Technical Publications & Articles
A selection of published technical papers and articles
Converting Core Sand Binder Processes in the Virtual World,
Real Benefits in the Real World
A technical paper on using CFD to simulate a new process before changing the actual process.
Authors: Nigel P Yeomans, Jesus Benavente Jr.
Publication: AFS Transactions
Copyright: American Foundry Society
Abstract
For the past thirty years, many cores have undergone a conversion from the shell (Croning) production process to the phenolic urethane cold box process. It is widely accepted that the PUCB process is generally more productive than the heat cured shell process and the vast number of cores converted over the years is a testament to that. The remaining cores that are still produced using the shell process are sometimes difficult cores to produce, often have some unique property that lends itself to the shell process or have been a victim of under investment. This paper outlines the process undertaken by one foundry to optimize the process of converting a shell core to a cold box core using computational fluid dynamics software to design the new process. The motivation behind this approach was to optimize the new production method at the same time as minimizing process method changes and financial investment. This approach also builds confidence in the process before the investment is made and leads to the greatest probability of success.
Development of a Structurally Optimized Heavy
Duty Diesel Cylinder Head Design Capable of 250
Bar Peak Cylinder Pressure Operation
A technical paper on designing the structural architecture of a heavy-duty diesel cylinder head to achieve cylinder pressures of 250 bar without exotic casting alloys.
Authors: Marc Megal, Barry Westmoreland, Guy Jones, Ford Phillips, Doug Eberle, Mark Tussing
Nigel Yeomans
Publication: SAE International 2011-01-2232
Copyright: SAE International
Abstract
Historically, heavy-duty diesel (HDD) engine designs have evolved along the path of increased power output, improved fuel efficiency and reduced exhaust gas emissions, driven both by regulatory and market requirements. The various technologies employed to achieve this evolution have resulted in ever-increasing engine operating cylinder pressures, higher than for any other class of internal combustion engine. Traditional HDD engine design architecture limits peak cylinder pressure (PCP) to about 200
bar (2900 psi). HDD PCP had steadily increased from the early 1970’s until the mid 2000’s, at which point the structural limit was reached using traditional methods and materials. Specific power output reversed its historical trend and fell at this time as a result of technologies employed to satisfy new emissions
requirements, most recirculation (EGR). While future incremental improvements to specific power are predicted to occur through refinements in existing technology, a significant change in HDD structural architecture is required to allow higher PCP operation. Many proposed combustion, emissions reduction
and high efficiency technologies for the future are also pointing to the need for increased PCP. Once higher PCP operation can be achieved, HDD performance can return to its historical trends and enable much of the advanced diesel combustion research ongoing throughout the world today to become more commercially viable. The challenge is to determine what this structural architecture must be.
Using “Gate Extensions” to Produce Thin-Wall Castings
Authors: R.E. Showman, R.C. Aufderheide, N.P. Yeomans
Publication: AFS Transactions
Copyright: American Foundry Society
A technical paper on using insulating mold materials to control and extend the flow of metal.
Abstract
Thin-wall castings present special challenges both to prevent misruns, cold-shuts, and other related casting defects and to provide acceptable physical and metallurgical casting properties. Previous work has shown that low density alumina silicate ceramic (LDASC) and sand blends can be used to modify and control the thermal properties of the mold or core and produce thin-wall castings that were difficult or impossible with conventional materials. This provides the option of “engineering” the thermal properties of the mold and core components to match the local section thickness of the casting. Another design option has been developed for thin-wall (<3mm) castings. Tests were conducted with the LDASC material to produce “gate extensions” within conventional sand molds. These extensions provide a means of directing and controlling the flow of metal into very thin sections. Casting examples were produced and used to develop modeling parameters for the application of the technology to new casting designs.