2Eis the Gurney factor(or Gurney specific energy), Gurney found the linear relation between the Gurney factor and explosive speed eD through many tests. 2 520 0.28 e E D + ＝ (5) In order to simplify the research, this paper chooses spherical fragments with diameter 0.05m and initial speed 1700 1 m s− g . 3. Models and material parameters 3.1 Bridge model In order to explain the mechanism clearly, a simple square section with 1m length of each side is used. The superior border has 3 longitudinal steels with diameter 6mm and inferior border has 3 longitudinal steels with diameter 12mm, shown as figure 2. Figure.2 Beam section and 3-D model 3.2 Constitutive relation of the concrete RHT model [2] was built by Riedel, Hiermaier and Thoma in 1999. The premise of the model formula is that the internal energy of the porous-material and compact-material under the same pressure and temperature are equal. The thermo-motive performances of the concrete under high pressure and the compression behaviors under low pressure will be described clearly by RHT. When the concrete is compacted enough, its state equation is shown as figure 3. Figure.3 RHT constitutive relation of concrete
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