Use of Miniature Specimens for Creep-Crack-Growth Testing

2000 ◽  
Vol 122 (3) ◽  
pp. 327-332 ◽  
Author(s):  
Carl E. Jaske ◽  
R. Viswanathan
Keyword(s):  
Crack Growth ◽  
Base Metal ◽  
Creep Crack Growth ◽  
Life Assessment ◽  
Crack Growth Behavior ◽  
Past Study ◽  
Constant Weight ◽  
Steel Weldment ◽  
Creep Crack ◽  
Miniature Specimens

Measuring the condition of high-temperature components after many years of service is an important part of remaining life assessment. Tests of miniature specimens have been utilized for this purpose because they require that only small samples be removed from the components, which minimizes or eliminates the need for costly repairs. Miniature-specimen techniques have been developed and validated for creep-rupture testing but not for creep-crack-growth testing. The objective of this research was to develop and validate a procedure for measuring creep-crack-growth behavior using miniature specimens. Based on a past study of Type 316 stainless steel, the single-edge-notch-tension (SENT) specimen configuration was chosen for the current work. SENT specimens were designed and prepared from both base metal and weldments of 2-1/4Cr-1Mo and 1-1/4Cr-1/2Mo steels. The base metal was ASME SA 387, Grade P22 and Grade P11 plate, respectively. The 2-1/4Cr-1Mo steel weldment was a seam-weld hot reheat steam pipe that had been in service for 106,000 hours, while the 1-1/4Cr-1/2Mo steel weldment was from a pipe that had been weld repaired after 244,200 hours of service. SENT specimens with test sections of 10×5×1.5 mm, 15×7.5×1.5 mm, and 20×10×1.5 mm were evaluated. Tests were conducted under constant weight loading or constant load-line displacement loading. Specimens were heated to 538°C using a standard laboratory furnace. Crack length was measured using the DC electric potential drop method. The test results were analyzed to produce creep-crack-growth rate da/dt as a function of the C* integral and compared with data from tests of half-size (1/2T-CT) and standard full-size (1T-CT) compact-tension specimens. For both base metals, the 1/2T-CT and three sizes of SENT specimens gave results that agreed well with those of 1T-CT specimens. For the 2-1/4Cr-1Mo steel weldments, SENT specimens produced good results. However, SENT specimens of the 1-1/4Cr-1/2Mo steel weldments exhibited cracking blunting and no creep crack growth. The reasons for the differences in behavior are discussed and guidance for application of miniature specimens to creep-crack-growth testing is presented. [S0094-4289(00)01403-1]

Geometry and Material Constraint Effects on Creep Crack Growth Behavior in Welded Joints

2017 ◽  
Vol 36 (2) ◽  
pp. 155-162 ◽  
Author(s):  
Y. Li ◽  
G. Z. Wang ◽  
F. Z. Xuan ◽  
S. T. Tu
Keyword(s):  
Crack Growth ◽  
Welded Joints ◽  
Creep Crack Growth ◽  
Stress Triaxiality ◽  
Life Assessment ◽  
Crack Growth Behavior ◽  
Creep Crack ◽  
Constraint Effects ◽  
Creep Life Assessment ◽  
Material Constraints

AbstractIn this work, the geometry and material constraint effects on creep crack growth (CCG) and behavior in welded joints were investigated. The CCG paths and rates of two kinds of specimen geometry (C(T) and M(T)) with initial cracks located at soft HAZ (heat-affected zone with lower creep strength) and different material mismatches were simulated. The effect of constraint on creep crack initiation (CCI) time was discussed. The results show that there exists interaction between geometry and material constraints in terms of their effects on CCG rate and CCI time of welded joints. Under the condition of low geometry constraint, the effect of material constraint on CCG rate and CCI time becomes more obvious. Higher material constraint can promote CCG due to the formation of higher stress triaxiality around crack tip. Higher geometry constraint can increase CCG rate and reduce CCI time of welded joints. Both geometry and material constraints should be considered in creep life assessment and design for high-temperature welded components.

Creep Crack Growth Behavior in Power Plant Boiler and Steam Pipe Steels

1988 ◽  
Vol 110 (2) ◽  
pp. 137-146 ◽  
Author(s):  
A. Saxena ◽  
J. Han ◽  
K. Banerji
Keyword(s):  
Power Plant ◽  
Crack Growth ◽  
Test Temperature ◽  
Creep Crack Growth ◽  
Growth Behavior ◽  
Life Assessment ◽  
Impurity Level ◽  
Crack Growth Behavior ◽  
Creep Crack ◽  
Service Degradation

One of the important ingredients in remaining creep crack growth life assessment of elevated temperature power plant components is the material creep crack growth rate data. This report summarizes the currently available data on Cr-Mo and Cr-Mo-V steels most commonly used in steam pipes and boilers. All data are correlated with the crack-tip parameter, Ct. The accompanying creep deformation data and tensile properties are also included. The influence of in-service degradation, test temperature and the welding parameters such as impurity level and post-weld heat treatment (PWHT) on the creep crack growth behavior were examined. It was shown that the influence of nominal material chemistry, service degradation and test temperature can be normalized into a single da/dt versus Ct trend for the base materials. It was also shown that the level of impurities and the PWHT can significantly influence the da/dt versus Ct behavior in weldments.

Creep Crack Growth Prediction of Very Long Term P91 Steel Using Extrapolated Short-Term Uniaxial Creep Data

2013 ◽  
Author(s):  
S. Maleki ◽  
A. Mehmanparast ◽  
K. M. Nikbin
Keyword(s):  
Crack Growth ◽  
Creep Crack Growth ◽  
Life Assessment ◽  
Short Term ◽  
Creep Crack ◽  
Uniaxial Creep ◽  
Laboratory Test Results ◽  
Area Of Concern ◽  
Term Creep

Practical time frames in newly developed steels, and technical and financial restrictions in test durations means that extrapolation of short-term laboratory test results to predict long-term high temperature service component failure is an area of concern when conducting a fitness for service or remaining life assessment. Recent literature presenting uniaxial creep and crack growth tests indicate that some materials show lower failure strains during longer term laboratory tests. The constraint based remaining failure ductility based NSW model crack prediction model has been shown to be capable of predicting upper/lower bounds of creep crack growth in a range of steels when data are obtained from relatively short to medium-term laboratory experiments (< 10,000 hours). This paper compares and analyses the response of the NSW model to predict long term creep crack propagation rates using a wide database of modified 9Cr material over s range of temperatures. The paper employs extrapolation methods of available uniaxial data to make viable conservative predictions of crack growth at high temperatures where at present no data is available.

scholarly journals Creep crack growth behavior of P91 steel weldments

2019 ◽  
Vol 23 (2 Part B) ◽  
pp. 1203-1209 ◽  
Author(s):  
Mohamed Swei ◽  
Aleksandar Sedmak ◽  
Blagoj Petrovski ◽  
Zorana Golubovic ◽  
Simon Sedmak ◽  
...  
Keyword(s):  
Crack Growth ◽  
Creep Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
P91 Steel ◽  
Creep Crack

Prediction of creep crack growth behavior in ASME P92 steel welded joint

2012 ◽  
Vol 61 ◽  
pp. 185-193 ◽  
Author(s):  
Lei Zhao ◽  
Hongyang Jing ◽  
Yongdian Han ◽  
Junjie Xiu ◽  
Lianyong Xu
Keyword(s):  
Crack Growth ◽  
Welded Joint ◽  
Creep Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
P92 Steel ◽  
Creep Crack
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