A new methodology to predict damage tolerance based on compliance via global-local analysis

Alvaro M Delgado Neto,Gilberto Gomes,Thiago A A Oliveira

doi:10.3221/igf-esis.58.16

Alvaro M Delgado Neto, Gilberto Gomes + Show 1 more

Open Access

https://doi.org/10.3221/igf-esis.58.16

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Abstract

Over the years several design philosophies to fatigue developed in order to combine structural safety and economy to manufacturing and operating aircraft process. The safe-life approach, which consists of designing and manufacturing a safe aeronautical structure throughout its useful life, results in factors that oversize the structural elements, preventing the possibility of failure and evidently leading to high design costs. On the other hand, the approach based on the damage tolerance concept, in which it is assumed that the structure, even whether damaged, is able to withstand the actions for which it was designed until the detection of a crack due to fatigue or other defects during its operation. Here, we propose a new methodology to the damage tolerance problem in which two-dimensional global-local analysis at different levels of external requests will be made by means of compliance, aimed at finding a relationship between fatigue life and the Paris constant. Moreover, the BemCracker2D program for simulating two-dimensional crack growth is used. This methodology has been proved to be an efficient and applied alternative in the damage tolerance analysis.

Highlights

The National Transportation Safety Board [1] and Wanhill [2], have highlighted a number of documented studies to interpret the cause of airplane accidents due to fatigue processes such as those with the Comet and the Boeing 737-200
It is an approach that leads to high design costs and is not capable of guaranteeing security as to whether an unforeseen failure may occur during project life
Probabilistic studies on damage tolerance are based on fabrication components [20] and fatigue life dispersion from an initial defect distribution [21]

Summary

INTRODUCTION

The National Transportation Safety Board [1] and Wanhill [2], have highlighted a number of documented studies to interpret the cause of airplane accidents due to fatigue processes such as those with the Comet and the Boeing 737-200. The most extreme situations of foreseeable fatigue requirements arising during operation must be considered in the prototype tests This methodology results in factors that oversize the structural elements in order to prevent the possibility of failure. A new philosophy has been developed based on the concept of damage tolerance In this methodology, it is assumed that the structure, even when damaged, is able to withstand the actions for which it was designed until the detection of a fatigue crack or other defects during its operation. The concept of damage tolerance is applied to aircraft with composite structures [13,14,15,16] in multiple crack analysis [17] and in shape optimization projects [18,19]. A homemade software called BemCracker2D and its GUI BEMLAB2D version will be used for modeling and analysis of two-dimensional elastostatic problems involving cracks, which are based on the BEM and DBEM

LITERATURE REVIEW

MATERIAL AND METHODS