Analysis of Creep Crack Initiation and Growth in Different Geometries for 316H and Carbon Manganese Steels

Davies, Catrin M.; Mueller, Falk; Nikbin, Kamran; O’Dowd, Noel P.; Webster, G. A.

doi:10.1520/jai13220

Cited by 35 publications

(20 citation statements)

References 11 publications

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“…15,16 For Cr-Mo-V steel with high yield stress, it has been shown by the previous work of authors 12 that at higher C* value corresponding to the turning point 3 in Fig. 2, the crack-tip plastic deformation occurred.…”

Section: Introductionmentioning

confidence: 77%

Effect of stress dependent creep ductility on creep crack growth behaviour of steels for wide range ofC*

Zhang

Wang

Xuan

et al. 2014

Materials at High Temperatures

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In this work, the effect of stress dependent creep ductility on the creep crack growth (CCG) behaviour of steels has been investigated by finite element simulations based on ductility exhaustion damage model. The relationship between the transition region of creep ductility and the transition behaviour of CCG rate on da/dt-C* curves has been examined and the CCG life assessments of components and CCG resistance of materials for a wide range of C* were discussed. The results show that with increasing the transition region size of creep ductility, the transition C* region size on da/dt-C* curves increases. With moving transition region position of creep ductility to high stress region (increasing transition stress levels), the transition C* region on the da/dt-C* curves also moves to high C* region. Decreasing transition stress levels and transition region sizes of creep ductility and increasing the lower shelf and upper shelf creep ductility values can improve the CCG resistance of materials. If the extrapolation CCG rate data from the high C* region or from the transition C* region are used in life assessments of the components at low C* region, the non-conservative or excessive conservative results may be produced. Therefore, the CCG rate data should be obtained for a wide range of C* by long term laboratory tests or numerical predictions using the stress dependent creep ductility and model.

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Section: Introductionmentioning

confidence: 77%

Effect of stress dependent creep ductility on creep crack growth behaviour of steels for wide range ofC*

Zhang

Wang

Xuan

et al. 2014

Materials at High Temperatures

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“…The stress dependency of the average creep strain rate, : e A , may also be described using the power-law relationship : e A~AA s n A (4) where A A and n A are the power-law stress coefficient and exponent, respectively, and the subscript 'A' is used to emphasise that the constants in the power-law are determined based on the average creep strain rate. Combining equations (2), (3) and (4), the creep strain at failure for a given stress and temperature can be defined as…”

Section: Creep Deformation and Rupture Behaviourmentioning

confidence: 99%

“…4,32 All analyses have been performed on the high constraint C(T) specimen geometry, although wide- Fig. 7a and b for the FE data obtained under PS and PE conditions, respectively.…”

Section: Normalised Reference Stress Variation In Ccg Simulationsmentioning

confidence: 99%

“…1 on the compact tension, C(T), geometry have been attributed to loss of specimen constraint due to plasticity effects in short term (high load) tests and the reduction of creep ductility and retention of specimen constraint in the long term data. 4,9 Hence, creep ductility data are required from long term uniaxial creep tests to examine this trend in the CCG rate. Also noted in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Creep crack growth rate predictions in 316H steel using stress dependent creep ductility

Mehmanparast

Davies

Webster

et al. 2014

Materials at High Temperatures

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Short and long term trends in creep crack growth (CCG) rate data over test times of 500-30 000 h are available for Austenitic Type 316H stainless steel at 550uC using compact tension, C(T), specimens. The relationship between CCG rate and its dependence on creep ductility, strain rate and plastic strain levels has been examined. Uniaxial creep data from a number of batches of 316H stainless steel, over the temperature range 550-750uC, have been collected and analysed. Power-law correlations have been determined between the creep ductility, creep rupture times and average creep strain rate data with stress s normalised by flow stress s 0?2 over the range 0?2,s/s 0?2 ,3 for uniaxial creep tests times between 100 and 100 000 h. Creep ductility exhibits upper shelf and lower shelf values which are joined by a stress dependent transition region. The creep strain rate and creep rupture exponents have been correlated with stress using a two-stage power-law fit over the stress range 0?2,s/s 0?2 ,3 for temperatures between 550 and 750uC, where it is known that power-law creep dominates. For temperature and stress ranges where no data are currently available, the data trend lines have been extrapolated to provide predictions over the full stress range. A stress dependent creep ductility and strain rate model has been implemented in a ductility exhaustion constraint based damage model using finite element (FE) analysis to predict CCG rates in 316H stainless steel at 550uC. The predicted CCG results are compared to analytical constant creep ductility CCG models (termed NSW models), assuming both plane stress and plane strain conditions, and validated against long and short term CCG test data at 550uC. Good agreement has been found between the FE predicted CCG trends and the available experimental data over a wide stress range although it has been shown that upperbound NSW plane strain predictions for long term tests are overly conservative.

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“…These & & data are generally less than that for the AR 316H material at 550 °C, which is typically close to unity [25]. This trend indicates that the elastic contribution in LLD rates generally increases with the percentage pre-compression in the material.…”

Section: C* Validity Criteriamentioning

confidence: 79%

Effects of plastic pre-straining level on the creep deformation, crack initiation and growth behaviour of 316H stainless steel

Mehmanparast

Davies

Dean

et al. 2016

International Journal of Pressure Vessels and Piping

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The effects of the material pre-straining level, in the form of plastic pre-compression at room temperature, on the tensile, creep deformation, creep crack initiation and growth behaviour of 316H stainless steel have been examined at 550 °C. Experiments have been performed on the 4%, 8% and 12% pre-compressed specimens and the results are compared with existing data on the pre-compressed material to investigate the change in mechanical response, creep failure, creep crack initiation and growth behaviour of 316H over a range of plastic pre-straining levels. Comparisons are also made to short term and long term test data on the as-received material. It has been found that creep ductility and rupture times decreased with an increase in pre-strain levels considered. The test results obtained from different material states are discussed in terms of the influence of material pre-straining level on the microstructural deformation, mechanical response, creep deformation and crack growth behaviour of the material.

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Analysis of Creep Crack Initiation and Growth in Different Geometries for 316H and Carbon Manganese Steels

Cited by 35 publications

References 11 publications

Effect of stress dependent creep ductility on creep crack growth behaviour of steels for wide range ofC*

Effect of stress dependent creep ductility on creep crack growth behaviour of steels for wide range ofC*

Creep crack growth rate predictions in 316H steel using stress dependent creep ductility

Effects of plastic pre-straining level on the creep deformation, crack initiation and growth behaviour of 316H stainless steel

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