(137d) Interpretation of Shear Cell Results Using Various Yield Locus Curve Fitting Approaches

Bulk powder flowability properties are routinely evaluated in Jenike shear cell testers. The results strongly depend on the Yield Locus that is approximated by fitting a curve (or a line) to the measured shear points. In the present study, an attempt is made to investigate the effects of various Yield Locus curve fitting approaches on the assessed bulk flow properties. To this end, 7 materials with a wide range of cohesive nature are tested at 3 different levels of normal steady-state stresses (providing major principal stresses in the range of 7 – 40 kPa). The curve fitting approaches included in the study are Linear, the Warren-Spring model, Power Law, and an alternative linear method. Amongst these, it was found that Power Law failed to meet the yield criteria for 25% of the tests (out of total 63 tests). All the methods reported similar values of Major Principal Stress. Linear method resulted in the most conservative values for Unconfined Yield Stress, Bulk Cohesion, and Tensile Strength; whereas Warren-Spring model estimated the least conservative values. The coefficients of variation of the reported bulk properties, using various Yield Locus curve fitting approaches, were found to be similar.