Non-linear Stress (non-linear + stress)

Distribution by Scientific Domains

Selected Abstracts

Numerical studies of shear banding in interface shear tests using a new strain calculation method,

Jianfeng Wang
Abstract Strain localization is closely associated with the stress,strain behaviour of an interphase system subject to quasi-static direct interface shear, especially after peak stress state is reached. This behaviour is important because it is closely related to deformations experienced by geotechnical composite structures. This paper presents a study using two-dimensional discrete element method (DEM) simulations on the strain localization of an idealized interphase system composed of densely packed spherical particles in contact with rough manufactured surfaces. The manufactured surface is made up of regular or irregular triangular asperities with varying slopes. A new simple method of strain calculation is used in this study to generate strain field inside a simulated direct interface shear box. This method accounts for particle rotation and captures strain localization features at high resolution. Results show that strain localization begins with the onset of non-linear stress,strain behaviour. A distinct but discontinuous shear band emerges above the rough surface just before the peak stress state, which becomes more expansive and coherent with post-peak strain softening. It is found that the shear bands developed by surfaces with smaller roughness are much thinner than those developed by surfaces with greater roughness. The maximum thickness of the intense shear zone is observed to be about 8,10 median particle diameters. The shear band orientations, which are mainly dominated by the rough boundary surface, are parallel with the zero extension direction, which are horizontally oriented. Published in 2007 by John Wiley & Sons, Ltd. [source]

Three-dimensional analysis of single pile response to lateral soil movements

J. L. Pan
Abstract Three-dimensional finite element analysis was carried out to investigate the behaviour of single piles subjected to lateral soil movements and to determine the ultimate soil pressures acting along the pile shaft. The finite element analysis program ABAQUS was used for the analysis and run on a SUN Workstation. The von Mises constitutive model was employed to model the non-linear stress,strain soil behaviour. The pile was assumed to have linear elastic behaviour. This was considered to be a reasonable approximation, as the maximum stress developed in the pile did not exceed the yield stress of the concrete pile. The length of the pile is 15 m, the width of the square pile is 1 m. The three-dimensional finite element mesh used in the analysis was optimized taking into account the computing capacity limitations of the Sun Workstation. The computed ultimate soil pressures agreed well with those from the literature. The shapes of the soil pressure versus soil movement curves and the soil pressure versus the relative soil,pile displacement curves as well as the magnitude of the relative soil,pile displacement to mobilize the ultimate soil pressures were in reasonable agreement with those reported by other researchers. Copyright 2002 John Wiley & Sons, Ltd. [source]

Accurate eight-node hexahedral element

Magnus Fredriksson
Abstract Based on the assumed strain method, an eight-node hexahedral element is proposed. Consistent choice of the fundamental element stiffness guarantees convergence and fulfillment of the patch test a priori. In conjunction with a ,-projection operator, the higher order strain field becomes orthogonal to rigid body and linear displacement fields. The higher order strain field in question is carefully selected to preserve correct rank for the element stiffness matrix, also for distorted elements. Volumetric locking is also removed effectively. By considerations of the bending energy, improved accuracy is obtained even for coarse element meshes. The choice of local co-ordinate system aligned with the principal axes of inertia makes it possible to improve the performance even for distorted elements. The strain-driven format obtained is well suited for materials with non-linear stress,strain relations. Several numerical examples are presented where the excellent performance of the proposed eight-node hexahedral is verified. Copyright 2007 John Wiley & Sons, Ltd. [source]

Finite element analysis and evaluation of design limits for structural materials in a cyclic state of creep

M. Boulbibane
Abstract In this paper a direct non-time stepping method derived from the minimum theorems given by the authors (European Journal of Mechanics , A/Solids 2002; 21:915,925) is outlined. This method can be used in the prediction of the deformation and life assessment of structures subjected to cyclic mechanical and thermal loadings. It produces accurate predictions of failure modes based on material behaviour incorporated into constitutive equations. It also can be used to define limit loads related to certain design criteria. Generally, for complex geometries and load histories, the identification of load histories that correspond to predefined design conditions, in the form of time or number of cycles to failure, can only be achieved by extensive and repeated calculations. For the Linear Matching Method, however, the representation of materially non-linear stress and strain fields by linear behaviour with spatially varying moduli, indicates the possibility that direct evaluation of loads and temperature ranges that correspond to a design restriction may be evaluated directly through the construction of the exact cyclic state and via sequence of approximations. The technique employs the finite element method combined with the cyclic state solution. The description of the material behaviour is given by a non-linear viscous model (Norton's law). It can also apply to any class of material behaviour that includes internal state variables. This technique has been applied successfully to a set of characteristics problems (Bree problem and plate containing a circular hole and subjected to radial temperature gradient). Copyright 2003 John Wiley & Sons, Ltd. [source]