [6].A criterion K x has been proposed [7] for determining the cracking resistance oll the descending branch, which is an analog of the force criterion Kic in planar mechanics:in which Pc, Fc, and xP c are the nominal failure force, area of cross section, and specific narrowing at the instant when the crack starts respectively, while AI w is the total extension of the working part at the stage of macroscopic crack growth (Fig.