As far as the calibration of bulk material for DEM simulations is concerned, it is necessary to adjust the properties of simulated bulk material until the behaviour of this digitally modelled material coincides with the behaviour of physical material tested in laboratory tests. One well-established parameter that is often used for this purpose is the so-called angle of repose, which can be described as the highest possible angle, with respect to the horizontal plane, at which bulk material can be heaped without collapsing. For the determination of this angle, various kinds of tests are applicable, such as the commonly used lifting cylinder test, in which a bottomless cylinder filled with bulk material is lifted off the ground. Digital bulk material calibration regarding the angle of repose is then performed using DEM simulations and adjusting the influencing material parameters correspondingly until the same angle of repose is obtained with the digital and thus calibrated bulk material model.

Since the angle measurement is still mostly done by hand, which harbours the danger of errors, and the calibration process with altering angle measurement and parameter adjustment is rather time-consuming, the development of an algorithm for the evaluation of the angle of repose promises some significant advantages. To name a few: higher reproducibility and accuracy of measurements, by eliminating the factor human; faster calibration due to a well-defined evaluation process, also implementable as algorithms directly in calibration processes; and benefits due to statistically supported, time-efficient analysis of large amounts of data.

This paper gives a step by step explanation of the methods behind the developed algorithm for the determination of the angle of repose, in particular, in order to enable the implementation of these methods as tools in custom software programs. Thus the developed algorithm is useful for applications ranging from simple angle determination to fully automated calibration procedures etc.