不同方法评定核压力容器用A508CL3钢动态断裂韧性的比较

Comparison of Several Methods for Determining the Dynamic Fracture Toughness of Nuclear Pressure Vessel Steel A508CL3

采用示被冲击试验及预制疲劳裂纹Charpy试样,通过几种不同的单试样(或多试样)试验方法对核压力容器用A508CL3钢的动态断裂韧性进行了评定,比较了各种方法的优缺点.研究结果表明:最大载荷能量法过高地评定了材料的动态断裂韧性值(特别是在常温以上温度时);而柔度变化率法的评定值则过低,断口延伸带宽度测试法的评定结果具有较大误差,且试验过程复杂,成本较高;能量修正法是一种方便而精确的评定核压力容器钢动态断裂韧性的单试样方法;研究还表明,虽然动态阻力曲线试验法可获得最为精确的动态断裂韧性的临界值,但所需的试样数量较多,用作核压力容器钢的中子辐射脆化动态断裂韧性监测是不合适的.

This investigation has used the five methods to estimate the dynamic fracture toughnes for a nuclear pressure vessel steel A508CL3 by using instrumented impact test and pre-cracke Charpy-size specimen, the merits and the disadvantages of the five methods have also been compared. The experimental results indicated that the maximum load energy method based on the curve of load versus load-point diaplacement overestimates the dynamic fracture toughness, especially beyond the room temperature. However . the method of compliance changing rate underestimates the dynamic fracture toughness. The method of measuring the stretched zone width (SZW) at the crack tip by means of a SEM fractography and then converting SZW into JId have a relatively large error, and it is difficult to measure the SZW and with high rost. The method of energy revised at the maximum load may be considered as a better single specimen method for determining dynamic fracture toughness of a A508CL3 steel. Furthermore, the results indicate that although the dynamic resistance curve method can exactly estimate dynamic fracture toughness of the material, this method needing several specimens and the test procedure is complicated, thus, it is not suitable for nuclear reactor pressure vessel embrittle-ment surveillance due to neutron irradiation.