Fig. 4. Shown is the small, portable aeration sand fi lling system used in the study.
system is compactability, which is a measure of sand temper inversely related to bulk density. It is a physi- cal property related to the percentage decrease in a sample’s height when the sand is compacted at the mold- ing machine. In automated molding systems, compactability must be held constant. Moisture and compactabil- ity are key tests for controlling water additions. T e higher the com- pactability is, the wetter the sand. Moisture is adjusted to control com- pactability. T e cone jolt test directly relates to compactability and mea- sures the green sand system’s ability to absorb energy. T e modifi ed cone jolt test uses the same basic testing approach as the conventional test, but the mass of the cone can be adjusted to represent a specifi ed force on the sand. T e drop height of the cone, as well as the frequency of drops, also can be varied. In the modified cone jolt test,
a computer and data acquisition system controls, monitors and plots graphs of jolts vs. displacement of a specimen (Fig. 2). A standard AFS cone jolt specimen is placed between the base and the cone. When the test is initiated, a solenoid is cycled to pick up and drop the specimen automatically, while a linear voltage displacement transducer simultane- ously engages and measures longitu- dinal displacement of the specimen. The data acquisition system auto- matically logs and plots the jolts vs. displacement curves. The test stops automatically when the specimen splits or displaces 0.05 in. (1.27 mm) vertically. From the slope of the jolts vs.
displacement curve, specimen stiff ness (jolt/in.) is identifi ed. T e distance a curve travels to the right indicates the degree of plastic deformation induced by the cone on the sand system. T e area under the curve indicates the toughness (jolt x in.) of the sand sys- tem. Ultimate sand strength is reported as the number of jolts sustained.
32 | MODERN CASTING September 2013
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