Impact of Prognosis on Asset Life Extension and Readiness

2003 ◽  
Author(s):  
Yevgeny Macheret ◽  
Leo Christodoulou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Crack Detection ◽  
Crack Size ◽  
Probability Of Detection ◽  
Life Extension ◽  
Growth Data ◽  
Damage State ◽  
The Impact

Fatigue response of structural components is determined by environmental conditions, material microstructure, and loading history. Variation of these factors results in significant scatter in fatigue-crack growth rates and component life. In this paper, the impact of prognosis capability on asset life extension and readiness is evaluated. Fatigue-crack growth data on aluminum samples under controlled spectrum loading are used to describe the statistics of the crack-size distribution. Several sensors with different probability of detection (POD) characteristics are considered for detecting cracks of critical size, and the effect of the POD on the component life extension is evaluated. Although the crack-detection capability leads to the asset life extension, it is not sufficient to maintain required mission readiness. On the other hand, the prognosis capability, which is based on the knowledge of the component’s current damage state, damage evolution laws, and upcoming mission loading, allows required mission readiness to be maintained.

Effect of Hardness and Tensile Mean Stress on Fatigue Crack Growth in Beryllium Copper

1969 ◽  
Vol 11 (3) ◽  
pp. 343-349 ◽  
Author(s):  
L. P. Pook
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Residual Stresses ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Mean Stress ◽  
Growth Data ◽  
Beryllium Copper

Some fatigue crack growth data have been obtained for age-hardened beryllium copper. The fatigue crack growth rate was found to be very dependent on the hardness and tensile mean stress. This dependence is believed to be associated with the intense residual stresses surrounding Preston-Guinier zones.

Comparison of International Codes for a Fatigue Crack Growth Flaw Tolerance Sample Problem

2021 ◽  
Author(s):  
Gary L. Stevens
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Large Diameter ◽  
Sample Problem ◽  
Pressurized Water ◽  
Typical Application ◽  
Flaw Tolerance ◽  
Asme Code ◽  
The Impact

Abstract As part of the development of American Society of Mechanical Engineers Code Case N-809 [1], a series of sample calculations were performed to gain experience in using the Code Case methods and to determine the impact on a typical application. Specifically, the application of N-809 in a fatigue crack growth analysis was evaluated for a large diameter austenitic pipe in a pressurized water reactor coolant system main loop using the current analytical evaluation procedures in Appendix C of Section XI of the ASME Code [2]. The same example problem was previously used to evaluate the reference fatigue crack growth curves during the development of N-809, as well as to compare N-809 methods to similar methods adopted by the Japan Society of Mechanical Engineers. The previous example problem used to evaluate N-809 during its development was embellished and has been used to evaluate additional proposed ASME Code changes. For example, the Electric Power Research Institute investigated possible improvements to ASME Code, Section XI, Nonmandatory Appendix L [3], and the previous N-809 example problem formed the basis for flaw tolerance calculations to evaluate those proposed improvements [4]. In addition, the ASME Code Section XI, Working Group on Flaw Evaluation Reference Curves continues to evaluate additional research data and related improvements to N-809 and other fatigue crack growth rate methods. As a part of these Code investigations, EPRI performed calculations for the Appendix L flaw tolerance sample problem using three international codes and standards to evaluate fatigue crack growth (da/dN) curves for PWR environments: (1) ASME Code Case N-809, (2) JSME Code methods [5], and (3) the French RSE-M method [6]. The results of these comparative calculations are presented and discussed in this paper.

Near-Threshold Fatigue Crack Growth at 63Sn37Pb Solder Joints

2002 ◽  
Vol 124 (4) ◽  
pp. 385-390
Author(s):  
Ki-Ju Kang ◽  
Seon-Ho Choi ◽  
Tae-Sung Bae
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Lap Joint ◽  
Growth Data ◽  
Micro Structure ◽  
Crack Behavior ◽  
Temperature Aging ◽  
Near Threshold

Fatigue tests were performed using single lap-joint specimens to obtain near-threshold fatigue crack growth data of solder joint under mode-II load. Attention was focused on the effect of high temperature aging and microstructures separately from the intermetallics. As a result, it was shown that the long cast time yielded the intermetallics and microstructures of the solder invariable regardless of aging condition. The granular micro-structure of the air-cooled specimens was shown to be inferior to the laminated micro-structure of the furnace-cooled specimens. Also, transition of fatigue crack behavior with ΔJ and the procedure of fatigue crack propagation from the pre-crack tip were discussed.

Full Size Fatigue Crack-Growth Testing for Girth Welds

2004 ◽  
Author(s):  
Paulo Gioielli ◽  
Jaime Buitrago
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Production Quality ◽  
Small Scale ◽  
Loading Frequency ◽  
Growth Data ◽  
Girth Welds ◽  
Crack Growth Modeling ◽  
Fatigue Crack Growth Testing

Fatigue crack-growth modeling has a significant impact in establishing defect acceptance criteria for the inspection of fracture-critical, girth-welded components, such as risers and tendons. ExxonMobil has developed an experimental technique to generate crack-growth data, in actual welded tubulars, that account for the particular material properties, geometry, and residual stresses. The technique is fully compatible with conventional fracture mechanics models. It uses a series of pre-designed notches made around the welds on a production quality, full-scale specimen that is tested efficiently in a resonant fatigue setup. The crack development from notches is monitored during testing and evaluated post-mortem. Given its simplicity and high loading frequency, the technique provides growth data germane to the component at hand at a lower cost and faster than standard, small-scale tests.

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