Residual Strength Prediction of Aluminum Panels with Multiple Site Damage Using Artificial Neural Networks.

Ala Hijazi,Sameer Al-Dahidi,Safwan Altarazi

doi:10.3390/ma13225216

Abstract

Multiple site damage (MSD) cracks are small fatigue cracks that may accumulate at the sides of highly loaded holes in aging aircraft structures. The presence of MSD cracks can drastically reduce the residual strength of fuselage panels. In this paper, artificial neural networks (ANN) modeling is used for predicting the residual strength of aluminum panels with MSD cracks. Experimental data that include 147 unique configurations of aluminum panels with MSD cracks are used. The experimental dataset includes three different aluminum alloys (2024-T3, 2524-T3, and 7075-T6), four different test panel configurations (unstiffened, stiffened, stiffened with a broken middle stiffener, and bolted lap-joints), many different panel widths and thicknesses, and the sizes of the lead and MSD cracks. The results presented in this paper demonstrate that a single ANN model can predict the residual strength for all materials and configurations with high accuracy. Specifically, the overall mean absolute error for the ANN model predictions is 3.82%. Furthermore, the ANN model residual strength predictions are compared to those obtained using the most accurate semi-analytical and computational approaches from the literature. The ANN model predictions are found to be at the same accuracy level of these approaches, and they even outperform the other approaches for many configurations.

Highlights

The concern about multiple site damage (MSD) typically arises for aging passenger and transport aircraft, especially since many of these aircraft are being used beyond their original design life
artificial neural networks (ANN) modeling is used for predicting the residual strength of aluminum panels with MSD cracks
Several methodologies ranging from simple engineering models to sophisticated computational approaches can be used for estimating the residual strength of panels with MSD cracks

Summary

Introduction

The concern about multiple site damage (MSD) typically arises for aging passenger and transport aircraft, especially since many of these aircraft are being used beyond their original design life. MSD cracks are small fatigue cracks that may accumulate at the sides of highly loaded holes (rivet holes in particular) in the aircraft’s fuselage or internal structure. These MSD cracks usually appear after an extended period of time due to the large number of loading cycles. According to LEFM, failure (or unstable crack extension) will occur when the value of the crack-tip Stress Intensity Factor (SIF) reaches a critical value This limiting value of the SIF is called the fracture toughness (KC ). The fracture toughness is a material property, but for thin sheets, it is slightly dependent on the thickness, grain orientation, and crack length Another theory that can be used for predicting the residual strength is the

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