| 1. |
- Cannmo, Patrik, et al.
(author)
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Modelling of plasticity and damage in a polycrystalline microstructure
- 1995
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In: International Journal of Plasticity. - 0749-6419 .- 1879-2154. ; 11:8, s. 949-970
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Journal article (peer-reviewed)abstract
- The mesomechanical behavior of a polycrystalline microstructure subjected to monotonic and cyclic loadings is investigated. The analysis is based on a Voronoi polygonization strategy for generation of grains embedded in a contiguous matrix. The main emphasis is to investigate the interaction between the microconstituents and the failure processes along grain boundaries. A rational interface theory based on damage development coupled to inelastic slip and dilatation is developed. The theory uses the interface width as a constitutive parameter, which regularizes the theory of LEMAITRE [1992], that is restricted to perfect bond between grain and matrix. In a series of FE-analyses parameter variations were performed: The unit cell size (as compared to the average grain diameter), the grain-matrix area ratio, the interface width and constitutive parameters. It appears that the composite behavior can be designed as brittle or ductile solely depending on the strength and rate of damage development in the interfaces. A localization band was detected, and its orientation is in the range that is predicted within continuum theory.
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| 2. |
- Ristinmaa, Matti
(author)
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Cyclic plasticity model using one yield surface only
- 1995
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In: International Journal of Plasticity. - : Elsevier BV. - 0749-6419. ; 11:2, s. 163-181
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Journal article (peer-reviewed)abstract
- A time-independent plasticity model using only one yield surface and capable of predicting cyclic loading is presented. Memory points are defined to monitor the loading history; these memory points have the property that they can be created as well as disappear during the load history. The generalized plastic modulus is defined from these memory points in such a way that it will be continuous and provide a smooth transition from elastic to elastic-plastic behavior. The model is formulated for general pressure-insensitive plasticity. Because only one yield surface is used, this framework allows all types of yield functions to be easily implemented. For piecewise linear response, the concept of memory points may be interpreted in terms of the classic Mroz model. Moreover, a generalization of the Mroz model for a smoothly varying response can be made. As an important example of pressure-insensitive plasticity, the von Mises criterion is incorporated into the model to illustrate the response for different load situations. Of particular interest is cyclic hardening, mean stress relaxation, and ratchetting. A simple law for controlling the ratchetting is also introduced.
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