Flow stress of f.c.c. polycrystals with application to OFHC Cu

Nemat‐Nasser, Sia; Li, Yu Long

doi:10.1016/s1359-6454(97)00230-9

Cited by 219 publications

(136 citation statements)

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“…As the strain rate increases from quasi-static conditions to approximately 10 3 s À1 , a linear relationship is maintained between the flow stress and the logarithm of the strain rate. 1,2) Deformation at these strain rates has been well explained by the mechanism of thermal activation of dislocations over short-range barriers.…”

Section: Introductionmentioning

confidence: 94%

The Effect of Strain Rate on the Impact Behaviour of Fe–2 mass% Ni Sintered Alloy

Lee

Chou

2005

Mater. Trans.

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The impact behaviour of Fe-2 mass% Ni sintered alloy as a function of strain rate has been studied using a material testing system at strain rate of 10 À3 , 10 À2 and 10 À1 s À1 and a split Hopkinson bar at strain rates ranging from 2:5 Â 10 3 s À1 to 6:8 Â 10 3 s À1 . The mechanical properties of the sintered alloy, including its impact strength, rate of work hardening and strain rate sensitivity are found to be significantly influenced by the strain rate at which deformation takes place. A constitutive law based on the Khan-Huang-Liang model is applied to predict the ratedependent plastic flow behaviour of the sintered alloy. The model predictions are found to be in good agreement with the observed experimental response. Even under heavy deformation conditions, none of the specimens were observed to fracture. Microstructural observations reveal that the grain size of the deformed specimen decreases as the strain rate increases. The reduction of the grain size can lead to an increase of the flow stress due to the enhancement of the grain boundary area.

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Section: Introductionmentioning

confidence: 94%

The Effect of Strain Rate on the Impact Behaviour of Fe–2 mass% Ni Sintered Alloy

Lee

Chou

2005

Mater. Trans.

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“…A modi®ed version of this model has been successfully applied to OFHC copper by Nemat-Nasser and Li (1998). The model uses the basic concept that the resistance to the motion of dislocations, introduced by various microstructural barriers, de®nes the¯ow stress of metals (Kocks et al, 1975;Follansbee and Kocks, 1988;Follansbee and Gray III, 1989).…”

Section: A Physically Based Model For Dynamic Response Of Vanadiummentioning

confidence: 99%

High strain-rate response of commercially pure vanadium

Nemat‐Nasser

Guo

2000

Mechanics of Materials

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To understand the plastic¯ow behavior of commercially pure vanadium under high strain rates, uniaxial compression tests of cylindrical samples are performed using UCSD's enhanced Hopkinson technique. True strains exceeding 50% are achieved in these tests, over a range of temperature from 77 to 800 K at the strain rates of 2500 and 8000 s À1 . The microstructure of the deformed and undeformed samples is observed by an optical microscope. The initial microstructure (the initial dislocation density, the grain size and its distribution) is found to have a strong eect on the yield stress and the initial stages of the¯ow stress. This eect becomes more signi®cant with decreasing temperature. Deformation twins are observed. Their density is seen to increase with decreasing temperature. Adiabatic shearbands occur in vanadium at low temperatures. Finally, an experimentally based micromechanical model is developed for the dynamic response of this material. The model predictions are compared with the results of other high strain-rate tests which have not been used in the evaluation of the model parameters, and good agreement between the theoretical predictions and experimental results is obtained. In addition, the results of a series of low strain-rate tests are presented and brie¯y discussed. Ó

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“…Thus, it is inferred that 6061-T6 alloy has good ductility and strengthening properties under cryogenic temperatures and high strain rates. Figure 3(d) compares the stress-strain response of the current 6061-T6 alloy with that of Al-4Cu-0.5Zr, 25) UFGCu, 26) OFHC-Cu 27) and 3003 Al-Mn 28) under broadly equivalent loading conditions. The results show that the flow stress of 6061-T6 alloy is higher than that of UFG-Cu, OFHC-Cu and 3003 Al-Mn, but lower than that of Al-4Cu-0.5Zr.…”

Section: ¹1mentioning

confidence: 99%

Mechanical Properties and Dislocation Substructure of 6061-T6 Aluminum Alloy Impacted at Cryogenic Temperatures

Lee

Huang

2016

Mater. Trans.

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The mechanical properties and dislocation substructure of 6061-T6 aluminum alloy deformed at temperatures of 0°C, ¹100°C and ¹196°C and strain rates of 1000 s ¹1 , 3000 s ¹1 and 5000 s ¹1 are investigated using a compressive split-Hopkinson pressure bar. It is found that the flow stress and strain rate sensitivity increase with increasing strain rate, but decrease with increasing temperature. In addition, the work hardening rate decreases with increasing strain rate and temperature. The flow stress corresponding to a true strain of 0.6 is modelled using a power law expression with an activation energy of 1.7 kJ/mol and an average strain rate sensitivity of 0.154. The dislocation density increases with increasing strain rate and decreasing temperature, and leads to a greater flow stress. A greater multiplication and tangling of the dislocations occurs at higher strain rates and lower temperatures. The flow stress and square root of the dislocation density are linearly related via the BaileyHirsch type relation · ¼ · 0 þ ¡ 1 Gb ffiffiffi µ p , where ¡ 1 has a value of 0.46 for the current 6061-T6 aluminum alloy.

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Flow stress of f.c.c. polycrystals with application to OFHC Cu

Cited by 219 publications

References 13 publications

The Effect of Strain Rate on the Impact Behaviour of Fe–2 mass% Ni Sintered Alloy

The Effect of Strain Rate on the Impact Behaviour of Fe–2 mass% Ni Sintered Alloy

High strain-rate response of commercially pure vanadium

Mechanical Properties and Dislocation Substructure of 6061-T6 Aluminum Alloy Impacted at Cryogenic Temperatures

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Flow stress of f.c.c. polycrystals with application to OFHC Cu

Cited by 219 publications

References 13 publications

The Effect of Strain Rate on the Impact Behaviour of Fe&ndash;2 mass% Ni Sintered Alloy

The Effect of Strain Rate on the Impact Behaviour of Fe&ndash;2 mass% Ni Sintered Alloy

High strain-rate response of commercially pure vanadium

Mechanical Properties and Dislocation Substructure of 6061-T6 Aluminum Alloy Impacted at Cryogenic Temperatures

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The Effect of Strain Rate on the Impact Behaviour of Fe–2 mass% Ni Sintered Alloy

The Effect of Strain Rate on the Impact Behaviour of Fe–2 mass% Ni Sintered Alloy