Search

A damage model suggested by the Tuler–Butcher concept of dynamic accumulation of microscopic defects is obtained from experimental data on microcrack formation in synthetic kidney stones. Experimental data on appearance of microcracks is extracted from micro-computed tomography images of BegoStone simulants obtained after subjecting the stone to successive pulses produced by an electromagnetic shock-wave lithotripter source. Image processing of the data is used to infer statistical distributions of crack length and width in representative transversal cross-sections of a cylindrical stone. A high-resolution finite volume computational model, capable of accurately modeling internal reflections due to local changes in material properties produced by material damage, is used to simulate the accumulation of damage due to successive shocks. Comparison of statistical distributions of microcrack formation in computation and experiment allows calibration of the damage model. The model is subsequently used to compute fracture of a different aspect-ratio cylindrical stone predicting concurrent formation of two main fracture areas as observed experimentally.

The application of an electric discharge at numerous holes in a dielectric diaphragm for generating spherically focused shock waves in a salt solution is described. The design of the presented transducer makes the erosion of the electrodes impossible, since they are placed beyond the discharge zone; as a result, the point of focus stabilizes. The dependences on the discharge voltage, the number and total area of the holes in the diaphragm, and the electrolyte concentration are obtained for the pressure-wave amplitude at the focus; the extreme values are ∼40 and –12 MPa in the compression and rarefaction waves, respectively. The possibility of comminuting stones with masses of

A modified version of a flat electromagnetic converter for enhancing the amplitude of the pressure of a shock wave using the Laptev-Trishin method and reducing the duration of an acoustic pulse is described. The interference of a focused edge diffraction rarefaction wave and a wave reflected from a free surface is used to form a narrow space-time negative-pressure region. The conditions for generating a single cavitation bubble near the free surface are found.

A transducer for measuring the velocity of shock wave propagation in salt water is described. The transducer operation is based on the depolarization of a double electrical layer exposed to an acoustic pulse. The time lag of the electrolysis current step at a disk anode was used for measuring the velocity of the propagation of the pressure disturbance. It was shown experimentally that the suggested method provides a measurement accuracy of 2% for the shock-wave front velocity, and base length of 5 mm. The transducer withstands repeated exposure to cavitation and shock waves at a pressure of up to 70 MPa.

The dynamics of luminescence generation and cavitation in the field of spherically focused and plane shock-acoustic waves in water, glycerin, and their mixtures is studied. It is shown that in the spherical focusing of shock-acoustic waves, the first pulse of luminescence correlates with cavitational rupture of the liquid. It is assumed that the registered luminescence is caused by electrokinetic processes upon formation and growth of cavitational bubbles.