Complexity of shear localization in a Zr-based bulk metallic glass

Applied Physics Letters

2011

We present an analysis of fractal geometry of extensive and complex shear band patterns in a severely deformed metallic glass. We show that the shear band patterns have fractal characteristics, and the fractal dimensions are determined by the stress noise induced by the interaction between shear bands. A theoretical model of the spatial evolution of multiple shear bands is proposed in which the collective shear bands slide is considered as a stochastic process far from thermodynamic equilibrium.

mentioning

confidence: 99%

Fractal nature of multiple shear bands in severely deformed metallic glass

Sun

Applied Physics Letters

2011

“…Both a full-field visualization, and a dynamic evaluation of the strain are profiled simultaneously on a local level. The DIC technique has been previously applied to investigate the strain localization behavior, such as shear banding in MGs [29][30][31], whisker growth [32], crack growth in ceramics [33], damage measurement in rocks [34] etc. In these work, the DIC technique could accurately estimate the local strength of materials [35], locate the initiation place of micro-crack [36], and evaluate the maximum strain value for failure [37].…”

Section: Introductionmentioning

confidence: 99%

Strain-energy transport during fracture of metallic glasses

Journal of Alloys and Compounds

et al. 2016

In a strained metallic glass (MG), depending on its fracture toughness, the failure mode can be dominated by shear-banding failure (for tough MGs) or cracking failure (for brittle MGs). During the fracture process, crack formation and propagation create a nonlinear strain field at crack tip. The transportation of the strain energy stored in the strained MG to the crack tip is of importance in understanding the deformation mechanism of MGs. By using digital image correlation method, we perform direct and precise measurements of the strain concentration, including maximum strain value and the strain-energy distribution, in four MGs. After yielding, plastic deformation is localized into shear bands or crack tip in a scale of micrometer, which means a systematic transition from the linear elastic behavior to the strongly nonlinear behavior. Through quantitatively evaluating the balance between the fracture energy and the strain-energy density, the failure modes are discussed based on a hyperelasticity model. This result provides a comprehensive picture of how remotely applied forces drive MGs failure in the fundamentals of fracture states.

“…Sequential digital images of sample surfaces are recorded during deformation and these images are post-processed to obtain strain fields based on a pattern-matching algorithm (Chu et al, 1985;Sutton et al, 2009). Because it provides a full-field 5 strain map, the DIC method is ideal for in situ investigation of localized deformation behavior in BMGs (Zhang et al, 2009;Joo et al, 2013). For example, Joo et al (2013) measured the shear band arrangements under different strain rates using DIC, and analyzed the dependence of deformation mode and fracture mechanism on strain rate.…”

Section: Introductionmentioning

confidence: 99%

Deformation-induced spatiotemporal fluctuation, evolution and localization of strain fields in a bulk metallic glass

Bei

International Journal of Plasticity

et al. 2015

Deformation behavior and local strain evolutions upon loading and unloading of a bulk metallic glass (BMG) were systematically investigated by in situ digital image correlation (DIC). Distinct fluctuations and irreversible local strains were observed before the onset of macroscopic yielding. Statistical analysis shows that these fluctuations might be related to intrinsic structural heterogeneities, and that the evolution history and characteristics of local strain fields play an important role in the subsequent initiation of shear bands. Effects of sample size, pre-strain, and loading conditions were systematically analyzed in terms of the probability distributions of the resulting local strain fields. It is found that a higher degree of local shear strain heterogeneity corresponds to a more ductile stress-strain curve. Implications of these findings are discussed for the design of new materials.