Automated Measurement of Edge Stress in Automotive Glass

Alex S. Redner

Automotive glass is subjected to a complex set of stresses resulting from bending, heating and laminating processes. Tensile stresses develop near glass edges. If not controlled, these tensile stresses can result in delayed fracture and service failures. Windshields are also known to fail as a result of insufficient edge compression.

To assure quality and avoid service failures, thorough Quality Control procedures are implemented in producing automotive glass. Automotive glass manufacturers measure compressive and tensile stresses at numerous points around the periphery using manual Edge Stress meters. Visual readout however is time consuming and requires operators. Since the measured retardation in laminated windshields is low, repeatability of visual inspection is not satisfactory.

A new system was developed which automatically measures edge stress using a lightweight, portable, PC-based probe. This new system eliminates operator error and features data storage for review and documentation.

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