Fast Analytical Algorithm for Fatigue Crack Life Estimations of Integrally Stiffened Metallic Panels

Abstract

This work presents the enhancement of a pseudo-numerical tool for fatigue crack growth investigations on integrally stiffened metallic panels. The model is based on an analytical approach that demands compatibility of displacement between skin sheet and stiffener. Since the basis model was presented before, the focus of the present work is on the incorporation of residual stress effects in order to improve simulation results of welded panel configurations that are manufactured by laser beam welding or friction stir welding and exhibit a significant amount of residual stresses. The necessary input parameters for the developed residual stress module are determined from experimental residual stress field measurements. Simulation results using the presented approach are compared with results from finite element simulations on a two stringer panel which show the good accordance of the base model as well as the capability of the tool enhancements to account for the crack retarding effect caused by residual stresses.

Holistic Low-Effort Model for Damage Tolerance Analysis in Preliminary Design

“…All scenarios feature stiffened structures, as they are usual in transport aircraft. In this paper only differential stiffener designs are discussed, but this does not limit the applicability of the calculation method; indeed it could easily be extended to integrally stiffened designs [10][11][12]. One crucial characteristic of the three different scenarios is the very dissimilar type of load histories to be expected.…”

Residual Stress Effects in Stiffened Structures - An Alternative Approach

“…The paper presents a semi-numerical method for the determination of stress intensity factors, taking into account the residual stresses in such a way that the relaxation of the residual stresses during the crack propagation phase is covered. This approach is different from the one presented in [1]. In the model presented in [1], the residual stress distributions proposed in [2] and [3] have been used.…”

“…This approach is different from the one presented in [1]. In the model presented in [1], the residual stress distributions proposed in [2] and [3] have been used. The developed pseudo-numerical method enables fast estimations on the crack growth behavior of integrally stiffened metallic panels and is based on analytical, two-dimensional complex stress functions, originally developed for riveted structures by Swift [4] and Nishimura [5].…”

“…The developed pseudo-numerical method enables fast estimations on the crack growth behavior of integrally stiffened metallic panels and is based on analytical, two-dimensional complex stress functions, originally developed for riveted structures by Swift [4] and Nishimura [5]. The developed method merges the features of both approaches and adapts them to the characteristics of integrally stiffened structures and was already presented in detail by the authors [6].…”

“…Different from the approach in [1], the present model introduces a residual stress by means of a mismatch in the length between stiffener and basic plate which results in a remaining stress in both items, a tensional one in the stiffener and a compressive one in the plate. The resulting total stress at a location i under remote stress σ then consists of the following parts: the resulting stress of the remote stress and the stress introduced by an attachment force F j due to the mismatched stiffener at the location of the crack front.…”