Thermal Instability Strain in Dynamic Plastic Deformation

Culver, R.

doi:10.1007/978-1-4615-8696-8_29

Cited by 74 publications

(22 citation statements)

References 3 publications

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“…The present study indicates that one reason for the flow localization is deformation-heating-induced softening since the formation of shear bands is found to be associated with a critical strain. This is in agreement with a thermal instability model which is originally formalized by Culver [1973] and modified later by Semiatin and Jonas [1984]. This model yields a simple equation relating the critical shear strain γi for the onset of localization during high strain rate deformation to other experimentally determined material parameters:…”

Section: Efp Movement Direction Efp Movement Direction Efp Movement Dsupporting

confidence: 82%

Dynamic Response and Microstructure Evolution of Oxygen-Free High-Conductivity Copper Liner in Explosively Formed Projectile

Liu

Long

et al. 2017

Lat. Am. j. solids struct.

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The dynamic response and microstructure evolution of oxygen-free high-conductivity copper in a shaped charge liner are investigated through microstructural examination of a soft-recovery EFP. Adiabatic shear bands and voids which is the failure original of copper EFP can be observed in the rear part of the projectile. Numerical simulation results illustrate that the highest plastic strain reaches about 2.9 which can fully accommodate the grains deformation of copper EFP during the formation process at strain rates of the order of 10 4 s −1 . Theoretical calculation results indicate that the highest temperature increase of EFP caused by shock wave and plastic deformation can reach 747K, which is 0.55Tm (where Tm is the melting temperature of copper). The main body of the EFP undergoes completely dynamic recrystallisation, and the average size of the refined grains significantly decreases to approximately 10µm. A slight increase in grain size occurs mainly away from the center and extends towards the head and rear sections of the EFP. During the DRX process, the dislocation movement is believed to be the controlling mechanism significantly refining the microstructure.

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Section: Efp Movement Direction Efp Movement Direction Efp Movement Dsupporting

confidence: 82%

Dynamic Response and Microstructure Evolution of Oxygen-Free High-Conductivity Copper Liner in Explosively Formed Projectile

Liu

Long

et al. 2017

Lat. Am. j. solids struct.

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“…As can be seen in Table 1 the situation is the same for the under-aged 8090 Al-Li alloy. The existence of a critical strain for localization has been shown by Marchand and Duffy [42] and is predicted by the mechanical analyses [5][6][7][8][9][10][11][12]. In the simplest form the onset of localization should occur beyond the maximum of the stress in the adiabatic stress-strain curve (d|/dm =O).…”

Section: Critical Strain For the Occurrence Of Localizationmentioning

confidence: 99%

“…Mechanicians have focused their efforts on the constitutive description, developing criteria for instability of plastic flow. Examples are the analyses of Recht [5], Culver [6], Clifton [7], Bai [8], Curran et al [9], Burns and Trucano [10], Molinari and Clifton [11], and Wright [12]. Most of these approaches consist of a combination of a mechanical and thermal instability analysis.…”

Section: Introductionmentioning

confidence: 99%

Shear localization and recrystallization in dynamic deformation of 8090 Al–Li alloy

Zhong

Chen

et al. 2001

Materials Science and Engineering: A

191

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The microstructural evolution in localized shear deformation was investigated in an 8090 Al -Li alloy by split Hopkinson pressure bar (strain rate of approximately 10 3 s − 1) at ambient temperature and 77 K. The alloy was tested in the peak-, over-, under-, and natural-aged conditions, that provide a wide range of microstructural parameters and mechanical properties. Two types of localized shear bands were distinguished by optical microscopy: the deformed shear band and the white-etching shear band. They form at different stages of deformation during localization. There are critical strains for the occurrence of deformed and white-etching localized shear deformation, at the imposed strain rate. Observations by transmission electron microscopy reveal that the white-etching bands contain fine equiaxed grains; it is proposed that they are the result of recrystallization occurring during localization. The deformed-type bands are observed after testing at 77 K in all heat treatment conditions, but they are not as well defined as those developed at ambient temperature. Cracking often occurs along the localized shear at ambient temperature. The decrement in temperature is favorable for the nucleation, growth and coalescence of the microcracks along the shear bands, inducing fracture.

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“…5). In order to convert the true strain to the corresponding shear strain, the following equation, applicable to simple shear [35], was used:…”

Section: Constitutive Responses and Temperature Estimationmentioning

confidence: 99%

Self-organization of shear bands in stainless steel

Xue¹,

Nesterenko²,

Meyers³

2001

Fundamental Issues and Applications of Shock-Wave and High-Strain-Rate Phenomena

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The spatial distribution of shear bands was investigated in 304L stainless steel through the radial collapse of a thick-walled cylinder under high-strain-rate deformation (∼10 4 s −1 ). The shear-band initiation and propagation were also examined. Self-organization of multiple adiabatic shear bands was observed. The effect of grain size on spacing of shear bands was investigated at four different grain sizes: 30 m, 50 m, 140 m and 280 m. A single crystal with a similar composition was also tested. The experimental results show only a modest variation of shear-band spacing within the investigated grain size range. Three principal mechanisms are considered to be active in initiation: (a) momentum diffusion by stress unloading, (b) perturbation in the stress/strain/temperature fields, (c) microstructural inhomogeneities. The observed shear-band spacing is compared with existing theories; Grady-Kipp and Wright-Ockendon-Molinari theories. These are one-dimensional theories that do not consider the evolution in spacing as the shear bands grow. A discontinuous growth mode for shear localization under periodic perturbation is applied and predicts spacings in good agreement with observations. Self-organized initiation and propagation modes are discussed in relation to the interaction among the nucleus and well-developed shear bands.

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Thermal Instability Strain in Dynamic Plastic Deformation

Cited by 74 publications

References 3 publications

Dynamic Response and Microstructure Evolution of Oxygen-Free High-Conductivity Copper Liner in Explosively Formed Projectile

Dynamic Response and Microstructure Evolution of Oxygen-Free High-Conductivity Copper Liner in Explosively Formed Projectile

Shear localization and recrystallization in dynamic deformation of 8090 Al–Li alloy

Self-organization of shear bands in stainless steel

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