In this paper,a nonlocal theory of fracture for brittle materials has been systematically devel- oped,which is composed of the nonlocal elastic stress fields of Griffith cracks of mode-Ⅰ,Ⅱ and Ⅲ,the asymptotic form...In this paper,a nonlocal theory of fracture for brittle materials has been systematically devel- oped,which is composed of the nonlocal elastic stress fields of Griffith cracks of mode-Ⅰ,Ⅱ and Ⅲ,the asymptotic forms of the stress fields at the neighborhood of the crack tips,and the maximum tensile stress criterion for brittle fracture.As an application of the theory,the fracture criteria of cracks of mode-Ⅰ,Ⅱ, Ⅲ and mixed mode Ⅰ-Ⅱ,Ⅰ-Ⅲ are given in detail and compared with some experimental data and the theoretical results of minimum strain energy density factor.展开更多
Without use of any plastic potential function, an incremental constitutive relation of elastoplastic material is formulated by relating energy-consumlng rate in sliding between micro grain constituents of material and...Without use of any plastic potential function, an incremental constitutive relation of elastoplastic material is formulated by relating energy-consumlng rate in sliding between micro grain constituents of material and in extending-shrinklng of fiber-like ones to overall strain rate and deriving the stress response with a work-conjugate method. Slip systems and fibers deforming compatibly with overall strain are used as equivalent energyconsumers distributed uniformly in the same direction as the replaced micro objects. The equivalent energy-consumers with similar orientation are treated as an elasto-plastic component with only one deformation degree of freedom, so the incremental stiffness tensor is explicit and convenient for numerical analysis. The effect of loading paths on macro mechanical behavior of material under complex loading conditions can be simulated because the combined responses of components with different orientations are sensitive to loading history.We have also investigated how to determine parameters in the force-response functions of the equivalent energy-consumers and coefficients for cross-hardenlng effect and Bauschinger effect on the basis of conventional material tests. Examples are given to show that the predicted macro elasto-plastic behavior and subsequent yield surfaces of materials under various loading conditions are in excellent agreement with experiments.展开更多
文摘In this paper,a nonlocal theory of fracture for brittle materials has been systematically devel- oped,which is composed of the nonlocal elastic stress fields of Griffith cracks of mode-Ⅰ,Ⅱ and Ⅲ,the asymptotic forms of the stress fields at the neighborhood of the crack tips,and the maximum tensile stress criterion for brittle fracture.As an application of the theory,the fracture criteria of cracks of mode-Ⅰ,Ⅱ, Ⅲ and mixed mode Ⅰ-Ⅱ,Ⅰ-Ⅲ are given in detail and compared with some experimental data and the theoretical results of minimum strain energy density factor.
基金Project supported by Laboratory for Nonlinear Mechanics of Continuous Media, Institute of Mechanics, Academia Sinica.
文摘Without use of any plastic potential function, an incremental constitutive relation of elastoplastic material is formulated by relating energy-consumlng rate in sliding between micro grain constituents of material and in extending-shrinklng of fiber-like ones to overall strain rate and deriving the stress response with a work-conjugate method. Slip systems and fibers deforming compatibly with overall strain are used as equivalent energyconsumers distributed uniformly in the same direction as the replaced micro objects. The equivalent energy-consumers with similar orientation are treated as an elasto-plastic component with only one deformation degree of freedom, so the incremental stiffness tensor is explicit and convenient for numerical analysis. The effect of loading paths on macro mechanical behavior of material under complex loading conditions can be simulated because the combined responses of components with different orientations are sensitive to loading history.We have also investigated how to determine parameters in the force-response functions of the equivalent energy-consumers and coefficients for cross-hardenlng effect and Bauschinger effect on the basis of conventional material tests. Examples are given to show that the predicted macro elasto-plastic behavior and subsequent yield surfaces of materials under various loading conditions are in excellent agreement with experiments.
