Study on Low Cycle Fatigue Failure Mechanism of Steel Material by Acoustic Emission

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In order to investigate the failure mechanism of steel material, the properties of acoustic emissions from the material were measured and analysed.Particularly, low cycle fatigue failure was mainly investigated. Low cycle fatigue tests were carried out on a specimen modeling pressed welded joint of steel reinforing bars, and a specimen with hour-glass shape made from mild steel. In some specimens, mechanical flaws were incuded on purpose in order to investigate the relationship between failure mechanism and the properties of acoustic emission. In addition, strain levels were varied in order to change the low cycle failure modes of specimens.Waveforms of aoustic emission were recorded by digital oscilloscope. Measured waveform was analysed from the viewpoints of frequency, occurrence time, etc. The relationship between these AE properties and failure mode depending on strain level and existance of mechanical flaws were investigated in detai.