Sand testing of sand casting (3)

5) Strength test:

This is tempered sand strength expressed by its ability to hold model in shape. Sand molds are subject to compressive, tensile, shearing and transverse stress. The compressive strength test green and dry compressive strength of the test most commonly used in the foundry.

- Compression Tests A specimen of sand rammed produced Tempered shape is 2 inches in diameter and 2 inches tall. The sample is then rammed subject to load increase gradually until the sample breaks. The point where the sample taken breaks the compression strength.

- Shear Tests compressive loading system is modified to offset the specimen load to provide. Under most conditions the shear test results shown to be closely associated with the compression tests, although the latter property increases proportionately more high density ramming.

- The tensile test specimen is loaded in tension special waisted by a pair of grips. The test sample is rectangular plain transverse support by the end of knife edges and centrally loaded broken. And transverse tensile tests commonly applied to sand high strength, the conditions to be particularly associated with the stress incurred during handling cores and solutions.

6) Permeability Test:

Permeability is determined by measuring the air flow rate through compacted specimens under standard conditions. Roller sand sample is prepared using rammer and death. This sample (typically 2 inch dia and 2 inches tall) used for testing the permeability or porosity of the sand molding and core. The test is performed in permeability meters flat consists of a tank, water tank, nozzle, lever, adjusting the nose piece for fixing sand specimens and a manometer. The permeability is measured directly. Permeability number P is air volume (in cm 3) passing through sand specimen of 1 cm2 area and 1 cm cross-sectional height, a pressure difference of 1 gm / cm2 in one minute.

P = VH / ATP

Where,
P = permeability
v = volume of air passing through the specimen in c.c.
h = height of specimen in cm
p = pressure of air in gm/cm2
a = cross-sectional area of the specimen in cm2
t = time in minutes.

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