Electro-magnetic collapse of thick-walled cylinders to investigate spontaneous shear localization

Lovinger, Zev; Rikanati, A.; Rosenberg, Z.; Rittel, D.

doi:10.1016/j.ijimpeng.2011.06.006

Cited by 48 publications

(27 citation statements)

References 12 publications

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“…Onset of strain localization (onset of necking) is reached at the weakest sections of the ring which are determined by the numerical round-off -i.e. numerical perturbations intrinsic to the FE analysis (Rusinek and Zaera, 2007;Lovinger et al, 2011). Once necking is nucleated at a certain material point, a release wave is generated.…”

Section: Symbol Property and Unitsmentioning

confidence: 99%

Identification of the critical wavelength responsible for the fragmentation of ductile rings expanding at very high strain rates

Rodríguez-Martínez

Vadillo

Fernández-Sáez

et al. 2013

Journal of the Mechanics and Physics of Solids

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A. (2013). Identification of the critical wavelength responsible for the fragmentation of ductile rings expanding at very high strain rates. Solids, 61, 6, 1357- Journal of the Mechanics and Physics of ández-Sáez tériaux UniversitéThis work examines the mechanisms governing the fragmentation of ductile rings expanding at very high strain rates. Based on previous works three different methodologies have been addressed, namely: fully 3D finite element computations of the radial expansion of ductile rings, numerical simulations of unitary axisymm etric cells with sinusoidal spatial imperfections subjected to tensile loading and a linear perturbation technique derived within a quasi-1D theoretical framework. The results derived from these three different approaches allow for identification of a critical wavelength which dictates the fragmentation of ductile rings expanding at very high strain rates. This critical wavelength is revealed quite independent of the material properties but closely related to the ratio (L 0 /ϕ 0 ) critical ≈1:5 where L 0 is the fragment size and ϕ 0 is the diameter of the circular section of the ring. This work highlights the fundamental role played by material inertia in the fragmentation at very high strain rates, setting aside the mechanisms associated to the classical statistical theories.

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Section: Symbol Property and Unitsmentioning

confidence: 99%

Identification of the critical wavelength responsible for the fragmentation of ductile rings expanding at very high strain rates

Rodríguez-Martínez

Vadillo

Fernández-Sáez

et al. 2013

Journal of the Mechanics and Physics of Solids

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“…The PCG was further detailed in [10]. The experimental set-up for expanding cylinders using the PCG is shown in Fig.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…Expanding cylinders were used in various works in the literature to measure strength [7] or fragmentation [8,9] at high rates, yet these experiments reach at most values of 10 4 sec −1 . Using our PCG, characterized by a fast rise time of about 1 µs [10], we manage to reach strain rates of ∼1e5, with no significant temperature rise, thus paving the way to a standard technique to measure strength at very high strain rates.…”

Section: Introductionmentioning

confidence: 99%

Investigating strength of materials at very high strain rates using magnetically driven expanding cylinders

Lovinger

Nemirovsky

Avriel

et al. 2015

EPJ Web of Conferences

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Abstract. Dynamic characterization of strength properties is done, in common practice by the means of a Split-Hopkinson Pressure Bar (also named Kolsky-Bar) apparatus. In such systems, strain rates are limited up to ∼ 5 · 10 3 sec −1 . For higher strain rates, the strain rate hardening is assumed to be the same as that measured at lower rates, with no direct measurement to validate the assumptions used for this extrapolation. In this work we are using a pulsed current generator (PCG) to create electro-magnetic (EM) driving forces on expanding cylinders. Most standard techniques for creating EM driving forces on cylinders or rings, as reported in the literature, reach strain rates of 1e3-1e4. Using our PCG, characterized by a fast rise time, we reach strain rates of ∼1e5, thus paving the way to a standard technique to measure strength at very high strain rates. To establish the experimental technique, we conducted a numerical study of the expanding cylinder set up using 2D hydrodynamic simulations to reach the desired high strain rates.

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“…A pronounced advantage of this loading technique is due to the more uniform collapse of the specimen, as compared with the explosively driven ones, which are also driven by an axial force due to the directional ignition of the explosive driver. More recently, we introduced an electromagnetically driven version of the TWC technique [14,15], using a pulsed current generator. This method has the advantage that it is highly controllable and somewhat simpler than the use of explosives or alternatively, the use of a large scale Mega-Joule energy facility.…”

Section: Introductionmentioning

confidence: 99%

“…This method has the advantage that it is highly controllable and somewhat simpler than the use of explosives or alternatively, the use of a large scale Mega-Joule energy facility. In a TWC experiment, one can measure the number, spacing and length of the spontaneously initiated EPJ Web of Conferences ASBs, as in [11] and [14]. Consequently, the TWC techniques, either explosive or electromagnetic, offer an ideal experimental platform to validate existing models for ASB formation, and use the data to calibrate material models for shear band formation.…”

Section: Introductionmentioning

confidence: 99%

On what controls the spacing of spontaneous adiabatic shear bands in collapsing thick-walled cylinders

Lovinger

Rosenberg

Rittel

2015

EPJ Web of Conferences

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Abstract. Shear bands formation in collapsing thick walled cylinders occurs in a spontaneous manner. The advantage of examining spontaneous, as opposed to forced shear localization, is that it highlights the inherent susceptibility of the material to adiabatic shear banding without prescribed geometrical constraints. The Thick-Walled Cylinder technique (TWC) provides a controllable and repeatable technique to create and study multiple adiabatic shear bands. The technique, reported in the literature uses an explosive cylinder to create the driving force, collapsing the cylindrical sample. Recently, we developed an electromagnetic set-up using a pulsed current generator to provide the collapsing force, replacing the use of explosives. Using this platform we examined the shear band evolution at different stages of formation in 7 metallic alloys, spanning a wide range of strength and failure properties. We examined the number of shear bands and spacing between them for the different materials to try and figure out what controls these parameters. The examination of the different materials enabled us to better comprehend the mechanisms which control the spatial distribution of multiple shear bands in this geometry. The results of these tests are discussed and compared to explosively driven collapsing TWC results in the literature and to existing analytical models for spontaneous adiabatic shear localization.

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Electro-magnetic collapse of thick-walled cylinders to investigate spontaneous shear localization

Cited by 48 publications

References 12 publications

Identification of the critical wavelength responsible for the fragmentation of ductile rings expanding at very high strain rates

Identification of the critical wavelength responsible for the fragmentation of ductile rings expanding at very high strain rates

Investigating strength of materials at very high strain rates using magnetically driven expanding cylinders

On what controls the spacing of spontaneous adiabatic shear bands in collapsing thick-walled cylinders

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