Random Spectrum Fatigue Crack Life Predictions With or Without Considering Load Interactions

2009 ◽  
pp. 115-115-18 ◽  
Author(s):  
JB Chang ◽  
M Szamossi ◽  
K-W Liu
Keyword(s):  
Fatigue Crack ◽  
Life Predictions

Effect of Pressure Loading on Integrity Management

2008 ◽  
Author(s):  
Sanjay Tiku ◽  
Aaron Dinovitzer ◽  
Scott Ironside
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Operating Pressure ◽  
Integrity Assessment ◽  
Pipeline Segment ◽  
Pressure Cycle ◽  
Integrity Management ◽  
Pump Compressor ◽  
Life Predictions

Integrity assessment or life predictions for in-service pipelines are sensitive to the assumptions they rely upon. One significant source of uncertainty is the pipeline operating pressure data often captured and archived using a Supervisory Control and Data Acquisition (SCADA) system. SCADA systems may be programmed to collect and archive data differently from one pipeline to another and the resulting pressure records can be significantly different on the basis of the sampling techniques, data processing and the distance from pump and compressor stations. This paper illustrates some of the issues involved in pressure load characterization and is based upon work sponsored by the Pipeline Research Council International (PRCI). A series of sensitivity studies using fatigue crack growth calculations have been carried out to evaluate several factors that can influence crack stability and growth predictions that are often employed in pipeline integrity planning and repair programs. The results presented will highlight the issues related to performing integrity management based upon pump/compressor discharge or suction SCADA data to characterize the potential severity of pressure fluctuation or peak pressure dependent defects, illustrate the differences in fatigue crack growth rates along a pipeline segment and demonstrate the complexity of pressure cycle severity characterization, based upon distance from discharge, elevation, hydraulic gradient, for different sites along the pipeline route.

scholarly journals Investigation of Fatigue Crack Growth in Full-Scale Railway Axles Subjected to Service Load Spectra: Experiments and Predictive Models

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1427
Author(s):  
Amir Pourheidar ◽  
Luca Patriarca ◽  
Stefano Beretta ◽  
Daniele Regazzi
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Full Scale ◽  
Experimental Results ◽  
Residual Lifetime ◽  
Crack Growth Behavior ◽  
Load Spectra ◽  
Life Predictions

In this paper, a series of experimental investigations was performed on full-scale railway axles to analyze the fatigue crack growth behavior of EA4T steel under load spectrum derived from real operating conditions. The experimental results were compared to life predictions carried out adopting two models: (i) the conventional Nasgro equation and (ii) the cyclic R-curve concept implemented in the Modified Nasgro equation for describing the crack growth behavior of an arbitrary crack length. The results show that the life predictions performed by means of the Modified Nasgro equation coincide well with the experimental results with an underestimation of the residual lifetime less than 32%, while the traditional Nasgro equation leads to significant overestimation (≈120%) of the residual lifetime for load spectra close to the in service scenario.

Two-Dimensional Surface Fatigue Crack Propagation and its Finite Element Simulation

2015 ◽  
Vol 725-726 ◽  
pp. 654-660
Author(s):  
Ruslan Guchinsky ◽  
Sergei Petinov
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Two Dimensional ◽  
Growth Step ◽  
Surface Fatigue ◽  
Element Simulation ◽  
Surface Fatigue Crack ◽  
Life Predictions

Fatigue crack growth rate at the plane stress is predicted by Paris equation, associating it with the stress intensity factor (SIF), generalized parameter of the elastic stress field near the crack tip. The finite element method allows modelling of the incremental crack growth in the plates, where the finite element grid should be re-meshed on each crack growth step fitting the first principal stress planes. However, the linear fracture mechanics format (LEFM) based evaluation of the two-dimensional fatigue cracks does not provide always the correct crack front assessment and appropriate life-predictions. It is shown that approach using the damage accumulation simulation and strain-life criterion may be promising in analysis of the two-dimensional cracks. Application of the approach is illustrated. The simulation results are in good agreement with the experimental data.

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