Scale-free features of temporal localization of deformation in late stages of creep failure

Abstract

The last stage of material failure often shows a regime with power-law acceleration as the material lifetime is approached. We study this experimentally in tensile creep with paper samples using digital image correlation. The last, tertiary creep stage exhibits scale-free features in the sample response (strain rate) and its fluctuations. It is accompanied by an increasing localization of strain at the location of final failure. The main features are reproduced by a material model built on a viscoelastic fiber bundle model.

Detection of the onset of yielding and creep failure from digital image correlation

“…The experimental details of the paper creep experiments are described in Ref. [16]. The data used here include the global strain rate ˙ measured by the tensile testing machine and the local strains in the loading direction yy measured at different points in time.…”

“…Moreover, in creep defining the onset of failure is even more difficult, and the creep characteristics of different materials can vary. The common thing is that creep failure is preceded by an acceleration of strain accumulation (tertiary creep) [13][14][15][16], so a natural definition for the onset of creep failure is the point of minimum strain rate. This can also be thought of as a transition from one state to another-from a decelerating strain evolution to an accelerating one.…”

“…As a test material for creep, we have used a quasibrittle disordered material-paper. The creep behavior of paper is fairly well known [15][16][17] and can be collapsed to a single master curve. The behavior divides into three phases: primary, logarithmic, and tertiary creep.…”

“…The size of the resulting strain fields is 100 pixels × 800 pixels. An image of the sample and the strain field obtained by DIC can be seen in Fig.1(a).The experimental details of the paper creep experiments are described in Ref [16]…”

Detection of the onset of yielding and creep failure from digital image correlation

“…The experimental details of the paper creep experiments are described in Ref. [16]. The data used here includes the global strain rate ˙ measured by the tensile testing machine and the local strains in the loading direction yy measured at different points in time.…”