Lifetime Management Research Articles

Fatigue Life Assessment and Lifetime Management of Aluminum Ships Using Life-Cycle Optimization

The development of aluminum ship structures has been promoted in the context of the rapid evolution of high-speed and light-weight vessels. Under the repeated and/or fluctuating application of stresses during voyages, fatigue damage of structural ship members is accumulated. For this reason, fatigue reliability analysis has to be conducted for assessing and predicting lifetime performance of aluminum ships. This assessment offers the opportunity to optimally perform the lifetime ship structural management planning. To allocate limited financial resources required to balance the lifetime reliability of ship structural details and the life-cycle cost, single-or multi-objective optimization can be used. The multi-objective optimization problem has several competing objectives such as:(minimizing the life-cycle maintenance cost,maximizing the fatigue reliability of details with welded attachments, andminimizing the fatigue damage. The S-N (stress vs. number of cycles) approach and available sea loading information are used to evaluate the time-dependent fatigue reliability. In this paper, the estimated fatigue reliability is incorporated into a life-cycle cost optimization problem to find the optimal inspection and repair interventions. The proposed approach is illustrated on an aluminum ship detail.

Application of probabilistic modelling to the lifetime management of nuclear boilers in the creep regime: Part 1

Monte Carlo probabilistic simulation has been applied to a large population of nominally identical components in an AGR boiler operating in the creep regime. The components have a history of defectiveness. The R5 procedure is used to calculate creep-fatigue crack growth rates within a probabilistic programme. The inspection process is also modelled probabilistically. The overall result is a ‘prediction’ of past inspection results which can be used to tune the parameters of the model. The model then makes genuine predictions of the required level of remediations in future overhauls by predicting the inspection results. The probabilistic treatment of both the structural calculations and the inspection process jointly has been shown to assist in clarifying the interpretation of the inspections and ascertaining the true state of the plant.

Long-term health implications of individuals with TBI: A rehabilitation perspective

Individuals with acquired brain injuries often present with lifelong health challenges. Trauma to the body directly related to the injury, physical and medical sequelae resulting from the brain injury itself, and an increase in the observed onset of physical aging are among the problems which require consideration throughout their lives. For many rehabilitation professionals, issues related to medical stability and health maintenance are unfamiliar and intimidating. As both hospital stays shorten and an existing population of individuals with brain injuries' survival and life expectancy rates increase, rehabilitation professionals have been increasingly challenged by medical issues. Rehabilitation nurses are positioned to best navigate these issues and facilitate needed care coordination, early intervention, and ongoing education for individuals, their families, and other caregivers. This article describes common medical complications related to the initial and related disability and aging in individuals with brain injury including chronic and late emerging complications involving all body systems including spasticity and changing mobility, aspiration and dysphagia, incontinence, diabetes, and acute and chronic pain. Strategies for successful management of these issues in a home or community setting are also discussed. Special attention is paid to falls and fall prevention, issues specific to aging women, and nutrition and weight control. Ways to promote positive health behaviors to preserve function are also explored. Additionally, patient and family education as part of a lifetime management plan is discussed.

Bare metal stenting for obstructed small diameter homograft conduits in the right ventricular outflow tract

Our aim was to assess acute hemodynamic changes with stent insertion, outcomes, and factors associated with increased longevity of stented small diameter homograft conduits. Right ventricle-to-pulmonary artery (RV-PA) homograft conduits are commonly used to palliate RV outflow tract obstruction. Bare metal stenting (BMS) and transcatheter pulmonary valve implantation have been shown to relieve obstructed larger diameter conduits and may delay surgical conduit reintervention. Less is known about BMS of small conduits. From 1992 to 2009, BMS was performed to relieve obstruction in 106 homograft conduits that were ≤12 mm at implant. The peak RV-PA gradient fell from 54.3 ± 17.4 mm Hg at baseline to 46.1 ± 15.2 mm Hg after balloon dilation alone and to 25.1 ± 11.4 mm Hg with stenting (all P < 0.001). Higher pre-BMS gradient and RV pressure were the only factors associated with higher post-BMS RV-PA gradient (≥30 mm Hg; both P < 0.001). There were no procedural deaths, two patients required surgical removal of embolized stents. At a median follow-up of 1.6 years, 83 conduits were replaced; freedom from conduit reoperation after BMS was 66% ± 5% at 1 year and 28% ± 5% at 3 years. Factors associated with shorter freedom from reoperation included implanted conduit diameter <10 mm (P = 0.009), higher post-stent RV-PA gradient (P = 0.026), and higher post-stent RV pressure (P < 0.01); only post-stent RV pressure remained significant on multivariable analysis (P < 0.001). BMS was acutely effective for the treatment of obstructed small diameter homograft conduits, with low morbidity. Prolongation of small diameter homograft conduit longevity with BMS may be useful in the lifetime management of conduit dysfunction in this patient population.

PC橋維持管理支援システム(J-BMS PC版)の開発と実橋への適用

PC橋維持管理支援システム(J-BMS PC版)の開発と実橋への適用

Methods of detailed thermal fatigue evaluation of nuclear power plant components

AbstractThe fatigue check of components has to be considered as an essential module of the safety concept as well as the ageing and lifetime management of nuclear power plants. It is based on special safety requirements in the design phase as well as in the framework of the ageing and lifetime management. Considerable efforts of load identification (fatigue monitoring) as well as the strict code conformity are characteristic features. The predominance of thermal cyclic loadings as well as relevant stress/strain amplitudes in the low cycle fatigue regime (LCF) are peculiarities compared to other technical domains. The code based fatigue concept is explained in the first part of the contribution. Furthermore, potentials for the quantification of existing margins are shown. On this, a new approach of mechanistic simulation of the thermal cyclic fatigue process based on short crack fracture mechanics is described in detail in the second part.

Conservative snapshot-based actor garbage collection for distributed mobile actor systems

A mobile agent system consists of mobile agents, each of which can transport its state and code to any computing host in the system. The system is able to perform dynamic network reconfiguration and user customization to keep it flexible and effective. A mobile agent system can be theoretically depicted by the mobile actor model, in which a mobile actor is an autonomous computing entity and communicates with other actors by using asynchronous messages. Automatic distributed actor garbage collection, one of the important issues of lifetime management of mobile actors, can help high-level programming and efficient resource management in such a mobile actor system. Therefore, it is beneficial to design an intelligent management strategy to automatically detect and collect mobile actor garbage. In this paper, we propose a mechanism for mobile actor garbage collection using a novel conservative snapshot-based algorithm. Compared with prior similar work, the proposed mechanism is more flexible because it does not assume FIFO communication and any network topology. Moreover, it can perform actor garbage collection in a partial set of computing nodes, and thus can reduce the synchronization overhead while taking a global snapshot on a particular distributed application. In addition, the proposed mechanism does not restrict mutation operations such as actor creation and actor migration while taking a global snapshot. We have conducted experiments to evaluate the overhead of the proposed mechanism, and the results showed that the proposed mechanism is practical.

Time-dependent performance indicators of damaged bridge superstructures

The ability of a structure to survive an extreme event without collapse reduces in time due to deterioration processes. Therefore, in the lifetime management of structures and infrastructures, the resistance to sudden local damage has to be considered together with the effect of progressive deterioration. The aim of this paper is to present a framework for computation of time-dependent performance indicators of civil structures and infrastructures, with emphasis on bridges, including reliability, vulnerability, robustness and redundancy. A brief theoretical background and selected structural performance indicators regarding vulnerability, redundancy and robustness are presented. The approach is based on probabilistic performance assessment supported by finite element analysis and applied to an existing bridge. Time-variation of vulnerability, redundancy and robustness associated with various damage scenarios under uncertainty and the effects of several loading conditions on performance are investigated.

Probabilistic dynamic behavior of a long-span bridge under extreme events

In addition to moderate wind and normal traffic scenarios, it is known that some extreme events may also occur on long-span bridges. These extreme events may include complex traffic congestion on the bridge, coupled with moderate or even strong wind. It is known that the excessive dynamic response and stress level of the bridge under these rare but critical scenarios, even for a very short period, may cause critical damage initiation or accumulation on some local bridge members. In addition to accelerating damages, the extreme events (e.g. heavy traffic) may even trigger the hazardous collapse of a whole bridge in some rare cases, especially when some hidden damage or design flaw has not been detected. Therefore, even though the extreme cases associated with congested traffic and/or windy weather are relatively rare, it is important for bridge engineers to appropriately look into these unusual extreme events during design and life-time management. By applying the general Bridge/Traffic/Wind coupled analysis methodology, the present study focuses on (1) conducting the cellular automaton (CA)-based traffic flow simulation of a long-span bridge and connecting roadways under incidental situations, (2) defining representative scenarios for the extreme events, and (3) numerically studying the bridge performance under these possible extreme events. By conducting studies on a comprehensive set of possible scenarios, it is anticipated that better understanding of extreme events of long-span bridges from the perspectives of strength and serviceability design will be achieved, which may contribute to the future design specification about long-span bridges. The proposed methodology will also offer a reasonable framework to replicate probabilistic traffic flow, characterize dynamic interaction and assess structural performance under those rare but critical situations integrally.

ICONE19-43985 Application of New Core Monitoring System "GNF-ARGOS" to Tokai No.2 Power Station (1) : System Developments

New BWR core monitoring system "GNF-ARGOS" has been applied to the Japan Atomic Power Company Tokai No.2 power station. ARGOS incorporated a BWR core physics simulator AETNA to evaluate the core performance. ARGOS is the world first system that adopted the three neutron energy group core simulator for on-line BWR core monitoring. Core monitor functions are enhanced, including life time management for in-core components. A very intuitive user interface was developed. ARGOS is composed of Linux servers and Windows PC clients, which are configured as a redundant system. The system is monitored by an additional server that displays system diagnosis on a touch panel monitor. ARGOS has an "Operator Window" which continuously displays the status of the plant and the core performance evaluation. By password authorization, the window is switched to an 'Engineer Window', on which site engineers can demand various core monitoring/prediction functions and reports. Currently the official core monitor of Tokai No.2 power station is 3D-Monicore system. ARGOS is planned to be an official monitor after validation during parallel run with the current system.

The Role of the External and Internal Reinforcing on the Structural Integrity of Damaged Steel Pipelines

The integrity and the lifetime management of different engineering structures and structural elements is one of the important technical-economic problems nowadays. The purpose of the paper is to present the role of the external and internal reinforcing on the structural integrity of industrial and transporting steel pipelines, based on experimental investigations. External and internal reinforcement technologies were developed using carbon fibre reinforced polymer matrix composite (CFR PMC) and glass fibre reinforced polymer matrix composite (GFR PMC), respectively. Fatigue and burst tests were performed on large pipeline sections containing natural and artificial metal loss defects, seam and girth welds including weld defects (“NOT PASSED” quality). Burst tests were executed after fatigue tests, using 100.000 cycles. Different corrosion defects were tested as natural defects, and longitudinal and circumferential gouges as well as holes and through holes were investigated as artificial defects. Both unreinforced and reinforced pipeline sections were examined. The applicability of the hybrid structure (steel + polymer matrix composite) was demonstrated by means of the experimental results.

The Role of the External and Internal Reinforcing on the Structural Integrity of Industrial and Transporting Steel Pipelines

The lifetime management of different engineering structures and structural elements is one of the important technical-economic problems nowadays. On the one hand, the aim of our research work is to develop an integrity management plan for pipelines and pipeline systems, and afterwards a Pipeline Integrity Management System. Material databases play important role both on the integrity management and on the engineering critical assessment of the pipeline systems. On the other hand, the aim of our research work is to establish the Pipeline Integrity Management System with different data, frequently with experimental data. The direct purpose of the paper is to present the role of the external and internal reinforcing on the structural integrity of industrial and transporting steel pipelines, based on own examinations. External and internal reinforcement was developed using carbon fibre and glass fibre polymer matrix composites, respectively. Fatigue and burst tests were performed on pipeline sections containing natural and artificial metal loss defects, and girth welds including weld defects. Both unreinforced and reinforced pipeline sections were examined. The burst pressures belonging to the unreinforced and the reinforced pipelines, and belonging to the passed and not passed girth welds were compared.

Experimental and numerical investigations of external reinforced damaged pipelines

The lifetime management of different engineering structures and structural elements is one of the important technical-economic problems nowadays. The purpose of the paper is to present the role of the external reinforcing on the structural integrity of industrial and transporting steel pipelines, based on experimental and numerical investigations. External reinforcement was developed using carbon fibre polymer matrix composite (PMC). Fatigue and burst tests were performed on pipeline sections containing natural and artificial metal loss defects, and girth welds including weld defects (passed and not passed quality). Both unreinforced and reinforced pipeline sections were examined. For the FEM investigation of the problem three groups of mechanical models are applied: multilayered elastic shell, 3D elastic solid and 3D elastic-plastic solid FEM models. The aim of this numerical analysis is to clarify the deformation, stresses and strains in the surrounding area of defects both in the steel pipe and in the composite reinforcement. A further task is to determine numerically the width of the reinforcement and the number of layers needed for reinforcement or repair. The applicability of the hybrid structure (steel + PMC) was demonstrated by means of the experimental and the numerical results.

Computational study of conjugate heat transfer in T-junctions

In this work we focus on the numerical prediction of temperature fluctuations induced in solid materials through turbulent mixing processes. As test case we use the mixing of two streams of different temperature in a T-junction. Due to the turbulent mixing of the two streams temperature fluctuations occur which are also transferred to the solid walls in contact with the fluid. Such fluctuations in the solid material may lead to thermal fatigue and are therefore relevant for the lifetime management of components used in nuclear power plants (NPP). We investigate the mixing in T-junctions made of different materials and having different pipe wall thicknesses. The temperature difference between the streams in the main and side branch is set to 75 °C and the mass flow rate in the main pipe is three times larger than in the side branch. In a first step we perform a set of simulations by using different formulations of the large-eddy simulation (LES) subgrid scale model, i.e. classical Smagorinsky model and dynamic procedure, to identify the influence of the modeled subgrid scales on the simulation results. The comparison between available experimental data and the numerical results reveals a good agreement when using the dynamic procedure. In a second step we address the temperature fluctuations in the solid wall subject to the wall thickness. The influence of the wall thickness is represented as a damping effect on the temperature fluctuations in radial direction in the pipe material. This study shows the capability of LES to predict thermal fluctuations in turbulent mixing.

Magnetic measurements for evaluation of radiation damage on nuclear reactor materials

It is important for the plant lifetime management to estimate the loss of toughness and other effects, e.g. increase of yield strength and hardness, caused by irradiation. This paper deals with the use of magnetic measurements to determine the irradiation effects on nuclear reactor structural materials. Three types of nuclear reactor materials were studied. Samples of the materials were irradiated with different neutron fluences. The Magnetic Barkhausen Emission was measured using stabilised flux mode, i.e., control of the magnetic flux within the sample to compensate for leakage and variations on the flux. The samples were carefully identified according to position and the cutting direction within the steel forging block. Anisotropy effect due to sample cutting direction was observed and it masks the magnetic signal results induced by the irradiation effects. The results on the specimens cut in the same direction shows correlation with irradiation induced material hardening and its dependence on fluence. Different materials show different hardening levels. Barkhausen emission results were correlated to neutron fluence taking into account the cutting direction.

Bariatric surgery was dominant over conventional therapy for lifetime management of type 2 diabetes in obese patients

Source Citation Keating CL, Dixon JB, Moodie ML, et al. Cost-effectiveness of surgically induced weight loss for the management of type 2 diabetes: modeled lifetime analysis. Diabetes Care. 2009;32...

C++ lambda expressions and closures

A style of programming that uses higher-order functions has become common in C++, following the introduction of the Standard Template Library (STL) into the standard library. In addition to their utility as arguments to STL algorithms, function parameters are useful as callbacks on GUI events, defining tasks to be executed in a thread, and so forth. C++’s mechanisms for defining functions or function objects are, however, rather verbose, and they often force the function’s definition to be placed far from its use. As a result, C++ frustrates programmers in taking full advantage of its own standard libraries. The effective use of modern C++ libraries calls for a concise mechanism for defining small one-off functions in the language, a need that can be fulfilled with lambda expressions. This paper describes a design and implementation of language support for lambda expressions in C++. C++’s compilation model, where activation records are maintained in a stack, and the lack of automatic object lifetime management make safe lambda functions and closures challenging: if a closure outlives its scope of definition, references stored in a closure dangle. Our design is careful to balance between conciseness of syntax and explicit annotations to guarantee safety. The presented design is included in the draft specification of the forthcoming major revision of the ISO C++ standard, dubbed C++0x. In rewriting typical C++ programs to take advantage of lambda functions, we observed clear benefits, such as reduced code size and improved clarity.

Abstract 3176: Percutaneous Pulmonary Valve Implantation Is A Successful Treatment Option For RVOT Conduit Failure After Ross Procedure

Background- The Ross operation offers good autograft function and low re-operation rates for the left ventricular outflow tract, however, the rate of conduit dysfunction in the right ventricular outflow tract (RVOT) remains a significant concern. Percutaneous pulmonary valve implantation (PPVI) is a novel trans-catheter treatment option for RVOT conduit dysfunction. Methods and Results- Of the 156 patients who underwent PPVI at our institutions with the current device, we retrospectively analyzed the outcomes of 11 patients (mean age: 26±5 years) who had RVOT conduit failure, 11.3±3.2 years following the Ross operation. PPVI could be performed in all patients (procedure time: 100±15 min; fluoroscopy time: 20±6 min). The RVOT gradient during catheterization and pulmonary regurgitant fraction (PRF) measured on magnetic resonance imaging (MRI) fell after PPVI (RVOT gradient: 35±6.5 mmHg to 14±2.8 mmHg, P&lt;0.01; PRF: 18±6% to 3±2%, P&lt;0.05). During mean follow-up of 17.4±5.2 months, there was 1 explantation (re-stenosis). The probability for freedom from RVOT re-operation was 100% at 1 year and 85.7% at 3 years. Conclusions- Failure of the conduit in the RVOT following Ross procedure can be successfully treated with PPVI to decrease the cumulative surgical burden in the lifetime management of congenital or acquired lesions of ventricular outflow tracts.

Reliability-based assessment of polyethylene pipe creep lifetime

Lifetime management of underground pipelines is mandatory for safe hydrocarbon transmission and distribution systems. The use of high-density polyethylene tubes subjected to internal pressure, external loading and environmental variations requires a reliability study in order to define the service limits and the optimal operating conditions. In service, the time-dependent phenomena, especially creep, take place during the pipe lifetime, leading to significant strength reduction. In this work, the reliability-based assessment of pipe lifetime models is carried out, in order to propose a probabilistic methodology for lifetime model selection and to determine the pipe safety levels as well as the most important parameters for pipeline reliability. This study is enhanced by parametric analysis on pipe configuration, gas pressure and operating temperature.

The 2005 ISMS Practice Prize Winner—Customer Equity and Lifetime Management (CELM) Finnair Case Study

The Customer Equity and Lifetime Management (CELM) solution is based on a decision-support system that offers marketing managers a scientific framework for the optimal planning and budgeting of targeted marketing campaigns to maximize return on marketing investments. The CELM technology combines advanced models of Markov decision processes (MDPs), Monte Carlo simulation, and portfolio optimization. MDPs are used to model customer dynamics and to find optimal marketing policies that maximize the value generated by a customer over a given time horizon. Lifetime value optimization is achieved through dynamic programming algorithms that identify which marketing actions, such as cross-selling, up-selling, and loyalty marketing campaigns, transition customers to better value and loyalty states. The CELM technology can also be used to simulate the financial impact of a given marketing policy using Monte Carlo simulation. This allows marketing managers to simulate several targeting scenarios to assess budget requirements and the expected impact of a given marketing policy. The benefits of the solution are illustrated with the Finnair case study, where CELM has been used to optimize marketing planning and budgeting for Finnair’s frequent-flyer program (FFP).