A dislocation-based constitutive description for modeling the behavior of FCC metals within wide ranges of strain rate and temperature

Abstract

a b s t r a c tIn this work a dislocation based constitutive description for modeling the thermo visco plastic behavior of FCC metals has been developed. The constitutive description, which is founded on the concepts of thermal activation analysis and dislocation dynamics, assumes the plastic flow additively decomposed into internal stress and effective stress. The internal stress represents the applied stress required for the transmission of plastic flow between the polycrystal grains and it is defined by the Hall Petch relationship. The effective stress formulation, which is the main innovative feature of this work, represents the thermally activated deformation behavior. This is defined taking into account the interrelationship between strain rate and temperature, and gathers structural evolution dependence. This structural evolution is described as a function of dislocations density, which acts as internal state variable in the material deformation behavior. A systematic procedure for identifica tion of the material parameters is developed and the model is applied to define the behav ior of annealed OFHC copper. The analytical predictions of the constitutive description are compared with the experimental data reported by Nemat Nasser and Li (Nemat Nasser, S., Li, Y., (1998). Flow stress of FCC polycrystals with application to OFHC Copper. Acta Mater. 46, 565 577). Good correlation between experiments and analytical predictions is found within wide ranges of strain rate and temperature.

Insights into the Mechanism of the Mechanochemical Formation of Metastable Phases

“…The sulfur penetrates still further into the bulk of the copper ( k 2 ′ ∼ 4 per pass, Table ), in agreement with predictions from measurements of the surface-to-bulk transport kinetics (Figure , Inset). Thus, the surface-to-bulk transport rate of sulfur in crystalline regions of the copper sample scales with the dislocation density as evidenced by the plot in Figure , implying that strain-rate sensitivity depends on the dislocation density . Note that the dislocation glide has been proposed as a mechanism for alloy formation during high-energy ball milling. − …”

“…density. 65 Note that the dislocation glide has been proposed as a mechanism for alloy formation during high-energy ball milling. 16−18 However, in the case of a sample annealed at 500 K (Figure 6), some sulfur is detected even deeper in the copper in linear regions that coincide with the location of grain boundaries that are identified by electron microscopy (Figure S1d), suggesting that sulfur can also diffuse along grain boundaries.…”

A new constitutive model for polymeric matrices: Application to biomedical materials

“…Moreover, strain hardening also plays a stabilizing role in necking formation [58][59][60]. In addition, thermal softening also influences the deformation process of thermoplastic polymers [61][62][63][64][65], as observed in other ductile materials [66,67]. In this regard, understanding this as a negative hardening, if temperature evolution occurs heterogeneously by inelastic dissipation, local necking is favoured leading to instability in the zone that reaches higher temperatures.…”

Material Behavior Description for a Large Range of Strain Rates from Low to High Temperatures: Application to High Strength Steel

“…The Rusinek-Klepaczko semi-physical model reported in [1] is initially based on the theory of dislocations and the model proposed by Klepaczko [30]. This study deals with the original version reported in [1], although several authors [31][32][33] have proposed an extended version of this model. It decomposes the equivalent stress in an internal stress σ µ , related to long-range obstacles and an effective stress σ * , related to short range obstacles, as in Equation (12) σ ε p ,ε p ,…”