Experimental analysis of the ratcheting behavior of linear flow split flanges of HC340LA

In this work the cyclic transient behavior of the steel alloy HC340LA was analyzed. Experimental tests have been carried out on specimens manufactured out of metal sheets (this material in considered in as-received state) and on specimens extracted from linear flow split flanges, which are manufactured by a process of severe plastic deformation. This process leads to a deep change in the microstructure. The results from specimens of material in as-received state and out of flanges have been compared. Besides studying the strain softening by means a series of uniaxial strain controlled tests with image, the research focuses on the ratcheting phenomenon. Ratcheting has been observed in uniaxial stress controlled tests at room temperature and a detailed description of this phenomenon has been provided with relation to the applied mean stress (also for compressive mean stress), stress amplitude and stress ratio. Ratcheting was observed also in loading conditions with zero mean stress and this behavior was discussed qualitatively. The analysis of the fracture surface of some of the tested specimens show that the fracture mechanisms for ratcheting failure differs from the conventional fatigue failures.