Time-dependent creep behavior of particulate materials

The analysis of creep curves is usually based on the rate process approach originated by Eyring in 1936. The modified Eyring equation predicts that creep rate resulting from the viscous behavior is temperature dependent. All authors have so far assumed that the temperature term in the Eyring equation is time independent. In this paper it is recognized that, during the short period of sudden application of a given load to the material, the inevitable deformation that takes place at the interparticle contact zones will cause a sudden increase in the temperature of these zones. During creep, this excess temperature will dissipate and cause a progressive increase in the viscosity of the contact zones resulting in a decreasing creep rate with time. Based on the foregoing concept a theoretical equation for creep rate dependence on time has been developed. Analysis of the experimental data obtained from the creep test of lime-pulvervized-fuel-ash mixtures shows that the derived equation can only account for the decrease in strain rate during the early stages of creep.