scholarly journals Fatigue-Crack Growth-Rate Studies of Low-Alloy Pressure-Vessel Steels

1968 ◽  
Vol 90 (4) ◽  
pp. 648-655 ◽  
Author(s):  
D. F. Mowbray ◽  
W. R. Andrews ◽  
A. J. Brothers
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Crack Extension ◽  
Room Temperature ◽  
Plate Thickness ◽  
Pressure Vessel Steels ◽  
Class B ◽  
Crack Growth Rates

Fatigue-crack growth rates were determined at room temperature for ASTM A302-Class B and A 508-Class 2 steels in two characteristic plate and forging directions. Tests were performed under zero-to-tension cyclic loading using both through-crack and part-through-crack plate specimens. Crack growth rates in the through-crack specimens, though affected by plate or forging directions, were found to correlate well upon the hypothesis that the crack extension per cycle is proportional to a positive power of the range of alternating stress intensity factor. In addition, the rate of crack extension through the plate thickness of the surface-crack specimens was successfully correlated with data from through-crack specimens.

scholarly journals Optimizing Measurement of Fatigue Crack Growth Relationships for Cr-Mo Pressure Vessel Steels in Hydrogen Gas

2015 ◽  
Author(s):  
Brian Somerday ◽  
Paolo Bortot ◽  
John Felbaum
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Upper Bound ◽  
Growth Rates ◽  
Hybrid Approach ◽  
Hydrogen Gas ◽  
Design Life ◽  
Pressure Vessel Steels ◽  
Crack Growth Rates

The objective of this study was to explore an approach for measuring fatigue crack growth rates (da/dN) for Cr-Mo pressure vessel steels in high-pressure hydrogen gas over a broad cyclic stress intensity factor (ΔK) range while limiting test duration, which could serve as an alternative to the method prescribed in ASME BPVC VIII-3, Article KD-10. Fatigue crack growth rates were measured for SA-372 Grade J and 34CrMo4 steels in hydrogen gas as a function of ΔK, load-cycle frequency (f), and gas pressure. The da/dN vs. ΔK relationships measured for the Cr-Mo steels in hydrogen gas at 10 Hz indicate that capturing data at lower ΔK is valuable when these relationships serve as inputs into design-life analyses of hydrogen pressure vessels, since in this ΔK range crack growth rates in hydrogen gas approach rates in air. The da/dN vs. f data measured for the Cr-Mo steels in hydrogen gas at selected constant-ΔK levels demonstrate that crack growth rates at 10 Hz do not represent upper-bound behavior, since da/dN generally increases as f decreases. Consequently, although fatigue crack growth testing at 10 Hz can efficiently measure da/dN over a wide ΔK range, these da/dN vs. ΔK relationships at 10 Hz cannot be considered reliable inputs into design-life analyses. A possible hybrid approach to efficiently establishing the fatigue crack growth rate relationship in hydrogen gas without compromising data quality is to measure the da/dN vs. ΔK relationship at 10 Hz and then apply a correction based on the da/dN vs. f data. The reliability of such a hybrid approach depends on adequacy of the da/dN vs. f data, i.e., the data are measured at appropriate constant-ΔK levels and the data include upper-bound crack growth rates.

Effects of Tension-Compression Cycling on Fatigue Crack Growth in High Strength Alloys

1971 ◽  
Vol 93 (4) ◽  
pp. 893-896 ◽  
Author(s):  
T. W. Crooker
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Low Cycle Fatigue ◽  
Plate Thickness ◽  
High Strength ◽  
Simple Zero ◽  
Pressure Vessels ◽  
Crack Growth Rates

Crack growth by low-cycle fatigue is a potential failure mechanism for welded pressure vessels. Residual stresses remaining from fabrication or caused by localized plastic deformation incurred in shakedown can result in operating stress cycles approaching fully-reversed tension-compression. However, virtually all of the fatigue crack propagation data reported in the literature for structural alloys are generated under simple, zero-tension cycling, and their direct application to such problems is questionable. This paper presents the results of a study which shows that the compression portion of fully-reversed tension-compression cycling can contribute substantially to fatigue crack growth rates in plate thickness medium-to-high strength alloys. Data from several alloys show a 50 percent increase in fatigue crack growth rates due to tension-compression cycling. The implications of these findings and methods for applying the results of this study are discussed.

scholarly journals Advantageous Description of Short Fatigue Crack Growth Rates in Austenitic Stainless Steels with Distinct Properties

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 475
Author(s):  
Lukáš Trávníček ◽  
Ivo Kuběna ◽  
Veronika Mazánová ◽  
Tomáš Vojtek ◽  
Jaroslav Polák ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stainless Steels ◽  
Growth Rates ◽  
Large Scale ◽  
J Integral ◽  
Scale Yielding ◽  
Residual Fatigue ◽  
Crack Growth Rates

In this work two approaches to the description of short fatigue crack growth rate under large-scale yielding condition were comprehensively tested: (i) plastic component of the J-integral and (ii) Polák model of crack propagation. The ability to predict residual fatigue life of bodies with short initial cracks was studied for stainless steels Sanicro 25 and 304L. Despite their coarse microstructure and very different cyclic stress–strain response, the employed continuum mechanics models were found to give satisfactory results. Finite element modeling was used to determine the J-integrals and to simulate the evolution of crack front shapes, which corresponded to the real cracks observed on the fracture surfaces of the specimens. Residual fatigue lives estimated by these models were in good agreement with the number of cycles to failure of individual test specimens strained at various total strain amplitudes. Moreover, the crack growth rates of both investigated materials fell onto the same curve that was previously obtained for other steels with different properties. Such a “master curve” was achieved using the plastic part of J-integral and it has the potential of being an advantageous tool to model the fatigue crack propagation under large-scale yielding regime without a need of any additional experimental data.

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