Issue34

X. Zhengbing et alii, Frattura ed Integrità Strutturale, 34 (2015) 574-579; DOI: 10.3221/IGF-ESIS.34.63 578 Figure 4: Correlation between peak strain and strain rate. A NALYSIS OF DYNAMIC DAMAGE MECHANISM t has been found from Fig. 1 and 2 that, two materials obviously change their forms under the effect of impact load, and concrete is broken to even blocks no matter strain rate is high or low, while sandstone changes into different forms under impact load with different strain rate, relatively large block under low strain rate and relatively small and powdered block under high strain rate [10]. To present dynamic damage mechanism of two materials more clearly, we use specific energy absorption to describe toughness of materials. In the view of physics, it means the stress wave energy absorbed by sample material in unit volume. Fig. 5 demonstrates the correlation between specific energy absorption and strain rate of concrete and sandstone. Specific energy absorption/(KJ/m 3 ) Figure 5: Correlation between specific energy absorption and strain rate. The figure above showed that specific energy absorption increases linearly with the increase of strain rate and the fitted formula is as follows: 2 2 ( ) 94.28 12.20 0.96849 ( ) 1473.45 29.91 0.88962 SEA C R SEA S R                (3) Energy absorption ability of sandstone is more significant than concrete. When strain rate becomes higher, specific energy absorption of sandstone varies more obviously. Taking dynamic damage forms of two materials into account, we can summarize that, dynamic forms of materials is correlated to specific energy absorption value. To be specific, dynamic I