Abstract
The originally performed perforation experiments were extended by compression and tensile dynamic tests reported in this work in order to fully characterize the material tested. Then a numerical model was presented to carry out numerical simulations. The tested material was the common brass alloy. The aim of this numerical study was to observe the behavior of the sample material and to define failure modes under dynamic conditions of impact loading in comparison with the experimental findings. The specimens were rectangular plates perforated within a large range of initial impact velocities V0 from 40 to 120 m/s and in different initial temperatures T0. The temperature range for experiments was T0 = 293 K to 533 K, whereas the numerical analysis covered a wider range of temperatures reaching 923 K. The thermoelasto-viscoplastic behavior of brass alloy was described using the Johnson–Cook constitutive relation. The ductile damage initiation criterion was used with plastic equivalent strain. Both experimental and numerical studies allowed to conclude that the ballistic properties of the structure and the ballistic strength of the sheet plates change with the initial temperature. The results in terms of the ballistic curve VR (residual velocity) versus V0 (initial velocity) showed the temperature effect on the residual kinetic energy and thus on the energy absorbed by the plate. Concerning the failure pattern, the number of petals N was varied depending on the initial impact velocity V0 and initial temperature T0. Preliminary results with regard to temperature increase were recorded. They were obtained using an infrared high-speed camera and were subsequently compared with numerical results.
Highlights
Dynamic tests are rarely coupled with thermal analysis since it is not easy to reach uniform temperature in the plate and gas gun is not frequently provided with a thermal chamber
The new experimental results of unidirectional tests of tension and compression, allowing to estimate the material constants and to ensure accurate FE simulations, are presented in this chapter. They are complimentary to a number of dynamic perforation tests previously conducted at high impact velocity [9] in order to understand the thermo-mechanical behaviour of brass and to evaluate its mechanical properties
Compression tests were carried out at room temperature for four selected impact velocities corresponding to three different strain rates
Summary
Dynamic tests are rarely coupled with thermal analysis since it is not easy to reach uniform temperature in the plate and gas gun is not frequently provided with a thermal chamber The usual approach is to carry out perforation tests at room temperature and to extrapolate results using numerical simulations at high temperatures knowing the constitutive relation. Standard compression and tension tests resulted in stress–strain curves and provided constants to the selected constitutive relation They determined failure strains which were taken into consideration in the numerical model. The parametrical analysis of the failure criterion was carried out to demonstrate its temperature and strain rate dependence It consisted of observing the petaling failure mode and fitting the numerical ballistic curves to the experimental ones in order to propose the failure criterion value
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