Through this third paper of the three-paper series, two formulae, called Nori Fatigue Formulae, are presented for calculation of maximum allowable fatigue stress for components and structures with significant stress-raisers. Further, this paper provides formulae required for several other mechanical design applications. These formulae will eliminate the usage of code-sensitive safety factors along with other factored values from the entire mechanical design engineering work ranging from a safety-pin to spacecraft. The first formula gives the maximum allowable fatigue stress in tension, and the second formula gives the maximum allowable fatigue stress in shear. These formulae are developed through deployment of all the fundamental mechanical properties of steel like ultimate tensile strength (T), yield strength (Y), reduction of area (R) and elongation (E) that are commonly obtained from the engineering stress-strain curve resulting from the globally standardized tensile test. Thus, the vast amount of data, reduction of area and elongation, currently available with the world is put to effective use for calculation of maximum allowable fatigue stress of a given material in the given condition for the given application. As a result, application of Nori Fatigue Formulae does not call for generation of additional data that often calls for huge investment of time and money. Work in this direction, hitherto unavailable, is found essential since different international design codes, standards and handbooks have been adopting different design philosophies and different design factors that are different at different times for arriving at the maximum allowable fatigue stress.
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