Effectiveness of Hydrostatic Testing for High Strength Pipe Material

2010 ◽  
Author(s):  
Kimberly Cameron ◽  
Alfred M. Pettinger
Keyword(s):  
Stress State ◽  
Crack Growth ◽  
High Strength ◽  
Pipe Material ◽  
Test Pressure ◽  
Safe Control ◽  
Low Probability ◽  
Lower Test ◽  
Crack Growth Rates ◽  
Pipe Materials

Pipeline systems are typically subjected to hydrostatic testing to help ensure pipeline integrity. It can be desirable to use the highest feasible test pressure to eliminate as many defects as possible. It is widely accepted that safe control of yielding can be achieved during hydrostatic testing and that the hydrostatic testing does not create a stress state that is less safe from the standpoint of pre-existing flaws. For a small percentage of cases, however, hydrostatic testing can produce flaws that were longer than the ones removed. In these few cases, the flaws can then fail at a lower test pressure than the original hydrostatic test. The low probability of these events, however, means that the effectiveness of the hydrostatic test is not significantly diminished in this case. Because crack growth from a pre-existing flaw is retarded in a plastically deformed material, it is also typically assumed that hydrostatic testing should not lead to accelerated crack growth. However, this does not take into account that the hydrostatic testing itself can cause some increment in crack growth and that for many higher strength pipe materials significantly large defects can survive hydrostatic testing. These longer defects can potentially grow after surviving a hydrostatic test. This paper discusses this difference in crack growth rates for cracks that have survived hydrostatic testing in different grade pipeline steels and the implications for hydrostatic testing.

Slow Crack Growth Resistance of Parent and Joint Materials From PE4710 Piping for Safety-Related Nuclear Power Plant Piping

2011 ◽  
Author(s):  
S. Kalyanam ◽  
D.-J. Shim ◽  
P. Krishnaswamy ◽  
Y. Hioe
Keyword(s):  
Crack Growth ◽  
Nuclear Power ◽  
Power Plants ◽  
Slow Crack Growth ◽  
Nuclear Industry ◽  
Pipe Material ◽  
Service Water ◽  
Hdpe Pipe ◽  
Pipe Materials ◽  
Hdpe Pipes

HDPE pipes are considered by the nuclear industry as a potential replacement option to currently employed metallic piping for service-water applications. The pipes operate under high temperatures and pressures. Hence HDPE pipes are being evaluated from perspective of design, operation, and service life requirements before routine installation in nuclear power plants. Various articles of the ASME Code Case N-755 consider the different aspects related to material performance, design, fabrication, and examination of HDPE materials. Amongst them, the material resistance (part of Article 2000) to the slow crack growth (SCG) from flaws/cracks present in HDPE pipe materials is an important concern. Experimental investigations have revealed that there is a marked difference (almost three orders less) in the time to failure when the notch/flaw is in the butt-fusion joint, as opposed to when the notch/flaw is located in the parent HDPE material. As part of ongoing studies, the material resistance to SCG was investigated earlier for unimodal materials. The current study investigated the SCG in parent and butt-fusion joint materials of bimodal HDPE (PE4710) pipe materials acquired from two different manufacturers. The various stages of the specimen deformation and failure during the creep test are characterized. Detailed photographs of the specimen side-surface were used to monitor the specimen damage accumulation and SCG. The SCG was tested using a large specimen (large creep frame) as well as using a smaller size specimen (PENT frame) and the results were compared. Further, the effect of polymer orientation or microstructure in the bimodal HDPE pipe on the SCG was studied using specimens with axial and circumferential notch orientations in the parent pipe material.

Environmentally assisted crack growth rates of high-strength aluminum alloys

JOM ◽  
2003 ◽  
Vol 55 (1) ◽  
pp. 49-52 ◽  
Author(s):  
Brain J. Connolly ◽  
Kristen L. Deffenbaugh ◽  
Angela L. Moran ◽  
Michelle G. Koul
Keyword(s):  
Aluminum Alloys ◽  
Crack Growth ◽  
Growth Rates ◽  
High Strength ◽  
High Strength Aluminum Alloys ◽  
Crack Growth Rates

The Effect of Cyclic Loading Frequency on Corrosion-Fatigue Crack Growth in High-Strength Riser Materials

2010 ◽  
Author(s):  
Stephen J. Hudak ◽  
James H. Feiger ◽  
Jason A. Patton
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Growth Rates ◽  
High Strength ◽  
Loading Frequency ◽  
Corrosion Fatigue Crack ◽  
Corrosion Fatigue Crack Growth ◽  
Crack Growth Rates

Corrosion-fatigue is a significant design consideration in deepwater floating production systems. Mechanical loading is accentuated due to the compliant nature of these structures, and sour service conditions can also occur either due to the nature of the crude production or due to seawater flooding of the reservoir to enhance production yield. New high-strength riser steels have recently been developed to meet the demands of deepwater development. The objective of this study was to characterize the corrosion-fatigue resistance of these materials in terms of crack growth rates as a function of applied stress intensity factor range (ΔK), as well as cyclic loading frequency. Experiments were performed on five different steels with yield strengths ranging from 848 to 1080 MPa. Two environments were considered: seawater with cathodic protection to simulate the environment outside of the riser, and a sour brine environment with low oxygen (< 10 ppb) to simulate the environment inside the riser. Not all steels were tested in the sour brine environment since not all were designed to operate in sour service. For both environments, higher strength steels were found to exhibit higher growth rates and lower saturation frequencies. Fatigue crack growth rates as a function of ΔK were also measured, and exhibited two different frequency responses. At high ΔK, the classical frequency response occurred: decreased frequency gave increased crack growth rates. At low ΔK, an inverse frequency effect was observed: deceased frequency gave decreased crack growth rates, as well as increased corrosion-fatigue crack growth thresholds. These differences are believed to be caused by different underlying processes controlling crack growth — specifically, material-environment reaction kinetics at high ΔK, and crack closure due to corrosion-product wedging at low ΔK. The practical significance of these results is discussed, including selection of frequencies for corrosion-fatigue crack growth testing, and applicability of results to structural integrity assessments.

Corrosion Fatigue Performance of Duplex 2507 for Riser Applications

2010 ◽  
Author(s):  
Feng Gui ◽  
Ramgopal Thodla ◽  
Ken Evans ◽  
Carlos Joia ◽  
Ilson Palmieri Baptista
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Growth Rates ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Performance ◽  
Partial Pressures ◽  
Crack Growth Rates

Corrosion fatigue performance is of interest for high strength steels in riser applications. This work investigated the corrosion fatigue performance of 2507 duplex stainless steel for use as riser materials in environments containing high partial pressures of carbon dioxide (50–100 bar) and limited quantity of hydrogen sulfide (0–0.12 bar). The procedures developed for controlling oxygen and Fe2+ contamination as well as methods to evaluate the concentration of H2S in the autoclave are presented. The crack growth rates and ΔKth for these materials in the pressure environments were discussed along with procedures to obtain ΔKth, when they were below 5ksi√in. Low crack growth rates in the range of 1×10−8 in/cycle were measured and the effect of sour environments was quantified. The fatigue crack growth rate in sour environments on 2507 duplex stainless steel is a 10x higher than in air.

Use of Precracked Specimens in Stress Corrosion Testing of High Strength Aluminum Alloys

CORROSION ◽  
1970 ◽  
Vol 26 (11) ◽  
pp. 487-503 ◽  
Author(s):  
M. V. HYATT
Keyword(s):  
Aluminum Alloys ◽  
Stress Corrosion ◽  
Crack Growth ◽  
Cantilever Beam ◽  
Growth Rates ◽  
Double Cantilever Beam ◽  
High Strength ◽  
Beam Specimen ◽  
High Strength Aluminum Alloys ◽  
Crack Growth Rates

Abstract Resistance to stress corrosion cracking of 10 high strength aluminum alloys in a variety of heat treatment conditions has been measured using precracked double cantilever beam (DCB) specimens. A new technique is described, and stress corrosion crack growth rates for the alloys tested are presented as a function of the plane-strain stress intensity KI. Crack growth rates for alloys in the T3 and T6 tempers showed both KI-independent and KI-dependent behavior, whereas alloys in the more resistant tempers showed only KI independent behavior over the KI range studied. Double cantilever beam specimen data correlated with established trends from smooth specimens tested by alternate immersion in 3.5% NaCl solution. From the crack growth rate data and the speed and simplicity with which it is obtained, it is concluded that the DCB specimen will be highly useful for (1) comparing and rating alloys, (2) developing new alloys and heat treatments, (3) comparing the effects of environments, (4) achieving or ensuring product uniformity, and (5) studying mechanisms of cracking.

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 Effects of Waveform and Cycle Period on Corrosion-Fatigue Crack Growth in Cathodically Protected High-Strength Steels

2014 ◽  
Vol 891-892 ◽  
pp. 211-216 ◽  
Author(s):  
Mark Knop ◽  
Nick Birbilis ◽  
Stan Lynch
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Growth Rates ◽  
High Strength Steels ◽  
High Strength ◽  
Corrosion Fatigue Crack ◽  
Corrosion Fatigue Crack Growth ◽  
Crack Growth Rates

The processes involved in corrosion fatigue in general are briefly outlined, followed by a brief review of recent studies on the effects of cycle frequency (rise times) and electrode potential on crack-growth rates at intermediate ΔK levels for cathodically protected high-strength steels. New studies concerning the effects of fall times and hold times at maximum and minimum loads on crack-growth rates (for Kmax values below the sustained-load SCC threshold) are presented and discussed. Fractographic observations and the data indicate that corrosion-fatigue crack-growth rates in aqueous environments depend on the concentration of hydrogen adsorbed at crack tips and at tips of nanovoids ahead of cracks. Potential-dependent electrochemical reaction rates, crack-tip strain rates, and hydrogen transport to nanovoids are therefore critical parameters. The observations are best explained by an adsorption-induced dislocation-emission (AIDE) mechanism of hydrogen embrittlement.

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