In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model...In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions relative residual thickness of billet (T/R0),frictional factor (m) or relative land length of ram and chamber are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).展开更多
The objective of the study was to prepare solid dispersions containing a thermally unstable drug by hot-melt extrusion(HME).Carbamazepine(CBZ)was selected as model drug and combinations of Kollidon VA64(VA64),Soluplus...The objective of the study was to prepare solid dispersions containing a thermally unstable drug by hot-melt extrusion(HME).Carbamazepine(CBZ)was selected as model drug and combinations of Kollidon VA64(VA64),Soluplus(SOL)and Eudragit EPO(EPO)were utilized as carriers.Preformulation was conducted to identify the suitability of polymer combinations based on solubility parameters,differential scanning calorimetry(DSC),hot stage microscopy and thermogravimetric analysis.Physicochemical properties of solid dispersions were determined by DSC,X-ray diffraction,fourier transform infrared spectroscopy,dissolution and accelerated stability testing.The results show that drug-polymer miscibility at temperatures below the melting point(Tm)of CBZ was improved by combining EPO with VA64 or SOL.With 30%drug loading in a solid dispersion in SOL:EPO(1:1,w/w),CBZ was mainly present in an amorphous form accompanied by a small amount of a microcrystalline form.The dissolution rate of the solid dispersion was significantly increased(approximately 90%within 5 min)compared to either the pure drug(approximately 85%within 60 min)or the corresponding physical mixture(approximately 80%within 60 min)before and after storage.The solid dispersion in SOL:EPO(1:1,w/w)was relatively stable at 401C/75%RH under CBZ tablet packaging conditions for at least 3 months.In conclusion,polymer combinations that improve drug-polymer miscibility at an HME processing temperature below the Tm of a drug appear to be beneficial in the preparation of solid dispersions containing thermally unstable drugs.展开更多
The AZ31/GW103 K bimetallic composite plates were prepared by co-extrusion of different combination types(sandwich extrusion type and double semicircle extrusion type),and effects of different extrusion combination ty...The AZ31/GW103 K bimetallic composite plates were prepared by co-extrusion of different combination types(sandwich extrusion type and double semicircle extrusion type),and effects of different extrusion combination types on the microstructure and mechanical properties of bimetallic composite plates were systematically investigated.The results show that both the AZ31/GW103 K bimetallic composite plates prepared by different extrusion combination types have good metallurgical bonding,and changing the combination type does not affect the thickness of the interfacial transition layer of composite plates.Compared with the monolithic AZ31 and GW103 K extruded plates,co-extrusion can promote the dynamic recrystallization(DRX)of AZ31 and GW103 K components in composite plates,and double semicircular extrusion type has a better promotion effect on the DRX than sandwich extrusion type.In addition,the texture of AZ31 in both monolithic AZ31 and AZ31/GW103 K/AZ31(A/G/A)plates is a typical(0002)basal texture,while that in the AZ31/GW103 K(A/G)composite plate shifts to the tangent direction(TD)of extruded plate.Compared with the monolithic AZ31 extruded plate,both the yield strength and tensile strength of A/G and A/G/A bimetallic composite plates are significantly improved.The strength of A/G/A composite plate is higher than that of A/G composite plate,but its elongation is worse.Meanwhile,co-extrusion reduces the dislocation density of AZ31 and GW 103 K components in composite plates,and different extrusion combination types also affect the dislocation density.展开更多
文摘In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions relative residual thickness of billet (T/R0),frictional factor (m) or relative land length of ram and chamber are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).
文摘The objective of the study was to prepare solid dispersions containing a thermally unstable drug by hot-melt extrusion(HME).Carbamazepine(CBZ)was selected as model drug and combinations of Kollidon VA64(VA64),Soluplus(SOL)and Eudragit EPO(EPO)were utilized as carriers.Preformulation was conducted to identify the suitability of polymer combinations based on solubility parameters,differential scanning calorimetry(DSC),hot stage microscopy and thermogravimetric analysis.Physicochemical properties of solid dispersions were determined by DSC,X-ray diffraction,fourier transform infrared spectroscopy,dissolution and accelerated stability testing.The results show that drug-polymer miscibility at temperatures below the melting point(Tm)of CBZ was improved by combining EPO with VA64 or SOL.With 30%drug loading in a solid dispersion in SOL:EPO(1:1,w/w),CBZ was mainly present in an amorphous form accompanied by a small amount of a microcrystalline form.The dissolution rate of the solid dispersion was significantly increased(approximately 90%within 5 min)compared to either the pure drug(approximately 85%within 60 min)or the corresponding physical mixture(approximately 80%within 60 min)before and after storage.The solid dispersion in SOL:EPO(1:1,w/w)was relatively stable at 401C/75%RH under CBZ tablet packaging conditions for at least 3 months.In conclusion,polymer combinations that improve drug-polymer miscibility at an HME processing temperature below the Tm of a drug appear to be beneficial in the preparation of solid dispersions containing thermally unstable drugs.
基金financially supported by the National Natural Science Foundation of China(Nos.U1810122,U1710118,52174362 and 51975207)the Yantai High-End Talent Introduction"Double Hundred Plan"(2021)+3 种基金the Talent Training Program for Shandong Province Higher Educational Youth Innovative Teams(2019)the Key Research and Development Program of Shanxi Province(Nos.201903D421076 and 201803D421086)the Innovative Talents of Higher Education Institutions of Shanxi(2018)the Central Government Guided Local Science and Technology Development Projects(No.YDZJSX2021A010)。
文摘The AZ31/GW103 K bimetallic composite plates were prepared by co-extrusion of different combination types(sandwich extrusion type and double semicircle extrusion type),and effects of different extrusion combination types on the microstructure and mechanical properties of bimetallic composite plates were systematically investigated.The results show that both the AZ31/GW103 K bimetallic composite plates prepared by different extrusion combination types have good metallurgical bonding,and changing the combination type does not affect the thickness of the interfacial transition layer of composite plates.Compared with the monolithic AZ31 and GW103 K extruded plates,co-extrusion can promote the dynamic recrystallization(DRX)of AZ31 and GW103 K components in composite plates,and double semicircular extrusion type has a better promotion effect on the DRX than sandwich extrusion type.In addition,the texture of AZ31 in both monolithic AZ31 and AZ31/GW103 K/AZ31(A/G/A)plates is a typical(0002)basal texture,while that in the AZ31/GW103 K(A/G)composite plate shifts to the tangent direction(TD)of extruded plate.Compared with the monolithic AZ31 extruded plate,both the yield strength and tensile strength of A/G and A/G/A bimetallic composite plates are significantly improved.The strength of A/G/A composite plate is higher than that of A/G composite plate,but its elongation is worse.Meanwhile,co-extrusion reduces the dislocation density of AZ31 and GW 103 K components in composite plates,and different extrusion combination types also affect the dislocation density.
