Using mosaic crystals for the generation of intense X-ray beams

The parametric X-ray (PXR) yield due to 500-MeV electrons in a 2-mm-thick diamond crystal with a mosaicity angle of ～0.2 mrad has been studied. It is shown that the mosaic crystal structure leads to a significant (about fourfold) increase in the PXR yield doe to the contribution of diffracted bremsstrahlung radiation. Advantages of using mosaic crystals for the generation of intense X-ray beams are discussed.     

Influence of temperature on the failure of brittle materials in concentrated loading

Conclusions In the area of low temperatures (Tc) the crack resistance and failure stress of high strength brittle materials decrease linearly with temperature, which is caused by the purely brittle character of the failure processes.Maximums are observed on the temperature relationships of radial and surface crack lengths. The formation of maximums may be explained by the increase with temperature of the power of the fields of residual stresses caused by the zones of plastic deformation with a simultaneous drop in crack resistance and failure stress. At increased temperatures with an increase in plasticity and relaxation capacity of the material there is a reduction in the level of residual stresses with a corresponding decrease in crack length until disappearance of them.The position of the maximums in crack length and the temperature of their disappearance depends upon the crack resistance and flow stress (hardness) and for materials with G_1C 2 _y0 the temperature of disappearance of radial cracks is close to the ductile-plastic transition temperature.Translated from Poroshkovaya Metallurgiya, No. 12(252), pp. 75–82, December, 1983.     

Adjustable synchronous electric drives of shaft fans with vector-based control oriented in the field

A special algorithm is developed that provides satisfactory control for mass high-power electric drives. Results of an experimental study and tests of drives are presented that are performed when they are being put into use.     

Rotor Rolling over a Water-Lubricated Bearing

The article presents the results of studying the effect of forces associated with secondary damping coefficients (gyroscopic forces) on the development of asynchronous rolling of the rotor over a water-lubricated bearing. The damping forces act against the background of other exciting forces in the rotor–supports system, in particular, the exciting forces of contact interaction between the rotor and bearing. The article considers a rotor resting on supports rubbing against the bearing and the occurrence of self-excited vibration in the form of asynchronous roll-over. The rotor supports are made in the form of plain-type water-lubricated bearings. The plain-type bearing’s lubrication stiffness and damping forces are determined using the wellknown algorithms taking into account the physical properties of water serving as lubrication of the bearing. The bearing sliding pair is composed of refractory materials. The lubrication layer in such bearings is thinner than that used in oil-lubricated bearings with white metal lining, and there is no white metal layer in waterlubricated bearings. In case of possible deviations from normal operation of the installation, the rotating rotor comes into direct contact with the liner’s rigid body. Unsteady vibrations are modeled using a specially developed software package for calculating the vibration of rotors that rub against the turbine (pump) stator elements. The stiffness of the bearing liner with the stator support structure is specified by a dependence in the force–deformation coordinate axes. In modeling the effect of damping forces, the time moment corresponding to the onset of asynchronous rolling-over with growing vibration amplitudes is used as the assessment criterion. With a longer period of time taken for the rolling-over to develop, it becomes possible to take the necessary measures in response to actuation of the equipment set safety system, which require certain time for implementing them. It is shown that the gyroscopic damping components facilitate the developing rolling of the rotor over the bearing. If measures taken to decrease these components in the damping devices and bearings are met with success, the onset of asynchronous rolling-over with the growing amplitudes occurs after a longer period of time.     

Properties of high-dispersion powders of tungsten carbide produced by high-temperature electrochemical synthesis

Translated from Poroshkovaya Metallurgiya, No. 8(344), pp. 1–4, August, 1991.     

Dynamometric uses of adaptive aerostatic bearings

Translated from Izmeritel'naya Tekhnika, No. 3, pp. 18–20, March, 1990.     

Interphase reaction in materials of the systems Ti-Cr and Ti(C,N)-Cr

Translated from Poroshkovaya Metallurgiya, No. 4(340), pp. 69–74, April, 1991.     

Mechatronic Motorized Spindle with Hydrostatic Bearings and a Piezohydraulic Generator of Resonant Axial Microoscillations

A mechatronic motorized spindle with hydrostatic bearings and a contact-free piezohydraulic generator of resonant axial spindle microoscillations is proposed. The boundary problem is solved for a nonsteady Reynolds equation in laminar motion, with no cavitation of the working fluid. On that basis, analytical formulas are derived for the dynamic-pressure distribution of the working fluid and the dynamic axial force created in the gap of the piezohydraulic generator.