Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow, Russia S.N. Buravova, Ju. A. Gordopolov, I.V. Saikov Formation of localized deformation strips during welding by explosion

Shock wave in a projectile (1), in a target (2), and a channel crack (3). AO – a trajectory of intersection of the rarefaction wave head characteristic point and front of a shock wave 2. The localized deformation strip is a zone of an interference of lateral rarefaction waves where the pressure of damage stretching does not reach spall stretch Damage during drop, rain or cavitation erosion Formation of a needle-like spall

3. Experimental check of the forecast of formation of a needle – like (damage) crack 1. Explosive charge with a detonator; 2. plate-projectile; 3. Sample; 4. Holder Channel cracks The scheme of modeling formation channel and cylindrical coaxial spall

4. Metallographic section of a steel target after the impact of a bar shaped ledge plate/ V~1000 m/sec. Modeling experiments. Formation needle-like damage is general phenomenon. It is observed at pulse laser irradiation, at cavitation erosion. Materials fracture in cracks Laser impact

1.shock wave in a projectile 2. shock wave in a target 3.channel spall crack 4. inner rarefaction wave 5. cylindrical zone of interference of the inner and lateral rarefaction waves 6. lateral rarefaction wave 5. Diagram of formation of cylindrical spall damage The needle-like crack at repeated loadings itself becomes a source internal unloading waves. The interference of internal rarefaction with a lateral wave creates a cylindrical coaxial zone of high tensile pressure.

6. Laser irradiation impact (V~ m/sec). System of longitudinal cracks in experiment with the sample containing an artificial channel aperture At the speeds close to ballistic threshold, pressure of tensile in cylindrical zone of interference is below spall strength. It is adiabatic strip which defines formation of a cork at penetration of shell at ballistic velocity.

Structure of the titan sample after shock loading Dependence of structure of the titan formed at high-speed loading from its initial condition / M.P.Bondar, O.L.Pervuhina // ФГВ Т С Border of a contact zone. Structures of connection zone of the titan and low – carbon steel Konon JU.A.welding explosion L.B.Pervuhin, A.D.Chudnovsky; JU.A.welding explosion (ed :Kudinova V.M.) - М.: MaschinostroeniJa Structure of the titan after shock wave loading and in a zone of connection after explosion welding.

Irregular mode of the shock wave reflection off the free surface of thebase plate There are two rarefaction waves: the first one bends the front and reduces its intensity. Cc- its head characteristic. Aa– a tail characteristic of the first wave which is a head characteristic of the second wave. The inclination angle of the shock wave front at a free surface: The second rarefaction wave arises from each point of a free surface where shock wave passes. А.А. Grib at all//Prikladnaya matematika i mekhanika, v. XX, 1956, № 4, c Pressure of the shock wave onto free surface of the base plate: 8. Wave picture( scheme) of current about a point of contact

9. Formation of micro rim on surfaces of cladding plates 1. Rim 2. Shock wave Small-scale wave formation is not connected with classical wave formation of boundary dividing materials. The ledge size makes microns

10 Conclusion: Small-scale protrusions are that mechanism which starts – up formation of localization deformation strips.