Contact interval, elastic

The contact method can be used to obtain the complete set of stiffness constants for samples with much smaller dimensions. In this method [3,5], a piezoelectric ceramic transducer, bonded to one surface of the sample, generated a beam of pulsed 10 MHz elastic waves that was subsequently received by another transducer bonded to the opposite surface. The wave velocity was calculated from the transit time of the ultrasonic pulse measured on a gated time interval counter. Longitudinal and transverse waves were generated using two different types of transducers. 

The point-by point analysis was used to gain the loading-point displacements, i.e. deflections of the notched beams, of the photographic plates of all load intervals of the specimens. The elastic deformations of the loading frame and the supports and the contact deformations between the specimens and supports were deducted from the total deformations measured by using the speckle photography and the point-by-point analysis. As the results, the load vs. loading-point displacement P-6 curves of all tested specimens were obtained. The P-5 curves were drawn in Fig.3. 

Durometer hardness testing determines the resistance of the sample to penetration by an indentor, which is a spring-loaded point initially protruding 1 mm from a flat surface. The profile of the indentor and the elastic constant of the spring to which it is attached define the type of durometer. In the case of polyethylene, durometer Type D is commonly used. When the flat surface is brought into firm contact with a block of polymer (minimum thickness 6.35 mm), the depth to which the indentor penetrates the specimen is inversely proportional to its hardness. After a fixed interval of time (commonly 10 secs), the hardness, in arbitrary units, is read directly from the scale. 

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