Camellia oleifera is one of the most important cash crops worldwide. Shelling equipment has been widely used to harvest fresh Camellia oleifera. An accurate discrete element model is often required to characterize the multi-layer mechanical response of the fruit interior during shelling. However, single-layer discrete element models cannot capture the mechanical differences between the shell and the seed, due to treating the fruit as a homogeneous entity. Double-layer models can be expected to distinguish between the outer shell and the internal seed body. Since the seed is treated as a uniform structure, the conventional model cannot capture the sequential failure sequence—from outer shell fracture to seed coat rupture and subsequent kernel response—that occurs under compression. In this study, a multi-layer flexible bonding model was established using the discrete element method and the Hertz-Mindlin with Bonding contact model. Camellia oleifera shared a three-layer composite structure, including the outer shell, the seed coat, and the seed kernel. A bonding mechanism for each layer was employed to characterize material fracture behavior using bond breakage between constituent particles. The basic Hertz-Mindlin contact model was applied between adjacent layers to simulate contact compression and extrusion interaction. Heterogeneous modeling provided a physically realistic representation of intra-layer fracture and inter-layer separation, compared with conventional double-layer models. Meanwhile, geometric parameters—including transverse diameter, longitudinal diameter, and shell thickness—and physical properties —including density, Poisson's ratio, and shear modulus—of fresh Camellia oleifera were determined after systematic physical experiments. Contact characteristic parameters, including coefficients of restitution, static friction, and rolling friction for various material pairings, were calibrated to combine experimental measurements with EDEM simulation. The bonding parameters were calibrated for the seed coat–seed coat, kernel–kernel, and shell–shell contacts. A multi-stage experimental protocol included Plackett Burman screening, steepest ascent climbing, and response surface optimization. In the tea seed model, the relative errors between simulated and experimentally measured peak cracking forces in the transverse and longitudinal directions were 3.17% and 7.13%, respectively. In the whole fruit model, the relative errors were 1.54% and 1.83%, respectively, indicating that the calibrated model accurately predicted the critical failure loads. The measured and simulated compression load displacement curves were compared to evaluate model fidelity beyond single-point peak force in the entire loading history. The coefficient of determination (R²) was employed to quantify the overall agreement between the two curves at the elastic deformation, crack initiation, and crack propagation stages. In the whole fruit, the R² values were 0.92 and 0.90, respectively, for transverse and longitudinal compression; In the tea seeds, the R² values were 0.89 and 0.87, respectively. The high R² values confirmed that the simulation matched the peak failure loads to reproduce the full force deformation response with excellent fidelity. Furthermore, macro cracks in the shells consistently appeared along the longitudinal valve lines in both physical experiments and simulations, indicating the correct failure morphology. The progressive cracking behavior was characterized from the fruit shell and the layer by layer mechanical response within the tea seeds—from seed coat rupture to kernel deformation. The findings can provide a robust theoretical basis and support for the simulation driven optimization of Shelling equipment for Camellia oleifera.

Efficient cleaning equipment is often needed in the post-harvesting of Camellia oleifera fruits. Existing devices are limited to suboptimal separation and structural complexity. In this study, a drum-felt cleaning machine was developed to integrate an upper and lower drum mechanism, felt rings, and a throwing plate in a coordinated manner. Effective separation of shell and seed mixtures was then achieved in the machine. The cleaning performance of the machine was systematically evaluated via single-factor and multi-factor orthogonal experiments. Two response indicators were improved, including the seed content in the shell and the shell content in the seed. Four independent variables were investigated, including rotational speed of the drum, feeding angle, moisture content of the shell material, and cumulative cleaning quantity. A single-factor experiment revealed that the increasing drum speed reduced the shell rate within seeds, but there was an increase in the seed rate within shells. The shell content in the seed initially decreased and then increased as the feeding angle increased. While the seed content in the shell rose consistently. A decreasing moisture content of the shell material caused a sharp decline in the shell content in the seed, while the seed content increased in the shell. The individual parameters on separation were used to select the factor ranges for later optimization. A multi-factor orthogonal experiment was designed for the best combination of parameters. The cleaning performance was most significantly dominated by the interaction among drum speed, feeding angle, and moisture content. The best combination of parameters was found as a drum speed of 15.00 r/min, a feeding angle of 3.5°, and a shell moisture content of 27.00%. The better performance of the machine was achieved with a shell content in the seed of 3.51% and a seed content in the shell of 3.49%. These experimental values closely matched the simulated best values from the multi-factor optimization model, thereby confirming the reliability and accuracy of the experimental design and the optimization. The structural design of the cleaning machine proved to be effective. Dual drums and felt bonding were used to manage Camellia oleifera fruit shell-seed mixtures. Dual-drum configuration enhanced the material interaction surface and separation efficiency, while the felt elements contributed to gentle handling and reduced mechanical damage to the seeds. The throwing plate also helped material flow and distribution, showing consistent feeding and uniform processing. Moisture content is also highlighted during separation. Excessive moisture tended to cause agglomeration and adhesion, thus impairing separation efficiency, whereas overly dry material increased dust and fine particles. The feeding angle was found to influence the residence time and movement trajectory of the material within the cleaning zone, thereby affecting separation accuracy. Drum speed directly impacted the centrifugal force and agitation intensity, particularly for dislodging shells from seeds. The high stability of cumulative cleaning quantity was obtained under continuous operation, particularly for practical application in commercial settings. Overall, the drum-felt cleaning machine improved the efficiency and quality of camellia oleifera fruit processing. The simple and robust structure with the best parameters can offer a practical and effective solution to the current challenges in shell–seed separation. The findings can contribute to the camellia oleifera fruit processing. A valuable reference can also offer to optimize similar cleaning equipment for other agricultural products. Long-term performance evaluations can be conducted to explore control systems for real-time parameter adjustment under varying material conditions. Sensors and feedback mechanisms can be integrated to enhance separation consistency with less operator dependency, thus scaling up fully intelligent cleaning in the Camellia oleifera fruit industry.

Monopterus albus (rice field eel) is one of the commercially important fish species in Asian areas. It is often required to efficiently and accurately grade the different body sizes in aquaculture production and standardized processing. In this study, a roller-type machine was proposed for the rice field eel grading. A vibration mechanism and a spraying device were integrated to fully meet the demand for the high-throughput and high-precision size classification. The numerical simulation and experimental validation were conducted to evaluate the grading performance of the equipment. A coupled dynamic model of the grading machine was then established to optimize the operating parameters using RecurDyn–EDEM co-simulation technology. Specifically, the rigid–flexible multibody dynamics of the grading system was modeled in RecurDyn platform, including the vibration exciter, grading sieve, and supporting structure. While the discrete element method was implemented to characterize the motion, collision behavior, and contact interactions of individual rice field eels in EDEM software. The optimal contact models and mechanical parameters were defined to represent the eel–eel and eel–machine interactions. Spraying-assisted lubrication was evaluated to improve material dispersion and then reduce excessive friction during grading. The performance of classification was quantitatively assessed to select grading efficiency and accuracy as the primary indices. A single-factor experiment was conducted to clarify the independent effects of vibration frequency, sieve inclination angle, and feeding quantity on the grading performance. The results showed that the grading efficiency first increased and then decrease, with an increase in the number of rice field eels, while the accuracy decreased gradually. The grading efficiency increased, as the inclination angle of the grading sieve increased, whereas the grading accuracy decreased. Furthermore, the grading efficiency increased continuously, with increasing vibration frequency, while the grading accuracy first increased and then decreased. Subsequently, a multi-factor orthogonal experiment was applied to identify the relative importance of each parameter and their combined influence on grading efficiency and accuracy. Physical experiments were further verified under optimal parameters using a prototype grading machine. A comparison was made on the numerical predictions and measurement. The results showed that the greatest influencing factors on both grading accuracy and efficiency were the grading sieve inclination angle, followed by feeding quantity and vibration frequency. The grading performance was reduced, due to insufficient dispersion, material accumulation, or excessive sliding velocity on the sieve surface. Parameters was then optimized to improve grading performance using Design-Expert software, with the grading efficiency and grading accuracy as the objective variables. The optimal combination of parameters was determined as a vibration frequency of 30 Hz, a grading sieve inclination angle of 2.6°, and a feeding quantity of 27 individuals. The better performance was achieved in the grading efficiency of 0.637 individuals per second, and the average grading accuracy of 0.867. The relative errors between experiment and simulation were 7.378% for the grading efficiency and 3.46% for the grading accuracy, indicating better consistency and prediction of the RecurDyn–EDEM coupled simulation. The optimal grading parameters were obtained from the complex interaction between vibration-driven machinery and elongated aquatic organisms. A reliable basis can provide for the structure and performance of eel vibratory grading equipment. This finding can offer practical technical support for the intelligent, efficient, and scalable grading of aquatic products with similar morphologies.

The scale of Monopterus albus farming in Hubei Province is large, but there are few pre-treatment processing devices. The current Monopterus albus pretreatment device is mainly dissected and killed. Aiming at the problems of poor stability, low efficiency, and low meat yield of existing Monopterus albus deboning devices, an adaptive Monopterus albus deboning device was designed, which was mainly composed of laparotomy components, transitional components, and deboning components. The theoretical analysis of the process of fish laparotomy, transition transportation, and deboning was carried out, and the key factors affecting the performance of the deboning device were obtained. Taking the meat yield rate and sensory quality scores as evaluation indexes, the single-factor test of the distance between the pressure wheel and the V-block, the initial clearance of the transition wheel, the rotational speed of the transition wheel, the shape of the deboning blade disc and the rotational speed of deboning blade disc were carried out to determine the reasonable range of each parameter. The test results showed that when the distance between the pressure wheel and the V-block was 15.50-16.75 mm, the meat yield rate was higher; when the initial clearance of the transition wheel was 9 mm, the sensory quality scores of the fish body was the highest; the increase of the rotational speed of the transition wheel and the rotational speed of the deboning blade disc is beneficial to improve the meat yield rate and sensory quality scores; and the shape of the boning blade disc had little influence on the meat yield rate and the sensory quality scores. The orthogonal test of four factors and three levels was carried out with the distance between the pressure wheel and the V-block, the initial clearance of the transition wheel, the rotational speed of the transition wheel, and the rotational speed of the deboning blade disc as the test factors. The results showed that the order of significance of each test factor on the meat yield rate was the distance between the pressure wheel and the V-block, the initial clearance of the transition wheel, the rotational speed of the transition wheel, and the rotational speed of the deboning blade disc; and the order of significance on the sensory quality scores was the initial clearance of the transition wheel, the distance between the pressure wheel and the V-block, the rotational speed of the transition wheel and the rotational speed of the deboning blade disc. When the distance between the pressure wheel and the V-block was 16.75 mm, the initial clearance of the transition wheel was 9 mm, the rotational speed of the transition wheel was 648 r/min, and the rotational speed of the deboning blade disc was 3 200 r/min, the deboning effect was the best. The meat yield rate of the deboning device was 84%, and the total sensory quality scores of the fish after processing reached 17.3. The device can process Monopterus albus with a body mass of 75-150 g, and the production efficiency reaches 16.8 strips/min. Compared with the current commercially available deboning device, the feeding is more convenient and the production efficiency is higher. It can provide a reference for the research of Monopterus albus pretreatment device.

Monopterus albus is one of the popular aquatic fish in Asia. Manual processing of eel cannot fully meet the large-scale production at present, due to the time-consuming, laborious, and low safety. In view of its slender and slimy body, an eel-cutting machine is required for the consumption of Monopterus albus. In this study, a miniature machine of automatic cutting was designed for the living Monopterus albus with a sticky surface. The machine consisted of conveying, clamping, and cutting parts. The double-clamped wheel to roller was used to capture the eel for transportation during cutting. The switch between laparotomy and back dissection was realized to change the feeding channel. The adaptive mechanism was equipped to meet the requirements of different sizes of eel cutting. Firstly, the geometry and weight parameters of Monopterus albus were measured using a straight ruler and precision electronic balance. The tribological parameters on the surface of Monopterus albus were measured by the inclined plane. The mechanical parameters of Monopterus albus meat were verified by compression test. Secondly, according to the rigid-flexible coupling principle, the rigid-damping model was equivalent to the contact between the Monopterus albus body and the clamping wheel and slide. The rigid-flexible coupling model was established by Abaqus and Adams simulation software. The analysis model was optimized to take the conveying time of the fish body, output speed, clamping force, and whole machine vibration as the test indexes in single-factor tests, such as the spring stiffness, slope Angle of the slide, and the speed of the clamping wheel. The results show that the clamping force first increased and then decreased with the increase of spring stiffness and the vibration amplitude of the whole machine decreased. But there was little influence on conveying time and output speed. The output time of the fish body decreased with the increase of slope angle, while the output speed, clamping force, and vibration of the whole machine increased. There was an increase in the conveying time of the fish body, the output speed, the clamping force, and the vibration of the whole machine, with the increase of the speed of the clamping wheel. The single- and multi-factor analyses were carried out to obtain the optimal working conditions. Specifically, the clamping wheel speed was 600 r/min, the spring stiffness was 1.2×10³ N/m, and the slope angle was 16°. Finally, the processing experiment was performed on the automatic cutting machine for Monopterus albus. There was consistency in the vibration amplitude range and the relationship between the three directions of the machine measuring points with the theoretical analysis. At the same time, the output speed of the fish body output machine was also measured to better agree with the theoretical analysis. The cutting of the machine under optimal working conditions has fully met the requirements. The correctness of the theoretical analysis was also verified by the test. The rigid-flexible coupling model can provide a strong reference to research and develop the subsequent equipment.