Dynamic damage evolution in brittle solids

268A 934481 Thickness equation for nonwoven needle-punched geotextiles under normal loading. Technical note Weggel, J R; Gontar, W A Geoteeh Test J V15, N4, Dec 1992, P404-408 Changes in thickness with increasing normal load have been examined for 8 nonwoven, needle-punched geotextiles in a radial flow permeability measuring device. An equation to predict thickness is developed, which gives excellent results up to about 370kPa. At limiting thickness, the porosity is reduced to approximately 91% of the initial unstressed value. 934482 Properties of eoncretionary laterite gravel concrete Akpokodje, E G; Hudec, P Int Assoe Engng Geol Bull N46, Oct 1992, P45-50 Compressive strength and expansion of concrete made with slightly/moderately indurated concretionary laterite gravels have been examined. The compressive strength is comparable with that of concrete made with the usual crushed granite aggregates of Nigeria. Strength of the laterite concrete is primarily dependent on the cement-aggregate bond,rather than on physical properties of the aggregate. The laterite concrete shows net contraction on immersion in hot lN NaOH, attributable to low contents of silica, clay, and lime. These gravels appear to be cheap and readily available aggregates for tropical countries.

Snow and ice mechanics 934483 Snowpack characteristics associated with avalanche accidents. Note Jamieson, J B; Johnston, C D Can Geoteeh J V29, NS, Oct 1992, P862-866

The case of a brittle cylindrical rod with a periodic array ol identical surface notches and under biaxial stress is examined using a linear elastic fracture mechanics approach. Fracturing pressure increases with increasing thickness of the disks. 934485 Dynamic damage evolution in brittle solids Deng, H; Nemat-Nasser, S Meeh Mater VI4, N2, Dec 1992. P83-103 A two dimensional model is developed to simulate the dynamic damage evolution under uniaxial compression of a brittle solid with an initial population of microflaws. Frictional and rate-dependent and rate-independent plastic constitutive relations are used to describe deformation of the microflaws. Inelastic deformation of the microflaws is assumed to produce tensile microcracks which emanate from the microflaws and grow in the direction of compression. Overall response of the solid is examined numerically. Propagation and attenuation of a stress pulse in a semi-infinite bar is also studied. 934486 Asymptotic fields of mode I steady-state crack propagation in non-associative elastoplastic solids Radi, E; Bigoni, D Meeh Mater V14, N3, Jan 1993, P239-251 The quasi-static, steady-state propagation of a crack running in an elastoplastic solid with volumetric non-associative flow law is analysed. The adopted constitutive model corresponds to the small strain version of that proposed by Rudnicki and Rice. The asymptotic crack-tip fields are numerically obtained for the case of the incremental theory with linear isotropic hardening, under mode I plane-stress conditions. A relevant conclusion of the study is that the singularity of the near-tip fields appears to be mainly governed by the flow-rule, rather than by the yield surface gradient. Auth

Analysis has been made of 93 fatal avalanche accidents in Canada. Most involved dry snow and were triggered by human activity. Slab thickness averaged 0.86m. More than half involved snow which fell before the most recent deposit. Surface hoar and faceted grains were the persistent failure layer microstructures. These avalanches were not predicted, indicating present forecasting techniques are inadequate where surface hoar and faceted grains occur.

Fracture mechanics 934484 Infinite periodic array of cracks in axisymmetric disking Santhanam, S Int J Solids Struet V30, N6, 1993, P739-749 Fracturing by disking has not been extensively studied and no analytical fracture criterion exists to predict the effects of various material and geometric parameters on fracture pressure.

© 1993 Pergamon Press Ltd. Reproduction not permitted