【摘要】 通过对低合金钢 (WCF 6 2 )在 - 10 0℃不同加载速度下的缺口试样四点弯曲 (4PB)实验及对断口和截剖金相试样的观察 ,研究了加载速度对低合金钢缺口试样解理断裂临界事件的影响 .结果表明 :加载速度从 30mm min增加到 5 0 0mm min时 ,解理断裂的临界事件由晶粒尺寸裂纹的扩展控制到扩展和起裂的混合控制再转变为起裂控制 ,其根本原因是材料的屈服应力σy 随加载速度的增加而升高 .临界事件随加载速度的变化决定了缺口韧性随加载速度的变化更多还原

【Abstract】 Four point bending (4PB) test of notched specimens of a low alloy steel WCF 62 is carried out at -100 ℃ with different loading rates. And the fracture surfaces and metallographic sections are observed. The influence of loading rate on the critical event of cleavage fracture in notched specimens of the low alloy steel is investigated. It has been found that, when the loading rate is increased from 30 mm/min to 500 mm/min, the critical event of the cleavage fracture changes from the propagation control of a grain sized crack to a mixed control of propagation and nucleation and, then, to nucleation control. The reason of this change is that the yield stress σ y of the steel increases with the loading rate. The change of the critical event with loading rate determines that of the notch toughness with loading rate.更多还原