Ceramics

Verification of the Presence of Internal Stresses in a Lot of Glass Pieces

Customer: Experts-Conseils CEP

Mandate submitted to CIR Laboratory:

Verify whether the presence of internal stresses could be the cause of the failure of a lot of glass pieces observed in service.

Work conducted by CIR Laboratory:

1) Original resonance frequency measurement

A sample of the produced lot of pieces was first submitted to acoustic resonance measurements by means of the SonicByteTM apparatus. Following a modeling of the sample using the finite elements method, two natural modes of vibration have been selected, the flexion and the torsion modes. The optimal positions of impact and listening of the generated acoustic signals were also determined during this mathematical modeling for each of these modes.

2) Heat treatment

The glass sample was then subjected to heat treatment to eliminate any possible presence of internal stresses.

3) Residual resonance frequency measurement

After heat treatment, the resonance frequencies of the sample were measured in the same two modes of vibration considered.

4) Calculation of the elastic modulus variation

From the values of resonance frequency obtained, the variation of the sample's modulus of elasticity during the heat treatment was calculated for both modes of vibration considered.

5) Results analysis

The significant decreases observed in the elastic modulus of the sample after heat treatment (in the two vibration modes considered) allowed to conclude that internal stresses were indeed present in the original sample.

Deliverables:

A full report presenting: (1) - the objectives and scope of the work performed, (2) - the overall experimental procedures adopted, (3) - the detailed description of the results analysis conducted and  (4) - a conclusion confirming the presence of internal stresses in the analyzed sample was delivered to the customer on time.