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The theoretical yield strength of a perfect crystal is much higher than the observed stress at the initiation of plastic flow. [18] That experimentally measured yield strength is significantly lower than the expected theoretical value can be explained by the presence of dislocations and defects in the materials.
In general, the yield strength of a material is an adequate indicator of the material's mechanical strength. Considered in tandem with the fact that the yield strength is the parameter that predicts plastic deformation in the material, one can make informed decisions on how to increase the strength of a material depending on its microstructural ...
The actual yield—the quantity physically obtained from a chemical reaction conducted in a laboratory—is often less than the theoretical yield. [8] The theoretical yield is what would be obtained if all of the limiting reagent reacted to give the product in question. A more accurate yield is measured based on how much product was actually ...
Thus, to calculate the stoichiometry by mass, the number of molecules required for each reactant is expressed in moles and multiplied by the molar mass of each to give the mass of each reactant per mole of reaction. The mass ratios can be calculated by dividing each by the total in the whole reaction.
The theoretical strength can also be approximated using the fracture work per unit area, which result in slightly different numbers. However, the above derivation and final approximation is a commonly used metric for evaluating the advantages of a material's mechanical properties.
The quadratic Hill yield criterion for thin rolled plates (plane stress conditions) can be expressed as + (+) (+) + = where the principal stresses , are assumed to be aligned with the axes of anisotropy with in the rolling direction and perpendicular to the rolling direction, =, is the R-value in the rolling direction, and is the R-value perpendicular to the rolling direction.
Structural engineering depends upon a detailed knowledge of loads, physics and materials to understand and predict how structures support and resist self-weight and imposed loads. To apply the knowledge successfully structural engineers will need a detailed knowledge of mathematics and of relevant empirical and theoretical design codes.
The yield calculation will determine the safety factor until the part starts to deform plastically. The ultimate calculation will determine the safety factor until failure. In brittle materials the yield and ultimate strengths are often so close as to be indistinguishable, so it is usually acceptable to only calculate the ultimate safety factor.