In this paper an analytical study is carried out to examine the effectiveness of absorbing boundaries using dashpot. Validity of the absorbing boundary conditions suggested by Lysmer-Kuhle- meyer and White et al. is i...In this paper an analytical study is carried out to examine the effectiveness of absorbing boundaries using dashpot. Validity of the absorbing boundary conditions suggested by Lysmer-Kuhle- meyer and White et al. is investigated by adopting the solution of Miller and Pursey. The Miller and Pursey’s problem is then numerically simulated using the finite element method. The absorption ratios are calculated by comparing the displacements at the absorbing boundary to those at the free field without the absorbing boundary. The numerical verification is carried out through comparison of displacement at the boundary.展开更多
The dynamic dashpot models are widely used in EDEM commercial software.However,most dashpot models suffer from a serious numerical issue in calculating the granular chain because the denominator of damping force inclu...The dynamic dashpot models are widely used in EDEM commercial software.However,most dashpot models suffer from a serious numerical issue in calculating the granular chain because the denominator of damping force includes the initial impact velocity.Moreover,the existing dynamic dashpot models extended from the original Hertz contact law overestimated the contact stiffness in the elastoplastic contact phase.These two reasons above result in most dynamic dashpot models confronting some issues in calculating the multiple collision of the granular chain.Therefore,this investigation aims to propose a new composite dynamic dashpot model for the dynamic simulation of granular matters.First,the entire contact process is divided into three different phases:elastic,elastoplastic,and full plastic phases.The Hertz contact stiffness is still used in the elastic contact phase when the contact comes into the elastoplastic or full plastic phase.Hertz contact stiffness in the dynamic dashpot model is replaced by linearizing the contact stiffness from the Ma‐Liu(ML)model in each time step.Second,the whole contact behavior is treated as a linear mass‐spring‐damper model,and the damping factor is obtained by solving the single‐degree‐freedom underdamped vibration equation.The new dynamic dashpot model is proposed by combining the contact stiffnesses in different contact phases and corresponding damping factors,which not only removes the initial im-pact velocity from the denominator of damping force but also updates the contact stiffness based on the constitutive relation of the contact body when the contact comes into the elastoplastic or full plastic phase.Finally,a granular chain is treated as numerical examples to check the reasonability and effectiveness of the new dynamic dashpot model by comparing it to the experimental data.The simulation shows that the solitary waves obtained using the new dashpot model are more accurate than the dashpot model used in EDEM software.展开更多
文摘In this paper an analytical study is carried out to examine the effectiveness of absorbing boundaries using dashpot. Validity of the absorbing boundary conditions suggested by Lysmer-Kuhle- meyer and White et al. is investigated by adopting the solution of Miller and Pursey. The Miller and Pursey’s problem is then numerically simulated using the finite element method. The absorption ratios are calculated by comparing the displacements at the absorbing boundary to those at the free field without the absorbing boundary. The numerical verification is carried out through comparison of displacement at the boundary.
基金The National Natural Science Foundation of China,Grant/Award Numbers:1193200,12172004Boya Postdoctoral Fellowship of Peking University。
文摘The dynamic dashpot models are widely used in EDEM commercial software.However,most dashpot models suffer from a serious numerical issue in calculating the granular chain because the denominator of damping force includes the initial impact velocity.Moreover,the existing dynamic dashpot models extended from the original Hertz contact law overestimated the contact stiffness in the elastoplastic contact phase.These two reasons above result in most dynamic dashpot models confronting some issues in calculating the multiple collision of the granular chain.Therefore,this investigation aims to propose a new composite dynamic dashpot model for the dynamic simulation of granular matters.First,the entire contact process is divided into three different phases:elastic,elastoplastic,and full plastic phases.The Hertz contact stiffness is still used in the elastic contact phase when the contact comes into the elastoplastic or full plastic phase.Hertz contact stiffness in the dynamic dashpot model is replaced by linearizing the contact stiffness from the Ma‐Liu(ML)model in each time step.Second,the whole contact behavior is treated as a linear mass‐spring‐damper model,and the damping factor is obtained by solving the single‐degree‐freedom underdamped vibration equation.The new dynamic dashpot model is proposed by combining the contact stiffnesses in different contact phases and corresponding damping factors,which not only removes the initial im-pact velocity from the denominator of damping force but also updates the contact stiffness based on the constitutive relation of the contact body when the contact comes into the elastoplastic or full plastic phase.Finally,a granular chain is treated as numerical examples to check the reasonability and effectiveness of the new dynamic dashpot model by comparing it to the experimental data.The simulation shows that the solitary waves obtained using the new dashpot model are more accurate than the dashpot model used in EDEM software.
