In order to find the effect of state device installed on a carding machine on card sliver quality, card slivers produced in conditions of different voltages and gauges were tested by USTER AFIS. The results show that,...In order to find the effect of state device installed on a carding machine on card sliver quality, card slivers produced in conditions of different voltages and gauges were tested by USTER AFIS. The results show that, when the gauge is 1 nun, most parameters of card sliver quality are better when voltage is 600 V than those when no voltage is applied. The contents of nep, trash, visible foreign matter （VFM） and short fiber content by number （SFCn）, short fiber content by weight （SFCw）, immature fiber content （IFC） of card sliver decrease by 5.9%, 16.7%, 12.5%, 5.3%, 4.8% and 1.6%, respectively, but seed coat nep （SCN） content of card sliver doesn＇t decrease. When the electrostatic plate gauge is 2 mm and electrostatic voltage is 4000 V, the removal efficiency of neps and SCN is remarkable, decreasing by 8.7% and 25% respectively. Card sliver quality is hardly improved under any voltage when the gauge between electrostatic plate and cylinder is 3mm.展开更多
Sliver is a common but easily neglected defect in single crystal Ni-based superalloy castings.To date,there is still no unified viewpoint on its formation mechanism and generation causes.In this work,the orientation d...Sliver is a common but easily neglected defect in single crystal Ni-based superalloy castings.To date,there is still no unified viewpoint on its formation mechanism and generation causes.In this work,the orientation discontinuity and motion behavior of sliver defects were studied through experiments and numerical simulations.The ultrathin wedge-shaped specimen containing the grain boundary of the sliver and the matrix was prepared at the initial position of the sliver defect for the observation of equal thick-ness fringes.The discontinuity of equal thickness fringes on both sides of the grain boundary was ob-served through a transmission electron microscope,which directly confirms the abrupt change in the orientation between the sliver and matrix from the nanoscale.The crystal lattices at the smooth area and the bulging area of the grain boundary were found to have unusually different arrangements.The irregular lattice arrangement at the bulging area shows that the grain boundary has experienced high-stress deformation.Statistical results of sliver orientation deviation with a further composition analysis show the micro protuberance of the mold shell has a noticeable inductive effect on the sliver generation.Furthermore,a self-developed three-dimensional phase-field simulation model coupled with the spatial topology algorithm is established to simulate the orientation deflection behavior and orientation devia-tion threshold of fractured dendrites.The simulation results indicated that there is an upper limit of the cross-section solid fraction at the fracture position for the motion of the fractured dendrites.When the cross-section solid fraction at the fracture position is higher than this upper limit,it will be difficult to produce large deviation slivers due to the structural limitation of surrounding dendrites.This upper limit does not change with the solidification temperature gradient.展开更多
The specific distribution characteristics of inclusions along with the sliver defect were analyzed in detail to explain the formation mechanism of the sliver defect on the automobile exposed panel surface.A quantitati...The specific distribution characteristics of inclusions along with the sliver defect were analyzed in detail to explain the formation mechanism of the sliver defect on the automobile exposed panel surface.A quantitative electrolysis method was used to compare and evaluate the three-dimensional morphology,size,composition,quantity,and distribution of inclusions in the defect and non-defect zone of automobile exposed panel.The Al2O3 inclusions were observed to be aggregated or chain-like shape along with the sliver defect of about 3–10μm.The aggregation sections of the Al2O3 inclusions are distributed discretely along the rolling direction,with a spacing of 3–7 mm,a length of 6–7 mm,and a width of about 3 mm.The inclusion area part is 0.04%–0.16%with an average value of 0.08%,the inclusion number density is 40 mm−2 and the inclusion average spacing is 25.13μm.The inclusion spacing is approximately 40–160μm,with an average value of 68.76μm in chain-like inclusion parts.The average area fraction and number density of inclusions in the non-defect region were reduced to about 0.002%and 1–2 mm^−2,respectively,with the inclusion spacing of 400μm and the size of Al2O3 being 1–3μm.展开更多
Elementary units“bamboo bundle”and“bamboo sliver”were processed and cross-linked as“bamboo-bundle veneer(BBV)”and“bamboo-sliver veneer(BSV)”for preparation of laminated composites.The concept of“high-content-...Elementary units“bamboo bundle”and“bamboo sliver”were processed and cross-linked as“bamboo-bundle veneer(BBV)”and“bamboo-sliver veneer(BSV)”for preparation of laminated composites.The concept of“high-content-adhesive surface treatment”was raised to improve boards’performance,rather than increasing adhesive absorption of every layer’s porous unit.That is,some BBVs experienced an extra“dipping&drying”to absorb more resin(named“HBBV”).The effect of the amount of knitting threads was also discussed for influencing BBV’s quality.Results indicated that light transmittance of BBVs decreased as the amount of threads added from 3 to 8,while mechanical stiffness increased.Adding two skin layers of HBBVs symmetrically was helpful to enhance 24-hour underwater and 28-hour“boil-dry-boil”dimensional stability for boards with BSVs as core,while more than two pairs of HBBVs were needed to improve 28-hour“boil-dry-boil”dimensional stability of boards with BBVs as core.Two symmetrical surface layers of BBVs/HBBVs provided BSV-boards/BBV-boards with greater bending resistance,while such“surface treatment”would not raise shearing strength of BSV-boards upon 28-hour“boil-dry-boil”treatment.Besides,the data obtained from drop-hammer impact test indicated that more than two pair of surface BBVs or HBBVs were required for significant improvement in anti-impact property.展开更多
The chaotic nonlinear time series method is applied to analyze the sliver irregularity in textile processing.Because it unifies the system's determinacy and randomness,it seems more adaptive to describe the sliver...The chaotic nonlinear time series method is applied to analyze the sliver irregularity in textile processing.Because it unifies the system's determinacy and randomness,it seems more adaptive to describe the sliver irregularity than conventional methods.Firstly,the chaos character,i.e.fractal dimension,positive Lyapunov exponent,and state space parameters,including time delay and reconstruction dimension,are calculated respectively.As a result,a positive Lyapunov exponent and a fractal dimension are obtained,which demonstrates that the system is chaotic in fact.Secondly,both local linear forecast and global forecast models based on the reconstructed state are adopted to predict a segment part of the sliver irregularity series,which proves the validity of this analysis.Therefore,the sliver irregularity series shows the evidence of chaotic phenomena,and thus laying the theoretical foundation for analyzing and modeling the sliver irregularity series by applying the chaos theory,and providing a new way to understand the complexity of the sliver irregularity much better.展开更多
The carding cycle affects the sliver quality and the subsequent yarn attributes since it is the main sliver formation step. Processing parameters assume a significant part in affecting the nature of the eventual outco...The carding cycle affects the sliver quality and the subsequent yarn attributes since it is the main sliver formation step. Processing parameters assume a significant part in affecting the nature of the eventual outcome in any sorts of production. In the case of carding machine, a higher production rate makes the operation more sensitive. And this will cause degradation in product quality. So optimization of speed is the talk of the town in spinning field [1]. Extreme higher speed can prompt fiber harm and unnecessary neps generation will corrupt the end result. Again lower speed will lessen the production rate which isn’t reasonable. So we need to discover the ideal speed which will be advantageous to both product quality and production rate. In carding machine, real operational activity happens between flats and cards [1]. From an ordinary perspective, high produce able cards generates higher level of speed. Speed of the cards impacts the carding cycle and the nature of the yarn and in practical point of view, flat’s level of speed is advanced and optimized. The aim of the project was to find out the optimum flat speed in the context of yarn quality. 40 Ne cotton yarns were produced with the slivers manufactured at different flat speeds such as 240, 260, 280, 300 and 320 mm/min. The quality parameters of slivers and yarns were tested and analyzed.展开更多
Sliver defects are a group of low-to-medium angle misoriented grains in Ni-based single crystal superalloys that have received more attention in recent years.Occurrence of these defects can negatively affect the mecha...Sliver defects are a group of low-to-medium angle misoriented grains in Ni-based single crystal superalloys that have received more attention in recent years.Occurrence of these defects can negatively affect the mechanical properties of single crystal components.Therefore,studying the mechanisms of sliver formation and its effects on the final properties of alloys is of great importance.In this article,recent studies on the sliver defects were reviewed.Accordingly,the mechanisms of sliver formation as well as factors contributing to sliver initiation were studied.Additionally,effects of slivers on the mechanical properties of single crystal superalloys were discussed.Dendrite deformation and dendrite fracture are the main mechanisms for the sliver formation.This is a consequence of local stress concentration on dendrites during solidification.Therefore,locations such as inclusions,pores,geometrically complex areas,mould walls,freckle channels,etc.can be considered as the potential factors that promote the sliver initiation.Sliver formation significantly degrades the creep life of single-crystal superalloys.Studies have shown that when crystallographic misorientation exceeds approximately15°,creep life can be reduced by up to 47%.Despite the absence of a standardized criterion for predicting or preventing sliver initiation and propagation,their occurrence can be minimized through optimization of solidification parameters,careful grain selection,proper casting geometry design,and rigorous control of material purity and equipment conditions.展开更多
Since March 2011, the prolonged war in Syria has become a nightmare haunt- ing its people and delivering each of them the bitter taste of terror. As the Syrian conflict enters its seventh year, some positive changes h...Since March 2011, the prolonged war in Syria has become a nightmare haunt- ing its people and delivering each of them the bitter taste of terror. As the Syrian conflict enters its seventh year, some positive changes have occurred. Will the Syrian people seize the sliver of hope for peace？展开更多
基金Supported by Fund of Scientific and Technological Key Project Plan of Liaoning Province , China(No.2003220026)Fund of Education Depart ment of Liaoning Province,China(No.05L147)
文摘In order to find the effect of state device installed on a carding machine on card sliver quality, card slivers produced in conditions of different voltages and gauges were tested by USTER AFIS. The results show that, when the gauge is 1 nun, most parameters of card sliver quality are better when voltage is 600 V than those when no voltage is applied. The contents of nep, trash, visible foreign matter （VFM） and short fiber content by number （SFCn）, short fiber content by weight （SFCw）, immature fiber content （IFC） of card sliver decrease by 5.9%, 16.7%, 12.5%, 5.3%, 4.8% and 1.6%, respectively, but seed coat nep （SCN） content of card sliver doesn＇t decrease. When the electrostatic plate gauge is 2 mm and electrostatic voltage is 4000 V, the removal efficiency of neps and SCN is remarkable, decreasing by 8.7% and 25% respectively. Card sliver quality is hardly improved under any voltage when the gauge between electrostatic plate and cylinder is 3mm.
基金This work was financially supported by the National Science and Technology Major Project(Nos.2017-VⅠ-0003-0073 and 2017-Ⅶ-0008-0101).The authors are grateful to Prof.Yao Kefu and Miss.Liao Yang in Tsinghua University for the assistance and advice with the analysis of TEM results.
文摘Sliver is a common but easily neglected defect in single crystal Ni-based superalloy castings.To date,there is still no unified viewpoint on its formation mechanism and generation causes.In this work,the orientation discontinuity and motion behavior of sliver defects were studied through experiments and numerical simulations.The ultrathin wedge-shaped specimen containing the grain boundary of the sliver and the matrix was prepared at the initial position of the sliver defect for the observation of equal thick-ness fringes.The discontinuity of equal thickness fringes on both sides of the grain boundary was ob-served through a transmission electron microscope,which directly confirms the abrupt change in the orientation between the sliver and matrix from the nanoscale.The crystal lattices at the smooth area and the bulging area of the grain boundary were found to have unusually different arrangements.The irregular lattice arrangement at the bulging area shows that the grain boundary has experienced high-stress deformation.Statistical results of sliver orientation deviation with a further composition analysis show the micro protuberance of the mold shell has a noticeable inductive effect on the sliver generation.Furthermore,a self-developed three-dimensional phase-field simulation model coupled with the spatial topology algorithm is established to simulate the orientation deflection behavior and orientation devia-tion threshold of fractured dendrites.The simulation results indicated that there is an upper limit of the cross-section solid fraction at the fracture position for the motion of the fractured dendrites.When the cross-section solid fraction at the fracture position is higher than this upper limit,it will be difficult to produce large deviation slivers due to the structural limitation of surrounding dendrites.This upper limit does not change with the solidification temperature gradient.
基金This work was financially supported by the National Natural Science Foundation of China(No.U1960202).
文摘The specific distribution characteristics of inclusions along with the sliver defect were analyzed in detail to explain the formation mechanism of the sliver defect on the automobile exposed panel surface.A quantitative electrolysis method was used to compare and evaluate the three-dimensional morphology,size,composition,quantity,and distribution of inclusions in the defect and non-defect zone of automobile exposed panel.The Al2O3 inclusions were observed to be aggregated or chain-like shape along with the sliver defect of about 3–10μm.The aggregation sections of the Al2O3 inclusions are distributed discretely along the rolling direction,with a spacing of 3–7 mm,a length of 6–7 mm,and a width of about 3 mm.The inclusion area part is 0.04%–0.16%with an average value of 0.08%,the inclusion number density is 40 mm−2 and the inclusion average spacing is 25.13μm.The inclusion spacing is approximately 40–160μm,with an average value of 68.76μm in chain-like inclusion parts.The average area fraction and number density of inclusions in the non-defect region were reduced to about 0.002%and 1–2 mm^−2,respectively,with the inclusion spacing of 400μm and the size of Al2O3 being 1–3μm.
基金supported by Open Fund of Key Laboratory of National Forestry and Grassland Administration/Beijing for Bamboo&Rattan Science and Technology[ICBR-2020-11]China Postdoctoral Science Foundation[2019M660500]Fundamental Research Funds of International Center for Bamboo and Rattan[1632019003].
文摘Elementary units“bamboo bundle”and“bamboo sliver”were processed and cross-linked as“bamboo-bundle veneer(BBV)”and“bamboo-sliver veneer(BSV)”for preparation of laminated composites.The concept of“high-content-adhesive surface treatment”was raised to improve boards’performance,rather than increasing adhesive absorption of every layer’s porous unit.That is,some BBVs experienced an extra“dipping&drying”to absorb more resin(named“HBBV”).The effect of the amount of knitting threads was also discussed for influencing BBV’s quality.Results indicated that light transmittance of BBVs decreased as the amount of threads added from 3 to 8,while mechanical stiffness increased.Adding two skin layers of HBBVs symmetrically was helpful to enhance 24-hour underwater and 28-hour“boil-dry-boil”dimensional stability for boards with BSVs as core,while more than two pairs of HBBVs were needed to improve 28-hour“boil-dry-boil”dimensional stability of boards with BBVs as core.Two symmetrical surface layers of BBVs/HBBVs provided BSV-boards/BBV-boards with greater bending resistance,while such“surface treatment”would not raise shearing strength of BSV-boards upon 28-hour“boil-dry-boil”treatment.Besides,the data obtained from drop-hammer impact test indicated that more than two pair of surface BBVs or HBBVs were required for significant improvement in anti-impact property.
文摘The chaotic nonlinear time series method is applied to analyze the sliver irregularity in textile processing.Because it unifies the system's determinacy and randomness,it seems more adaptive to describe the sliver irregularity than conventional methods.Firstly,the chaos character,i.e.fractal dimension,positive Lyapunov exponent,and state space parameters,including time delay and reconstruction dimension,are calculated respectively.As a result,a positive Lyapunov exponent and a fractal dimension are obtained,which demonstrates that the system is chaotic in fact.Secondly,both local linear forecast and global forecast models based on the reconstructed state are adopted to predict a segment part of the sliver irregularity series,which proves the validity of this analysis.Therefore,the sliver irregularity series shows the evidence of chaotic phenomena,and thus laying the theoretical foundation for analyzing and modeling the sliver irregularity series by applying the chaos theory,and providing a new way to understand the complexity of the sliver irregularity much better.
文摘The carding cycle affects the sliver quality and the subsequent yarn attributes since it is the main sliver formation step. Processing parameters assume a significant part in affecting the nature of the eventual outcome in any sorts of production. In the case of carding machine, a higher production rate makes the operation more sensitive. And this will cause degradation in product quality. So optimization of speed is the talk of the town in spinning field [1]. Extreme higher speed can prompt fiber harm and unnecessary neps generation will corrupt the end result. Again lower speed will lessen the production rate which isn’t reasonable. So we need to discover the ideal speed which will be advantageous to both product quality and production rate. In carding machine, real operational activity happens between flats and cards [1]. From an ordinary perspective, high produce able cards generates higher level of speed. Speed of the cards impacts the carding cycle and the nature of the yarn and in practical point of view, flat’s level of speed is advanced and optimized. The aim of the project was to find out the optimum flat speed in the context of yarn quality. 40 Ne cotton yarns were produced with the slivers manufactured at different flat speeds such as 240, 260, 280, 300 and 320 mm/min. The quality parameters of slivers and yarns were tested and analyzed.
文摘Sliver defects are a group of low-to-medium angle misoriented grains in Ni-based single crystal superalloys that have received more attention in recent years.Occurrence of these defects can negatively affect the mechanical properties of single crystal components.Therefore,studying the mechanisms of sliver formation and its effects on the final properties of alloys is of great importance.In this article,recent studies on the sliver defects were reviewed.Accordingly,the mechanisms of sliver formation as well as factors contributing to sliver initiation were studied.Additionally,effects of slivers on the mechanical properties of single crystal superalloys were discussed.Dendrite deformation and dendrite fracture are the main mechanisms for the sliver formation.This is a consequence of local stress concentration on dendrites during solidification.Therefore,locations such as inclusions,pores,geometrically complex areas,mould walls,freckle channels,etc.can be considered as the potential factors that promote the sliver initiation.Sliver formation significantly degrades the creep life of single-crystal superalloys.Studies have shown that when crystallographic misorientation exceeds approximately15°,creep life can be reduced by up to 47%.Despite the absence of a standardized criterion for predicting or preventing sliver initiation and propagation,their occurrence can be minimized through optimization of solidification parameters,careful grain selection,proper casting geometry design,and rigorous control of material purity and equipment conditions.
文摘Since March 2011, the prolonged war in Syria has become a nightmare haunt- ing its people and delivering each of them the bitter taste of terror. As the Syrian conflict enters its seventh year, some positive changes have occurred. Will the Syrian people seize the sliver of hope for peace？
