Mechanics of Cohesive-frictional Materials最新文献

The tensile mechanical behaviour of quasi-brittle materials, such as concrete, has been the subject of numerous studies from which there has unequivocally emerged the centrality of the cracking phenomenon. The present study highlights this aspect by evaluating the tensile structural response of an infinite plate with an infinite set of collinear cracks that are spaced at a constant distance apart and are of variable length according to a distribution of self-similarity. The first part of this paper describes the general features of the method of the pseudo-tractions used to determine the stress-intensity factors, which is based on the application of the principle of superposition. Subsequently, by means of a numerical simulation, in which account is taken of crack propagation and coalescence (excluding overlapping), the link is obtained between critical tensile stress and the incremental displacement due to the damage present in the material, accounting for typical aspects of structural response, such as the strain-softening phenomenon. Copyright © 2000 John Wiley & Sons, Ltd.

This paper examines the problem of crack extension during the indentation of a brittle elastic half-space by a cylindrical punch with a smooth flat contact surface. The paper develops a procedure for locating the point of nucleation of the crack within the brittle elastic solid and employs a boundary element technique to locate the progress of crack evolution as the force on the punch is increased. The numerical results illustrate the influence of the extent of crack development on the load–displacement relationship for the indentor. Copyright © 2000 John Wiley & Sons, Ltd.

The numerical method of Contact Dynamics is used in order to simulate the Ring Simple Shear Experiment of a granular medium model (Schneebeli material). The numerical results on the discrete medium are then post-processed in order to construct the displacement fields of an equivalent continuum, and the formation of a shear interface layer is observed. The existence and magnitude of individual grain rotations imply that the equivalent continuum could be a Cosserat continuum in this case, at least for the material inside the interface layer. Porosity profiles are presented, showing the progressive loosening of the granular medium, while its dilation is also measured. Copyright © 2000 John Wiley & Sons, Ltd.

The elasto-plastic constitutive model for unsaturated soils postulates the existence of a loading collapse yield locus (LC) and a suction increase yield locus (SI) in the p:s stress plane. The characteristics of the LC yield locus have been reasonably well established in recent years but there is a much greater degree of uncertainty in relation to the SI yield locus. In the work reported in this paper a number of stress path tests in the p:s plane were conducted on samples of unsaturated compacted kaolin in a modified triaxial apparatus. Two series of tests were conducted on samples compacted to an identical initial condition so as to ensure a uniform soil structure prior to testing. Samples tested in Series 1 were taken through three stages: wetting at constant mean net stress, drying at constant mean net stress and a combination of isotropic compression and wetting. Samples tested in Series 2 were taken to pre-selected values of suction prior to isotropic compression. Data obtained from these tests indicate a possible form of single yield locus for unsaturated compacted soil. The data also indicate that the position of the yield locus, initially imposed by the compaction process will be influenced by the subsequent wetting process. Copyright © 2000 John Wiley & Sons, Ltd.

The paper discusses the performance of two different strategies for the integration of hypoplastic constitutive equations, recently proposed to model the incrementally non-linear behaviour of granular soils. An extensive program of numerical tests on some particular strain paths has been conducted in order to evaluate the different algorithms in terms of both accuracy and efficiency. The paper focuses on the effects of such variables as strain increment size and assumed error tolerance, as well as strain increment direction and initial stress state. Copyright © 2000 John Wiley & Sons, Ltd.