Peak Pressure Of Shock Wave Research Articles

Study on the Shock Wave Pressure Characteristics of Pulsed Discharge in Liquid in the Pipe

In this paper, the shock wave characteristics of pulsed discharge in liquid which occurred in the pipe with rod-rod electrodes were studied. The effects of shock wave peak pressure in the discharge were studied with changed the discharge voltage and electrode gap. The results show that the peak pressure of shock wave increased with the increasing of voltage. When the discharge voltage 22kV, the peak pressure of shock wave increased first and then decreased with the electrode gap increased. However, the discharge voltages 26kV and 28kV, the peak pressure of shock waves increased with electrode gap increased. The pressure of the shock wave (Pr) decays exponentially with the distance (r) from the discharging center. Under this experimental condition, the shock wave intensity is calculated by averaging many values of the experiment, and the experience formula is Pr = 2.56E·e-0.4831r.

Based on the Technology of Shaped Charge Numerical Simulation Research of the Ice Model's Combination Blasting

Combination of ice blasting model is set up with the program of blasting with technology of shaped charge, numerical calculation is carried out, and the shockwave peak pressure in ice medium is obtained based on the large-scale finite element software ANSYS/LS-DYNA . This paper analyzes the stress distribution of ice in the combination of underwater explosion loads, and studies the process of the underwater explosion. The article aims to promote the application and research of underwater explosion in Yellow River and Hei Long Jiang River ice blasting, etc.

Time-Resolved High-Speed Visualization and Analysis of Underwater Shock Wave Focusing Generated by a Magnetic Pulse Compression Unit

Paper reports on visualization and analysis of underwater shock waves generation, focusing, and propagation. Recently, shock waves have been attractive with rising attention in medical field. Extracorporeal shock wave lithotripter has been one of its very successful applications. However, the effects of shock waves on living tissue are not sufficiently understood, due to unknown parameters involving the shock wave interaction. For better understanding of affecting points, a precise and controllable shock wave source is required. In this paper, in order to study shock wave effects, pulsed electric discharges produced by magnetic pulse compression circuit were used to generate underwater shock waves. A half-ellipsoidal reflector was used for shock wave focusing. The whole sequences of the shock wave generation, propagation, focusing, and cavitation bubbles, which appeared after shock wave passage, were visualized by time-resolved high-speed shadowgraph method. The peak pressure of shock wave focusing at second focal point reached 180 MPa. A cylindrical test section was used to observe phenomena around the electrode from the pulse discharge to bubble collapse. The first cavitation bubble's collapse occurred at about 750 μs. In the experiment, the two shock waves, one generated by expansion of plasma and another generated by collapse of the cavitation bubble were studied. Using high-speed visualization and image analysis, the velocity and pressure of the two shock waves were evaluated. The peak pressure of shock wave generated by bubble collapse reached 157 MPa.

The Research of Strengthening Mechanism on Ferritic Stainless Steel Under Impact Processing

This paper mainly studies the microstructure and strengthening mechanism of ferritic stainless under laser shock. the mechanical properties and microstructure were observed through the X-ray diffraction and TEM. The results showed that laser induced shock wave peak pressure is higher than the yield strength of stainless steel, the plastic deformation occus under the impact of the role of stress and high strain rate. when the laser power increases, ferritic stainless steel will have an obvious phase transition from the body-centered cubic into hexagonal system.

Effects of Steel Case on Underwater Shock Wave

The effects of steel case confinement for the aluminized explosive on underwater explosion(UNDEX) were experimentally and numerically investigated. The experimental results using 1kg cylindrical charge cased 6mm steel shell, show that steel case enhance the peak pressure, impulse, shock wave energy and decay time relative to the bare charge. The effect of different thickness of steel case was analyzed. With the increase of the case thickness, the shock wave were enhanced first and weaken later, and there is a lag-effect for the peak pressure of shock wave. There is an optimal case thickness which could maximum enhance the peak pressure. According to dimensional analysis, it's found that the ratio of case mass and charge mass( ) is a better dimensionless parameter to estimate UNDEX for a cased charge.

The Numerical Optimization of Laser Shot Peening Parameters Based on Response Surface Analysis

Residual stress field induced by laser shot peening (LSP) was simulated using Box-Behnken experimental design. Compressive residual stress field intensity (S) was introduced to estimate the effect of compressive residual stress field on fatigue performance. The effect of laser process parameters (such as laser shock wave peak pressure, spot diameter and peening number) on S was analyzed by response surface analysis (RSA), quadratic regression predicting model for S was established, and the rationality of that was verified. Finally, the optimal combination of laser process parameters oriented to anti-fatigue manufacture was optimized. The results indicated statistical analysis results agreed well with those of simulation, RSA for parameter optimization of LSP is feasible.

On the Use of Composite Charges to Determine Insensitive Explosive Material Properties at the Laboratory Scale

Laboratory-scale air-blast experiments an gram-range composite explosive charges are presented. The composite charges consist of a spherical booster charge surrounded by a concentric, spherical “candidate material” shell charge. By way of composite charge explosive characterization, the candidate explosive material is able to be characterized through the “removal” of the known booster effects. Using peak shock wave pressures, a method is developed to remove the booster effects from the composite charge’s signature to yield the sole effects of the candidate explosive material, permitting its characterization. Air-blast explosive tests are conducted using digital high-speed shadowgraph visualization to measure the resulting shock wave radial position as a function of time. Booster and composite charge data are converted to Mach number versus shock wave radius profiles and subsequently to peak shock wave pressure versus shock wave radius profiles for characterization of the shell material. Explosives tested include: PETN, RDX, HMX, and Alliant Bullseye® SP.

Hydrodynamic Loading of Ceramic Components Due to Pulsed Discharge in Water

Pulsed discharge in water produces transient pressure waves. For one kind of high-current electron accelerators composed of a water pulse-forming line and a ceramic-insulated vacuum diode, the mechanical stability of the water-vacuum interface should be taken into account during operations. In this paper, by combining empirical formulas of a plasma-driven water-shock theory with a self-consistent underwater explosive approach, a finite element model was introduced to investigate the shock-wave behaviors. The pressure-time history and ceramic mechanical response to pressure waves were presented. In order to get the pressure profile and verify the calculation models, the arc pressure test, including ldquopoint-planerdquo electrode system, was carried out based on a ten-stage Marx generator. Peak pressures of shock waves were measured by the piezoelectric sensor, and related results have a close approximation to the predictions. The relationship between peak pressure and shock-wave energy under nanosecond time-scale pulsed-discharge condition was also obtained in the experiment. These results may be helpful for the estimation of a water shock when designing structural components of pulsed-power machines.

Study of the mechanism of overlays acting on laser shock waves

In laser shock processing, overlays are used to enhance peak pressures and prolong pulse widths of laser shock waves. The overlay usually has three types: rigid, flexible, and liquid overlays. In this paper, some mathematical models are constructed to analyze the process of laser-induced shock waves and pressure attenuations of the shock waves. The analyses indicate that the peak pressure of shock waves depends on the deformation amount of the overlays and the pressure attenuations depend on the deformation speed of the overlays, while the deformation amount and deformation speed are determined by the density and thickness of the overlays. Besides, for the rigid overlay, the elastic modulus must be taken into account in addition to its density and thickness. Furthermore, the reflected waves from the overlays enhance the shocking effects of laser-induced shock waves. Therefore, the rigid overlays are superior to the flexible and liquid overlays.

The Mechanism and Experimental Study on Laser Peen Forming of Sheet Metal

Laser peen forming of sheet metal is a new plastic forming technique based on laser shock waves, which derives from the combination of laser shock processing and conventional shot peening technique, it uses high-power pulsed laser replacing the tiny balls to peen the surface of sheet metal, when the laser induced peak pressure of shock waves exceeds the dynamic yield strength of the materials, the sheet metal yields, resulting in an inhomogeneous residual stresses distribution in depth. The sheet metal responds to this residual stress by elongating at the peened surface and effectively bending the overall shape. On the basis of analyzing the mechanism of laser peen forming, the line-track-peening experiments of 45 steel sheets with 2 mm thickness were carried out; a curved sheet metal with deep layer of residual compressive stress was obtained. The preliminary experiment result shows that laser peen forming can offer desirable characteristics in shaped metals and is a valuable technique for producing components for a range of industries.

AIRBORNE ACOUSTICS OF EXPLOSIVE VOLCANIC ERUPTIONS

A recently developed theoretical model of the airborne acoustic field from an explosive volcanic eruption of the Strombolian type is described in this article. The magma column is assumed to be a circular cylinder, which is open to the atmosphere at the top, and which opens into a large magma chamber below. The magma itself is treated as a fluid, and the surrounding bedrock is taken to be rigid. An explosive source near the base of the magma column excites the natural resonances of the conduit. These resonances result in displacement of the magma surface, which acts as a piston radiating sound into the atmosphere. The source is modeled in much the same way as an underwater explosion from a high-explosive chemical such as TNT, although in the case of the volcano the detonation mechanism is the ex-solution of magmatic gases under extremely high hydrostatic pressure. The new theory shows compelling agreement with airborne acoustic signatures that were recorded in July 1994 at a distance of 150 m from the western vent of Stromboli volcano, Italy. The theoretical and observed power spectra both display the following features: (1) four energetic peaks below 20 Hz, identified as the first four longitudinal resonances of the magma column; (2) a broad minimum around 30 Hz, interpreted as a source-depth effect, occurring because the source lay close to nulls in the fifth and sixth longitudinal resonances and thus failed to excite these modes; and (3) radial resonance peaks between 35 and 65 Hz. On the basis of the theory, an inversion of the acoustic data from Stromboli yields estimates of the depth (≈100 m) and radius (≈16 m) of the magma column as well as the depth (≈83 m), spectral shape and peak shock wave pressure (≈1 GPa) of the explosive source. Most of the parameters estimated from the acoustic inversion compare favorably with the known geometry and source characteristics of Stromboli.

Airborne Acoustics of Explosive Volcanic Eruptions

A recently developed theoretical model of the airborne acoustic field from an explosive volcanic eruption of the Strombolian type is described in this article. The magma column is assumed to be a circular cylinder, which is open to the atmosphere at the top, and which opens into a large magma chamber below. The magma itself is treated as a fluid, and the surrounding bedrock is taken to be rigid. An explosive source near the base of the magma column excites the natural resonances of the conduit. These resonances result in displacement of the magma surface, which acts as a piston radiating sound into the atmosphere. The source is modeled in much the same way as an underwater explosion from a high-explosive chemical such as TNT, although in the case of the volcano the detonation mechanism is the ex-solution of magmatic gases under extremely high hydrostatic pressure. The new theory shows compelling agreement with airborne acoustic signatures that were recorded in July 1994 at a distance of 150 m from the western vent of Stromboli volcano, Italy. The theoretical and observed power spectra both display the following features: (1) four energetic peaks below 20 Hz, identified as the first four longitudinal resonances of the magma column; (2) a broad minimum around 30 Hz, interpreted as a source-depth effect, occurring because the source lay close to nulls in the fifth and sixth longitudinal resonances and thus failed to excite these modes; and (3) radial resonance peaks between 35 and 65 Hz. On the basis of the theory, an inversion of the acoustic data from Stromboli yields estimates of the depth (≈100 m) and radius (≈16 m) of the magma column as well as the depth (≈83 m), spectral shape and peak shock wave pressure (≈1 GPa) of the explosive source. Most of the parameters estimated from the acoustic inversion compare favorably with the known geometry and source characteristics of Stromboli.

The maximum volume of urinary calculi to be disintegrated by ESWL

In our investigations to develop microexplosion lithotripsy (MEL), the detonation theory, which was proposed in industrial blasting, was proved to be tenable also in MEL with tiny explosives of a few mg. According to the theory, the peak pressure of shock wave generated by blasting was analyzed relating to the volume of calculi. 472 cases of renal urinary calculi to be disintegrated by ESWL were examined. For the successful disintegration, the maximum length of calculi, which was employed conventionally, was a good predictor as for those less than 15 mm (disintegrated in 95%) and those more than 25 mm (disintegrated in 8%). However, the maximum length could not predict the successful result in calculi with intermediate maximum length between 15 and 25 mm. For this intermediate range of the maximum length, the volume of calculi was a very good indicator to show whether the integration was possible or not, because the large majority (90%) of calculi less than 6 cm3 was treated successfully, while none of calculi more than 6 cm3 was disintegrated. According to the theory, the peak pressure of shock wave generated by blasting, which was required to disintegrate a calculated of 6 cm3, was calculated as 80 MPa. Since it is believed that the peak pressure generated by usual ESWL machines is between 80 and 120 MPa at the focussing point, the conclusion in this report that the maximum volume of calculi disintegrated by ESWL might be 6 cm3 was thought to be fairly reasonable.

Routine liver function tests and serum amylase determinations after biliary lithotripsy: are they necessary?

Shock-wave-induced soft-tissue damage after biliary extracorporeal shock-wave lithotripsy (BESWL) has been reported. Every patient treated in Vancouver has, therefore, had liver function tests and serum amylase levels measured before and within 6 days after BESWL. All patients had symptomatic cholecystolithiasis with normal pre-BESWL biochemistry. Analysis of 311 patients after treatment with the Siemens Lithostar unit showed elevation of one or more laboratory value in 19% (60/311). Serum aspartate transaminase level was most frequently abnormal (38 cases). The majority of abnormalities were mild, less than two times normal levels. Clinically significant complications occurred in five patients (three pancreatitis, one cholecystitis, one common bile duct obstruction); four of these occurred 1 week or more after treatment. The results of routine laboratory tests could not be used to predict complications. No correlation was seen between abnormal values and number of shock waves administered or peak shock-wave pressure. Of 112 patients surveyed at the time of post-BESWL enzyme measurement, 49 (44%) reported a degree of pain, which was severe in eight cases. Presence of severe pain correlated strongly (p less than .001) with abnormal laboratory findings, however not with the degree of abnormality. As results of these laboratory tests are nonspecific, have not been shown to correlate with the degree of severity of BESWL-induced tissue damage, and do not predict complications, the tests are of little value in the absence of clinical signs and symptoms. These conclusions, however, apply only to the Siemens Lithostar Plus with patients treated in the steep left posterior oblique position. Cost savings can be expected if routine post-BESWL biochemical tests are abandoned.