Maximum Shock Research Articles

Alumina/NiCu Laminate under Thermal Shock up to 1000°C: I, Experimental

The mechanical behavior of an alumina/NiCu laminate under thermal shock loading was investigated. The maximum thermal shock temperature was 1000°C. The laminate architecture was the cause of a basic change in the cracking mechanisms, manifested in a dramatic increase in the mechanical residual strength over that of monolithic alumina. The laminated system was constructed by alternating alumina layers coated with copper films with nickel interlayers and joining them by a combination of liquid-state (brazing) and solid-state (diffusion) bonding. The material system was tested by water quenching square-shaped laminated specimens initially at temperatures of up to 1000°C. Three-point bending tests revealed the mechanical strength before and after thermal shock, and SEM analysis described the damage mechanisms and the extent of debonding at the alumina/NiCu interfaces.

Residual Stresses in Silicon Nitride Based Composites Using Synchrotron Radiation

AbstractIn order to measure the residual strain (stress) in the silicon nitride based composites, synchrotron based x-ray diffraction was employed on the BESSRC beamline at the APS. The residual stress for both the baseline Si3N4 and the Si3N4-TiN composites were determined from the (441) and (531) reflections, obtained by applying the three-dimensional 2θ-sin2ψ method. In both the baseline Si3N4 and the Si3N4-TiN composites, after thermal shocking, compressive residual stresses were developed in both directions parallel and perpendicular to the specimen's surface. The average residual stresses in the direction parallel to the sample surface were much higher than in the perpendicular direction.The measured residual stresses were compared with the flexural strength and fracture toughness results to determine the effects of residual stress and thermal shocking on the strength and toughness of each composite. The results suggested that there should be a maximum thermal shock temperature, within the range of 1000 °C to 1100 °C, for improving the fracture toughness for both the baseline Si3N4 and the Si3N4-TiN composites. Also, the addition of the TiN appeared to improve both the strength and toughness of the baseline composition.

Anticonvulsive activity of Albizzia lebbeck, Hibiscus rosa sinesis and Butea monosperma in experimental animals

The ethanolic extracts of leaves of Albizzia lebbeck and flowers of Hibiscus rosa sinesis and the petroleum ether extract of flowers of Butea monosperma exhibited anticonvulsant activity. The bioassay guided fractionation indicated that the anticonvulsant activity lies in the methanolic fraction of chloroform soluble part of ethanolic extract of the leaves of A. lebbeck, acetone soluble part of ethanolic extract of H. rosa sinesis flowers and acetone soluble part of petroleum ether extract of B. monosperma flowers. The fractions protected animals from maximum electro shock, electrical kindling and pentylenetetrazole-induced convulsions in mice. The fractions also inhibited convulsions induced by lithium–pilocarpine and electrical kindling. However, they failed to protect animals from strychnine-induced convulsions. The fractions antagonised the behavioral effects of d-amphetamine and potentiated the pentobarbitone-induced sleep. The fractions raised brain contents of gamma-aminobutyric acid (GABA) and serotonin. These fractions were found to be anxiogenic and general depressant of central nervous system.

A Simple Scaling Analysis of X‐Ray Emission and Absorption in Hot‐Star Winds

We present a simple analysis of X-ray emission and absorption for hot-star winds, designed to explore the natural scalings of the observed X-ray luminosity with wind and sstellar properties. We show that an exospheric approximation, in which all of the emission above the optical depth unity radius escapes the wind, reproduces very well the detailed expression for radiation transport through a spherically symmetric wind. Using this approximation we find that the X-ray luminosity $L_x$ scales naturally with the wind density parameter $\Mdot/\vinf$, obtaining $L_x \sim (\Mdot/\vinf)^2$ for optically thin winds, and $L_x \sim (\Mdot/\vinf)^{1+s}$ for optically thick winds with an X-ray filling factor that varies in radius as $f \sim r^s$. These scalings with wind density contrast with the commonly inferred empirical scalings of X-ray luminosity $L_x $ with bolometric luminosity $L_B$. The empirically derived linear scaling of $L_x \sim L_B$ for thick winds can however be reproduced, through a delicate cancellation of emission and absorption, if one assumes modest radial fall-off in the X-ray filling factor ($s \approx -0.25$ or $s \approx -0.4$, depending on details of the secondary scaling of wind density with luminosity). We also explore the nature of the X-ray spectral energy distribution in the context of this model, and find that the spectrum is divided into a soft, optically thick part and a hard, optically thin part. Finally, we conclude that the energy-dependent emissivity must have a high-energy cut-off, corresponding to the maximum shock energy, in order to reproduce the general trends seen in X-ray spectral energy distributions of hot stars.

The thermal shock resistance of solids

The thermal shock resistance of a brittle solid is analysed for an orthotropic plate suddenly exposed to a convective medium of different temperature. Two types of plate are considered: (i) a plate containing a distribution of flaws such as pores, for which a stress-based fracture criterion is appropriate, and (ii) a plate containing a single dominant crack aligned with the through-thickness direction, for which a critical stress intensity factor criterion is appropriate. First, the temperature and stress histories in the plate are given for the full range of Biot number. For the case of a cold shock, the stress field is tensile near the surface of the plate and gives rise to a mode I stress intensity factor for a pre-existing crack at the surface of the plate. Alternatively, for the case of hot shock, the stress field is tensile at the centre of the plate and gives rise to a mode I stress intensity factor for a pre-existing crack at the centre of the plate. Lower bound solutions are obtained for the maximum thermal shock that the plate can sustain without catastrophic failure according to the two distinct criteria: (i) maximum local tensile stress equals the tensile strength of the solid, and (ii) maximum stress intensity factor for the pre-existing representative crack equals the fracture toughness of the solid. Merit indices of material properties are deduced, and optimal materials are selected on the basis of these criteria, for the case of a high Biot number (high surface heat transfer) and a low Biot number (low surface heat transfer). The relative merit of candidate materials depends upon the magnitude of the Biot number, and upon the choice of failure criterion. The effect of porosity on thermal shock resistance is also explored: it is predicted that the presence of porosity is generally beneficial if the failure is dominated by a pre-existing crack. Finally, the analysis is used to develop merit indices for thermal fatigue.

Shock wave focusing using geometrical shock dynamics

A finite-difference numerical method for geometrical shock dynamics has been developed based on the analogy between the nonlinear ray equations and the supersonic potential equation. The method has proven to be an efficient and inexpensive tool for approximately analyzing the focusing of weak shock waves, where complex nonlinear wave interactions occur over a large range of physical scales. The numerical results exhibit the qualitative behavior of strong, moderate, and weak shock focusing observed experimentally. The physical mechanisms that are influenced by aperture angle and shock strength are properly represented by geometrical shock dynamics. Comparison with experimental measurements of the location at which maximum shock pressure occurs shows good agreement, but the maximum pressure at focus is overestimated by about 60%. This error, though large, is acceptable when the speed and low cost of the method is taken into consideration. The error is primarily due to the under prediction of disturbance speed on weak shock fronts. Adequate resolution of the focal region proves to be particularly important to properly judge the validity of shock dynamics theory, under-resolution leading to overly optimistic conclusions.

Effect of grain size and pressure on twinning and microbanding in oblique shock loading of copper rods

High-purity copper rods in a range of grain sizes—29 μm, 141 μm and 375 μm—were shock loaded in an cylique, cylindrical shock fixture which simultaneously and linearly strained the rods from zero to 5% at peak pressures calculated to range from 11 to 30 GPa at the top and bottom of the rods, respectively. These pressures correspond to the minimum and maximum shock deformation. Light metallography and transmission electron microscopy revealed that the density of deformation twins was measurably and observably increased with both increasing grain size and deformation (pressure). In addition, microbands coincident with traces of {111} planes were observed to be intermixed with the deformation twins. The microbands were almost exclusively associated with a single (or primary) {111} glide plane. The tendency for microband formation, isolated or intermixed with twins, was qualitatively observed to increase with increasing grain size. There appears to be a direct, shear-related connection between microbands and deformation twin/twin-faults in oblique shock loaded copper. The obliquity of the shock wave seems to suppress the critical twinning pressure of copper, since twinning was observed at pressures of only 11 GPa at the top of the rods in contrast to an established critical twinning pressure of approximately 20 GPa for plane-wave shock loading of copper.

Coherent anti-Stokes Raman spectroscopy of shock-compressed liquid carbon monoxide–oxygen and nitrogen–oxygen mixtures

A two-stage light gas gun and single-pulse multiplex coherent anti-Stokes Raman scattering (CARS) have been used to obtain carbon monoxide, nitrogen, and oxygen vibrational spectra for several high-pressure/high-temperature, dense fluid, carbon monoxide–oxygen, and nitrogen–oxygen mixtures. The experimental spectra were compared to synthetic spectra calculated with a semiclassical model for CARS intensities and using best fit vibrational frequencies, peak Raman susceptibilities, and Raman linewidths for each mixture component. Up to a maximum shock pressure of 6.75 GPa for carbon monoxide–oxygen mixtures, the CO and O2 vibrational frequencies were found to increase monotonically with pressure and depended on the carbon monoxide–oxygen mixture ratio. For the nitrogen–oxygen mixtures, the N2 vibrational frequency increased monotonically with pressure to a maximum experimental pressure of 12.9 GPa, however the O2 vibrational frequency increased with pressure to about 11 GPa and then appeared to decrease slightly as the pressure increased to the experiment maximum of 12.9 GPa. Empirical fits of the measured Raman frequencies incorporating previously published neat nitrogen, carbon monoxide, and oxygen data and using a functional form dependent on pressure, temperature, and mixture ratio, accurately describe the N2 , CO, and O2 vibrational frequency shifts for both the carbon monoxide–oxygen and the nitrogen–oxygen mixtures. The transition intensity and linewidth data suggest that thermal equilibrium of the vibrational levels is attained in less than 10 ns at these shock pressures. The vibrational temperatures obtained for the nitrogen–oxygen mixtures were used to improve the oxygen potential function used to calculate equation-of-state pressures and temperatures. The measured linewidths for CO, N2 , and O2 were different for the different mixtures and did not appear to depended significantly on mixture ratios. The broadening of all spectral lines suggested that the vibrational dephasing time for each species decreased to a few ps at the highest pressure shock states.

The propagation of weak shocks in non-uniform flows

A new theory of the propagation of weak shocks into non-uniform, two-dimensional flows is introduced. The theory is based on a description of shock propagation in terms of a manifold equation together with compatibility conditions for shock strength and its normal derivatives behind the shock. This approach was developed by Ravindran & Prasad (1993) for shocks of arbitrary strength propagating into a medium at rest and is extended here to non-uniform media and restricted to moderately weak shocks. The theory is tested against known analytical solutions for cylindrical and plane shocks, and against a full direct numerical simulation (DNS) of a shock propagating into a sinusoidal shear flow. The test against DNS shows that the present theory accurately predicts the evolution of a moderately weak shock front, including the formation of shock-shocks due to shock focusing. The theory is then applied to the focusing of an initially parabolic shock, and to the propagation of an initially straight shock into a variety of simple flows (sinusoidal shear, vortex array, point-vortex array) exhibiting some fundamental properties of turbulent flows. A number of relations are deduced for the variation of shock quantities with initial shock strength MS0 and the Mach number of the flow ahead of the shock MU (e.g. separation of shock-shocks and maximum shock strength at a focus). It is found that shock-shocks are likely to form in turbulent flows with Mt/M1N > 0.14–0.25, where Mt is the average Mach number of the turbulence and M1N is the Mach number of the shock in a flow at rest. The shock moves up to 1.5% faster in a two-dimensional vortex array than in uniform flow.

Silicon micromachined integrated suspension systems for magnetic disk drives

This paper presents results related to the design, fabrication and static/dynamic testing of a silicon micromachined integrated suspension system. This novel magnetic read/write head suspension with its built-in electrodes has been developed especially for automated assembly with miniaturized slider bearings. The one-piece construction silicon microgimbal and the polyimide-reinforced silicon load-beam are designed to have minimum profile, maximum pitch and roll compliances, maximum in-plane stiffness and maximum shock resistance, all of which are important operational requirements for the emerging small-form-factor magnetic recording rigid disk drive market.

Shock features in iron‐nickel metal and troilite of L‐group ordinary chondrites

Abstract— Shock metamorphic features in opaque minerals (FeNi metal and troilite) of 22 L chondrites have been studied petrographically and geochemically in an attempt to establish a connection between the present silicate‐based shock classification scheme (Stöffler et al., 1991) and the peak‐shock and postshock thermal history recorded in these minerals. Unshocked to weakly shocked (S1–S3) L chondrites contain FeNi metal and troilite that display textures related to normal, slow cooling. They may also contain rare disequilibrium shock features, which suggest localized departures from equilibrium shock conditions. Above shock stage S3, selected melting of FeNi metal and troilite produces melt droplets whose composition and abundance correspond to the maximum equilibrium shock state achieved by the sample. At these higher shock levels, the abundance of other shock‐induced features, such as polycrystalline kamacite, sheared and fizzed troilite, coarse‐grained pearlitic plessite, polycrystalline troilite, and polymineralic melt veins serve as textural criteria that can be used to establish peak‐shock conditions. Minimum postshock temperatures obtained from analyses of plessite components show a systematic increase in temperature with an increase in shock stage, thereby providing additional information about the postshock thermal histories of L chondrites. At the highest shock levels recorded in L chondrites (S6 and above), melting and chemical homogenization of FeNi metal produces flattened Ni profiles that may partially to completely obscure any evidence for an earlier, slow‐cooling history. All of these features serve as aids for shock classifying L chondrites as well as for quantifying minimum peak temperatures that resulted during shock metamorphism.

95/06035 The 15 cm inspection robot

In a nuclear power plant, chalk river unidentified deposit (CRUD) is known as a deposit that is composed of corrosion and oxidation materials. It has a porous structure, which combines with boron that is injected into the coolant for controlling power levels. The buildup of corrosion products on the fuel cladding surface has proven to be particularly significant for both BWRs and PWRs. The high temperature of the cladding surface attracts impurities and chemical additives in the reactor coolant that deposit on the fuel rod surface in a process. The deposits on a fuel rod, known as CRUD, can be tenacious, insulative compounds capable of increasing the local clad temperature and accelerating clad corrosion—sometimes to the point of fuel failure.The deposition of CRUD on fuel cladding surfaces causes uneven heating of the reactor core. The situation is exacerbated by boron, which is added to the coolant to control power levels. However, boron becomes concentrated and is deposited within thick CRUD deposits. Ultrasonic mechanisms were developed but they have limitations for decontamination. In this experiment, a decontamination test was conducted using a sample sheet that was composed of SiC/water nanofluids. In addition, it was exposed to swirl flow and common flow for checking enhanced cavitation. It is measured by a pressure film, as shock pressure is associated with cavitation number. As a pressure film is wetted easily in water, it was injected into a holder. In the experiment, the maximum shock pressure was obtained during swirl flow at a low cavitation number. This indicates that pressure was concentrated on the pressure film. Consequently, cavitation can get rid of CRUD layers partially.

Effects of Digoxin on Ventricular Vulnerability During Atrial Defibrillation via Implanted Transvenous Catheter Electrodes in the Sterile Pericarditis Model

Because digoxin is often used in patients with atrial fibrillation, we evaluated its effects on the relative risk of inducing ventricular tachyarrhythmia (VT/NF) during synchronized atrial defibrillation shocks delivered through implanted transvenous catheter electrodes. Sterile pericarditis was created in 10 mongrel dogs. Two catheter electrodes with a 6 cm coil tip were inserted through the right external jugular vein and placed in the distal coronary sinus and in the right atrial appendage. To systematically achieve variable preceding ventricular coupling intervals (VCls). the ventricles were paced during sinus rhythm before delivery of the atrial shock in two protocols: 1) rapid pacing (8 stimuli, S 1 S 1 protocol); and 21 double extra stimuli (long-short intervalsl following 8 basic stimuli (S 1 S 2 S 3 protocol). The VCI (S 1 S 1 or S 2 S 3 )was shortened by 10 ms until the ventricular effective refractory period was achieved. After sensing the last paced ventricular beat. an atrial shock was delivered with a 2 ms delay at a shock intensity of 300 V (3.2–3.6 J), i.e., maximum shock intensity ofthe device. Atrial shocks were delivered 4 times at each VCI in each protocol. VCI was normalized by subtracting the OT interval in the surface ECG from the actual VCI. The relationship between the VCI and induction of VT/NF was evaluated in the drug free state and after administration of a therapeutic (50 μ g/kg. 5 dogs) or toxic (to obtain toxic arrhythmia. 5 dogs) dose of digoxin. Data are shown in mean ± SD, for each protocol (S 1 S 1 or S 1 S 2 S 3 ). To calculate a 99% probability of sinus rhythm (SR) after an atrial shock.logistic regression was used. No significant difference was observed before and after digoxin administration. The longest VCI that preceded VTNF induction was QT + 50 ms (290 ms) before digoxin and QT + 50 ms (310 ms) after digoxin. digoxin QT (ms) VTNF induction 99% probability of SR (ms) control 226 ± 22 6/377 (S 1 S 1 ) 27/303 (S 1 S 2 S 3 ) QT – 4 (S 1 S 1 ) QT + 71 (S 1 S 2 S 3 ) therap 237 ± 44 8/178 (S 1 S 1 ) 16/151 (S 1 S 2 S 3 ) QT + 1 (S 1 S 1 ) QT + 73 (S 1 S 2 S 3 ) toxic 220 ± 8 8/177 (S 1 S 1 ) 15/142 (S,S 2 S 3 ) QT + 1 (S 1 S 1 ) OT + 63 (S 1 S 2 S 3 ) Digoxin did not significantly change the risk of VT/NF induction during atrial defibrillation shocks delivered through transvenous catheter electrodes at maximum shock intensity. Shocks delivered at VCls longer than 310 ms resulted in no VT/NF induction.

Coherent anti-Stokes Raman spectroscopy of shock-compressed liquid nitrogen/argon mixtures

Single-pulse multiplex coherent anti-Stokes Raman scattering (CARS) was used to obtain vibrational spectra of 20%/80% liquid nitrogen/argon mixtures, shock compressed to several high-pressure/high-temperature states. A semiclassical model for CARS spectra was used to extract best fit vibrational frequencies, peak Raman susceptibilities, and Raman linewidths from the data. Up to a maximum single shock pressure of 17.1 GPa, the N2 vibrational frequency was found to increase monotonically with pressure. The vibrational frequencies measured in both the singly and doubly shocked N2/Ar mixtures correspond within experimental error to those for pure nitrogen at equivalent pressures and temperatures, implying that the influence of the interaction potential on the N2 vibrational frequency for the N2/Ar collision is not significantly different from that of a N2/N2 collision at these conditions. The transition intensity and linewidth data suggest that thermal equilibrium of the vibrational levels is attained in less than 10 ns at these shock pressures. Vibrational temperatures obtained were used to improve the potential function of argon used to calculate equation-of-state pressures and temperatures. The measured linewidths suggest that the nitrogen vibrational dephasing time decreased to about 1 ps at the highest pressure shock state.

Termination shock response to large‐scale solar wind fluctuations

The analysis of data recorded by the Voyager 2 spacecraft indicates the presence of large‐scale fluctuations in the solar wind ram pressure on the time scale of tens of days. The amplitude of the fluctuations is highly variable but often lies within a factor of 5 to 10 change from an average or mean value of the ram pressure. Since the spacecraft has presumably not encountered the termination shock yet, these fluctuations should eventually interact with the shock and thereby play a role in determining the shock location. Numerical solutions of the time‐dependent gasdynamic equations are used to simulate the response of the termination shock to fluctuations in the solar wind ram pressure comparable to those observed. The primary result of this study is that the maximum shock excursion due to the fluctuations is of the order of 1 AU, which is much smaller than that predicted by other studies. Additional simulations show that the limited movement is due to the fact that the time scale for the termination shock response is substantially larger than the time scale of the fluctuations. It is also shown that the heliopause acts as a barrier for the fluctuations and confines them to the heliosphere.

Study of lateral shocks observed during fork truck and pallet jack operations for the handling of palletized loads

AbstractThis study measured the lateral impact levels that occur when fork trucks are used to handle palletized loads. The existing ASTM‐D4003 standard on pallet marshalling recommends a 40 G, 10 ms shock or a 10G. 50ms shock to simulate impacts on pallet loads due to fork truck equipment. This study investigated the validity of these levels since no previous studies documenting these levels is provided in the ASTM standards.5 A set of ten impacts were conducted in the two different scenarios using boxes, bins and drums. These scenarios represent a palletized load on a fork truck impacting a similar stationary pallet load and an empty fork truck impacting a pallet load. Results are presented for each category of impacts performed in terms of average and maximum levels measured. The average peak acceleration for the data collected was 36 G and the average duration of impact was 4.3 ms. An analysis describing the limiting conditions for the shock acceleration G and the duration T as a function of the fork truck weight, impact speed, pallet weight and impact condition was determined. This showed that the impacts should have the product of maximum shock (in G) and duration (T) mms lying between 37.2 and 368 for half‐sine shocks.

Microstructures of carbon polymorphs formed in shocked compressed diamond powder utilizing an interaction of oblique shock waves

Microstructures of carbon polymorphs formed in diamond-powder compact obtained by shock compaction were investigated using high-resolution electron microscopy. Shock compaction was performed by impacting iron-flyer plate at impact velocities of 1.6 and 2.3 km/s. The maximum shock pressure was estimated as 18 and 56 GPa by numerical simulation for an initial powder density of 60% of the bulk density. The particle-size reduction resulted from the pulverization effects due to cracking, friction rubbing between particles, and a tensile wave. The local heating of particle surfaces and plastic deformation promoted the phase transformation from diamond to low-density phases of carbon: turbostratic carbon, i-carbon, and α-carbyne. The higher the shock pressure, the more the effect of particle-size reduction and the local heating were enhanced. Chain-like and ribbon-like turbostratic carbon, and spherical “γ-carbon” developed from gaseous carbon generated by jetting from the diamond-particle surface were found at the 56 GPa region in the compact. The formation of “γ-carbon” was assumed to proceed through vapor → liquid → solid sequences.

Coherent anti-Stokes Raman spectroscopy of shock-compressed liquid nitrogen/carbon monoxide mixtures

Vibrational spectra of liquid nitrogen/carbon monoxide mixtures, shock compressed to several high-pressure/high-temperature states, were obtained using single-pulse multiplex coherent anti-Stokes Raman scattering (CARS). The experimental spectra were compared to synthetic spectra calculated with a semiclassical model for CARS intensities and using best fit vibrational frequencies, peak Raman susceptibilities, and Raman linewidths. Up to a maximum shock pressure of 9.3 GPa, both the N2 and CO vibrational frequencies were found to increase monotonically with pressure but depended strongly on the nitrogen/carbon monoxide mixture ratio. An empirical fit of the Raman frequency shifts incorporating previously published neat nitrogen and carbon monoxide data, using a functional form dependent on pressure, temperature, and mixture ratio, accurately describes both the N2 and CO shifts. The transition intensity and linewidth data suggest that thermal equilibrium of the vibrational levels is attained in less than 10 ns at these shock pressures and the vibrational temperatures obtained were used to improve the potential function used to calculate equation-of-state pressures and temperatures. The measured linewidths were different for N2 and CO and suggest that the vibrational dephasing time decreased to a few ps at the highest pressure shock state.

Comparison of mechanical fatigue with thermal fatigue in ceramics

Thermal fatigue studies have shown a saturation of damage accumulation with cycling. Similar damage saturation has been observed for mechanical fatigue. This study compares damage saturation behavior for mechanical fatigue with thermal fatigue in ceramics. Studies of thermal fatigue of ceramics show that the accumulation of thermal shock cycling damage depends on the magnitude of the thermal shock, [Delta][Tau] (where [Delta][Tau] is the temperature change of the specimen from the initial temperature to the temperature of the quenching medium). Three distinct regimes of damage accumulation exist depending on the magnitude of [Delta][Tau]. For the first regime where the thermal shock cycling is below [Delta][Tau][sub c], a critical thermal shock value, there is no thermal damage detected. In the second regime where [Delta][Tau] is higher than [Delta][Tau][sub c] but lower than [Delta][Tau][sub 1], the accumulating microcrack damage initially induces a rapid change in material property P. As the number of cycles increases a steady state value of properties is reached. For the third regime [Delta][Tau] is higher than [Delta][Tau][sub 1] and rapid crack growth results in fracture of the specimen. Each regime depends on [Delta][Tau] since, for a given specimen and quenching medium, the maximum thermal shock stress is proportional tomore » [Delta][Tau]. So characterization of each regime by [Delta][Tau] is indicative of the maximum stress applied by the thermal shock.« less

The Effects of Ultrasound-Guided Shock Waves During Early Pregnancy in Sprague-Dawley Rats

Pregnancy is a contraindication to extracorporeal shock wave lithotripsy (ESWL) because of its possible harm to the embryo or fetus caused by shock waves or ionizing radiation. In this study timed-pregnant rats were subjected to shock waves early in gestation using a lithotriptor having ultrasound imaging. In a pilot group undergoing immediate laparotomy, it was determined to what extent the pelvic structures were effected. Then a test group was exposed to shock waves and carried to near term pregnancy along with an identical group of pregnant, sham procedure rats. A laparotomy all were inspected for fetal viability, fetal abnormalities, and maternal organ damage. Fetuses located nearest the focal area of maximum shock wave energy showed lower mean weight than controls. There was no recognizable gross or microscopic fetal damage.