1. When rocks or metals are to be broken up by dynamic loads, experiments show that It is necessary to take account of the time-dependent strength characteristics [5,6] imtead of the "static" characteristics [1][2][3][4]. The point of introducing these characteristics is that an important feature of the breakage process is the time of action of the load: the critical stress must act for a definite time, which increases as the load decreases.In studies of the fracture of many materials such as rocks and many metals and alloys, a metal has been suggested and extensive study has been made of the time-dependent strength characteristic over a wide range of "longevity" r (10"3-10 +T sec), and experiments have confirmed the rule of damage summation when the tensile values of the normal stress have different time dependences [5,6]. However, although this rule applies over a wide range of r values, the latter is very limited, and furthermore the method used to study the characteristic, or its analog, scarcely permits us to study small longevity values and correspondingly high stresses. A model experirnental-analytical method, which gives satisfactory results, is based on study of "scabbing" (splitting-off) phenomena in plates acted on by impact or explosion. There are exact solutions to the dynamic problem of the theory of elasticity concerning an impact on a plate; the analysis on the axis of symme~y is based on certain qualitative ideas about rear scabbing [7,8]. In addition, much experimental materialhas accumulated on the laws of variation of the state of stress in a real material and on the description of the physical pattern of possible fractures [9][10][11] and on the construction of the time-dependent strength characteristic [12].Calculation of the pattern of fracture on the basis of an approximate construction of the solution to the problem of the theory of elasticity in uhe neighborhood of the axis of symmetry wtl~ the aid of an exact solution on the axis itself, followed by correction for the real distribution of the action on the front surface of the plate with account of the real laws of damping, and also on the basis of a suitably-chosen fracture characteristic, can yield interesting data and may be regarded as the converse problem to correcting the strength characteristics of the materlal, the fracture parameters, and the laws of propagation of stress waves.In our experiments we used the scheme shown in Fig. 1. The testspecimens lwereof Steel 3 in the form of square plates, L = 200 mm on a side and b = 5-60 mm thick; they were installed on support 2 and acted on by the detonation of a cylindrical charge 3 of a TNT-Geksogen mixture (TG-50/50) with a density of p = 1.68 g/cm ~ and a detonation velocity of VD = 7800 m/sec. The diameter of the charge was d = 30 mm, and its height H was 10, 30 or 60 ram. It was initiated by electrical detonator 4 attached to the charge at the end opposite the specimen.If we calculate the total impulse Js with the aid of the formula suggested in [13], J, ~ 0.8p 9 vo 9 (H), (1) ...

Strong waves were generated in Plexiglas and in aluminum under a pressure of 2.9 and 7.1 mbars respectively. The retardation of high-velocity streams in air and in inert gases is analyzed.

Durch Einwirkung von Explosionsdruckwellen auf Pulvergemische von Al2O3 mit Mo oder SiC wurden keramische Massen erhalten.