New Design Formulae for Safety and Precision in the Fatigue Engineering of Mechanical Components and Structures

Year : 2026 | Volume : 16 | Issue : 01 | Page : 6 24
    By

    Nori VSN Murthy,

  1. , Independent Research Scientist, , India

Abstract

This paper introduces two new formulae, termed the Nori Fatigue Formulae, for determining the maximum allowable fatigue stress in mechanical components and structures with significant stress concentrations. 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 established by methodically using all the vital mechanical properties of steel—ultimate tensile strength (T), yield strength (Y), reduction of area (R), and elongation (E)—as obtained from the engineering stress–strain curve generated by the globally standardized tensile testing. This framework enables effective utilization of the vast amount of tensile- test databases already available worldwide, particularly reduction of area and elongation, for computing the maximum permissible fatigue stress of a given material in the given condition and application. Consequently, the proposed approach eliminates the need for generating additional experimental data, which often entails substantial investments of time and financial resources. Such a unified approach, previously unavailable, is essential in view of the divergent design philosophies and design factors adopted across international design codes, standards, and handbooks over time. To make this paper more comprehensive, several new formulae are provided in the Appendix-A for use in various design situations routinely encountered. Also provided additional applications for the formulae offered in the first two papers. Thus, this paper fully encompasses the previous two papers of this new-design-formulae series.

Keywords: Allowable stress, design stress, maximum permissible stress, maximum allowable fatigue stress, maximum working stress, maximum safe stress, design factor, factor of safety, safety margin, failure stress.

[This article belongs to Trends in Mechanical Engineering & Technology ]

How to cite this article:
Nori VSN Murthy. New Design Formulae for Safety and Precision in the Fatigue Engineering of Mechanical Components and Structures. Trends in Mechanical Engineering & Technology. 2026; 16(01):6-24.
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Nori VSN Murthy. New Design Formulae for Safety and Precision in the Fatigue Engineering of Mechanical Components and Structures. Trends in Mechanical Engineering & Technology. 2026; 16(01):6-24. Available from: https://journals.stmjournals.com/tmet/article=2026/view=235800


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Regular Issue Subscription Review Article
Volume 16
Issue 01
Received 13/12/2025
Accepted 05/01/2026
Published 09/01/2026
Publication Time 27 Days
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