Prasanth Ambady, Bingfeng Fan, D. Hatch, D. Kazmer
Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or process 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 develops a fundamental approach to process design for optimal mold cooling. Specifically, a viscoelastic constitutive model is utilized with process and quality models to develop theoretical and feasible limits for mold cooling. The analysis drives the development of a composite thermal structure consisting of 1) a thin layer with high density and specific heat, 2) a thin layer with low thermal conductivity, and 3) a conventional mold base with high thermal diffusivity. When pre-heated via gas convection, the resulting process enables isothermal mold-filling and improved polymer solidification. Numerical results indicate that the proposed system will reduce residual stress by 30% compared to conventional molding for equivalent cycle times.
{"title":"Process Design for Optimal Mold Cooling","authors":"Prasanth Ambady, Bingfeng Fan, D. Hatch, D. Kazmer","doi":"10.1115/imece2000-1226","DOIUrl":"https://doi.org/10.1115/imece2000-1226","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 process 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 develops a fundamental approach to process design for optimal mold cooling. Specifically, a viscoelastic constitutive model is utilized with process and quality models to develop theoretical and feasible limits for mold cooling. The analysis drives the development of a composite thermal structure consisting of 1) a thin layer with high density and specific heat, 2) a thin layer with low thermal conductivity, and 3) a conventional mold base with high thermal diffusivity. When pre-heated via gas convection, the resulting process enables isothermal mold-filling and improved polymer solidification. Numerical results indicate that the proposed system will reduce residual stress by 30% compared to conventional molding for equivalent cycle times.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125938953","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}
Recently developed aluminum alloys show significant potential as injection mold materials for their ability to cool plastic parts faster than steel. These alloys maintain more uniform mold temperatures that can have significant effects in reducing post-molding shrinkage. Commercially available software can be used to predict the global shrinkage in a part. However, none of the currently available software predicts localized sink mark formation. In the present work, temperature and pressure histories from a three-dimensional molding analysis using C-Mold™ are used to determine the initial conditions for a sequentially coupled thermal and structural finite element analysis using ANSYS™. The thermal conductivity, density and specific heat of the polymer are input as temperature dependent properties. The polymer is modeled as a temperature dependent elastic material. Correlations made between numerical and experimental data for sink mark depths in parts molded in P-20 steel and QE-7™ aluminum alloy molds validate the use of the sink mark simulation method. Numerical comparison of sink mark depths for parts molded in aluminum alloy and steel molds show that aluminum alloys reduce sink mark depths in molded parts.
{"title":"Analysis of Sink Marks for Plastic Parts Molded in Steel and Aluminum Alloy Molds","authors":"N. Iyer, K. Ramani","doi":"10.1115/imece2000-1224","DOIUrl":"https://doi.org/10.1115/imece2000-1224","url":null,"abstract":"\u0000 Recently developed aluminum alloys show significant potential as injection mold materials for their ability to cool plastic parts faster than steel. These alloys maintain more uniform mold temperatures that can have significant effects in reducing post-molding shrinkage. Commercially available software can be used to predict the global shrinkage in a part. However, none of the currently available software predicts localized sink mark formation. In the present work, temperature and pressure histories from a three-dimensional molding analysis using C-Mold™ are used to determine the initial conditions for a sequentially coupled thermal and structural finite element analysis using ANSYS™. The thermal conductivity, density and specific heat of the polymer are input as temperature dependent properties. The polymer is modeled as a temperature dependent elastic material.\u0000 Correlations made between numerical and experimental data for sink mark depths in parts molded in P-20 steel and QE-7™ aluminum alloy molds validate the use of the sink mark simulation method. Numerical comparison of sink mark depths for parts molded in aluminum alloy and steel molds show that aluminum alloys reduce sink mark depths in molded parts.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128152259","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}
After a well-focused research effort over the past quarter of a century, CAE for injection molding has become a common engineering tool used widely in industrial practice. Today, part and mold designers readily make use of CAE software tools to make rational design decisions based on scientific principles rather than solely on prior experiences. While the common goal of the industry is to produce plastic parts anywhere in the world at the lowest cost, with the best quality and fastest speed to market, a missing link in an integrated production system seems to lie in the ability at the shop floor to control the molding process automatically and adaptively without compromising part quality. As the IT (Information Technologies) and Web-based engineering continue to strive, the injection molding industry would benefit immensely to achieve its goals. This paper discusses some issues on technical challenges and opportunities.
{"title":"CAE for Injection Molding: What’s Next?","authors":"Kuo K. Wang","doi":"10.1115/imece2000-1244","DOIUrl":"https://doi.org/10.1115/imece2000-1244","url":null,"abstract":"\u0000 After a well-focused research effort over the past quarter of a century, CAE for injection molding has become a common engineering tool used widely in industrial practice. Today, part and mold designers readily make use of CAE software tools to make rational design decisions based on scientific principles rather than solely on prior experiences. While the common goal of the industry is to produce plastic parts anywhere in the world at the lowest cost, with the best quality and fastest speed to market, a missing link in an integrated production system seems to lie in the ability at the shop floor to control the molding process automatically and adaptively without compromising part quality. As the IT (Information Technologies) and Web-based engineering continue to strive, the injection molding industry would benefit immensely to achieve its goals. This paper discusses some issues on technical challenges and opportunities.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122144213","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}
M. Motuku, U. Vaidya, G. Janowski, G. Basappa, S. Jeelani
The influence of test conditions on the low velocity impact (LVI) response and damage evolution in neat resin plaques was investigated and documented. Specifically, the effect of impactor mass, velocity, and corresponding impact energy on the LVI response and damage evolution in unreinforced DERAKANE vinyl ester 411-350-resin system was studied. An instrumented drop weigh test machine was used to conduct the low velocity impact tests. The room temperature response of the material to impact loading and damage evolution was investigated using the impact load histories, impact plots and fractography analysis. This study is built upon previous work by the authors on LVI of neat resin systems, particularly those that have emerged as a new class of resins in liquid molding process. The study was motivated by the need for data and understanding of the failure characteristics of the individual constituents of a composite material such as in modeling of damage propagation and failure criteria analysis. For constant impact velocity, the time-to-maximum load (tm), total impact duration (tt), and the energy-to-maximum load to total energy absorbed (Em/Et) ratio increased, and energy absorbed after peak load (Ep) decreased with the mass of the impactor. For constant impactor mass, the time-to-maximum load and total impact duration decreased, the Em/Et ratio remained fairly the same, and energy absorbed after peak load increased with velocity; i.e., the impact velocity and mass had opposing effects on the time-to-maximum load, the total impact duration, Em/Et and energy absorbed after peak load. A single layer of plain-weave S2-glass fabric was incorporated in some of the unreinforced plaques in order to analyze the influence of reinforcement on the impact response and damage evolution. Insertion of a fabric layer aided in containment of the damage within the bounds of the specimen and to isolate the failure characteristics, which enabled further analysis of the impact response and damage evolution.
{"title":"Effect of Impact Velocity and Impactor Mass on the Low Velocity Impact Response of Liquid Molding Vinyl Ester-350 Resin and Fiber-Reinforced Plaques","authors":"M. Motuku, U. Vaidya, G. Janowski, G. Basappa, S. Jeelani","doi":"10.1115/imece2000-1229","DOIUrl":"https://doi.org/10.1115/imece2000-1229","url":null,"abstract":"\u0000 The influence of test conditions on the low velocity impact (LVI) response and damage evolution in neat resin plaques was investigated and documented. Specifically, the effect of impactor mass, velocity, and corresponding impact energy on the LVI response and damage evolution in unreinforced DERAKANE vinyl ester 411-350-resin system was studied. An instrumented drop weigh test machine was used to conduct the low velocity impact tests. The room temperature response of the material to impact loading and damage evolution was investigated using the impact load histories, impact plots and fractography analysis. This study is built upon previous work by the authors on LVI of neat resin systems, particularly those that have emerged as a new class of resins in liquid molding process. The study was motivated by the need for data and understanding of the failure characteristics of the individual constituents of a composite material such as in modeling of damage propagation and failure criteria analysis.\u0000 For constant impact velocity, the time-to-maximum load (tm), total impact duration (tt), and the energy-to-maximum load to total energy absorbed (Em/Et) ratio increased, and energy absorbed after peak load (Ep) decreased with the mass of the impactor. For constant impactor mass, the time-to-maximum load and total impact duration decreased, the Em/Et ratio remained fairly the same, and energy absorbed after peak load increased with velocity; i.e., the impact velocity and mass had opposing effects on the time-to-maximum load, the total impact duration, Em/Et and energy absorbed after peak load.\u0000 A single layer of plain-weave S2-glass fabric was incorporated in some of the unreinforced plaques in order to analyze the influence of reinforcement on the impact response and damage evolution. Insertion of a fabric layer aided in containment of the damage within the bounds of the specimen and to isolate the failure characteristics, which enabled further analysis of the impact response and damage evolution.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"133 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125552860","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}
In this work, we develop a numerical simulation method to optimize the injection molding process using the design sensitivity analysis (DSA). The optimization concerns the filling stage and focuses on the number and location of gates in a mold cavity as well as the injection pressure, considered as one of the key processing parameters, in order to minimize the fill time. Since the problem to be solved involves transient flow with free surfaces, the direct differentiation method is used to evaluate the sensitivities of the Hele-Shaw, filling fraction and the energy equations with respect to the design variables used in the analysis. The mesh domain parameterization is coped with using B-spline functions. Sensitivity equations are solved by means of finite element method. The proposed numerical approach is combined with the sequential linear and quadratic programming method of the DOT optimization tools to find the new design variables at each iteration. Starting with any initial gate locations and injection pressure profile, the method enables us to find the optimal gate locations together with the optimal injection pressure profile. Finally, numerical results involving complex mold geometries are presented and discussed to assess the validity and robustness of the proposed method.
{"title":"Design Sensitivity Analysis Applied to Injection Molding Process: Injection Pressure and Multi-Gate Location Optimization","authors":"K. Kabanemi, J. Hétu, A. Derdouri","doi":"10.1115/imece2000-1223","DOIUrl":"https://doi.org/10.1115/imece2000-1223","url":null,"abstract":"\u0000 In this work, we develop a numerical simulation method to optimize the injection molding process using the design sensitivity analysis (DSA). The optimization concerns the filling stage and focuses on the number and location of gates in a mold cavity as well as the injection pressure, considered as one of the key processing parameters, in order to minimize the fill time. Since the problem to be solved involves transient flow with free surfaces, the direct differentiation method is used to evaluate the sensitivities of the Hele-Shaw, filling fraction and the energy equations with respect to the design variables used in the analysis. The mesh domain parameterization is coped with using B-spline functions. Sensitivity equations are solved by means of finite element method. The proposed numerical approach is combined with the sequential linear and quadratic programming method of the DOT optimization tools to find the new design variables at each iteration. Starting with any initial gate locations and injection pressure profile, the method enables us to find the optimal gate locations together with the optimal injection pressure profile. Finally, numerical results involving complex mold geometries are presented and discussed to assess the validity and robustness of the proposed method.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134413381","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}
Runner system design for injection molds with multiple gates or multiple cavities often requires iterative analyses for optimized results, because the gate locations or cavity shapes may not be naturally balanced. In addition, in molds with symmetrical layouts, the required injection pressure may be unnecessarily high if the runners are poorly sized. In this paper, a scheme for quickly optimizing runner system design is presented. The objective of design optimization is to minimize the required injection pressure within the design space defined by a given total runner volume. Each runner segment can be given an upper limit and lower limit to define the range of runner cross sectional dimensional size. Application examples are included to demonstrate the effectiveness of the scheme.
{"title":"Runner System Design Optimization for Multigated and Multicavity Injection Molds","authors":"Xiaoshi Jin","doi":"10.1115/imece2000-1247","DOIUrl":"https://doi.org/10.1115/imece2000-1247","url":null,"abstract":"\u0000 Runner system design for injection molds with multiple gates or multiple cavities often requires iterative analyses for optimized results, because the gate locations or cavity shapes may not be naturally balanced. In addition, in molds with symmetrical layouts, the required injection pressure may be unnecessarily high if the runners are poorly sized. In this paper, a scheme for quickly optimizing runner system design is presented. The objective of design optimization is to minimize the required injection pressure within the design space defined by a given total runner volume. Each runner segment can be given an upper limit and lower limit to define the range of runner cross sectional dimensional size. Application examples are included to demonstrate the effectiveness of the scheme.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114582933","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}
Calendering of multi-layer sheets is an excellent process for production of sheets and films for thermoformable feedstocks. The quality of the sheet surface and throughput rate are strongly affected by thermal and adhesive properties of constituent materials and temperatures of individual layers and nip-rolls. We conducted a set of experiments that allows us to relate process conditions to sheet quality and develop mathematical functions for process optimization. In addition, we have developed a physics-based model to calculate transient thermal distribution in the sheet and adhesive strength between rolls and sheet surface. Model predictions of temperature are in good agreement with actual surface temperature measurement. The model can be used to relate quality characteristics to thermal gradients and adhesive strength and can become a useful tool for development the of optimum process envelope for highest throughput.
{"title":"Process Stability in Multilayer Sheet Extrusion","authors":"R. K. Upadhyay, G. Tryson","doi":"10.1115/imece2000-1242","DOIUrl":"https://doi.org/10.1115/imece2000-1242","url":null,"abstract":"\u0000 Calendering of multi-layer sheets is an excellent process for production of sheets and films for thermoformable feedstocks. The quality of the sheet surface and throughput rate are strongly affected by thermal and adhesive properties of constituent materials and temperatures of individual layers and nip-rolls. We conducted a set of experiments that allows us to relate process conditions to sheet quality and develop mathematical functions for process optimization. In addition, we have developed a physics-based model to calculate transient thermal distribution in the sheet and adhesive strength between rolls and sheet surface. Model predictions of temperature are in good agreement with actual surface temperature measurement. The model can be used to relate quality characteristics to thermal gradients and adhesive strength and can become a useful tool for development the of optimum process envelope for highest throughput.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123205847","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 process of reactive melt infiltration can be used to fabricate ceramics and ceramic matrix composites. This process involves a liquid metal being allowed to infiltrate a medium with which the liquid reacts to form a resultant ‘matrix’ along with the already present reinforcing fibers. The authors’ previous work on this area revealed that the transient porosity and permeability of a porous medium can be determined for certain geometries from the reaction kinetics and coupled heat and mass transfer problem occurring at the pore level. But the formulation at the macro level, which is essential to optimize the process, has been limited. Towards this end, this paper solves the macro reactive flow problem in a porous medium analytically as well as numerically. The focus of this article will be on the solutions for the advance (displacement) of the ‘infiltration front’ with progressive chemical reaction occurring between the medium and the infiltrant. A finite element formulation is used to solve the problem computationally; a level set formulation is used to track the infiltration front during the process. Excellent agreement is obtained between the analytical and computational solutions thereby validating the level set finite element formulations.
{"title":"Macro Modeling of Reactive Infiltration Using Level Set Finite Element Formulations","authors":"D. Balagangadhar, G. Rajesh","doi":"10.1115/imece2000-1239","DOIUrl":"https://doi.org/10.1115/imece2000-1239","url":null,"abstract":"\u0000 The process of reactive melt infiltration can be used to fabricate ceramics and ceramic matrix composites. This process involves a liquid metal being allowed to infiltrate a medium with which the liquid reacts to form a resultant ‘matrix’ along with the already present reinforcing fibers. The authors’ previous work on this area revealed that the transient porosity and permeability of a porous medium can be determined for certain geometries from the reaction kinetics and coupled heat and mass transfer problem occurring at the pore level. But the formulation at the macro level, which is essential to optimize the process, has been limited. Towards this end, this paper solves the macro reactive flow problem in a porous medium analytically as well as numerically. The focus of this article will be on the solutions for the advance (displacement) of the ‘infiltration front’ with progressive chemical reaction occurring between the medium and the infiltrant. A finite element formulation is used to solve the problem computationally; a level set formulation is used to track the infiltration front during the process. Excellent agreement is obtained between the analytical and computational solutions thereby validating the level set finite element formulations.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129967604","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}
A new model for strain-rate dependence of elongational viscosity of a polymer is introduced. The proposed model can capture the initial strain thickening, which is followed by a descent in elongational viscosity as the elongation rate is further increased. Effect of the four rheological parameters in the new model on a 4:1 entrance flow is analyzed. It is confirmed that the entrance pressure loss and recirculating vortices in an entrance flow grow significantly as the Trouton ratio is increased. The center-line velocity near the abrupt contraction in a 4:1 entrance flow is found to overshoot its value for a fully developed flow in the downstream channel, if the Trouton ratio has a local minima beyond the Newtonian limit of the polymer.
{"title":"An Investigation of the Effect of Elongational Viscosity on Entrance Flow","authors":"D. Sarkar, M. Gupta","doi":"10.1115/imece2000-1233","DOIUrl":"https://doi.org/10.1115/imece2000-1233","url":null,"abstract":"\u0000 A new model for strain-rate dependence of elongational viscosity of a polymer is introduced. The proposed model can capture the initial strain thickening, which is followed by a descent in elongational viscosity as the elongation rate is further increased. Effect of the four rheological parameters in the new model on a 4:1 entrance flow is analyzed. It is confirmed that the entrance pressure loss and recirculating vortices in an entrance flow grow significantly as the Trouton ratio is increased. The center-line velocity near the abrupt contraction in a 4:1 entrance flow is found to overshoot its value for a fully developed flow in the downstream channel, if the Trouton ratio has a local minima beyond the Newtonian limit of the polymer.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121054484","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}
Characterization of the transient rheological response of polymer melts is important for computerized modeling and optimization of the manufacturing processes involving fast polymer melt flow such as injection molding and extrusion. In this paper, a new cone-and-plate rheometer utilizing the Kolsky torsion bar technique is reported. This rheometer can be accelerated to an angular velocity of 1600 rad/s within 100 μs. It enables characterization of the transient response of polymer melts for shear rates up to 104 1/s, temperatures up to 300°C, pressures up to 10 MPa, and shear strains up to 1000%. Experimental data are presented for a low-density polyethylene melt at shear rates between 780 1/s and 6840 1/s. The results show that the shear stress in the material increases not only with the shear rate but also more significantly with the shear strain. The significance of this finding is also discussed.
{"title":"A New Technique for Characterizing the Transient Rheological Response of Polymer Melt at High Shear Rates","authors":"R. Feng, Y. Hu","doi":"10.1115/imece2000-1228","DOIUrl":"https://doi.org/10.1115/imece2000-1228","url":null,"abstract":"\u0000 Characterization of the transient rheological response of polymer melts is important for computerized modeling and optimization of the manufacturing processes involving fast polymer melt flow such as injection molding and extrusion. In this paper, a new cone-and-plate rheometer utilizing the Kolsky torsion bar technique is reported. This rheometer can be accelerated to an angular velocity of 1600 rad/s within 100 μs. It enables characterization of the transient response of polymer melts for shear rates up to 104 1/s, temperatures up to 300°C, pressures up to 10 MPa, and shear strains up to 1000%. Experimental data are presented for a low-density polyethylene melt at shear rates between 780 1/s and 6840 1/s. The results show that the shear stress in the material increases not only with the shear rate but also more significantly with the shear strain. The significance of this finding is also discussed.","PeriodicalId":198750,"journal":{"name":"CAE and Related Innovations for Polymer Processing","volume":"225 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115187985","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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