Browsing by Author "Payten, WM"

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    Crack initiation and crack growth assessment of a high pressure steam chest
    (Elsevier, 2011-01) Payten, WM; Wei, T; Snowden, KU; Bendeich, PJ; Law, M; Charman, D
    Extensive cracking had occurred in a number of high pressure steam chests. An assessment was undertaken based on the R5 British Energy methodology to assess the components for both creep–fatigue damage initiation and crack growth analysis to determine fitness for purpose. The analysis determined that the remaining base rupture endurance life of the component was greater then 1 million hours, however, due to the start-up and shutdown ramp rates, creep–fatigue damage greater then unity has occurred leading to crack initiation in a number of locations. These cracks were confirmed during internal inspection of the steam chest. A subsequent crack growth analysis determined that the component could safely be returned to service for the expected future life of the station. © 2011, Elsevier Ltd.
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    Creep-fatigue prediction of low alloy ferritic steels using a strain energy based methodology
    (American Society of Mechanical Engineers (ASME), 2009-07-26) Payten, WM; Dean, DW; Snowden, KU
    The accumulation of creep-fatigue damage over time is the principal damage mechanism which will eventually lead to crack initiation in critical high temperature equipment. A model that calculates the creep damage under conditions of strain control has been developed that assumes on a macroscopic level that the energy dissipated in the material may be taken as a measure of the creep damage induced in the material. This then assumes that the creep damage is directly proportional to absorbed internal energy density. The model developed is derived from considerations of mechanistic cavity growth. The model makes use of already existing creep data and relatively easily determined fatigue data for estimation of life under non-steady state conditions. The predictions of the energy-density exhaustion approach are compared with the results of creep-fatigue tests on a low alloy ferritic steel 1/2Cr-1/2Mo-1/4V (CMV) and with creep-fatigue calculations using a number of current models. The predicted results of the energy-density model are found to have good correlation with the measured creep-fatigue lives.
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    Design of H-knee: a modular ceramic total knee replacement prosthesis
    (Australasian Ceramic Society, 1988-09) Payten, WM; Ben-Nissan, B
    Degenerative joint disease, recognized as an increasing problem for society, is a direct result of an aging population. When patients present with joint pain, their primary concern is the relief of pain and return to a mobile life style. This often requires replacement of skeletal parts, such as hips, knees, elbows, finger joints, shoulder, and teeth, or fusion of vertebrae, and repair or augmentation of the jaw and bones of the skull. The result is a current worldwide orthopedic market valued at over $5 billion; joint replacement represents 68% of this market. The demand for knee replacements is increasing at approximately 17%/ p.a., with some 300,000 knee joints replaced each year in the United States alone. This increase results in part from increased confidence in using such prostheses. Unfortunately, results do not reinforce this confidence: Long-term clinical results are scattered, and, although the overall rate of failure is reasonably low, it remains unacceptable. A further complication arises because the increase in younger patients undergoing total knee arthroplasty (TKA) may well lead to a higher incidence of eventual failure.
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    Development of a modular ceramic knee prosthesis
    (Humana Press, 2000) Payten, WM; Ben-Nissan, B
    Degenerative joint disease, recognized as an increasing problem for society, is a direct result of an aging population (1). When patients present with joint pain, their primary concern is the relief of pain and return to a mobile life style. This often requires replacement of skeletal parts, such as hips, knees, elbows, finger joints, shoulder, and teeth, or fusion of vertebrae, and repair or augmentation of the jaw and bones of the skull. The result is a current worldwide orthopedic market valued at over $5 billion; joint replacement represents 68% of this market. The demand for knee replacements is increasing at approx 17%/yr, with some 300,000 knee joints replaced each year in the United States alone (2). This increase results in part from increased confidence in using such prostheses. Unfortunately, results do not reinforce this confidence: Long-term clinical results are scattered (3), and, although the overall rate of failure is reasonably low, it remains unacceptable. A further complication arises because the increase in younger patients undergoing total knee arthroplasty (TKA) may well lead to a higher incidence of eventual failure. © Springer Science+Business Media New York 2000
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    HAZ cold cracking - a restrained view
    (Welding Technology Institute of Australia, 1994) Squires, IF; Feng, B; Mercer, D; Payten, WM; Dunne, D; Alam, N
    Heat affected zone (HAZ) hydrogen cracking occurs after the weld has cooled to ambient temperature when the HAZ has transformed and hydrogen has had time to diffuse into it from the weld metal. It is therefore referred to as “cold cracking”. For cracking to occur, a stress needs to be present This will arise inevitably from the local heating and cooling when making the weld, however, the magnitude of the stress will depend on the restraint applied to the weld, the welding conditions used and the geometry of the weld. Recommendations to assist with the avoidance of HAZ cold cracking are available in publications such as WTIA Technical Note 1 “Weldability of Steels” but these cover essentially only the control of the thermal cycle and hydrogen level. The more complex issue of restraint is not included. Consequently the recommendations tend to be either over conservative, hence not fully cost effective, or present unquantied risks. Research work by various authors in this area has been summarised by Suzuki(l) and a basic model produced. The work covered a variety of methodologies and these could not be considered consistent. The present study provides a consistent approach, based on the use of the rigid restraint cracking (RRC) test which allows direct measurement of weld stress. To enable the effect of local stresses to be understood and general models of restraint effects to be developed a finite element analysis (FEA) computer model is being developed in parallel with work on the RRC test Further inputs to the modelling process are being or will be generated from localised studies of mechanical properties in the weld and heat affected zone and from dilatometric studies of the weld. The former will allow more accurate assessment of the behaviour of local stress concentrators in the weld and HAZ. The latter will assist in quantifying the weld metal and HAZ contribution to stress generation.
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    High temperature remaining life cost assessment
    (9th International Conference and Exhibition 2009 Operating Pressure Equipment Incorporating the AINDT Biennial Conference, 2009-08-26) Payten, WM; Bendeich, PJ; Snowden, KU
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    Life assessment methodologies for high temperature branch pieces
    (Australian Institute for Non-Destructive Testing (AINDT), 2009-08-27) Bendeich, PJ; Payten, WM
    Branch pieces in high temperature steam circuits are a common feature of power generating plants both conventional and nuclear. A simple inverse code methodology based on BS1113 [1-3] exists for estimating base rupture life in cylinder to cylinder configurations (branches) under constant pressure and temperature. This does not cover the complex issue of estimating the mixed creep-fatigue effects of cycling which can have a significant influence on damage especially under the current practice of multi-shifting as utilities follow fluctuating energy markets. The current work is primarily aimed at extending the inverse code methodology for base rupture to include cycled loading due to startups and shutdowns. This is achieved under the guidelines of the R5 assessment code by the use of an analytical expression for metastable thermal stresses [4,5] and mapped thermal stress response. System loads are not considered in this work other than by the simple method suggested using the inverse code method. Only 90° non protruding branches are considered in the current work. Examples of 90° branches are examined showing the significance of cyclic loading on a variety of branch configurations. It was observed that base rupture dominates most configurations up to a "cliff edge" in thermal ramp rate followed by rapid accumulation of creep-fatigue damage at higher rates. The results are a useful aid when assessing the optimal operating conditions for individual power stations. © 2009, Australian Institute for Non-Destructive Testing (AINDT)
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    Life management of cycling plant components utilising RemLifeTM software
    (Electric Power Research Institute, 2018-06-06) Abolis, A; Payten, WM
    Due to changes in the mix of power generation that includes both wind and solar, base-load power, for example coal and combined cycle plants, are faced with challenging market conditions that increasingly necessitates operating the units in a cyclic mode. These types of operations can place increased damage rates on the plant. In order to categorise and understand the damage, the common practice is to undertake a Remaining life assessment. These assessments can be both time consuming and expensive, particularly; if multiple components are to be assessed. This paper describes a computer package developed that enables the user to quickly and efficiently assess the remaining life of high temperature components. The program is based around state of the art creep-fatigue methodologies and is designed to rapidly simulate different cycle types and assesses the relative merit of each type of operation. This paper will outline the basic program methodology and illustrate a case study undertaken on a tertiary stage superheater header, that is proposed to change from base load to two shifting operation.
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    A strain energy based methodology for the prediction of creep fatigue damage in high temperature components
    (9th International Conference and Exhibition 2009 Operating Pressure Equipment Incorporating the AINDT Biennial Conference, 2009-08-26) Payten, WM; Dean, DW; Snowden, KU
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    A strain energy density method for the prediction of creep-fatigue damage in high temperature components
    (Elsevier, 2010-03-25) Payten, WM; Dean, DW; Snowden, KU
    The accumulation of creep–fatigue damage over time is the principal damage mechanism which will eventually lead to crack initiation in critical high temperature equipment. A model has been developed that assumes on a macroscopic level that the energy dissipated in the material may be taken as a measure of the creep damage induced in the material and hence the creep damage is directly proportional to absorbed internal energy density. The model developed is derived from considerations of mechanistic cavity growth and is based on rupture elongation to failure data using true strain. The predictions of the energy density exhaustion approach are compared with the results of creep–fatigue tests on low alloy ferritic steels. The predicted results of the energy density model are found to have good correlation with the measured creep–fatigue lives. © 2010, Elsevier Ltd.
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    Stress concentration factors for flat endcaps
    (Engineers Australia, 2017-11-27) Law, M; Payten, WM
    Endcaps on pressure vessels have stress concentrations which lead to fatigue crack initiation and growth during cycling of power generating plant. Finite element analyses of actual endcaps showed a current analytical method to be inaccurate. To develop a model, the maximum non-Mises stress was calculated across a range of geometries using over 380 finite element models. A new analytical method of calculating the stress concentration factor was developed based on the ratio of the von-Mises stress in the fillet to the hoop stress in the remote vessel wall. © 2017 Engineers Australia
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    Structural integrity verification of a primary circuit pump flywheel for the OPAL Research Reactor
    (International Group On Research Reactors, 2005-09-12) Carr, DG; Harrison, RP; Payten, WM
    The flywheels on nuclear reactor coolant pump motors provide inertia to ensure a slow decrease in coolant flow in the event of loss of power; thus preventing fuel damage due to the reduced coolant flow. During operation at normal speed, a flywheel has sufficient kinetic energy to produce high-energy missiles and excessive vibration of the coolant pump assembly if the flywheel should fail. The structural integrity of a large steel flywheel to be used in the primary cooling circuit of the OPAL research reactor at Lucas Heights was evaluated according to the requirements of the US Nuclear Regulatory Commission guide RG 1.14. This guide was developed for nuclear power plants where significant over-speeds in pumps are possible. In the OPAL reactor at ANSTO such pump over-speeds are not possible, however, the code was used to demonstrate the incredibility of failure of the flywheel and consequently a guillotine failure of the primary cooling system pipework.
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    Structural integrity verification of a primary circuit pump flywheel for the OPAL Research Reactor
    (Insitute of Materials Engineering Australasia Ltd, 2006) Carr, DG; Harrison, RP; Payten, WM
    The flywheels on nuclear reactor coolant pump motors provide inertia to ensure a slow decrease in coolant flow in the event of loss of power; thus preventing possible fuel damage due to the reduced coolant flow. During operation at normal speed, a flywheel has sufficient kinetic energy to produce high-energy missiles and excessive vibration of the coolant pump assembly if the flywheel should fail. It is thus important to evaluate the fracture properties of the material to ensure it can withstand the applied stress. The structural integrity of a large steel flywheel to be used in the primary cooling system of the OPAL research reactor at Lucas Heights was evaluated according to the requirements of the US Nuclear Regulatory Commission guide RG 1.14. The guide was developed for nuclear power plants where significant over-speeds in pumps are possible. In the OPAL reactor at ANSTO such pump over-speeds are not possible, however, the code was used to demonstrate the incredibility of failure of the flywheel. An experimental program determined the fracture toughness and tensile properties of the flywheel material; thick section AS 3678 Grade 350 plate. Revision 4 of the well-validated British Energy R6 defect assessment procedure was used to analyse the critical speed and crack length for the flywheel using the two-component failure assessment diagram which considers brittle fracture and plastic collapse. The results of the evaluation are presented in this paper, and illustrate what can be accomplished through the application of modern methods of integrity assessment.
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    Use of a simplified analytical expression for metastable thermal stress analysis and its application to creep-fatigue damage of a 2.25Cr 1Mo thick walled component
    (Elsevier, 2010-02) Payten, WM; Snowden, KU; Bendeich, PJ
    Thick walled pressure vessels are of considerable importance in a wide range of industries. The evaluation of stresses is necessary not only from a design point of view but also for fitness for service analysis of ageing infrastructure. The accumulation of creep–fatigue damage over time is the principal damage mechanism which will eventually lead to crack initiation in critical high temperature fossil plants. Many power stations are being subjected to two-shift operation due to changes in demand and competition from cheaper energy sources, and in the future from added carbon taxes. To assess high temperature components for creep–fatigue damage for example, under faster ramp rates and additional cycles, as a first pass it would be useful to explore the feasible operational envelope using simplified calculations. These are, however, generally not available and more complex finite element analysis is necessary. This paper uses a simplified closed form solution for metastable thermal stresses in thick walled pressure vessels. This form of solution can if necessary be used with either stress concentration factors or superposition of polynomials for more complex components derived from FEA analysis, such that the closed form solution can be used to estimate any ramp rate on the unit. In this case the ramp rates are considered to provide sufficient time to become metastable. Many existing units rely on heavy section 2.25Cr 1Mo steel (P22) pipe-work and tubing, and hence for two shifting can be subjected to high levels of cyclic strain. Based on the simplified expression developed, an operational envelope is explored for thick walled cylinders constructed using P22 steel. Creep–fatigue damage is calculated based on the R5 methodology. The analysis shows that for thick walled components with minimal stress concentrations, creep will dominate the life of the component. However, complex interaction between base rupture, onset of significant cycling, creep, and fatigue dictates the upper bound on feasible ramp rates, as a result it is possible to construct screening curves based on the effective elastic stress intensity range. © 2010, Elsevier Ltd.