A CONSTANT VOLUMETRIC-FAILURE-STRAIN EROSION FOR DETERMINING THE EFFECT OF INERTIA AND STRAIN RATE ON THE CRUSHING STRENGTH OF A CELLULAR CONCRETE

Abstract

The effect of inertia and strain rate on the failure of a cellular autoclaved aerated concrete (600 kg m-3 ) was investigated using MAT_096 material model together with a constant volumetric-failure-strain erosion criterion in the LSDYNA. A rate insensitive, constant compressive yield stress, and a rate sensitive, variable compressive yield stress, model were implemented and the results of models were compared with those of experimental compression tests conducted at similar strain rates, between 2x10-3 s -1 and ~4150 s-1 . Results have shown an “s-type” compressive strength relation with strain rate, broadly composing of three distinct regions: a lower-velocity-dependentstrength region at the quasi-static velocities, a higher-velocity-dependent-strength region at intermediate velocities and again a lower-velocity-dependent-strength region above ~1150 s-1 . In experimentally tested samples, a shock fracture strength was presumed to be reached in the higher velocity-dependent strength region, resulting in a cut-off DIF value (2.78), while in numerically tested samples, the compressive strength increased with increasing strain rate in the third region. One dimensional state of strain condition above a critical velocity was also shown numerically. The stress triaxiality increased to 0.66 between 1 and 30 m s-1 , reaching a fully constraint 1D state of strain condition above 30 m s-1 . In accord with this, the numerical failure mode, as with that of experiments, switched from an axial- to a radial-dominated cracking after ~20 m s-1 . Finally, the strain rate dependent compressive strength was numerically shown as partly arising due to the change of deformation state from a 1D state of stress to a 1D state of strain and partly due to the intrinsic rate sensitivity of cellular concrete.