High-temperature fatigue properties were investigated for a nickel-based superalloy 617 as a typical candidate material for high-temperature components using an advanced ultra super critical （A-USC） power plant. Cre...High-temperature fatigue properties were investigated for a nickel-based superalloy 617 as a typical candidate material for high-temperature components using an advanced ultra super critical （A-USC） power plant. Creep-fatigue data obtained by strain-controlled tests at 700 ？ C was analyzed for the superalloy 617 focused on position of hold at peak strain in comparison with continuously cycled tests. The fatigue life was the shortest with the hold tensile strain wave, which showed mainly intergranular fracture appearance. The life was the longest with symmetrical triangular wave which fractured from the specimen surface, while the wave with the hold compressive strain showed partially intergranular fracture appearance and the life was middle in the both waves. In this study, it is discussed with the creep-fatigue interaction for the superalloy 617.展开更多
A design strategy for a mechanical metamaterial with large negative hygroscopic expansion(NHE)was proposed in this paper.Different from the reported structures,the present metamaterial is designed by constructing repe...A design strategy for a mechanical metamaterial with large negative hygroscopic expansion(NHE)was proposed in this paper.Different from the reported structures,the present metamaterial is designed by constructing repeated lattice microstructure consisting of curved ligaments incorporating hydrogel active layers and polymer support layers and straight polymer bars.When immersed in the solution environment,the swelling of hydrogel layer of such composite structure induces the reversed bending of the ligament,leading to the overall ultra-large shrink(negative expansion)deformation of the metamaterial.Through the new structural design,large NHE effects can be achieved.The theoretical investigation and finite element analysis(FEA)were conducted to demonstrate the large negative expansion effects of such metamaterial.The results showed that the effective NHE ratio of the metamaterial is dependent of the curvature of the curved ligament and the size of both the ligament and the connecting rod.The ultra-large NHE ratios about−80%for the 2D structure and−90%for the 3D version can be obtained by adopting the structural parameters.The newly designed metamaterials have potential applications in medical and other fields.展开更多
文摘High-temperature fatigue properties were investigated for a nickel-based superalloy 617 as a typical candidate material for high-temperature components using an advanced ultra super critical （A-USC） power plant. Creep-fatigue data obtained by strain-controlled tests at 700 ？ C was analyzed for the superalloy 617 focused on position of hold at peak strain in comparison with continuously cycled tests. The fatigue life was the shortest with the hold tensile strain wave, which showed mainly intergranular fracture appearance. The life was the longest with symmetrical triangular wave which fractured from the specimen surface, while the wave with the hold compressive strain showed partially intergranular fracture appearance and the life was middle in the both waves. In this study, it is discussed with the creep-fatigue interaction for the superalloy 617.
基金supported by the National Natural Science Foundation of China[12172117]Science Foundation for Returned Scholars of Hebei Province of China[C20190318]。
文摘A design strategy for a mechanical metamaterial with large negative hygroscopic expansion(NHE)was proposed in this paper.Different from the reported structures,the present metamaterial is designed by constructing repeated lattice microstructure consisting of curved ligaments incorporating hydrogel active layers and polymer support layers and straight polymer bars.When immersed in the solution environment,the swelling of hydrogel layer of such composite structure induces the reversed bending of the ligament,leading to the overall ultra-large shrink(negative expansion)deformation of the metamaterial.Through the new structural design,large NHE effects can be achieved.The theoretical investigation and finite element analysis(FEA)were conducted to demonstrate the large negative expansion effects of such metamaterial.The results showed that the effective NHE ratio of the metamaterial is dependent of the curvature of the curved ligament and the size of both the ligament and the connecting rod.The ultra-large NHE ratios about−80%for the 2D structure and−90%for the 3D version can be obtained by adopting the structural parameters.The newly designed metamaterials have potential applications in medical and other fields.
