Экспериментальное и теоретическое исследование высокоскоростного проникания длинных стержневых ударников в песок

Results of computations with the use of improved modified Alekseevskii-Tate theory (IMATT) are compared to experimental data on high-velocity penetration of long rod projectiles into sand in the impact velocity range of V0=0.5-3.5 km/s. Projectiles were made of three different metals: M1 copper, WNZh tungsten heavy alloy and 30KhGSA steel. The value of hardening coefficient k in the linear dependence of the projectile material yield on pressure could be determined using IMATT and experimental data on dependence of differential penetration coefficient K on the penetration velocity. At penetration in regime of the hydrodynamic erosion of projectile, differential penetration coefficient K could be approximated just by dependence on the ratio of the impact velocity of penetration to the value of the critical velocity, above which the projectile deforms plastically during penetration. The values of the critical velocity may differ for specific projectile material properties as well as the density and the humidity of sand.

CHIP FORMATION DURING THERMAL FRICTION TURN-MILLING

This paper presents the results of chip formation studies in the processing of 30KhGSA steel by thermofriction turn-milling. When studying the process in this work there are presented the results of studying chip formation when the processing of chip formation there is used the metallographic method. Chip root area investigated. The dependence of the chip shrinkage coefficient on the cutting speed and feed was also investigated. It is established that with increasing supply S the value of the chip shrinkage coefficient K decreases. The higher the chip shrinkage factor, the more work will be required to cut the chips and the more complex the processing process.

Incipience and development of spall fracture in 30KHGSA steel, α↔ε transformation, spall fracture and damage recovery

Results of investigation into strength and elasto-plastic properties of 30KhGSA steel are presented. The investigation was performed with planar samples using submicrosecond shockwave length technique. Shockwave amplitude varied in the range from 4 to 26 GPa and controlled with 0.2% accuracy. Steel sample temperature varied in the range from-90 °C to 670 °C. Stress wave profiles in the samples were registered with VISAR and PDV interferometers having nanosecond time resolution and measurement error better than 0.8%. Special attention was payed to the study of spall fracture incipience and development processes as well as damage recovery (healing), and shockwave passing through the damaged region in steel samples. Relaxation characteristics of dynamic elastic limit were determined. Spall strength magnitude versus strain rate and temperature characteristics was determined. The impact of polymorphic α↔ε transition in 30KhGSA steel on spall strength was studied.

Numerical 3D-modeling of spall and shear fractures in shells of austenitic 12Kh18N10T steel and 30KhGSA steel under their spherical and quasi-spherical explosive loading

To pursue VNIIEF–VNIITF joint investigations, this paper briefly describes the experimental setup and provides numerical 3D-computation results (LEGAK-3D technique) on special features in the convergence dynamics of steel shells under their quasi-spherical explosive loading in the system with the 40-mm outer radius of the explosive layer. The computation results were compared with the data experimentally registered for shells of the 30KhGSA steel, both as-received and quenched to HRC 35…40, and the austenitic 12Kh18N10T stainless steel. The comparison was also made with laser-interferometry results obtained directly under explosive loading, as well as with gamma-tomography and scanning electron microscopy investigations of the recovered shells.