On rate sensitivity of f.c.c. metals, instantaneous rate sensitivity and rate sensitivity of strain hardening

Klepaczko, J.R.; Chiem, C.Y.

doi:10.1016/0022-5096(86)90004-9

Cited by 151 publications

(64 citation statements)

References 22 publications

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“…This behavior cannot be described by equa- .6 whereas dashed line shows model p&diction for g, = 1, which is the actual value measured at ( = 1800 s-' and c = 0.52 and listed in Table 1. tion (10) unless the initial strain hardening rate is allowed to vary with strain rate. Thus, the observed variation of 8, with c' is not a function of the particular evolutionary law chosen; it instead indicates a general and unique finding which has not been noted previously, at least in the context of the basic model represented by equation (10). The variation of the initial strain hardening rate with strain rate was illustrated in Fig.…”

Section: Initial Strain Hardening Ratementioning

confidence: 80%

“…The key to the successful app~~tion of equation (10) to the description of structure evolution is the choice of the function F. Several functions were investigated, including the simple Vote law [equation (IO)], the modified Vote law proposed by Es&in and Mecking [IS] and a Vote law coupled with a linear strain hardening expression at large strains [20]. To fit the evolutionary equations to the mechanical threshold stress data the factors 8, and gS were varied iteratively until the Iowest error between the experimental data points and the predicted (f--~ curve was achieved.…”

Section: Application Of the Results To The Description Of Structure Ementioning

confidence: 99%

“…That is, the strain hardening rate continues to decrease toward zero with increasing stress or strain, but true ~tu~tion behavior is rarely observed. For this study, we will concentrate on strains < 1, assume that the strain hardening curves do saturate, and model the strain hardening behavior using an equation of the form e=f+-F(S)], (10) where the function F is chosen to fit the measured data. In equation (10) as in equation (9) the tern, perature and strain rate dependencies lie in the saturation threshold stress 6,.…”

Section: Structure Evolutionmentioning

confidence: 99%

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A constitutive description of the deformation of copper based on the use of the mechanical threshold stress as an internal state variable

1988

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At&ra&--Tlx ascetic &f&nation behavior of 0.9999 cu is investi~t~ at strain rates from IO-' to IO4 s-l. The variations of the flow stress and of the mechanical threshold stress (the flow stress at 0 K), which is used as an internal state variable, with strain rate and strain are measured. The experimental results are analyzed using a model proposed by Kocks and Making: results at constant structure are described with thermal activation theory; structure evolution (strain and strain rate evolution of the mechanical threshold stress) is treated by the sum of dislocation generation and dynamic recovery processes. A significant result is that the athermal dislocation accumulation rate, or Stage II hardening rate, becomes a strong function of strain rate at strain rates exceeding IO's_'. This leads to the apparent increased strain rate sensitivity seen in a plot of flow stress at a given strain vs the logarithm of strain rate. An explanation is proposed for the strain rate dependence of this initial strain hardening rate based on the limiting dislocation velocity and average distance between Obstacles.R&urn&--Nous Ctudions la deformation de symetrie axiale dun cuivre 4N pour de-s vitesses de deformation allant de lO-4 s-I a IO's_'. En fonction de la vitesse de deformation et de la deformation, nous mesurons Ies variations de la contrainte d%coulement et de la'&ntrainte seuil mbanique (la contrainte d'6coulement a OK) que l'on utilise comme variable d'etat inteme. Nous analysons les resultats expirimentaux a I'aide d'un modele propose par Kocks et Mecking: les resuhats P structure constante sont d&its par une theorie d'activation thermique; l'tvolution de la structure (evolution du seuil de contrainte m&anique en fonction de la deformation et de la vitesse de deformation) est trait&. par la combinaison des m&canismes de creation des dislocations et de restauration dynamique. Un r&n&at important est I soulingner: la vitesse ~a~umulation athermique des dislocations, ou vitesse de consolidation du stade II, commence ii d&per&e fortement de la vitesse de deformation pour des vitesses de deformation sup&ieures a IO3 s-l. Qci conduit a l'influence apparente accrue de la vitesse de deformation que t'on observe sur les courbes de la contrainte d%couIement a deformation don&e en fonction du Iogarithme de la vitesse de deformation. Nous proposons une explication de l'influence de la vitesse de deformation sur la vitesse de consolidation initiale, explication fond& sur la vitesse Iimite des dislocations et la distance moyenne entre les obstacles,

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Section: Initial Strain Hardening Ratementioning

confidence: 80%

Section: Application Of the Results To The Description Of Structure Ementioning

confidence: 99%

Section: Structure Evolutionmentioning

confidence: 99%

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A constitutive description of the deformation of copper based on the use of the mechanical threshold stress as an internal state variable

1988

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“…Klepaczko and Chiem [31] proposed a general balance equation to describe the strain-induced evolution of material microstructure based on the accumulation and recovery of dislocations. Gao and Zhang [25] further developed this general law in association with the effect of extreme strain rate and proposed a unified constitutive model for thermal stress as follows:…”

Section: Constitutive Modellingmentioning

confidence: 99%

Influences of temperature and grain size on the material deformability in microforming process

Jiang

Zhao

et al. 2016

Int J Mater Form

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This paper investigated the influences of temperature and grain size on the deformability of pure copper in micro compression process. Based on the dislocation theory, a constitutive model was proposed taking into account the influences of forming temperature, Hall-Petch relationship and surface layer model. Vacuum heat treatment was employed to obtain various grain sizes of cylindrical workpieces, and then laser heating method was applied to heat workpieces during microforming process. Finite element (FE) simulation was also performed, with simulated values agreed well with the experimental results in terms of metal flow stress. Both the FE simulated and experimental results indicate that forming temperature and grain size have a significant influence on the accuracy of the produced product shape and metal flow behaviour in microforming due to the inhomogeneity within the deformed material. The mechanical behaviour of the material is found to be more sensitive to forming temperature when the workpieces are constituted of fine grains. experimental results indicate that forming temperature and grain size have a significant influence on the accuracy of the produced product shape and metal flow behaviour in microforming due to the inhomogeneity within the deformed material. The mechanical behaviour of the material is found to be more sensitive to forming temperature when the workpieces are constituted of fine grains.

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“…In order to fully control the process of plastic deformation, the influence of strain rate on the mechanics of plastic flow (yield stress, strain heterogeneity, etc.) should be investigated [1]. However, at present, the possibility of testing and determining the characteristics of materials under high strain rates is limited by the availability of research equipment, the ambiguity of the applied methods and procedures, and the complexity of the phenomena of deformation.…”

Section: Introductionmentioning

confidence: 99%

Designing an impact energy-absorbing device: numerical simulations

Ryzińska¹,

Skrzat²

2015

ZN PRz Mechanika

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The numerical results of 1100-aluminium extrusion tests conducted at a tool velocity of 36 km/h are presented. Engineering applications of the considered problem concern the use of this extrusion technology in the design of an impact energyabsorbing device. Viscous and plastic properties of the extruded materials are described on the basis of numerical simulations of a tensile test in which the BodnerPartom material model is applied. The numerical results are compared with experimental ones.

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On rate sensitivity of f.c.c. metals, instantaneous rate sensitivity and rate sensitivity of strain hardening

Cited by 151 publications

References 22 publications

A constitutive description of the deformation of copper based on the use of the mechanical threshold stress as an internal state variable

A constitutive description of the deformation of copper based on the use of the mechanical threshold stress as an internal state variable

Influences of temperature and grain size on the material deformability in microforming process

Designing an impact energy-absorbing device: numerical simulations

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