Extensive research has been conducted in an attempt to develop reliable models or indicators for determining product quality based on process information. Relationships between part quality and process variables such as nozzle temperature, hydraulic pressure and cavity pressure have been established using methods such as statistical process control, regression analysis and artificial neural networks. Ideally, these models would be used to determine part quality without direct inspection. If a level of confidence equivalent to that obtained by traditional methods (e.g., SQC) could be achieved, “quality by inspection” could be eliminated. Two drawbacks to these models are that they are specific to the machine/mold/polymer (M/M/P) combination being studied and they require a significant amount of “up-front” process data for model formulation. A method for “normalizing” pressure data obtained from a range of machine/mold/polymer configurations to yield essentially one curve or attribute denoting acceptable part quality would greatly enhance the utility of P-t data in a manufacturing setting. The objective of the present research is to examine the effects on the temporal cavity pressure due to changes in the mold geometry and to investigate methods for obtaining generic pressure data for various geometries. Cavity pressure data was collected using geometric inserts fitted into a standard ASTM tensile specimen cavity. The pressure data was analyzed to determine the correlation between cavity pressure and part quality for three part geometries studied. A discussion of the utility of the pressure is presented and an attempt is made to find a geometry independent cavity pressure attribute for use in determining part quality.
{"title":"Cavity Pressure and Part Quality in the Injection Molding Process","authors":"D. C. Angstadt, J. Coulter","doi":"10.1115/imece1999-1249","DOIUrl":"https://doi.org/10.1115/imece1999-1249","url":null,"abstract":"\u0000 Extensive research has been conducted in an attempt to develop reliable models or indicators for determining product quality based on process information. Relationships between part quality and process variables such as nozzle temperature, hydraulic pressure and cavity pressure have been established using methods such as statistical process control, regression analysis and artificial neural networks. Ideally, these models would be used to determine part quality without direct inspection. If a level of confidence equivalent to that obtained by traditional methods (e.g., SQC) could be achieved, “quality by inspection” could be eliminated. Two drawbacks to these models are that they are specific to the machine/mold/polymer (M/M/P) combination being studied and they require a significant amount of “up-front” process data for model formulation. A method for “normalizing” pressure data obtained from a range of machine/mold/polymer configurations to yield essentially one curve or attribute denoting acceptable part quality would greatly enhance the utility of P-t data in a manufacturing setting. The objective of the present research is to examine the effects on the temporal cavity pressure due to changes in the mold geometry and to investigate methods for obtaining generic pressure data for various geometries. Cavity pressure data was collected using geometric inserts fitted into a standard ASTM tensile specimen cavity. The pressure data was analyzed to determine the correlation between cavity pressure and part quality for three part geometries studied. A discussion of the utility of the pressure is presented and an attempt is made to find a geometry independent cavity pressure attribute for use in determining part quality.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114676255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fused deposition based solid freeform fabrication technique allows manufacturing of potential functional preforms for subsequent Resin Transfer Molding. In this study, the transport property (permeability) of solid freeform fabricated porous preform geometries are investigated. Specifically the effect of pore geometry and network on the permeability is sought. Wet (saturated) permeability experiments were performed for various pore geometries with different viscosity liquids. For all fluids and preform structures investigated in this study, the porous flow exhibited Darcian behavior. The permeability is affected by changes in order of magnitude of fluid viscosity, the effect considerably significant in low porosity preforms. Current work concentrates on dry permeability measurement and development of numerical permeability models for ordered pore geometries (as produced through SFF) that will be compared with experimental results.
{"title":"Characterization of Permeability for Solid Freeform Fabricated Porous Structures","authors":"M. Erdal, Levent Ertoz, S. Güçeri","doi":"10.1115/imece1999-1254","DOIUrl":"https://doi.org/10.1115/imece1999-1254","url":null,"abstract":"\u0000 Fused deposition based solid freeform fabrication technique allows manufacturing of potential functional preforms for subsequent Resin Transfer Molding. In this study, the transport property (permeability) of solid freeform fabricated porous preform geometries are investigated. Specifically the effect of pore geometry and network on the permeability is sought. Wet (saturated) permeability experiments were performed for various pore geometries with different viscosity liquids. For all fluids and preform structures investigated in this study, the porous flow exhibited Darcian behavior. The permeability is affected by changes in order of magnitude of fluid viscosity, the effect considerably significant in low porosity preforms. Current work concentrates on dry permeability measurement and development of numerical permeability models for ordered pore geometries (as produced through SFF) that will be compared with experimental results.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"254 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130421224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The mechanism of porosity nucleation in pressure infiltration casting of metal matrix composites is investigated. Five interfacial configurations are considered for a variety of matrix/reinforcement systems. Interfaces with negative curvature such as cavity are found to be potential sites for porosity formation. The Al/Al2O3 system is most susceptible to porosity nucleation for the systems considered. Appropriate matrix alloying such as Mg in Al/Al2O3 system, and Mg and Cu in Al/SiC system and reinforcement coating such as Cu coating on SiC, could be effective for suppressing porosity formation.
{"title":"Effect of Matrix Alloying and Reinforcement Coating on Porosity Nucleation in Metal-Matrix Composites","authors":"O. Ilegbusi, Jijin Yang","doi":"10.1115/imece1999-1250","DOIUrl":"https://doi.org/10.1115/imece1999-1250","url":null,"abstract":"\u0000 The mechanism of porosity nucleation in pressure infiltration casting of metal matrix composites is investigated. Five interfacial configurations are considered for a variety of matrix/reinforcement systems. Interfaces with negative curvature such as cavity are found to be potential sites for porosity formation. The Al/Al2O3 system is most susceptible to porosity nucleation for the systems considered. Appropriate matrix alloying such as Mg in Al/Al2O3 system, and Mg and Cu in Al/SiC system and reinforcement coating such as Cu coating on SiC, could be effective for suppressing porosity formation.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116020620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The kinetics of reaction-bonded SiC infiltration process utilizing Si-Al matrix has been investigated theoretically using a modified Washburn model. The effect of alloy composition and temperature on infiltration has been quantified. The resulting characteristics depend on alloy composition of the secondary metallic phase. Specifically, aluminum generally suppresses the infiltration rate. Increasing the temperature enhances both the infiltration capacity and reaction rate.
{"title":"Effect of Si-Al Alloy on Kinetics of Reaction-Bonded SiC Infiltration Process","authors":"O. Ilegbusi, Jijin Yang","doi":"10.1115/imece1999-1255","DOIUrl":"https://doi.org/10.1115/imece1999-1255","url":null,"abstract":"\u0000 The kinetics of reaction-bonded SiC infiltration process utilizing Si-Al matrix has been investigated theoretically using a modified Washburn model. The effect of alloy composition and temperature on infiltration has been quantified. The resulting characteristics depend on alloy composition of the secondary metallic phase. Specifically, aluminum generally suppresses the infiltration rate. Increasing the temperature enhances both the infiltration capacity and reaction rate.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117039136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Phase segregation during the mold filling of semisolid slurry (Sn-15%Pb) is numerically investigated under non-isothermal conditions. The effects of operating parameters on the phase segregation including inlet velocity, initial solid fraction, heat transfer rate, mold geometry are considered. The semi-solid slurry is considered a non-Newtonian fluid below a critical solid fraction (fcr) and a viscoplastic medium saturated with liquid phase above the critical solid fraction. A group of particles are introduced at the mold inlet and phase segregation is studied by following the trajectories of these particles. The sharp property change at the slurry air interface is resolved with Van Leer numerical method. It is found that phase segregation is significantly affected by processing parameter. The segregation decreases with high inlet velocity, low heat transfer rate from the mold wall and cylindrical mold geometry.
{"title":"Prediction of Phase Segregation During Mold Filling of Semi-Solid Slurries","authors":"M. D. Mat, O. Ilegbusi","doi":"10.1115/imece1999-1257","DOIUrl":"https://doi.org/10.1115/imece1999-1257","url":null,"abstract":"\u0000 Phase segregation during the mold filling of semisolid slurry (Sn-15%Pb) is numerically investigated under non-isothermal conditions. The effects of operating parameters on the phase segregation including inlet velocity, initial solid fraction, heat transfer rate, mold geometry are considered. The semi-solid slurry is considered a non-Newtonian fluid below a critical solid fraction (fcr) and a viscoplastic medium saturated with liquid phase above the critical solid fraction. A group of particles are introduced at the mold inlet and phase segregation is studied by following the trajectories of these particles. The sharp property change at the slurry air interface is resolved with Van Leer numerical method. It is found that phase segregation is significantly affected by processing parameter. The segregation decreases with high inlet velocity, low heat transfer rate from the mold wall and cylindrical mold geometry.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123802561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on a linear stability theory for liquid jets, the design of a droplet generator system is presented for freeform fabrication. The linear stability theory of forming droplets is first reviewed and its suitability to the present droplet deposition system is then discussed. The analytical formulae for predicting droplet size and break-up length at optimal conditions are developed. Based on the present formulation, a droplet generator is designed and built to make wax and tin alloy droplets. Experiments have been conducted at a wide range of jet velocities, frequencies, and droplet sizes. Good agreements are found between the analytical predictions based on the linear theory and experimental results. It has also been found that using the present design and procedure recommended, the droplet sizes can be controlled having a size deviation of less than 3 % and the variation of the deposited layer can be managed within 3% of its width deposited.
{"title":"Design and Operation of a Droplet Deposition System for Freeform Fabrication of Metal Parts","authors":"A. Tseng, M. H. Lee, B. Zhao","doi":"10.1115/1.1286187","DOIUrl":"https://doi.org/10.1115/1.1286187","url":null,"abstract":"\u0000 Based on a linear stability theory for liquid jets, the design of a droplet generator system is presented for freeform fabrication. The linear stability theory of forming droplets is first reviewed and its suitability to the present droplet deposition system is then discussed. The analytical formulae for predicting droplet size and break-up length at optimal conditions are developed. Based on the present formulation, a droplet generator is designed and built to make wax and tin alloy droplets. Experiments have been conducted at a wide range of jet velocities, frequencies, and droplet sizes. Good agreements are found between the analytical predictions based on the linear theory and experimental results. It has also been found that using the present design and procedure recommended, the droplet sizes can be controlled having a size deviation of less than 3 % and the variation of the deposited layer can be managed within 3% of its width deposited.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"197 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117096312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Subcooled boiling of water in a vertical pipe is numerically investigated. The mathematical model involves solution of transport equations for vapor and liquid phase separately. Turbulence model considers the turbulence production and dissipation by the motion of the bubbles. The radial and axial void fractions, temperature and velocity profiles in the pipe are calculated. The estimated results are compared to experimental data available in the literature. It is found that while present study satisfactorily agrees with experimental data in the literature, it improves the prediction at lower void fractions.
{"title":"Application of a Bubble-Induced Turbulence Model to Subcooled Boiling in a Vertical Pipe","authors":"M. D. Mat, Yuksel Kaplan, O. Ilegbusi","doi":"10.1115/imece1999-1253","DOIUrl":"https://doi.org/10.1115/imece1999-1253","url":null,"abstract":"\u0000 Subcooled boiling of water in a vertical pipe is numerically investigated. The mathematical model involves solution of transport equations for vapor and liquid phase separately. Turbulence model considers the turbulence production and dissipation by the motion of the bubbles. The radial and axial void fractions, temperature and velocity profiles in the pipe are calculated. The estimated results are compared to experimental data available in the literature. It is found that while present study satisfactorily agrees with experimental data in the literature, it improves the prediction at lower void fractions.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131260499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The study of particle filtration in resin transfer molding of liquid preceramic polymer (PCP) based ceramic composites with filler particles is the topic of our current research, in order to prevent particle filtering during impregnation and to achieve a uniform particle distribution within the composite. This study targets an experimental analysis of filtration that will be coupled to previously developed filtration models. For reliable filtration data, the properties of the particle-PCP suspension must be known (predictable) and the suspension quality reproducible. This paper presents the initial stage of the experimental work, which consists of standardization of particle-polymer suspension preparation and its characterization. A methodology for optimal (homogeneous suspension with low agglomeration) steric stabilization of polymer / SiC particle suspensions is presented. The results Blackglas™1 preceramic of the characterization of the suspensions through visual inspection (SEM) and rheological measurements are reported. With the achievement of well-dispersed, low viscosity suspensions with reproducible properties, our current work is in the adaptation of electrostatic spraying and laser particle counting technology for the detection of particle size distribution and concentration to be used in subsequent filtration experiments.
{"title":"Experimental Analysis of Particle Filtration in Resin Transfer Molding of Preceramic Polymer Based Ceramic Composites","authors":"M. Erdal, L. A. Ambrosoni","doi":"10.1115/imece1999-1251","DOIUrl":"https://doi.org/10.1115/imece1999-1251","url":null,"abstract":"\u0000 The study of particle filtration in resin transfer molding of liquid preceramic polymer (PCP) based ceramic composites with filler particles is the topic of our current research, in order to prevent particle filtering during impregnation and to achieve a uniform particle distribution within the composite. This study targets an experimental analysis of filtration that will be coupled to previously developed filtration models. For reliable filtration data, the properties of the particle-PCP suspension must be known (predictable) and the suspension quality reproducible. This paper presents the initial stage of the experimental work, which consists of standardization of particle-polymer suspension preparation and its characterization. A methodology for optimal (homogeneous suspension with low agglomeration) steric stabilization of polymer / SiC particle suspensions is presented. The results Blackglas™1 preceramic of the characterization of the suspensions through visual inspection (SEM) and rheological measurements are reported. With the achievement of well-dispersed, low viscosity suspensions with reproducible properties, our current work is in the adaptation of electrostatic spraying and laser particle counting technology for the detection of particle size distribution and concentration to be used in subsequent filtration experiments.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128508861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-10-01DOI: 10.1106/PACL-R7AP-41WL-23HQ
Alan M. Tom, A. Kikuchi, J. Coulter
The current investigation focused on contributing to the development of a novel injection molding process by attempting to understand the scientific relationship that exist between the applied vibrational parameters involved in this process and the effect it has on final product polymeric characterization. Although previous and current attempts at understanding the connection between applied oscillatory or vibrational motion to an injection molding process has shown positive quantitative advantages to final product properties, there still exists a void in the scientific explanation on a molecular level linking these effects. This experimental study, in particular, involved an evaluation on a range of processing conditions applied to Polystyrene and the effects it produced on resultant product quality and polymer properties. Optimal control and mechanical vibrational molding conditions were obtained for Polystyrene. As a result of this, optimal opportunities for initial commercial utilization of the technology can be proposed.
{"title":"An Experimental Evaluation of Vibration-Assisted Injection Molding During Manufacturing","authors":"Alan M. Tom, A. Kikuchi, J. Coulter","doi":"10.1106/PACL-R7AP-41WL-23HQ","DOIUrl":"https://doi.org/10.1106/PACL-R7AP-41WL-23HQ","url":null,"abstract":"\u0000 The current investigation focused on contributing to the development of a novel injection molding process by attempting to understand the scientific relationship that exist between the applied vibrational parameters involved in this process and the effect it has on final product polymeric characterization. Although previous and current attempts at understanding the connection between applied oscillatory or vibrational motion to an injection molding process has shown positive quantitative advantages to final product properties, there still exists a void in the scientific explanation on a molecular level linking these effects. This experimental study, in particular, involved an evaluation on a range of processing conditions applied to Polystyrene and the effects it produced on resultant product quality and polymer properties. Optimal control and mechanical vibrational molding conditions were obtained for Polystyrene. As a result of this, optimal opportunities for initial commercial utilization of the technology can be proposed.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133997673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-10-01DOI: 10.1106/DAD5-PNGG-U87B-08Y5
D. Kazmer, D. Hatch
Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or system design has been universally accepted, and molding systems continue to produce defective components during production. The capability of the injection molding process is limited by the thermal and flow dynamics of the heated polymer melt. This paper discusses some of the difficulties posed by complex and distributed nature of the injection molding process. The flow and thermal dynamics of the process are analyzed with respect to transport and rheology. Then, two novel processing methods are described to enable in-cycle flow, pressure, and thermal control. Simulation and experimental results demonstrate effectiveness of these innovations to increase the consistency and flexibility in polymer processing. Such system design changes simplify the requisite control structures while improving the process robustness and productivity.
{"title":"Towards Controllability of Injection Molding","authors":"D. Kazmer, D. Hatch","doi":"10.1106/DAD5-PNGG-U87B-08Y5","DOIUrl":"https://doi.org/10.1106/DAD5-PNGG-U87B-08Y5","url":null,"abstract":"\u0000 Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or system design has been universally accepted, and molding systems continue to produce defective components during production. The capability of the injection molding process is limited by the thermal and flow dynamics of the heated polymer melt.\u0000 This paper discusses some of the difficulties posed by complex and distributed nature of the injection molding process. The flow and thermal dynamics of the process are analyzed with respect to transport and rheology. Then, two novel processing methods are described to enable in-cycle flow, pressure, and thermal control. Simulation and experimental results demonstrate effectiveness of these innovations to increase the consistency and flexibility in polymer processing. Such system design changes simplify the requisite control structures while improving the process robustness and productivity.","PeriodicalId":410594,"journal":{"name":"The Science, Automation, and Control of Material Processes Involving Coupled Transport and Rheology Changes","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130614403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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