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通过对缺口试样冲击弯曲断裂过程的研究,论证了示波冲击P～δ图与试样断口结构的对应关系.将冲击值α_(?)分解为裂纹萌生功α_i与裂纹扩展功α_p,并研究这两部分功随温度降低时的变化规律,发现在韧～脆转变的温度范围内,α_K的降低主要受α_p的降低所控制,而α_i基本上保持不变.同时得到,对于所研究的两种材料,在韧～脆转变温度范围内,冲击值α_K与断口上纤维状组分FF%有线性关系:α_K=α_i+B×FF%.于是提出了求取裂纹扩展功的简便办法. 借助电子显微镜,观察分析了断口上不同区域的微观形貌以及随温度降低时断裂机制的变化,从微观上解释了不同材料低温脆断抗力的差别.
The impact relationship between the oscillometric impact P ~ δ diagram and the fracture structure of the specimen is demonstrated by studying the impact fracture bending process of the notched specimen. The impact value α_ (?) Is decomposed into the crack initiation function α_i and the crack propagation function α_p The results show that the decrease of α_K is mainly controlled by the decrease of α_p and α_i is basically unchanged in the temperature range of tough to brittle transition.At the same time, For both materials, the impact value α_K has a linear relationship with the FF% of the fibrous component on the fracture surface in the range of toughness to brittle transition temperature: α_K = α_i + B × FF%. Therefore, a simple and convenient method for calculating the crack extension work is proposed. By means of electron microscope, the microscopic morphology of different regions on the fracture surface and the change of fracture mechanism as the temperature decreases were observed and analyzed, and the difference of the brittle fracture resistance at different temperatures was explained microscopically.