Dew is an important supplement water source in arid and semi-arid areas. In order to determine the dew formation on different kinds of soils associated with various shrub species and microhabitats, we performed measur...Dew is an important supplement water source in arid and semi-arid areas. In order to determine the dew formation on different kinds of soils associated with various shrub species and microhabitats, we performed measurement of accumulated dew formation amount and duration in October 2009 in a revegetation-stabilized arid desert ecosystem in Shapotou area, northern China. The results indicated that the accumulated dew formation amount was four times larger at open spaces as compared to under the canopy, and it was nearly twice as much under living Artemisia ordosica plants(L.A.) as compared to under living Caragana korshinskii plants(L.C.). The opposite characteristics were found for dew duration between different microhabitats. Dew amounts at different vertical heights around the shrub stands were in the order of 50 cm above the canopy〉the canopy edge〉under the canopy. Dew amount continued to increase after dawn, and the proportion of average accumulated dew amount after dawn accounting for the average maximum amount increased from above the canopy to under the canopy. Dew formation duration after sunrise accounted for more than 50% of the total formation duration during the day time. Contrary to the distribution characteristics of dew amount, dew duration after dawn and total dew formation duration during the day time were both highest under the canopy, followed by at the canopy edge and then at 50 cm above the canopy. The portion of dew duration after dawn accounting for the total dew duration during the day time increased from above the canopy to under the canopy. From these results, we may conclude that dew availability as a supplemental water resource for improving the microhabitats in water-limited arid ecosystems is position dependent especially for the plant microhabitats at different stands layers.展开更多
The fact that the amount of the mold flux components differs at differentlocations on the cracking surface indicates that the longitudinal surface cracks are initiallyformed in the mold and are enlarged in the seconda...The fact that the amount of the mold flux components differs at differentlocations on the cracking surface indicates that the longitudinal surface cracks are initiallyformed in the mold and are enlarged in the secondary cooling zone. Based on the hot ductilitymeasurement of two typical container used steels, it is known that the steels are in severeembrittlement state in the temperature range of 825-775 deg C. By means of increasing Cr/Ni platingthickness on the upper part of the mold, reducing mold heat flux, adopting new secondary coolingpattern, etc., the occurrence of the surface longitudinal cracks on the steel CC (continuouscasting) slabs has been significantly reduced.展开更多
The design of the cooling system of injection molds directly affects both productivity and the quality of the final part. Using the cooling process CAE system to instruct the mold design, the efficiency and quality ...The design of the cooling system of injection molds directly affects both productivity and the quality of the final part. Using the cooling process CAE system to instruct the mold design, the efficiency and quality of design can be improved greatly. At the same time, it is helpful to confirm the cooling system structure and optimize the process conditions. In this paper, the 3D surface model of mold cavity is used to replace the middle-plane model in the simulation by Boundary Element Method, which break the bottleneck of the application of the injection molding simulation softwares base on the middle-plane model. With the improvements of this paper, a practical and commercial simulation software of injection molding cooling process named as HsCAE3D6.0 is developed.展开更多
On the basis of the comprehensive analysis about the automatic generation of the injection mold parting surface, the parting surface design method which introduces knowledge and case-based reasoning (CBR) into the c...On the basis of the comprehensive analysis about the automatic generation of the injection mold parting surface, the parting surface design method which introduces knowledge and case-based reasoning (CBR) into the computer-aided design is described by combining with the actual characteristic in injection mold design, and the design process of case-based reasoning method is also given. A case library including the information of parting surface is built with the index of main shape features, The automatic design of the mold parting surface is realized combined with the forward-reasoning method and the similarity solution procedure. The rule knowledge library is also founded including the knowledge, principles and experiences for parting surface design. An example is used to show the validity of the method, and the quality and the efficiency of the mold design are improved.展开更多
The effects of the wavelength and orientation of machined grooves on a mold surface, casting speed, and melt superheat on the formation of surface marks on as-cast ingots were studied with an immersion casting tester ...The effects of the wavelength and orientation of machined grooves on a mold surface, casting speed, and melt superheat on the formation of surface marks on as-cast ingots were studied with an immersion casting tester and copper mold chill blocks. The mold surface topographies included a polished smooth surface, and those with machined unidirectional parallel contoured grooves oriented either parallel (vertical) or perpendicular (horizontal) to the casting direction. The unidirectional grooves were 0.232 mm deep with wavelength or spacing between 1 and 15 mm. The casting speed and melt superheat were between 1 and 200 mm/s, and 10 and 50 K, respectively. Two primary types of surface marks were observed on ingots cast with the copper mold with smooth surface topography, namely the finer and closely spaced ripples (Type I), and the widely spaced but coarser laps (Type II). The latter were more prevalent at the higher casting speeds and melt superheats. Qualitatively, formation of both types of surface marks on the as-cast ingots of the aluminum alloy 3003 appeared to be alleviated by increase in casting speed and melt superheat, and by the use of molds with grooved surface topography. In fact, casting with a mold surface with 1 mm spaced grooves that are perpendicular to the casting direction eliminated the formation of surface marks at casting speeds greater than 1 mm/s. It also improved the uniformity of the ingot subsurface microstructure and eliminated the associated subsurface segregation.展开更多
In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies ...In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies used to form thin glass components is investigated. The surface roughness of the polished stainless steel molding die surface is below Rz = 200 nm (P-V) at 15 h polishing with 0.5 % alumina polishing liquid. In the case of polishing process with only the weight of molding die and a polishing pressure of 0.5 kPa, polishing times are approximately 60 h and 20 h, respectively. Final surface roughness polished stainless steel molding die surface with pressure of 0.5 kPa is Rz = 7 nm (P-V), rms -- 1.6 nm and Ra = 1.4 nm. In a thin glass component manufacturing method, "slumping method", surface roughness before glass forming is rms = 0.7 nm and Ra = 0.6 nm, and after is rms = 0.7 nm and Ra = 0.6 nm. Therefore, there were no observable changes their surface roughness.展开更多
Deformation of casting during the solidification process has puzzled many engineers and scientists for years. In order to attain the goal of near-net forming by casting, numerical simulation is a powerful tool. Tradit...Deformation of casting during the solidification process has puzzled many engineers and scientists for years. In order to attain the goal of near-net forming by casting, numerical simulation is a powerful tool. Traditional methods compute the thermal stress of both the casting and the mold. This method suffers the problem of massive calculation and failure of convergence. This paper proposes an improved Mold Surface Element Method, the main idea of which is to use the surface elements instead of body elements to express the interactions between the casting and the mold. The proposed method shows a high computation efficiency and provides satisfactory precision for engineering. Two practical casting products were used to verify the proposed method. The simulated results agree well with those observed in practical products. The proposed method is believed to benefit production practice and to provide theoretical guidance.展开更多
Polishing is an important finishing process in die and mold manufacturing. Hand polishing takes long time and much labor. Efforts are made to automate the polishing process while keeping accuracy. Recently grinding ce...Polishing is an important finishing process in die and mold manufacturing. Hand polishing takes long time and much labor. Efforts are made to automate the polishing process while keeping accuracy. Recently grinding centers have been developed, which are used for free surface polishing in the present work. The new polishing technique applies the same cutting locus as used in the cutting process to remove only cusp height effectively, keeping the form accuracy generated in the cutting process.展开更多
Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing ...Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing the number of input factors and to include all possible interactions. For this purpose, two-stage experimentation is suggested: a factor screening stage and Response Surface optimization stage. In screening stage Taguchi 3 level experimental design is used to classify the input parameters as significant and non-significant factors. Eight input variables were classified into 3 non-significant and 5 significant factors using this screening stage. Thus for the Response Surface optimization stage: instead of doing 160 experiments in Central Composite, 56 are only needed after the screening stage in half Central Composite Design. The best subset and regression model fitting tools in addition to model verification using randomly selected input setting were used to select a model for predicting residual stresses with a verified Root Mean Square Error (RSME) of nearly 0.93 MPa.展开更多
A 3D mathematical model was proposed to simulate the mold filling process in high-pressure die casting(HPDC) to improve accuracy considering the surface tension. Piecewise liner interface calculation(PLIC) and volume ...A 3D mathematical model was proposed to simulate the mold filling process in high-pressure die casting(HPDC) to improve accuracy considering the surface tension. Piecewise liner interface calculation(PLIC) and volume of fluid(VOF) methods were used to construct the pattern of the liquid interface. A coupled levelset and VOF method(CLSVOF) was proposed to capture the interface pattern and obtain its normal vector. A continuum surface force(CSF) model was used to consider the surface tension. Two water analogy experiments were carried out using the proposed model. Simulation and experimental results were analyzed and compared; and the effects of surface tension were also discussed. The simulation results agreed well with the experiments and the simulation accuracy was an improvement on interface geometries, liquid flows, and gas entrapments.展开更多
The in vitro degradation rate of polyanhydride (poly(sebacic acid), diacetoxy terminated), also known as PSADT, was investigated. PSADT tablets with a circular cross-section were formed using a compression molding...The in vitro degradation rate of polyanhydride (poly(sebacic acid), diacetoxy terminated), also known as PSADT, was investigated. PSADT tablets with a circular cross-section were formed using a compression molding device, and then immersed into phosphate buffer saline (PBS) for in vitro degradation experiments. The mechanisms of degradation and the degradation rate were characterized by the change in molecular weight and reduction in specimen mass. In addition, the effects of processing temperature and the geometry of the formed PSADT tablets on the rate of degradation were studied. The surface morphology at different degradation times was observed by scanning electron microscopy (SEM). The experimental results showed that PSADT exhibited sur^hce erosion due to the fact that near zero-order degradation kinetics was observed during its degradation process. Moreover, it is found that the geometry of tablets played an important role on the rate of degradation, while the processing temperature had no significant effect on the PSADT degradation rate.展开更多
The potential of a 3D FDM (Finite Difference Method) computer code was presented, in prediction of flow patterns by modeling the mold filling phenomena through different gating systems. In this code, improvements and ...The potential of a 3D FDM (Finite Difference Method) computer code was presented, in prediction of flow patterns by modeling the mold filling phenomena through different gating systems. In this code, improvements and modifications were made on the original SOLA VOF and Donor Acceptor algorithms. A more accurate solution procedure for handling free surfaces is developed in order to describe the flows through complicated gating designs. A block casting of 200?mm×200?mm×50?mm with two different gating designs was chosen as the verifying problem. Water analog studies are carried out on these two gating designs. The comparison indicates that computer simulation could be a powerful tool in shaping gating systems.展开更多
In order to solve the problem of the high surface longitudinal crack ratio of heavy peritectic steel slabs produced by the No. 3 continuous caster at Baosteel,the physical properties of the original mold flux and the ...In order to solve the problem of the high surface longitudinal crack ratio of heavy peritectic steel slabs produced by the No. 3 continuous caster at Baosteel,the physical properties of the original mold flux and the optimized mold flux were compared in a comprehensive way by using analytical measures, such as a slag film heat-flow simulator, a thermowire molten flux crystallization tester and an X-ray diffractometer in the laboratory. The results reveal that one of the major reasons for the cracks is the poor heat transfer ability of the original mold flux. However, the optimized mold flux with a high basicity features a high crystallizing rate,low crystallization temperature and low heat-flow density. Therefore, the optimized mold flux is more suitable for casting peritectic steel by the heavy slab continuous caster. The test results show that the slabs produced by using the optimized mold flux had no surface longitudinal crack in four test casts, while the surface longitudinal crack ratio of the slabs produced by using the original mold flux was 5%. The optimized mold flux can effectively prevent slab surface longitudinal cracks from occurring.展开更多
An evaluation of the incidence of Crypticerya multicicatrices and Maconellicoccus hirsutus in Colombian Seaflower Biosphere Reserve in San Andrés, Providence and Santa Catalina islands, from mid-August to mid-Nov...An evaluation of the incidence of Crypticerya multicicatrices and Maconellicoccus hirsutus in Colombian Seaflower Biosphere Reserve in San Andrés, Providence and Santa Catalina islands, from mid-August to mid-November 2012 was made. 38 locations were sampled, and 34% of sites tested show an incidence of C. multicicatrices oscillating between a range of 80%-100%, 24% with 40%-80% of incidence, 18% between 10%-40% and 24% with a range of 0%-10%. The occurrence of M. hirsutus fluctuated between 0.5% and 17%. There were seven genera of ants associated C. multicicatrices and 94 hosts of this agriculturally important insect and we found high incidence of associated sooty mold in C. multicicatrices hosts. Observations also contained some developmental stages of C. multicatrices.展开更多
The mositure content inside the hermetic package of semiconductor device has been quantitatively measured by using in-site sensor technique and computer-aided-test system.The principle and apparatus for measurement ar...The mositure content inside the hermetic package of semiconductor device has been quantitatively measured by using in-site sensor technique and computer-aided-test system.The principle and apparatus for measurement are introduced.The results show good repeatability and consistency.This technology can be used as a standard test for controlling the moisture content within semiconductor device package.展开更多
An innovative, cost-effective, user-friendly and portable device (dew sensor) to directly detect condensation on glass surfaces was developed within the EC-VIDRIO project (contract No. EVK4-CT-2001-00045), aimed a...An innovative, cost-effective, user-friendly and portable device (dew sensor) to directly detect condensation on glass surfaces was developed within the EC-VIDRIO project (contract No. EVK4-CT-2001-00045), aimed at finding sustainable solutions to preserve ancient stained glass windows. The results of the research showed that the direct survey of condensation with the new sensor is more accurate and reliable than the traditional indirect microclimatic measurements. Since the construction of the first prototype, the dew sensor was developed further, continuously improved, validated in the laboratory and applied successfully on different surfaces at sites of interest in the field of Cultural Heritage; on the stained glass windows in the Saint Urbain Basilica of Troyes (France), Sainte Chapelle of Paris (France) and Cologne Cathedral (Germany); on stone walls in Petrarca's Tomb (Padua, Italy) and the Hagar Qim Temple (Malta). Now the sensor is being used in the Lascaux Caves (France). The newly built device was patented (PTC/EP2005/050665) and gave such interesting results that the Italian Ministry of University and Research financially supported a spin-off project that has lead to the creation of a new company (R.E.D.s.r.l.) in order to develop the prototype further and to produce the sensor at industrial scale.展开更多
Fiber reinforced polypropylene has been widely accepted as material for structural and engineering applications in recent years.Jute,Banana fibers etc.are the most common low cost,versatile,renewable and abundantly av...Fiber reinforced polypropylene has been widely accepted as material for structural and engineering applications in recent years.Jute,Banana fibers etc.are the most common low cost,versatile,renewable and abundantly available natural fibers which have biodegradable properties.All these fibers are versatile,renewable and most common agro based fibers that have enormous aspect due to their potentiality in composite manufacture.In comparison to other artificial fibers there are many advantages of natural fibers due to everyday applications such as,paperweight,suitcases,lampshades,helmets,and shower and bath units.Untreated and alkali treated banana fiber reinforced with Polypropylene matrix composite were fabricated with 10-25%loading of fiber by weight and were fabricated as Polypropylene Banana Composite(PPBC).Using melt mixing hot press molding technique these biodegradable composites were prepared.Different characteristics like morphologies and micro structural analysis of the composites were studied by Scanning electron microscope(SEM)and infrared spectroscopy instrument(IR).Due to the concept of group vibration infrared spectroscopy has the extensive application.Any kind of structural change such as addition or substitution of groups or atoms in a molecule may affect the relative mode of vibration of the group.This causes change in IR spectral band position,change in relative intensities and appearance of new bands and disappearance of any band and splitting of a single band into two or more bands.To increase the utility of fiber infrared spectroscopy can also be used.It deals with the interaction of infrared light with matter.The former can indicate the presence of functional groups qualitatively and the latter can provide a semi quantitative measure of their concentrations.On the other hand Electron Microscopy is most widely used to obtain information regarding the morphology of fiber surfaces,especially SEM(Scanning Electron Microscopy).Using SEM,it is easy to determine the differences of fiber surface topography after and before treatment,and hence the formation of fiber polymer composites.Fiber deboning was also observed for untreated and treated fiber pp matrix composite.The SEM can have a magnification range from a few times to several hundred thousand times.展开更多
High-moisture regains nature of cellulosic fibers considered one of the critical drawbacks for jute-based applications. To minimize this by developing better interfacial adhesion, a hydrophobic nonwoven wet-laid glass...High-moisture regains nature of cellulosic fibers considered one of the critical drawbacks for jute-based applications. To minimize this by developing better interfacial adhesion, a hydrophobic nonwoven wet-laid glass fiber sheet used <span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> woven jute fabric in this experiment. For this purpose, woven jute fabric </span><span style="font-family:;" "=""><span style="font-family:Verdana;">wa</span><span style="font-family:Verdana;">s </span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">categorized into untreated, silane, alkali, and alkali-silane combined treatment then compounded with the solution of polycaprolactone </span><span style="font-family:Verdana;">(PCL). Fabric</span></span><span style="font-family:Verdana;">ation of composites performed </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">following sandwich method based on differ</span><span style="font-family:Verdana;">ent hot-pressing time </span></span><span style="font-family:Verdana;">with</span><span style="font-family:Verdana;"> temperature for detecting a prominent fabrication parameter. Surface treated jute fibers characterized using FTIR spectro</span><span style="font-family:;" "=""><span style="font-family:Verdana;">sco</span><span style="font-family:Verdana;">py. Hence, the mechanical and thermal properties of composites were investiga</span><span style="font-family:Verdana;">ted to find the consequence of chemical treatments into woven jute fabric. Alkali-silane combined chemical treatments resulting in improved 48.38% of tensile strength over untreated optimized composites. Scanning electron microscope (SEM) used for displaying interfacial adhesion between fiber and polymer matrix. Besides, further investigation demonstrated due to the combined chemical treatment of alkali-silane optimized composites significantly enhanced the thermogravimetric (TGA) stability in contrast to other composites.</span></span>展开更多
基金financially supported by the National Natural Science Foundation of China (41201085)the 100 Talents Program of the Chinese Academy of Sciences
文摘Dew is an important supplement water source in arid and semi-arid areas. In order to determine the dew formation on different kinds of soils associated with various shrub species and microhabitats, we performed measurement of accumulated dew formation amount and duration in October 2009 in a revegetation-stabilized arid desert ecosystem in Shapotou area, northern China. The results indicated that the accumulated dew formation amount was four times larger at open spaces as compared to under the canopy, and it was nearly twice as much under living Artemisia ordosica plants(L.A.) as compared to under living Caragana korshinskii plants(L.C.). The opposite characteristics were found for dew duration between different microhabitats. Dew amounts at different vertical heights around the shrub stands were in the order of 50 cm above the canopy〉the canopy edge〉under the canopy. Dew amount continued to increase after dawn, and the proportion of average accumulated dew amount after dawn accounting for the average maximum amount increased from above the canopy to under the canopy. Dew formation duration after sunrise accounted for more than 50% of the total formation duration during the day time. Contrary to the distribution characteristics of dew amount, dew duration after dawn and total dew formation duration during the day time were both highest under the canopy, followed by at the canopy edge and then at 50 cm above the canopy. The portion of dew duration after dawn accounting for the total dew duration during the day time increased from above the canopy to under the canopy. From these results, we may conclude that dew availability as a supplemental water resource for improving the microhabitats in water-limited arid ecosystems is position dependent especially for the plant microhabitats at different stands layers.
文摘The fact that the amount of the mold flux components differs at differentlocations on the cracking surface indicates that the longitudinal surface cracks are initiallyformed in the mold and are enlarged in the secondary cooling zone. Based on the hot ductilitymeasurement of two typical container used steels, it is known that the steels are in severeembrittlement state in the temperature range of 825-775 deg C. By means of increasing Cr/Ni platingthickness on the upper part of the mold, reducing mold heat flux, adopting new secondary coolingpattern, etc., the occurrence of the surface longitudinal cracks on the steel CC (continuouscasting) slabs has been significantly reduced.
基金Supported by NationalNatural Science FoundationCouncil of the People’s Republic of China (20490224)
文摘The design of the cooling system of injection molds directly affects both productivity and the quality of the final part. Using the cooling process CAE system to instruct the mold design, the efficiency and quality of design can be improved greatly. At the same time, it is helpful to confirm the cooling system structure and optimize the process conditions. In this paper, the 3D surface model of mold cavity is used to replace the middle-plane model in the simulation by Boundary Element Method, which break the bottleneck of the application of the injection molding simulation softwares base on the middle-plane model. With the improvements of this paper, a practical and commercial simulation software of injection molding cooling process named as HsCAE3D6.0 is developed.
文摘On the basis of the comprehensive analysis about the automatic generation of the injection mold parting surface, the parting surface design method which introduces knowledge and case-based reasoning (CBR) into the computer-aided design is described by combining with the actual characteristic in injection mold design, and the design process of case-based reasoning method is also given. A case library including the information of parting surface is built with the index of main shape features, The automatic design of the mold parting surface is realized combined with the forward-reasoning method and the similarity solution procedure. The rule knowledge library is also founded including the knowledge, principles and experiences for parting surface design. An example is used to show the validity of the method, and the quality and the efficiency of the mold design are improved.
文摘The effects of the wavelength and orientation of machined grooves on a mold surface, casting speed, and melt superheat on the formation of surface marks on as-cast ingots were studied with an immersion casting tester and copper mold chill blocks. The mold surface topographies included a polished smooth surface, and those with machined unidirectional parallel contoured grooves oriented either parallel (vertical) or perpendicular (horizontal) to the casting direction. The unidirectional grooves were 0.232 mm deep with wavelength or spacing between 1 and 15 mm. The casting speed and melt superheat were between 1 and 200 mm/s, and 10 and 50 K, respectively. Two primary types of surface marks were observed on ingots cast with the copper mold with smooth surface topography, namely the finer and closely spaced ripples (Type I), and the widely spaced but coarser laps (Type II). The latter were more prevalent at the higher casting speeds and melt superheats. Qualitatively, formation of both types of surface marks on the as-cast ingots of the aluminum alloy 3003 appeared to be alleviated by increase in casting speed and melt superheat, and by the use of molds with grooved surface topography. In fact, casting with a mold surface with 1 mm spaced grooves that are perpendicular to the casting direction eliminated the formation of surface marks at casting speeds greater than 1 mm/s. It also improved the uniformity of the ingot subsurface microstructure and eliminated the associated subsurface segregation.
文摘In recent years, high precision geometric shape, surface roughness, and cost reduction are required for large glass component molding processes. In this research, the polishing process of stainless steel molding dies used to form thin glass components is investigated. The surface roughness of the polished stainless steel molding die surface is below Rz = 200 nm (P-V) at 15 h polishing with 0.5 % alumina polishing liquid. In the case of polishing process with only the weight of molding die and a polishing pressure of 0.5 kPa, polishing times are approximately 60 h and 20 h, respectively. Final surface roughness polished stainless steel molding die surface with pressure of 0.5 kPa is Rz = 7 nm (P-V), rms -- 1.6 nm and Ra = 1.4 nm. In a thin glass component manufacturing method, "slumping method", surface roughness before glass forming is rms = 0.7 nm and Ra = 0.6 nm, and after is rms = 0.7 nm and Ra = 0.6 nm. Therefore, there were no observable changes their surface roughness.
基金financially supported by the Program for New Century Excellent Talents in University(No.NCET-13-0229)the National Science&Technology Key Projects of Numerical Control(No.2012ZX04010-031,2012ZX0412-011)Natural Science Foundation of Hubei Province,China(2011CDB279)
文摘Deformation of casting during the solidification process has puzzled many engineers and scientists for years. In order to attain the goal of near-net forming by casting, numerical simulation is a powerful tool. Traditional methods compute the thermal stress of both the casting and the mold. This method suffers the problem of massive calculation and failure of convergence. This paper proposes an improved Mold Surface Element Method, the main idea of which is to use the surface elements instead of body elements to express the interactions between the casting and the mold. The proposed method shows a high computation efficiency and provides satisfactory precision for engineering. Two practical casting products were used to verify the proposed method. The simulated results agree well with those observed in practical products. The proposed method is believed to benefit production practice and to provide theoretical guidance.
基金Project supported by the Natural Science Foundation of Shaanxi Province(Grant No.2006E112)
文摘Polishing is an important finishing process in die and mold manufacturing. Hand polishing takes long time and much labor. Efforts are made to automate the polishing process while keeping accuracy. Recently grinding centers have been developed, which are used for free surface polishing in the present work. The new polishing technique applies the same cutting locus as used in the cutting process to remove only cusp height effectively, keeping the form accuracy generated in the cutting process.
文摘Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing the number of input factors and to include all possible interactions. For this purpose, two-stage experimentation is suggested: a factor screening stage and Response Surface optimization stage. In screening stage Taguchi 3 level experimental design is used to classify the input parameters as significant and non-significant factors. Eight input variables were classified into 3 non-significant and 5 significant factors using this screening stage. Thus for the Response Surface optimization stage: instead of doing 160 experiments in Central Composite, 56 are only needed after the screening stage in half Central Composite Design. The best subset and regression model fitting tools in addition to model verification using randomly selected input setting were used to select a model for predicting residual stresses with a verified Root Mean Square Error (RSME) of nearly 0.93 MPa.
基金supported by the National Natural Science Foundation of China(No.51275269)the National Science and Technology Major Projects(Nos.2012ZX04012011 and 2011ZX04001071)
文摘A 3D mathematical model was proposed to simulate the mold filling process in high-pressure die casting(HPDC) to improve accuracy considering the surface tension. Piecewise liner interface calculation(PLIC) and volume of fluid(VOF) methods were used to construct the pattern of the liquid interface. A coupled levelset and VOF method(CLSVOF) was proposed to capture the interface pattern and obtain its normal vector. A continuum surface force(CSF) model was used to consider the surface tension. Two water analogy experiments were carried out using the proposed model. Simulation and experimental results were analyzed and compared; and the effects of surface tension were also discussed. The simulation results agreed well with the experiments and the simulation accuracy was an improvement on interface geometries, liquid flows, and gas entrapments.
基金Funded by the China Scholarship Council and Wisconsin Institute for Discovery(WID)the Scientific Research Staring Foundation,Fujian University of Technology,China(No.GY-Z13028)+1 种基金the Programfor New Century Excellent Talents in Fujian Province University(NCETFJ-2010)the Research Fund for Fujian Provincial University(JK-2010038)
文摘The in vitro degradation rate of polyanhydride (poly(sebacic acid), diacetoxy terminated), also known as PSADT, was investigated. PSADT tablets with a circular cross-section were formed using a compression molding device, and then immersed into phosphate buffer saline (PBS) for in vitro degradation experiments. The mechanisms of degradation and the degradation rate were characterized by the change in molecular weight and reduction in specimen mass. In addition, the effects of processing temperature and the geometry of the formed PSADT tablets on the rate of degradation were studied. The surface morphology at different degradation times was observed by scanning electron microscopy (SEM). The experimental results showed that PSADT exhibited sur^hce erosion due to the fact that near zero-order degradation kinetics was observed during its degradation process. Moreover, it is found that the geometry of tablets played an important role on the rate of degradation, while the processing temperature had no significant effect on the PSADT degradation rate.
文摘The potential of a 3D FDM (Finite Difference Method) computer code was presented, in prediction of flow patterns by modeling the mold filling phenomena through different gating systems. In this code, improvements and modifications were made on the original SOLA VOF and Donor Acceptor algorithms. A more accurate solution procedure for handling free surfaces is developed in order to describe the flows through complicated gating designs. A block casting of 200?mm×200?mm×50?mm with two different gating designs was chosen as the verifying problem. Water analog studies are carried out on these two gating designs. The comparison indicates that computer simulation could be a powerful tool in shaping gating systems.
文摘In order to solve the problem of the high surface longitudinal crack ratio of heavy peritectic steel slabs produced by the No. 3 continuous caster at Baosteel,the physical properties of the original mold flux and the optimized mold flux were compared in a comprehensive way by using analytical measures, such as a slag film heat-flow simulator, a thermowire molten flux crystallization tester and an X-ray diffractometer in the laboratory. The results reveal that one of the major reasons for the cracks is the poor heat transfer ability of the original mold flux. However, the optimized mold flux with a high basicity features a high crystallizing rate,low crystallization temperature and low heat-flow density. Therefore, the optimized mold flux is more suitable for casting peritectic steel by the heavy slab continuous caster. The test results show that the slabs produced by using the optimized mold flux had no surface longitudinal crack in four test casts, while the surface longitudinal crack ratio of the slabs produced by using the original mold flux was 5%. The optimized mold flux can effectively prevent slab surface longitudinal cracks from occurring.
文摘An evaluation of the incidence of Crypticerya multicicatrices and Maconellicoccus hirsutus in Colombian Seaflower Biosphere Reserve in San Andrés, Providence and Santa Catalina islands, from mid-August to mid-November 2012 was made. 38 locations were sampled, and 34% of sites tested show an incidence of C. multicicatrices oscillating between a range of 80%-100%, 24% with 40%-80% of incidence, 18% between 10%-40% and 24% with a range of 0%-10%. The occurrence of M. hirsutus fluctuated between 0.5% and 17%. There were seven genera of ants associated C. multicicatrices and 94 hosts of this agriculturally important insect and we found high incidence of associated sooty mold in C. multicicatrices hosts. Observations also contained some developmental stages of C. multicatrices.
文摘The mositure content inside the hermetic package of semiconductor device has been quantitatively measured by using in-site sensor technique and computer-aided-test system.The principle and apparatus for measurement are introduced.The results show good repeatability and consistency.This technology can be used as a standard test for controlling the moisture content within semiconductor device package.
文摘An innovative, cost-effective, user-friendly and portable device (dew sensor) to directly detect condensation on glass surfaces was developed within the EC-VIDRIO project (contract No. EVK4-CT-2001-00045), aimed at finding sustainable solutions to preserve ancient stained glass windows. The results of the research showed that the direct survey of condensation with the new sensor is more accurate and reliable than the traditional indirect microclimatic measurements. Since the construction of the first prototype, the dew sensor was developed further, continuously improved, validated in the laboratory and applied successfully on different surfaces at sites of interest in the field of Cultural Heritage; on the stained glass windows in the Saint Urbain Basilica of Troyes (France), Sainte Chapelle of Paris (France) and Cologne Cathedral (Germany); on stone walls in Petrarca's Tomb (Padua, Italy) and the Hagar Qim Temple (Malta). Now the sensor is being used in the Lascaux Caves (France). The newly built device was patented (PTC/EP2005/050665) and gave such interesting results that the Italian Ministry of University and Research financially supported a spin-off project that has lead to the creation of a new company (R.E.D.s.r.l.) in order to develop the prototype further and to produce the sensor at industrial scale.
文摘Fiber reinforced polypropylene has been widely accepted as material for structural and engineering applications in recent years.Jute,Banana fibers etc.are the most common low cost,versatile,renewable and abundantly available natural fibers which have biodegradable properties.All these fibers are versatile,renewable and most common agro based fibers that have enormous aspect due to their potentiality in composite manufacture.In comparison to other artificial fibers there are many advantages of natural fibers due to everyday applications such as,paperweight,suitcases,lampshades,helmets,and shower and bath units.Untreated and alkali treated banana fiber reinforced with Polypropylene matrix composite were fabricated with 10-25%loading of fiber by weight and were fabricated as Polypropylene Banana Composite(PPBC).Using melt mixing hot press molding technique these biodegradable composites were prepared.Different characteristics like morphologies and micro structural analysis of the composites were studied by Scanning electron microscope(SEM)and infrared spectroscopy instrument(IR).Due to the concept of group vibration infrared spectroscopy has the extensive application.Any kind of structural change such as addition or substitution of groups or atoms in a molecule may affect the relative mode of vibration of the group.This causes change in IR spectral band position,change in relative intensities and appearance of new bands and disappearance of any band and splitting of a single band into two or more bands.To increase the utility of fiber infrared spectroscopy can also be used.It deals with the interaction of infrared light with matter.The former can indicate the presence of functional groups qualitatively and the latter can provide a semi quantitative measure of their concentrations.On the other hand Electron Microscopy is most widely used to obtain information regarding the morphology of fiber surfaces,especially SEM(Scanning Electron Microscopy).Using SEM,it is easy to determine the differences of fiber surface topography after and before treatment,and hence the formation of fiber polymer composites.Fiber deboning was also observed for untreated and treated fiber pp matrix composite.The SEM can have a magnification range from a few times to several hundred thousand times.
文摘High-moisture regains nature of cellulosic fibers considered one of the critical drawbacks for jute-based applications. To minimize this by developing better interfacial adhesion, a hydrophobic nonwoven wet-laid glass fiber sheet used <span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> woven jute fabric in this experiment. For this purpose, woven jute fabric </span><span style="font-family:;" "=""><span style="font-family:Verdana;">wa</span><span style="font-family:Verdana;">s </span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">categorized into untreated, silane, alkali, and alkali-silane combined treatment then compounded with the solution of polycaprolactone </span><span style="font-family:Verdana;">(PCL). Fabric</span></span><span style="font-family:Verdana;">ation of composites performed </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">following sandwich method based on differ</span><span style="font-family:Verdana;">ent hot-pressing time </span></span><span style="font-family:Verdana;">with</span><span style="font-family:Verdana;"> temperature for detecting a prominent fabrication parameter. Surface treated jute fibers characterized using FTIR spectro</span><span style="font-family:;" "=""><span style="font-family:Verdana;">sco</span><span style="font-family:Verdana;">py. Hence, the mechanical and thermal properties of composites were investiga</span><span style="font-family:Verdana;">ted to find the consequence of chemical treatments into woven jute fabric. Alkali-silane combined chemical treatments resulting in improved 48.38% of tensile strength over untreated optimized composites. Scanning electron microscope (SEM) used for displaying interfacial adhesion between fiber and polymer matrix. Besides, further investigation demonstrated due to the combined chemical treatment of alkali-silane optimized composites significantly enhanced the thermogravimetric (TGA) stability in contrast to other composites.</span></span>