Strain Localization in Energetic and Inert Granular Materials

Walley, S. M.

doi:10.1016/b978-0-08-097781-2.00007-1

Cited by 6 publications

(6 citation statements)

References 161 publications

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“…The occurrence of shear bands in ductile polycrystalline metals has long received particular attention because of their adverse consequences for material failure in processing applications involving large material deformation such as forming [9,10] (also see [11]), machining [12] and wear (tribology) [13]. In addition, shear banding is now recognized as an important mechanism for fracture in high-strain-rate applications such as shock and impact [14,15]; and is also considered as one of the 'hot-spot' ignition mechanisms in powdered and granular explosives [16].…”

Section: Introductionmentioning

confidence: 99%

In situ analysis of shear bands and boundary layer formation in metals

Yadav

Sagapuram

2020

Proc. R. Soc. A.

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Shear banding is a plastic instability in large deformation of solids where the flow becomes concentrated in narrow layers, with broad implications in materials processing applications and dynamic failure of metals. Given the extremely small length and time scales involved, several challenges persist in studying the development of shear bands. Here, we present a new approach to study shear bands at low speeds using low melting point alloys. We use in situ imaging to directly capture the essential features of shear banding, including transition from homogeneous to shear banded flow, band nucleation and propagation dynamics, and temporal evolution of the flow around a developing band. High-resolution, time-resolved measurements of the local displacement and velocity profiles during shear band growth are presented. The experiments are complemented by an analysis of the shear band growth as a Bingham fluid flow. It is shown that shear banding occurs only beyond a critical shear stress and is accompanied by a sharp drop in the viscosity by several orders of magnitude, analogous to the yielding transition in yield-stress fluids. Likewise, the displacement field around a nucleated band evolves in a manner that resembles boundary layer formation, with the band thickness scaling with time as a power law.

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Section: Introductionmentioning

confidence: 99%

In situ analysis of shear bands and boundary layer formation in metals

Yadav

Sagapuram

2020

Proc. R. Soc. A.

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“…Clearly, a detailed understanding of shear band onset characteristics is of critical importance for both quantifying conditions required for banding and designing practical means to control it [6,8,9]. While most extensively studied in the context of polycrystalline metals, shear banding has been also widely observed in other material systems such as metallic glasses [10][11][12][13], polymers [14,15] and granular media [16,17].…”

Section: Introductionmentioning

confidence: 99%

Nucleation properties of isolated shear bands

Yadav

Sagapuram

2020

Proc. R. Soc. A.

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Shear banding, or localization of intense strains along narrow bands, is a plastic instability in solids with important implications for material failure in a wide range of materials and across length scales. In this article, we report on a series of experiments on the nucleation of single isolated shear bands in three model alloys. Nucleation kinetics of isolated bands and characteristic stresses are studied using high-speed in situ imaging and parallel force measurements. The results demonstrate the existence of a critical shear stress required for band nucleation. The nucleation stress bears little dependence on the normal stress and is proportional to the shear modulus. These properties are quite akin to those governing the onset of dislocation slip in crystalline solids. A change in the flow mode from shear banding to homogeneous plastic flow occurs at stress levels below the nucleation stress. Phase diagrams delineating the strain, strain rate and temperature domains where these two contrasting flow modes occur are presented. Our work enables interpretation of shear band nucleation as a crystal lattice instability due to (stress-assisted) breakdown of dislocation barriers, with quantitative experimental support in terms of stresses and the activation energy.

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“…So, John was also able to sell Stephen's services to sponsors of research to perform literature reviews on subjects they were interested in. This has led to Stephen to writing a number of published research reviews on a wide range of topics including: experimental methods at high rates of strain [76,77], elastic wave propagation in materials [78,79], impact sensitivity of explosives [67,80], shear localization [81,82], indentation hardness [83] solid particle erosion [14], and the high rate properties of ceramics [84] and glasses [85]. This set Stephen up well for his retirement where he has continued to write historical reviews on various topics to do with the high-rate mechanical properties of materials [86][87][88][89][90][91][92].…”

Section: Stephen M Walley Research Associate Cavendish Laboratory University Of Cambridge Phd Awarded 1982-erosion Of Polyethylene By Solmentioning

confidence: 99%