Abstract

Technical ceramics are an important part of the various construction materials in modern machine engineering. It would be advantagous to detect defects or inhomogeniousities in the early process of production to reduce the production costs. The non-destructive characterisation methods, especially the ultrasonic testing, to measure fast and with low costs thee inhomogeniousities and different material properties, are very interesting.

The main point of this work is the optimisation of different ultrasonic testing methods for the testing of green ceramic bodies. The problem is to couple the ultrasonic impulse into the testing material. Because of the destruction of the green ceramic the conventional coupling possibilities with water or other liquids are not applicable. An alternative way is presented only by the dry coupling method. In this work, different kinds of ultrasonic dry coupling will be tested for their sensitivity and lateral resolution to detect material mismatches. With dry coupling methods it is very difficult to analyse the lateral resolution of a real defect in green ceramic bodies. Appropriate devices that allow an water immersion technique for the green ceramic testing will be demonstrated. Another possibility of ultrasonic dry coupling with air-coupled ultrasonic transducers will be supposed.
The aim of this research is an ultrasonic areascan of green ceramic bodies. First results of combinations of different coupling techniques will be discussed.

Table of contents Full Text

1. Ultrasonic contact coupling
2. Ultrasonic coupling in immersion technique
3. Air coupled ultrasonic testing
4. References