Investigation of mechanical properties of Armco-iron during fatigue test

Abstract

In this paper the mechanical properties of armco-iron are studied experimentally. The ultrasonic testing machine USF-2000 was used to carry out fatigue tests involving 10⁶–10¹⁰ loading cycles. The frequency of loading is 19.5?±?0.5?kHz. Based on the experimental data, the W?hler curve was obtained.

For the analysis of physical condition, two new sensors were designed, one of which measured the electric resistance of the sample and the other measured the magnetic permeability. Second measuring method can be applied to ferromagnetic materials only, though it may be useful for studying the mechanical properties of metals in general.

It was shown that the significant changes in physical processes accompanying the evolution of structural defects in the material were observed in the final stages of the experiment.

The applied measurement techniques allowed us to exactly determine the time of fatigue crack initiation below the surface the material, which cannot be monitored by the standard optic methods.