This paper presents a new methodology for coarse-grained atomistic simulation of inelastic material behavior including phase transformations in ceramics and dislocation mediated plasticity in metals. The methodology c...This paper presents a new methodology for coarse-grained atomistic simulation of inelastic material behavior including phase transformations in ceramics and dislocation mediated plasticity in metals. The methodology combines an atomistic formulation of balance equations and a modified finite element method. With significantly fewer degrees of freedom than those of a fully atomistic model and without additional constitutive rules but the interatomic force field, the new coarse-grained （CG） method is shown to be feasible in predicting the nonlinear constitutive re- sponses of materials and also reproducing atomic-scale phenomena such as phase transformations （diamond --, 13-Sn） in silicon and dislocation nucleation and migration, formation of dislocation loops and stacking faults ribbons in single crystal nickel. Direct comparisons between CG and the corresponding full molecular dynamics （MD） simulations show that the present methodology is efficient and promising in modeling and simulation of inelastic material behavior without losing the essential atomistic features. The potential applications and the limitations of the CG method are also discussed.展开更多
Effect of boron on the microstructure and impact toughness in the coarse-grained heat-affected zone（CGHAZ）of two high strength low alloy steels,boron-free and boron-containing,was investigated by means of weld therm...Effect of boron on the microstructure and impact toughness in the coarse-grained heat-affected zone（CGHAZ）of two high strength low alloy steels,boron-free and boron-containing,was investigated by means of weld thermal simulation test.The result shows that,for the boron-free steel,a microstructure consisting of grain boundary ferrite degenerates pearlite and granular bainite for longer t8/5（the cooling time from 800 to 500 ℃）,while lath bainite for shorter t8/5.For the boron-containing steel,granular bainite is dominant for a wide range of t8/5.Continuous cooling transformation（CCT）study on the CGHAZ indicates that the transformation start temperature decreases by about 50-100℃under different t8/5,for the boron-containing steel compared with the boron-free steel.The presence of boron suppresses the nucleation of ferrite at prior austenite grain boundaries and hence enlarges the range of t8/5for granular bainite transformation.However,the addition of boron deteriorates the impact toughness of CGHAZ,which may be due to a markedly increased fraction of martensite-austenite（M-A）constituents and decreased fraction of high angle grain boundaries.展开更多
In this paper, a non-Newtonian third-grade blood in coronary and femoral arteries is simulated analytically and numerically. The blood is considered as the third- grade non-Newtonian fluid under the periodic body acce...In this paper, a non-Newtonian third-grade blood in coronary and femoral arteries is simulated analytically and numerically. The blood is considered as the third- grade non-Newtonian fluid under the periodic body acceleration motion and the pulsatile pressure gradient. The hybrid multi-step differential transformation method （Hybrid-Ms- DTM） and the Crank-Nicholson method （CNM） are used to solve the partial differential equation （PDE）, and a good agreement between them is observed in the results. The effects of the some physical parameters such as the amplitude, the lead angle, and the body acceleration frequency on the velocity and shear stress profiles are considered. The results show that increasing the amplitude, Ag, and reducing the lead angle of body acceleration, 9, make higher velocity profiles on the center line of both arteries. Also, the maximum wall shear stress increases when Ag increases.展开更多
In this short note we discuss the GM property of some special linear transformation pairs over infinite-dimensional vector spaces. In particular, it is proved that if R =- End（VD） is the endomorphism ring of an infi...In this short note we discuss the GM property of some special linear transformation pairs over infinite-dimensional vector spaces. In particular, it is proved that if R =- End（VD） is the endomorphism ring of an infinite-dimensional right vector space V over a division ring D with IC（D）I 〉 3 and g e R, then （a0q-alg, 9） is a GM pair for any ao, ale C（D）. Furthermore, two existing results are obtained as immediate consequences.展开更多
With the aim of “Win-Win Cooperation and Re-sponsible Development”, and themed on “Open Col-laboration, Technology Driven, Fashion Transforma-tion”, the three-day 2nd World Textile Merchandising Conference ended s...With the aim of “Win-Win Cooperation and Re-sponsible Development”, and themed on “Open Col-laboration, Technology Driven, Fashion Transforma-tion”, the three-day 2nd World Textile Merchandising Conference ended successfully on September 29th. The conference linked the global industrial think tanks to explore the industry's common prosperity and sus-tainable development.展开更多
Considering the features of martensitic transformation in Fe-Mn-Si based alloys, the Landau theory is established by introducing the density of stacking faults as a new order parameter η and the corresponding free en...Considering the features of martensitic transformation in Fe-Mn-Si based alloys, the Landau theory is established by introducing the density of stacking faults as a new order parameter η and the corresponding free energy function. By using such an order parameter, the stacking fault mechanism of the nucleation and growth for the γ(fcc) →ε(hcp) martensitic transformation can be reasonably explained, and a further detailed mechanism is proposed. The stacking faults are generated and overlapped in an irregular form at the beginning and then becoming regular to create some transition structures till a stable phase forms at a certain temperature. The importance of the interface soliton is to complete the transformations into various structures of martensite but not the twinned one. The thermodynamics of fcc→hcp transformation and those between different transition structures are described by the free energy function established in the present note.展开更多
基金supported by the National Science Foundation under award numbers CMMI-0855795 and 1129976DARPA under award number N66001-10-1-4018+1 种基金Department of Energy under award number DOE/DE-SC0006539supported in part by the National Science Foundation through Teragrid resources provided by TACC
文摘This paper presents a new methodology for coarse-grained atomistic simulation of inelastic material behavior including phase transformations in ceramics and dislocation mediated plasticity in metals. The methodology combines an atomistic formulation of balance equations and a modified finite element method. With significantly fewer degrees of freedom than those of a fully atomistic model and without additional constitutive rules but the interatomic force field, the new coarse-grained （CG） method is shown to be feasible in predicting the nonlinear constitutive re- sponses of materials and also reproducing atomic-scale phenomena such as phase transformations （diamond --, 13-Sn） in silicon and dislocation nucleation and migration, formation of dislocation loops and stacking faults ribbons in single crystal nickel. Direct comparisons between CG and the corresponding full molecular dynamics （MD） simulations show that the present methodology is efficient and promising in modeling and simulation of inelastic material behavior without losing the essential atomistic features. The potential applications and the limitations of the CG method are also discussed.
文摘Effect of boron on the microstructure and impact toughness in the coarse-grained heat-affected zone（CGHAZ）of two high strength low alloy steels,boron-free and boron-containing,was investigated by means of weld thermal simulation test.The result shows that,for the boron-free steel,a microstructure consisting of grain boundary ferrite degenerates pearlite and granular bainite for longer t8/5（the cooling time from 800 to 500 ℃）,while lath bainite for shorter t8/5.For the boron-containing steel,granular bainite is dominant for a wide range of t8/5.Continuous cooling transformation（CCT）study on the CGHAZ indicates that the transformation start temperature decreases by about 50-100℃under different t8/5,for the boron-containing steel compared with the boron-free steel.The presence of boron suppresses the nucleation of ferrite at prior austenite grain boundaries and hence enlarges the range of t8/5for granular bainite transformation.However,the addition of boron deteriorates the impact toughness of CGHAZ,which may be due to a markedly increased fraction of martensite-austenite（M-A）constituents and decreased fraction of high angle grain boundaries.
文摘In this paper, a non-Newtonian third-grade blood in coronary and femoral arteries is simulated analytically and numerically. The blood is considered as the third- grade non-Newtonian fluid under the periodic body acceleration motion and the pulsatile pressure gradient. The hybrid multi-step differential transformation method （Hybrid-Ms- DTM） and the Crank-Nicholson method （CNM） are used to solve the partial differential equation （PDE）, and a good agreement between them is observed in the results. The effects of the some physical parameters such as the amplitude, the lead angle, and the body acceleration frequency on the velocity and shear stress profiles are considered. The results show that increasing the amplitude, Ag, and reducing the lead angle of body acceleration, 9, make higher velocity profiles on the center line of both arteries. Also, the maximum wall shear stress increases when Ag increases.
文摘In this short note we discuss the GM property of some special linear transformation pairs over infinite-dimensional vector spaces. In particular, it is proved that if R =- End（VD） is the endomorphism ring of an infinite-dimensional right vector space V over a division ring D with IC（D）I 〉 3 and g e R, then （a0q-alg, 9） is a GM pair for any ao, ale C（D）. Furthermore, two existing results are obtained as immediate consequences.
文摘With the aim of “Win-Win Cooperation and Re-sponsible Development”, and themed on “Open Col-laboration, Technology Driven, Fashion Transforma-tion”, the three-day 2nd World Textile Merchandising Conference ended successfully on September 29th. The conference linked the global industrial think tanks to explore the industry's common prosperity and sus-tainable development.
基金This work was financially supported by the National Natural Science Foundation of China (Grant No. 59671023)the Emerson Electric Corporation of U.S.A.
文摘Considering the features of martensitic transformation in Fe-Mn-Si based alloys, the Landau theory is established by introducing the density of stacking faults as a new order parameter η and the corresponding free energy function. By using such an order parameter, the stacking fault mechanism of the nucleation and growth for the γ(fcc) →ε(hcp) martensitic transformation can be reasonably explained, and a further detailed mechanism is proposed. The stacking faults are generated and overlapped in an irregular form at the beginning and then becoming regular to create some transition structures till a stable phase forms at a certain temperature. The importance of the interface soliton is to complete the transformations into various structures of martensite but not the twinned one. The thermodynamics of fcc→hcp transformation and those between different transition structures are described by the free energy function established in the present note.
