Quality index of cast aluminum alloy is a measure to evaluate its quality based on tensile mechanical properties such as yield strength (YS), ultimate tensile strength (UTS), elongation to fracture (Ef) and strain energy density W.
Quality index Q0 evaluates material quality on the basis of the balance between YS and W, and it evaluates material’s potential in combination of tensile strength, ductility and toughness.
Its calculation formula involves strain energy density W as a term and W is calculated by integration of true stress–true strain tensile flow curve. So Q0 can be evaluated only if the tensile flow curve of the alloy is known and it may make the use of Q0 difficult.
Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, has developed an approximate formula for calculating Q0 according to YS, UTS and Ef without requiring W.
He developed approximate formulas for Q0 which are expressed as a function of YS, UTS and Ef using multiple linear and quadratic regression models, and evaluated their performances from the viewpoints of mean absolute error (MAE), mean relative error (MRE), determination coefficient (R2) and simplicity. The results demonstrated that they have excellent performances.
The MAE, MRE, R2 and F-statistic of the multiple linear regression model for Q0 are respectively 19.981 MPa, 3.792%, 0.944 and 523.344, and the MAE, MRE, R2 and F-statistic of the multiple quadratic regression model for Q0 are respectively 3.322MPa, 0.566%, 0.998 and 7 277.034.
These approximate formulas could be widely used to evaluate the quality of cast aluminum alloys for materials designers and engineers in practice.
You can find more information in his paper “Approximate formulas for quality index Q0 of cast aluminum alloys according to mechanical tensile properties using multiple linear and quadratic regression models” in “ International Journal on Interactive Design and Manufacturing” (EI).
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