Abstract
The objective of this paper is to describe the instrumentation of a new developed ultrasonic
fatigue testing machine at 20 kHz working frequency and compare the possible solutions to
estimate the stress applied in the middle section of the specimen. Stress is estimated by
measuring the displacement on bottom of the specimen and their strain on middle section.
The monitoring of the displacement, considered here in the bottom face of the specimen, is
carried out using a high resolution laser, the strain using a strain gauge in middle of specimen
and field temperature using a pyrometer and thermographic camera.
A LabVIEW routine is used to control the initial parameters of the transducer, such as the
frequency reset, the frequency seek, the load amplitude and to record data of all sensors. To
manage and process the data, a data acquisition device working at 400 kHz from National
Instruments is used.