| 1. |
- Ottosen, Niels Saabye
(författare)
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Behaviour of Viscoelastic-Viscoplastic Spheres and Cylinders-Partly Plastic Vessels walls
- 1985
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 21:6, s. 573-595
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Tidskriftsartikel (refereegranskat)abstract
- The material model consists of a viscoelastic Burgers element and an additional viscoplastic Bingham element when the effective stress exceeds the yield stress. For partly plastic vessel walls, expressions are derived for the stress and strain state in pressurised or relaxation loaded thick-walled cylinders in plane strain and spheres. For the spherical problem, the material compressibility is accounted for. The influence of the different material parameters on the behaviour of the vessels is evaluated. It is shown that the magnitude of the Maxwell viscosity is of major importance for the long-term behaviour of thick-walled partly plastic vessels.
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| 2. |
- Ottosen, Niels Saabye
(författare)
-
Behaviour of viscoelastic-viscoplastic spheres and cylinders—Fully plastic vessel walls
- 1985
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 21:6, s. 561-595
-
Tidskriftsartikel (refereegranskat)abstract
- The material model consists of a viscoelastic Burgers element and an additional viscoplastic Bingham element when the effective stress exceeds the yield stress. For fully plastic vessel walls, exact closed-form expressions arc derived for the stress and strain state in pressurised or relaxation loaded thick-walled cylinders in plane strain and spheres. For the spherical problem, the material compressibility is accounted for. The influence of the different material parameters on the behaviour of the vessels is evaluated. It is shown that the magnitude of the Maxwell viscosity is of major importance for the long-term behaviour of thick-walled fully plastic vessels.
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| 3. |
- Ottosen, Niels Saabye
(författare)
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Theoretical Framework for Modelling the Behaviour of Frictional Materials
- 1986
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 22:11, s. 1325-1342
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Tidskriftsartikel (refereegranskat)abstract
- A constitutive theory is proposed, which possesses the possibilities of modelling all the important features or the behaviour or frictional materials such as: influence of all three stress invariants, coupling between deviatoric and volumetric response, dilatancy, softening, and different behaviour in loading and unloading. The basic constitutive assumptions are relations between properly defined stress and strain rate invariants, from which the component equations are derived by means of a suitable reformulation. After the incremental stress-strain relations have been derived, they are augmented by consistent loading/unloading criteria. Emphasis is given to a fundamental discussion of the general properties of the theory proposed and it is shown to fulfil all the formal requirements (causality, determinism, admissibility, form-invariance, continuity) that a properly formulated constitutive theory must obey. Moreover, the theory contains a surprisingly large number of classical as well as nonclassical theories as special cases. In particular, it contains formulations ranging from nonassociated plasticity theory, associated plasticity theory, hypoelasticity to elasticfracturing theory.
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| 4. |
- Singh, U.K., et al.
(författare)
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Application of a continuum damage model in the finite element simulation of the progressive failure and localization of deformation in brittle rock structures
- 1989
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 25:9, s. 1023-1038
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Tidskriftsartikel (refereegranskat)abstract
- A continuum damage model is generalized to simulate both the progressive failure and the formation of localization bands in brittle rock structures under both tensile and compressive loading. The model is implemented into a finite element code to simulate the constitutive behaviour of a number of brittle rock structures which might actually be found in the laboratory or in the field. The effect of closed cracks is included in the calculations. Since, in the present work, finitely extended bodies are considered, the damage in a given direction can no longer be supposed uniformly distributed throughout the body considered
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| 5. |
- Singh, U.K., et al.
(författare)
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Continuum damage model for simulation of the progressive failure of Brittle Rocks
- 1989
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 25:6, s. 647-663
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Tidskriftsartikel (refereegranskat)abstract
- A constitutive model is developed in which a set of continuous field variables, called damage vectors are used to describe the anisotropic response of a brittle solid due to the growth of cracks under general applied loads. The model is tested numerically by studying the response of infinitely extended solids under a number of general plane strain loading conditions
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| 6. |
- Östlund, Sören, et al.
(författare)
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Asymptotic crack tip fields for dynamic fracture of linear strain-hardening solids
- 1988
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 24:11, s. 1141-1158
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Tidskriftsartikel (refereegranskat)abstract
- Asymptotic crack tip fields, for dynamic crack propagation in an elastic-plastic material, have been calculated. The material is characterized by J2flow theory with linear-strain hardening. The possibility of plastic reloading on the crack flank is taken into account. Numerical results for the strength of the crack tip singularity, the angular positions of elastic unloading and possible plastic reloading regions, and the angular variation of the stress and velocity fields, are presented as functions of the crack tip speed and the ratio between tangent modulus and elastic modulus. Calculations have been performed for crack tip speeds below a certain limit velocity which depends on the tangent modulus and the loading conditions. The different loading modes which have been studied are modes I and II (plane strain and plane stress) and mode III (antiplane strain).
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