Determination of tensile membrane stress and compressive layer thickness in tempered glass using a CO.sub.2 laser beam
AssigneeFord Motor Company
InventorsAmin H. Hashemi, David N. Heilman
Life of this patent
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Abstract
A determination of the temper quality of a tempered glass sheet is made which includes determining the percentages of the thickness of a tempered glass sheet which are in compression as well as the sheet's tensile membrane stress. The process uses a CO.sub.2 laser beam, either on a painted or unpainted glass sheet, to shatter the glass sheet and then comparing the number of pulses required for the glass sheet to shatter to a correspondence, e.g., a graph, of tensile membrane stress v. compression layer thickness as a % of the total thickness of the glass sheet.
Claims10
A process for determining the percentage of the total thickness of a tempered glass sheet in compressive stress and the tensile stress of the tempered glass sheet, comprising the steps of:
- A) penetrating a major surface of the tempered glass sheet with a number of pulses of a laser beam generated by a circular CO.sub.2 laser having (a) a power between 5.0 and 200 watts, (b) a pulse length between about 0.1 and 1.0 msec, and (c) pulse interval between about 1 and 10 seconds until said glass sheet shatters;
- and
- B) comparing said number of pulses required for said tempered glass sheet to shatter to data which comprises said number of pulses as well as a correspondence of tensile membrane stress v. compression layer thickness as a % of the total thickness of samples of tempered glass having the same thickness and composition as said tempered glass sheet.
A process for determining the percentage of the total thickness of a tempered glass sheet in compressive stress and the tensile stress of the tempered glass sheet, comprising the steps of:
- A) penetrating a major surface of the tempered glass sheet of a thickness of about 3.8 mm with a number of pulses of a laser beam generated by a circular CO.sub.2 laser having (a) a power of 105 watts, (b) a pulse length of 0.5 msec, and (c) pulse interval of about 4 seconds until said tempered glass sheet shatters;
- and
- B) comparing said number of pulses required for said tempered glass sheet to shatter to data which comprises said numbers of pluses as well as a correspondence of tensile membrane stress v. compression layer thickness as a % of the total thickness of samples of tempered glass of the same thickness and composition as said tempered glass sheet.
Dependencies are inferred from the claim text.