Academic literature on the topic 'Mean residual lifetime'
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Journal articles on the topic "Mean residual lifetime"
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Alshehri, Mashael A., and Mohamed Kayid. "Mean Residual Lifetime Frailty Models: A Weighted Perspective." Mathematical Problems in Engineering 2021 (December 13, 2021): 1–21. http://dx.doi.org/10.1155/2021/3974858.
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The mean residual life frailty model and a subsequent weighted multiplicative mean residual life model that requires weighted multiplicative mean residual lives are considered. The expression and the shape of a mean residual life for some semiparametric models and also for a multiplicative degradation model are given in separate examples. The frailty model represents the lifetime of the population in which the random parameter combines the effects of the subpopulations. We show that for some regular dependencies of the population lifetime on the random parameter, some aging properties of the subpopulations’ lifetimes are preserved for the population lifetime. We indicate that the weighted multiplicative mean residual life model generates positive dependencies of this type. The copula function associated with the model is also derived. Necessary and sufficient conditions for certain aging properties of population lifetimes in the model are determined. Preservation of stochastic orders of two random parameters for the resulting population lifetimes in the model is acquired.
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Tang, L. C., Y. Lu, and E. P. Chew. "Mean residual life of lifetime distributions." IEEE Transactions on Reliability 48, no. 1 (March 1999): 73–78. http://dx.doi.org/10.1109/24.765930.
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Jupp, P. E. "Characterization of matrix probability distributions by mean residual lifetime." Mathematical Proceedings of the Cambridge Philosophical Society 100, no. 3 (November 1986): 583–89. http://dx.doi.org/10.1017/s0305004100066305.
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The mean residual lifetime of a real-valued random variable X is the function e defined byOne of the more important properties of the mean residual lifetime function is that it determines the distribution of X. See, for example, Swartz [10]. References to related characterizations are given by Galambos and Kotz [3], pages 30–35. It was established by Jupp and Mardia[6] that this property holds also for vector-valued X. As (1·1) makes sense if X is a random symmetric matrix, it is natural to ask whether the property holds in this case also. The purpose of this note is to show that, under certain regularity conditions, the distributions of such matrices are indeed determined by their mean residual lifetimes.
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Kayid, M. "Characterizations of the Weak Bivariate Failure Rate Order and Bivariate IFR Aging Class." Journal of Mathematics 2022 (April 30, 2022): 1–9. http://dx.doi.org/10.1155/2022/2573667.
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In this paper, two characterizations of the weak bivariate failure rate order over the bivariate Laplace transform order of two-dimensional residual lifetimes are given. The results are applied to characterize the weak bivariate failure rate ordering of random pairs by the weak bivariate mean residual lifetime ordering of the minima of pairs with exponentially distributed random pairs with unspecified mean. Moreover, a well-known bivariate aging term, namely, the bivariate increasing failure rate, is characterized by the weaker bivariate decreasing mean residual lifetime property of a random pair of minima.
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Ebrahimi, Nader. "Estimation of Two Ordered Mean Residual Lifetime Functions." Biometrics 49, no. 2 (June 1993): 409. http://dx.doi.org/10.2307/2532554.
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Finkelstein, Maxim. "On relative ordering of mean residual lifetime functions." Statistics & Probability Letters 76, no. 9 (May 2006): 939–44. http://dx.doi.org/10.1016/j.spl.2005.10.027.
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Triantafyllou, Ioannis S. "On the Lifetime and Signature of Constrained (k, d)-out-of-n: F Reliability Systems." International Journal of Mathematical, Engineering and Management Sciences 6, no. 1 (October 29, 2020): 66–78. http://dx.doi.org/10.33889/ijmems.2021.6.1.006.
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In the present paper we carry out a reliability study of the constrained (k, d)-out-of-n: F systems with exchangeable components. The signature vector is computed by the aid of the proposed algorithm. In addition, explicit signature-based expressions for the corresponding mean residual lifetime and the conditional mean residual lifetime of the aforementioned reliability system are also provided. For illustration purposes, a well-known multivariate distribution for modelling the lifetimes of the components of the constrained (k, d)-out-of-n: F structure is considered.
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Finkelstein, M. S. "On the shape of the mean residual lifetime function." Applied Stochastic Models in Business and Industry 18, no. 2 (2002): 135–46. http://dx.doi.org/10.1002/asmb.461.
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Navarro, Jorge, and Serkan Eryilmaz. "Mean Residual Lifetimes of Consecutive-k-out-of-n Systems." Journal of Applied Probability 44, no. 1 (March 2007): 82–98. http://dx.doi.org/10.1239/jap/1175267165.
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In this paper we study reliability properties of consecutive-k-out-of-n systems with exchangeable components. For 2k ≦ n, we show that the reliability functions of these systems can be written as negative mixtures (i.e. mixtures with some negative weights) of two series (or parallel) systems. Some monotonicity and asymptotic properties for the mean residual lifetime function are obtained and some ordering properties between these systems are established. We prove that, under some assumptions, the mean residual lifetime function of the consecutive-k-out-of-n: G system (i.e. a system that functions if and only if at least k consecutive components function) is asymptotically equivalent to that of a series system with k components. When the components are independent and identically distributed, we show that consecutive-k-out-of-n systems are ordered in the likelihood ratio order and, hence, in the mean residual lifetime order, for 2k ≦ n. However, we show that this is not necessarily true when the components are dependent.
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Navarro, Jorge, and Serkan Eryilmaz. "Mean Residual Lifetimes of Consecutive-k-out-of-n Systems." Journal of Applied Probability 44, no. 01 (March 2007): 82–98. http://dx.doi.org/10.1017/s0021900200002734.
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In this paper we study reliability properties of consecutive-k-out-of-n systems with exchangeable components. For 2k ≦ n, we show that the reliability functions of these systems can be written as negative mixtures (i.e. mixtures with some negative weights) of two series (or parallel) systems. Some monotonicity and asymptotic properties for the mean residual lifetime function are obtained and some ordering properties between these systems are established. We prove that, under some assumptions, the mean residual lifetime function of the consecutive-k-out-of-n: G system (i.e. a system that functions if and only if at least k consecutive components function) is asymptotically equivalent to that of a series system with k components. When the components are independent and identically distributed, we show that consecutive-k-out-of-n systems are ordered in the likelihood ratio order and, hence, in the mean residual lifetime order, for 2k ≦ n. However, we show that this is not necessarily true when the components are dependent.
Dissertations / Theses on the topic "Mean residual lifetime"
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Bekker, Leonid. "Association between mean residual life (MRL) and failure rate functions for continuous and discrete lifetime distributions." FIU Digital Commons, 2002. http://digitalcommons.fiu.edu/etd/1479.
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The purpose of this study was to correct some mistakes in the literature and derive a necessary and sufficient condition for the MRL to follow the roller-coaster pattern of the corresponding failure rate function. It was also desired to find the conditions under which the discrete failure rate function has an upside-down bathtub shape if corresponding MRL function has a bathtub shape. The study showed that if discrete MRL has a bathtub shape, then under some conditions the corresponding failure rate function has an upside-down bathtub shape. Also the study corrected some mistakes in proofs of Tang, Lu and Chew (1999) and established a necessary and sufficient condition for the MRL to follow the roller-coaster pattern of the corresponding failure rate function. Similarly, some mistakes in Gupta and Gupta (2000) are corrected, with the ensuing results being expanded and proved thoroughly to establish the relationship between the crossing points of the failure rate and associated MRL functions. The new results derived in this study will be useful to model various lifetime data that occur in environmental studies, medical research, electronics engineering, and in many other areas of science and technology.
Books on the topic "Mean residual lifetime"
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Hamilton, Kirk, and Gang Liu. Human Capital, Tangible Wealth, and the Intangible Capital Residual. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198803720.003.0011.
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Since income is the return on wealth, the total wealth of a country should be around twenty times its GDP. Instead, the average observed ratio from the System of National Accounts (SNA) is a factor of 2.6–6.6. Clearly, wealth accounts are incomplete. Estimating the value of the most obvious omission, human capital, using the lifetime income approach for a sample of thirteen (mostly high-income) countries yields a mean share of human capital in total wealth of 63 per cent—four times the value of produced and fourteen times that of natural capital. But for selected high-income countries an average of 25 per cent of total wealth remains unaccounted. This residual intangible is arguably the ‘stock equivalent’ of total factor productivity—the value of assets such as institutional and social capital that augment the capacity of produced, natural, and human capital to support a stream of consumption into the future.
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Manson, S. S., and G. R. Halford. Fatigue and Durability of Structural Materials. ASM International, 2006. http://dx.doi.org/10.31399/asm.tb.fdsm.9781627083447.
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Fatigue and Durability of Structural Materials serves as a reference, textbook, and guide for engineers who design or maintain equipment subject to fatigue damage and failure. Using images, diagrams, and equations, it explains how cyclic loading affects the composition, structure, and properties of metals and the lifetime and performance of machine components. It describes the fundamentals of fatigue analysis, the role of dislocations, the concept of mean stress, the complexity of multiaxial loading, and the impact of cumulative fatigue damage. It discusses the influence of notches and cracks on shaft failures, the effects of fatigue on nonmetals, the characteristics of fatigue mechanisms, and the use of fatigue life equations and approximating techniques. It also defines important terms and concepts, includes relevant background information, and provides guidelines and best practices on part sizing, materials selection and processing routes, fabrication methods, surface preparation, the introduction of favorable residual stresses, material restoration and healing, and permissible crack growth. For information on the print version, ISBN 978-0-87170-825-0, follow this link.
Book chapters on the topic "Mean residual lifetime"
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Finkelstein, M. S. "THE FAILURE RATE AND THE MEAN RESIDUAL LIFETIME OF MIXTURES." In Series on Quality, Reliability and Engineering Statistics, 165–83. WORLD SCIENTIFIC, 2001. http://dx.doi.org/10.1142/9789812799548_0010.
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Fatima, Bouakkaz, Ali Wided, Guemmadi Sabrina, and Derdour Makhlouf. "K-Means Efficient Energy Routing Protocol for Maximizing Vitality of WSNs." In Computational Optimization Techniques and Applications. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96567.
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The progress of wireless communication and microelectronics create wireless sensor network, which is a very important field of research, The utilization of Wireless Sensor Network is growing and have a diversity applications like Military applications, Agriculture, Health care, Medical monitoring. The main issue of WSN is energy consumption, where prolonged network lifetime, is important necessity. From the solution proposed the Clustering with k-means is a successful technique for achieving these goals. This work is adaptation of one of the most famous protocol in WSN witch is Low Energy Adaptive Clustering Hierarchy (LEACH) in the clustering phase where the choice of number of clusters and their CHs.sing the k-means method and the distance between nodes and residual energy. Clustering k-means given a best partition with cluster separation. This chapter regulated as below, in section two we discussed related work used k-means to improved vitality of WSN. In the next section, we introduce the proposed adaptation protocol. The simulation resultsusing MATLAB have shown that the proposed protocol outperforms LEACH protocol and optimizes the nodes energy and thenetwork lifetime.
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Kulkarni, Nandkumar Prabhakar, Neeli Rashmi Prasad, and Ramjee Prasad. "An Evolutionary Mobility Aware Multi-Objective Hybrid Routing Algorithm for Heterogeneous WSNs." In Sensor Technology, 221–37. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-2454-1.ch011.
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Researchers have faced numerous challenges while designing WSNs and protocols in numerous applications. Amongst all sustaining connectivity and capitalizing on the network lifetime is a serious deliberation. To tackle these two problems, the authors have considered Mobile Wireless Sensor Networks (MWSNs). In this paper, the authors put forward an Evolutionary Mobility aware multi-objective hybrid Routing Protocol for heterogeneous wireless sensor networks (EMRP). EMRP selects the optimal path from source node to sink by means of various metrics such as Average Energy consumption, Control Overhead, Reaction Time, LQI, and HOP Count. The Performance of EMRP when equated with Simple Hybrid Routing Protocol (SHRP) and Dynamic Multi-Objective Routing Algorithm (DyMORA) using parameters such as Average Residual Energy (ARE), Delay and Normalized Routing Load. EMRP improves AES by a factor of 4.93% as related to SHRP and 5.15% as related to DyMORA. EMRP has a 6% lesser delay as compared with DyMORA.
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Eftink, Maurice R., and Glen D. Ramsay. "Temperature- and Pressure-Induced Unfolding of a Mutant of Staphylococcal Nuclease A." In High Pressure Effects in Molecular Biophysics and Enzymology. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195097221.003.0008.
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Nuclease conA is a hybrid version of Staphylococcal nuclease that contains a six amino acid (β-turn substitute from concanavalin A. This hybrid protein has a much lower thermodynamic stability than does the wild-type protein. This enables the unfolding of the protein to be achieved easily by several types of perturbations. From temperature-, pressure-, and denaturant-induced unfolding studies, we have found the free energy change for unfolding, ΔG°un, to be approximately 1.4 kcal mo−1 at pH 7, 0.1 M NaCI, and 20 °C, as compared to a thermodynamic stability of approximately 5.5–6 kcal mo−1 for wild-type nuclease A. Due to its reduced thermodynamic stability, nuclease conA also shows evidence of unfolding at low-temperature (cold denaturation), with a temperature of maximum stability of 13–15 °C. The thermal unfolding of nuclease conA is shown to be two-state by simultaneous measurement of fluorescence and CD changes as a function of temperature, using a modified AVIV CD instrument. Increased hydrostatic pressure unfolds nuclease conA in what appears to be a two-state manner, with an apparent of ΔV°un approximately —100 ml mol−1. From studies of the pressure (p)-induced unfolding of this hybrid protein as a function of temperature (T), we can define the complete p-T free energy surface for the unfolding transition. In auxiliary studies, we have characterized the fluorescence intensity decay and anisotropy decay of the single tryptophan residue (Trp-140) of nuclease conA in the native state and in the unfolded state induced by temperature, pressure, and denaturant. For each type of perturbation, there is a red shift in fluorescence, a lowering of the mean fluorescence lifetime, and a lowering of the rotational correlation time of the tryptophan residue to a value of ~1 ns (compared to 10–15 ns for the native state). The thermodynamics of the unfolding of proteins has received renewed interest in recent years, owing to the availability of a rich variety of mutant proteins and to advances in our understanding of their structural features. Among the questions being asked are, What are the relative energetic contributions of the hydrophobic effect and other interaction forces?
Conference papers on the topic "Mean residual lifetime"
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Martinez Perez, Imanol, Philippe Bastid, Andrei Constantinescu, and Vengatesan Venugopal. "Multiaxial Fatigue Analysis of Mooring Chain Links Under Tension Loading: Influence of Mean Load and Simplified Assessment." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77552.
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Current standards (as an example, DNV-OS-E301[1] and API-RP-2SK[2]) do not account for mean load in the fatigue assessment of mooring chains. Both standards, provide S-N curves derived from experimental work without specifying the mean load for which they have been obtained or proposing a mean load correction function. This paper reports a fatigue analysis study of mooring chains under Tension Loading using a multiaxial fatigue criterion for two different mean loads. Multiaxial fatigue criteria enable to account directly for complex phenomena, such as residual stresses, non-proportionality of the stress tensor, among others. This paper presents an example of the implementation of the Dang Van fatigue criterion for studying the fatigue behavior of mooring chains under tension. It quantifies the effect of the mean load on the fatigue lifetime and the failure location. Furthermore, it also proposes a simplified approach to reduce the complexity and the computational time of the fatigue analysis using Dang Van fatigue criterion. The paper is organized as follows: in the first part an example of the fatigue assessment is reported. Two different loading conditions with the same load amplitude but different mean loads are studied. The assessment method is based on two steps: a mechanical analysis and a fatigue analysis. In the second part, a simplified fatigue assessment method is proposed. As part of this method, a ratio between the fatigue lifetimes of two loading conditions, which have the same load amplitude but different mean load, is formulated. This ratio has been obtained analytically using the geometric representation of the Dang Van fatigue Criterion. Finally, the paper ends with a discussion, based on recent works, regarding the formulation of the locus of the Dang Van criterion and the fatigue properties used for the calibration of this criterion.
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Linn, Stefan, Christian Kontermann, and Matthias Oechsner. "Aspects of Creep Fatigue Lifetime Assessment for High Temperature Components With Accumulative Model." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90909.
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Abstract Alternating temperatures induce thermomechanical stresses in thick-walled components such as turbine rotors or housings, which can lead to fatigue and superimposed creep. Subsequently, damage can occur at their heated surfaces. Under the nowadays prevailing operating conditions of power plants with multiple cold, warm and hot starts as reaction to the high volatility of electric demand from fossil fired power plants for ensuring grid stability, methods for lifetime assessment are coming more into the focus of investigations and research. Engineers are trying to estimate the residual lifetimes of in-service components and operators of power plants ask for strategies to minimize the calculative material damage while simultaneously providing a maximum flexibility with shortest response times on altered demands. Among constitutive models, which are not subject of this paper, accumulative models for lifetime assessment were introduced several decades ago and are partially considered in applicable standards. Such models based on a damage accumulation are easy to apply but they are considered to be either very imprecise or very conservative, while the conservatism reflects the necessity of large safety margins. This paper summarize a few measures, which are suitable to improve the predictive quality of models based on a simple time-fraction rule. The proposed model is based on a synthesis of hysteresis loops for isothermal and non-isothermal conditions, concepts for consideration of cyclic softening or hardening during lifetime, concepts for dealing with internal back stresses, mean strains or stresses, and for accounting of creep-fatigue interaction. The latter is based on a so-called transition time concept, where the creep damage during dwell times partially attributes to the portion of fatigue damage, which in turn is determined from fatigue life curves for dwell time experiments. In addition, the model comprises a concept for the post-processing of transient FEM calculations and dealing with multiaxial loading conditions. Since the essentials of the proposed method with the transition time concept were published more than 10 years ago, the listed modifications improve the benefit for daily engineering usage. Validation experiments provide evidence of the models predicting capabilities with acceptable uncertainty.
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Kadavath, Gokulnath, Jino Mathew, James Griffin, David Parfitt, and Michael E. Fitzpatrick. "Magnetic Barkhausen Noise Method for Characterisation of Low Alloy Steel." In ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-94073.
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Abstract Application of NDE techniques to operating reactor materials is useful for the determination of deviations resulting from material inhomogeneity and long-term degradation of properties from irradiation damage. A new programme, Nondestructive Evaluation System for the Inspection of Operation-Induced Material Degradation in Nuclear Power Plants (NOMAD), focuses on the non-destructive investigations of Reactor Pressure Vessel (RPV) steels in ageing reactors to better assess the integrity for lifetime management. In this study, Magnetic Barkhausen Noise (MBN) is used to characterise the effect of inhomogeneties in a Jominy end-quench test specimen subjected to differential cooling rates. The effect of material state encompassing different variables such as surface roughness, microstructure, hardness and residual stress is correlated with the MBN Root Mean Square (RMS) parameter in order to enhance the understanding of the embrittlement phenomena. These studies will contribute to the development of a tool that can monitor and quantify the extent of material degradation in operating nuclear power plants.
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Maier, Bernd, Christoph Guster, Richard Tichy, and Werner Ecker. "Different Microstructures in the HAZ of Double Submerged Arc Welded Pipelines and How They Influence the Fatigue Crack Growth." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97975.
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To meet the cost and weight reduction requirements in welded structures, the application of high-strength low-alloy (HSLA) steels also increases in the field of pipeline engineering. However, in comparison to low-strength steels these materials are more susceptible to notches or initial cracks. Therefore, an extensive investigation of fatigue crack growth behaviour in the different microstructural zones of the heat-affected zone (HAZ) is necessary for an appropriate lifetime evaluation of welded pipes. For this purpose, fracture mechanics parameters like thresholds and crack growth rates in the three characteristic microstructural zones of the HAZ as well as in the base material are characterized. The different microstructures are reproduced with a Gleeble thermal simulator system using the same heating curves as measured previously during the welding process of a double submerged arc welded pipeline. The effect of varying stress ratios R on the crack growth threshold and the crack growth curves is also assessed. This knowledge about the mean stress sensitivity is needed for estimating the influence of residual stresses stemming from different manufacturing processes like welding and post-welding treatments, which is essential for a reliable, damage tolerant application of HSLA steels in pipelines.
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Saevik, Svein, and Naiquan Ye. "Armour Layer Fatigue Design Challenges for Flexible Risers in Ultra-Deep Water Depth." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79924.
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Fatigue design of armor layers of flexible risers in ultra-deep water depth fields is challenging. Very high internal pressure and tension impose extreme contact pressure between steel armor layers. The paper outlines how these challenges were handled focusing on the physical effects that needed to be included in the structural mechanics model and the procedure used to calculate the lifetime. Residual stresses due to manufacturing plays an important role in reducing the fatigue performance of the pressure layer by affecting the mean stress level. However, this effect can be improved by selecting appropriate factory acceptance test (FAT). A tailor-made finite element program (BFLEX) has been designed to make this sort of analyses possible and ensure the safety of the flexible riser design for ultra-deep water depth. The study is also extended to discuss the fatigue damage owing to friction in the armor layer for the ultra-deep water flexible because of higher contact pressure on the armor layer. Finally, the fatigue behavior of the pressure amour is a typical multi-axial fatigue problem. Various models are proposed to address how different stress components are exposed for the fatigue calculation.
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Luz, A. M. G., D. Balint, and K. Nikbin. "A Multiscale NDT System for Damage Detection in Thermal Barrier Coatings." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10694.
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Progress in aero-engines and land-based gas turbines is continuously linked with a rise of the operating temperature. TBCs are multilayered structures which function together to effectively lower the temperature of its load-bearing superalloy substrate while simultaneously providing oxidation protection against high temperature combustion environments during operation. They typically comprise of a ceramic top coat for thermal insulation and a metallic bond coat that provides oxidation/corrosion resistance and enhances the adhesion of the YSZ to the superalloy substrate. Due to high-temperature oxidation of the bond coat, a thermally grown oxide (TGO) scale of continuous Al2O3 is formed between the ceramic top coat and the bond coat. The formation and growth of the TGO increases the mismatch of thermal expansion coefficients among the multilayered TBC and induce high thermal stresses leading to spallation of the YSZ coat from the underlying metal. Hence, nondestructive diagnostic tools that could reliably probe the subsurface damage state of TBCs are essential to take full advantage of these systems. In this contribution, a new concept of multiscale NDT system is presented. The instrument uses a combination of imaging-based methods with photoluminescence piezospectroscopy, a laser-based method. Imaging-based methods like mid-infrared reflectance, laser optical backscatter and infrared tomography were used to predict the overall lifetime of the coated component. When TBCs approach the end of life, micro-crack nucleation and propagation at the top coat/bond coat interface increases the amount of reflected light. This rise in reflectance was correlated with the lifetime of the component using a neural network that merges the mean and standard deviation value of the gray level. Photoluminescence piezospectroscopy was subsequently used to give information about the structural integrity of the hot spots identified in the image analysis. This laser-based technique measures in-situ the residual stress in the TGO at room temperature. Damage leads to a relaxation of the local stress which is in turn reflected in the luminescence spectrum shape. However, presently there is no agreement on the best spectral parameters that should be used as a measure of the damage accumulation in the coatings. Therefore, the evolution of luminescence spectrum from as-manufactured to critically damaged TBCs was determined using the finite element method. This approach helped to identify the most suitable spectral parameters for damage detection, improving the reliability of photoluminescence piezospectroscopy as a failure assessment tool for TBCs.
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Bunsell, A. R., S. Blassiau, Y. Mezie`re, Y. Favry, and J. Ch Teissedre. "NDE of Carbon Fiber Composite Pressure Vessels." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33481.
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The use of advanced composites in pressure vessels requires means of periodically evaluating residual minimum lifetimes in order for them to remain in service. Tests based on the prediction of crack propagation are not applicable for composite vessels as, in the absence of stress raisers or localised damage, the failure processes are diffuse and particularly damaging if the reinforcing fibers fail. Acoustic emission has been used to detect this type of damage. At a constant pressure it has been shown that even unidirectional carbon fiber reinforced resin continues to emit which reveals a continuing failure process involving the failure of fibers. The rate of emission under a constant pressure has been shown to obey a simple law which allows the damage accumulation to be calculated as a function of time. A maximum damage threshold can be determined experimentally so that master curves corresponding to the damage accumulated by a pressure vessel under constant pressure over the lifetime required can be calculated. A comparison between these master curves and the rate of damage accumulation of any other pressure vessel of the same type reveals if it will fail before or after the desired lifetime. The effects of pressure variations during service have been seen to be minor but even if this is not the case a comparison with the master curves still allows minimum lifetimes to be predicted. The technique does not require the vessels to be removed from the vehicle which is immobilised for a minimum of time.
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Hackel, Lloyd A., C. Brent Dane, Jon Rankin, Fritz Harris, Chanh Truong, and Serena Marley. "Fatigue and SCC Lifetime Enhancement of Steels by Means of Laser Peening." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-58037.
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Laser peening is a technology employed to induce deep levels of plasticity in materials resulting in compressive residual stress to depths of 5mm (0.2 inches) or deeper enabling increased fatigue strength and lifetimes and greatly enhanced resistance to stress corrosion cracking. An advanced in Nd:glass laser technology has enabled high rate, cost effective industrial deployment of the technology that is now being widely used in aerospace and electric power generation applications. Examples of deep levels of compressive stress and resulting improvements in fatigue life and resistance to stress corrosion cracking will be shown. An advanced beam delivery technology incorporating a robotic arm coupled with a video detection/beam alignment system is enabling rapid setup and application in field applications. The technology has been approved and deployed to prevent early fatigue cracking of key structural components on the F-22 fighter jet. It is also being applied to oil and natural gas applications and has the potential to serve a broad base of field applications including oil and gas lines, on-board ship SCC, nuclear power plant SCC, and fatigue and corrosion applications in upstream exploration and downstream oil refining.
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Buchmann, M., and R. Gadow. "Residual Stress Analysis of Solid Lubricant Containing Coatings on Light Metal Alloys for Aluminum Engine Components." In ITSC 2000, edited by Christopher C. Berndt. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.itsc2000p0293.
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Abstract Mechanical coating properties like hardness, bond strength and tribological features as well as the layer composite lifetime under thermal and mechanical operation stress conditions are mainly influenced by the residual stress situation in the composite. The final residual stress state in thermally spray coated composites is superimposed by different stress mechanisms occurring during the manufacturing process. By means of the micro milling method, residual stresses are measured in a quasi-nondestructive way over the drilling depth. This paper describes the measurement features as well as experimental and numerical results. Measurements are performed on coated plane composite specimens as well as on inside coated bushing guides of aluminum crankcases for different coating materials. The correlation between residual stresses and coating properties is investigated.
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Wang, Min, David O. Harris, Dilip Dedhia, Xinjian Duan, and Michael J. Kozluk. "Two Means of Calculating Very Low Failure Probability." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57595.
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Computation of large break probabilities in pipes when initiating cracks are the dominant degradation mode is difficult, because the problem is dominated by the probability of initiating multiple cracks around the pipe circumference and having them coalesce and grow to become long prior to penetrating the wall to become a leak. The purpose of this paper is to describe two techniques for evaluating very low large break probabilities in pipes with multiple initiating cracks: (i) combining initiation and growth probabilities by a convolution integral, and (ii) sorting through sets of sampled random variables and performing detailed (lifetime) calculations only for particularly “severe” sets. These techniques are demonstrated in an example problem involving primary water stress corrosion crack (PWSCC) initiation and subsequent growth in a piping weldment with high residual stresses by use of a probabilistic fracture mechanics code, PRAISE-CANDU, which is under development to address specific degradation issues in CANDU® reactors.