A model for experimentally-observed high-strain-rate dynamic strain aging in titanium

Cheng, Jingyi; Nemat‐Nasser, Sia

doi:10.1016/s1359-6454(00)00124-5

Cited by 79 publications

(28 citation statements)

References 25 publications

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“…Equation [8] forms the basis of many subsequent analyses in the literature. [20,[29][30][31][32] Zbib and Aifantis, [33] working from the same assumptions as used in Reference 4 arrived at Eq. [8] by means of a nonlinear instability analysis using strain gradient plasticity.…”

Section: S<0 ½8mentioning

confidence: 99%

“…[18] Many authors have found that a distinguishing feature of DSA is the increased work-hardening rate. [19][20][21][22][23] The effect has been proposed as an alternative hardening mechanism to work hardening at room temperature by some investigators [24,25] or as an increased bake-hardening effect. [21] and Barnby [26] reported measurements of increased dislocation densities after deformation at temperatures up to 700 K (427°C).…”

Section: Introductionmentioning

confidence: 99%

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A Revised Criterion for the Portevin–Le Châtelier Effect Based on the Strain-Rate Sensitivity of the Work-Hardening Rate

Liempt

Sietsma

2011

Metall Mater Trans A

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An improved analysis is presented of the stability of plastic deformation under conditions where dynamic strain aging (DSA) occurs, which leads to instabilities known as the Portevin-Le Chaˆtelier (PLC) effect. It is shown that PLC instabilities can occur for conditions that are not covered by the currently prevailing criterion presented by Estrin and Kubin (1991), which focuses on a negative strain rate sensitivity of the flow stress, caused by interactions of solutes with thermally activated glide of mobile dislocations. The current analysis recognizes that the strain-rate sensitivity of the flow stress consists of two contributions, one associated with glide of mobile dislocations and the second with work hardening, related to storage of immobile dislocations. In this paper, an instability criterion is proposed that takes into account the possibility of a negative strain-rate sensitivity of the work-hardening rate, which is caused by diffusion of solutes to immobile dislocations. The latter contribution leads to an extended instability criterion. This criterion also provides an explanation for the existence of a critical strain above which instabilities occur. In this article, previously published tensile test data are used to show that a negative strain-rate sensitivity of the work-hardening rate, which influences significantly the occurrence of the PLC effect, can indeed occur under DSA conditions.

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Section: S<0 ½8mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Revised Criterion for the Portevin–Le Châtelier Effect Based on the Strain-Rate Sensitivity of the Work-Hardening Rate

Liempt

Sietsma

2011

Metall Mater Trans A

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“…The effects of strain rate, in particular, has proven challenging to predict. Several studies have observed the mechanical response of titanium under quasi-static [7,8,17,18] and dynamic loading [3,7,[19][20][21][22][23][24]. Existing mechanical test data, and with it understanding of active mechanisms in the dynamic loading regime, is fairly limited.…”

Section: Introductionmentioning

confidence: 99%

Characterization and Modeling of Titanium Single Crystals Following Dynamic Compression by Split‐Hopkinson Pressure Bar

Morrow¹,

Lebensohn²,

Trujillo³

et al. 2016

Proceedings of the 13th World Conference on Titanium

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Split-Hopkinson pressure bar (SHPB) was used to dynamically load single crystal titanium samples in two different orientations. Characterization of the resulting microstructure, especially twin activity, was performed to understand the observed mechanical behavior. Twinning was quantified using microtextures measured using electron backscatter diffraction (EBSD). Compressive twinning followed by secondary, tensile twinning was observed for both [0001] and [1011]-oriented crystals. Dislocations, though prevalent in the microstructure, contributed to final texture far less than twinning. The microstructures of the strained samples were heavily twinned after loading, and twin variants and corresponding textures were different as a function of initial orientation. Large amounts of dislocations were present, indicating that plasticity was achieved through slip and twinning together. Due to the severe deformation imparted to the samples, the pathway from initial to final states was difficult to discern using post-mortem characterization alone. Viscoplastic Self-Consistent (VPSC) modeling was used to determine the complex order of operations as a function of strain. Crystal orientation was found to play a large role in the activation of different mechanisms in each sample, even under these high strain rate conditions.

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Section: Introductionmentioning

confidence: 99%

“…Examples are , Meyers et al (1994), , Cheng and Nemat-Nasser (2000). The first investigation mentioned above was on Ti-6Al-4V alloy, while others were on commercially available pure alpha-titanium except in case of Cheng and Nemat-Nasser (2000), in which the microstructure, or phase, was not specified. The development of relatively economical Ti-6Al-4V alloy, with resulting high oxygen content, has sparked interest in its possible use in lightweight tanks (Montgomery and Wells, 2001); the conventional, more expensive Ti-6Al-4V alloy has been used primarily in aerospace components.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Multi-Axial Loading Response and Constitutive/Damage Modeling of Titanium and Titanium Alloys

Khan¹

2006

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Research ObjectivesTitanium alloys, and ceramics encapsulated in titanium alloys are considered for next generation of lightweight tanks. The objectives of this research project are to obtain responses of newly developed economical, but with much higher Oxygen content, Ti6Al-4V alloys, determine the suitability of existing constitutive relations to model these responses, and to determine material constants for these models (e.g., JC and KHL models) for incorporation in computer codes for penetration simulation.These objectives are being achieved through uniaxial loading experiments over a wide range of strain rates and temperatures in the first year of funding, and through multi-axial loading experiments over a wide strain rate range and a wide temperature range in the second and third year of funding, respectively. ApproachUniaxial compressive experiments, over a wide range of strain rates and temperatures, are used to determine material constants for two constitutive models (Johnson-Cook and Khan-Huang-Liang); experiments are performed on several titanium (Ti-6Al-4V) alloys. The results from these models are correlated to these experimental data to demonstrate the flexibility in each model. Most other investigators who have performed similar studies, stopped at this stage. The approach taken by other scientists is not right because if correlations are done with the same experiments from which the material constants are determined, then correlations should be always good for any constitutive model. We have gone one step further, which is very desirable, if not required, to validate a constitutive model. In the phase of the current year of funding, multi-axial loading experiments (e.g. dynamic torsion followed by dynamic compression using Kolsky or split Hopkinson bar technique, uniaxial compression followed by biaxial compression, etc) have been performed and compared to predictions from these two constitutive models to establish validity of these two models over a wide ranges of strain rates and temperatures. BackgroundSince the introduction of titanium and titanium alloys around 1950, they have become important materials for aerospace, energy, and chemical industries. They are used chiefly for parts that require good corrosion resistance, moderate strength up to 588 K, and lightweight. Titanium alloys, especially Ti-6Al-4V, an α+β type titanium alloy is largely used alloy in many industries because of its extremely attractive properties like high specific strength, good deformability, reasonable ductility and ability to withstand high temperatures and resistance to corrosion. It is primarily used in aero-engine, gas turbines and other applications. The development of a relatively economical Ti-6Al-4V alloy, with a low interstitial content has prompted a lot of interest in its possible use in armor tanks because of improved ductility, whereas the conventional more expensive Ti6Al-4V alloy has been used primarily in aerospace components chiefly because of its high strength to weight ratio. This advantage has al...

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A model for experimentally-observed high-strain-rate dynamic strain aging in titanium

Cited by 79 publications

References 25 publications

A Revised Criterion for the Portevin–Le Châtelier Effect Based on the Strain-Rate Sensitivity of the Work-Hardening Rate

A Revised Criterion for the Portevin–Le Châtelier Effect Based on the Strain-Rate Sensitivity of the Work-Hardening Rate

Characterization and Modeling of Titanium Single Crystals Following Dynamic Compression by Split‐Hopkinson Pressure Bar

Dynamic Multi-Axial Loading Response and Constitutive/Damage Modeling of Titanium and Titanium Alloys

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