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中文核心期刊

加载速率和几何尺寸对国产A508-III钢断裂行为影响的实验研究

EXPERIMENTAL STUDY ON THE EFFECT OF LOADING RATE AND GEOMETRIC SIZE ON THE FRACTURE BEHAVIOR OF CHINESE A508-III STEEL

  • 摘要: 由加载速率和几何约束改变而引起的压力容器钢韧脆转变问题是核能安全领域亟待解决的关键问题. 为了准确分析国产A508-III钢的动态断裂行为, 借助INSTRON VHS高速材料试验机, 开展了不同加载速率和几何尺寸条件下的国产A508-III钢的断裂韧性试验, 研究了加载速率和几何尺寸等因素对国产A508-III钢动态断裂韧性的影响. 研究表明, A508-III钢具有良好的抗冲击韧性, 随着加载速率的提高, 试样的总冲击吸收能基本保持恒定, 裂纹萌生吸收能量不断上升, 而裂纹扩展吸收能量呈下降趋势. Ja阻力曲线和条件起裂韧性JQ随着几何约束的增加而降低, 随加载速率的增加而升高. 当达到某一临界速率时, 条件起裂韧性JQ基本恒定, 试样断裂方式也由韧性断裂转变为韧−脆−韧混合断裂. 由于出现混合断裂模式, 发生脆性断裂时的最大J积分值Jmax更适于描述国产A508-III钢的断裂韧性演化规律. 随着试样面外几何约束的降低, Jmax随Δam的增加而线性增大. 试样面内几何约束越高, Jmax与Δam之间的线性关系斜率越大. 随着试样几何约束的增加, 材料的韧脆转变速率增加, Jmax值下降. 改变几何约束只能在有限的加载速率范围内改变材料的断裂方式, 当加载速率超过某个临界值时, 加载速率成为影响材料断裂方式的主要因素.

     

    Abstract: The ductile-brittle transition of pressure vessel steels caused by the change of loading rate and geometric constraint is a key issue that needs to be solved in the field of nuclear energy safety. In order to accurately analyze the dynamic fracture behavior of Chinese A508-III steel, the fracture toughness tests of Chinese A508-III steel under different loading rate and geometric size were carried out by using INSTRON VHS high-speed material testing machine to investigate the effect of loading rate and geometric size on the dynamic fracture toughness of Chinese A508-III steel. The results show that the Chinese A508-III steel has good impact toughness. With the increase of loading rate, the total impact absorbed energy of the specimen basically remains constant, the absorbed energy of crack initiation increases, while the absorbed energy of crack propagation decreases. The Ja resistance curve and the conditional initiation toughness JQ decrease with the increase of geometric constraint, but increase with increasing loading rate. When loading rate reaches a critical value, the conditional initiation toughness JQ basically keeps constant and the fracture mode of the specimen changes from ductile fracture to ductile-brittle-ductile mixed fracture. The maximum J-integral value Jmax is more suitable to describe the fracture toughness evolution of Chinese A508-III steel when brittle fracture occurs due to the occurrence of mixed fracture mode. With the decrease of out-of-plane geometric constraints, Jmax increases linearly with the increase of Δam. The higher the in-plane geometric constraint of the specimen has, the greater the slope of the linear relation between Jmax and Δam presents. As the geometric constraint of the specimen increases, the ductile-brittle transition loading rate of the material increases, but the value of Jmax decreases. Changing the geometric constraint can only change the fracture mode of the material within a finite loading rate range, and when the loading rate exceeds a certain threshold value, the loading rate becomes the main factor affecting the fracture mode of the material.

     

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