Effect of Relative Humidity on DEM Contact Parameter Calibration for Lanthanum Oxide Powder

Lanthanum oxide (La2O3) powder is widely used in optical, catalytic, and ceramic applications, but its flowability is highly sensitive to ambient humidity, and reliable discrete element method (DEM) contact parameters under varying moisture conditions remain unavailable. To address this, the present study introduces coarse-graining theory to reduce computational cost while preserving macroscopic mechanical equivalence, and systematically calibrates the DEM contact parameters of La2O3 powder under three controlled humidity levels (5%, 50%, and 95% RH) using the Hertz–Mindlin with JKR contact model. The angle of repose was measured as the macroscopic response. A Plackett–Burman design was employed to screen three significant factors from seven candidate parameters, followed by a steepest ascent test to determine optimal parameter ranges, and a Box–Behnken design to construct response surface models. Quantitative relationships were established between the angle of repose and the particle–particle static friction coefficient, particle–particle rolling friction coefficient, and particle–stainless steel static friction coefficient under each humidity condition. The calibrated parameters were verified against experimental anglef of repose measurements, showing good agreement, with errors of 0.48%, 2.15%, and 1.67% for the three humidity levels, respectively. This work provides reliable DEM parameters specifically for the three tested relative humidity levels (5%, 50%, and 95% RH) under the specific conditioning procedures used, and offers a calibration framework extendable to other moisture-sensitive cohesive powders.