Adhesion tester, calibration

Figure 2. Calibration of Elcometer adhesion tester with Tnstron tester.

A different principle is used in ultrasonic resonance testing. Here, thickness vibrations are induced in the adherend/adhesive/adherend sandwich in which the two adherends eire considered to act as rigid masses while the adhesive is an almost massless spring. If the type and thickness of the metal sheets is constant, then the resonant frequency is a function of the thickness and bulk modulus of the adhesive. The well-known Fokker Bond Tester (Mark II) overcomes the difficulty of the many variables in the ultrasonic resonance test by coupling the joint to a system of well-defined resonance characteristics. Changes in the frequencies of the joint-transducer system are correlated with known defects and a calibration curve obtained. The calibration curves can then be used to establish acceptance limits which can be (and are extensively) used for quality control in production. 

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