Method and apparatus for thickness determination in multilayer a

Details Method and apparatus for thickness determination in multilayer a Method and apparatus for thickness determination in multilayer a

1997-09-15

1999-11-02

Brock, Michael

Measuring and testing

Vibration

By mechanical waves

73602, 73622, 73629, 73 182, G01N 2910

Patent

active

059748869

ABSTRACT:
An exemplary apparatus for determining the thicknesses of individual layers in a multilayer article comprises an ultrasonic transducer coupled to the multilayer article with a buffer rod of similar acoustic properties, a pulser-receiver-amplifier which generates ultrasonic waves to produce discernible, time resolved pulse echoes, a digitizing oscilloscope which may be used to view the received pulse echoes, and a computer for controlling data acquisition and analysis. The computer is programmed to execute the exemplary method, which comprises the steps of selecting a center frequency of a transducer such that respective pulse echoes produced at the interfaces between layers of the multilayer article each have a common distinguishing feature with a signal to noise ratio greater than or equal to a predetermined value, and the pulse echoes are resolved in time; determining a transit time correction factor for the layer of the multilayer article based on an actual transit time measured with the transducer adjacent to the layer and an apparent transit time measured with the transducer not adjacent to the layer; propagating a pulse through the multilayer article to produce pulse echoes at the interfaces between the layers of the multilayer article; determining a measured transit time of the pulse through the layer based on the pulse echoes at the interfaces of the layer; and calculating a thickness of the layer based on the measured transit time and the transit time correction factor.

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