• Material model parameters identification of blast environment

    Security & Future, Vol. 2 (2018), Issue 3, pg(s) 142-145

    In terms of designing or building new protective and security structures or equipment as a physical component of force protection, experimental verification of analytical or numerical calculations and vice versa becomes necessary. While the experiment can be performed on individual components, complex assessment of more complex variants or performing a parametric study is becoming more and more relevant in modelling and simulation domain. For this reason, there is a clear necessity to find the right connection between numerical simulation and experiment.
    Fast, nonlinear processes require nonlinear material models to capture the rate of deformation and material behaviour under extreme loads such as the effect of explosions or the impact of a projectile, i.e. the effects, which the theories and practices of protection of the population and troops are trying to minimize. The important part of the accuracy of computational models is the correct identification of the parameters of material models used in the simulations.
    This paper deals with the simulation of explosion and its effects and identification and optimization of material parameters of the environment in which the explosion and the shockwave propagates, with a focus on the soil material model. The inverse identification method is based on a combination of the experimental measurement data and the computational methods implemented in the finite element solvers and optimization programs. The simulation proceed from experimental measurement curves of blast effects. For measured parameter in the air overpressure at specific measuring points was chosen, while ground-propagating shock wave was evaluated by measuring
    acceleration values. The numerical simulation took place in the LS-Dyna software environment interconnected with the Optislang optimization program.

  • Non-destructive methods in concrete blast resistance assessment

    Security & Future, Vol. 2 (2018), Issue 2, pg(s) 91-93

    The paper deals with the assessment of material used for the construction of protective structures and elements of military and civilian infrastructure. Since the main reason of protective structures is to protect personnel, equipment and equipment from attack by hostiles, it is necessary to conduct tests of material ballistic resistance and resistance against contact or distant explosion when choosing suitable materials for building protective structures.
    In order to achieve the aim of this work, from several basic groups of NDT methods was selected. Based on the evaluation of their advantages and technical possibilities, representatives from 4 principally and physically different groups of NDT methods were selected, i.e. visual method, ultrasonic method, hardness method and resonance method.
    The practical part of the paper is focused on the design of the material evaluation by means of NDT methods. In the first stage, the setting of the measuring devices was performed. Laboratory measurement was then carried out, on the basis of which calibration relations were established to determine the basic mechanical properties of the material. The material evaluation is described fort both, newly designed elements and for material in already built structures. Laboratory and field tests were performed during the assessment of the material of the newly constructed elements. In laboratory tests, the test specimens were evaluated by NDT methods. In the field tests, the test specimen was subjected to an explosion, the effect of which was subsequently evaluated by NDT methods and compared with the results of the same method prior to loading.