Pre-crack fatigue life assessment of relevant aircraft materials using fractal analysis of eddy current test data

2013 ◽  
Author(s):  
Jürgen Schreiber ◽  
Ulana Cikalova ◽  
Susanne Hillmann ◽  
Norbert Meyendorf ◽  
Jochen Hoffmann
Keyword(s):  
Fatigue Life ◽  
Test Data ◽  
Eddy Current ◽  
Fractal Analysis ◽  
Life Assessment ◽  
Eddy Current Test ◽  
Current Test ◽  
Fatigue Life Assessment

Fatigue Life Assessment for NPS30 Steel Pipe

2012 ◽  
Author(s):  
Jorge Silva ◽  
Hossein Ghaednia ◽  
Sreekanta Das
Keyword(s):  
Fatigue Life ◽  
Test Data ◽  
Crack Depth ◽  
Research Work ◽  
Longitudinal Crack ◽  
Assessment Model ◽  
Life Assessment ◽  
Fatigue Life Assessment ◽  
Remaining Fatigue Life ◽  
Crack Defect

Pipeline is the common mode for transporting oil, gas, and various petroleum products. Aging and corrosive environment may lead to formation of various defects such as crack, dent, gouge, and corrosion. The performance evaluation of field pipelines with crack defect is important. Accurate assessment of crack depth and remaining fatigue life of pipelines with crack defect is vital for pipeline’s structural integrity, inspection interval, management, and maintenance. An experimental based research work was completed at the University of Windsor for developing a semi-empirical model for estimating the remaining fatigue life of oil and gas pipes when a longitudinal crack defect has formed. A statistical approach in conjunction with fracture mechanics was used to develop this model. Statistical analysis was undertaken on CT specimen data to develop this fatigue life assessment model. Finite element method was used for determining the stress intensity factor. The fatigue life assessment model was then validated using full-scale fatigue test data obtained from 762 mm (30 inch) diameter X65 pipe. This paper discusses the test specimens and test data obtained from this study. Development and validation of the fatigue life assessment model is also presented in this paper.

scholarly journals Unified Principal S–N Equation for Friction Stir Welding of 5083 and 6061 Aluminum Alloys

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiangwei Li ◽  
Ji Fang ◽  
Xiaoli Guan
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Friction Stir Welding ◽  
Test Data ◽  
Fatigue Tests ◽  
Life Assessment ◽  
Test Results ◽  
Friction Stir ◽  
Fatigue Life Assessment ◽  
Curve Equation

AbstractWith the popularization of friction stir welding (FSW), 5083-H321 and 6061-T6 aluminum alloy materials are widely used during the FSW process. In this study, the fatigue life of friction stir welding with two materials, i.e., 5083-H321 and 6061-T6 aluminum alloy, are studied. Fatigue tests were carried out on the base metal of these two materials as well as on the butt joints and overlapping FSW samples. The principle of the equivalent structural stress method is used to analyze the FSW test data of these two materials. The fatigue resistances of these two materials were compared and a unified principal S–N curve equation was fitted. Two key parameters of the unified principal S–N curve obtained by fitting, Cd is 4222.5, and h is 0.2693. A new method for an FSW fatigue life assessment was developed in this study and can be used to calculate the fatigue life of different welding forms with a single S–N curve. Two main fatigue tests of bending and tension were used to verify the unified principal S–N curve equation. The results show that the fatigue life calculated by the unified mean 50% master S–N curve parameters are the closest to the fatigue test results. The reliability, practicability, and generality of the master S–N curve fitting parameters were verified using the test data. The unified principal S–N curve acquired in this study can not only be used in aluminum alloy materials but can also be applied to other materials.

On the Derivation of Design S-N Curves Based on Limited Fatigue Test Data

2011 ◽  
Author(s):  
Inge Lotsberg ◽  
Knut O. Ronold
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Test Data ◽  
Large Scale ◽  
Life Assessment ◽  
Small Scale ◽  
Probability Of Survival ◽  
Fatigue Life Assessment ◽  
Prototype Test ◽  
Material Factor

Qualification of new characteristic S-N curves for fatigue life assessment of structures is considered to be a significant engineering challenge. First, representative fatigue test data for the actual structural connections have to be derived. Then these test data have to be transferred into characteristic S-N curves that represent a predefined probability of survival. Characteristic S-N curves are also often denoted design S-N curves as these curves are often used directly for fatigue life assessment of structures without application of a material factor. A few large scale tests can add significant confidence to a design S-N curve dependent on the type of structural detail to be designed. The reason for this is that a prototype test specimen can be fabricated in a similar way as the actual connection and it is similar in geometry, material characteristics, residual stress, and fabrication tolerances. In addition it can likely be subjected to a more relevant loading and boundary conditions as compared with that of small scale test specimens. When a limited number of test data are available, it is questioned how a characteristic S-N curve can be derived with a well defined probability of survival. The mentioned issues are further considered in this paper together with some recommendations on how to derive design S-N curves based on limited data.

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