The most convenient tool for measuring edge stress is automotive sunroofs is the EdgeMaster 2 real-time PSA (Photoelastic Stress Analysis) system with integrated edge guide. This easy to use hand-held system is specifically designed to slide along the edge of the windshield and reflect light off black frit to measure windshield edge stress. Measurements can be logged at key locations.
The GFP 1600 is the tool of choice for general area stress measurement, including area stress in automotive sunroofs. The system can be used with any c-mount lens, including zoom lenses, to conveniently image broad areas and/or close-up details. Combined with a flat-panel illuminator (GFP1600 FPI), full sunroof stress images can be acquired easily, in seconds. Although not as common in sunroofs, the GFP 1600 FPI is a powerful tool to document temper patterns. It measures the average stress through the glass and can show imbalance in the tempering, although it does not explicitly provide the surface stress or (skin stress). Examples can be found in sidelite/backlite applications.
Some assembly stress work can be accomplished by viewing the stress in the glass; however, often it’s important to know the stress changes on the outside surface. The GFP1600, combined with simple glue on sheet coatings and a camera jig, is an ideal tool for measuring assembly stress. Sheet coatings are easy to apply, and the glass stand accurately positions the system over the coating, without fuss.