scholarly journals Calibration and Verification Test of Lily Bulb Simulation Parameters Based on Discrete Element Method

2021 ◽  
Vol 11 (22) ◽  
pp. 10749
Author(s):  
Zhenwei Dai ◽  
Mingliang Wu ◽  
Zhichao Fang ◽  
Yongbo Qu
Keyword(s):  
Friction Coefficient ◽  
Static Friction ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Recovery Coefficient ◽  
Q235 Steel ◽  
Dynamic Friction Coefficient ◽  
Contact Parameters ◽  
Lily Bulb

In the simulation analysis of the lily harvesting process, the intrinsic parameters of the lily bulb and the contact parameters between the lily bulb and the lily mechanized harvesting equipment (Q235 steel) are deficient. Thus, the three-axis size, density, moisture content, Poisson’s ratio, elastic modulus, and other parameters of lily bulbs are measured in this paper with lily bulbs as the research object. Moreover, the discrete element model of the lily bulb was established using 3D scanning technology. The contact parameters between the lily bulb and Q235 steel were calibrated through bench test and simulation parameter test. The relative error between the measured value of the lily bulb accumulation angle and the simulated value is taken as response value to calibrate three parameters (collision recovery coefficient, static friction coefficient, and dynamic friction coefficient between lily bulbs). A regression model of the relative error of the stacking angle and three parameters is established, and the response surface is optimized. The results demonstrate that collision recovery coefficient, static friction coefficient, and dynamic friction coefficient between lily bulb and Q235 steel are 0.301, 0.423, and 0.063, respectively; these coefficients between lily bulbs are 0.455, 0.425, and 0.158, respectively. Additionally, a better combination of parameters is adopted to perform the simulation stacking test. The measured stacking angle is 32.31°, which is 0.34% in error with the stacking angle obtained by the physical stacking test. The test results suggest that the discrete element model and contact parameters of the lily bulb can be used in the discrete element simulation test. Furthermore, these research results could provide references for simulation tests, such as mechanized harvesting and post-harvest processing, of lily.

scholarly journals A GENERAL MODELLING APPROACH FOR COATED COTTON-SEEDS BASED ON THE DISCRETE ELEMENT METHOD

2021 ◽  
pp. 221-230
Author(s):  
Long Wang ◽  
Can Hu ◽  
Xiaowei He, ◽  
Wensong Guo ◽  
Xufeng Wang ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Relative Error ◽  
Optimal Solution ◽  
Static Friction ◽  
Element Model ◽  
Discrete Element ◽  
Physical Test ◽  
Dynamic Friction Coefficient ◽  
Two Parameters ◽  
Coated Cotton

In the current paper, a coated cotton-seed discrete element model was established. Furthermore, we designed a device for the simultaneous determination of the repose and accumulation angles, and Plackett–Burman and central composite design (CCD) tests were performed with the repose and accumulation angles as the test indexes. The static friction coefficient between seeds (SFCC) and the dynamic friction coefficient between seeds (DFCC) were observed to have a significant influence on the indexes and were thus selected for the subsequent analysis (P < 0.05). Analysis of variance revealed the terms of these two parameters to have a significant effect on the relative error of the repose angle (RERA) and the relative error of accumulation angles (REAA) (P < 0.05). A solution to the proposed mathematical model was determined via the NSGA-Ⅱ genetic algorithm and the Pareto optimal solution set was obtained. Based on multi-objective optimization, the SFCC and DFCC were determined as 0.174 and 0.068, for RERA and REAA values of 1.715% and 1.712%, respectively. Simulations were then performed using the optimal parameters. Results of the T-test demonstrated that there were no significant differences between the simulated and physical test results.

Discrete element model (DEM) simulations of cone penetration test (CPT) measurements and soil classification

2020 ◽  
Vol 57 (9) ◽  
pp. 1369-1387 ◽  
Author(s):  
A. Khosravi ◽  
A. Martinez ◽  
J.T. DeJong
Keyword(s):  
Soil Classification ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Interparticle Contact ◽  
Cone Penetration ◽  
Dem Simulations ◽  
Tip Resistance ◽  
Contact Parameters ◽  
Insight Into

This paper presents a study on the simulation of cone penetration tests (CPTs) using the discrete element model (DEM) method. This study’s main objective is to investigate the effect of different modeling parameters and simulation configurations on the ability of three-dimensional DEM simulations to replicate realistic CPT tip resistance (qc) and friction sleeve shear stress (fs) measurements. The CPT tests were simulated in virtual calibration chambers (VCCs) containing particles calibrated to model the behavior of sand. The parameters investigated included the granular assembly properties, interparticle contact parameters, particle–probe interface characteristics, and simulation configuration. Results indicate that the interparticle contact parameters, boundary conditions, and void ratio have an important role in the tip resistance and friction sleeve measurements obtained from the simulations. Particle-level interactions such as particle displacements and rotations and interparticle contact forces were analyzed throughout to provide insight into the differences in measured CPT response. Interpretation of the qc and fs measurements using soil behavior type (SBT) charts for soil classification indicates that the simulated CPT response is representative of the response of coarse-grained soils measured during field soundings. Analysis of results within the SBT framework can provide insight into the influence of soil particle properties on CPT-based soil classification.

scholarly journals Calibration and Verification of Dynamic Particle Flow Parameters by the Back-Propagation Neural Network Based on the Genetic Algorithm: Recycled Polyurethane Powder

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3350
Author(s):  
Ping He ◽  
Yiwei Fan ◽  
Banglong Pan ◽  
Yinfeng Zhu ◽  
Jing Liu ◽  
...  
Keyword(s):  
Neural Network ◽  
Genetic Algorithm ◽  
Friction Coefficient ◽  
Back Propagation ◽  
Static Friction ◽  
Discrete Element ◽  
Calibration Method ◽  
Angle Of Repose ◽  
Recovery Coefficient ◽  
Static Friction Coefficient

The discrete element method (DEM) is commonly used to study various powders in motion during transportation, screening, mixing, etc.; this requires several microscopic parameters to characterize the complex mechanical behavior of the particles. Herein, a new discrete element parameter calibration method is proposed to calibrate the ultrafine agglomerated powder (recycled polyurethane powder). Optimal Latin hypercube sampling and virtual simulation experiments were conducted using the commercial DEM software; the microscopic variables included the static friction coefficient between the particles, collision recovery coefficient, Johnson–Kendall–Roberts surface energy, static friction coefficient between the particles and wall, and collision recovery coefficient. A predictive model based on genetic-algorithm-optimized feedforward neural network (back propagation) was developed to calibrate the microscopic DEM simulation parameters. The cycle search algorithm and mean-shift cluster analysis were used to confirm the input parameters’ range by comparing the mean value of the dynamic angle of repose measured via the batch accumulation test. These parameters were verified by the baffle lifting method and the rotating drum method. This calibration method, once successfully developed, will be suitable for use in a variety of fine viscous powder dynamic flow conditions.

Calibration and Experimental Validation of Contact Parameters for Oat Seeds for Discrete Element Method Simulations

2021 ◽  
Vol 37 (4) ◽  
pp. 605-614
Author(s):  
Lingxin Geng ◽  
Jiewen Zuo ◽  
Fuyun Lu ◽  
Xin Jin ◽  
Chenglong Sun ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Discrete Element Method ◽  
Static Friction ◽  
Discrete Element ◽  
Rolling Friction ◽  
Angle Of Repose ◽  
Static Friction Coefficient ◽  
Contact Parameters ◽  
Rolling Friction Coefficient ◽  
Element Method

Highlights The static friction coefficient and rolling friction coefficient of oat seeds were calibrated by the discrete element method. Two representative oat varieties were selected. The hollow cylinder method and sidewall collapse method were used together to reduce the test error. Abstract . Hulless and shelled oat are two types of oat with major differences in physical appearance. To study the contact parameters between the two different oat seed types, these parameters were delineated with the discrete element method and graphic image processing technology. Using plexiglass as the contact material, the experiments used two different angle of repose measurement methods—hollow cylinder and collapse sidewall devices, to perform bench and simulation experiments on the two different oats. Under different measurement methods, bench experiments measured the angles of repose of the two oat seed types at 33.19°, 33.82° and 22.45°, 23.57°; the static friction coefficient and rolling friction coefficient were the experimental factors, and the angle of repose was the experimental indicator in the simulation. The steepest climbing experiment determined the optimal range of the experimental factor, and the regression equation between the static friction coefficient, rolling friction coefficient and angle of repose was established by a quadratic orthogonal rotation combination experiment. Finally, the angles of repose measured by the bench experiment with the two different measurement methods were treated as target values, the coefficient of static friction and the coefficient of rolling friction were solved; the coefficient of static friction between hulless oats was 0.36, and the coefficient of rolling friction between hulless oats was 0.052; the coefficient of static friction between shelled oats was 0.24, and the coefficient of rolling friction between shelled oats was 0.036. The obtained contact parameters between seeds were input into EDEM, the simulation and bench experiment results were verified. The difference between the simulation results and the actual values was within 3%. The angle of repose of oats after calibration was close to the actual situation, and the calibration results had high reliability and provided a referencefor the measurement of contact parameters between other agricultural crop seeds. Keywords: Calibration, Contact parameters, Discrete element method, Oat.

scholarly journals CONSTRUCTION OF A DISCRETE ELEMENT MODEL OF BUCKWHEAT SEEDS AND CALIBRATION OF PARAMETERS

2021 ◽  
pp. 175-184
Author(s):  
Bing Xu ◽  
Yanqing Zhang ◽  
Qingliang Cui ◽  
Shaobo Ye ◽  
Fan Zhao
Keyword(s):  
Stainless Steel ◽  
Friction Coefficient ◽  
Static Friction ◽  
Discrete Element ◽  
Rolling Friction ◽  
Restitution Coefficient ◽  
Steel Rolling ◽  
Static Friction Coefficient ◽  
Contact Parameters ◽  
Rolling Friction Coefficient

In view of the lack of seeds contact parameters that can be used as a reference for the design of key mechanical components such as buckwheat planting, harvesting, and processing, this study combines simulation optimization design experiments and physical experiments to calibrate the parameters of simulated discrete element of buckwheat seeds. The non-spherical particle model of buckwheat seeds was established using the automatic filling method, and the simulation accumulating test and physical accumulating test were carried out using the bottomless conical cylinder lifting method; the repose angle of buckwheat seeds was taken as the response value, and the initial parameters were screened for significance based on the Plackett-Burman test; and a second-order regression model of the error value for the repose angle and the significance parameter was established based on the steepest climb test and Box-Behnken test. On this basis, the minimum error value of the repose angle was used as the goal to optimize the significance parameter, the optimal combination of contact parameters was obtained, and parameter validation tests were carried out. The significance screening test showed that the buckwheat-buckwheat static friction coefficient, the buckwheat-stainless steel rolling friction coefficient, and the buckwheat-stainless steel restitution coefficient had significant effects on the repose angle of buckwheat (P<0.05). The optimization test showed that the buckwheat-buckwheat static friction coefficient was 0.510, the buckwheat-stainless steel rolling friction coefficient was 0.053, and the buckwheat-stainless steel restitution coefficient was 0.492. The validation test showed that the repose angle of buckwheat seeds under such parameter was 25.39°, and the error with the repose angle of the physical test was 0.55%, which indicated that the optimal parameter combination was reliable. This study could provide a seed model and simulation contact parameters for the research and development of buckwheat sowing, threshing and hulling machinery.

scholarly journals Discrete element model for general polyhedra

2021 ◽  
Author(s):  
Alfredo Gay Neto ◽  
Peter Wriggers
Keyword(s):  
Frictional Contact ◽  
Virtual Work ◽  
Particle Surface ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Principle Of Virtual Work ◽  
Dynamics Model ◽  
Railway Ballast ◽  
Multibody Dynamics Model

AbstractWe present a version of the Discrete Element Method considering the particles as rigid polyhedra. The Principle of Virtual Work is employed as basis for a multibody dynamics model. Each particle surface is split into sub-regions, which are tracked for contact with other sub-regions of neighboring particles. Contact interactions are modeled pointwise, considering vertex-face, edge-edge, vertex-edge and vertex-vertex interactions. General polyhedra with triangular faces are considered as particles, permitting multiple pointwise interactions which are automatically detected along the model evolution. We propose a combined interface law composed of a penalty and a barrier approach, to fulfill the contact constraints. Numerical examples demonstrate that the model can handle normal and frictional contact effects in a robust manner. These include simulations of convex and non-convex particles, showing the potential of applicability to materials with complex shaped particles such as sand and railway ballast.

Study on Machining Mechanism of Glass Using Discrete Element Method

2014 ◽  
Vol 577 ◽  
pp. 108-111 ◽  
Author(s):  
Ying Qiu ◽  
Mei Lin Gu ◽  
Feng Guang Zhang ◽  
Zhi Wei
Keyword(s):  
Discrete Element Method ◽  
Element Model ◽  
Discrete Element ◽  
Rake Angle ◽  
Milling Process ◽  
Micro Milling ◽  
Discrete Element Model ◽  
Machined Surface ◽  
Damage Depth ◽  
Element Method

The discrete element method (DEM) is applied to glass micromachining in this study. By three standard tests the discrete element model is established to match the main mechanical properties of glass. Then, indentating, cutting, micro milling process are simulated. Results show that the vertical damage depth is prevented from reaching the final machined surface in cutting process. Tool rake angle is the most remarkable factor influencing on the chip deformation and cutting force. The final machined surface is determined by the minimum cutting thickness per edge. Different cutting thickness, cutter shape and spindle speed largely effect on the mechanism of glass.

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