On the dynamics of localization and fragmentation-IV. Expansion of Al 6061-O tubes

Zhang, H.; Ravi‐Chandar, K.

doi:10.1007/s10704-009-9441-5

Cited by 57 publications

(18 citation statements)

References 26 publications

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“…The authors did, however, acknowledge the influence of such deformation mechanisms on the fragmentation characteristics. The works [12][13][14] made apparent that the fragmentation characteristics and the distribution of fragment size depend on the specific localization mechanism and pattern that develops before final fracture.…”

Section: Introductionmentioning

confidence: 99%

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Random distributions of initial porosity trigger regular necking patterns at high strain rates

et al. 2018

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At high strain rates, the fragmentation of expanding structures of ductile materials, in general, starts by the localization of plastic deformation in multiple necks. Two distinct mechanisms have been proposed to explain multiple necking and fragmentation process in ductile materials. One view is that the necking pattern is related to the distribution of material properties and defects. The second view is that it is due to the activation of specific instability modes of the structure. Following this, we investigate the emergence of necking patterns in porous ductile bars subjected to dynamic stretching at strain rates varying from 10 to 0.5×10 using finite-element calculations and linear stability analysis. In the calculations, the initial porosity (representative of the material defects) varies randomly along the bar. The computations revealed that, while the random distribution of initial porosity triggers the necking pattern, it barely affects the average neck spacing, especially, at higher strain rates. The average neck spacings obtained from the calculations are in close agreement with the predictions of the linear stability analysis. Our results also reveal that the necking pattern does not begin when the Considère condition is reached but is significantly delayed due to the stabilizing effect of inertia.

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Section: Introductionmentioning

confidence: 99%

“…More recently, Zhang & Ravi-Chandar [12][13][14] performed a series of experiments using aluminium and copper rings and cylinders expanded radially at strain rates ranging from 5 × 10 3 s −1 to 1.5 × 10 4 s −1 . The nominal wall thickness of the specimens in these experiments was 0.5 mm.…”

Section: Introductionmentioning

confidence: 99%

Random distributions of initial porosity trigger regular necking patterns at high strain rates

et al. 2018

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“…Zhang and Ravi-Chandar [2][3][4][5] reported recent experimental data for high-speed tangential extension to rupture of thin metallic rings by a magnetic pulse technique. Electro-magnetic loading provided radial expansion rates of the ring in the range 80-200 m/s or strain rates on the order of 10 4 s −1 .…”

Section: Introductionmentioning

confidence: 99%

Behavior of metals Induced by magnetic pulse loading

Svetlana

Morozov

Denis

et al. 2015

EPJ Web of Conferences

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Abstract. The investigation of copper and aluminum ring samples was carried out using magnetic pulse loading. Two modifications of the magnetic pulse technique were used. They were based on a GKVI-300 high-voltage narrow-pulse generator Morozov et al. (2011) [1]. It is possible using these two approaches to decrease the period of the harmonic load up to 100 ns. The study of fracture surfaces of aluminum and copper samples after the test was carried out on an optical microscope AxioObserver-Z1-M in a dark field, and study of the cross sections structure -in the bright field or C-DIC. The structure has been studied in cross sections after appropriate etching. Grain size and the number of pores on the surface of cross sections were determined after etching. Microhardness was measured on a PMT-3 device with a load of 20 g. The optical micrographs of aluminum demonstrate that the long pulse causes almost fully ductile fracture. In the case of the short pulse, the number of fibers decreases: the fracture surface exhibits the signs of both ductile cup fracture and brittle crystalline fracture with cracks, which are sometimes rather deep. In addition, the short pulse results in twinning, which seems surprising for aluminum featuring a high stacking fault energy. It is seen that under short loading dynamic recrystallization occurs. As for copper samples before loading they were in the form of single crystal and after loading their structure due to dynamic recrystallization consists of small grain. The specimen with notch has more developed dynamic recrystallization shear bands.

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“…The experiments are conducted with a pulse current generator (PCG) providing magnetic pressures as the driving force. 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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On the dynamics of localization and fragmentation-IV. Expansion of Al 6061-O tubes

Cited by 57 publications

References 26 publications

Random distributions of initial porosity trigger regular necking patterns at high strain rates

Random distributions of initial porosity trigger regular necking patterns at high strain rates

Behavior of metals Induced by magnetic pulse loading

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

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