BMe Research Grant
During the measurements and observations several physical, morphological traits, and mechanical behaviour were analyzed and defined that was not measured earlier. The main findings are as follows [K1, K2].
● the equivalent diameter of the internodal parts of maize stalk shows a bi-linear decrease from the bottom to the top of the plant, where the inflection point is the 6th internode, the position of the maize ear;
● the wet mass of the first five internodes gives ~85% of the total wet mass of the stalk, thus, these parts provide the main part of the biomass;
● the axisymmetric shape of an ideal maize ear was determined by using image processing methods;
● the required compressive, bending and cutting work were determined for each internodal section, moreover, the characteristics of these parameters show a decreasing tendency from the bottom to the top of the maize stalk, so that the first five internodes provide the 80% of the total required compressive, bending or cutting work of a common stalk;
● typical breakage of internodal parts were determined through transversal compression, bending and cutting;
● the required ear-detachment force was determined;
● the coefficient of restitution of maize ears was determined on different surfaces.
To determine the model parameters that have a significant effect on the mechanical behaviour of the model in case of different loading cases an extensive parametric study was carried out on the 4th internodal section. The main findings are summarized in Figure 6. [K3, K4, K5, K6]
Figure 6: Relationship between the model parameters and loading cases:
Eb: bond stiffness; ST: bond tensile strength; ζT: coefficient of variation, tensile; SS: bond shear strength; ζS: coefficient of variation, shear;
To numerically predict the mechanical behaviour of the real internodal section during different loading cases, a parameter set was determined by using the calibration and verification method and the results of the parametric study.
Figure 7 presents the experimental and numerical results of sectional transversal compression. The force response of the DEM model is in good agreement with the experimental results. Moreover, the breakage of the virtual sample is similar to the observations during the experiments. [K4, K5, K6]
Figure 7: Experimental and numerical results of sectional transversal compression [K6]
Figure 8 presents the experimental and numerical results of three-point bending experiment. The force response of the DEM model is in a good agreement with the experimental results but for the last section. This can be attributed to the elastic mechanical behaviour of the applied bonded model. Moreover, the breakage of the virtual sample looks similar to the observations during the experiments. [K4, K5, K6]
Figure 8: Experimental and numerical results of three-point bending [K6]
Figure 9 presents the experimental and numerical results of the dynamic cutting experiment. During the virtual cutting process, the same stages of cut can be found: initial compression, cutting and sliding as in the case of the real process. Moreover, the virtual cutting surface is really similar to the experimentally observed ones. [K4, K5, K6]
Figure 9: Experimental and numerical results of dynamic cutting [K6]
[K1] Kovács, Á., Jóri, I.J., Gaál, K., Piros, A., Kerényi, G., 2015. Development of measurement methods for a numerical simulation of corn plants. Mechanical Engineering Letters, Szent István University, 13, 88-96.
[K2] Kovács, Á., Jóri I.J., Kerényi G., Gaál K., 2015. Mérési módszerek kifejlesztése kukorica növény numerikus szimulációjához. Mezőgazdasági Technika, LVI. évf. (12) 2-5.
[K3] Kovács, Á., Kerényi, G., 2016. Comparative analysis of different geometrical structures of discrete element method (DEM) for fibrous agricultural materials. 4th CIGR International Conference of Agricultural Engineering (CIGR-AgEng2016). Aarhus, Denmark.
[K4] Kovács, Á., Kotrocz, K., Kerényi, G., 2015. The adaptability of discrete element method (DEM) in agricultural machine design. Hungarian Agricultural Engineering, 27, 14-19. https://doi.org/10.17676/HAE.2015.27.14
[K5] Kovács, Á., Kerényi, G., 2016. Stochastic variation in discrete element method (DEM) for agricultural simulations. Hungarian Agricultural Engineering, 30, 31-38. https://doi.org/10.17676/HAE.2016.30.31
[K6] Kovács, Á., Kerényi, G., 2018. A new method to calibrate discrete element models of fibrous agricultural materials. European Agricultural Engineering Conference (AgEng 2018). Wageningen, the Netherlands, July 8-12, 2018.
[K7] Kovács, Á., Rádics, P. J., Kerényi, G., 2017. A discrete element model for agricultural decision support. 31st European Conference on Modelling and Simulation (ECMS 2017). Budapest, Hungary, May 23-May 26, 2017.
[K8] Kovács, Á., Kerényi, G., 2017. Modeling of corn ears by discrete element method (DEM). 31st European Conference on Modelling and Simulation (ECMS 2017). Budapest, Hungary, May 23-May 26, 2017.
[K9] Kovács, Á., Zwierczyk, P.T., 2018. Coupled DEM-FEM simulation on maize harvesting. 32nd European Conference on Modelling and Simulation (ECMS 2018). Wilhelmshaven, Germany, May 22-May 25, 2018.
[K10] Kovács, Á., Zwierczyk, P.T., Kerényi, G., 2017. Kapcsolt véges és diszkrét elemes szimulációk (FEA-DEM) alkalmazása a mezőgazdasági géptervezésben. XXV. Nemzetközi Gépészeti Találkozó, ISSN 2068-1267. Kolozsvár, Romania, 2017.
[L1] Wheat harvesting in the mediaeval age
[L2] Wheat harvesting today
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