Handbook of Materials Failure Analysis with Case Studies from the Aerospace and Automotive Industries

Abdel Salam Hamdy Makhlouf, Mahmood Aliofkhazraei

• Publisher: Butterworth-Heinemann
• Year: 2015
• ISBN:
  9780128011775
• Topic: Technology & Engineering
• Subtopic: Aeronautic & Astronautic Engineering
• Index: Technology & Engineering

Handbook of Materials Failure Analysis: With Case Studies from the Aerospace and Automotive Industries provides a thorough understanding of the reasons materials fail in certain situations, covering important scenarios, including material defects, mechanical failure as a result of improper design, corrosion, surface fracture, and other environmental causes.

The book begins with a general overview of materials failure analysis and its importance, and then logically proceeds from a discussion of the failure analysis process, types of failure analysis, and specific tools and techniques, to chapters on analysis of materials failure from various causes. Later chapters feature a selection of newer examples of failure analysis cases in such strategic industrial sectors as aerospace, oil & gas, and chemicals.

• Covers the most common types of materials failure, analysis, and possible solutions
• Provides the most up-to-date and balanced coverage of failure analysis, combining foundational knowledge, current research on the latest developments, and innovations in the field
• Ideal accompaniment for those interested in materials forensic investigation, failure of materials, static failure analysis, dynamic failure analysis, fatigue life prediction, rotorcraft, failure prediction, fatigue crack propagation, bevel pinion failure, gasketless flange, thermal barrier coatings
• Presents compelling new case studies from key industries to demonstrate concepts
• Highlights the role of site conditions, operating conditions at the time of failure, history of equipment and its operation, corrosion product sampling, metallurgical and electrochemical factors, and morphology of failure

Part 1

Failure Analysis in Aircraft and Aerospace Structures

Chapter 1

Strategies for static failure analysis on aerospace structures

Javier S. Millán; Iñaki Armendáriz; Juan García-Martínez; Roberto González ^* Materials and Structures Department, Instituto Nacional de Técnica Aeroespacial (INTA), Torrejón de Ardoz, Madrid Spain

Abstract

Primary objective of the failure analysis of a structure is the prediction of damage onset and the determination of its causes. As damage onset does not mean the final failure of the structure, the failure analysis also comprises the subsequent damage growth analysis that occurs when the structure is loaded; this is called progressive failure analysis (PFA). Performing accurate predictions of damage onset and PFA allows optimizing the structural design and improving its reliability. In this chapter, several methodologies developed by Instituto Nacional de Técnica Aeroespacial (INTA), the Spanish research center for Aerospace, in order to achieve reliable finite element model simulation of damaged structures including PFA are presented. These include delamination growth in composites, debonding onset and growth, and crack growth in thin metallic structures. Besides accuracy, INTA focuses on developing computationally efficient techniques and correcting mesh size effects.

Keywords

Progressive failure analysis

Finite element model

Virtual crack closure technique

Cohesive zone

Crack tip opening angle

Chapter outline

1 Introduction 4

2 Delamination Growth in Composites 4

2.1 VCCT Fundamentals 5

2.2 Experimental Benchmark and FEM Simulation 7

2.3 FEMs Comparison 8

2.4 Delamination Growth Tool 9

2.5 Correlation Between FEM Simulations and Tests 9

2.6 Mesh Size Effects 10

2.7 Comparison of Mixed-Mode Failure Criteria 10

2.8 Conclusion and Further Work in Delamination Growth Analysis 10

3 Debonding Onset and Growth 12

3.1 DCB Coupon: Mode I Interlaminar Fracture Toughness Test 13

3.2 FE Modeling 13

3.3 CZ Fundamentals 14

3.4 Mesh Dependency 14

3.5 Experimental Results 16

3.6 Correlation FEM Simulation—Tests 17

3.7 Conclusion and Future Work in Debonding Analysis 20

4 Crack Growth in Metallic Structures 20

4.1 CTOA Criterion—Experimental Obtaining of CTOA_C 21

4.2 Crack Growth Tool 23

4.3 Benchmarks Description 23

4.4 FEM Modeling 24

4.5 Correlation Simulations—Tests 24

4.6 Crack Growth in Metallic Structures—Conclusion and Future Work 26

References 26

1 Introduction

Failure analysis comprises the prediction of damage onset on a structure when subjected to loads and environmental conditions. Damages may consist in permanent structural deformations (plastic strains for instance); local damages as cracks for instance, or in general any deterioration of the structure, or lack of functionality. It should be noted that damage onset does not mean the final or catastrophic failure of the structure. Failure analysis also comprises the subsequent progressive failure analysis (PFA) that occurs when the structure is loaded in static or fatigue environments.

In PFA, two features are commonly studied. The first is damage progression before it may reach a critical size producing the final failure. The second is the so-called residual strength, the remaining capability of the damaged structure to withstand loads. In the aircraft sector, it is common to refer the concept of damage tolerance, which means that a structure in presence of undetected damages, either produced by manufacturing defects, fatigue, ambient conditions, or accidental, is still able to withstand the loads produced during its service life. The fail-safe concept is employed and is defined as damage that must not lead to failure before it is detectable by means of inspections. Properly understanding of failure causes and PFA, allows the engineer improving and optimizing the structural design, additionally improving structural reliability.

Instituto Nacional de Técnica Aeroespacial (INTA) is currently involved in developing reliable simulation techniques for damaged structures including PFA. The methodologies are based in the finite element model (FEM) technique and have been applied to typical aerospace structures made in metallic or composite materials, monolithic or sandwich, etc. Some examples are shown below:

• Composite structures with interlaminar delaminations: prediction of delamination growth under static loads.

• Debonding analysis: prediction of debonding onset and growth under static loads.

• Crack growth in thin metallic structures (structures with high plasticity).

Besides accuracy, INTA focuses on developing efficient techniques from a computational point of view (reasonable computation and postprocessing time) as well as understanding and correcting the mesh size effects (FE results dependency on mesh size).

2 Delamination Growth in Composites

The general trend in modern aircraft structures is the progressive replacement of metallic materials with composites. Composites exhibit superior structural properties such as higher stress allowable, better behavior in fatigue and damage tolerance, less sensitivity to corrosion phenomena, etc. Both the new Airbus A350 and Boeing B787 each wit...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Preface
• Part 1: Failure Analysis in Aircraft and Aerospace Structures
• Part 2: Failure Analysis in Automotive and Transportation Structures
• Index