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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
If Schmid factor (m) value is larger than stress (σ), then it is enough to produce slip in a crystal. A change in orientation of stress axis in reference to the slip system will change the Schmid factor. Although CRSS and yield stress are material properties, both cannot be changed. From the experiments, Schmid established the relation and said that CRSS remains constant even though yield stress changes. The minimum stress is essential to induce yielding in a single crystal, with respect to orientation (i.e., ϕ = θ = 45° as follows σy = 2τCRSS ) as shown in Figure 2.9. Other than this orientation, the CRSS value exhibits zero when applied stress is parallel or perpendicular to the axis.
Plastic deformation and annealing
Published in Gregory N. Haidemenopoulos, Physical Metallurgy, 2018
Slip in a specific slip system is activated when the shear stress reaches a critical value, the critical resolved shear stress (CRSS). The orientation of a slip system relative to the applied tensile stress is expressed by the Schmid factor.
Effect of heat treatment on the FeCoCrNiMnAl high-entropy alloy cladding layer
Published in Surface Engineering, 2021
Yan Cui, Junqi Shen, Sunusi Marwana Manladan, Keping Geng, Shengsun Hu
The criterion for the commencement of slip in crystal materials can be expressed according to the following equation [28]: where cosφcosλ is the ‘Schmid factor’ or ‘orientation factor’, as shown in Figure 6(e). Based on the criterion, crystal slip occurs when the shear stress (F) acting on the slip plane along the slip direction is greater than a defined critical value. For a certain material constant (τc), the yield strength () of the material decreases with increasing Schmid factor. Generally, crystals with a large Schmid factor are said to have ‘soft orientation’ and those with a small Schmid factor are said to have ‘hard orientation’.
Anisotropic Radiation-Induced Changes in Type 316L Stainless Steel Rods Built by Laser Additive Manufacturing
Published in Nuclear Technology, 2019
Jordan A. Evans, Scott A. Anderson, Eric J. Faierson, Delia Perez-Nunez, Sean M. McDeavitt
The system on which slip occurs has the largest Schmid factor. While the Schmid factor is accurate for single crystal face-centered-cubic (fcc) metals, the Taylor factor has shown to be more applicable to polycrystalline metals.39 The Taylor factor M can be approximated by averaging the Schmid factor values for all the grains constituting the polycrystals (note that the Taylor factor reflects the greater constraint provided by the least-favorable oriented grains and is therefore not merely a geometric average). In other words, if a polycrystalline material has significant texture, then grains may exist that are preferentially oriented more favorably for slip than others, as is the case for the LAM specimens in this study (see Fig. 5). The Taylor factor is defined by Eq. (2):
Effect of elasto-plastic compatibility of grains on void-initiation criteria in low-carbon steel
Published in Philosophical Magazine Letters, 2019
In the present work, a potential crystallographic description for incompatible grains has been formulated and three microstructures (i.e. ultrafine, bimodal and coarse grained) are ranked based on an incompatibility criterion, formulated as the combined contribution of elastic incompatibility and plastic incompatibility. The elastic and plastic incompatibilities are characterised by the local elastic modulus difference and the local Schmid factor difference, respectively. Now, from Figure 4, it is evident that the tendency towards void nucleation in terms of elasto-plastic incompatibility is highest for the bimodal microstructure. A comparably lower difference in elastic moduli and Schmid factors gives rise to void initiation in this structure. From the perspective of void initiation, the bimodal structure is highly unstable. The ultrafine-grain microstructure requires grains with a moderately higher difference in elastic modulus to initiate voids compared to the bimodal one, which displays a lower degree of instability. The coarse-grained microstructure shows the lowest degree of instability as it requires grains with a higher mismatch in elastic modulus and Schmid factor to create voids. A probable reason for this behaviour is based on the processing schedules for the formation of these structures (Figure 1). Earlier studies showed that the bimodal microstructure has coarse grains with a dominance of alpha fibre texture (<110||RD>), whereas the fine grains embedded in it shows texture randomisation [16]. The ultrafine-grain sample possesses a random texture [20], while subsequent thermomechanical treatment develops an annealing texture in the coarse-grain structure.