Crack growth rate curves are the fundamental material property for metal structures under fatigue loading. Although there are many crack growth rate curves available in the literature, few of them showed the capabilit...Crack growth rate curves are the fundamental material property for metal structures under fatigue loading. Although there are many crack growth rate curves available in the literature, few of them showed the capability to explain various special phenomena observed in tests. A modified constitutive relation recently proposed by McEvily and his co-workers showed very promising capability. This modified constitutive relation is further generalized by (1) introducing an unstable fracture condition; (2) defining a virtual strength to replace the yield stress; and (3) defining an overload and underload parameter. The performances of this general constitutive relation for fatigue crack growth is extensively studied and it is found that this general constitutive relation is able to explain various phenomena observed with particular strong capability on load sequence effect.展开更多
In the study of plastic constitutive relations, due to the "single curve" hypothesis andthe yield conditions of the phenomenological theory, some theoretic problems about the proc-ess of plastic deformation ...In the study of plastic constitutive relations, due to the "single curve" hypothesis andthe yield conditions of the phenomenological theory, some theoretic problems about the proc-ess of plastic deformation have not yet been solved, and moreover, the constitutive relationsobtained with this method can only be approximately applied to some materials of excellentplastic performances. Plastic deformation in σ<sub>m</sub>, τ<sub>p</sub>, S<sub>2</sub> spaces has been analyzed according tothe "similar curve" hypothesis and the rational yield condition obtained in σ<sub>m</sub>, τ<sub>p</sub>, S<sub>2</sub> spaces,a constitutive relationship of deformation theory of plasticity has been set up, which des-cribes better the laws of plastic deformation and voluminal deformation of all engineeringmaterials subjected to various stresses. By the characteristics of σ<sub>m</sub>, τ<sub>p</sub>, and S<sub>2</sub> and the inde-pendent deformations caused by them respectively, the problem about deviation from simpleloading has been solved, the cause of the loss of stability of materials under tension hasbeen theoretically given, some difficuties in the basic theory of plasticity have been over-come, and thus the basis has been laid down for a new theory system of plasticity.展开更多
文摘Crack growth rate curves are the fundamental material property for metal structures under fatigue loading. Although there are many crack growth rate curves available in the literature, few of them showed the capability to explain various special phenomena observed in tests. A modified constitutive relation recently proposed by McEvily and his co-workers showed very promising capability. This modified constitutive relation is further generalized by (1) introducing an unstable fracture condition; (2) defining a virtual strength to replace the yield stress; and (3) defining an overload and underload parameter. The performances of this general constitutive relation for fatigue crack growth is extensively studied and it is found that this general constitutive relation is able to explain various phenomena observed with particular strong capability on load sequence effect.
文摘In the study of plastic constitutive relations, due to the "single curve" hypothesis andthe yield conditions of the phenomenological theory, some theoretic problems about the proc-ess of plastic deformation have not yet been solved, and moreover, the constitutive relationsobtained with this method can only be approximately applied to some materials of excellentplastic performances. Plastic deformation in σ<sub>m</sub>, τ<sub>p</sub>, S<sub>2</sub> spaces has been analyzed according tothe "similar curve" hypothesis and the rational yield condition obtained in σ<sub>m</sub>, τ<sub>p</sub>, S<sub>2</sub> spaces,a constitutive relationship of deformation theory of plasticity has been set up, which des-cribes better the laws of plastic deformation and voluminal deformation of all engineeringmaterials subjected to various stresses. By the characteristics of σ<sub>m</sub>, τ<sub>p</sub>, and S<sub>2</sub> and the inde-pendent deformations caused by them respectively, the problem about deviation from simpleloading has been solved, the cause of the loss of stability of materials under tension hasbeen theoretically given, some difficuties in the basic theory of plasticity have been over-come, and thus the basis has been laid down for a new theory system of plasticity.
