PSI - Issue 50

Alekseev D.I et al. / Procedia Structural Integrity 50 (2023) 17–26 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Research of high strain deformation of materials has a long history, and it practically was based on experimental data, which were obtained by various testing methods for verification of different dynamic plasticity and fracture models, e.g., Johnson and Cook (1985). Dynamic characteristics of materials can be studied with the use of various methods like ones described in Kolsky – Hopkinson’s method described by Kolsky (1949), Taylor’s experiment described by Taylor (1948), spall method described by Mayfield and Rogers (1960). Mentioned various testing methods obviously have their own advantages and disadvantages and, in combination, can provide the information for verification of materials plasticity and fracture models, e.g., two split advanced methods: Hopkinson-Kolsky bar testing described by Smirnov et al. (2020) and spall fraction testing described by Kanel et al. (2020) and Bragov et al. (2017). The first method allows receiving the experimental strain-stress curve, but is limited by strain rate of 10 4 1/s. The second one allows obtaining spall strength in a wide range of strain rates up to 10 9 1/s as shown by Podurets et al. (2011), but it is difficult to verify the tensile plasticity models using this method, since the tensile wave is preceded by a compression wave. The main feature of each method is the way of creating pulse loading, which can be implemented by various mechanical pulse sources, e.g., using a compressed gas under pressure, detonation of an explosive, a pulse laser, etc. Along with mentioned traditional pulse energy sources, it is also possible to use high energy density of the strong pulse magnetic field as a source of pressure pulse. The parameters of magnetic pressure are determined by the parameters of the magnetic field as described by Knoepfel (1970), what allows recording the pressure pulse in time by measuring of the current or magnetic field. Testing of conductive materials using strong pulsed magnetic fields has a number of specific features influencing the deformation process, e.g., the Joule heating, the Lorentz force and the electroplastic effect described by Troitskiy and Stashenko (2017). Various magnetic pulse loading methods have been used in a series of works performed by Krivosheev et al. (2005, 2015, 2018, 2020), Morozov et al. (2014, 2016, 2018), the results of which have shown the effectiveness of magnetic pulse loading methods for testing both dielectric and conductive materials at high strain rate. The assessment of the deformation process of materials under extreme loading conditions is important in the study of electrophysical processes, such as the influence of the strength characteristics of a material in the calculation and creation of axisymmetric quasi-force-free magnets descried by Shneerson 2008, or in the design of various electrophysical apparatuses and installations, an example of which is the study of the process of deformation of the current-carrying parts of protective devices used in complex electrical installations described by Manzuk et al. (2013, 2017, 2021). The purpose of this work is to analyze the used loading schemes for the study of materials characteristics and behavior under direct high strain rate tension conditions with use of pulse magnetic fields, and to compare available experimental data with possible analytical solution to find a workable predictive model for high strain rate tension analysis. 2. Magnetic methods of forming controlled pressure pulses Several methods of material testing under magnetic pulse loading, including testing of samples with crack type macro defect (Fig. 1a), uniaxial tension (Fig. 1b, e), bending impact test (Fig. 1c), spall test (Fig. 1d), Hopkinson Kolsky method (Fig. 1f), ring expansion (Fig. 1g, h), are shown in Fig. 1. Magnetic systems with the following shapes of inductor and driver are used in shown methods: a. Thin flat conductors (Fig. 1 a, b, c, d), which can be made in the form of the simple, direct and return conductors and quasi-coaxial conductors, which form significantly reduce the induced current in the test sample. b. Spiral solenoid (Fig. 1e, f) located near the conducting disk. The disk transfers mechanical pressure to the sample directly (Fig. 1e) or through the Kolsky – Hopkinson split cylinders (Fig. 1f). c. Thin-walled conducting cylinders (Fig. 1g) or a cylindrical solenoid with a conductive ring (Fig. 1h).