bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reliability High Cycle Fatigue Design of Gas Turbine Blading System Using Probabilistic Goodman Diagram
Authors: Shen M.-H. Herman , Nicholas Theodore 
Published: November 2021

Abstract
A framework for the probabilistic analysis of high cycle fatigue is developed. The framework will be useful to U.S. Air Force and aeroengine manufacturers in the design of high cycle fatigue in disk or compressor components fabricated from Ti-6Al-4V under a range of loading conditions that might be encountered during service. The main idea of the framework is to characterize vibratory stresses from random input variables (uncertainties such as initial crack size, crack location, loading, material properties, and manufacturing variability). The characteristics of such vibratory stresses will be portrayed graphically as histograms, or probability density function (PDF). The outcome of the probability measures associated with all the values of a random variable exceeding the material capability is achieved by a failure function g(X) defined by the difference between the vibratory stress and Goodman line or surface such that the probability of HCF failure is P(f) = P(g(X&lt;0)). The framework can be used to facilitate the development design tools for the prediction of inspection schedules and reliability in aeroengine components. Such tools could lead ultimately to improved life extension schemes in aging aircraft, and more reliable methods for the design and inspection of critical components.
Failure by Fatigue and Stress Rupture in Fiber-Reinforced Composites
Authors: Curtin W. A. 
Published: November 2021

Abstract
Composite durability under conditions where the material survives the initial application of load but then deteriorates with time is a major issue in most engineering applications of composites. The degradation can be caused by the propagation of many damage modes: delamination, matrix cracking, interface degradation, creep, and fiber degradation, among others. In many situations, ultimate and total failure is associated with failure of the fiber bundle supporting the dominant portion of the applied load. Here, the lifetime of a composite due to fiber degradation is investigated for two important modes of fiber degradation: fatigue crack growth under cyclic loading and slow crack growth under stress rupture conditions of constant load. In both cases, individual fiber failure is caused by the growth of pre-existing cracks to a critical size via fatigue or rupture, which is modeled here by a Paris law. A simulation model is used to determine the time-dependent stresses on a bundle of uniaxial brittle fibers, each containing an initial distribution of cracks corresponding to a Weibull strength distribution. As individual fibers fail, their stresses are transferred to nearby fibers, which increases the rate of degradation of the nearby fibers. The damage evolution thus accelerates locally, culminating in the very rapid growth of damage across the entire specimen at the failure time. The average failure time for a set of nominally identical specimens is primarily a function of the fiber Weibull modulus, the Paris law exponent in the fatigue or rupture model, the initial fiber strength, and the rate coefficient of the Paris law. Guidance for the major dependencies of the failure time is obtained by considering an analogous “Global Load Sharing” (GLS) model in which broken fibers transfer load equally to all remaining fibers in the same cross-section. The statistical distribution of failure times at fixed composite size and the size scaling of the mean failure time with increasing size, neither of which can be obtained from the GLS model, are presented and discussed.
Time-Dependent Reliability of Ceramic Components Under Transient Loads
Authors: Jadaan Osama , Nemeth Noel , Powers Lynn , Palko Joe , Baker Eric 
Published: November 2021

Abstract
Present capabilities of the NASA CARES/Life code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code has the capability to compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth (SCG) type failure conditions CARES/Life can handle the cases of sustained and linearly increasing time-dependent loads, while for cyclic fatigue applications various types of repetitive constant amplitude loads can be accounted for. In real applications applied loads are rarely that simple, but rather vary with time in more complex ways such as, for example, engine start up, shut down, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. The objective of this paper is to demonstrate a methodology capable of predicting the time-dependent reliability of components subjected to transient thermomechanical loads that takes into account the change in material response with time. In this paper, the dominant delayed failure mechanism is assumed to be SCG. This methodology has been coded into CARES/Life, which has also been modified to have the capability of interfacing with commercially available FEA codes executed for transient load histories. An example involving a ceramic exhaust valve subjected to combustion cycle loads is presented to demonstrate the viability of this methodology and the CARES/Life program.
Fatigue Reliability Under Corrosion, Creep, and Fretting Damage
Authors: Mahadevan Sankaran 
Published: November 2021

Abstract
This paper presents probabilistic methodologies being developed at Vanderbilt University for the reliability analysis of aging structures. Several deterioration mechanisms such as fatigue, corrosion, creep, and fretting are considered, and probabilistic models are developed. Interactions between the different mechanisms are considered. The effects of various uncertain parameters on the overall life prediction estimates are quantified.
The fatigue damage process induced by pitting corrosion in aging aircraft is composed of seven stages: pitting nucleation, pit growth, transition from pit growth to short crack, short crack growth, transition from short crack to long crack, long crack growth and fracture. A comprehensive mechanics-based probabilistic model for pitting corrosion fatigue life prediction by including all the stages is presented. Analytical FORM/SORM methods as well as advanced Monte Carlo simulation methods are implemented with the proposed model, and probabilistic sensitivity analysis and parametric studies are performed.
Fretting fatigue is one of the main mechanisms of the formation of cracks in riveted lap joint assemblies in aging aircraft and can reduce the fatigue life significantly. A macro-mechanics-based probabilistic model is developed to give the quantitative description of crack nucleation life. Fretting conditions in an idealized, cyclic-loaded pinned connection having dimensions typical of riveted panels are studied. ANSYS finite element analysis is applied to provide the stress, displacement and strain fields in the neighborhood of the contacts between the panel and pin.
Creep is one of the principal damage mechanisms for materials operating at elevated temperatures, such as in aircraft and space propulsion engines. It can produce larger strain deformation, stress relaxation, and crack initiation and growth. Current creep-fatigue life prediction methods use a code-specified bilinear model that has several uncertainties and assumptions regarding material behavior. A new continuous creep-fatigue failure criterion function is introduced directly based on experimental data to facilitate analytical reliability approximations. Such a model is advantageous for new high performance materials where previous experience is limited. A linear damage accumulation rule is used. The use of analytical and simulation methods for reliability analysis with the proposed model is investigated. The effects of the scatter and distributions of different random variables on the creep-fatigue life are studied.
This study is supported by funds from the National Science Foundation.
Challenges and Opportunities for Prime Reliant Thermal Barrier Coating Systems
Authors: Evans Anthony G. 
Published: November 2021

Abstract
Thermal protection systems based on thermal barrier coatings are widely used in turbine engines for propulsion and power generation. They commonly comprise oxide thermal barriers coatings (TBCs) deposited on an intermetallic bond coat (BC), and provide simultaneous thermal and oxidation protection. The benefit of these coatings resides in their ability to inhibit degradation of the underlying structural superalloy component by thermo-mechanical fatigue and oxidation. Existing commercial coatings are well-engineered with established durability and cost benefits. However, they lose adhesion and spall from the underlying metal with cyclic thermal exposure. Because coating failure occurs in a stochastic manner, with no assured cyclic life, the coatings cannot be used in a prime-reliant manner. Prime reliability is only achievable if a high level of basic understanding is gained about failure mechanisms, and material responses, that arise upon thermal cycling. Because of differing manufacturing approaches and operating scenarios, several specific mechanisms are involved. Present understanding of these phenomena has highlighted several nuances and challenges in developing thermal barrier coatings for use as prime-reliant components. This talk will review the current understanding of factors affecting coating durability and presents relationships between the durability, the governing material properties and the salient morphological features. The durability of thermal barrier coatings is governed by a sequence of crack nucleation, propagation and coalescence events that accumulate prior to final failure by large scale buckling and spalling.
Processing and Microstructure Evolution in EB-PVD TBCs
Authors: Terry Scott G. , Cho Junghyun , Levi Carlos G. 
Published: November 2021

Abstract
The connection between processing and performance in thermal barrier coatings produced by electron-beam physical-vapor-deposition is not well understood. A significant component of the problem is the limited understanding of the role that microstructure (including defects) plays in this connection, and the relationships between microstructure and process parameters. This presentation will review recent work aimed at understanding these relationships. The focus will be on the evolution of porosity within the TBC, which is of paramount importance to both thermal conductivity and strain tolerance. Porosity is a result of shadowing processes in the presence of insufficient surface diffusion, and thus deposition temperature and vapor incidence pattern are major parameters. The presentation will highlight the interplay between vapor flux and surface topography, illustrating the relevant phenomena with experimental and modeling results. (Work sponsored by ONR under Grant N00014-99-1-0471 and the UC-LANL Collaborative Research Program.)
Degradation of the Mechanical Properties of Aluminide Coatings as a Result of Thermal Cycling
Authors: Walter Mark , Kim Hyungjun 
Published: November 2021

Abstract
Thermal barrier coatings (TBCs) are typically composed of a ceramic top coat, a thermally grown oxide, and an aluminide bond coat. These three layers each have specific roles in protecting super alloy substrates. State-of-the-art TBCs use Zirconia for the ceramic top coat and develop Alumina thermally grown oxide. Although the bond coats almost universally contain aluminides, their composition and processing vary greatly. In this work, a platinum aluminide bond coat system which was processed using an unactivated pack cementation process is studied. This bond coat system was formed on 1 inch diameter CMSX-4 super alloy disks.
Optimization and Process Control for High Performance Thermal Spray Coatings
Authors: Moreau Christian , Leblanc Luc 
Published: November 2021

Abstract
Thermal spray coatings are used to protect surfaces against exposure to severe conditions. To insure a reliable protection, not only the structure and properties of the sprayed coatings must be optimized but also one needs to develop appropriate process control techniques to produce high performance coatings in a consistent manner, day after day. This is particularly important during plasma spraying as the wear of the electrodes affects significantly the plasma characteristics and consequently the coating properties. First, in this paper, the stability of plasma spray processes is investigated by monitoring in-flight particle characteristics and plasma fluctuations. Secondly, the possibility and advantages of controlling plasma spray processes by monitoring and regulating the condition of the sprayed particles are discussed. Finally, we will see how the properties of thermal barrier coatings and wear resistant coatings can be optimized by controlling the temperature and velocity of the sprayed particles both in the plasma spray and HVOF (high velocity oxy-fuel) processes.
The Functional Performance of Poly Methylmethacrylate Orthopaedic Bone Cement
Authors: Prendergast Patrick J. 
Published: November 2021

Abstract
Materials for fixation of load-bearing implants in the human body should be able to sustain a cyclic load of variable magnitude over an extended period over the remaining lifetime of the parient. A material commonly used for fixation of orthopaedic, dental, and maxillofacial implants is a polymer poly methylmethacrylate (PMMA). However, PMMA does not ideally fulfill this criterion because it undergoes damage accumulation and creep under cyclic loading. This leads to implant loosening and the need for a revision operation.
Fundamental Characteristics of Viscoelastic Fluids Simulated by a Bead-Spring-Damper Macro Model With Interaction
Authors: Ishikawa Takuji , Kawabata Nobuyoshi , Fujita Katsushi , Miyake Yutaka 
Published: November 2021

Abstract
The flow field of viscoelastic fluids is commonly analyzed by using constitutive equations. In this paper, a bead-spring-damper macro model with interaction is proposed as an alternative to analyze a viscoelastic flow. A tetrahedral structure of beads and springs models a gathering of intertwined polymer chains. Behavior of the macro model and the cluster is computed under a simple shear flow condition. Shear-thinning of viscosity, the mechanism of generation of normal stress differences and the effect of slip in the interaction are investigated. The results show that the elongation of clusters to the x direction is the mechanism of the normal stress differences generation, and that the slip in the interaction weakens the stresses. Consequently, it is found that the bead-spring-damper macro model can express the behavior of polymer chains in viscoelastic fluids and basic characteristics of viscoelastic fluids without using constitutive equations.
Evolution of the Late Cretaceous Nanaimo Basin, British Columbia, Canada: Definitive provenance links to northern latitudes
Authors: Mahoney J. Brian , Haggart James W. , Grove Marty , Kimbrough David L. , Isava Virginia , Link Paul K. , Pecha Mark E. , Fanning C. Mark 
Published: November 2021

AbstractAccurate reconstruction of the Late Cretaceous paleogeography and tectonic evolution of the western North American Cordilleran margin is required to resolve the long-standing debate over proposed large-scale, orogen-parallel terrane translation. The Nanaimo Basin (British Columbia, Canada) contains a high-fidelity record of orogenic exhumation and basin subsidence in the southwestern Canadian Cordillera that constrains the tectonic evolution of the region. Integration of detrital zircon U-Pb geochronology, conglomerate clast U-Pb geochronology, detrital muscovite 40Ar/39Ar thermochronology, and Lu-Hf isotopic analysis of detrital zircon defines a multidisciplinary provenance signature that provides a definitive linkage with sediment source regions north of the Sierra Nevada arc system (western United States).Analysis of spatial and temporal provenance variations within Nanaimo Group strata documents a bimodal sediment supply with a local source derived from the adjacent magmatic arc in the southern Coast Mountains batholith and an extra-regional source from the Mesoproterozoic Belt Supergroup and the Late Cretaceous Atlanta lobe of the Idaho batholith. Particularly robust linkages include: (1) juvenile (εHf &gt;+10) Late Cretaceous zircon derived from the southern Coast Mountains batholith; (2) a bimodal Proterozoic detrital zircon signature consistent with derivation from Belt Supergroup (1700–1720 Ma) and ca. 1380 Ma plutonic rocks intruding the Lemhi subbasin of central Idaho (northwestern United States); (3) quartzite clasts that are statistical matches for Mesoproterozoic and Cambrian strata in Montana and Idaho (northwestern United States) and southern British Columbia; and (4) syndepositional evolved (εHf &gt;−10) Late Cretaceous zircon and muscovite derived from the Atlanta lobe of the Idaho batholith. These provenance constraints support a tectonic restoration of the Nanaimo Basin, the southern Coast Mountains batholith, and Wrangellia to a position outboard of the Idaho batholith in Late Cretaceous time, consistent with proposed minimal- fault- offset models (&lt;~1000 km).
Prospective cohort study to evaluate the accuracy of sleep measurement by consumer-grade smart devices compared with polysomnography in a sleep disorders population
Authors: Ellender Claire M , Zahir Syeda Farah , Meaklim Hailey , Joyce Rosemarie , Cunnington David , Swieca John 
Published: November 2021

ObjectivesConsumer-grade smart devices are now commonly used by the public to measure waking activity and sleep. However, the ability of these devices to accurately measure sleep in clinical populations warrants more examination. The aim of the present study was to assess the accuracy of three consumer-grade sleep monitors compared with gold standard polysomnography (PSG).DesignA prospective cohort study was performed.SettingAdults undergoing PSG for investigation of a suspected sleep disorder.Participants54 sleep-clinic patients were assessed using three consumer-grade sleep monitors (Jawbone UP3, ResMed S+ and Beddit) in addition to PSG.OutcomesJawbone UP3, ResMed S+ and Beddit were compared with gold standard in-laboratory PSG on four major sleep parameters—total sleep time (TST), sleep onset latency (SOL), wake after sleep onset (WASO) and sleep efficiency (SE).ResultsThe accelerometer Jawbone UP3 was found to overestimate TST by 28 min (limits of agreement, LOA=−100.23 to 157.37), with reasonable agreement compared with gold standard for TST, WASO and SE. The doppler radar ResMed S+ device underestimated TST by 34 min (LOA=−257.06 to 188.34) and had poor absolute agreement compared with PSG for TST, SOL and SE. The mattress device, Beddit underestimated TST by 53 min (LOA=−238.79 to 132) on average and poor reliability compared with PSG for all measures except TST. High device synchronisation failure occurred, with 20% of recordings incomplete due to Bluetooth drop out and recording loss.ConclusionPoor to moderate agreement was found between PSG and each of the tested devices, however, Jawbone UP3 had relatively better absolute agreement than other devices in sleep measurements compared with PSG. Consumer grade devices assessed do not have strong enough agreement with gold standard measurement to replace clinical evaluation and PSG sleep testing. The models tested here have been superseded and newer models may have increase accuracy and thus potentially powerful patient engagement tools for long-term sleep measurement.
What are the needs and preferences of patients and family members discharged from the emergency department within 24 hours? A qualitative study towards a family-centred approach
Authors: Østervang Christina , Lassen Annmarie Touborg , Jensen Charlotte Myhre , Coyne Elisabeth , Dieperink Karin Brochstedt 
Published: November 2021

ObjectiveThere is an increase in patients being discharged after short stays in the emergency department, but there is limited knowledge of their perspectives on treatment and care. This study aims to explore and understand the needs and preferences of emergency care from the perspective of patients and family members discharged from the emergency department within 24 hours of admission.DesignThe study reports from the first phase in an overall participatory design project. Systematic text condensation was used to identify key themes from field observations and interviews with patients and family members.SettingThis study was conducted in two emergency departments in the Region of Southern Denmark.ParticipantsAll adults aged ≥18 years who had been discharged from the emergency department within 24 hours were eligible to take part. Purposeful sampling was used to recruit patients and family members with different sociodemographic features.ResultsField observational studies (n=50 hours), individual interviews with patients (N=19) and family members (N=3), and joint interviews with patients and family members (N=4) were carried out. Four themes were derived from the material: (1) being in a vulnerable place—having emotional concerns; (2) having a need for person-centred information; (3) the atmosphere in the emergency department and (4) implications of family presence.ConclusionThis study demonstrates a gap between patients’ and family members’ needs and preferences and what current emergency departments deliver. The findings highlight the importance of family and person-centred care. Tailored communication and information with genuine involvement of family members is found to be essential needs during acute illness.
Nurse staffing and patient-perceived quality of nursing care: a cross-sectional analysis of survey and administrative data in German hospitals
Authors: Winter Vera , Dietermann Karina , Schneider Udo , Schreyögg Jonas 
Published: November 2021

ObjectiveTo examine the impact of nurse staffing on patient-perceived quality of nursing care. We differentiate nurse staffing levels and nursing skill mix as two facets of nurse staffing and use a multidimensional instrument for patient-perceived quality of nursing care. We investigate non-linear and interaction effects.SettingThe study setting was 3458 hospital units in 1017 hospitals in Germany.ParticipantsWe contacted 212 554 patients discharged from non-paediatric, non-intensive and non-psychiatric hospital units who stayed at least two nights in the hospital between January and October 2019. Of those, 30 174 responded, yielding a response rate of 14.2%. Our sample included only those patients. After excluding extreme values for our nurse staffing variables and removing observations with missing values, our final sample comprised 28 136 patients ranging from 18 to 97 years of age (average: 61.12 years) who had been discharged from 3458 distinct hospital units in 1017 hospitals.Primary and secondary outcome measuresPatient-perceived quality of nursing care (general nursing care, guidance provided by nurses, and patient loyalty to the hospital).ResultsFor all three dimensions of patient-perceived quality of nursing care, we found that they significantly decreased as (1) nurse staffing levels decreased (with decreasing marginal effects) and (2) the proportion of assistant nurses in a hospital unit increased. The association between nurse staffing levels and quality of nursing care was more pronounced among patients who were less clinically complex, were admitted to smaller hospitals or were admitted to medical units.ConclusionsOur results indicate that, in addition to nurse staffing levels, nursing skill mix is crucial for providing the best possible quality of nursing care from the patient perspective and both should be considered when designing policies such as minimum staffing regulations to improve the quality of nursing care in hospitals.