12/15/2023 0 Comments Crystalmaker cif file dextroseThis again leads to strain accumulation mediated crack propagation. Similarly, when a strain hardening material cannot undergo further hardening, the material cannot flow and dissipate fracture energy. Such a crack will soon accumulate enough strain and propagate catastrophically (assuming that this solid follows the critical strain based fracture criterion). On the other hand, strain softening materials allow strains to localize ahead of the crack tip, which is not good as the fracture energy is not dissipated in a wider region. Hence the whole strain hardening process and dislocation motion in this zone absorbs the crack driving force and arrests its propagation. This facilitates more fracture energy dissipation in the material. As strain hardened material can bear more load, the envelope over which plasticity can be sustained will increase. If the material strain hardens due to some barrier for dislocation motion, the area around the crack tip strain- hardens. However, there are two possibilities now. In a ductile metal, cracks cannot propagate easily because the area ahead of the crack tip allows dislocation motion and the material can plastically flow. For instance, pure Cu undergoes strain hardening when loaded in tension and this is the reason why it can be drawn into wires. Therefore, strain hardening is necessary for improving ductility. This is because the reduction in cross section area elevates the stress level in the specimen and since the material cannot strain harden, it cannot sustain the higher stress levels. Because, if materials tested in tension strain soften or are perfectly plastic (flow stress is constant) will start undergoing necking and fail prematurely. For example, metals that undergo strain hardening are more ductile than those which strain soften. Any material which has higher hardenability, is actually more ductile. Although a very stubborn resistance to plastic deformation does lead to brittle behavior, the process of hardening is actually quite important for structural reliability. However, hardness is simply resistance to plastic deformation. A solid is considered brittle when it offers no intrinsic resistance to crack propagation. Remember that both of them have very specific definitions. But hardness does not necessarily imply brittleness. How electron cloud density and local potential energy of a molecule/ motif/lattice point can be linked to total Gibbs free energy of molecule/lattice integrated over the whole structure? What are the statistical-mechanical formula that relates the two? and what are the prerequisites to understand such formula?įor most conventional materials, it is claimed, often incorrectly, that hardness and brittleness go hand in hand.Is there any mathematical method that finds out potential energy in an infinite 3D periodic lattice with distributed charges (say, theoretical calculation of Madelung constant)? What are the mathematical requirement/prerequisite to understand such formula?.But is there any limit of motif that can be included into the lattice without violating stoichiometry? How ab-initio calculation find out the appropriate motif to put into lattice to generate crystal structure? Without finding motifs, it is impossible to find crystal structures whose Gibbs free energy needs to be minimized. There can be only about 230 3D crystallographic lattices. Electronic structure of constituent elements from numerical solution of Quantum chemistry are also known. Suppose, chemical composition of the compound, temperature and pressure are known.
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