The Measurement of the Local Slip in Bamboo-Reinforced Concrete Beams Using Moment-Curvature and Bond-Stress

This paper presents a method of measuring local slip in bamboo-reinforced concrete beams.Local slips(so)are calculated by reducing the elongation of the bamboo reinforcement(ebo)with the elongation of the concrete(eco).The elongation of bamboo reinforcement(ebo)is determined in two ways,namely,read directly through a straingauge mounted on the bamboo reinforcement and calculated based on the force analysis or curvature moment as a control.The elongation of the concrete(eco)is calculated using force analysis or curvature moment.The process of calculating curvature moments and bond stress employs the Excel program.The steps in calculating the elongation of concrete(eco)consist of calculating the curvature moment,calculating the bond-stress at the initial crack,and calculating the bond-stress at the second crack until the beam collapses.Further,the results of the calculation of the elongation of the concrete(eco)and the elongation of the bamboo reinforcement(ebo)resulting from the reading of the strain-gauge are substituted in the local slip calculation equation.The results of the calculation analysis show that the local slip is approaching the local slip resulting from the experiment.The relationship behavior of bond-stress vs.slip indicates conformity with the experimental results.The local slip calculation based on the moment-curvature can be considered as control of the experiment result.

A quantitative microplasticity-based approach to rationalize the poor strengthening response of polycrystalline Mg alloys

This work aims to understand the inefficiency of nanoprecipitates to strengthen a weakly textured,polycrystalline Mg-Gd-Y-Zr alloy.An experimental micromechanical approach consisting on micropillar compression combined with analytical electron microscopy is put in place to analyze the effect of nanoprecipitation on soft and hard basal slip and twinning in individual grains with different orientations.This study shows that,in grains that are favorably oriented for basal slip(“soft”basal slip),aging leads to extreme localization due to the ability of basal dislocations to shear the nanoparticles,resulting overall in the softening of basal systems.Additionally,in grains in which the c-axis is almost perpendicular to the compression axis,prismatic slip dominates deformation in the solid solution state and nanoprecipitation favors twinning due to the concomitant lattice solute depletion.Finally,in grains oriented with their c-axis making an angle of about 5-7°with respect to the compression axis,which deform mainly by“hard”basal slip,precipitation leads to the strengthening of basal systems in the absence of obvious localization.This work reveals that the poor hardening response of the polycrystalline alloy is related to the capability of basal dislocations to shear the nanoparticles,in the absence of Orowan looping events,and to the associated basal slip localization.

On the low cycle fatigue behaviour of an Al-Zn-Mg-Cu alloy processed via non-isothermal ageing

The low cycle fatigue behaviour of an Al-Zn-Mg-Cu alloy processed via non-isothermal ageing(NIA)was examined at different strain amplitudes.We showed that NIA improved the low cycle fatigue life(more than 7000 cycles)by optimising the precipitate configuration within 5.5 h while maintaining comparable mechanical properties(570 MPa for tensile strength)and conductivity(nearly 39%IACS)to conventional isothermal ageing,simultaneously.Experimental observation combined with molecular dynamic simula-tion revealed that precipitation configuration manipulated by NIA had a crucial effect on fatigue resis-tance.A great number of repeatedly sheared and locally destructed GP zones enhanced co-planar slip and slip localisation in the under-aged alloy during the early stage of NIA,responsible for the dramatic displacement steps on the surface and resultant poor fatigue performance.As the NIA further proceeded,moderately coarsened precipitates with an average dimension of 6.0 nm and elevated number density ef-fectively impeded the dislocation movement and weaken the slip localisation to a great extent,improving the fatigue performance within a few hours.

LOCAL SLIP VELOCITY IN A DOWNER

Based on the EMMS model, the local slip velocity between gas and solid is systematically analyzed and a theoretical correlation of local slip velocity with local voidage for a downer is derived as follows:U_s(r)/U_t=D^(8/7)(1-ε_mt)^(-2/7)[(1-ε(r)/(ε(r))]^(8/7)]ε(r)(47/14)((ε(r)-ε_(mt))/ε(r)) Using this correlation, the local gas-solid slip velocity in a downer is calculated. The calculated results are well consistent with experimental data. In addition, the variation of the local slip velocity with its corresponding solid holdup is also dis-cussed.