Cyclic Non-linear Constitutive Equations for Sands

A series of triaxial cyclic tests are performed on Hostun sand; each test undergoes several two-way, strain-controlled cyclic loadings under drained conditions. The purpose of these tests is to investigate the behavior of this sand under complex loadings. This paper extends the previous works during the last years, and aims at showing that the non-linear incremental constitutive equations can describe the behavior of saturated sand subjected to various stress loadings in drained conditions

Cyclic Undrained Tests Along Constant Axial Stress on Hollow Cylinder

Cyclic hollow cylinder tests have been performed on sand and clay under undrained conditions. In order to point out the effects of the rotation of principal axes, a constant axial stress is maintained during the application of torsional shear. On this stress path, the behavior of the two materials is studied in terms of stress-strain relationship, pore pressure, failure criterion and also rotation of strain principal axes

Estimation of the light output power and efficiency of a XeCl dielectric barrier discharge exciplex lamp using one dimensional drift-diffusion model for various voltage waveforms

A XeCl dielectric barrier discharge (DBD) excilamp applied by pulsed and sinusoidal voltage waveforms is simulated using a 1-D drift–diffusion model. In both waveforms, the light output power depends not only on the gas mixture composition but also on the electrical parameters of each voltage waveform such as the frequency, the duty cycle, etc. At the same amplitude of the applied voltage and frequency, the light ultraviolet output efficiency of a pulsed voltage is higher than that of a sine voltage. These results obtained in this paper permit us to find out an appropriate power supply for a DBD excilamp

A laboratory study of anisotropic geomaterials incorporating recent micromechanical understanding

This paper presents an experimental investigation revisiting the anisotropic stress–strain–strength behaviour of geomaterials in drained monotonic shear using hollow cylinder apparatus. The test programme has been designed to cover the effect of material anisotropy, preshearing, material density and intermediate principal stress on the behaviour of Leighton Buzzard sand. Experiments have also been performed on glass beads to understand the effect of particle shape. This paper explains phenomenological observations based on recently acquired understanding in micromechanics, with attention focused on strength anisotropy and deformation non-coaxiality, i.e. non-coincidence between the principal stress direction and the principal strain rate direction. The test results demonstrate that the effects of initial anisotropy produced during sample preparation are significant. The stress–strain–strength behaviour of the specimen shows strong dependence on the principal stress direction. Preloading history, material density and particle shape are also found to be influential. In particular, it was found that non-coaxiality is more significant in presheared specimens. The observations on the strength anisotropy and deformation non-coaxiality were explained based on the stress–force–fabric relationship. It was observed that intermediate principal stress parameter b(b = (σ2 − σ3)/(σ1 − σ3)) has a significant effect on the non-coaxiality of sand. The lower the b-value, the higher the degree of non-coaxiality is induced. Visual inspection of shear band formed at the end of HCA testing has also been presented. The inclinations of the shear bands at different loading directions can be predicted well by taking account of the relative direction of the mobilized planes to the bedding plane