Creep Crack Growth of P92 Welds

This paper represents creep properties and creep crack growth properties for P92 welds. The CCG tests were carried out using cross-welded compact tension (C (T) specimens at several temperatures. The crack front was located at HAZ region to simulate Type IV crack. Finite element analysis was conducted to simulate multiaxiality in welded joints and compare the experimental results. The constitutive behaviour for these materials is described by a power law creep model.

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Evaluation of Creep Crack Growth Rate of P92 Welds Using Fracture Mechanics Parameters

Journal of Pressure Vessel Technology ◽

10.1115/1.4001522 ◽

2010 ◽

Vol 132 (4) ◽

Cited By ~ 3

Author(s):

Masataka Yatomi ◽

Akio Fuji ◽

Masaaki Tabuchi ◽

Yasushi Hasegawa ◽

Ken-ichi I. Kobayashi ◽

...

Keyword(s):

Crack Growth ◽

Power Plants ◽

Thermal Power ◽

Creep Crack Growth ◽

Creep Model ◽

Element Analysis ◽

Creep Crack ◽

Fine Grained ◽

Type Iv ◽

Total Life

High Cr ferritic heat resisting steels have been widely used for boiler components in ultrasupercritical thermal power plants operated at about 600°C. In the welded joint of these steels, type-IV crack initates in the fine-grained heat affected zone during long-term use at high temperatures and their creep strength decreases. In this paper, creep properties and creep crack growth (CCG) properties of P92 welds are presented. The CCG tests are carried out using cross-welded compact tension C(T) specimens at several temperatures. The crack front was located within the fine-grained HAZ region to simulate type-IV cracking. Finite element analysis was conducted to simulate multiaxiality in welded joints and to compare experimental results. The constitutive behavior for these materials is described by a power-law creep model. C∗ and Q∗ parameters are used to evaluate CCG rate of P92 welds for comparison. C∗ parameters can characterize approximately 20% of the total life of CCG in P92 welds, and Q∗ parameters can characterize approximately 80% of the total life. Q∗ parameter is one of the useful parameters to predict CCG life in P92 welds.

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Modeling and Simulation of Creep Crack Growth in High Chromium Steels

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2014-28021 ◽

2014 ◽

Author(s):

Nicola Bonora ◽

Luca Esposito ◽

Simone Dichiaro ◽

Paolo Folgarait

Keyword(s):

Crack Growth ◽

Creep Crack Growth ◽

Compact Tension ◽

Chromium Steel ◽

Creep Model ◽

Model Parameters ◽

Approximate Methods ◽

High Chromium ◽

Creep Crack ◽

Wide Range

Safe and accurate methods to predict creep crack growth (CCG) are required in order to assess the reliability of power generation plants components. With advances in finite element (FE) methods, more complex models incorporating damage can be applied in the study of CCG where simple analytical solutions or approximate methods are no longer applicable. The possibility to accurately simulate CCG depends not only on the damage formulation but also on the creep model since stress relaxation, occurring in the near tip region, controls the resulting creep rate and, therefore, crack initiation and growth. In this perspective, primary and tertiary creep regimes, usually neglected in simplified creep models, plays a relevant role and need to be taken into account. In this paper, an advanced multiaxial creep model [1], which incorporates damage effects, has been used to predict CCG in P91 high chromium steel. The model parameters have been determined based on uniaxial and multiaxial (round notched bar) creep data over a wide range of stress and temperature. Successively, the creep crack growth in standard compact tension sample was predicted and compared with available experimental data.

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Comparison Between Crack Growth in Fracture Mechanics Specimens and Feature Component Tests Carried Out in a Low-Alloy Steel

Journal of Pressure Vessel Technology ◽

10.1115/1.556147 ◽

1999 ◽

Vol 122 (1) ◽

pp. 40-44 ◽

Cited By ~ 1

Author(s):

Kamran Nikbin

Keyword(s):

Fracture Mechanics ◽

Crack Growth ◽

Creep Crack Growth ◽

Compact Tension ◽

Growth Data ◽

Good Correspondence ◽

Creep Crack ◽

Growth Properties ◽

Circumferential Defects ◽

Testing Condition

In both power generation plants and the chemical industries, there is a need to assess the significance of defects which may exist in high-temperature equipment operating in the creep range. This paper examines the methods of analysis used in laboratory creep crack growth data and their relevance to crack growth data derived from feature component tests which best simulate actual components under controlled testing condition. The material examined was a 214 Cr 1 Mo steel in the new condition at 550 and 600°C. The creep crack growth properties were determined on compact tension specimens. The data were compared with representative crack growth data from feature test components. These consisted of cracked rings, thick-walled cylinders, and thin-walled tubes containing axial or circumferential defects under combinations of axial and internal pressure loading. Little influence of size or temperature on the measured crack propagation rates was observed when the results were plotted against the creep fracture mechanics parameter C*. This is shown to be because the relevant condition had little effect on the appropriate crack tip creep ductilities of the material. Good correspondence was observed between the compact tension and the feature component tests, suggesting the feasibility of the C* method for predicting short-term laboratory tests using different geometries. [S0094-9930(00)01001-5]

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Prediction of Creep Crack Growth for Modified 9Cr-1Mo at 600°C

Volume 3: Design and Analysis ◽

10.1115/pvp2012-78160 ◽

2012 ◽

Author(s):

Nak Hyun Kim ◽

Yun Jae Kim ◽

Woo Gon Kim ◽

Hyeong Yeon Lee

Keyword(s):

Prediction Model ◽

Crack Growth ◽

Damage Model ◽

Creep Crack Growth ◽

Creep Damage ◽

Compact Tension ◽

Compact Tension Specimen ◽

Element Analysis ◽

Creep Ductility ◽

Creep Crack

This paper introduce theoretical creep crack growth prediction model and provides experimental validation of the approach for simulating creep crack growth using finite element analysis method, recently proposed by the authors. The FE creep damage model is based on the creep ductility exhaustion concept, and incremental damage is defined by the ratio of incremental creep strain and multi-axial creep ductility. A simple linear damage summation rule is applied. When accumulated damage becomes unity, element stresses are reduced to zero to simulate progressive crack growth. For validation, simulated results are compared with experimental data for a compact tension specimen of modified 9Cr-1Mo at 600°C under various loading levels. The simulated results agree well with experimental C*-da/dt data. The test data are also compared with theoretical CCG prediction model.

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Estimation of Creep Crack Growth Properties Using Circumferential Notched Round Bar Specimen for 12CrWCoB Rotor Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.297-300.397 ◽

2005 ◽

Vol 297-300 ◽

pp. 397-402

Author(s):

Je Chang Ha ◽

Joon Hyun Lee ◽

Masaaki Tabuchi ◽

A.Toshimitsu Yokobori Jr.

Keyword(s):

Crack Growth ◽

Axial Stress ◽

Creep Crack Growth ◽

Turbine Rotor ◽

Rotor Steel ◽

Creep Ductility ◽

Crack Growth Behaviour ◽

Creep Crack ◽

Round Bar ◽

Growth Properties

Most heat resisting materials in structural components are used under multi-axial stress conditions and under such conditions ductile materials often exhibit brittle manner and low creep ductility at elevated temperature. Creep crack initiation and growth properties are also affected by multi-axial stress and it is important to evaluate these effects when laboratory data are applied to structural components. Creep crack growth tests using circumferential notched round bar specimens are a simple method to investigate multi-axial stress effects without using complicated test facilities. Creep crack growth tests have been performed using a 12CrWCoB turbine rotor steel. In order to investigate the effects of multi-axial stress on creep crack growth properties, the tests were conducted for various notch depths at 650°C. The circumferential notched round bar specimen showed brittle crack growth behaviour under multi-axial stress conditions. Creep crack growth rate was characterized in terms of the C* parameter. A 12CrWCoB turbine rotor steel has been tested using circumferential notched round bar specimens with different multi-axiality. Circumferential notched round bar specimens show increased brittle creep crack growth behaviour due to the multi-axial stress condition. Creep crack growth properties could be predicted by allowing for the decrease of creep ductility under multi-axial conditions.

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