Effect of temperature and the initial state on the spalling fracture of alloy 36NKhTYu

The article presents the results of an experimental investigation of the effect of the temperature, the sulfur content, and the previous heat treatment on the strength and fracture of the alloy 36NKhTYu under loading by shock waves. The load levels corresponding to different stages of spalling fracture of specimens were determined in the temperature range from −196 to 750‡C. It was established that heating, increase of sulfur content, and hardening of the specimens lead to an imperceptible decrease of the dynamic strength of the alloy. The article presents the results of observations of the structure and nature of spalling fracture of the alloy by optical and electron microscopy. Translated from Problemy Prochnosti, No. 5, pp. 119–122, May, 1996.     

Effect of the initial state on spalling of copper

The results are presented of experimental examination of the effect of the grain size on the spoliation of copper. Levels of the loading pressure, corresponding to various stages of spollation, were determined for two initial states characterized by a mean grain size of 0.29 and 1.62 mm. The results show that for the material with the smaller grain these levels are approximately 0.2 GPa higher than for the material with the larger grain size.Translated from Problemy Prochnosti, No. 2, pp. 73–75, February, 1996.     

Damage of a steel plate from hypervelocity impact

We presents the results of damage of a carbon steel plate30 mm thick upon its loading by the impact of a steel ball5.55 mm in diameter at a velocity of up to7.4 km/sec. The dimensions of the crater formed and the bending flexure of the spalling layer are in good agreement with the results obtained upon a less intense loading of the target. One more feature of damage, namely, a crack passing through the target at the level of the crater bottom, has been revealed for the first time. Institute of Experimental Physics, Sarov 607200. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 119–121, January–February, 1997.     

Brachistochrone with friction

The brachistochrone problem is solved under the action of dry and viscous friction. For this purpose, this problem is represented as a problem of choosing a time optimal normal component (control) of the reaction of the support curve, whose shape is to be found. The Okhotsimsky-Pontryagin method of investigation of the functional differential is applied. Necessary optimality conditions that give the solution of the classical brachistochrone problem without friction and provide the corresponding optimal curves with friction are found. Parametric formulas for brachistochrones under the action of dry and viscous frictions are found analytically. Their properties are investigated. Attainability domains are determined. For certain values of the friction coefficients, the results of calculations are presented, which show the shape of the found brachistochrones and the optimal motion time.     

Crossing a small body of water by an insectomorphic robot on a raft

A mathematical model of the action of water on a raft in the case of nonstationary motion is developed. In the linear approximation, the dynamics and stability of the raft motion in the case of a shifted constant load and disturbed initial data are investigated. The motion enabling the robot to cross a body of water in the simple case when the robot imparts an initial push from the shore to the raft is designed. The proposed algorithm was worked out using computer simulation. Given sufficient data about the robot’s motion, numerical results proving the validity of the algorithm are presented.     

A control for an insectomorphic robot in climbing to the top of a vertical corner and in moving on a step ladder

For a six-legged robot, the problem of climbing a roof of a vertical right dihedral corner along its walls and a vertical high shelf with the help of a step ladder is investigated. The motions are realized with the help of the dry friction forces. The motion of the robot is formed by imposing servo-constraints in the form of adaptive step cycles of legs and the required geometric structure of body motion. An asymptotically stable program motion of legs relative to the body and the whole system is implemented by a PD controller. The results of 3D computer simulation of the controlled robot dynamics are presented.     

Design of submerged turbulent jets of gases of different densities

We present results of a theoretical and experimental investigation of submerged gas jets in the range of density variations ( _j/ _e=0.05–10).Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 4, pp. 715–720, April, 1979.