電磁超音波共鳴法による鋼材疲労評価の研究

概要

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Recently, an EMAR(electro-magnetic acoustical resonance) measuring system has come to be in use for precision ultrasonic velocity measurement, which enables stress evaluation of a metallic material based on an acousto-elastic effect. It also serves as an ultrasonic attenuation measuring system with high accuracy owing to the couplantless nature of the EMAR system. In order to collect fundamental technical data for development of a fatigue damage evaluation technique before crack initiation, we carried out ultrasonic measurements with the EMAR system on SM400B and S35C steel specimens, that were fatigued under stress ratio R=-1. SM400B specimens were used for velocity and attenuation measurement, and S35C specimens were for acoustical anistoropy measurement. We examined the ultrasonic characteristics value changes during fatigue test in relation with fatigue deterioration index such as fatigue cycle number and plastic strain width of stress-strain curves. The results are as follows : (1)sound velocity decreases as fatigue proceeds, (2)attenuation fluctuates for high stress fatigued specimens, because EMAR signal reduced its amplitude and attenuation measurement becomes tough work, (3)acoustical anisotropy shows similar behavior as plastic strain width. We conducted additional experiments concerning peculiar properties of the EMAR system such as stress effect, specimen size effect, etc.
独立行政法人海上技術安全研究所の論文
2004-10-29