Aircraft Joints: the Interaction between Corrosion Protection and Structural Performance

2011 ◽  
Vol 275 ◽  
pp. 101-104 ◽  
Author(s):  
Graham Clark ◽  
Ung Hing Tiong ◽  
Aditya Jaya
Keyword(s):  
Fatigue Life ◽  
Corrosion Protection ◽  
Protective Coatings ◽  
Fatigue Cracking ◽  
Lap Joints ◽  
Structural Performance ◽  
Large Strains ◽  
Strain Effect ◽  
Protection Measures ◽  
Coating Degradation

Aircraft joints feature prominently in aircraft structural degradation. Fatigue cracking and corrosion damage can reduce joint strength and degrade service life. Corrosion management can include use of paints and sealants and, increasingly, the application of Corrosion Inhibiting Compounds (CICs) which retard corrosion, by penetrating into crevices and cracks, and displacing water. A combination of coatings and CIC use can provide effective corrosion protection, but both interact - in different ways - with structural performance and overall system durability. This paper discusses the interaction between these two corrosion protection measures and fatigue performance of joints. The first issue relates to a reduction in the fatigue life of mechanically-fastened joints after application of CICs (or other lubricants) The lubricating properties of the CICs reduce the friction at the faying surface, which may change the load transfer characteristics of the joint. The paper discusses results from a test program assessing the fatigue life and failure mode of riveted lap joints; the results show a marked reduction in fatigue life for joints containing CICs, and the paper discusses the changes which may be responsible for the reduction. The second issue discussed is the degradation of protective coatings in service. Joints are key locations for coating cracking and failure, since areas such as sheet ends and fastener heads, where displacements are concentrated, will produce concentrated strain in coatings. So far, however, the potential influence of aircraft loading on coating degradation prognostics has received little attention. The paper discusses the role of joint displacement in service as a factor contributing to early degradation of aircraft coatings, and argues that this local strain effect, and indeed structural loading history, needs to be considered in predicting and assessing rates of coating degradation. It describes initial analyses of displacements in aircraft joints, to identify the levels of coating strain and the roles and relative contributions of the various deflections in the joints. The results indicate the potential for very large strains in coatings.

Sustainable and environmentally friendly zinc coatings for protecting steel bridges in Europe

2021 ◽  
Author(s):  
M. C. van Leeuwen ◽  
P. M. Gangé ◽  
B. Duran ◽  
F. Prenger
Keyword(s):  
Corrosion Protection ◽  
Life Cycle Cost ◽  
Zinc Coating ◽  
Environmentally Friendly ◽  
Cost Effective ◽  
Steel Bridges ◽  
Metallic Zinc ◽  
Protection Measures ◽  
Paint Systems ◽  
Zinc Coatings

<p>Metallic zinc coatings are well established as cost-effective corrosion protection for steel bridges. The zinc coating acts first as barrier protection, isolating the base steel from corrosive elements, and secondly by cathodic protection, acting as a sacrificial anode to protect the steel should the coating be compromised. Bridge operators can be confronted by disproportional high maintenance costs for bridges in use as removal of (in)organic paint systems with hazardous and toxic compounds require expensive waste disposal and environmental protection measures. Metallic zinc coatings are recognized as environmentally friendly, sustainable, and low maintenance, providing the lowest life cycle cost corrosion protection. Various case studies with bridges protected with metallic zinc coatings in and outside Europe are illustrated.</p>

Riveted single lap joints Part 2: Fatigue life prediction

1997 ◽  
Vol 211 (2) ◽  
pp. 123-128 ◽  
Author(s):  
C-P Fung ◽  
J Smart
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Effective Stress ◽  
Fatigue Testing ◽  
Strain Range ◽  
Lap Joints ◽  
Total Strain Range ◽  
Single Lap Joints ◽  
Data Points ◽  
Fretting Damage

Fatigue lives of snap and countersunk riveted single lap joints with either one-row or two- rows of rivets have been predicted with fatigue laws using either local total strain range or effective stress obtained from finite element analyses and data obtained from fatigue testing of plates with holes. The finite element models of the joints were subjected to an alternating cyclic load; plasticity and nonlinear geometry are considered. The failures have also been metallurgically examined and gave evidence of fretting damage. It was found that all the data points lie within a narrow band using the strain-life law although the band is wider when using the effective stress-life law, but it is impossible to predict the fatigue life from one kind of specimen to another using the conventional stress-life law.

scholarly journals OBSERVATIONS ON FATIGUE CRACK GROWTH AND FATIGUE LIFE OF RIVETED LAP JOINTS

2012 ◽  
Vol 31 (3) ◽  
pp. 108
Author(s):  
Andrzej SKORUPA ◽  
Małgorzata SKORUPA ◽  
Tomasz MACHNIEWICZ ◽  
Andrzej KORBEL
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Lap Joints ◽  
Riveted Lap Joints

scholarly journals Review of Recent Developments in the Formulation of Graphene-Based Coatings for the Corrosion Protection of Metals and Alloys

2020 ◽  
Vol 1 (3) ◽  
pp. 296-327
Author(s):  
Bronach Healy ◽  
Tian Yu ◽  
Daniele da Silva Alves ◽  
Carmel B. Breslin
Keyword(s):  
Graphene Oxide ◽  
Corrosion Protection ◽  
Hexagonal Boron Nitride ◽  
Protective Coatings ◽  
Galvanic Corrosion ◽  
Metals And Alloys ◽  
Graphene Layers ◽  
Recent Developments ◽  
Double Hydroxides ◽  
Protection Of Metals

Corrosion is a naturally occurring phenomenon and there is continuous interest in the development of new and more protective coatings or films that can be employed to prevent or minimise corrosion. In this review the corrosion protection afforded by two-dimensional graphene is described and discussed. Following a short introduction to corrosion, the application of graphene in the formulation of coatings and films is introduced. Initially, reduced graphene oxide (rGO) and metallic like graphene layers are reviewed, highlighting the issues with galvanic corrosion. Then the more successful graphene oxide (GO), functionalised GO and polymer grafted GO-modified coatings are introduced, where the functionalisation and grafting are tailored to optimise dispersion of graphene fillers. This is followed by rGO coupled with zinc rich coatings or conducting polymers, GO combined with sol-gels, layered double hydroxides or metal organic frameworks as protective coatings, where again the dispersion of the graphene sheets becomes important in the design of protective coatings. The role of graphene in the photocathodic protection of metals and alloys is briefly introduced, while graphene-like emerging materials, such as hexagonal boron nitride, h-BN, and graphitic carbon nitride, g-C3N4, are then highlighted.

A Review of Optimising the Design of a New Coke Drum Skirt

2019 ◽  
Author(s):  
Alex Berry ◽  
Warren Brown ◽  
Antonio Seijas ◽  
Sarah Cook
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Literature Review ◽  
Thermal Stresses ◽  
Fatigue Cracking ◽  
Element Analysis ◽  
Long Life ◽  
Welded Connection

Abstract Coke drums are subjected to severe thermal cycling with the skirt to shell connection weld being vulnerable to fatigue cracking. It is essential this connection is well designed to ensure a long life before repairs are inevitably required. Much has been written on coke drum skirt design with the aim of reducing the thermal stresses and strains encountered at the skirt connection weld, some designs have removed the weld completely allowing the drum to sit in an “egg-in-cup” arrangement. This paper includes a short literature review discussing Coke drum skirt designs and explains skirt behaviour during the drum cycle that results in eventual skirt cracking. A case study is reviewed in detail for a new pair of coke drums, where the predicted fatigue life of the chosen welded connection is assessed using axisymmetric, quarter symmetry and half symmetry finite element analysis supported by thermocouple data. The optimised design focuses on a conventional tangential design where the effects of the essential variables such as skirt thickness, skirt connection location, skirt-to head-gap and slot design (length, location & spacing) have been modelled and optimised to obtain a skirt design that produces the longest fatigue life for the intended duty cycle. Coke drum skirts must be installed onto the shell to exacting tolerances during manufacture to ensure concentricity and minimal gap between the skirt and shell. A brief overview of how this is achieved will be presented.

Laboratory Comparison of Permanent Deformation and Fatigue Behavior of Neat, Polymer, and Rubber-Asphalt Binders

2019 ◽  
Vol 2673 (4) ◽  
pp. 524-532
Author(s):  
Felipe F. Camargo ◽  
Kamilla Vasconcelos ◽  
Liedi L. Bernucci
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Fatigue Behavior ◽  
Permanent Deformation ◽  
Asphalt Binder ◽  
Fatigue Cracking ◽  
Fatigue Life Prediction ◽  
Polymer Modification ◽  
Neat Polymer ◽  
Percentage Recovery

Fatigue cracking and rutting are among the major types of distresses to be considered in flexible pavement design. In this context, the choice of the asphalt binder plays a major role in both the fatigue behavior and permanent deformation resistance of the asphalt mixture. This study was conducted to assess the permanent deformation and fatigue behavior of a field-blended rubber-asphalt (CRMA) and compare the results with typical binders used in Brazil. The neat binder used for modification was also employed as a control and as a base for polymer modification (SBSA). The binders were evaluated using the multiple stress creep and recovery (MSCR) for permanent deformation behavior, and the time sweep (TST) and linear amplitude sweep (LAS) tests for fatigue behavior. Modification of the neat binder resulted in an increase in percentage recovery in the MSCR, whereas the percentage recovery for CRMA was the highest among the three binders at any given temperature. The non-recoverable creep compliance for the CRMA was lower than that exhibited by the neat and SBSA binders for both stress levels for the range of temperatures tested. Binder modification resulted in an improved fatigue behavior compared with the neat binder according to the TST and LAS, whereas rubber modification resulted in the best fatigue behavior. Fatigue life prediction by TST was consistently higher than fatigue life prediction in the LAS test, probably because different criteria were used for determining failure in each test (ranking of the binders remained constant regardless of the criteria used).

Predicting the Fatigue Life of Long Dents in Petroleum Pipelines

2002 ◽  
Author(s):  
Adam J. Rinehart ◽  
Peter B. Keating
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Contact Region ◽  
Laboratory Data ◽  
Prediction Method ◽  
Fatigue Cracking ◽  
Local Stress ◽  
Fatigue Damage Accumulation ◽  
Bending Stresses ◽  
Life Predictions

A full scale experimental study has demonstrated that long, unrestrained pipeline dents typically experience fatigue cracking in the dent contact region and have significantly shorter fatigue lives compared to other dent types studied. Furthermore, these dents often fully reround under normal pipeline operating pressures, making them difficult to reliably detect and assess using existing depth-based approaches. Several conditions unique to the dent contact region accelerate fatigue damage accumulation and are considered in a case-specific long dent fatigue life prediction method. First, the contact region develops significant bending stresses that contribute to a higher rate of fatigue crack growth. Second, history dependent, thru-thickness residual bending stresses that may have a significant influence on fatigue behavior are present in the contact region as a result of plastic deformation associated with dent formation and subsequent rebounding. A method for predicting the fatigue life of long dents that accounts for these factors is presented here and is used to analyze specific cases for which laboratory data is available. Nonlinear finite element modelling of the dent life cycle, including the indentation and rebounding phases, is used to determine local stress range behaviors and residual stress distributions. The application of appropriate fracture mechanics based models of fatigue is discussed and demonstrated. Fatigue life predictions are made on a case by case basis for situations studied in the laboratory so that the validity and accuracy of the approach presented here may be studied.

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