Life Prediction for Turbopropulsion Systems Under Dwell Fatigue Conditions

2012 ◽  
Author(s):  
Kwai S. Chan ◽  
Michael P. Enright ◽  
Jonathan P. Moody ◽  
Benjamin Hocking ◽  
Simeon H. K. Fitch
Keyword(s):  
Crack Growth ◽  
Life Prediction ◽  
Growth Models ◽  
Degradation Process ◽  
Time Dependent ◽  
Analysis Tool ◽  
Dwell Fatigue ◽  
Cycle Dependent ◽  
Time Dependent Crack Growth ◽  
Generic Time

The objective of this investigation was to develop an innovative methodology for life and reliability prediction of hot-section components in advanced turbopropulsion systems. A set of three generic time-dependent crack growth models was implemented and integrated into the DARWIN® probabilistic life-prediction code. Using the enhanced risk analysis tool and material constants calibrated to IN 718 data, the effect of time-dependent crack growth on the risk of fracture in turboengine component was demonstrated for a generic rotor design and a realistic mission profile. The results of this investigation confirmed that time-dependent crack growth and cycle-dependent crack growth in IN 718 can be treated by a simple summation of the crack increments over a mission. For the temperatures considered, time-dependent crack growth in IN 718 can be considered as a K-controlled environmentally-induced degradation process. Software implementation of the generic time-dependent crack growth models in DARWIN provides a pathway for potential evaluation of the effects of multiple damage modes on the risk of component fracture at high service temperatures.

Life Prediction for Turbopropulsion Systems Under Dwell Fatigue Conditions

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Kwai S. Chan ◽  
Michael P. Enright ◽  
Jonathan P. Moody ◽  
Benjamin Hocking ◽  
Simeon H. K. Fitch
Keyword(s):  
Crack Growth ◽  
Life Prediction ◽  
Growth Models ◽  
Degradation Process ◽  
Time Dependent ◽  
Analysis Tool ◽  
Dwell Fatigue ◽  
Cycle Dependent ◽  
Time Dependent Crack Growth ◽  
Generic Time

The objective of this investigation was to develop an innovative methodology for life and reliability prediction of hot-section components in advanced turbopropulsion systems. A set of three generic time-dependent crack growth models was implemented and integrated into the Darwin® probabilistic life-prediction code. Using the enhanced risk analysis tool and material constants calibrated to IN 718 data, the effect of time-dependent crack growth on the risk of fracture in a turboengine component was demonstrated for a generic rotor design and a realistic mission profile. The results of this investigation confirmed that time-dependent crack growth and cycle-dependent crack growth in IN 718 can be treated by a simple summation of the crack increments over a mission. For the temperatures considered, time-dependent crack growth in IN 718 can be considered as a K-controlled environmentally-induced degradation process. Software implementation of the generic time-dependent crack growth models in Darwin provides a pathway for potential evaluation of the effects of multiple damage modes on the risk of component fracture at high service temperatures.

An Overview of Time Dependent Crack Growth Models Used for ERW Seam Weld Analyses

2017 ◽  
Author(s):  
Richard Olson ◽  
Bruce Young ◽  
Jennifer O’Brian
Keyword(s):  
Crack Growth ◽  
Prediction Models ◽  
Growth Models ◽  
Time Dependent ◽  
Creep Model ◽  
Transportation Safety ◽  
Seam Weld ◽  
Integrity Management ◽  
Crack Growth Model ◽  
Time Dependent Crack Growth

In response to the National Transportation Safety Board (NTSB) Recommendation P-09-1, the Department of Transportation (DOT) Pipeline and Hazardous Material Safety Administration (PHMSA) initiated a comprehensive study to identify actions that could be implemented by pipeline operators to significantly reduce longitudinal seam failures in electric resistance weld (ERW) pipe. As part of the project, Task 4 in Phase II was designed to validate existing failure prediction models and, where gaps exist, refine or develop the models needed to assess and quantify defect severity for cold welds, hook cracks, and selective seam weld corrosion (SSWC) (the primary ERW/Flash Weld seam threats) for failure subject to loadings that develop both during hydrotests and in service. These models would then be used to develop new software to support integrity management of seam welds with enough flexibility to benefit from the experience gained during this project. The purpose of this paper is to review the time-dependent crack growth model used in the development of the PipeAssess PI™ pipeline integrity management software. The model will be discussed in the context of its underlying theory, validation, and application to a set of test cases. Both the stress-activated creep model and consequential tie to fatigue crack growth models are presented, which describe crack growth under hydrostatic holds and subsequent pressure cycles. Full-scale experiments are used to validate the models. The reports generated during the course of the project are publically available and are located at the PHMSA website: HTTP://PRIMIS.PHMSA.DOT.GOV/MATRIX/PRJHOME.RDM?PRJ=390.

Contributions of Time Dependent and Cyclic Crack Growth to the Crack Growth Behavior of Non Strain-Crystallizing Elastomers

2002 ◽  
Vol 75 (4) ◽  
pp. 643-656 ◽  
Author(s):  
J. J. C. Busfield ◽  
K. Tsunoda ◽  
C. K. L. Davies ◽  
A. G. Thomas
Keyword(s):  
Crack Growth ◽  
Growth Behavior ◽  
Time Dependent ◽  
Crack Growth Behavior ◽  
Wide Range ◽  
Dependent Component ◽  
Tearing Energy ◽  
Quasi Crystals ◽  
Crack Growth Rates ◽  
Time Dependent Crack Growth

Abstract Engineering components are observed to fail more rapidly under cyclic loading than under static loading. This reflects features of the underlying crack growth behavior. This behavior is characterized by the relation between the tearing energy, T, and the crack growth per cycle, dc/dn. The increment of crack growth during each cycle is shown here to result from the sum of time dependent and cyclic crack growth components. The time dependent component represents the crack growth behavior that would be present in a conventional constant T crack growth test. Under repeated stressing additional crack growth, termed the cyclic crack growth component, occurs. For a non-crystallizing elastomer, significant effects of frequency have been found on the cyclic crack growth behavior, reflecting the presence of this cyclic element of crack growth. The cyclic crack growth behavior over a wide range of frequencies was investigated for unfilled and swollen SBR materials. The time dependent crack growth component was calculated from constant T crack growth tests and the cyclic contribution derived from comparison with the observed cyclic growth. It is shown that decreasing the frequency or increasing the maximum tearing energy during a cycle results in the cyclic crack growth behavior being dominated by time dependent crack growth. Conversely at high frequency and at low tearing energy, cyclic crack growth is dominated by the cyclic crack growth component. A large effect of frequency on cyclic crack growth behavior was observed for highly swollen SBR. The cyclic crack growth behavior was dominated by the time dependent crack growth component over the entire range of tearing energy and/or crack growth rate. The origin of the cyclic component may be the formation/melting of quasi crystals at the crack tip, which is absent at fast crack growth rates in the unswollen SBR and is absent at all rates in the swollen SBR.

A Superposition Approach for Time-Dependent Fatigue Crack Growth

2012 ◽  
Author(s):  
Fashang Ma
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Time Dependent ◽  
Crack Growth Rates ◽  
Time Dependent Crack Growth

High temperature fatigue crack growth is a combination of fatigue, creep and environmental attack, which greatly enhance fatigue crack growth. In order to understand the damage mechanisms and develop a physically based crack growth model, systematic experimental research has been conducted under various loading conditions for different specimen geometries made from a high strength nickel alloy. Test results from this work showed that time-dependent fatigue crack growth rates differ significantly from those observed in conventional fatigue crack growth tests. Crack geometry and loading history significantly affect fatigue crack growth rate. These results suggest the need for a change in the K based superposition approach for time-dependent crack growth modeling. A phenomenological model has been developed to predict time-dependent crack growth under various loading histories and crack geometries. In this model an effective stress intensity factor is defined to account for the effects of constraint loss of fracture mechanics due to crack-tip plasticity, and the creep stress relaxation on stress intensity factor. It is found the model can accurately predict the dwell crack growth rates for different crack geometries under various loading conditions.

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