Ultrasonic Fatigue Analysis on Steel Specimen with Temperature Control: Evaluation of Variable Temperature Effect
Authors: Lage, Y., Freitas, M., Montalvao, D., Ribeiro, A.M.R. and Reis, L.
Conference: XIII Portuguese Conference on Fracture
Dates: 2-3 February 2012Abstract:
Ultrasonic fatigue testing machine are being used to perform materials testing in the range of 10E9 to 10E10 fatigue cycles. The so-called very high cycle fatigue regime is now under intense studies in which concerns the lay-out of ultrasonic fatigue testing machines. Nevertheless, the accurate measurement of the parameters that influence fatigue life (stress, strain, displacement …) at ultrasonic frequencies still is a matter of concern and continuous development. The objective of this paper is to describe the design and construction of an ultrasonic fatigue testing machine at 20 kHz working frequency. In order to achieve fully automated tests, a closed loop control system was developed to use monitored temperature and displacement to set the power and the cooling periods of the machine. The monitoring of the displacement, considered here in the bottom face of the specimen, is carried out using a high resolution laser. The specimen´s temperature is monitored online through a pyrometer. To manage and process, a data acquisition device working at 400 kHz from National Instruments is used. The software was developed in house using the LabView package. The present paper describes the advantages and drawbacks of metal fatigue testing at very high frequencies.