ASTM C623 Test for Elastic Properties of Glass and Glass-Ceramic by Resonance

Scope:

All glass and glass-ceramic materials that are elastic, isotropic, and homogeneous can be tested in ASTM C623. Cracks or voids represent inhomogeneities in the material, therefore such materials cannot be tested with this method. Materials that cannot be prepared in a suitable geometry can not be tested as well.

Glass and glass-ceramic materials possess specific natural resonance frequencies. Resonance frequency depends upon the density, elastic moduli, and geometry of the test specimen. The knowledge about these parameters helps to calculate resonance frequency of a material. Resonance frequency value can be used to calculate elastic properties of Glass and Glass-Ceramic in ASTM C623 testing. 

Young’s modulus is determined using the resonance frequency in the flexural mode of vibration. The shear modulus, or modulus of rigidity, is determined using torsional resonance vibrations. Young’s modulus and shear modulus are used to compute Poisson’s ratio.

Test Procedure:

In ASTM C623, elastic properties are determined by calculating resonance frequencies. Resonance frequencies of test specimens are determined by exciting the specimens at different frequencies to find a particular frequency that matches the specimen’s natural resonance frequency t. It is a hit and trial method. 

To determine the resonance frequency in ASTM C623 testing, the specimens are excited by a transducer, (a transducer transforms a set electric signal into a mechanical vibration) which causes a vibration in the specimen. Another transducer converts the vibration in the specimen into an electric signal that is displayed on the screen of an oscilloscope to measure resonance. The dimensions of the specimen, its resonance frequency, and its mass is used to calculate Young’s modulus and Shear modulus. 

Data:

1. Method to calculate Young modulus for ASTM C623 testing: 

Y = (38.3 × f² × ρ × ℓ⁴)/d²

where:

Y = Young’s Modulus

f = resonance frequency of oscillations.

ρ = density

ℓ = length

d = width

2. Method to calculate Shear modulus: 

E = 2G(1 + ν)

Where:

E =  Young’s modulus, 

G =  shear modulus 

ν =  Poisson’s ratio

Conclusion:

ASTM C623 is used to determine elastic properties (Young’s Modulus, Shear Modulus, and Poisson’s Ratio) for Glass and Glass-Ceramics by Resonance.