Fatigue Crack Growth Simulation in Railway Axles

2011 ◽  
Vol 488-489 ◽  
pp. 407-410
Author(s):  
Antonio De Iorio ◽  
Marzio Grasso ◽  
F. Penta ◽  
G. P. Pucillo
Keyword(s):  
Crack Growth ◽  
Damage Tolerance ◽  
Growth Models ◽  
Characteristic Parameters ◽  
Linear Elastic ◽  
Crack Growth Simulation ◽  
Propagation Law ◽  
Stationary Loading ◽  
Elastic Fracture ◽  
Two Parameters

In order to carry out the railway axle design according to the “Damage Tolerance” philosophy, reliable crack-growth models for these kind of components are necessary. Indeed, damage tolerance principles have received more and more attention from railway technical community, thanks to its ambitious task concerning the inspection intervals prevision of railway components subjected to non-stationary loading conditions. In this paper, a simple routine is exposed that is able to calculate the characteristic parameters of the Linear Elastic Fracture Mechanics (LEFM) for a generic cracked mechanical component. Such parameters are then used in a two parameters propagation law to estimate the necessary time for a crack to become critical.

Damage Tolerance Evaluation of Cracked Tubular Joints Subjected to Fatigue Loading

2010 ◽  
Vol 452-453 ◽  
pp. 653-656
Author(s):  
A. Rama Chandra Murthy ◽  
G.S. Palani ◽  
Nagesh R. Iyer
Keyword(s):  
Crack Growth ◽  
Life Prediction ◽  
Damage Tolerance ◽  
Fatigue Loading ◽  
Analytical Prediction ◽  
Remaining Life ◽  
Linear Elastic ◽  
Tubular Joints ◽  
Elastic Fracture ◽  
Experimental Values

This paper presents methodologies for damage tolerance evaluation of tubular T- and Y-joints by using linear elastic fracture mechanics (LEFM) principles. The damage tolerance evaluation is in terms of crack growth analysis and remaining life prediction of tubular joints. Stress intensity factor (SIF) for T-butt plates which can be used for computation of SIF for tubular joints has been evaluated as per BS: 7910. It is observed from the literature that the expressions given in BS: 7910 for computation of SIF have not been used for remaining life prediction of tubular joints. In this paper, these expressions have been used for analytical prediction of remaining life of tubular T- and Y- joints subjected to constant amplitude loading (CAL) and variable amplitude loading (VAL). Wheeler residual stress model has been employed to represent the retardation effects due to tensile overloads. It is observed that remaining life predicted for T- and Y-joints under CAL are found to be in good agreement with those of experimental values reported in the literature. In the case of VAL, it is observed that crack growth retardation increases with increase of OLR resulting in higher predicted remaining life. It has also been observed that the predicted remaining life is influenced by the number of OLs and occurrence of OL. Early occurrence of OL causes the higher remaining life compared to later OLs.

Aspects of Fatigue Crack Growth

1988 ◽  
Vol 202 (1) ◽  
pp. 19-29 ◽  
Author(s):  
M W Brown
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
High Cycle Fatigue ◽  
Fatigue Cracks ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Linear Elastic ◽  
Propagation Law ◽  
Elastic Fracture ◽  
Low Levels

The propagation of fatigue cracks under low levels of cyclic stress can be modelled by linear elastic fracture mechanics. Elastic-plastic parameters must be used for the higher stress amplitudes of conventional S–N curves in both the low and the high cycle fatigue regimes. The occurrence of different modes of crack growth is discussed and the use of a propagation law to predict component lifetime is demonstrated.

Handling Uncertainty in the Remnant Fatigue Life Assessment of Offshore Process Pipework

2016 ◽  
Author(s):  
Arvind Keprate ◽  
R. M. Chandima Ratnayake
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Life Assessment ◽  
Assessment Process ◽  
Linear Elastic ◽  
Fatigue Life Assessment ◽  
Process Piping ◽  
Growth Laws ◽  
Elastic Fracture ◽  
Offshore Industry

A typical procedure for a remnant fatigue life (RFL) assessment is stated in the BS-7910 standard. The aforementioned standard provides two different methodologies for estimating RFL; these are: the S-N curve approach and the crack growth laws (i.e. using Linear Elastic Fracture Mechanics (LEFM) principles) approach. Due to its higher accuracy, the latter approach is more commonly used for RFL assessment in the offshore industry. Nevertheless, accurate prediction of RFL using the deterministic LEFM approach (stated in BS-7910) is a challenging task, as RFL prediction is afflicted with a high number of uncertainties. Furthermore, BS-7910 does not provide any recommendation in regard to handling the uncertainty in the deterministic RFL assessment process. The most common way of dealing with the aforementioned uncertainty is to employ Probabilistic Crack Growth (PCG) models for estimating the RFL. This manuscript explains the procedure for addressing the uncertainty in the RFL assessment of process piping with the help of a numerical example. The numerically obtained RFL estimate is used to demonstrate a calculation of inspection interval.

The Growth Rate of Semi-Elliptic Fatigue Cracks in Thick-Walled Cylinders

1983 ◽  
Vol 22 ◽  
Author(s):  
W. A. Lees ◽  
P. S. J. Crofton
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Internal Pressure ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Low Alloy Steel ◽  
Linear Elastic ◽  
Fatigue Data ◽  
Elastic Fracture ◽  
Crack Growth Rates

ABSTRACTThe rate of growth of fatigue cracks originating at the bore and at the outside surface of thick-walled low alloy steel cylinders has been measured for cylinders subjected to fluctuating internal pressure.Analysis of the results using linear elastic fracture mechanics relationships shows that crack growth rates found in air adequately predict the behaviour of cracks growing from the outside surface of a cylinder.Fatigue cracks growing from the bore of a cylinder subjected to fluctuating internal pressure are found to advance at a consistently higher rate than that predicted from crack growth rate tests carried out in air.These findings are discussed in relation to the proposed adoption of existent strain-life fatigue data for pressure vessel design.

Evaluation of Crack Growth in Oxygenated High Temperature Water Using Full Size Pipe Tests

1986 ◽  
Vol 108 (1) ◽  
pp. 50-56
Author(s):  
R. M. Horn
Keyword(s):  
High Temperature ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Crack Depth ◽  
Ultrasonic Inspection ◽  
Linear Elastic Fracture Mechanics ◽  
Growth Data ◽  
Full Size ◽  
Linear Elastic ◽  
Elastic Fracture

Full Size pipe tests have been conducted as part of EPRI research programs at the General Electric Company to verify IGSCC crack growth predictions made using a linear elastic fracture mechanics model. The tests on 10.16 cm (4″ pipes) were performed in oxygenated, high temperature, high purity water. The pipes were produced through standard manufacturing procedures which in turn led to characteristic field piping sensitization levels in the heat affected zones (HAZ) and characteristic through wall weld residual stresses. The tests were conducted at stresses equal to or below the yield strength under constant load with limited cycling. Ultrasonic inspection and metallography were used to characterize crack depth after several test phases and used to verify model predictions. Significant cracks were detected and radial and circumferential growth were documented. These test results support the predictions made using linear elastic fracture mechanics modeling, and are discussed in terms of crack growth data developed in CT specimens in the laboratory. The stress level and oxygen level are shown to influence the crack growth rates. Rates of circumferential crack growth are also evaluated. The paper discusses the results in the context of other stress corrosion evaluations as well.

Fatigue Analysis of Nuclear Welded Structures Based on Structural Stress and Elasto-Plastic Fracture Mechanics Approach

2005 ◽  
Vol 297-300 ◽  
pp. 774-780
Author(s):  
Jong Sung Kim ◽  
Tae Eun Jin
Keyword(s):  
Fracture Mechanics ◽  
Fatigue Test ◽  
Growth Models ◽  
Fatigue Analysis ◽  
Thickness Variation ◽  
Structural Stress ◽  
Test Results ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Stress Concentration Factors

In the paper, the validity of the modified mesh-insensitive SS (structural stress) procedure to apply to the welded joints with local thickness variation is identified via the comparison of SCFs (stress concentration factors) calculated for various FE (finite element) models. FCI (fatigue crac kinitiation) cycles are determined by using the SS/EPFM (elasto-plastic fracture mechanics) approach and the various fatigue crack growth models. Fatigue test is performed to identify the validity of the fatigue analysis results. Finally, as a result of comparison among test and various analysis results, it is found that the SS/FM (fracture mechanics) approach agrees well with the fatigue test results over all cycle regions and the SS/EPFM approach is more reliable than the SS/LEFM (linear elastic fracture mechanics) approach.

A Practical Approach to Implementing Linear Elastic Fracture Mechanics in Gas Turbine Rotor Disk Analyses

2015 ◽  
Author(s):  
Scott Keller
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Gas Turbine ◽  
Crack Growth ◽  
Turbine Rotor ◽  
Linear Elastic Fracture Mechanics ◽  
Linear Elastic ◽  
Rotor Disk ◽  
Elastic Fracture ◽  
Growth Analyses

The failure of vital components is not uncommon in the gas turbine industry. In the event excessive degradation occurs within a component, e.g. extensive cracking in a turbine blade or vane, solutions exist to either repair or replace defective parts. Such parts are readily accessible and mostly exchangeable in the field, limiting the amount of outage time and assessment required for defective parts. When more critical components exhibit extreme wear or cracking, e.g. a crack in a rotor disk, repairs typically necessitate a complete rotor destack and refurbishment or have the potential to require the replacement of individual disks. In extreme cases, defects found in rotor disks can be known to retire an entire compressor or turbine rotor. The OEM solution of replacing disks puts a substantial cost on the customer, thus providing an incentive for characterization and advanced analyses to determine the residual life in critical rotating components. Considered an advanced analysis, linear elastic fracture mechanics (LEFM) provides the theory and fundamental structure to conduct crack growth analyses in components that exhibit nominally elastic behavior. Successful implementation of LEFM requires extensive characterization of the material, engine operating boundary conditions, and high fidelity finite element models. Upon the detection of a flaw, whether an internal or external indication, the results from finite element analyses can be used to derive the crack tip stress field and subsequent crack tip driving parameters. These parameters are then utilized in a comprehensive crack propagation model, calibrated to temperature- and load-dependent material data, to determine the number of cycles to unstable propagation. As a result, the remaining life of a component with a given indication is readily obtained, enabling our engineering team to provide a thorough life assessment of critical rotating components. An overview of the linear elastic fracture mechanics crack growth analyses conducted is presented, with a special emphasis on compressor and turbine disks.

Lifetime Analysis of Fusion Reactor First Wall Components

1983 ◽  
Vol 105 (2) ◽  
pp. 144-152 ◽  
Author(s):  
R. D. Watson ◽  
R. R. Peterson ◽  
W. G. Wolfer
Keyword(s):  
Crack Growth ◽  
Creep Crack Growth ◽  
Heat Fluxes ◽  
First Wall ◽  
Surface Heat Fluxes ◽  
Linear Elastic ◽  
R Ratio ◽  
Lifetime Analysis ◽  
Elastic Fracture ◽  
Effects Of Temperature

Linear elastic fracture mechanics is used to predict the growth of a semi-elliptical surface flaw through a thin-walled actively cooled 316 stainless steel first wall in a tokamak power reactor, which is subjected to pulsed surface heat fluxes, 14 MeV neutron irradiation and sputtering from particle bombardment. The results from an inelastic stress analysis, which includes thermal creep, irradiation creep, swelling, and wall thinning, are coupled to the crack growth calculations. The effects of temperature, R-ratio, threshold ΔK, neutron-induced embrittlement, creep crack growth and two-dimensional flaw shape changes are included. Predictions for a cylindrical blanket module with hemispherical first wall end cap indicate that severe reductions in lifetime can occur when radiation damage effects are included and demonstrate the need for high fluence data on da/dN and KIc.

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