PSI - Issue 32

Anatoly M. Bragov et al. / Procedia Structural Integrity 32 (2021) 340–344 Author name / Structural Integrity Procedia 00 (2019) 000–000

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After processing the deformation pulses of the measuring bars recorded in the experiments, deformation curves of the sand-lime brick were plotted under several loading modes in terms of the strain rate. The averaged strain diagrams obtained during the tests are shown in Fig. 1. In this figure, in parallel with the dependences σ(ε) (left vertical axis - stress), depicted by solid lines, the appropriate histories of strain rate έ(ε) (right vertical axis - strain rate) are shown by dashed lines and the same colors. The form of dynamic deformation diagrams obtained under conditions of uniaxial stress state of experimental samples is similar to the form of dynamic deformation diagrams of other brittle materials, for example, concrete in Bragov et al. (2015). An increase of stresses and strains occurs until the stresses achieve of maximum value in the first section of the deformation diagram (loading branch). After that, the diagram has extended fracture section, characterized by decrease of the stresses with increase of strains (fracture branch).

Figure 2. Dynamic deformation diagram of the sand-lime brick at fracture The energy spent on deformation of a unit volume of sand-lime brick samples was determined on the basis of the obtained deformation diagrams:        ∙    , where A - the work of force F expended on deformation of a cylindrical sample volume V=S * L 0 . The total energy E spent in the process of loading a sample can be represented as the sum of two components E = E 1 + E 2 (Figure 2). The first term E 1 is the energy spent on deformation of the sample until the stresses achieve of maximum value. It was called the pre-fracture energy. The second term E 2 (post-fracture energy) characterized the avalanche-like process of fracture of the sample. The specific energy absorption graphs obtained by the numerical integration of the σ(ε) curves for several loading modes of sand-lime brick are shown in Figure 3. Strain rate histories έ(ε) (right vertical axis - strain rate) are shown by dotted lines parallel to the dependences E (ε) (left vertical axis - energy) displayed by solid lines in this figure. The markers on the curves correspond to a specific loading mode.