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Research Papers: Materials and Fabrication

Measurement of Fatigue Crack Growth Relationships in Hydrogen Gas for Pressure Swing Adsorber Vessel Steels

[+] Author and Article Information
Brian P. Somerday

Sandia National Laboratories,
7011 East Ave.,
Livermore, CA 94550
e-mail: bpsomer@sandia.gov

Monica Barney

Chevron Energy Technology Company,
100 Chevron Way,
Richmond, CA 94801
e-mail: MBarney@chevron.com

The crack length data furnished by the unloading compliance method were corrected based on post-test optical measurements of the precrack and final crack lengths from the fracture surfaces. The difference between the crack lengths determined from unloading compliance and optical measurements were approximately 10% for the precrack and < 5% for the final crack length. A routine in the analysis software linearly corrected the crack lengths calculated from unloading compliance so that the initial and final crack lengths equaled the optically measured values.

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received January 4, 2014; final manuscript received August 18, 2014; published online December 4, 2014. Assoc. Editor: Marina Ruggles-Wrenn.

J. Pressure Vessel Technol 137(2), 021406 (Apr 01, 2015) (7 pages) Paper No: PVT-14-1001; doi: 10.1115/1.4028349 History: Received January 04, 2014; Revised August 18, 2014; Online December 04, 2014

Hydrogen-assisted fatigue crack growth rates (da/dN) were measured for SA516 Grade 70 steel as a function of stress-intensity factor range (ΔK) and load-cycle frequency to provide life-prediction data relevant to pressure swing adsorber (PSA) vessels. For ΔK values up to 18.5 MPa m1/2, the baseline da/dN versus ΔK relationship measured at 1 Hz in 2.8 MPa hydrogen gas represents an upper bound with respect to crack growth rates measured at lower frequency. However, at higher ΔK values, baseline da/dN data must be corrected to account for modestly higher crack growth rates at the lower frequencies relevant to PSA vessel operation.

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Figures

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Fig. 1

Optical image representing the rolling plane of SA516 Grade 70 steel plate (2% nital etch). The steel microstructure consists of equiaxed ferrite grains with pearlite bands oriented in the rolling direction.

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Fig. 2

Fatigue crack growth rate (da/dN) versus stress-intensity factor range (ΔK) relationships for SA516 Grade 70 steel in nominally 2.8 MPa hydrogen gas and ambient air

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Fig. 3

Scanning electron microscope (SEM) image of fracture surface from SA516 Grade 70 steel at the termination point of the fatigue precrack produced in air (ΔK = 8.0 MPa m1/2). Crack growth direction is from bottom to top.

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Fig. 4

SEM images of fracture surfaces from SA516 Grade 70 steel tested under constant load amplitude at 1 Hz in 2.8 MPa hydrogen gas: (a) intergranular crack growth at ΔK = 10.0 MPa m1/2, (b) transgranular crack growth at ΔK = 14.0 MPa m1/2, and (c) transgranular crack growth at ΔK = 36.5 MPa m1/2. Crack growth direction is from bottom to top.

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Fig. 5

Fatigue crack growth rates (da/dN) measured as a function of load-cycle frequency (f) at four different constant ΔK levels in 2.8 MPa hydrogen gas. These data points are superimposed on the baseline da/dN versus ΔK relationships measured under constant load amplitude at 1 Hz in nominally 2.8 MPa hydrogen gas (Fig. 2).

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Fig. 6

Normalized fatigue crack growth rate as a function of load-cycle frequency (f) at two different constant ΔK levels in 2.8 MPa hydrogen gas. The normalized quantity is the ratio of the crack growth rate at constant ΔK and the crack growth rate at the respective ΔK level from the baseline da/dN versus ΔK relationship. The lines are not curve fits but are merely intended to indicate trends.

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Fig. 7

Fatigue crack growth rate (da/dN) versus stress-intensity factor range (ΔK) relationships for A516 steel (7 MPa hydrogen gas and 1 Hz load-cycle frequency [10]) and another C–Mn–Si steel (3 MPa hydrogen gas and 0.001 Hz load-cycle frequency [5]). These data are compared to the da/dN versus ΔK relationships for SA516 steel (2.8 MPa hydrogen gas and 1 Hz load-cycle frequency) from Fig. 2.

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