The results of the experimental determination of the spallation strength of polymer materials are presented using samples made of acrylic glass and polystyrene as examples. The study was conducted in the energy density range of 35–1500 J/cm2. Despite the similar physical and technical parameters of the examined polymers (acrylic glass, polystyrene, epoxy resins), the nature of their failure under pulsed volumetric energy release is different [1, 2]. It has been shown that, in polystyrene, cracks originate directly from the energy release zone, while in acrylic glass, a transparent undamaged area is observed next to the energy release zone, beyond which cracks form. The spallation strength of polystyrene was determined to be σ = 0.35 GPa, which is similar to the spallation strength of acrylic glass. This is interesting, as the spatial localization of the failure zones in samples made from these two materials differs significantly.

To study the strength characteristics of various materials, experiments are carried out on the interaction of high-energy electron beams with targets made of these materials [1].As a result of the experiment, it is possible to assess the degree of surface destruction, the presence of chips on the back side, and measure the pressure exerted on the target.Modeling of such experiments often does not take into account some features of installations and additional external factors.In this work, we simulated the interaction of an electron beam with a target, the subsequent appearance of anode and cathode plasmas, the interaction of these plasmas in the diode gap, and the influence of this interaction on the propagation of shock waves inside the target.The experiments were carried out on the Squid high-current electron accelerator (current up to 40 kA, voltage up to 350 kV, pulse duration about 100 ns, electron energy in the beam about 0.35 MeV).Using measurements of the total voltage drop, the electron beam current was calculated, which was subsequently used in the simulation.Chronograms of the propagation of shock waves inside the target were obtained.Modeling of the effect of REB on the sample under study was carried out using the method developed at the Institute for Problems of Mathematics named after.M.V.Keldysh RAS MARPLE code [2], supplemented with a cathode model [3].Calculations were carried out in the approximation of a single-temperature 3-dimensional hydrodynamic model, taking into account thermal conductivity and volumetric energy losses due to bremsstrahlung.Calculations were performed using wide-range equations of state of matter.The mathematical modeling results of the processes occurring in the Squid generator's of highcurrent beams of relativistic electrons diode gap were obtained and analyzed.The influence of the interaction of plasma flows from the anode and cathode on the nature and propagation speed of shock waves inside a polymer target has been studied.The simulation results coincide with the experimental data.

An explanation is proposed for a specific feature in the general scenario of the destruction of non-brittle polymers under the action of a shock wave induced by a high-power electron beam found in several experiments. The remoteness of the cracking region to a finite depth from the surface of the irradiated material is related to the 3D propagation of elastic waves. The universality of the effect is demonstrated on the simplest isotropic model, which shows that high tensile stresses are efficiently generated inside the target at sufficiently large transverse and longitudinal dimensions even with disregard of nonlinear and shear processes.

An experimental study of the effect of high-current electron beams on crystals made of polycrystalline tungsten and corrosion-resistant ferritic-martensitic steel EK-181 was carried out, as well as a numerical simulation of the process of interaction of the beam with the target, in which the energy of the electron beam was absorbed in the near-surface layers of the samples under study. The experiments were carried out on the Kalmar high-current electron accelerator at an average pulse energy of E ≈ 100 ± 20 J (pulse duration at half maximum 100 ns). During the experiments, samples were irradiated from one to ten times. Numerical modeling was performed using electron spectra calculated on the basis of data (currents and voltages in the diode gap) obtained as a result of electrical measurements. The difference in the nature of destruction of tungsten and steel was demonstrated. It has been shown that tungsten begins to crack after three-pulse exposure with an energy of about 100 J, which correlates well with tests on other types of installations. On steel, minor cracking was observed only after 8–10 pulses of exposure. Numerous traces of droplets of melting and redeposition of the target material were found on the surface of the steel target. For both materials, the specific amount of energy absorbed in the region of interaction of the electron beam with the target was estimated.

Changes in the chemical and phase compositions, as well as the formation of micro- and nanostructured objects in syntactic foams consisting of tungsten-modified glass microspheres and a polymeric binder based on a phenylsilsesquioxane— b -dimethylsiloxane block copolymer, caused by the action of a single relativistic electron beam with an average energy in the range of 180–260 keV and a peak current power in the range of 4.5–6.8 GW were studied by scanning electron microscopy and X-ray phase analysis. It was demonstrated that tungsten and tungstic acid hydrate react with products of polysiloxane decomposition to give WO 3 , WO 2 , δ-WO 2 , and Na 2 WO 4 under extreme conditions ( T > 1600 K and pressures in the range of 3–8 GPa) near the surface of the microspheres. The observation of irregularly shaped droplets and “solidified foam” structures found on the inner surface of collapsing microspheres suggests that the formation of filamentous structures is preceded by high-temperature reactions involving products of high-temperature pyrolysis of polysiloxane and tungsten compounds.

We studied the impact of a powerful relativistic electron beam on polymer targets at energy density up to 1 kJ/cm2. Experiments were carried out on high current electron accelerator “Kalmar” at beam current up to 45 kA and electron energy up to 300 keV. Laser shadow streak image was used to visualize the dynamics of shock waves in transparent materials. Three-dimensional numerical simulation of gasdynamic phenomena in the diode gap and elastoplastic phenomena that depend on them in the target material was performed using MARPLE3D multiphysics software package. The new technique was designed for end-to-end modeling including heating and evaporation of the target under the action of the electron beam and nonlinear wave processes leading to internal fractures and spalling phenomena in the target material. We use wide-range equation of state for the description of the liquid and solid phases of matter at low temperatures. Appropriate modeling of this complex problem is based on high resolution numerical methods as well as on high performance computing. The implemented computer models are verified by experimental data. The developed software can be used for numerical stress-strain analysis of various structural units loaded by strong pulsed forces and/or energy fluxes.

The destruction of an energetic condensed system based on glycerol trinitrate, polyether urethane, and aluminum powder upon exposure to a relativistic electron beam with a maximum energy of 310 keV, a total duration of 170–180 ns, and an average flux density of 200–215 J/cm2 was studied by nanosecond electron-optical chronography, scanning electron microscopy, and energy dispersive analysis. The effect of the generation of pulsed electric fields and shock-wave loads accompanying relativistic electron beam absorption on the mechanical damage to samples of energetic condensed systems is discussed.

Transformations caused by the action of a relativistic electron beam with the half-amplitude pulse duration of 100 ns and power of 6.3–9.2 GW on a syntactic foam formed by glass microspheres and siloxane block copolymer and on the polymer base of the syntact were studied by scanning electron microscopy and X-ray diffraction. The collapse of glass microspheres in the syntactic foam under the action of the relativistic electron beam leads to the formation of elongated structures of micrometer size and of whisker structures with the minimal diameter of 40 nm (nanofibers). The distribution of the fields of absorbed doses and shock wave pressure was estimated using Monte Carlo methods. The revealed changes in the chemical and phase composition of the syntactic foam and its polymer base, caused by the single action of the relativistic electron beam, are discussed.

This paper presents the results of a study of the impact of a high-current electron beam of the Kalmar accelerator with a cutoff electron energy of up to 350 keV on igdantine and low molecular weight nitrile butadiene rubber SKN-18-KTR. The materials are similar in mechanical and physical properties, but differ in chemical structure. It has been shown that, at a beam energy of less than 600 J, the destruction of igdantin begins to a depth significantly exceeding the electron range, while nitrile rubber withstands a load of more than 700 J without significant damage. It is demonstrated that the dynamics of plasma expansion from the surface of igdantin regularly demonstrates specific.

A physical experiment performed to test a mathematical model for the generation of bremsstrahlung by electrons and the formation of an electromagnetic field during its scattering is considered. During the experiment, a high-current electron accelerator irradiates the converter target. The resulting bremsstrahlung generates a flux of emission electrons and an electromagnetic field in a sealed chamber. A mathematical model of the measuring circuit used for the experimental determination of the electric current in the chamber is developed. The results of physical and computational experiments simulating them coincide with satisfactory accuracy. It is established that the necessary condition for confirming the model is to take into account the measuring equipment in the computational experiment and use directly measured values for comparison.

An explanation for a feature found in several experiments in the general picture of the destruction of non-brittle polymers under the influence of a shock wave initiated by a powerful electron beam is proposed. The distance of the cracking region from the surface of the material affected by the beam to a finite length in depth is associated with the three-dimensional nature of the propagation of elastic waves. The universality of the effect is demonstrated by the simplest isotropic model, which shows that large tensile stresses are effectively generated inside the target at its sufficiently large transverse and longitudinal size, even without taking into account nonlinear and shear processes.

An experimental verification of the mathematical model of the generation of bremsstrahlung radiation by electrons and the formation of an electromagnetic field during its scattering is considered. A physical experiment was used in which a high-current accelerator formed bremsstrahlung in a target-converter, as well as an emission electron flux and an electromagnetic field in a sealed chamber. The results of physical and simulating computational experiments coincided to within an order of magnitude.

Рассмотрен физический эксперимент, выполненный для проверки математической модели генерации электронами тормозного излучения и образования электромагнитного поля при его рассеянии. В ходе эксперимента сильноточный ускоритель электронов облучал мишень-конвертор. Образовавшееся тормозное излучение генерировало поток электронов эмиссии и электромагнитное поле в герметичной камере. Разработана математическая модель измерительной цепи, использованной для экспериментального определения электрического тока в камере. Результаты физических и моделирующих их вычислительных экспериментов совпали с удовлетворительной точностью. Установлено, что необходимым условием подтверждения модели является учет измерительного оборудования в вычислительном эксперименте и использование для сравнения непосредственно измеряемых величин.

An informative and very clear experimental method for studying the processes that accompany the propagation of shock waves in transparent materials under powerful pulsed exposure is proposed. The method is based on analysis of the shadow streak image formed by probe laser radiation that passes through a sample. The sensitivity of the method is estimated. The method was tested on samples of polymethyl methacrylate (PMMA) and K-8 optical glass at electron beam currents of up to 45 kA and electron energies of up to 300 keV. The effectiveness of the proposed method is demonstrated.