Lifetime Calculations Research Articles

Lifetime extension of gears and main bearings in wind turbines, scientific calculations and practical implementation

REWITEC, as a part of Cargill Bioindustrial, is a developer and manufacturer of an innovative particle-based surface treatment phyllosilicate-technology for increasing the reliability and the lifetime of wind turbine gears and bearings. The active particles are compatible to all common oils and greases and use lubricants as a carrier to build through their adsorption a protective and repairing phyllosilicate-based coating on the surface. The modified surface has a significantly lower surface roughness, which ensures a better load distribution, lower local pressure and lower tribological stress. Additionally, due to the special layered material structure the particles can be sheared in the tribological contact, which leads to a reduction in friction. All in all, when applying the products systems can run better with reduced friction, wear, surface roughness and temperature. These effects lead to higher reliability and a longer lifetime and thus to cost savings for operators. We would like to show our new scientific study about the lifetime calculation of a grease-lubricated wind turbine main bearing (1.5 MW) with and without the use of technology. The project is a cooperation between REWITEC and Sentient Science who performs lifetime calculations using digital clone method based on real friction coefficient and surface roughness data. The project includes data generation using MTM test bench, in a wind turbine bearing and subsequent simulation based on this data and bearing geometry. The simulation shows that with REWITEC the probability for a bearing failure significantly decreases which leads to a lifetime extension of up to 17.3 years.

BIM-centred building diagnoses as a decision support tool for maintenance and repair

Digitalization in the construction industry continues to advance and, together with the increasing dissemination and further development of hardware and software, is steadily opening up further opportunities for innovative ways of working. Building Information Modeling (BIM) is currently becoming the standard for new construction, but has not yet been optimized for use in existing buildings. Therefore, the Institute of Building Materials Research at RWTH Aachen University (ibac) is researching new methods and possibilities for BIM-based building preservation. In this paper, the vision of digitalized building preservation, the state of research so far and the planned further steps are presented. It highlights what information needs to be available in the BIM model for digitalized maintenance planning, and shows how this data can be implemented in a way that is machine-readable and suitable for automated evaluation. The goal is the digital availability and linking of all inspection results, so that various operations such as lifetime prognoses or calculation of concrete removal can be performed in the BIM model. The findings to date show that making BIM models usable beyond the planning and execution phase is an essential step for the digitalization of building maintenance and holds great potential for effective building diagnoses and efficient service life management.

Prospects for Neutron Reactions on Excited States in High-Density Plasmas

With the reactions of high flux neutrons, such as in a DT plasma, there is a prospect of seeing new kinds of neutron-nucleus reactions for the first time. If neutrons excite a heavy nucleus, for example, there is possibility of a second neutron reacting on excited states of the residual nucleus before that nucleus has de-excited to its ground state. The possibility of such reactions on excited states has rarely been considered. The cross section for neutron induced fission on the isomeric state of 235U has been measured (D’Eer et al., Phys. Rev. C, 1988, 38: 1270–1276) and calculated (Younes et al., 2003, Maslov, 2007), and reactions on rotationally excited nuclear states has been calculated (Kawano et al., Phys. Rev. C, 2009, 80: 024611). In high flux plasmas, however, a much wider range of reactions is possible. We therefore need to consider excited states at much higher-energies than previously modeled, and then estimate whether second neutrons are likely to rescatter on those excited states. To determine the likelihood of such rescattering events, we first need to know the probable time series of nuclear decays of those excited states. The lifetimes of many low-lying states have been measured experimentally, but now we need to know the lifetimes of the many higher excited states that could be produced from incident 14 MeV neutrons. These are too numerous to be measured and also too numerous to be calculated individually, so statistical Hauser-Feshbach decay models are used. I show some lifetime calculations for 89Y, 169Tm, and 197Au targets, and predictions for the number of rescattering events in plausible plasma scenarios.

Modeling and X-ray Analysis of Defect Nanoclusters Formation in B4C under Ion Irradiation.

In the presented work, B4C was irradiated with xenon swift heavy ions at the energy of 167 MeV. The irradiation of the substrate was done at room temperature to a fluence of 3.83 × 1014 ion/cm2. The samples were then analyzed with the X-ray diffraction technique to study the structural modification, as it can probe the region of penetration of xenon atoms due to the low atomic number of the two elements involved in the material under study. The nano-cluster formation under ion irradiation was observed. Positron lifetime (PLT) calculations of the secondary point defects forming nanoclusters and introduced into the B4C substrate by hydrogen and helium implantation were also carried out with the Multigrid instead of the K-spAce (MIKA) simulation package. The X-ray diffraction results confirmed that the sample was B4C and it had a rhombohedral crystal structure. The X-ray diffraction indicated an increase in the lattice parameter due to the Swift heavy ion (SHI) irradiation. In B12-CCC, the difference between τ with the saturation of H or He in the defect is nearly 20 ps. Under the same conditions with B11C-CBC, there is approximately twice the value for the same deviation.

Three Dimensional Lifetime-Multiplex Tomography Based on Time-Gated Capturing of Near-Infrared Fluorescence Images

We report a computed tomography (CT) technique for mapping near-infrared fluorescence (NIRF) lifetime as a multiplex three-dimensional (3D) imaging method, using a conventional NIR camera. This method is achieved by using a time-gated system composed of a pulsed laser and an NIR camera synchronized with a rotatable sample stage for NIRF-CT imaging. The fluorescence lifetimes in microsecond-order of lanthanides were mapped on reconstructed cross-sectional and 3D images, via back-projection of two-dimensional projected images acquired from multiple angles at each time point showing fluorescence decay. A method to select slopes (the observed decay rates in time-gated imaging) used for the lifetime calculation, termed as the slope comparison method, was developed for the accurate calculation of each pixel, resulting in reduction of image acquisition time. Time-gated NIRF-CT provides a novel choice for multiplex 3D observation of deep tissues in biology.

Einfluss von Eiskollisionslasten am Propeller auf die Kontaktzustände in den Antriebsstranggleitlagern von Schiffen

Journal bearings in drive trains of ships in Arctic and Antarctic operations show wear and fatigue damage resulting from collision between the propeller and drift ice. The damage requires costly drivetrain maintenance in dry dock, which can be reduced by loadappropriate design and predictive maintenance measures However, this requires a reliable life time calculation of marine drive train bearings subjected to stochastic ice loads. In the following investigations, the influence of different load characteristics of a propeller-ice collision on the contact states in the drive train bearings of ships is investigated in order to be able to estimate the influence of different load characteristics in terms of the development of future life time models. For the investigations, a MBD and EHD model of the drive train of the research vessel SA Agulhas II was built. The results show that the load characteristics “load duration”, “load height” and “load orientation” and the operating parameter “oil temperature” have a high influence on the contact states in the drive train bearings and must be taken into account for future life time calculations.

Оценка долговечности и рациональное крепление кожуха зубчатой передачи к тяговому двигателю электровоза

Purpose: To investigate the dependence of workload of an electric locomotive gear housing on the parameters of its attachment to a traction motor. To determine own oscillation frequencies under various conditions of its attachment to a traction motor. To propose technical solution allowing to reduce the workload of gear housing in the case of abnormal operation of its attachment to a traction motor. To propose an algorithm for housing lifetime calculation taking into account its fastening parameters. Methods: The values of gear housing own frequencies are obtained by solving the system of Lagrange differential equations of the second kind. Created with this purpose mathematical model of mechanical system under consideration takes into account an elastic nature of housing attachment to a traction motor. Results: The influence of conditions and parameters of gear housing attachment to a traction motor on its workload and, correspondingly, its lifetime is shown. The algorithm for gear housing lifetime calculation is proposed, taking into account its fastening conditions and parameters. The significant influence of workload abnormal modes on housing durability is shown. Practical importance: Constructive solution is proposed that reduces gear housing workload in the case of abnormal conditions of attachment to a traction motor. The algorithm for estimating gear housing durability in the case of redistribution of workloads between its reference points has been developed.

Silver nanoparticles embedded sulfur doped graphitic carbon nitride quantum dots: A fluorescent nanosensor for detection of mercury ions in aqueous media

Graphitic carbon nitride (gCN) quantum dots, in recent years, have captivated enormous attention in the field of sensing due to their unique optical and electronic properties. We have reported a facile synthesis of silver nanoparticles (AgNPs) embedded sulfur-doped gCN quantum dots (Ag-S-gCN QDs) using thiourea, trisodium citrate, and silver nitrate precursors. The as-prepared quantum dots with an average particle size of 3.7 nm emitted strong blue fluorescence with a relative quantum yield of 36.5%. They exhibited significant stability against photobleaching and high ionic strength. The Ag-S-gCN QDs, under optimal conditions, were employed for fast sensing of Hg2+ ions in 3 min at pH 5. The limit of detection (LOD) and limit of quantification (LOQ) were measured to be 0.13 μM and 0.43 μM, respectively, with a linear range of 0.1–0.6 μM. The average lifetime of Ag-S-gCN QDs was calculated as 7.79 ns from a time-resolved decay experiment. A static quenching mechanism was proposed from the average lifetime calculation accompanied by a redox reaction via electron transfer from metallic Ag to Hg2+ ions. A substantial amount (>85%) of Hg2+ ions in the real water samples were recovered within a relative standard deviation (RSD) of ≤ 5%. The proposed nanosensor was anticipated to open up a new avenue for convenient, efficient, sensitive, and selective sensing of potentially hazardous Hg2+ ions.

Characterization of lattice distortions in refractory metal complex concentrated alloys using positron annihilation spectroscopy

Severe distortions of crystalline lattice represent an inherent feature of complex concentrated alloys (CCAs). Lattice distortions are caused by atomic size differences of alloy constituent ions which are distributed randomly over the lattice sites. It is believed that lattice distortions play the key role in extraordinary properties of CCAs. However, characterization of lattice distortions is difficult since they occur on the atomic scale and have a stochastic nature. In the present work we employ positron annihilation spectroscopy for characterization of lattice distortions in series of 18 refractory metal CCAs with the bcc structure. Our study revealed that the bulk positron lifetime increases with increasing magnitude of lattice distortions. It indicates that positron delocalized in the lattice can be used as a probe of lattice distortions in CCAs since it is located with higher probability in interstitial regions with extended open volume. This experimental observation is supported by theoretical calculations of positron lifetimes in CCAs. Moreover, it was confirmed that lattice distortions cause strengthening of CCAs.

Operations expenditure modelling of the X-Rotor offshore wind turbine concept

O&M of an offshore wind farm is becoming increasingly challenging as farms are being commissioned further from shore. Weather windows are more difficult to navigate leading to longer downtime for turbines. The X-Rotor offshore wind turbine concept directly tackles these O&M challenges by, amongst other advantages, removing the requirements for components that have traditionally contributed high failure rates, repair times and downtimes, and by placing the heavy and expensive machinery closer to sea level. The turbine also benefits from having modular small rotors that can be quickly replaced and repaired onshore, and being able to operate at reduced capacity when there are failures in the modular rotors. This paper presents the StrathX-OM OpEx model. This model features changes to OpEx modelling that will allow for comprehensive analysis of the operations and maintenance costs for a wind farm made up of radical X-Rotor wind turbines with the flexibility to handle changing designs as the technology progresses. The calculation of lifetime O&M costs for a wind farm 100 km from shore showed that the X-Rotor has lower O&M costs than conventional HAWTs for an established design. A sensitivity study on the estimated failure rates of X-Rotor is also presented. This shows that even with significantly over-estimated failure rates the X-Rotor would still be competitive in today’s market.

A Cross-Layer Design and Fuzzy Logic based Stability Oriented Routing Protocol

Ad-hoc networks in which nodes are mobile as well as communicate via wireless links fall under the category of mobile ad-hoc networks (MANETs). Evasive mobility and the limited battery life of MANET nodes make routing a difficult problem. Most of the conventional routing protocols recommend the shortest path without considering route stability into account. A Cross-Layer Design and Fuzzy Logic based Stability Oriented (CLDFL-SO) routing protocol is proposed in this research, which offers a solution for stable route formation by eliminating unstable links and low-quality nodes. Cross-layer interaction parameter based link residual lifetime calculation is used to assess the link's stability. The fuzzy logic is being used to evaluate the node quality by providing node metrics like node speed, residual energy and node degree. The simulations illustrate the efficacy of the suggested protocol in comparison to the popular Ad-hoc On-Demand Distance Vector (AODV) protocol.

A novel Cd (II) coordination polymer of highly sensitive sensing for antibiotics in aqueous medium

A novel Cd(II) coordination polymer (CP) {[Cd(H2DOBPDC2-)(bpd)]·H2O}n (1) has been synthesized by a rigid polycarboxylic acid with hydroxyl groups (H4DOBPDC = 4,4′- dihydroxy-[1,1′-biphenyl-3,3′-dicarboxylic acid]). Structure analysis displayed that CP 1 shows a 3D supramolecular structure through hydrogen bonding. In addition, fluorescence experiments confirmed 1 can sensitively and selectively detect NFT in aqueous medium with limit of detection of 3.67 × 10-6 M. Meanwhile, the detection mechanism of 1 toward NFT was also investigated by the experiments of PXRD, UV–vis spectrum and fluorescent lifetime and Density Functional Theory (DFT) calculation in detail.

Calculation of Minority Carriers’ Lifetime in HgCdTe Structures by Using the Method Based on Mutual Correlation Between the Concentration of Electrical Particles

We perform a theoretical study of the bulk generation-recombination mechanisms, and the carrier lifetime in n- and p-type long- and mid-wavelength infrared HgCdTe structures at liquid nitrogen (LN) temperature has been done. This article is a continuation of our previous work and presents a method for calculating the excess minority carrier lifetime considering the mutual correlation between the concentration of electrons, holes, ionized impurities, and trap states resulting from the principle of charge conservation. It has been shown that recombination involving shallow impurity states in HgCdTe structures with low intrinsic concentration has a significant impact on minority carriers’ lifetime. This applies to both p- and n-type materials. The results of calculations of the carrier lifetime determined by the interband processes: radiative, Auger 1 and 7, recombination involving impurities, as well as and Shockley–Read–Hall (SRH) mechanisms related to mercury vacancies have been compared with experimental data presented by other authors. By analyzing the published calculations made by American researchers, the values of the overlap integrals <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert {F}_{1}{F}_{2} \vert $ </tex-math></inline-formula> for Auger processes were determined, which allowed to obtain a good compliance of our calculations with the experimental values. In this article, the cross sections for SRH recombination with the participation of mercury vacancies were estimated. These values are lower than those previously presented by other researchers. By verifying the results of the calculations with the experimental data, we confirmed the effectiveness of the proposed method.

Устойчивость процедуры вычисления радиационных времен жизни

Purpose: Radiation lifetimes of atom and ion energy levels refer to fundamental physical constants which knowledge of is necessary in many fields of both, fundamental or applied science. The knowledge of these values is necessary at search of active medias for optical generators, for plasma both laboratory or astrophysical and other diagnostics. While lifetime calculation, it’s very vital to evaluate the impact of simplifications and supposition, put on the basis of calculation procedure. In particular, to evaluate impact of configuration superposition which consideration significantly complicates calculation model. The present work investigates this issue on a particular example of spectrum of sixfold wolfram ion W VII. Methods: Superposition of configurations 4f 13 5p6 6p + 4f 14 5p5 6p in the spectrum of erbium-similar W VII is investigated by semiempirical method of intermediate coupling with the use of energy experimental levels known from the literature. Together, wave functions of intermediate binding of odd configurations have been found in a single-configuration approximation; radial integrals, that’re necessary for transfer to absolute scale of transition probabilities, are calculated in the form of length with Hartree-Fock functions. Lifetimes of 4f 135p66p levels are calculated by summarizing electric dipole transition probabilities 4f 13 5p6 6p+ 4f 14 5p5 6p → 4f 13 5p65d, 4f 13 5p66s. Results: It’s been obtained that configuration essential mixing takes place for states with total angular momentum J = 3. Values of level lifetimes have been appeared to be insensitive to influence of configuration mixing. As to author’s opinion, it’s connected with that the lifetimes are defined by the probabilities of the most intensive transitions which in its turn, are the least sensitive to possible inaccuracies in calculation procedure. Practical significance: Values of lifetimes of levels 4f 13 5p6 6p in W VII spectrum, that are absent in contemporary databases at the moment, are practically significant.

Accurate multiconfiguration calculations of energy levels, transition rates, and lifetimes for Kr XXIII

Extensive Multiconfiguration Dirac-Hartree-Fock calculations are performed for the lowest 97 levels belonging to the 3s23p2, 3s3p3, 3s23p3d, 3s3p23d, 3s23d2, and 3p4 configurations in silicon-like Kr XXIII. Complete and consistent data sets of energy levels, transition rates and lifetimes for electric-dipole (E1), electric-quadrupole (E2), magnetic-dipole (M1), and magnetic-quadrupole (M2) transitions among all these levels are given. High-accuracy calculations have been performed with accurate treatment of relativity, electron correlation, and quantum electrodynamic effects, as well as inter-electron correlation. The calculated energy levels are in excellent agreement with available theoretical and experimental data. The present results are reported as benchmarks for future calculations and measurements.

Stress Analysis of the Cylinder Block in an Axial Piston Pump

For axial piston units, product optimisation plays an essential role in the development phase, where an efficient and price-attractive product design and manufacturing process is the key to the success of a product. Moreover, the market needs are on lighter, more compact, efficient, and reliable products designed to the limit. Therefore, reliability is the focus of this work, where the research includes method analysis of the material stress calculation applied to the cylinder block implemented in an axial piston pump. A simplified calculation model is presented and evaluated concerning load while remaining accessible for users without deep technical knowledge or access to expensive Finite Element (FE) simulation tools. The analytical calculation method delivers a stress distribution intended for different purposes like design evaluation or as load spectrum for lifetime calculation. Additionally, the developed calculation method is generalised, enabling the methodology to be used on any standard axial piston pump. The methodology utilises the stress determination model, which includes the load as a sum of forces caused by the external and internal influencing factors. To show the method’s success, a comparison demonstrates strong positive agreement between the calculated and simulated stress results obtained by Finite Element Analysis.

Graphene compared to fluorine-doped tin oxide as transparent conductor in ZnO dye-sensitized solar cells

Graphene could replace widely used transparent conductors (TC) like tin oxides due to its high transparency and electrical conductivity. This work focuses on the technical feasibility of graphene produced by chemical vapor deposition (CVD) to replace tin oxides in the photoanode of dye-sensitized solar cells (DSSCs). This is the first study in which graphene is used as photoanode TC in a tin oxide-free DSSC with ZnO as mesoporous semiconductor. The stability of graphene towards hybridization with ZnO was investigated using electrical measurements and Raman spectroscopy. A thorough comparison of performance between FTO- and graphene-DSSCs fabricated with otherwise identical methods was performed with linear voltammetry, electrochemical impedance spectroscopy and electron lifetime calculations. The higher optical transmittance of graphene resulted in larger open circuit voltage and short circuit current density than FTO devices. However, the larger sheet resistance of graphene caused a lower fill factor in the graphene-DSSCs. Graphene- and FTO-DSSCs yielded similar power conversion efficiencies of 0.4%, despite graphene being ∼250 times thinner than FTO. The findings have important cost and environmental implications for large scale production, not only for DSSCs, but for the photovoltaic technologies derived from them, such as perovskites and quantum dot-SSCs, and other photoelectrochemical devices. Tin oxides replacement with graphene is promising for development of lighter, and more flexible, sustainable and resilient PV technology.

Room-Temperature Persistent Luminescence in Metal Halide Perovskite Nanocrystals for Solar-Driven CO 2 Bioreduction

Room-Temperature Persistent Luminescence in Metal Halide Perovskite Nanocrystals for Solar-Driven CO ₂ Bioreduction

The refined determination of the ion pair lifetimes in ionic liquids

Assessing lifetimes of liquid’s local structures could bring impactful output. For example, the key transport properties of ionic liquids are governed by local structure dynamics to a large extent. Due to long-range Coulomb interactions, these systems show pronounced charge ordering. In this case, the local structure breaking rate could be described in terms of cation–anion pair lifetimes. Conventional pair lifetime analysis relies on geometrical criterion, defining the maximum distance from cation to anion in pair. In this study, we argue towards additional restriction to ensure pair stability. Based on vibrational properties, we introduce lower boundary for pair lifetime to exclude false pair recognition in the case of collision-like interaction. Also, we put forward a computational algorithm which allows obtaining both mean lifetime and lifetime distribution. The calculations of mean pair lifetimes in molten alkali halides support our reasoning.

A comparative study on energy-based fatigue criteria for lifetime calculation of magnetorheological elastomers under multiaxial loading

Predicting fatigue life of magnetorheological elastomers (MREs) containing, different volumes of carbonyl iron particles (CIPs) with various external magnetic fields has been investigated. Unlike many studies on fatigue behavior of MREs, representing experimental models, a novel three-dimensional constitutive magneto-hyper-viscoelastic semi-coupling model based on strain energy density function (3DSED) is derived, analyzing the fatigue of structures enhanced by MRE experimentally and numerically. In this 3DSED model, to obtain the best predicting MREs’ fatigue life, three different hyper-elastic functions, including Neo-Hookean, Mooney-Rivlin, and Yeoh are utilized. Using some uniaxial compression, such as loading phase, relaxation, and loading/unloading phases tests, hyper-elastic, magneto-elastic, and viscoelastic constants are determined. In addition, multi-axial fatigue tests are performed to define the number of cycles to failure. These tests have been induced by the magnetic fields of 0, 0.27, and 0.4 T. The fatigue tests re-performed with the magnetic field of 0.3 T to compare the predicted results using the proposed fatigue models. The results show that the 3DSED model can be used for the prediction of MREs fatigue life when subjected to complex and repetitive loading. For all CIP contents, the Mooney-Rivlin fatigue predictor has more accurate results. The Yeoh fatigue predictor indicates better results for MREs with higher CIP contents, while the Neo-Hookean fatigue predictor doesn’t show acceptable results for any CIP contents.