不锈钢晶间腐蚀弯曲评价方法的影响因素

Influencing Factors of Bending Assessment Method for Intergranular Corrosion of Stainless Steels

用嵌含有GTN延性损伤模型的ABAQUS有限元法,模拟研究了不锈钢晶间腐蚀弯曲评价方法中材料力学性能、弯曲角度和压头直径对弯曲试样塑性应变分布、延性损伤和裂纹起裂的影响规律,分析了其对晶间腐蚀弯曲评价结果的影响。结果表明:随着试样弯曲角度的增大和弯曲压头直径的减小,试样拉伸面的塑性应变增加,试样越容易产生弯曲开裂;在晶间腐蚀弯曲评价标准中,当固定弯曲角度和压头直径时,对于塑性、韧性和抗断裂综合力学性能较低的不锈钢材料,在弯曲过程中材料本身会发生开裂;因此,需要考虑材料力学性能对晶间腐蚀弯曲评价结果的影响;对于该研究中的典型的奥氏体不锈钢材料,当其弯曲断裂应变低于0.51左右时,在弯曲过程中材料本身会发生开裂,不宜用弯曲方法来评价其晶间腐蚀敏感性。

The finite element method （FEM） based on GTN damage model was used to investigate the effects of mechanical properties of materials, bending angle and pressure head diameter on plastic strain distribution, ductile damage and crack initiation of bending specimens for assessing intergranular corrosion of stainless steels. The results show that the tensile plastic strain in the specimens increases with the increasing of bending angle and decreasing of pressure head diameter, and the specimens become easier to crack. For the fixed bending angle and pressure head diameter in the assessment standard for intergranular corrosion, cracks may initiate during bending for some stainless steels with lower plasticity, toughness and fracture resistance. So the effects of the mechanical properties of materials on the bending assessment results for intergranular corrosion should be considered. For the typical austenitic stainless steel in this study, when its bending fracture strain is less than about 0. 51, cracks may occur during bending test. In this case, the bending method may not be suitable for assessing the intergranular corrosion of stainless steels.