Predicting Elastic and Plastic Stress Concentration Factor using Notch Strength Analysis

Abstract

Structural sizing is getting more sophisticated as weight and cost of any structure is important. Weight optimization is a key player in enhancing business revenues and reducing fuel consumption for a greener planet. Thus, millennial designers attempt to develop weight optimized structures, while meeting structural stiffness, strength and integrity, and safety requirements as specified by international certification agencies. This can be achieved by innovative analyses approaches, which predict realistic factor of safeties. As of today, structural designers rely on conservative hand analysis methods based on theoretical stress concentration factors to predict elastic/plastic stress concentrations around notches and cutouts for metallic structures. To optimize weight, such conservatisms are recommended to be avoided. However, calculation of experimental stress concentration factors is time consuming and very expensive. Finite element methods are used as an alternative. Even then, these methods are time consuming, require expensive licenses and validation against costly test results. This paper discusses about the hand analysis, using notch strength analysis approach to predict elastic as well as plastic stress concentrations and factor of safeties for structures subjected to tensile loads. The correlation between the results predicted by this approach and the finite element methods are discussed. Eventually, this paper guides the reader to calculate the elastic and plastic stress concentrations, nominal failure stresses and safety margins for various notched/cutout structures. This is lucrative from the point of view of optimization of weight, strength and robust structural integrity with minimal analysis time and expense.

Keywords: Weight, aircraft, cutout, notches, static, Neuber element, elastic stress, plastic stress, stress concentration factor, nominal failure stress and notch strength analysis

Cite this Article

Ravindra Kiragi, Sundaresan Poovalingam, Indradeep Bhadra. Predicting Elastic and Plastic Stress Concentration Factor using Notch Strength Analysis. Journal of Aerospace Engineering & Technology. 2018; 9(1): 1–14p.