A review on the strain rate dependency of the dynamic viscoplastic response of FCC metals

Salvado, Francisco C.; Teixeira-Dias, Filipe; Walley, S. M.; Lea, Lewis; Cardoso, João B.

doi:10.1016/j.pmatsci.2017.04.004

Cited by 97 publications

(42 citation statements)

References 145 publications

(285 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The proposed concept is quite different from the celebrated strength models introduced by Zerilli and Armstrong [18], Johnson and Cook [19], Follansbee and Kocks [20], Preston, Tonks and Wallace [21], among others [22]. The models are based on a salient assumption that the yield stress carries all H p results from slip events along many θ planes defined by two orthogonal unit vectors, n θ and s θ .…”

Section: Introductionmentioning

confidence: 98%

Mechanisms-Based Transitional Viscoplasticity

Zubelewicz

2020

Crystals

View full text Add to dashboard Cite

When metal is subjected to extreme strain rates, the conversation of energy to plastic power, the subsequent heat production and the growth of damages may lag behind the rate of loading. The imbalance alters deformation pathways and activates micro-dynamic excitations. The excitations immobilize dislocation, are responsible for the stress upturn and magnify plasticity-induced heating. The main conclusion of this study is that dynamic strengthening, plasticity-induced heating, grain size strengthening and the processes of microstructural relaxation are inseparable phenomena. Here, the phenomena are discussed in semi-independent sections, and then, are assembled into a unified constitutive model. The model is first tested under simple loading conditions and, later, is validated in a numerical analysis of the plate impact problem, where a copper flyer strikes a copper target with a velocity of 308 m/s. It should be stated that the simulations are performed with the use of the deformable discrete element method, which is designed for monitoring translations and rotations of deformable particles. relevant material information, such as sensitivities to strain rate, temperature, size effect, etc. In a typical scenario, the models adapt the strain rate-insensitive solving scheme, where radial return seems to be the favorite procedure. In consequence, plastic strain is merely a byproduct of the requirement that stress must adhere to the yield surface. An interesting technique suitable for generating random dislocation arrangements is proposed by Gurrutxanga-Lerma [23]. The main concern of the study is focused on how a given population of dislocation structures influences the dominant features of the stress field. The stochastic analysis provides justification for Taylor's equation and the Hall-Petch relation. The study, however, is not concerned with how the dislocation structures are formed in the first place. Another approach to crystal plasticity is proposed by Langer [24]. His thermodynamics dislocation theory (TDT) is based on the observation that dislocation experience complex chaotic motions and the motion is responsible for the field fluctuations. One should expect the frequency of the fluctuations to be many orders of magnitude lower in comparison with the frequency of thermal excitations. According to Langer, the non-deterministic nature of dislocation dynamics makes the behaviors suitable for statistical and thermodynamics treatment. Brown [25] offered an interesting idea that plastic flow is responsible for the formation of dislocation structures in the state of self-organized criticality. In this interpretation, the dislocation structures evolve until reaching the state of maximum structural adaptiveness such that every site of the structure has a statistically equal chance to act as a nucleation site of further deformation. At the initial stages of plastic deformation, flow is initiated at points of weakness. However, as the process proceeds, the initiation sites become inactive and are replaced by newly cre...

show abstract

Section: Introductionmentioning

confidence: 98%

Mechanisms-Based Transitional Viscoplasticity

Zubelewicz

2020

Crystals

View full text Add to dashboard Cite

show abstract

“…These are only few examples of an extensive literature. A detailed review of experimental testing and modelling for bcc metals can be found in [22,23] and more recently in [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Flow Stress of bcc Metals over a Wide Range of Temperature and Strain Rates

Testa

Bonora

Ruggiero

et al. 2020

Metals

View full text Add to dashboard Cite

A physical-based model for the flow stress of bcc metals is presented. Here, thermally activated and viscous drag regimes are considered. For the thermally activated component of the flow stress, the diffusion-controlled regime at elevated temperature is also taken into account assuming the non-linear dependence of the activation volume on temperature. The model was applied to A508 (16MND5) steel showing the possibility to accurately describe the variation of the flow stress over the entire temperature range (from 0 K to Tm) and over a wide strain-rate range.

show abstract

“…Often, it is assumed 4 that the thermally activated dislocation mechanism operates at all strain rates, while others 5 have argued that both thermal activation and drag-controlled mechanisms coexist at high strain rates. A comprehensive review of the theoretical concepts and models is presented in refs 6,7 . In various constitutive descriptions, the effort is focused on connecting the material responses at high strain rates with the rapid increase of dislocation density and the development of fine dislocation structures.…”

Section: Introductionmentioning

confidence: 99%

Metal behavior in the extremes of dynamics

Zubelewicz

2018

Sci Rep

View full text Add to dashboard Cite

When the rate of loading is faster than the rate at which material absorbs and converts energy to plastic work and damages, then there is an excess of energy that is partly stored in the material's microstructure and the rest of it triggers micro-dynamic excitations. The additional storage necessitates the development of plastic flow constraints and is directly responsible for the observed dynamic strengthening. At extreme conditions, we find that the micro-excitations contribute to the dynamic behavior. The phenomena are universally observed in metals, frictional materials and polymers. In essence, strong dynamics creates conditions at which materials are pushed from equilibrium and temporarily reside in an excited state of behavior. This study is focused on the behavior of metals. The concept is incorporated into a mechanisms-based constitutive model and is examined for annealed OFHC copper.When energy is delivered to a material with rates that are faster than the rate at which the material converts the excess energy to plastic work, then the uncompensated energy is partly stored in the material, while the rest of it is converted to micro-dynamic excitations. In metals, the observed strengthening mechanism 1 is linked to kinetics of the drag-controlled dislocation glide under applied stress 2,3 . Often, it is assumed 4 that the thermally activated dislocation mechanism operates at all strain rates, while others 5 have argued that both thermal activation and drag-controlled mechanisms coexist at high strain rates. A comprehensive review of the theoretical concepts and models is presented in refs 6,7 . In various constitutive descriptions, the effort is focused on connecting the material responses at high strain rates with the rapid increase of dislocation density and the development of fine dislocation structures. Subsequently, the microstructural evolution is coupled with external stimuli such as strain rate and temperature.Experimental observations presented in ref. 8 suggest that the dynamic behaviors arise due to the intrinsic resistance of lattice to motion of dislocations. This mechanism competes with an extrinsic resistance exerted by defects such as vacancies, interstitials and dislocations. The phenomena are studied with the use of standard split-Hopkinson pressure bar and Taylor cylinder tests 9 , where the achievable strain rates are in the range of 10 4 /s. The experiments have been further modified for a combined pressure-shear loading 8 , and then, the strain rates can reach a range of 10 5 /s to nearly 10 7 /s. As reported, the strain rates produce thermal instabilities and the fraction of plastic work converted to heat is much lower from the common ratio of β = 0.9. Even stronger loading is achieved in gas gun experiments, where energy is delivered in much shorter times 10 . The micro-dynamic excitations are consistently detected in acoustic emission (AE) measurements. In metals and rocks, the rate of AE counts is proportional to the rate of plastic strain 11,12 , where in metals bursts of acous...

show abstract

A review on the strain rate dependency of the dynamic viscoplastic response of FCC metals

Cited by 97 publications

References 145 publications

Mechanisms-Based Transitional Viscoplasticity

Mechanisms-Based Transitional Viscoplasticity

Flow Stress of bcc Metals over a Wide Range of Temperature and Strain Rates

Metal behavior in the extremes of dynamics

Contact Info

Product

Resources

About