Deformation simulation analysis of black fungus stick during piercing and laying process based on discrete element

This study addresses the challenge of observing and simulating the internal movement of fungal material substrate during the piercing and laying processes of black fungal sticks using the Discrete Element Method (DEM). The research begins by calibrating the intrinsic and contact parameters of fungi of different sizes within the cultivation sticks. This calibration ensures that the DEM simulations accurately reflect real-world mechanical behavior. Key parameters such as particle stiffness, friction coefficients, and damping factors are adjusted to replicate the interactions between fungal particles. After calibration, both physical experiments and DEM simulations of the piercing process are conducted. The physical experiments measure key substrate parameters, particularly the repose angle, which influences how the substrate settles. Using these measurements, the DEM simulations are fine-tuned to closely match real-life scenarios. The simulations involve inserting virtual tools into the modeled fungal sticks, allowing for the observation of substrate behavior under controlled conditions. To validate the accuracy of the DEM model, the simulation results are compared with experimental data obtained from a fully automatic piercing machine. The comparison focuses on the depth and diameter of the holes created during the piercing process. The relative errors between the simulation and experimental results are 3.6% for hole depth and 4.5% for hole diameter. These low error margins confirm the model's accuracy in replicating real-world conditions, providing confidence in the DEM model's reliability for future simulations. In addition to the piercing simulations, the study explores the impact of landing shock on the deformation of fruiting holes within the fungal sticks. This aspect of the research simulates the falling process of fungal sticks during the operation of a semi-automatic laying machine. Displacement velocities of substrate particles around the ear holes are measured at three different positions along the fungal stick: the top, middle, and bottom. The recorded velocities are 441 mm/s, 621 mm/s, and 1115 mm/s, respectively. The results indicate that deformation is most significant at the bottom of the stick and decreases towards the top. The diameter and depth of the bottom ear holes are 12.3% and 14.3% smaller, respectively, compared to the top ear holes. Despite this deformation, the study finds that the minimum aperture diameter and depth obtained through simulation 3.2mm and 32.5mm, respectively still meet the requirements for ear production. This indicates that the fungal sticks remain suitable for agricultural use, even after undergoing deformation due to landing shock. The study concludes that the semi-automatic laying machine is effective for practical agricultural production, as it does not cause deformation beyond acceptable limits. In conclusion, this research successfully addresses the challenges of simulating the internal movement of fungal material within black fungal sticks and provides a validated DEM model that accurately replicates the piercing and laying processes. The insights gained from the study, particularly regarding deformation caused by landing shock, contribute to optimizing the design and operation of machinery used in mushroom cultivation. This ensures that the quality and functionality of the fungal sticks are maintained throughout the production process, making the DEM model and methodologies valuable tools for improving agricultural practices in mushroom cultivation.