ASTM C674 Determining Flexural Properties of Ceramic Whiteware

Scope:

ASTM C674 determines two things: the modulus of rupture and the modulus of elasticity. These two parameters are used by materials engineers to describe how material gets deformed. Both are written in the product’s specification.

The main difference between modulus of elasticity and modulus of rigidity is that the modulus of elasticity describes how material gets deformed when a force is applied at right angles to a surface of an object, causing the material to elongate or shorten while the modulus of rigidity describes how material gets deformed when a force is applied parallel to a surface of an object, causing one of the surfaces to shift relative to another surface of the same object. Both of these are crucial in ASTM C674.

Test Procedure:

In ASTM C674, the ceramic sample is placed on two ridges and a direct load is applied at the midpoint of the sample until the sample breaks. The modulus of elasticity is determined by halting the applied load at definite intervals and measuring the deflection of the specimen at the midpoint to the nearest 0.001 inches.

 Specimen size:

For ASTM C674, at least 10 samples are needed. The sample needs to be approximately 1.125 inch, 0.750 inch, 0.500 inch, or 0.250 inch in diameter, whichever diameter is most comparable to that of the finished product. The length needs to be approximately 0.50 inches to permit an overhang of at least 0.25 inches at each end when mounted on the supports. 

The dry-pressed specimens need to be rectangular bars approximately 1 inch by 0.50 inch in cross-section and at least 4.50 inches in length to permit an overhang of at least 0.25 inches at each end when mounted on the supports.

Data:

To calculate the Modulus of rupture for ASTM C674

1. For circular specimen: 

  M = 8PL/πd³

2. For rectangular specimen: 

M = 3 PL/2bd²

where: 

M = modulus of rupture

P = load at rupture

L = distance between supports

d = diameter of specimen

To calculate the Modulus of elasticity

1. For circular specimen

    E = 4WL³/3π∆d⁴

2. For rectangular specimen

E = WL³/4∆bd³

Where:

W = load coordinate of the selected point. 

D = deformation coordinate of the selected point. 

b = width of specimen at the center

Conclusion:

ASTM C674 determines flexural properties of Ceramic Whiteware by calculating the modulus of rupture and modulus of elasticity.