Application of impression creep data in life assessment of power plant materials at high temperatures

Sun, Wei; Hyde, T H; Brett, S.J.

doi:10.1243/14644207jmda183

Cited by 26 publications

(50 citation statements)

References 9 publications

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“…This technique appears to be useful in power plant component life assessment [6], and has been deployed in-service to support decisions to continue operation as opposed to undertaking immediate repairs. Despite these advantages, the test has some limitations, e.g.…”

Section: Evaluation Of Current Test Methodsmentioning

confidence: 99%

“…Creep and hardness data are not correlated by any mathematical model because of the different parameters they are related to, since creep life is a function of the operating temperature and stress, while hardness, after prolonged service, is mostly related to the thermal aging at the operating temperature [6]. Nevertheless, Brett [12] found that by plotting the variations of minimum creep strain rates obtained by both uniaxial and impression creep tests at 600 °C and at a stress of 155 MPa, against room temperature hardness for Grade P91 steels (with different service histories) the samples with the lowest minimum creep strain rates have the highest hardness (Figure 19-a).…”

Section: Small Specimen Creep Data Correlated With Hardness Data For mentioning

confidence: 99%

“…Nevertheless, Brett [12] found that by plotting the variations of minimum creep strain rates obtained by both uniaxial and impression creep tests at 600 °C and at a stress of 155 MPa, against room temperature hardness for Grade P91 steels (with different service histories) the samples with the lowest minimum creep strain rates have the highest hardness (Figure 19-a). Brett [12] also plotted the time to failure against the hardness (Figure 19-b), and found that the samples with the highest hardness have the longest time to failure as well, where the time to failure for the impression test samples were calculated by using the Monkman-Grant relationship [6,74].…”

Section: Small Specimen Creep Data Correlated With Hardness Data For mentioning

confidence: 99%

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The role of small specimen creep testing within a life assessment framework for high temperature power plant

Morris

Cacciapuoti

Sun

2017

International Materials Reviews

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The safe operation of components operating at high temperature and pressure faces numerous challenges associated with ageing materials and maintaining commercial viability whilst economies transition to a lower carbon future as part of their climate change commitments. Due to these challenges the plant operator faces increasing pressure to ensure that any capital or operational expenditures are optimised and must ensure that they duly recognise plant age, condition, operating regime and ultimately the planned closure date.This review, for the first time, describes how small specimen creep testing can be applied within a practical and deployable life assessment framework and in conjunction with other assessment techniques. The current state of the art for small specimen creep testing is critically reviewed; this also includes a review of traditional techniques used on site for the metallurgical assessment of material condition, with examples from site investigations and assessment campaigns in both conventional and nuclear plant applications.In order to enhance the current practice for assessing the condition of creep ageing components this review proposes the more proactive use of small specimen testing methods for the in-service condition assessment of power plant materials, notably earlier in the plant lifecycle and within a holistic life assessment framework. This is intended to provide a means of calibrating the time dependent response of the component or system being monitored, thereby providing a key reference in-service strain rate measurement, or material property evaluation, that can subsequently be used with other traditionally deployed assessment methods to define a more targeted and cost-effective forward inspection plan. The review describes how small specimen creep testing methods and other complementary tools can be use in a new and structured approach to life management.The current status of small specimen testing methods, for both conventional and nuclear applications, is described along with a detailed discussion on current practice for in-service creep life assessment, with a case study used to illustrate the main principals. A case study is presented for ageing CMV (0.5%Cr0.5%Mo0.25%V) main steam pipework due to the extensive amount of through life data available, which highlights the particular challenges associated with the interpretation of various types of site outage inspection data, in conjunction with on-load plant operational data. The current approach to the assessment of component condition follows well established inspection based practices defined in various industry good practice guides, with expert elicitation and experience used to judge the condition of the component, system and operational risk on return to service.This review proposes a new approach to the holistic life assessment of high temperature plant, with a particular emphasis on more proactive use of small specimen testing. In addition, the review has 2 highlighted other aspects of the current approach to in-...

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Section: Evaluation Of Current Test Methodsmentioning

confidence: 99%

Section: Small Specimen Creep Data Correlated With Hardness Data For mentioning

confidence: 99%

Section: Small Specimen Creep Data Correlated With Hardness Data For mentioning

confidence: 99%

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The role of small specimen creep testing within a life assessment framework for high temperature power plant

Morris

Cacciapuoti

Sun

2017

International Materials Reviews

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“…It is especially useful if this information can be used to predict how much longer the component can safely stay in service. Such information is extremely useful for ranking assessments [3]. By enabling the use of smaller samples to determine creep properties, creep testing can be extended to smaller components.…”

Section: Introductionmentioning

confidence: 99%

Small ring testing of a creep resistant material

Hyde

Sun

et al. 2013

Materials Science and Engineering: A

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Many components in conventional and nuclear power plant, aero-engines, chemical plant etc., operate at temperatures which are high enough for creep to occur. These include steam pipes, pipe branches, gas and steam turbine blades, etc. The manufacture of such components may also require welds to be part of them. In most cases, only nominal operating conditions (i.e. pressure, temperatures, system load, etc.) are known and hence precise life predictions for these components are not possible. Also, the proportion of life consumed will vary from position to position within a component. Hence, non-destructive techniques are adopted to assist in making decisions on whether to repair, continue operating or replace certain components. One such approach is to test a small sample removed from the component to make small creep test specimens which can be tested to give information on the remaining creep life of the component. When such a small sample cannot be removed from the operating component, e.g. in the case of small components, the component can be taken out of operation in order to make small creep test specimens, the results from which can then be used to assist with making decisions regarding similar or future components. This paper presents a small creep test specimen which can be used for the testing of particularly strong and creep resistant materials, such as nickel-based superalloys.

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“…7 Life remnant assessment is an important need for the gas turbine parts such as blades and rotors, especially when they are near the design life. 8 Failure of high temperature rotors and their mechanisms were studied by some researchers. 9, 10 Das and Sivakumar 11 used critical plane approach to study only multiaxial fatigue of a turbine rotor.…”

Section: Introductionmentioning

confidence: 99%

Analysis of unified continuum damage mechanics model of gas turbine rotor steel: Life assessment

Nayebi

Ranjbar

Rokhgireh

2012

Proceedings of the Institution of Mechanical Engineers, Part L:

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In this research, the unified creep continuum damage mechanics model of Lemaitre is used to model the stress-strain behavior of a gas turbine rotor. The unified damage law can model the creep and low cycle fatigue damage. It is based on the increment of the accumulated inelastic strain, which may be due to either creep damage or low cycle fatigue damage. The parameters of the unified continuum damage mechanics model, including Q, Norton constants, and constants of the nonlinear kinematic hardening model are determined and optimized by cyclic tension and relaxation tests. A careful three-dimensional thermal analysis is carried out and the temperature gradient is obtained. This analysis is used to determine stresses of the gas turbine rotor. Creep and low cycle damage are also modeled and stress-strain evolution in the gas turbine rotor is obtained. The replica tests are performed on four points of the rotor surface and formation of the creep voids is verified under a scanning electron microscope. Based on the continuum damage mechanics analysis, the creep-fatigue interaction is considered in modeling and the remaining life of the rotor is estimated.

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Application of impression creep data in life assessment of power plant materials at high temperatures

Cited by 26 publications

References 9 publications

The role of small specimen creep testing within a life assessment framework for high temperature power plant

The role of small specimen creep testing within a life assessment framework for high temperature power plant

Small ring testing of a creep resistant material

Analysis of unified continuum damage mechanics model of gas turbine rotor steel: Life assessment

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