Dislocation transport and intermittency in the plasticity of crystalline solids

Abstract

When envisioned at the relevant length scale, plasticity of crystalline solids consists in the transport of dislocations through the lattice. In this paper, transport of dislocations is evidenced by experimental data gathered from high-resolution extensometry carried out on copper single crystals in tension. Spatiotemporal kinematic fields display spatial correlation through characteristic lines intermittently covered by plastic activity. Intermittency shows temporal correlation and power-law distribution of avalanche size. Interpretation of this phenomenon is proposed within the framework of a field dislocation theory attacking the combined problem of dislocation transport and long-range internal stress field development. Intermittency and transport properties show remarkable independence from sample size, aspect ratio, loading rate, and strain-rate sensitivity of the flow stress.

Universal fluctuations and extreme statistics of avalanches near the depinning transition

“…In fact the variability in the acoustic emission experiments [7,[14][15][16][17][18] on the value of µ might be related to the fact that the experiments are performed at nonzero driving rate. If that is the case, we find that the deviation from the adiabatic driving rate enters in the mean field exponents as µ = 2−c, in a way similar to that for the driving-rate dependent scaling exponents α and τ in the power-law distributions of avalanche durations and sizes.…”

“…ice, Cd, Zn, and Cu, report robust power law scaling in the statistics of the maximum amplitude A m of acoustic waves emitted during plastic slip avalanches. The probability distribution density of the maximum AE amplitude follows a power-law tail P (A m ) ∼ A −µ m , with an exponent µ ≈ 2 [7,[14][15][16][17][18]. Since many slip avalanches are required to obtain good statistics for P (A m ), the deviations in the values of µ could depend on the experimental resolution.…”

“…Since many slip avalanches are required to obtain good statistics for P (A m ), the deviations in the values of µ could depend on the experimental resolution. Nevertheless, the exponent is remarkably robust to variations such as loading mode, type of crystal, temperature, forest hardening effect, or plastic anisotropy [16][17][18]. Under certain conditions, it is argued that the maximum amplitude A m is a measure of the area swept by the fastmoving dislocations [14,15].…”

Significant correlation between macroscopic and microscopic parameters for the description of localized plastic flow auto-waves in deforming alloys

“…In particular, the experimental studies of plastic flow in metals and alloys [1][2][3][4][5] have unambiguously demonstrated its tendency towards localization behavior from yield point to failure. Typical localization patterns observed by mechanical testing using a technique of double-exposure speckle-photography [6] are shown in Fig.…”

“…However, speculation continues concerning elastic waves, which occur in an elastically deforming solid and plastic waves, which are distinct from the former in the sense that they are associated with the propagation of plastic flow fronts in the deforming material. During the recent decades numerous investigations have addressed the generation of the above two classes of waves in a deforming solid [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The physical properties of these waves and the conditions favoring their generation have been studied extensively.…”