Identifying suitable processing window is necessary but difficult for achieving favorable microstructure and performance in extrusion of large thick-walled pipe with difficult-to-deform Inconel 625 alloy. In this work...Identifying suitable processing window is necessary but difficult for achieving favorable microstructure and performance in extrusion of large thick-walled pipe with difficult-to-deform Inconel 625 alloy. In this work, a method was established for identifying the extrusion process window considering temperature control using response surface methodology. Firstly, the response surface models, which correlate temperature rise and peak temperature to key extrusion parameters, have been developed by orthogonal regression based on finite element calculated data. Secondly, the coupled effects of the key extrusion parameters on the temperature rise and peak temperature have been disclosed based on the regression models. Lastly, suitable extrusion processing windows, which are described by contour map of peak temperature in the space of extrusion speed and initial billet temperature, have been established for different extrusion ratios. Using the identified process window, a suitable combination of the key extrusion parameters can be determined conveniently and quickly.展开更多
The machining characteristics of LM25 Al/SiCp composite using end milling was investigated.A comprehensive mathematical model was developed for correlating the interactive and higher order influences of various proces...The machining characteristics of LM25 Al/SiCp composite using end milling was investigated.A comprehensive mathematical model was developed for correlating the interactive and higher order influences of various process parameters on the dominant machining criteria,i.e.the tool flank wear phenomena,through response surface methodology,utilizing relevant experimental data obtained through experimentation.Experimental plan was performed by a standard response surface methodology design called a central composite design（CCD）.The results of analysis of variance（ANOVA）indicate that the proposed mathematical model can adequately describe the performance within the limits of the studied factors.Optimal combination of these parameters can be used to achieve the minimum tool flank wear.展开更多
In order to investigate the seismic performance of geosynthetic reinforced and pile supported(GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This ...In order to investigate the seismic performance of geosynthetic reinforced and pile supported(GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This method is based on the explicit finite element method while considering the viscous-spring artificial boundary(VSAB) condition. Using the proposed method, a numerical study was conducted, and the influence of oblique incidence on the seismic response of GRPS embankment under the oblique incident P waves was analyzed. The results indicate that in comparison with vertical incidence, the oblique incidence can significantly increase the displacement, velocity and acceleration of key locations in the GRPS embankment. The existence of geosynthetics can alleviate the impact of seismic load on the response of the embankment to a certain degree. Moreover, the number of reinforcement layers and modulus of geogrid also greatly influence the seismic performance of GRPS embankment.展开更多
A batch is a subset of jobs which must be processed jointly in either serial or parallel form. For the single machine, batching, total completion time scheduling problems, the algorithmic aspects have been extensively...A batch is a subset of jobs which must be processed jointly in either serial or parallel form. For the single machine, batching, total completion time scheduling problems, the algorithmic aspects have been extensively studied in the literature. This paper presents the optimal hatching structures of the problems on the batching ways： all jobs in exactly N（arbitrary fix batch number and 1 〈 N 〈 n） batches.展开更多
This paper is concerned with the stability analysis of reinforced slopes.A new approach based on the limit equilibrium principle is proposed to evaluate the stability of the reinforced slopes.The effect of reinforceme...This paper is concerned with the stability analysis of reinforced slopes.A new approach based on the limit equilibrium principle is proposed to evaluate the stability of the reinforced slopes.The effect of reinforcement is modeled as an equivalent restoring force acting the bottom of the slice and added into the general limit equilibrium(GLE) method.The equations of force and moment equilibrium of the slice are derived and corresponding iterative solution methods are provided.The new method can satisfy both the force and the moment equilibrium and be applicable to the critical failure surface of arbitrary form.Furthermore,the results predicted by the proposed method are compared with the calculation examples of other researchers and the centrifuge model test results to validate its correctness and effectiveness.展开更多
Porous poly(vinylidene fluoride)(PVDF)/poly(methyl methacrylate)(PMMA) blend five-bore hollow fiber membranes are prepared by wet phase inversion methods.In spinning these PVDF hollow fibers, N,N-dimethylacetamide(DMA...Porous poly(vinylidene fluoride)(PVDF)/poly(methyl methacrylate)(PMMA) blend five-bore hollow fiber membranes are prepared by wet phase inversion methods.In spinning these PVDF hollow fibers, N,N-dimethylacetamide(DMAc) and polyvinyl pyrrolidone(PVP) are used as the solvent and the non-solvent additive,respectively.The external coagulant uses water.The internal coagulants use water and DMAc-water solutions.The membranes are characterized in terms of water flux and molecular weight cut-off for the wet membranes.The cross-sectional structures are examined by scanning electron microscopy(SEM).The effects of polymer concentration and the internal coagulant on the permeation properties and membrane structures are examined keeping the bore liquid flow and air-gap constants.Relative high flux,rejection and strengh PVDF five-bore hollow fiber membranes could be prepared from the polymer concentration in dope solution at 17%of mass fraction,the air gap distance of 14 cm,and using 10%of mass fraction of DMAc solution as the internal coagulant at 13 mL/min of flow.展开更多
基金Project(2009ZX04005-031-11)supported by the Major National Science and Technology Special Project of ChinaProject(318968)supported by the Marie Curie International Research Staff Exchange Scheme(IRSES,Mat Pro Future)within the 7th EC Framework Program(FP7)Project(B08040)supported by the 111 Plan,China
文摘Identifying suitable processing window is necessary but difficult for achieving favorable microstructure and performance in extrusion of large thick-walled pipe with difficult-to-deform Inconel 625 alloy. In this work, a method was established for identifying the extrusion process window considering temperature control using response surface methodology. Firstly, the response surface models, which correlate temperature rise and peak temperature to key extrusion parameters, have been developed by orthogonal regression based on finite element calculated data. Secondly, the coupled effects of the key extrusion parameters on the temperature rise and peak temperature have been disclosed based on the regression models. Lastly, suitable extrusion processing windows, which are described by contour map of peak temperature in the space of extrusion speed and initial billet temperature, have been established for different extrusion ratios. Using the identified process window, a suitable combination of the key extrusion parameters can be determined conveniently and quickly.
文摘The machining characteristics of LM25 Al/SiCp composite using end milling was investigated.A comprehensive mathematical model was developed for correlating the interactive and higher order influences of various process parameters on the dominant machining criteria,i.e.the tool flank wear phenomena,through response surface methodology,utilizing relevant experimental data obtained through experimentation.Experimental plan was performed by a standard response surface methodology design called a central composite design（CCD）.The results of analysis of variance（ANOVA）indicate that the proposed mathematical model can adequately describe the performance within the limits of the studied factors.Optimal combination of these parameters can be used to achieve the minimum tool flank wear.
基金Projects(41202220,41472278,51478438)supported by the National Natural Science Foundation of ChinaProjects(20120022120003,20134101120009)supported by the Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(2652012065)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(14A560014)supported by the Key Project of Education Department in Henan Province,China
文摘In order to investigate the seismic performance of geosynthetic reinforced and pile supported(GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This method is based on the explicit finite element method while considering the viscous-spring artificial boundary(VSAB) condition. Using the proposed method, a numerical study was conducted, and the influence of oblique incidence on the seismic response of GRPS embankment under the oblique incident P waves was analyzed. The results indicate that in comparison with vertical incidence, the oblique incidence can significantly increase the displacement, velocity and acceleration of key locations in the GRPS embankment. The existence of geosynthetics can alleviate the impact of seismic load on the response of the embankment to a certain degree. Moreover, the number of reinforcement layers and modulus of geogrid also greatly influence the seismic performance of GRPS embankment.
基金Supported by the NSF of Henan Province(082300410070)
文摘A batch is a subset of jobs which must be processed jointly in either serial or parallel form. For the single machine, batching, total completion time scheduling problems, the algorithmic aspects have been extensively studied in the literature. This paper presents the optimal hatching structures of the problems on the batching ways： all jobs in exactly N（arbitrary fix batch number and 1 〈 N 〈 n） batches.
基金funded by the Key Industrial Science and Technology Project of Shaanxi Province(No.2015GY149)the Scientific Project funded by the Ministry of Housing and Urban-Rural Development of the People’s Republic of China Council(No.2015-K2-008)
文摘This paper is concerned with the stability analysis of reinforced slopes.A new approach based on the limit equilibrium principle is proposed to evaluate the stability of the reinforced slopes.The effect of reinforcement is modeled as an equivalent restoring force acting the bottom of the slice and added into the general limit equilibrium(GLE) method.The equations of force and moment equilibrium of the slice are derived and corresponding iterative solution methods are provided.The new method can satisfy both the force and the moment equilibrium and be applicable to the critical failure surface of arbitrary form.Furthermore,the results predicted by the proposed method are compared with the calculation examples of other researchers and the centrifuge model test results to validate its correctness and effectiveness.
基金the China Postdoctoral Science Foundation (No.20110490645)the Science Foundation of Shanghai(No.11ZR1400800)
文摘Porous poly(vinylidene fluoride)(PVDF)/poly(methyl methacrylate)(PMMA) blend five-bore hollow fiber membranes are prepared by wet phase inversion methods.In spinning these PVDF hollow fibers, N,N-dimethylacetamide(DMAc) and polyvinyl pyrrolidone(PVP) are used as the solvent and the non-solvent additive,respectively.The external coagulant uses water.The internal coagulants use water and DMAc-water solutions.The membranes are characterized in terms of water flux and molecular weight cut-off for the wet membranes.The cross-sectional structures are examined by scanning electron microscopy(SEM).The effects of polymer concentration and the internal coagulant on the permeation properties and membrane structures are examined keeping the bore liquid flow and air-gap constants.Relative high flux,rejection and strengh PVDF five-bore hollow fiber membranes could be prepared from the polymer concentration in dope solution at 17%of mass fraction,the air gap distance of 14 cm,and using 10%of mass fraction of DMAc solution as the internal coagulant at 13 mL/min of flow.
