K. Andreev1, N. Shetty2, E. Verstrynge2
1)  Ceramics Research Centre, Tata Steel, Velsen Noord, The Netherlands
e-mail: Kirill.Andreev@tatasteel.com
2)   Department of Civil Engineering, KU Leuven, Belgium
e-mail: Naveen.Shetty@kuleuven.be Els.Verstrynge@kuleuven.be

Keywords: Refractory masonry, Silica refractories, Strain controlled fatigue, Acoustic emission, Kaiser and Felicity effects, LOAD ratio, CALM ratio.

Abstract. Refractory masonry serves in industrial furnaces where it is exposed to repetitive thermal loads. Material fatigue is a frequent cause of structural failure. In this study, cyclic fatigue resistance of two silica-based products was analysed. The aim was to clarify the selection criteria for alternative lining materials. Displacement-controlled monotonic and cyclic bending tests were performed. The failure process was monitored during testing with the acoustic emission technique. Due to different micro-mechanical behaviour, the materials demonstrated different brittleness at failure. It was established that a reduced fatigue resistance can be expected at loading amplitudes above 60-70% of the critical strain. In this range, the material of lower strength and brittleness demonstrates lower fatigue resistance. However, the less brittle material also shows higher strains to failure and can therefore be a better option for specific applications. It was concluded that in the selection process, one should examine the fatigue resistance both in the absolute and normalised forms related to the loads typical for the given application. Acoustic emission parameters used in the investigation, such as CALM and LOAD ratios, proved to be a very efficient approach to monitor and predict the fatigue degradation of masonry materials.