Numerical simulation is an effective approach in studying cutting mechanism.The widely used methods for cutting simulation include finite element analysis and molecular dynamics.However,there exist some intrinsic shor...Numerical simulation is an effective approach in studying cutting mechanism.The widely used methods for cutting simulation include finite element analysis and molecular dynamics.However,there exist some intrinsic shortcomings when using a mesh-based formulation,and the capable scale of molecular dynamics is extremely small.In contrast,smoothed particle hydrodynamics(SPH)is a candidate to combine the advantages of them.It is a particle method which is suitable for simulating the large deformation process,and is formulated based on continuum mechanics so that large scale problems can be handled in principle.As a result,SPH has also become a main way for the cutting simulation.Since some issues arise while using conventional SPH to handle solid materials,the total Lagrangian smoothed particle hydrodynamics(TLSPH)is developed.But instabilities would still occur during the cutting,which is a critical issue to resolve.This paper studies the effects of TLSPH settings and cutting model parameters on the numerical instability,as well as the chip formation process.Plastic deformation,stress field and cutting forces are analyzed as well.It shows that the hourglass coefficient,critical pairwise deformation and time step are three important parameters to control the stability of the simulation,and a strategy on how to adjust them is provided.展开更多
Extreme ultraviolet(EUV)light plays an important role in various fields such as material characterization and semiconductor manufacturing.It is also a potential approach in material fabrication at atomic and close-to-...Extreme ultraviolet(EUV)light plays an important role in various fields such as material characterization and semiconductor manufacturing.It is also a potential approach in material fabrication at atomic and close-to-atomic scales.However,the material removal mechanism has not yet been fully understood.This paper studies the interaction of a femtosecond EUV pulse with monocrystalline silicon using molecular dynamics(MD)coupled with a two-temperature model(TTM).The photoionization mechanism,an important process occurring at a short wavelength,is introduced to the simulation and the results are compared with those of the traditional model.Dynamical processes including photoionization,atom desorption,and laser-induced shockwave are discussed under various fluencies,and the possibility of single atomic layer removal is explored.Results show that photoionization and the corresponding bond breakage are the main reasons of atom desorption.The method developed can be further employed to investigate the interaction between high-energy photons and the material at moderate fluence.展开更多
基金supported by the National key Research and Development Program of China(No.2016YFB 1102203)the National Natural Science Foundation of China(No.61635008)the‘111’project by the State Administration of Foreign Experts Affairs and the Ministry of Education of China(Grant No.B07014).
文摘Numerical simulation is an effective approach in studying cutting mechanism.The widely used methods for cutting simulation include finite element analysis and molecular dynamics.However,there exist some intrinsic shortcomings when using a mesh-based formulation,and the capable scale of molecular dynamics is extremely small.In contrast,smoothed particle hydrodynamics(SPH)is a candidate to combine the advantages of them.It is a particle method which is suitable for simulating the large deformation process,and is formulated based on continuum mechanics so that large scale problems can be handled in principle.As a result,SPH has also become a main way for the cutting simulation.Since some issues arise while using conventional SPH to handle solid materials,the total Lagrangian smoothed particle hydrodynamics(TLSPH)is developed.But instabilities would still occur during the cutting,which is a critical issue to resolve.This paper studies the effects of TLSPH settings and cutting model parameters on the numerical instability,as well as the chip formation process.Plastic deformation,stress field and cutting forces are analyzed as well.It shows that the hourglass coefficient,critical pairwise deformation and time step are three important parameters to control the stability of the simulation,and a strategy on how to adjust them is provided.
基金supported financially by the National Natural Science Foundation(Grant No.52035009)the‘111’project of the State Administration of Foreign Experts Affairs and the Ministry of Education of China(Grant No.B07014).
文摘Extreme ultraviolet(EUV)light plays an important role in various fields such as material characterization and semiconductor manufacturing.It is also a potential approach in material fabrication at atomic and close-to-atomic scales.However,the material removal mechanism has not yet been fully understood.This paper studies the interaction of a femtosecond EUV pulse with monocrystalline silicon using molecular dynamics(MD)coupled with a two-temperature model(TTM).The photoionization mechanism,an important process occurring at a short wavelength,is introduced to the simulation and the results are compared with those of the traditional model.Dynamical processes including photoionization,atom desorption,and laser-induced shockwave are discussed under various fluencies,and the possibility of single atomic layer removal is explored.Results show that photoionization and the corresponding bond breakage are the main reasons of atom desorption.The method developed can be further employed to investigate the interaction between high-energy photons and the material at moderate fluence.
