Parameter Optimization and Experimental Study on Alfalfa Stem Flattening Process Based on DEM–MBD
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this study, an alfalfa flattening modulation device with adjustable gap was designed based on the DEM-MBD joint simulation technique, and the adaptive performance of the double-spring floating pressure mechanism was verified through parameter optimization experiments, and the optimal parameter combinations (feeding volume of 5.10 kg/s, roller speed of 686.87 r/min, and spring preload force of 670.02 N) were proposed and verified in field tests. The innovations are the use of rigid-flexible coupling model and DEM-MBD joint simulation method to analyze the dynamic modulation process, and the design of double-spring floating pressure mechanism. There are some urgent problems that need to be solved in order to improve the overall scientific validity of the study:
1.The specific implementation process (boundary conditions) of the DEM-MBD coupled simulation is not described in detail, which affects the reproducibility.The mechanical parameters of alfalfa stalks in the DEM model only rely on literature references, and the accuracy of the rigid-flexible coupled model is not verified by experiments.
2. the basis for determining the range of feeding volume (3.47-10.41 kg/s) in the Box-Behnken experiment, and its relationship with the operating speed of the implement.
3. Key environmental parameters such as soil moisture, alfalfa variety maturity or plant density in the field trials were not clearly stated, which affected the generalizability of the results.
4. The scope of application of the optimized parameters (e.g., whether they are only applicable to specific alfalfa varieties or harvesting stages) is not discussed, nor is there any mention of the adaptability of the equipment to complex terrain (e.g., slopes).
5. The terminology (e.g., “DEM-MBD”, “rigid-flexible coupling model”) is not clearly defined or explained when it appears for the first time, which makes it more difficult for non-specialized readers to understand.
6. The transition between chapters is hard and lacks logical guiding sentences. For example, from “Theoretical Analysis” to “Simulation Experiment”, the correlation between the two is not explained.
7. The abstract states that the goal is to solve the problem of “high stalk breakage rate”, but the introduction does not quantify the baseline breakage rate of conventional equipment.
8. There are two versions of the Bonging model in EDEM2022, V1 and V2, so please clarify the version of the model used in this study.
Language needs to be touched up to improve readability.
Author Response
Comments from reviewer:1
Comment: [The specific implementation process (boundary conditions) of the DEM-MBD coupled simulation is not described in detail, which affects the reproducibility.The mechanical parameters of alfalfa steams in the DEM model only rely on literature references, and the accuracy of the rigid-flexible coupled model is not verified by experiments.]
Response: Thanks for your suggestion, the paper has been supplemented with the relevant content of DEM-MBD coupled simulation boundary conditions in the section of “4.3. Simulation Design of Experiments Coupled Simulation Modeling”. Since the parameters of alfalfa straw have been comprehensively studied by many scholars, the research results of related scholars are cited directly. The main purpose of the article is to investigate the interaction between the compression force and shear force generated by the modulating roller on the steams of alfalfa steams in the process of flattening and modulation, and to analyze the interaction between the steams. In this paper, the accuracy of the rigid-flexible coupling model is determined according to the state of alfalfa steam compression modulation by pre-testing to verify the modulation treatment of a single steam.
Comment: [The basis for determining the range of feeding volume (3.47-10.41 kg/s) in the Box-Behnken experiment, and its relationship with the operating speed of the implement.]
Response: Thank you for your suggestion. We have highlighted all the revisions made to the manuscript to facilitate review by editors and reviewers.Thank you for your suggestion. In this paper, according to the alfalfa planting density and the forward speed of the machine is 1.4-4.2 m/s, by studying the geometry of alfalfa steam plants (Table 3 Alfalfa stem geometry.) and planting density, and through the formula (9), the feeding volume is converted into the number of steams fed, and the number of steams is converted, and the range of the device feeding volume is finally determined as 3.47-10.41 kg/s .
Comment: [Key environmental parameters such as soil moisture, alfalfa variety maturity or plant density in the field trials were not clearly stated, which affected the generalizability of the results.]
Response: Thank you for your suggestion. Alfalfa steams are mainly harvested from the bud stage to the early flowering stage because the crude protein content of alfalfa steams and leaves harvested in this period is at a higher level, and at this time, the proportion of leaves is large, the fiber content is low, and the palatability and digestibility are optimal, so this paper mainly focuses on exploring the harvest in this period. The environmental parameters of alfalfa variety “Zhongtian No.1” and “harvesting alfalfa from the pre-bloom to the early flowering stage” have been added in the paper in “Test Conditions and Equipment”, but the soil humidity, temperature and other soil parameters are very important for alfalfa harvesting, However, soil parameters such as soil moisture, temperature and other soil parameters had less influence on the flattening and modification process of alfalfa steams, so they were not described.
Comment: [The scope of application of the optimized parameters (e.g., whether they are only applicable to specific alfalfa varieties or harvesting stages) is not discussed, nor is there any mention of the adaptability of the equipment to complex terrain (e.g., slopes).]
Response: Thanks for your suggestion, the paper has added the alfalfa species and harvesting stage in the section of “Test Conditions and Equipment”, as well as the terrain environment of alfalfa field trial harvesting. According to “GB/T 21899-2008 Mowing and flattening machine”, during the field test, after the prototype passes through the first 20 m of the stabilization zone, five random samples are selected in the stabilization zone in the forward direction, and the length of each sample area is 1 m. Each group of samples is repeated three times, and the results of the test are taken as the average value. The actual mass of harvested alfalfa steams, the mass of flattened alfalfa steams, and the crushed grass mass of the steams were measured separately.
Comment: [The terminology (e.g., “DEM-MBD”, “rigid-flexible coupling model”) is not clearly defined or explained when it appears for the first time, which makes it more difficult for non-specialized readers to understand.]
Response: Thanks to your suggestion, the paper has provided clear definitions and explanations of “DEM-MBD” and “rigid-flexible coupled model” where they first appear, and MBD-DEM refers to a simulation method that combines multibody dynamics with discrete elements, and rigid-flexible coupled model refers to a simulation method that combines a rigid-body dynamics model with a flexible-body dynamics model. MBD-DEM refers to the simulation calculation method combining multi-body dynamics and discrete elements, and rigid-flexible coupling model refers to the simulation calculation method combining rigid-body dynamics and flexible-body dynamics.
Comment: [The transition between chapters is hard and lacks logical guiding sentences. For example, from “Theoretical Analysis” to “Simulation Experiment”, the correlation between the two is not explained.]
Response: Thank you for your suggestion, the paper has been added in the “3.3. Analysis of Alfalfa Stem Flattening and Modulation Process” between "According to the analysis of the force of the modulation roller rubber teeth meshing drive, in the process of alfalfa steam flattening and modulation, the alfalfa steam is mainly subjected to the compression force and the shear force generated by the modulation roller. In order to investigate the physical changes of alfalfa steams under the two forces, biomechanical characterization of alfalfa steams was tested." The logical guiding statement that reinforces the relevance and transition between the two parts.
Comment: [The abstract states that the goal is to solve the problem of “high stalk breakage rate”, but the introduction does not quantify the baseline breakage rate of conventional equipment.]
Response: Thanks to your suggestion, the paper has added a comparison between the “dual-spring floating pressure mechanism” and the traditional “fixed-drive” equipment in the part of “3.1. Flattening and Modulating Device Structure”, which is used to To strengthen the innovation of “dual-spring floating pressure mechanism” to solve the problem of “high steam breakage rate”.
Comment: [There are two versions of the Bonging model in EDEM2022, V1 and V2, so please clarify the version of the model used in this study.]
Response: Thank you for your suggestion. The EDEM software contains two physical models, bonding V2 and bonding. The Bonging model can be used to bond a limited number of particles of a certain size into a larger particle by bonding the spheres together through the bonding bond, which is mainly suitable for simple bonding application scenarios of macroscopic particles. While the BongingV2 model is applicable to the viscoelastic behavior of microscopic powdery particles. Since the model established in this paper is the alfalfa steam model and the individual generated particles are large in size, the Bonging model is used which is more in line with the model establishment of alfalfa steam.
Reviewer 2 Report
Comments and Suggestions for AuthorsTo the presented material - Parameter Optimization and Experimental Study on Alfalfa Stem Flattening Process Based on DEM-MBD
The study examines the problem of uneven flattening and high degree of stem breakage during field conditioning operations with alfalfa.
The study investigates a current problem of the effect of machine operation on the deformation of alfalfa stems. Due to the fact that this is a biological unit that is difficult to accurately describe and changes (emulates), it is necessary to study the parameters. These studies would be useful for developers of agricultural machinery.
The material is well developed and contains a descriptive part in section 3.1., a theoretical part in section 3.2, and an analytical part in section 3.3 Analysis of the process of flattening and modulation of the alfalfa stem.
In sections 4.1. and 4.2, modeling is done. T. 4.3 is presented a simulation model in SolidWorks is a detailed description of the conducted simulations.
In 4.6. Test Results and Analysis is presented an analysis Based on the Box-Behnken
for review I have the following comments:
- Make a description under the tables (as an example Table 7. ) about the meaning of X1-3 and Y1,2.
In section 5 is presented in detail the experiment, to which I have the following comment:
- Please compare your study with similar studies and give a comparison of the results.
And in conclusion it would be clearer to formulate the obtained results and conclusions:
- Present in more detail Conclusions.
Author Response
Comments from reviewer:2
Comment: [Make a description under the tables (as an example Table 7. ) about the meaning of X1-3 and Y1,2.]
Response: Thanks to your suggestion, the paper has added explanations about the meaning of X1-3 and Y1,2 in Table 7. The feeding amount is X1, the modulating roller speed is X2, the buffer spring preload force is X3, the crushing rate is Y1, and the bonding key fracture rate is Y2.
Comment: [Please compare your study with similar studies and give a comparison of the results.]
Response: Thanks to your suggestion, the paper has been supplemented with a comparison with similar studies in the section “Test Conditions and Equipment”. According to the experimental results, the average flattening rate and grass breakage rate were 95.71 % and 1.73 %, respectively. Compared with the simulation optimization results, the bonding key fracture rate and bonding key fracture rate were 95.81 % and 1.35 %, respectively, which showed a small error compared with the predicted values, and the optimization results were reliable. It shows that the developed flattening and modulating device can be adapted to different feeding amounts and can flatten and modulate alfalfa steams in a good way.
Comment: [Present in more detail Conclusions.]
Response: Thanks to your suggestion, the paper has been supplemented with the details of the experimental results in “6 Conclusions”. In the article, a gap adjustable flattening modulation device was designed, and the theoretical analysis of the flattening modulation process of alfalfa steams and related mechanical tests were carried out, and the analysis and parameter optimization of the flattening modulation device were completed by using MBD-DEM coupled simulation.
Reviewer 3 Report
Comments and Suggestions for AuthorsGENERAL OVERVIEW OF THE PAPER
The paper presents the design and optimization of a gap-adjustable flattening and modulating device for alfalfa stems. It employs DEM-MBD coupled simulations to analyze and optimize key parameters such as feeding amount, roller speed, and spring preload force. The device's performance is validated through field trials, achieving high flattening and low breakage rates, meeting operational requirements for alfalfa conditioning.
ABSTRACT
The abstract lacks discussion of how the device performs under different alfalfa varieties, field conditions, or moisture levels, making it hard to judge how it will function in real-life application.
Although the abstract mentions both simulation and field trials, it does not clearly describe how the simulation results were validated against the field data.
INTRODUCTION
The introduction gives good technical details but does not explain how the research will benefit farmers or equipment makers.
THEORETICAL ANALYSIS OF ALFALFA FLATTENING AND MODULATION PROCESS
The shift from the theoretical analysis to the biomechanical tests of alfalfa stems feels sudden. While both parts are important, the manuscript doesn't clearly show how the calculated forces relate to the results of the compression and shear experiments
DEM-MBD BASED SIMULATION TEST
The use of DEM-MBD coupling and tools like RecurDyn and EDEM is a solid approach for modeling the flattening of alfalfa stems. However, the section does not provide enough validation of the simulation results using experimental or field data.
It’s unclear how well the simulated outcomes—such as crushing rate, fracture rate of bonding keys, or deformation behavior—match real-world observations or tests.
Also, key variables like spring preload forces, contact parameters from the Hertz-Mindlin model, and the modulus of elasticity of alfalfa stem segments are mentioned, but their sources (whether from literature or experiments) are not clearly stated.
The authors should include a comparative analysis between simulation results and actual lab or field test outcomes to confirm the accuracy of the model.
EXPERIMENTAL VALIDATION
The field experiment provides useful data on the prototype’s performance, but it doesn't explain how factors like temperature, humidity, and soil conditions might have affected the results. Since alfalfa stem properties can change with these conditions, their influence should be considered for a more thorough validation of the prototype’s effectiveness.
The experimental procedure mentions taking the average of 10 measurements to evaluate the stem flattening and crushing rates, but it is unclear whether these measurements were replicated across different locations or times. There is no mention of statistical analysis (such as standard deviation, confidence intervals, or error analysis) to assess the consistency and reliability of the results.
CONCLUSION
The conclusions accurately summarize the paper
REFERENCES
The references are generally current and relevant, with a good mix of recent studies (2023-2024) on alfalfa stem conditioning and related agricultural machinery. The quality is high, as most sources are peer-reviewed journals, but the quantity could be expanded to include more foundational studies to support the research further.
Author Response
Comments from reviewer:3
Comment: [The abstract lacks discussion of how the device performs under different alfalfa varieties, field conditions, or moisture levels, making it hard to judge how it will function in real-life application.]
Response: Thank you for your suggestion. The main research object of the thesis is “Zhongtian No.1” alfalfa, and the field test is mainly for verifying the intrinsic relationship and optimal parameter combinations between the flattening and modulating devices, and the thesis has already added the alfalfa species and harvesting stage in the part of “Test Conditions and Equipment”, and added the terrain environment for harvesting in the field test. In the section “Test Conditions and Equipment”, the paper has added the varieties of alfalfa and the harvesting stage, and also the topographic environment of alfalfa field trial harvesting.
Comment: [Although the abstract mentions both simulation and field trials, it does not clearly describe how the simulation results were validated against the field data.]
Response: Thanks to your suggestion, the paper has been supplemented with a comparison with similar studies in the section “Test Conditions and Equipment”. According to the experimental results, the average flattening rate and grass breakage rate were 95.71 % and 1.73 %, respectively. Compared with the simulation optimization results, the bonding key fracture rate and bonding key fracture rate were 95.81 % and 1.35 %, respectively, which showed a small error compared with the predicted values, and the optimization results were reliable. It shows that the developed flattening and modulating device can be adapted to different feeding amounts and can flatten and modulate alfalfa steams in a good way.
Comment: [The introduction gives good technical details but does not explain how the research will benefit farmers or equipment makers.]
Response: Thanks for your suggestion, the paper has added the significance of researching the alfalfa steam flattening modulation process in the part of “0 Introduction”, and through the use of MBD-DEM coupled simulation technology, the main factors affecting the operational performance of the flattening modulation device are identified and simulation experiments are carried out to get the optimal parameter combinations affecting the quality of the modulation, which can be used to enhance the flattening rate and reduce the broken grass rate during harvesting, and improve the operational efficiency of the harvesting equipment. The optimal combination of parameters affecting the modulation quality was obtained to enhance the flattening rate of alfalfa steams and reduce the grass fragmentation rate during harvesting, so as to improve the operational efficiency of harvesting.
Comment: [The shift from the theoretical analysis to the biomechanical tests of alfalfa stems feels sudden. While both parts are important, the manuscript doesn't clearly show how the calculated forces relate to the results of the compression and shear experiments.]
Response: Thank you for your suggestion, the paper has been added in the “3.3. Analysis of Alfalfa Stem Flattening and Modulation Process” between "According to the analysis of the force of the modulation roller rubber teeth meshing drive, in the process of alfalfa steam flattening and modulation, the alfalfa steam is mainly subjected to the compression force and the shear force generated by the modulation roller. In order to investigate the physical changes of alfalfa steams under the two forces, biomechanical characterization of alfalfa steams was tested." The logical guiding statement that reinforces the relevance and transition between the two parts.
Comment: [The use of DEM-MBD coupling and tools like RecurDyn and EDEM is a solid approach for modeling the flattening of alfalfa stems. However, the section does not provide enough validation of the simulation results using experimental or field data.]
Response: Thank you for your suggestion, the paper has been added in the “3.4 Test factors and evaluation indexes” part of the initial deformation of the compression spring and buffer spring is set to 15 mm, the initial deformation of the buffer spring can be adjusted by the preload adjustment device, the range of adjustment is from 0 to 60 mm, so choose the buffer spring preload (240, 720, 1200 N) for the coupling test, and then control the modulation of the inter-roller force. Therefore, the preload force of the buffer spring (240, 720, 1200 N) is selected for the coupling test to control the force between the modulating rollers. The critical fracture force of alfalfa steams at the top, middle and root of alfalfa steams can be obtained through simulation as 26.5 N, 33 N and 75.1 N. The number of bonding keys at the top, middle and root of alfalfa steams are: 1993, 3904 and 6392, respectively.
Comment: [It’s unclear how well the simulated outcomes—such as crushing rate, fracture rate of bonding keys, or deformation behavior—match real-world observations or tests.]
Response: Thanks to your suggestion, the paper has been supplemented with a comparison with similar studies in the section “Test Conditions and Equipment”. According to the experimental results, the average flattening rate and grass breakage rate were 95.71 % and 1.73 %, respectively. Compared with the simulation optimization results, the bonding key fracture rate and bonding key fracture rate were 95.81 % and 1.35 %, respectively, which showed a small error compared with the predicted values, and the optimization results were reliable. It shows that the developed flattening and modulating device can be adapted to different feeding amounts and can flatten and modulate alfalfa steams in a good way.
Comment: [Also, key variables like spring preload forces, contact parameters from the Hertz-Mindlin model, and the modulus of elasticity of alfalfa stem segments are mentioned, but their sources (whether from literature or experiments) are not clearly stated.]
Response:Thanks for your suggestion, the flattening modulation device by adjusting the size of the “buffer spring preload” to change the modulation force of the device, through the alfalfa steam compression and shear test, it was finally determined that the buffer spring preload in the 240~1200N, the modulation force is in the interval of 136~157 N/cm. In this paper, the detailed parameters of Hertz-Mindlin with JKR and the material properties of alfalfa steam segments are added in “Table 5 Discrete element simulation parameters”.
Comment: [The authors should include a comparative analysis between simulation results and actual lab or field test outcomes to confirm the accuracy of the model.]
Response:Thanks to your suggestion, the paper has been supplemented with the details of the experimental results in “6 Conclusions”. In the article, a gap adjustable flattening modulation device was designed, and the theoretical analysis of the flattening modulation process of alfalfa steams and related mechanical tests were carried out, and the analysis and parameter optimization of the flattening modulation device were completed by using MBD-DEM coupled simulation.
Comment: [The field experiment provides useful data on the prototype’s performance, but it doesn't explain how factors like temperature, humidity, and soil conditions might have affected the results. Since alfalfa stem properties can change with these conditions, their influence should be considered for a more thorough validation of the prototype’s effectiveness.]
Response:Thank you for your suggestion. Alfalfa steams are mainly harvested from the bud stage to the early flowering stage because the crude protein content of alfalfa steams and leaves harvested in this period is at a higher level, and at this time, the proportion of leaves is large, the fiber content is low, and the palatability and digestibility are optimal, so this paper mainly focuses on exploring the harvest in this period. The environmental parameters of alfalfa variety “Zhongtian No.1” and “harvesting alfalfa from the pre-bloom to the early flowering stage” have been added in the paper in “Test Conditions and Equipment”, but the soil humidity, temperature and other soil parameters are very important for alfalfa harvesting, However, soil parameters such as soil moisture, temperature and other soil parameters had less influence on the flattening and modification process of alfalfa steams, so they were not described.
Comment: [The experimental procedure mentions taking the average of 10 measurements to evaluate the stem flattening and crushing rates, but it is unclear whether these measurements were replicated across different locations or times. There is no mention of statistical analysis (such as standard deviation, confidence intervals, or error analysis) to assess the consistency and reliability of the results.]
Response:Thanks for your suggestion, the paper has added the alfalfa species and harvesting stage in the section of “Test Conditions and Equipment”, as well as the terrain environment of alfalfa field trial harvesting. According to “GB/T 21899-2008 Mowing and flattening machine”, during the field test, after the prototype passes through the first 20 m of the stabilization zone, five random samples are selected in the stabilization zone in the forward direction, and the length of each sample area is 1 m. Each group of samples is repeated three times, and the results of the test are taken as the average value. The actual mass of harvested alfalfa steams, the mass of flattened alfalfa steams, and the crushed grass mass of the steams were measured separately.
In addition to the above comments, all spelling and grammatical errors pointed out by the reviewers have been revised.
