An Experimental Study of Inhomogeneous Cyclic Plastic Deformation

Abstract

A localized inhomogeneous cyclic plastic deformation phenomenon was experimentally investigated in a mild steel. Small strain gages were utilized to characterize the local deformation within the gage section and the gross deformation was measured with an extensometer. Both fully reversed symmetrical loading and asymmetrical loading with a mean stress were used in the cyclic experiments. Plastic deformation was initiated in local areas of the specimen and it propagated into the whole gage section in the specimen with increasing cyclic loading. The local inhomogeneous cyclic deformation was dependent on the loading magnitude and evolved with continued cyclic loading.

Cyclic deformation and fatigue damage in single-crystal magnesium under fully reversed strain-controlled tension–compression in the [1 01¯0] direction

“…The second stress drop is followed by an immediate stress increment by 10 MPa and a subsequent plastic flow plateau (Δε 2 = 0.09%), which continues until reaching the tensile peak strain of 0.75%. The currently observed unstable plastic flow is similar to the inhomogeneous plastic deformation associated with Lüders band propagation in carbon steels [20,21] and the serration of the stress-strain curve (Portevin-Le Chatelier (PLC) effect) observed in aluminum alloys [22][23][24]. Unlike the highfrequent serration with small stress drop and increment (around 5 MPa in average) in the PLC effect, the magnitude of stress drop in the [10-10] Mg single crystals is rather random, varying from ~4 MPa to as high as ~30 MPa.…”

“…Moreover, both the stress increment and the plastic flow plateau can be followed after a stress drop. The underlying mechanisms of plastic instability might be related to dislocation-solute interaction (or dynamic solute aging) and dislocationdislocation interaction [20][21][22][23][24]. Without the presence of solutes in the pure Mg single crystals, the dislocation-solute interaction can be ruled out as a possible cause of the observed phenomenon and therefore, the dislocation-dislocation interaction can be a probable cause.…”

Benchmark experiments and characteristic cyclic plasticity deformation

“…Step 2 Δε/2=1.5% band during yielding (Jiang, 2001;Zhang and Jiang, 2004). The Lü ders band propagation typically occurs in carbon steels under cyclic loading, resulting in an overall cyclic softening.…”

Effect of cyclic stress reduction on high temperature creep characteristics of solid solution Al−2·9 wt-Mg alloy

“…With ever increasing pursuit of light weight and high performance structures in industry, there has been a corresponding rise of interest in maximising the use of material's potentials. 1,2 Attempts have been made to design a machine element beyond the traditional yield strength of the material. As a result, cyclic plastic deformation becomes a major concern.…”

“…(2) which is derived from equation(1). The dependence of b on the s cy and n values are respectively shown in Fig.5a…”