scholarly journals Effect of residual stresses on the fatigue lifetime of railway axle

2017 ◽  
Vol 4 ◽  
pp. 42-47 ◽  
Author(s):  
Pavel Hutař ◽  
Pavel Pokorný ◽  
Jan Poduška ◽  
Rostislav Fajkoš ◽  
Luboš Náhlík
Keyword(s):  
Residual Stresses ◽  
Fatigue Lifetime ◽  
Railway Axle

Hydraulic Versus Swage Autofrettage and Implications of the Bauschinger Effect

2003 ◽  
Vol 125 (3) ◽  
pp. 309-314 ◽  
Author(s):  
A. P. Parker ◽  
G. P. O’Hara ◽  
J. H. Underwood
Keyword(s):  
Residual Stresses ◽  
Experimental Evidence ◽  
Hybrid Method ◽  
Bauschinger Effect ◽  
Pressure Level ◽  
Opening Angle ◽  
Fatigue Lifetime ◽  
Analysis Of Results

A hybrid method is presented which permits calculation of residual stresses in a swage autofrettaged tube including Bauschinger effect. The results are generally supported by three types of available experimental evidence by comparing “equivalent” swage and hydraulic autofrettage tubes having the same level of overstrain. Radial slitting of the swaged tube is predicted to show a greater opening angle than its hydraulic equivalent. Fatigue lifetime of the swaged tube is predicted to be significantly higher than the hydraulic case. Re-pressurization of the equivalent tubes is predicted to produce initial re-yielding at the same pressure in both cases. Analysis of results shows that permanent strains in the swaged tube are expected to appear at a pressure level below that for the hydraulic tube.

scholarly journals Methodology for estimation of residual stresses in hardened railway axle

2019 ◽  
Vol 23 ◽  
pp. 185-190
Author(s):  
Pavol Dlhý ◽  
Jan Poduška ◽  
Pavel Pokorný ◽  
Luboš Náhlík ◽  
Rostislav Fajkoš ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Railway Axle

Influence of Extension of Load Spectrum on Estimation of Residual Fatigue Lifetime of Railway Axle

2016 ◽  
Vol 258 ◽  
pp. 607-610
Author(s):  
Pavel Pokorný ◽  
Pavel Hutař ◽  
Luboš Náhlík
Keyword(s):  
Load Spectrum ◽  
Safe Operation ◽  
Fatigue Lifetime ◽  
Term Operation ◽  
Railway Axle ◽  
Tolerance Approach ◽  
Curved Track ◽  
Service Conditions ◽  
Residual Fatigue

Railway axles are subjected to cyclic amplitude loading which can lead to fatigue failure. For safe operation of railway axles a damage tolerance approach taking into account a possible defect in railway axle is often required. Because of different operation regimes of trains (fast/slow ride, ride on straight track, on curved track, over switches etc.) the load amplitude of axle is not constant. The variability of load is defined by a load spectrum, which is determined experimentally by measuring of load in service conditions. Even though the load spectrum is measured on several hundreds or thousands of operation kilometres, the railway axles are in operation much longer time (often tens of years). Therefore, some load amplitudes higher than ones measured in the test can occur during a long-term axle service. The contribution presented deals with the effect of extension of load spectrum by rare high load amplitudes, which can occur during long-term operation, on residual fatigue lifetime of railway axles.

scholarly journals Effect of Prestrain on the Fatigue Life of Superelastic Nitinol

2019 ◽  
Vol 28 (10) ◽  
pp. 5946-5958 ◽  
Author(s):  
Karthikeyan Senthilnathan ◽  
Ali Shamimi ◽  
Craig Bonsignore ◽  
Harshad Paranjape ◽  
Tom Duerig
Keyword(s):  
Residual Stresses ◽  
Duty Cycle ◽  
Fatigue Testing ◽  
Strain History ◽  
Fatigue Lifetime ◽  
History Of ◽  
Tension Testing ◽  
Beam Bending ◽  
Local Plastic Deformation ◽  
Delivery Catheter

Abstract Three types of fatigue testing are performed to elucidate the effects of prestraining superelastic Nitinol on its subsequent fatigue lifetime: rotary bending and tension–tension testing of wire, and beam bending using diamond-shaped specimens fabricated from tubing. Results show that local plastic deformation during prestraining induces residual stresses that have a pronounced effect on fatigue performance, enhancing performance when the fatigue duty cycle is of the same sense as the prestraining (tensile prestraining followed by a tensile duty cycle, for example), and decreasing fatigue lifetime when the sense of the duty cycle is opposite to that of prestraining. This provides an avenue to increasing fatigue lifetime, but more importantly it highlights the need to fully understand the nature of the duty cycle: for example, prestraining a stent by crimping it into a delivery catheter induces favorable residual stresses with respect to subsequent pulsatile fatigue, but might accelerate fracture in other modes, such as axial or crush fatigue. Caution is also advised when trying to apply data from “constant life diagrams” derived from the literature (Ref 1, 2 for example) that may not properly reflect the strain history of the device being analyzed.

A Re-Autofrettage Procedure for Mitigation of Bauschinger Effect in Thick Cylinders

2004 ◽  
Vol 126 (4) ◽  
pp. 451-454 ◽  
Author(s):  
Anthony P. Parker
Keyword(s):  
Yield Strength ◽  
Residual Stresses ◽  
Fracture Resistance ◽  
Hoop Stress ◽  
Bauschinger Effect ◽  
Pressure Vessels ◽  
Fatigue Lifetime ◽  
Cyclic Pressure ◽  
Manufacturing Procedure ◽  
Tube Geometry

A manufacturing procedure for enhancing residual stresses and thereby improving fatigue lifetime and fracture resistance of pressure vessels is proposed. The procedure involves initial autofrettage; one or more “heat soak plus autofrettage” sequences and an optional final heat soak. Stresses are calculated numerically for traditional, single autofrettage and compared with those created by the new procedure. The loss of bore compressive hoop stress due to Bauschinger effect is predicted to be significantly reduced. Associated fatigue lifetime calculations indicate that life may be improved by a factor of between 2 and 30, depending upon tube geometry and the ratio of cyclic pressure to yield strength. Repeated overload plus heat soak cycles may also be of benefit in other engineering design scenarios.

Is There an “Ultimate” Autofrettage Process?

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
M. Perl ◽  
J. Perry ◽  
T. Aharon ◽  
O. Kolka
Keyword(s):  
Residual Stresses ◽  
Carrying Capacity ◽  
Maximum Pressure ◽  
Numerical Comparison ◽  
Test Results ◽  
Fatigue Lifetime ◽  
Gun Barrel ◽  
Long Time ◽  
Experimental Findings ◽  
Hydraulic Processes

To increase the elastic-carrying capacity of a gun barrel, beneficial residual stresses are introduced to the barrel’s wall, commonly by the autofrettage process. There are two major autofrettage processes: the hydrostatic and the swage. While the theoretical solution for hydraulic autofrettage has been available and accessible for a long time, the available models for swage autofrettage have been quite limited. The issue of hydraulic versus swage autofrettage was intensively investigated pointing to the clear advantages of swage autofrettage in both the level of the residual stresses created and the total fatigue lifetime obtained. Nevertheless, it is generally accepted that overstraining a barrel to the same level of autofrettage by either the swage or the hydraulic processes produces the same safe maximum pressure (SMP) for firing. In the present analysis, the recently developed 3D code, which finally enables a realistic simulation of both swage and hydraulic autofrettage, is validated against experimental findings for several gun barrels. All the numerical results are found in excellent agreement with the test results in terms of the permanent bore enlargement (PBE) and the safe maximum pressure for these barrels. In order to compare the two autofrettage processes, the code is applied to two hypothetic 120 mm gun barrels simulating both swage and hydraulic autofrettage. The detailed numerical comparison between the two different autofrettage processes points to the fact that the swage autofrettage process is superior to the hydraulic autofrettage process. These results are very encouraging and call for continuing the pursuit of finding an “ultimate” autofrettage process that will yield the “optimal gun barrel.”

scholarly journals Corrosion fatigue lifetime assessment of high-speed railway axle EA4T steel with artificial scratch

2021 ◽  
Vol 245 ◽  
pp. 107588 ◽  
Author(s):  
Yanan Hu ◽  
Shengchuan Wu ◽  
Philip J. Withers ◽  
Huatang Cao ◽  
Pei Chen ◽  
...  
Keyword(s):  
Corrosion Fatigue ◽  
High Speed ◽  
Fatigue Lifetime ◽  
High Speed Railway ◽  
Railway Axle

Influence of Different Crack Propagation Rate Descriptions on the Residual Fatigue Lifetime of Railway Axles

2014 ◽  
Vol 627 ◽  
pp. 469-472 ◽  
Author(s):  
Pavel Pokorný ◽  
Luboš Náhlík ◽  
Pavel Hutař
Keyword(s):  
Crack Propagation ◽  
Crack Propagation Rate ◽  
Threshold Value ◽  
Propagation Rate ◽  
Accurate Estimation ◽  
Fatigue Crack Propagation Rate ◽  
Lifetime Estimation ◽  
Fatigue Lifetime ◽  
Railway Axle ◽  
Residual Fatigue

The paper deals with an estimation of the residual fatigue lifetime of the railway axles. The railway axles can include some cracks either from manufacturing process or from previous loading operation. Because of cyclic loading of the railway axles there is a risk of fatigue failure of the railway axles with unacceptable consequences. Based on this fact, for conservative establishment of the residual fatigue lifetime of the railway axle is necessary to consider an existing crack in the railway axle during design process. The fatigue lifetime estimation of railway axles is very sensitive to used crack propagation rate description (e.g.v-Kcurve). Typical bending of this curve (knee) can be found in the vicinity of the threshold value in fatigue crack propagation rate dependence (typicallyv-Kcurve expressed in log-log coordinates). For accurate estimation of residual fatigue lifetime of the railway axle is necessary to use approximation ofv-Kcurve that takes into account existence of the knee close to the threshold value of the stress intensity factor. The paper shows important differences between different crack propagation rate descriptions on the residual fatigue lifetime estimation of the railway axles. Results obtained can be used for safer design and operation of the railway axles.

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