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本文通过裂隙亚临界扩展的分析,提出一个计算低、中等应力率下裂隙断裂起动应力的新公式。通过冲击载荷下裂隙尖端应力强度因子-时间关系的积分,得到计算高、中等应力率下裂隙的断裂起动应力的公式。两公式的结合得到一个适用于从低到高各种加载速率的计算裂隙的断裂起应力的一般表达式。文章还分析了多裂隙材料的临界失稳断裂,提出了在高加载速率下材料的σ_(fi)-σ曲线是材料内所有裂隙的σ_(fi)-σ曲线的包络线的新观点,并由此得出布高加载速率下材料的断裂起动应力与加载速率的立方根成正比的结论。
In this paper, through the analysis of the subcritical expansion of fractures, a new formula for calculating the fracture initiation stress at low and medium stress rates is proposed. By integrating the stress intensity factor-time relationship at the crack tip under impact loading, the formula for calculating the fracture initiation stress at cracks at high and moderate stress rates is obtained. The combination of the two formulae yields a general expression of the fracture initiation stress for a calculated fracture that applies from low to high loading rates. The paper also analyzes the critical instability fracture of multi-fractured materials and proposes a new view of the σ_(fi)-σ curve of the material at high loading rates as the envelope of the σ_(fi)-σ curve for all fractures in the material. It is concluded that the fracture initiation stress of the material is proportional to the cubic root of the loading rate at the loading rate.