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起爆方式對間隔裝藥應力場分布及裂紋擴展的影響

Effect of the detonation method on the stress field distribution and crack propagation of spacer charge blasting

  • 摘要: 通過模型實驗研究了不同起爆方式對空氣間隔裝藥炮孔兩側損傷分布的影響規律,借助數字圖像相關實驗系統,獲取了全場應變場演化過程及空氣段應變衰減規律,同時借助透射式焦散線實驗系統,探究了起爆方式對預制裂紋動態斷裂行為的影響。實驗結果表明:柱狀藥包炮孔兩側產生的損傷范圍具有顯著的分形特征。采用外側起爆時,空氣段中心兩側均產生損傷,而采用其他起爆方式時,空氣段均未出現損傷。不同起爆方式對空氣段應變場徑向壓應變的影響主要體現在應變大小、衰減速度兩個方面,對軸向拉應變的影響主要體現在時效性、衰減速度兩個方面。不同起爆方式下預制裂紋端部斷裂行為差別較大。采用內側起爆、外側起爆時,裂紋均為水平擴展,呈現典型Ⅰ型裂紋,裂紋起裂主要由拉伸破壞引起,異側起爆時裂紋起裂為Ⅰ?Ⅱ混合型,具體表現為拉?剪破壞。基于數值模擬軟件LS-DYNA,解釋了預制裂紋端部起裂成因,得到了孔壁處應力場分布規律,不同起爆方式對炮孔軸向孔壁處壓力分布影響顯著,裝藥段主要體現在壓力峰值位置和壓力分布形態兩個方面,空氣段主要體現在壓力峰值大小和壓力分布形態兩個方面。

     

    Abstract: In this study, a numerical simulation is used to study the effect of initiation methods on the damage distribution on both sides of an air-spaced charge blasthole using lead azide as the explosive and polymethyl methacrylate as the experimental material. The digital image correlation system determines the evolution of the global strain field and the strain attenuation pattern of the air section, and the dynamic caustics experimental system investigates the effect of detonation methods on the dynamic fracture behavior of the precrack. The experimental results show that the damage induced on both sides of the cylindrical charge blasthole has significant fractal properties. The damage degree corresponding to each initiation point of the charge section is the smallest, and the damage degree gradually increases along the detonation path. When it approaches the noninitiating end, the damage degree reduces further due to a decrease in the energy accumulation rate and a portion of the energy dissipation. When the outer detonation method is employed, both sides of the central air section are damaged, but not when the other detonation methods are used. The effect of different initiation methods on the radial compressive strain of the air segment strain field is mostly reflected in the strain size and strain decay rate, whereas the effect on the axial tensile strain is primarily reflected dynamically and in the decay rate. The attenuation coefficient of the strain field is the greatest when the outer detonation is initiated, regardless of whether the strain is radial or axial. The fracture behavior of the precrack end varies considerably depending on the detonation method. When both the inner and outer detonations are used, the crack exhibits a typical I type generated by tensile failure. When antarafacial detonation is used, the crack initiation is mixed I–II, and the specific performance is tensile-shear destruction. The origin of the crack initiation at the end of the precrack is described using LS-DYNA numerical simulation software, and the distribution pattern of the stress field at the blasthole wall is derived. The pressure distribution along the axial hole wall of the blasthole is considerably affected by different detonation methods. The charge section is mainly reflected in the position of the pressure peak and the pressure distribution shape, whereas the air section is primarily reflected in the size of the pressure peak and the pressure distribution shape.

     

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