The tensile-shear interactive damage(TSID)model is a novel and powerful constitutive model for rock-like materials.This study proposes a methodology to calibrate the TSID model parameters to simulate sandstone.The bas...The tensile-shear interactive damage(TSID)model is a novel and powerful constitutive model for rock-like materials.This study proposes a methodology to calibrate the TSID model parameters to simulate sandstone.The basic parameters of sandstone are determined through a series of static and dynamic tests,including uniaxial compression,Brazilian disc,triaxial compression under varying confining pressures,hydrostatic compression,and dynamic compression and tensile tests with a split Hopkinson pressure bar.Based on the sandstone test results from this study and previous research,a step-by-step procedure for parameter calibration is outlined,which accounts for the categories of the strength surface,equation of state(EOS),strain rate effect,and damage.The calibrated parameters are verified through numerical tests that correspond to the experimental loading conditions.Consistency between numerical results and experimental data indicates the precision and reliability of the calibrated parameters.The methodology presented in this study is scientifically sound,straightforward,and essential for improving the TSID model.Furthermore,it has the potential to contribute to other rock constitutive models,particularly new user-defined models.展开更多
For the challenge of parameter calibration in the process of SWMM(storm water management model)model application,we use particle Swarm Optimization(PSO)and Sequence Quadratic Programming(SQP)in combination to calibrat...For the challenge of parameter calibration in the process of SWMM(storm water management model)model application,we use particle Swarm Optimization(PSO)and Sequence Quadratic Programming(SQP)in combination to calibrate the parameters and get the optimal parameter combination in this research.Then,we compare and analyze the simulation result with the other two respectively using initial parameters and parameters obtained by PSO algorithm calibration alone.The result shows that the calibration result of PSO-SQP combined algorithm has the highest accuracy and shows highly consistent with the actual situation,which provides a scientific and effective new idea for parameter calibration of SWMM model,moreover,has practical guidance for flood control and disaster mitigation.展开更多
Accurately simulating the crushing process of ore particles in a semi-autogenous grinding mill (SAG mill) is quite challenging. This study utilizes the discrete element method (DEM) to construct a breakage model for o...Accurately simulating the crushing process of ore particles in a semi-autogenous grinding mill (SAG mill) is quite challenging. This study utilizes the discrete element method (DEM) to construct a breakage model for ore particles. Calibration of the discrete element basic parameters and Tavares breakage model parameters is conducted based on angle of repose (AoR) tests and single-particle impact tests. 3D scanning is employed to capture the morphology of the ore for particle modeling. On this basis, a discrete element breakage model for ore particles is built for single-particle impact simulations and validated through testing to determine the calibrated model parameters. The results indicate that the AoR angles and stacking shapes from the simulation and tests are highly similar, with a relative error of about 0.19%. The similarity in crushing outcomes and quantitative values between single-particle impact simulations and tests preliminary validates the reliability of the calibration method and the applicability of the Tavares breakage model, successfully determining a group of model parameters suitable for simulating ore particle crushing processes. This study lays the groundwork for utilizing DEM to simulate the visualization of ore particle crushing.展开更多
To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River,which causes clogging of the fer...To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River,which causes clogging of the fertilizer discharger and leads to a reduction in the uniformity and stability of fertilizer discharge,research on the crushing mechanism of caking compound fertilizer was performed.Considering that it is difficult to measure the bonding force between caking fertilizer particles directly,a simulation model of caking composite fertilizer was established with the bonding model in EDEM discrete element software.To decrease error between the simulation and physical test results,the normal contact stiffness,tangential contact stiffness,critical normal stress,critical tangential stress,bonding radius,and other parameters of the bonding model of caking composite fertilizer were calibrated.The three-dimensional structure of the caking composite fertilizer was obtained via three-dimensional scanning,the critical crushing displacement and critical crushing force of the caking composite fertilizer were measured via compression testing with a mass spectrometer,and the optimal parameter combination of the bonding model was determined via EDEM discrete element simulation of the Plackett-Burman test,steepest ascent test,and Box-Behnken test.The results of the simulated compression tests under the optimal parameter combination show that the relative errors of the critical crushing displacement and critical crushing force with respect to the physical test results were 0.296%and 0.343%,respectively.Using the crushing rate of caking compound fertilizer as an evaluation index,the feasibility of the calibrated parameters was verified for a four-head spiral two-row fertilizer discharger installed in a direct seeding machine for oilseed rape.The results show that the relative errors of the caking fertilizer crushing rates from the simulation relative to those of the bench and field tests were 5.81%and 5.06%,respectively,indicating that the calibration parameters of the discrete element model were accurate and could be used for parameter analysis of caking fertilizer with a discrete element model.These results can provide a reference for the structural optimization of fertilizer discharger crushing of caking fertilizer of direct seeding machine for oilseed rape.展开更多
Understanding the biomechanical properties of safflowers is essential for appropriately designing harvesting machinery and optimizing the harvesting process.Safflower is a flexible crop that lacks a basis for relevant...Understanding the biomechanical properties of safflowers is essential for appropriately designing harvesting machinery and optimizing the harvesting process.Safflower is a flexible crop that lacks a basis for relevant simulation parameters,which causes difficulties in designing harvesting machinery.In this study,a calibration method for safflowers was proposed.First,a discrete element model was established by measuring the intrinsic parameters of a safflower,such as its geometric parameters,density,Poisson’s ratio,and modulus of elasticity.Second,the contact and bonding parameters were calibrated using a combination of physical and simulation tests.In the contact parameter tests,the Hertz-Mindlin(no-slip)model was implemented for the stacking angle tests conducted regarding the safflower filament.A regular two-level factorial design was used to determine the important factors and perform the steepest climb test.Moreover,the Box-Behnken design was adopted to obtain the optimal contact parameters.In the bonding parameter tests,the Hertz-Mindlin model with bonding contact was applied for the safflower shear simulation tests;moreover,the optimum bonding parameters were obtained through the central composite design test.The results demonstrated that the relative errors between the simulated and measured stacking angles and maximum shear were 3.19%and 5.29%,respectively.As a result,the safflower simulation parameters were accurately calibrated,providing a reference for appropriately setting the simulation parameters and designing key mechanical components.展开更多
To improve the survival rate of larvae during material separation after biotransformation of existing residual film mixtures of Protaetia brevitarsis larvae,this paper adopts the method of combining physical test and ...To improve the survival rate of larvae during material separation after biotransformation of existing residual film mixtures of Protaetia brevitarsis larvae,this paper adopts the method of combining physical test and EDEM simulation test,and selects Hertz Mindlin with JKR contact model to calibrate the discrete element simulation contact parameters of the Protaetia brevitarsis larvae and the frass mixture.First,the cylinder lifting method was used to determine the actual repose angle of the mixture of larvae and frass.The collision recovery coefficients between larvae-frass and steel,static friction coefficient,kinetic friction coefficient and the collision recovery coefficient between larvae were measured through physical tests such as the inclined plane method.The Plackett-Burman test was then used to screen out the factors that have a significant impact on the repose angle:Poisson’s ratio of frass,frass-frass rolling friction coefficient,frass JKR surface energy,frass-larvae JKR surface energy.The optimal value intervals of four significant factors were determined based on the steepest climb test,Based on the Box-Behnken response surface analysis test,the second-order regression model between the repose angle and four significant factors was determined,and variance and interaction effects were analyzed.And with the actual repose angle as the goal,the significant factors were optimized and the optimal parameter combination of the four significant factors was determined.The simulation test of material repose angle and screening was carried out with the optimal parameter combination,and compared with the physical test.It was found that the maximum relative errors of the two tests were 1.48%and 3.79%respectively,indicating that the calibrated parameter values are true and reliable,It can provide a reference for the discrete element simulation of the transportation and separation of the Protaetia brevitarsis larvae-frass mixture.展开更多
Due to the different microstructures caused by the heat source effect,welding joints exhibit significant differences in mechanical properties compared to the base material.Precise characterization of the constitutive ...Due to the different microstructures caused by the heat source effect,welding joints exhibit significant differences in mechanical properties compared to the base material.Precise characterization of the constitutive characteristics of the welded joint requires a large number of repetitive experiments,which are costly,inefficient,and have limited accuracy improvements.This paper proposes an integrated experimental-simulation-based inverse calibration method,which establishes a calibration optimization problem based on the corresponding constitutive model and a finite element calculation model built by the distribution of hardness in the weldment.Using the global tensile force-displacement curve of the MIG-welded 6005A-T6 aluminum alloy specimen and the experimental data of local deformation with time change obtained from DIC(Digital Image Correlation),the parameters involved in the constitutive models are optimized accordingly.This method can directly obtain the constitutive characteristics of the weldment under conditions of limited experiments and insufficient data.Additionally,the adaptability of the constitutive model to the calibration method and the influence of optimization results are discussed and analyzed.The results indicate that the global force-displacement response of the non-saturated Ramberg-Osgood(R-O)model is in the best agreement with that of the experimental data,and the energy error is only 2.62%,followed by the MPL model,while the saturation-based Voce model shows the largest simulation error in terms of the presented object.Furthermore,the simulation results of R-O,Voce,and MPL models in the local area are far superior to traditional fitting methods.展开更多
The shear pin of the friction pendulum bearing(FPB)can be made of 40Cr steel.In conceptual design,the optimal cut-off point of the shear pin is predetermined,guiding the design of bridges isolated by FPBs to maximize ...The shear pin of the friction pendulum bearing(FPB)can be made of 40Cr steel.In conceptual design,the optimal cut-off point of the shear pin is predetermined,guiding the design of bridges isolated by FPBs to maximize their isolation performance.Current researches on the shear pins are mainly based on linear elastic models,neglecting their plasticity,damage,and fracture mechanical properties.To accurately predict its cutoff behavior,the elastic-plastic degradationmodel of 40Cr steel is indeed calibrated.For this purpose,the Ramberg-Osgoodmodel,the Bao-Wierzbicki damage initiation criterion,and the linear damage evolution criterion were selected to develop the elastic-plastic degradation model of 40Cr.Subsequently,parameter calibration of this model was performed through uniaxial tensile tests on two sets of six smooth,round bars with different diameters.Following this,finite element simulations were conducted for the pure shear test of grade 10.9 high-strength bolts made of 40Cr steel,aiming to verify the elasticplastic degradation model.The results showed that the failure modes and force-displacement curves simulated by the finite element method were in good agreement with the test results.Moreover,the error between the primary characteristic parameters(initial stiffness,peak load,fracture displacement,and absorbed energy)obtained by finite element calculation and the test values was within 15%.These results demonstrated that the calibration elastic-plastic degradation model of 40Cr steel can predict the cutoff of the shear pin.展开更多
The accurate contact parameters of American ginseng seed particles are the basis for establishing the discrete element simulation model of American ginseng seeds.The parameters of American ginseng seeds were calibrate...The accurate contact parameters of American ginseng seed particles are the basis for establishing the discrete element simulation model of American ginseng seeds.The parameters of American ginseng seeds were calibrated by combining the physical tests and simulation tests together.The basic physical parameters,contact parameters and repose angle of sprouted American ginseng seeds were determined by physical tests.The simulation parameters were significantly screened by conducting the Plackett-Burman test.Meanwhile,it was determined that the collision recovery coefficient,static friction coefficient and rolling friction coefficient of interspecific contact parameters have significant influences on the repose angle of the simulation test.By the steepest climb test,the optimal interval for the value of the significance parameter was determined.Subsequently,the second-order regression equation between contact parameters and the repose angle was established,the regression equation was optimized and solved,and the best combination of simulation parameters was determined.The collision recovery coefficient between sprouted American ginseng seeds was 0.346,the static friction coefficient was 0.769,and the rolling friction coefficient was 0.490.By the calibrated seed group of American ginseng for discrete element simulation test,the average repose value angle was 38.80°,and the relative error with the measured repose angle was 0.733%.The results revealed that the simulation parameters of American ginseng seeds were reliable,which can provide a basis for the design and performance optimization of American ginseng seed-metering device in the later stage.展开更多
The differential evolution(DE)algorithm was deployed to calibrate microparameters of the DEM cohesive granular material.4 macroparameters,namely,uniaxial compressive strength,direct tensile strength,Young’s modulus a...The differential evolution(DE)algorithm was deployed to calibrate microparameters of the DEM cohesive granular material.4 macroparameters,namely,uniaxial compressive strength,direct tensile strength,Young’s modulus and Poisson’s ratio,can be calibrated to high accuracy.The best calibration accuracy could reach the sum of relative errors RE_(sum)<0.1%.Most calibrations can be achieved with RE_(sum)<5%within hours or RE_(sum)<1%within 2 days.Based on the calibrated results,microparameters uniqueness analysis was carried out to reveal the correlation between microparameters and the macroscopic mechanical behaviour of material:(1)microparameters effective modulus,tensile strength and normal-to-shear stiffness ratio control the elastic behaviour and stable crack growth,(2)microparameters cohesion and friction angles present a negative linear correlation that controls the axial strain and lateral strain prior to the peak stress,and(3)microparameters friction coefficient controls shear crack friction and slip mainly refers to the unstable crack behaviour.Consideration of more macroparameters to regulate the material mechanical behaviour that is dominated by shear crack and slip motion is highlighted for future study.The DE calibration method is expected to serve as an alternative method to calibrate the DEM cohesive granular material to its peak strength.展开更多
The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibratio...The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.展开更多
Parameter calibration is an important part of hydrological simulation and affects the final simulation results.In this paper,we introduce heuristic optimization algorithms,genetic algorithm(GA)to cope with the complex...Parameter calibration is an important part of hydrological simulation and affects the final simulation results.In this paper,we introduce heuristic optimization algorithms,genetic algorithm(GA)to cope with the complexity of the parameter calibration problem,and use particle swarm optimization algorithm(PsO)as a comparison.For large-scale hydrological simulations,we use a multilevel parallel parameter calibration framework to make full use of processor resources,and accelerate the process of solving high-dimensional parameter calibration.Further,we test and apply the experiments on domestic supercomputers.The results of parameter calibration with GA and PSO can basically reach the ideal value of 0.65 and above,with PSO achieving a speedup of 58.52 on TianHe-2 supercomputer.The experimental results indicate that using a parallel implementation on multicore CPUs makes high-dimensional parameter calibration in large-scale hydrological simulation possible.Moreover,our comparison of the two algorithms shows that the GA obtains better calibration results,and the PSO has a more pronounced acceleration effect.展开更多
To simulate the bending behavior of wheat straw,a flexible straw model was developed based on the Hertz-Mindlin with bonding model using discrete element method.The proposed model was constructed by bonding straw unit...To simulate the bending behavior of wheat straw,a flexible straw model was developed based on the Hertz-Mindlin with bonding model using discrete element method.The proposed model was constructed by bonding straw units(filled by multi-spherical method)through parallel bonding keys.By means of a three-point bending test,single-factor sensitivity analysis and calibration of bonding parameters were performed.Results showed that elastic modulus of the flexible straw enhanced with the increase of bonded disk radius,normal stiffness per unit area and shear stiffness per unit area.The three bonding parameters were respectively calibrated to be 2.11 mm,9.48×10^(9)N/m^(3)and 4.67×10^(9)N/m^(3) by solving the regression equation developed from Box-Behnken design.The simulated elastic modulus(in terms of those three calibrated parameters)exhibited 4.20%difference with the measured one.It proved that the flexible straw could accurately demonstrate bending property of the wheat straw.This would not only help to improve accuracy in simulating wheat straw,but also provide references for flexible straw modeling and parameters calibration of other crops.展开更多
Some approaches to measure parallel 6-degree of freedom platform's posturestatically and to calibrate the platform's actual structural parameters by measuring a series of theplatform's varying postures are...Some approaches to measure parallel 6-degree of freedom platform's posturestatically and to calibrate the platform's actual structural parameters by measuring a series of theplatform's varying postures are studied. In the case where high posture accuracy is requiredrelatively, to obtain the platform's actual structural parameters is very important. Threedimensions measurement with 2 theodolites are used to obtain the platform's postures statically andNewton iterative method is adopted to calibrate structural parameters. Some measures taken in themeasurement and the calibration are discussed in detail. And the experiment results of theplatform's posture control before and after the calibration are given. The results show that theplatform's posture control accuracy after the calibration is improved notably.展开更多
The existing discrete element model of wheat plants lacks the glume,which hinders the simulation of the entire threshing process.To address this issue,this paper takes wheat at the harvest stage as the research object...The existing discrete element model of wheat plants lacks the glume,which hinders the simulation of the entire threshing process.To address this issue,this paper takes wheat at the harvest stage as the research object and constructs a complete discrete element model of wheat plants with glumes based on the Hertz-Mindlin with bonding model in the EDEM simulation software.The parameter calibration of wheat glumes discrete element model is studied through collision bounce experiments,slope experiments,and accumulation experiments.The results show that the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and steel are 0.488,0.625,and 0.048,respectively,and the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and glume are 0.232,0.966,and 0.059,respectively.The relative errors between the simulation results and the measured values are less than 5%,and the calibration parameters are effective.Based on the structural parameters of the self-developed experiment-bed of tangential axial-flow grain threshing device,a three-dimensional model of the wheat threshing device is established to simulate the whole threshing process of the complete wheat plant,and the bench-scale experiments are carried out with the non-threshing rate as the performance index.The results indicate that the model can completely simulate the separation process of glume and grain and the movement law of different grains,and the relative error of non-threshing rate between the simulation experiments and bench-scale experiments is 4.36%.This further demonstrates that the proposed model can provide a reference for the wheat threshing process research and device performance optimization design.展开更多
The parameter X of the Muskingum method is a physical parameter that reflects the flood peak attenuation and hydrograph shape flattening of a diffusion wave in motion. In this paper, the historic process that hydrolog...The parameter X of the Muskingum method is a physical parameter that reflects the flood peak attenuation and hydrograph shape flattening of a diffusion wave in motion. In this paper, the historic process that hydrologists have undergone to find a physical explanation of this parameter is briefly discussed. Based on the fact that the Muskingum method is the second-order accuracy difference solution to the diffusion wave equation, its numerical stability condition is analyzed, and a conclusion is drawn： X ≤ 0.5 is the uniform condition satisfying the demands for its physical meaning and numerical stability. It is also pointed out that the methods that regard the sum of squares of differences between the calculated and observed discharges or stages as the objective function and the routing coefficients C0, C1 and C2 of the Muskingum method as the optimization parameters cannot guarantee the physical meaning of X.展开更多
Since its introduction,discontinuous deformation analysis(DDA)has been widely used in different areas of rock mechanics.By dividing large blocks into subblocks and introducing artificial joints,DDA can be applied to r...Since its introduction,discontinuous deformation analysis(DDA)has been widely used in different areas of rock mechanics.By dividing large blocks into subblocks and introducing artificial joints,DDA can be applied to rock fracture simulation.However,parameter calibration,a fundamental issue in discontinuum methods,has not received enough attention in DDA.In this study,the parameter calibration of DDA for intact rock is carefully studied.To this end,a subblock DDA with Voronoi tessellation is presented first.Then,a modified contact constitutive law is introduced,in which the tensile and shear meso-strengths are modified to be independent of the bond lengths.This improvement can prevent the unjustified preferential failure of short edges.A method for imposing confining pressure is also introduced.Thereafter,sensitivity analysis is performed to investigate the influence of the calculated parameters and meso-parameters on the mechanical properties of modeled rock.Based on the sensitivity analysis,a unified calibration procedure is suggested for both cases with and without confining pressure.Finally,the calibration procedure is applied to two examples,including a biaxial compression test.The results show that the proposed Voronoi-based DDA can simulate rock fracture with and without confining pressure very well after careful parameter calibration.展开更多
Sunflower(Helianthus annuus L.)is one of the four major oil crops in the world and has high economic value.However,the lack of discrete element method(DEM)models and parameters for sunflower seeds hinders the applicat...Sunflower(Helianthus annuus L.)is one of the four major oil crops in the world and has high economic value.However,the lack of discrete element method(DEM)models and parameters for sunflower seeds hinders the application of DEM for computer simulation in the key working processes of sunflower seed sowing and harvesting.The present study was conducted on two varieties of sunflower,and the DEM model of sunflower seeds was established by using 3D scanning technology based on the distribution of triaxial dimensions and volumes of the geometric model of sunflower seeds.Similarly,the physical characteristics parameters of sunflower seeds were determined by physical tests and the simulation parameters were screened for significance based on the Plackett-Burman test.Our results show that the coefficient of static friction between sunflower seeds and the coefficient of rolling friction have significant effects on the repose angle of the simulation test.Furthermore,the optimal range of the significance parameters was further determined by the steepest climb test,and the second-order regression model of the significance parameters and the repose angle was obtained according to the Box-Behnken design test and Response Surface Methodology(RSM),with the repose angle measured by the physical test as the optimized target value to obtain the optimal parameter combination.Finally,a two-sample t-test for the repose angle of the physical test and the repose angle of the simulation test yielded P>0.05.Our results confirms that the repose angle obtained from simulation is not significantly different from the physical test value,and the relative errors between the repose angle of the simulation test and the physical test are 1.43%and 0.40%,respectively,for the optimal combination of parameters.Based on these results it can be concluded that the optimal parameters obtained from the calibration can be used for DEM simulation experiments related to the sunflower seed sowing and harvesting process.展开更多
In order to establish an accurate discrete element model of alfalfa seeds,real physical experiments were combined with simulation experiments,and the contact parameters of alfalfa seeds were calibrated using the repos...In order to establish an accurate discrete element model of alfalfa seeds,real physical experiments were combined with simulation experiments,and the contact parameters of alfalfa seeds were calibrated using the repose angle of alfalfa seeds as the response value.Some intrinsic parameters(thousand grain weight,triaxial size,density)and contact parameters(static friction coefficient,rolling friction coefficient)of alfalfa seeds were obtained through physical experiments,and a spherical particle model was established.Through the Plackett Burman experiment,the static friction coefficient between alfalfa seeds,the rolling friction coefficient between alfalfa seeds,and the static friction coefficient between alfalfa seeds and ABS plastic were determined to have a significant impact on the experiment.The steepest climb test is used to narrow down the selection range of the optimal parameters,and the box Behnken test is used to obtain the quadratic regression equation of the repose angle.The optimal parameter combination was obtained with the objective of minimizing the repose angle error:the static friction coefficient between alfalfa seeds and alfalfa seeds was 0.418,the rolling friction coefficient between alfalfa seeds and alfalfa seeds was 0.086,and the static friction coefficient between alfalfa seeds and ABS plastic was 0.471.The repose angle and mass flow rate experiments show that the model is effective and reliable.展开更多
Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional cali...Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional calibration of material parameters often relies on a trial-and-error approach,in which the parameters are manually adjusted until the corresponding finite element model results in a response matching the experimental global response.The parameter estimates are often subjective.To address this issue,in this paper we treat the identification of material parameters as an optimization problem and introduce the particle swarm optimization(PSO)algorithm as the optimization approach.We provide material parameters of two uncoupled ductile fracture models—the Rice and Tracey void growth model(RT-VGM)and the micro-mechanical void growth model(MM-VGM),and a coupled model—the gurson-Tvergaard-Needleman(GTN)model for ASTM A36,A572 Gr.50,and A992 structural steels using an automated PSO method.By minimizing the difference between the experimental results and finite element simulations of the load-displacement curves for a set of tests of circumferentially notched tensile(CNT)bars,the calibration procedure automatically determines the parameters of the strain hardening law as well as the uncoupled models and the coupled GTN constitutive model.Validation studies show accurate prediction of the load-displacement response and ductile fracture initiation in V-notch specimens,and confirm the PSO algorithm as an effective and robust algorithm for seeking ductile fracture model parameters.PSO has excellent potential for identifying other fracture models(e.g.,shear modified GTN)with many parameters that can give rise to more accurate predictions of ductile fracture.Limitations of the PSO algorithm and the current calibrated ductile fracture models are also discussed in this paper.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.12272247)National Key Project(Grant No.GJXM92579)Major Research and Development Project of Metallurgical Corporation of China Ltd.in the Non-Steel Field(Grant No.2021-5).
文摘The tensile-shear interactive damage(TSID)model is a novel and powerful constitutive model for rock-like materials.This study proposes a methodology to calibrate the TSID model parameters to simulate sandstone.The basic parameters of sandstone are determined through a series of static and dynamic tests,including uniaxial compression,Brazilian disc,triaxial compression under varying confining pressures,hydrostatic compression,and dynamic compression and tensile tests with a split Hopkinson pressure bar.Based on the sandstone test results from this study and previous research,a step-by-step procedure for parameter calibration is outlined,which accounts for the categories of the strength surface,equation of state(EOS),strain rate effect,and damage.The calibrated parameters are verified through numerical tests that correspond to the experimental loading conditions.Consistency between numerical results and experimental data indicates the precision and reliability of the calibrated parameters.The methodology presented in this study is scientifically sound,straightforward,and essential for improving the TSID model.Furthermore,it has the potential to contribute to other rock constitutive models,particularly new user-defined models.
基金We would like to express our acknowledgements to the Fund of postgraduate training and innovation project of Jiangsu Province(NO.SJKY19_0969).
文摘For the challenge of parameter calibration in the process of SWMM(storm water management model)model application,we use particle Swarm Optimization(PSO)and Sequence Quadratic Programming(SQP)in combination to calibrate the parameters and get the optimal parameter combination in this research.Then,we compare and analyze the simulation result with the other two respectively using initial parameters and parameters obtained by PSO algorithm calibration alone.The result shows that the calibration result of PSO-SQP combined algorithm has the highest accuracy and shows highly consistent with the actual situation,which provides a scientific and effective new idea for parameter calibration of SWMM model,moreover,has practical guidance for flood control and disaster mitigation.
文摘Accurately simulating the crushing process of ore particles in a semi-autogenous grinding mill (SAG mill) is quite challenging. This study utilizes the discrete element method (DEM) to construct a breakage model for ore particles. Calibration of the discrete element basic parameters and Tavares breakage model parameters is conducted based on angle of repose (AoR) tests and single-particle impact tests. 3D scanning is employed to capture the morphology of the ore for particle modeling. On this basis, a discrete element breakage model for ore particles is built for single-particle impact simulations and validated through testing to determine the calibrated model parameters. The results indicate that the AoR angles and stacking shapes from the simulation and tests are highly similar, with a relative error of about 0.19%. The similarity in crushing outcomes and quantitative values between single-particle impact simulations and tests preliminary validates the reliability of the calibration method and the applicability of the Tavares breakage model, successfully determining a group of model parameters suitable for simulating ore particle crushing processes. This study lays the groundwork for utilizing DEM to simulate the visualization of ore particle crushing.
基金supported by the China Agricultural Research System of MOF and MARA(NO:CARS-12).
文摘To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River,which causes clogging of the fertilizer discharger and leads to a reduction in the uniformity and stability of fertilizer discharge,research on the crushing mechanism of caking compound fertilizer was performed.Considering that it is difficult to measure the bonding force between caking fertilizer particles directly,a simulation model of caking composite fertilizer was established with the bonding model in EDEM discrete element software.To decrease error between the simulation and physical test results,the normal contact stiffness,tangential contact stiffness,critical normal stress,critical tangential stress,bonding radius,and other parameters of the bonding model of caking composite fertilizer were calibrated.The three-dimensional structure of the caking composite fertilizer was obtained via three-dimensional scanning,the critical crushing displacement and critical crushing force of the caking composite fertilizer were measured via compression testing with a mass spectrometer,and the optimal parameter combination of the bonding model was determined via EDEM discrete element simulation of the Plackett-Burman test,steepest ascent test,and Box-Behnken test.The results of the simulated compression tests under the optimal parameter combination show that the relative errors of the critical crushing displacement and critical crushing force with respect to the physical test results were 0.296%and 0.343%,respectively.Using the crushing rate of caking compound fertilizer as an evaluation index,the feasibility of the calibrated parameters was verified for a four-head spiral two-row fertilizer discharger installed in a direct seeding machine for oilseed rape.The results show that the relative errors of the caking fertilizer crushing rates from the simulation relative to those of the bench and field tests were 5.81%and 5.06%,respectively,indicating that the calibration parameters of the discrete element model were accurate and could be used for parameter analysis of caking fertilizer with a discrete element model.These results can provide a reference for the structural optimization of fertilizer discharger crushing of caking fertilizer of direct seeding machine for oilseed rape.
基金supported by the National Natural Science Foundation of China(Grant Nos.52265041 and 31901417)the assistance provided by the Xinjiang Key Laboratory of Intelligent Agricultural Equipment.
文摘Understanding the biomechanical properties of safflowers is essential for appropriately designing harvesting machinery and optimizing the harvesting process.Safflower is a flexible crop that lacks a basis for relevant simulation parameters,which causes difficulties in designing harvesting machinery.In this study,a calibration method for safflowers was proposed.First,a discrete element model was established by measuring the intrinsic parameters of a safflower,such as its geometric parameters,density,Poisson’s ratio,and modulus of elasticity.Second,the contact and bonding parameters were calibrated using a combination of physical and simulation tests.In the contact parameter tests,the Hertz-Mindlin(no-slip)model was implemented for the stacking angle tests conducted regarding the safflower filament.A regular two-level factorial design was used to determine the important factors and perform the steepest climb test.Moreover,the Box-Behnken design was adopted to obtain the optimal contact parameters.In the bonding parameter tests,the Hertz-Mindlin model with bonding contact was applied for the safflower shear simulation tests;moreover,the optimum bonding parameters were obtained through the central composite design test.The results demonstrated that the relative errors between the simulated and measured stacking angles and maximum shear were 3.19%and 5.29%,respectively.As a result,the safflower simulation parameters were accurately calibrated,providing a reference for appropriately setting the simulation parameters and designing key mechanical components.
基金supported by the Autonomous Region Key R&D Program of Xinjiang,China(Grant No.2022B02046).
文摘To improve the survival rate of larvae during material separation after biotransformation of existing residual film mixtures of Protaetia brevitarsis larvae,this paper adopts the method of combining physical test and EDEM simulation test,and selects Hertz Mindlin with JKR contact model to calibrate the discrete element simulation contact parameters of the Protaetia brevitarsis larvae and the frass mixture.First,the cylinder lifting method was used to determine the actual repose angle of the mixture of larvae and frass.The collision recovery coefficients between larvae-frass and steel,static friction coefficient,kinetic friction coefficient and the collision recovery coefficient between larvae were measured through physical tests such as the inclined plane method.The Plackett-Burman test was then used to screen out the factors that have a significant impact on the repose angle:Poisson’s ratio of frass,frass-frass rolling friction coefficient,frass JKR surface energy,frass-larvae JKR surface energy.The optimal value intervals of four significant factors were determined based on the steepest climb test,Based on the Box-Behnken response surface analysis test,the second-order regression model between the repose angle and four significant factors was determined,and variance and interaction effects were analyzed.And with the actual repose angle as the goal,the significant factors were optimized and the optimal parameter combination of the four significant factors was determined.The simulation test of material repose angle and screening was carried out with the optimal parameter combination,and compared with the physical test.It was found that the maximum relative errors of the two tests were 1.48%and 3.79%respectively,indicating that the calibrated parameter values are true and reliable,It can provide a reference for the discrete element simulation of the transportation and separation of the Protaetia brevitarsis larvae-frass mixture.
基金Supported by National Natural Science Foundation of China(Grant Nos.52202431,52172353)Talent Fund of Beijing Jiaotong University of China(Grant No.2024XKRC044).
文摘Due to the different microstructures caused by the heat source effect,welding joints exhibit significant differences in mechanical properties compared to the base material.Precise characterization of the constitutive characteristics of the welded joint requires a large number of repetitive experiments,which are costly,inefficient,and have limited accuracy improvements.This paper proposes an integrated experimental-simulation-based inverse calibration method,which establishes a calibration optimization problem based on the corresponding constitutive model and a finite element calculation model built by the distribution of hardness in the weldment.Using the global tensile force-displacement curve of the MIG-welded 6005A-T6 aluminum alloy specimen and the experimental data of local deformation with time change obtained from DIC(Digital Image Correlation),the parameters involved in the constitutive models are optimized accordingly.This method can directly obtain the constitutive characteristics of the weldment under conditions of limited experiments and insufficient data.Additionally,the adaptability of the constitutive model to the calibration method and the influence of optimization results are discussed and analyzed.The results indicate that the global force-displacement response of the non-saturated Ramberg-Osgood(R-O)model is in the best agreement with that of the experimental data,and the energy error is only 2.62%,followed by the MPL model,while the saturation-based Voce model shows the largest simulation error in terms of the presented object.Furthermore,the simulation results of R-O,Voce,and MPL models in the local area are far superior to traditional fitting methods.
基金The Research Start-up Fund for Talents Introduction of Huaiyin Institute of Technology(Grant No.Z301B23517).
文摘The shear pin of the friction pendulum bearing(FPB)can be made of 40Cr steel.In conceptual design,the optimal cut-off point of the shear pin is predetermined,guiding the design of bridges isolated by FPBs to maximize their isolation performance.Current researches on the shear pins are mainly based on linear elastic models,neglecting their plasticity,damage,and fracture mechanical properties.To accurately predict its cutoff behavior,the elastic-plastic degradationmodel of 40Cr steel is indeed calibrated.For this purpose,the Ramberg-Osgoodmodel,the Bao-Wierzbicki damage initiation criterion,and the linear damage evolution criterion were selected to develop the elastic-plastic degradation model of 40Cr.Subsequently,parameter calibration of this model was performed through uniaxial tensile tests on two sets of six smooth,round bars with different diameters.Following this,finite element simulations were conducted for the pure shear test of grade 10.9 high-strength bolts made of 40Cr steel,aiming to verify the elasticplastic degradation model.The results showed that the failure modes and force-displacement curves simulated by the finite element method were in good agreement with the test results.Moreover,the error between the primary characteristic parameters(initial stiffness,peak load,fracture displacement,and absorbed energy)obtained by finite element calculation and the test values was within 15%.These results demonstrated that the calibration elastic-plastic degradation model of 40Cr steel can predict the cutoff of the shear pin.
基金the National Natural Science Foundation of China(51775290)Natural Science Foundation of Shandong Province(ZR202111230084)+5 种基金the Shandong Provincial Science and Technology SMEs Innovation Capacity Improvement Project(2021TSGC1428)the Key R&D Plan of Shandong Province(2019GNC106056)the Key R&D Plan of Shandong Province(2017NC212006)the Qingdao Minsheng Science and Technology Plan(22-3-7-xdny-17-nsh)the Qingdao Minsheng Science and Technology Plan(173352nsh)the Chinese Herbal Medicine Innovation Team of Modern Agricultural Industrial Technology System in Shandong Province(SDAIT-20-05).
文摘The accurate contact parameters of American ginseng seed particles are the basis for establishing the discrete element simulation model of American ginseng seeds.The parameters of American ginseng seeds were calibrated by combining the physical tests and simulation tests together.The basic physical parameters,contact parameters and repose angle of sprouted American ginseng seeds were determined by physical tests.The simulation parameters were significantly screened by conducting the Plackett-Burman test.Meanwhile,it was determined that the collision recovery coefficient,static friction coefficient and rolling friction coefficient of interspecific contact parameters have significant influences on the repose angle of the simulation test.By the steepest climb test,the optimal interval for the value of the significance parameter was determined.Subsequently,the second-order regression equation between contact parameters and the repose angle was established,the regression equation was optimized and solved,and the best combination of simulation parameters was determined.The collision recovery coefficient between sprouted American ginseng seeds was 0.346,the static friction coefficient was 0.769,and the rolling friction coefficient was 0.490.By the calibrated seed group of American ginseng for discrete element simulation test,the average repose value angle was 38.80°,and the relative error with the measured repose angle was 0.733%.The results revealed that the simulation parameters of American ginseng seeds were reliable,which can provide a basis for the design and performance optimization of American ginseng seed-metering device in the later stage.
文摘The differential evolution(DE)algorithm was deployed to calibrate microparameters of the DEM cohesive granular material.4 macroparameters,namely,uniaxial compressive strength,direct tensile strength,Young’s modulus and Poisson’s ratio,can be calibrated to high accuracy.The best calibration accuracy could reach the sum of relative errors RE_(sum)<0.1%.Most calibrations can be achieved with RE_(sum)<5%within hours or RE_(sum)<1%within 2 days.Based on the calibrated results,microparameters uniqueness analysis was carried out to reveal the correlation between microparameters and the macroscopic mechanical behaviour of material:(1)microparameters effective modulus,tensile strength and normal-to-shear stiffness ratio control the elastic behaviour and stable crack growth,(2)microparameters cohesion and friction angles present a negative linear correlation that controls the axial strain and lateral strain prior to the peak stress,and(3)microparameters friction coefficient controls shear crack friction and slip mainly refers to the unstable crack behaviour.Consideration of more macroparameters to regulate the material mechanical behaviour that is dominated by shear crack and slip motion is highlighted for future study.The DE calibration method is expected to serve as an alternative method to calibrate the DEM cohesive granular material to its peak strength.
基金Supported by National Natural Science Foundation of China(Grant Nos.51105092,61403106)International Science and Technology Cooperation Program of China(Grant No.2014DFR50250)the 111 Project,China(Grant No.B07018)
文摘The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.
基金Key R&D Program of China No.2021YFB0300202&2021YFB0300200Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)No.FRF-IDRY-20-036.
文摘Parameter calibration is an important part of hydrological simulation and affects the final simulation results.In this paper,we introduce heuristic optimization algorithms,genetic algorithm(GA)to cope with the complexity of the parameter calibration problem,and use particle swarm optimization algorithm(PsO)as a comparison.For large-scale hydrological simulations,we use a multilevel parallel parameter calibration framework to make full use of processor resources,and accelerate the process of solving high-dimensional parameter calibration.Further,we test and apply the experiments on domestic supercomputers.The results of parameter calibration with GA and PSO can basically reach the ideal value of 0.65 and above,with PSO achieving a speedup of 58.52 on TianHe-2 supercomputer.The experimental results indicate that using a parallel implementation on multicore CPUs makes high-dimensional parameter calibration in large-scale hydrological simulation possible.Moreover,our comparison of the two algorithms shows that the GA obtains better calibration results,and the PSO has a more pronounced acceleration effect.
基金This research was financially supported by Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130204110020).
文摘To simulate the bending behavior of wheat straw,a flexible straw model was developed based on the Hertz-Mindlin with bonding model using discrete element method.The proposed model was constructed by bonding straw units(filled by multi-spherical method)through parallel bonding keys.By means of a three-point bending test,single-factor sensitivity analysis and calibration of bonding parameters were performed.Results showed that elastic modulus of the flexible straw enhanced with the increase of bonded disk radius,normal stiffness per unit area and shear stiffness per unit area.The three bonding parameters were respectively calibrated to be 2.11 mm,9.48×10^(9)N/m^(3)and 4.67×10^(9)N/m^(3) by solving the regression equation developed from Box-Behnken design.The simulated elastic modulus(in terms of those three calibrated parameters)exhibited 4.20%difference with the measured one.It proved that the flexible straw could accurately demonstrate bending property of the wheat straw.This would not only help to improve accuracy in simulating wheat straw,but also provide references for flexible straw modeling and parameters calibration of other crops.
基金This project is supported by National Defense Science and Technology Multi-vocation Foundation in Advance Research of China(No. 97J465JW0408).
文摘Some approaches to measure parallel 6-degree of freedom platform's posturestatically and to calibrate the platform's actual structural parameters by measuring a series of theplatform's varying postures are studied. In the case where high posture accuracy is requiredrelatively, to obtain the platform's actual structural parameters is very important. Threedimensions measurement with 2 theodolites are used to obtain the platform's postures statically andNewton iterative method is adopted to calibrate structural parameters. Some measures taken in themeasurement and the calibration are discussed in detail. And the experiment results of theplatform's posture control before and after the calibration are given. The results show that theplatform's posture control accuracy after the calibration is improved notably.
基金supported by the Major Scientific and Technological Project of Henan Province(Grant No.231100110200)the Open Subject of State Key Laboratory of Intelligent Agricultural Power Equipment(Grant No.SKLIAPE2023015)the Open Subject of Key Laboratory of Agricultural Equipment Technology for Hilly and Mountainous Areas(Grant No.2023KLOP03).
文摘The existing discrete element model of wheat plants lacks the glume,which hinders the simulation of the entire threshing process.To address this issue,this paper takes wheat at the harvest stage as the research object and constructs a complete discrete element model of wheat plants with glumes based on the Hertz-Mindlin with bonding model in the EDEM simulation software.The parameter calibration of wheat glumes discrete element model is studied through collision bounce experiments,slope experiments,and accumulation experiments.The results show that the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and steel are 0.488,0.625,and 0.048,respectively,and the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and glume are 0.232,0.966,and 0.059,respectively.The relative errors between the simulation results and the measured values are less than 5%,and the calibration parameters are effective.Based on the structural parameters of the self-developed experiment-bed of tangential axial-flow grain threshing device,a three-dimensional model of the wheat threshing device is established to simulate the whole threshing process of the complete wheat plant,and the bench-scale experiments are carried out with the non-threshing rate as the performance index.The results indicate that the model can completely simulate the separation process of glume and grain and the movement law of different grains,and the relative error of non-threshing rate between the simulation experiments and bench-scale experiments is 4.36%.This further demonstrates that the proposed model can provide a reference for the wheat threshing process research and device performance optimization design.
基金supported by the Scientific and Technological Basic Research Grant of the Ministry of Science and Technology of China (Grant No. 2007FY140900)the Public Welfare Industry Special Fund Project of the Ministry of Water Resources of China (Grant No. 200801033)
文摘The parameter X of the Muskingum method is a physical parameter that reflects the flood peak attenuation and hydrograph shape flattening of a diffusion wave in motion. In this paper, the historic process that hydrologists have undergone to find a physical explanation of this parameter is briefly discussed. Based on the fact that the Muskingum method is the second-order accuracy difference solution to the diffusion wave equation, its numerical stability condition is analyzed, and a conclusion is drawn： X ≤ 0.5 is the uniform condition satisfying the demands for its physical meaning and numerical stability. It is also pointed out that the methods that regard the sum of squares of differences between the calculated and observed discharges or stages as the objective function and the routing coefficients C0, C1 and C2 of the Muskingum method as the optimization parameters cannot guarantee the physical meaning of X.
基金The authors would like to thank the National Natural Science Foundation of China(Grant Nos.51879184 and 52079091)for funding this work.
文摘Since its introduction,discontinuous deformation analysis(DDA)has been widely used in different areas of rock mechanics.By dividing large blocks into subblocks and introducing artificial joints,DDA can be applied to rock fracture simulation.However,parameter calibration,a fundamental issue in discontinuum methods,has not received enough attention in DDA.In this study,the parameter calibration of DDA for intact rock is carefully studied.To this end,a subblock DDA with Voronoi tessellation is presented first.Then,a modified contact constitutive law is introduced,in which the tensile and shear meso-strengths are modified to be independent of the bond lengths.This improvement can prevent the unjustified preferential failure of short edges.A method for imposing confining pressure is also introduced.Thereafter,sensitivity analysis is performed to investigate the influence of the calculated parameters and meso-parameters on the mechanical properties of modeled rock.Based on the sensitivity analysis,a unified calibration procedure is suggested for both cases with and without confining pressure.Finally,the calibration procedure is applied to two examples,including a biaxial compression test.The results show that the proposed Voronoi-based DDA can simulate rock fracture with and without confining pressure very well after careful parameter calibration.
基金funding for this study from Nature Science Foundation of China,Grant No.(51865047).
文摘Sunflower(Helianthus annuus L.)is one of the four major oil crops in the world and has high economic value.However,the lack of discrete element method(DEM)models and parameters for sunflower seeds hinders the application of DEM for computer simulation in the key working processes of sunflower seed sowing and harvesting.The present study was conducted on two varieties of sunflower,and the DEM model of sunflower seeds was established by using 3D scanning technology based on the distribution of triaxial dimensions and volumes of the geometric model of sunflower seeds.Similarly,the physical characteristics parameters of sunflower seeds were determined by physical tests and the simulation parameters were screened for significance based on the Plackett-Burman test.Our results show that the coefficient of static friction between sunflower seeds and the coefficient of rolling friction have significant effects on the repose angle of the simulation test.Furthermore,the optimal range of the significance parameters was further determined by the steepest climb test,and the second-order regression model of the significance parameters and the repose angle was obtained according to the Box-Behnken design test and Response Surface Methodology(RSM),with the repose angle measured by the physical test as the optimized target value to obtain the optimal parameter combination.Finally,a two-sample t-test for the repose angle of the physical test and the repose angle of the simulation test yielded P>0.05.Our results confirms that the repose angle obtained from simulation is not significantly different from the physical test value,and the relative errors between the repose angle of the simulation test and the physical test are 1.43%and 0.40%,respectively,for the optimal combination of parameters.Based on these results it can be concluded that the optimal parameters obtained from the calibration can be used for DEM simulation experiments related to the sunflower seed sowing and harvesting process.
基金financially sponsored by the National Natural Science Foundation of China(Grant No.5227051664)Natural Science Foundation of Shandong Province(Grant No.ZR202111230084)+2 种基金Key R&D Program of Shandong Province,China(Grant No.2019GNC106056)Taishan Scholar Youth Expert Project,the Chinese Herbal Medicine Innovation Team of Modern Agricultural Industrial Technology System in Shandong Province(Grant No.SDAIT-20-05)Qingdao Agricultural University-Technical Service Team of Special Industries(Grant No.QAU2022QY009).
文摘In order to establish an accurate discrete element model of alfalfa seeds,real physical experiments were combined with simulation experiments,and the contact parameters of alfalfa seeds were calibrated using the repose angle of alfalfa seeds as the response value.Some intrinsic parameters(thousand grain weight,triaxial size,density)and contact parameters(static friction coefficient,rolling friction coefficient)of alfalfa seeds were obtained through physical experiments,and a spherical particle model was established.Through the Plackett Burman experiment,the static friction coefficient between alfalfa seeds,the rolling friction coefficient between alfalfa seeds,and the static friction coefficient between alfalfa seeds and ABS plastic were determined to have a significant impact on the experiment.The steepest climb test is used to narrow down the selection range of the optimal parameters,and the box Behnken test is used to obtain the quadratic regression equation of the repose angle.The optimal parameter combination was obtained with the objective of minimizing the repose angle error:the static friction coefficient between alfalfa seeds and alfalfa seeds was 0.418,the rolling friction coefficient between alfalfa seeds and alfalfa seeds was 0.086,and the static friction coefficient between alfalfa seeds and ABS plastic was 0.471.The repose angle and mass flow rate experiments show that the model is effective and reliable.
基金the National Natural Science Foundation of China(No.51908416)the Shanghai Pujiang Program(No.19PJ1409500)the Fundamental Research Funds for the Central Universities,China。
文摘Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional calibration of material parameters often relies on a trial-and-error approach,in which the parameters are manually adjusted until the corresponding finite element model results in a response matching the experimental global response.The parameter estimates are often subjective.To address this issue,in this paper we treat the identification of material parameters as an optimization problem and introduce the particle swarm optimization(PSO)algorithm as the optimization approach.We provide material parameters of two uncoupled ductile fracture models—the Rice and Tracey void growth model(RT-VGM)and the micro-mechanical void growth model(MM-VGM),and a coupled model—the gurson-Tvergaard-Needleman(GTN)model for ASTM A36,A572 Gr.50,and A992 structural steels using an automated PSO method.By minimizing the difference between the experimental results and finite element simulations of the load-displacement curves for a set of tests of circumferentially notched tensile(CNT)bars,the calibration procedure automatically determines the parameters of the strain hardening law as well as the uncoupled models and the coupled GTN constitutive model.Validation studies show accurate prediction of the load-displacement response and ductile fracture initiation in V-notch specimens,and confirm the PSO algorithm as an effective and robust algorithm for seeking ductile fracture model parameters.PSO has excellent potential for identifying other fracture models(e.g.,shear modified GTN)with many parameters that can give rise to more accurate predictions of ductile fracture.Limitations of the PSO algorithm and the current calibrated ductile fracture models are also discussed in this paper.
