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Validating Process Simulation to Experimentation for Reinforced Sand Molds


Simulation results confirmed the locations of stress concentration and demonstrated accuracy with the actual temperature profiles and cracking


locations. YAN LU, HUIMIN WANG AND ALAN LUO, THE OHIO STATE UNIVERSITY (COLUMBUS, OHIO); KEITH RIPPLINGER, HONDA ENGINEERING NORTH AMERICA (ANNA, OHIO).


S


and casting is the most commonly used casting process. Components with


intricate cavities can be cast by insert- ing cores made of foundry sand. Of all the aggregates used to produce sand molds/cores, silica sand is the most popular in producing highly dimen- sionally accurate castings at a cost more favorable than other materials, such as zircon, chromite, and mullite ceramic. In molding operations, resin binders and hardeners are generally added into silica sand. Sand with these mixtures is called resin-bonded sand, and it typically consists of 93-99% silica and 1-3% binders. In the past few decades, simula-


tion technology has made remarkable progress in casting design and process optimization prior to actual manu- facturing, which reduces the time and cost of conventional trial-and-error methods. Although many experiments have been done to study sand molds/ cores (silica sand stiffness, sand cores expansion), simulation techniques for predicting and controlling sand molds/ cores casting process are still underde- veloped due to the complex mechani- cal behavior and failure mechanisms of sand materials. Tus, it is necessary to develop reliable and robust process


30 | MODERN CASTING July 2017


simulation models of sand molds/cores for more efficient manufacturing. In the present study, mechanical tests of resin-bonded silica sand with 98.7% silica and 1.3% phenolic resin binder were performed. Experimental data from mechanical tests, together with some key data from literature, were used to build a material model for sand molds/cores for casting process


Fig. 1 A schematic cross-section of intact sand cup mold is shown.


simulation. Ten, casting simulation for three different geometries of sand cups was performed, and correspond- ing experimental validation was carried out. Te goal was to establish sand material models and apply them to process simulation and experimental validation of sand casting. A commercial resin-bonded silica sand mixture (98.7% SiO2, 1.3% phenolic resin binder) was studied through both experiments and simula- tion. Mechanical tests, including three-point bending test and uniaxial tensile test, were employed to study the mechanical behaviors of the sand. A hardness test was done as a quan- titative measure to confirm a uniform curing condition. Experimental data from mechanical tests were further employed to calibrate the simulation database. Cylindrical sand cup molds were designed to be filled with an aluminum alloy. Te casting process was simulated using a finite element analysis (FEA) code. Laboratory grav- ity casting experiments were carried out to validate the simulation results. Both temperature profiles and failure positions presented good agreement between simulation and experiments. Te methods and results provide valuable information on sand proper-


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