62 research outputs found
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Heat transfer at the mold-metal interface in permanent mold casting of aluminum alloys project. Annual project status report for the period October 1, 1997 to September 30, 1998
In the first year of this three-year project, substantial progress has been achieved. This project on heat transfer coefficients in metal permanent mold casting is being conducted in three areas. They are the theoretical study at the University of Michigan, the experimental investigations of squeeze casting and semi-solid casting at CMI-Tech Center, and the experimental investigation of low pressure permanent mold casting at Amcast Automotive. U-M did an initial geometry which was defined for ProCAST to solve, and then a geometry half the size was defined and solved using the same boundary conditions. A conceptual mold geometry was examined and is represented as an axisymmetric element.Furthermore, the influences of the localized heat transfer coefficients on the casting process were carefully studied. The HTC Evaluator has been proposed and initially developed by the U-M team. The Reference and the Database Modules of the HTC Evaluator have been developed, and extensively tested. A series of technical barriers have been cited and potential solutions have been surveyed. At the CMI-Tech Center, the Kistler direct cavity pressure measurement system has been purchased and tested. The calibrations has been evaluated. The probe is capable of sensing a light finger pressure. The experimental mold has been designed and modified. The experimental mold has been designed and modified. The first experiment is scheduled for October 14, 1998. The geometry of the experimental hockey-puck casting has been given to the U-M team for numerical analysis
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Heat transfer at the mold-metal interface in permanent mold casting of aluminum alloys project. Quarterly project status report, October 1--December 31, 1998
The first series of experiments at the CMI-Tech Center was successfully conducted on October 14 and 15 with the participation of the University of Michigan team. The preliminary experimental results indicate that the die surface temperatures (or near the surface) have a close correlation with the metal pressure profiles. Considering the difference in timing of the peak die temperatures, the high melt temperature and hotter die temperature for Inter 54 might cause a longer solidification time, and the pressure would decrease more slowly than for Inter 12. The slopes of the metal pressure profiles at the low pressure setting are almost linear. This may mean that the low metal pressure couldn`t effectively keep a pressure channel opened. In other words, as temperature decreased, the solid fraction increased and the solidified shell strengthened, and the pressure, which couldn`t overcome the resistance, would drop linearly. However, at the high pressure, there are inflection points in the pressure profiles. The inflection points are at about 8,500 psi for both the low and the high melt temperature settings. This suggests that the metal pressure was sufficient enough to overcome the resistance of the solidified shell before the inflection point was reached. A preliminary microstructure analysis shows that the dendrite arms at the location near the gate are much coarser than that at the top of the casting. The influence of intensification pressure on microstructure needs further verification and study
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Heat transfer at the mold-metal interface in permanent mold casting of aluminum alloys project. Quarterly project status report, April 1--June 30, 1998
Extensive progress in development of an HTC (heat transfer coefficient) Evaluator and in the preparation of the experiments at CMI and Amcast have been achieved in the last three months. The interface of the HTC Evaluator has been developed in Visual C++ for the PC platform. It provides a tool to collect and store the published data on heat transfer coefficients in a database for further analysis. It also supports the mathematical model for evaluation of heat transfer coefficients. More than 100 papers related to this project have been cited and most of them have been collected. The preparation of the experiments at CMI is almost completed. A hockey-puck mold has been selected for the experiments for squeeze casting and semi-solid casting. A direct cavity pressure measurement system was purchased from Kistler. The pressure probes and data acquisition software as well as the necessary accessories have been delivered. The instrumented mold modification has been designed and the modifications completed. At Amcast Automotive, a new wheel-like mold for low-pressure permanent mold casting was designed. The CAD file for mold fabrication has been generated. The modeling of the casting has been done. An extensive survey on the ultrasonic gap formation measurement was fulfilled. It is concluded that the ultrasonic probe is capable of measuring a gap under the authors` casting conditions. In the last three months, four project meetings has been organized and held with the industrial partners
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Heat transfer at the mold-metal interface in permanent mold casting of aluminum alloys project. Quarterly project status report, January 1, 1998--March 31, 1998
There have been numerous developments in the current project over the last three months. The most appropriate geometries for performing the interfacial heat transfer studies have been discussed with both of our Industrial Partners. Both companies have molds which may be available for adaptation to record the thermal history during casting required for determining interfacial heat transfer coefficients. The details of what instrumentation would be the most appropriate remain to be worked out, but the instrumentation would likely include thermocoupling in the mold cavity as well as in the mold wall, as well as pressure sensors in the squeeze casting geometry molds and ultrasonic gap monitoring in the low pressure and gravity fed permanent mold geometry molds. The first advisory committee meeting was held on February 6th, and the steering committee was apprised of the objectives of the program. The capabilities of the Industrial Partners were reviewed, as well as the need for the project to make use of resources from other CMC projects. The second full Advisory Committee Meeting will be held in early May
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