An experimentally validated contour method/eigenstrains hybrid model to incorporate residual stresses in glass structural designs

Abstract

Contour method-based finite element models together with knowledge of the surface deformation resulted from the stress relaxation along a newly cut-plane were used to construct the residual stresses in commercially available float glass. The results show that the residual stress depth profile of float glass is parabolic. The constructed residual stress profiles, validated to some extent against results of scattered light polariscope experiments, were then used to establish the misfit strains (i.e. eigenstrains) existed in the original glass specimens. It is shown that despite the modelling uncertainty of the contour method and the limitations associated with the scattered light polariscope measurements, the eigenstrain depth profile in a given float glass specimen can be determined to an acceptable accuracy. The article shows that once the underlying eigenstrain distribution in a given thickness of glass has been determined, the complete residual stress distribution can simply be determined by incorporating the eigenstrain profile as a misfit strain in an appropriate finite element model. It is also shown that the hybrid contour method/eigenstrain model enables modelling the residual stress around stress concentration features such as holes and/or stress evolution during subsequent applied loadings, by simply using the knowledge of eigenstrains.

Mechanical prestressing of annealed glass beams using pretensioned GFRP: Characterisation and potentiality

“…A surface compressive prestress has potential to improve the apparent tensile strength of glass. As stated in Section 1, although commercially available thermally-toughened glass possess a compressive prestress in the surface regions, toughened glass is not desirable from structural safety point of view since tempered glass fractures into small pieces [10][11].…”

“…A scattered light polariscope, SCALP-05 [10,30], was used to measure the prestress introduced into the glass beams. SCALP-05 uses glass birefringence that changes the polarisation of an input laser beam and the consequent variation in the optical retardation of the scattered light to determine the stress at a given location of glass.…”

“…SCALP-05 uses glass birefringence that changes the polarisation of an input laser beam and the consequent variation in the optical retardation of the scattered light to determine the stress at a given location of glass. Details of the use of SCALP-05 to measure stresses in glass can be found in elsewhere [10,30].…”

“…Polaricopes usually accurately measure the stresses within the surface regions of glass, but the measurement of stress data at mid-thickness regions of thick glass are less reliable [10]. The polariscope used in the present study (SCALP-05) [30] usually provide accurate stress measurements in glass up to ~3 mm from the surface [10]. Therefore, in the present study, stresses were measured up to ~3 mm deep from both top and bottom sides of the two-layer glass beams.…”

“…However, since glass has some initial prestress (i.e. residual stress) owing to its manufacturing process [10,11], these measured stresses may not be the actual prestress caused by the pretensioned GFRP strip.…”