Ultrasonic Vibroacoustic Processes, Excited By Heating By Impulse Currents of Metals

When passing impulse currents through a conductor, powerful vibro-acoustic oscillations are generated in it. The parameters of these oscillations are easy to control. Changing the duty cycle of pulses allows for such equipment as welding with the allocation of a large amount of heat, and regimes of controlled cooling and ultrasonic quality control of the welded joint. Keywords: welding, vibration, pulse current, diagnostics, ultrasoun

Analysis of the Relationships for the Vibrational Response to the Excitation of Vibro-acoustic Processes in Conductors from the Action of a Pulsed Current

Evaluation of the mechanisms of formation of mechanical deformations is of great importance for the practical application of the electroplastic effect. Estimations of the efficiency of conversion of the energy of the electric pulse in the energy of the magnetic field and mechanical oscillations are obtained. Keywords: pulse current, metal, vibroacoustic, magnetic field, vibration sensors

Electroplastic Processing of Titanium Implants

The results of experimental studies of samples of titanium for implants when exposed to pulsed electric currents. Excitation of longitudinal and transverse vibrations to the sample under these influences can be used in their electroplastic processing and introduction into the bone tissue. When exposed to pulses of surface layers of titanium sample are experiencing significant dynamic load. The possibility of increasing amplitudes with decreasing duration of pulses of electric current was shown. This allows to exclude the heating of implants during such impacts. The peculiarities of ponderomotive effects in titanium samples related to its uniqueelectrical and mechanical properties, precluding the practical manifestation of the classic skin-effect and its impact on the generation of oscillatory processes in the moments of passage of the leading and trailing edges of current pulse. Keywords: titanium, implant, vibration, acceleration, magnetic field, skin effect

ВКЛАД ПОНДЕРОМОТОРНЫХ ФАКТОРОВ В РЕАЛИЗАЦИЮ ЭЛЕКТРОПЛАСТИЧЕСКОЙ ДЕФОРМАЦИИ

Theoretical aspects of the implementation of electroplastic deformation for dynamic pinch-effect at elastic-plastic deformation of metals with the participation of self-magnetic field of current are considered. The redistribution of magnetic field intensity H in the surface layers of metal leads to ponderomotive effects in the form of dynamic pinch effect, which in addition to the electron-plastic action of the pulse current leads to a compression of the sample intrinsic magnetic field and the excitation of elastic vibrations of the skeleton of the crystal lattice, with a repetition frequency of current pulses at the front of their rise. Dynamic pinch effect creates ultrasonic vibration of the lattice system, thus changing the kinetics, and induced plastic deformation due to the increase of the oscillation amplitude of rectilinear dislocations and periodic changes of the position of the dislocation loops with a higher probability of detachment of dislocations from stoppers. At deformation above the yield limit, due to the pinch effect, magnetic field of a current diffuses into crystal, thus the rate of diffusion depends on the conductivity of the metal and the frequency of the current. At the same geometry of the samples, the pinch effect is stronger for materials with high electrical conductivity. For practical use of the technology of electroplastic deformation, especially in the processing of metals by pressure by drawing, rolling and so on, it is necessary to consider physical conditions of the creation of the ponderomotive effects in relation to particular technologically important materials. Рассмотрены теоретические аспекты реализации электропластической деформации для динамического пинч- эффекта в упругой пластической деформации металлов с участием собственного магнитного поля тока. Перераспределение напряженности магнитного поля Н в приповерхностных слоях металла обусловливает пондеромоторные явления в виде динамического пинч-эффекта, который помимо электронно-пластического действия импульсного тока приводит к сжатию образцов собственным магнитным полем и возбуждению упругих колебаний остова кристаллической решетки с частотой следования импульсов тока на фронте их нарастания. Динамический пинч-эффект создает ультразвуковую вибрацию решеточной системы, при этом изменяется кинетика и стимулируется пластическая деформация за счет увеличения амплитуды колебаний прямолинейных дислокаций и периодического изменения позиции дислокационных петель с увеличением вероятности отрыва дислокаций от стопоров. При деформации выше предела текучести за счет пинч-эффекта собственное магнитное поле тока диффундирует в кристалл, при этом скорость диффузии зависит как от проводимости металла, так и от частоты тока. При одной и той же геометрии образцов пинч-эффект выражен сильнее на материалах с высокой электропроводностью. Для практического использования технологии электропластической деформации, особенно при обработке металлов давлением при волочении, прокатке и так далее, необходимо учитывать физические условия создания пондеромоторных эффектов применительно к конкретным технически важным материалам.