双金属接头界面裂纹几何拘束与断裂韧性的统一关联

UNIFIED CORRELATION OF GEOMETRY CONSTRAINT WITH FRACTURE TOUGHNESS FOR THE INTERFACE CRACK IN BIMETALLIC JOINTS

针对均质材料A508合金钢定义了可表征面内/面外几何拘束的统一拘束参数Ap,但在双金属接头或异种金属焊接接头中,除了存在面内/面外几何拘束外,还存在材料性能失配引起的材料拘束。针对均质材料定义的统一拘束参数Ap能否同时对几何拘束与材料拘束进行表征还需要进一步的研究。采用有限元数值模拟的方法,对不同面内、面外拘束的双金属接头界面裂纹尖端的等效塑性应变等值线所围面积进行了计算;并用嵌含有GTN损伤模型的有限元法计算了不同拘束状态下双金属接头界面裂纹的J-R阻力曲线和延性断裂韧性。之后,分析了Ap作为几何拘束与材料拘束统一表征参数的可行性。结果表明:Ap可作为统一拘束参数对几何拘束和材料拘束同时进行表征,并可用其建立双金属接头中几何拘束与断裂韧性之间的统一关联线。

A unified constraint characterization parameter Aphas been defined based on the homogeneous material A508 in the previous study of authors. However,it is not clear that whether the unified correlation of in-plane and out-of-plane constraint with fracture resistance can be established by using the constraint parameter for the dissimilar metal welded joints（ DMWJs） or the bimetallic joint with highly heterogeneous mechanical property（ material constraint）. In this paper,the J-resistance curves of specimens under different in-plane and out-of-plane constraints for bimetallic joint were obtained by the FEM simulations based on GTN（ Gurson-Tvergaard-Needleman） damage model. And the equivalent plastic strain distributions ahead of crack tips for specimens with different constraint were calculated by the FEM model. After the fracture toughness JICand Apunder different constraint conditions were obtained,the unified correlation of in-plane constraint and out-of-plane constraint with fracture toughness of bimetallic joint was investigated. The results show that the Apis an appropriate unified constraint parameter which can characterize both geometry and material constraint,and can be used to established the unified correlation line between the fracture toughness and geometry constraint in bimetallic joint.