Theory:

ASTM A84 specifies a tensile test for gray iron. Gray iron has a high percentage of graphite or carbon, which gives it a gray look and a graphitic  or crystalline structure. This type of iron is relatively low cost and easy to machine. Gray Iron also has a high damping capacity which means it does not transmit vibration as easily as metals like brass with low damping capacity. Along with damping capacity, gray iron also has a high specific heat index. Both of these qualities allow it to be a great material for automotive break pads and machine tool couplings and metal to metal interfaces. 

Gray iron does have several drawbacks including low tensile strength and the inability for it to be worked. The class rating for this metal are based on the tensile strength. Class No. 20 is 20+ ksi, class 25 is 25, class 300 is 300ksi, etc. 

Geometry:

There are three sizes of cast metal tensile bars for this test. The main difference between sample types is the diameter which is either at .5",  .75", or 1.25". The radius of the fillet is different for the largest sample. The specimens are button head type and the test bars are cast separately. 

Solution:

Universal Grip offers a Shoulder Grip with easily interchangeable inserts to account for different sized samples. The grips are the ideal solution for rapid testing of button head style specimens. Both the diameter of the test specimen and the radius of the fillet are customer specified and quickly machined to order. 

Universal Grip also offers Galdabini tensile testing machines to perform ASTM A48. The system can be pre-programmed and configured to run various ASTM tests as well as perform advanced data calculations. The Galdabini machines are flexible and very easy to learn. More information on Galdabini universal testing machines

Analysis:

ASTM A84 provides a simple measure of ultimate tensile strength. The tensile strength is calculated by taking the peak load and dividing it by the square area of the sample. For .5" diameter samples, the square area is .25. 

Similar Specifications:
ASTM E8 - Metal Tensile Testing
ASTM A370 - Steel Tensile Testing

 

 

ASTM A48

Tensile Testing Gray Iron Castings

ASTM A48 Tensile Fixture.jpg