DEM simulation for draft force prediction of moldboard plow according to the tillage depth in cohesive soil

In the field of agricultural machinery, various empirical field tests are performed to measure the design load for optimal design of tractors and implement. However, field test performance is costly, time-consuming, and there are many constraints on weather and field soil conditions, requiring simulation utilization studies to overcome these shortcomings. Therefore, the objectives of this study are to perform agricultural soil modeling, draft force prediction simulation in function of tillage depth using discrete element method (DEM) software, and to verify the prediction accuracy by comparing with field test results. In this study, soil property measurement test was performed by soil depth considering target tillage depth (0-200 mm) using soil mechanical properties measurement system for DEM soil modeling. DEM soil model calibration was performed using virtual vane shear test and cone penetration test values instead of the repose angle test. In addition, field tests to verify the accuracy of draft force prediction simulation were performed using a measuring tractor equipped with a draft force measurement system, a tillage depth measurement system and an RTK-GPS (travel speed). As a result of the DEM simulation, it was found that the prediction accuracy of the draft force was within 7.5% (5.1-9.9%) when compared to the measured draft force through field test. In addition, it was confirmed that the result was 5.3-61.6% more accurate than those obtained through existing theoretical methods used to predict draft force. On the other hand, the error of draft force prediction using DEM simulation considering only topsoil properties showed 20.3% lower prediction accuracy than the DEM soil model considering the soil properties of different soil layer. This study provides useful information for the DEM soil modeling process that consider the change in soil properties according to the tillage depth from the perspective of agricultural machinery research and it is expected to be utilized in agricultural machinery design research.