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Mechanical Behavior of Materials
Published in Snehanshu Pal, Bankim Chandra Ray, Molecular Dynamics Simulation of Nanostructured Materials, 2020
Snehanshu Pal, Bankim Chandra Ray
The relationship among the shear stress, slip planes, and slip directions through the slip plane are defined with the aid of law of CRSS. Critical resolved shear stress (CRSS) is well-defined as, slip initiates on the particular slip plane in particular slip direction, when the shear stress reaches a threshold value. It is also an indication that plastic deformation has started in the material. In simple manner, the point where yielding initiates in the material when it is subjected to minimum resolved shear stress is known as CRSS. Schmid’s law states that orientation of stress axis with respect to the slip system is not a dependency factor for CRSS.
Multiscale materials modelling: Procedures, examples and challenges
Published in Alphose Zingoni, Insights and Innovations in Structural Engineering, Mechanics and Computation, 2016
S. Schmauder, D. Rapp, P. Binkele, D. Molnar
The precipitation of dissolved Cu atoms is a relatively slow, statistical process which is modeled by Kinetic Monte Carlo (KMC) simulations. Therein a single vacancy performs countless random jumps with probabilities weighted according to mixing energies. Over time this leads to the formation of clusters of atoms of the same type, as this is energetically favorable in the Fe-Cu system. For determining each precipitate’s ability to hinder dislocation motion, Molecular Dynamics (MD) shear tests are performed, where a single dislocation is forced to interact with a precipitate particle by applying an external shear stress. The stress required for the dislocation to cut the precipitate is the Critical Resolved Shear Stress (CRSS), a well-known quantity in computational materials science. Using the different values for the CRSS, different precipitate configurations obtained from KMC simulations are used in Dislocation Dynamics (DD) simulations where the influence of the number and size of precipitates on the plastic behavior of a mesoscopic (µm3) simulation volume is considered by calculating the interactions of discrete dislocation segments. The change in the yield stress is denoted as the precipitation hardening value ∆σDD. Finally in order to determine the toughness of the material a macroscopic finite element model of a CT-specimen is used taking into account this value. As an additional step, further precipitate growth was simulated using the thermodynamically based Phase-Field Method (PFM), as KMC would need long time to achieve these late ageing states.
Resolved shear stress analytical modelling: application to the determination of CRSS in olivine thanks to dislocation electron tomography
Published in Philosophical Magazine, 2019
The plastic simulation of crystalline material, for example by finite element modelling or viscoplastic self-consistent code needs input parameters like critical resolved shear stresses (CRSS) for several temperatures. Generally, CRSS are obtained by performing compression or tensile tests of single crystals oriented in order to solicit specific slip systems. From a practical point of view, single crystals are oriented in order to get the highest Schmid factors for the slip systems of interest and the smallest Schmid factors for the easiest slip system [1–5]. Nervertheless, this method experiences some complications for some crystal structures. Actually, it is sometimes difficult, if not impossible to isolate a single slip system because several slip systems could have high Schmid factors at once. For example, considering olivine, the highest Schmid factor for the slip system cannot be isolated from the one [6,7]. Moreover, this technique encounters difficulties for brittle materials where failures occur before reaching flow stresses.
Temperature-dependent critical resolved shear stress model for (Cu–Au)–Co alloys in pure shear mode
Published in Philosophical Magazine, 2018
Jianzuo Ma, Weiguo Li, Jiaxing Shao, Yong Deng, Xianhe Zhang, Haibo Kou, Peiji Geng, Xuyao Zhang, Ying Li
The CRSS is the critical value of shear stress when dislocations begin to slip in metals [29]. The present paper attempts to establish a physics-based temperature-dependent CRSS model in pure shear mode from strict mathematic deducing based on the definition of maximum storage of energy when dislocations begin to slip in metals. To verify the model, the CRSS of Cu, Cu–Au, Cu–Co and Cu–Au–Co in pure shear mode are then predicted and compared with these from experiments. This work offers an approach to predict the temperature-dependent CRSS for metal materials in pure shear mode.