Application of Notch Strain Techniques to Elastic-Plastic and Elastic-Plastic-Creep Behaviour of Complex Structures

Abstract

Notch strain techniques have been widely applied to simple notch components and geometries to predict both elastic -plastic and creep strains along with associated stresses. However, the real benefit of such methods ought to be in their application to more complex structures with stress concentration features such as notches under multi-axial stress states. Aero-engine casing structures are a typical example of such a complex component in which optimum design is critical for weight savings and appropriate stiffness behaviour but where notch features may lead to localized plastic strains and hence damage. This article examines the performance of a number of notch strain techniques for the prediction of the elastic -plastic and creep notch stress and strain responses of a complex aero-engine casing structure. In addition, a modelling methodology involving a combination of (a) linear elastic and limit load analyses of a simplified global model and (b) linear elastic analysis of detailed local models is developed to demonstrate how approximate notch predictions of elastic -plastic and elastic -plastic-creep notch stresses and strains in complex structures can be obtained without recourse to the more significant computational expense of global (fine mesh), non-linear (incremental), and time-dependent elastic -plastic -creep analyses.

A time‐dependent stress and strain estimation method for notched components of power‐law creep materials under combined primary and secondary loads

“…Subsequently, a procedure for multi‐axial notch principal stress and strains under creep based on the differential Neuber's method was raised 35 . Reasonable stress and strain predictions at local regions of aero‐engine casing structures under different load conditions were obtained 36 …”

“…35 Reasonable stress and strain predictions at local regions of aero-engine casing structures under different load conditions were obtained. 36 Another modified differential method is proposed by Nunez and Glinka, 37,38 considering the local strain energy density rate variation during the creeping stage. In their work, the constraint effect of the far field on the strain energy density of notch root was estimated, based on a series of theoretical formulas of the elastic stress distribution along the cross section with different notch geometries.…”