Evolution of Some Structural Fine Parameter in the Superficial Layer during Low Cycle Fatigue Process

Abstract

Using laminate samples, investigations have been realized at variable solicitation of pure bending on a patented machine. The machine has two working places and it can be adjusted for different deformations, frequencies and number of cycles. The tests have developed in a symmetrical alternative regime at two frequencies. In this paper some results concerning the evolution of the crystalline lattice parameter, level of the texture were realized in steps of each two thousand cycles until a limit of 104 cycles. The X-ray diffraction method was used and information on the ferrite phase was obtained. The crystalline lattice parameter presents a decreasing tendency when the number of the fatigue cycles increase. This decreasing in jumps occurs. During fatigue tests at high testing frequencies, an increasing texture process is displayed, but at small fatigue testing frequencies, increasing and decreasing texture processes occur. Experimental data allows to estimate the history of the sample and its behavior in fatigue process.

Keywords

• steel
• fatigue
• low frequency
• lattice parameter
• texture
• X-ray diffraction