WorldWideScience

Sample records for wind stress strength

  1. Southern Ocean carbon-wind stress feedback

    Science.gov (United States)

    Bronselaer, Ben; Zanna, Laure; Munday, David R.; Lowe, Jason

    2018-02-01

    The Southern Ocean is the largest sink of anthropogenic carbon in the present-day climate. Here, Southern Ocean pCO2 and its dependence on wind forcing are investigated using an equilibrium mixed layer carbon budget. This budget is used to derive an expression for Southern Ocean pCO2 sensitivity to wind stress. Southern Ocean pCO2 is found to vary as the square root of area-mean wind stress, arising from the dominance of vertical mixing over other processes such as lateral Ekman transport. The expression for pCO2 is validated using idealised coarse-resolution ocean numerical experiments. Additionally, we show that increased (decreased) stratification through surface warming reduces (increases) the sensitivity of the Southern Ocean pCO2 to wind stress. The scaling is then used to estimate the wind-stress induced changes of atmospheric pCO_2 in CMIP5 models using only a handful of parameters. The scaling is further used to model the anthropogenic carbon sink, showing a long-term reversal of the Southern Ocean sink for large wind stress strength.

  2. An Integrated Structural Strength Analysis Method for Spar Type Floating Wind Turbine

    Institute of Scientific and Technical Information of China (English)

    胡志强; 刘毅; 王晋

    2016-01-01

    An integrated structural strength analysis method for a Spar type floating wind turbine is proposed in this paper, and technical issues related to turbine structure modeling and stress combination are also addressed. The NREL-5MW “Hywind” Spar type wind turbine is adopted as study object. Time-domain dynamic coupled simulations are performed by a fully-coupled aero-hydro-servo-elastic tool, FAST, on the purpose of obtaining the dynamic characteristics of the floating wind turbine, and determining parameters for design load cases of finite element calculation. Then design load cases are identified, and finite element analyses are performed for these design load cases. The structural stresses due to wave-induced loads and wind-induced loads are calculated, and then combined to assess the structural strength of the floating wind turbine. The feasibility of the proposed structural strength analysis method for floating wind turbines is then validated.

  3. Dispersive stresses in wind farms

    Science.gov (United States)

    Segalini, Antonio; Braunbehrens, Robert; Hyvarinen, Ann

    2017-11-01

    One of the most famous models of wind farms is provided by the assumption that the farm can be approximated as a horizontally-homogeneous forest canopy with vertically-varying force intensity. By means of this approximation, the flow-motion equations become drastically simpler, as many of the three-dimensional effects are gone. However, the application of the horizontal average operator to the RANS equations leads to the appearance of new transport terms (called dispersive stresses) originating from the horizontal (small-scale) variation of the mean velocity field. Since these terms are related to the individual turbine signature, they are expected to vanish outside the roughness sublayer, providing a definition for the latter. In the present work, an assessment of the dispersive stresses is performed by means of a wake-model approach and through the linearised code ORFEUS developed at KTH. Both approaches are very fast and enable the characterization of a large number of wind-farm layouts. The dispersive stress tensor and its effect on the turbulence closure models are investigated, providing guidelines for those simulations where it is impossible to resolve the farm at a turbine scale due to grid requirements (as, for instance, mesoscale simulations).

  4. Fatigue strength ofcomposite wind turbine blade structures

    DEFF Research Database (Denmark)

    Ardila, Oscar Gerardo Castro

    Wind turbines are normally designed to withstand 20-30 years of life. During this period, the blades, which are the main rotating structures of a wind turbine, are subjected to high fluctuating load conditions as a result of a combination of gravity, inertia, and aeroelastic forces. For this reason......, fatigue is one of the foremost concerns during the design of these structures. However, current standard fatigue methods used for designing wind turbine blades seem not to be completely appropriate for these structures because they are still based on methods developed for metals and not for composite...... materials from which the blades are made. In this sense, the aim of this work is to develop more accurate and reliable fatigue-life prediction models for composite wind turbine blades. In this project, two types of fatigue models are implemented: fatigue-life models and damage mechanics models. In the first...

  5. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Curl

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  6. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  7. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  8. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  9. Shear and Turbulence Estimates for Calculation of Wind Turbine Loads and Responses Under Hurricane Strength Winds

    Science.gov (United States)

    Kosovic, B.; Bryan, G. H.; Haupt, S. E.

    2012-12-01

    Schwartz et al. (2010) recently reported that the total gross energy-generating offshore wind resource in the United States in waters less than 30m deep is approximately 1000 GW. Estimated offshore generating capacity is thus equivalent to the current generating capacity in the United States. Offshore wind power can therefore play important role in electricity production in the United States. However, most of this resource is located along the East Coast of the United States and in the Gulf of Mexico, areas frequently affected by tropical cyclones including hurricanes. Hurricane strength winds, associated shear and turbulence can affect performance and structural integrity of wind turbines. In a recent study Rose et al. (2012) attempted to estimate the risk to offshore wind turbines from hurricane strength winds over a lifetime of a wind farm (i.e. 20 years). According to Rose et al. turbine tower buckling has been observed in typhoons. They concluded that there is "substantial risk that Category 3 and higher hurricanes can destroy half or more of the turbines at some locations." More robust designs including appropriate controls can mitigate the risk of wind turbine damage. To develop such designs good estimates of turbine loads under hurricane strength winds are essential. We use output from a large-eddy simulation of a hurricane to estimate shear and turbulence intensity over first couple of hundred meters above sea surface. We compute power spectra of three velocity components at several distances from the eye of the hurricane. Based on these spectra analytical spectral forms are developed and included in TurbSim, a stochastic inflow turbulence code developed by the National Renewable Energy Laboratory (NREL, http://wind.nrel.gov/designcodes/preprocessors/turbsim/). TurbSim provides a numerical simulation including bursts of coherent turbulence associated with organized turbulent structures. It can generate realistic flow conditions that an operating turbine

  10. Stochastic models for strength of wind turbine blades using tests

    DEFF Research Database (Denmark)

    Toft, H.S.; Sørensen, John Dalsgaard

    2008-01-01

    The structural cost of wind turbine blades is dependent on the values of the partial safety factors which reflect the uncertainties in the design values, including statistical uncertainty from a limited number of tests. This paper presents a probabilistic model for ultimate and fatigue strength...... of wind turbine blades especially considering the influence of prior knowledge and test results and how partial safety factors can be updated when additional full-scale tests are performed. This updating is performed by adopting a probabilistic design basis based on Bayesian statistical methods....

  11. Wireless Concrete Strength Monitoring of Wind Turbine Foundations

    Directory of Open Access Journals (Sweden)

    Marcus Perry

    2017-12-01

    Full Text Available Wind turbine foundations are typically cast in place, leaving the concrete to mature under environmental conditions that vary in time and space. As a result, there is uncertainty around the concrete’s initial performance, and this can encourage both costly over-design and inaccurate prognoses of structural health. Here, we demonstrate the field application of a dense, wireless thermocouple network to monitor the strength development of an onshore, reinforced-concrete wind turbine foundation. Up-to-date methods in fly ash concrete strength and maturity modelling are used to estimate the distribution and evolution of foundation strength over 29 days of curing. Strength estimates are verified by core samples, extracted from the foundation base. In addition, an artificial neural network, trained using temperature data, is exploited to demonstrate that distributed concrete strengths can be estimated for foundations using only sparse thermocouple data. Our techniques provide a practical alternative to computational models, and could assist site operators in making more informed decisions about foundation design, construction, operation and maintenance.

  12. Wireless Concrete Strength Monitoring of Wind Turbine Foundations.

    Science.gov (United States)

    Perry, Marcus; Fusiek, Grzegorz; Niewczas, Pawel; Rubert, Tim; McAlorum, Jack

    2017-12-16

    Wind turbine foundations are typically cast in place, leaving the concrete to mature under environmental conditions that vary in time and space. As a result, there is uncertainty around the concrete's initial performance, and this can encourage both costly over-design and inaccurate prognoses of structural health. Here, we demonstrate the field application of a dense, wireless thermocouple network to monitor the strength development of an onshore, reinforced-concrete wind turbine foundation. Up-to-date methods in fly ash concrete strength and maturity modelling are used to estimate the distribution and evolution of foundation strength over 29 days of curing. Strength estimates are verified by core samples, extracted from the foundation base. In addition, an artificial neural network, trained using temperature data, is exploited to demonstrate that distributed concrete strengths can be estimated for foundations using only sparse thermocouple data. Our techniques provide a practical alternative to computational models, and could assist site operators in making more informed decisions about foundation design, construction, operation and maintenance.

  13. Wind Stress Variability Observed Over Coastal Waters

    Science.gov (United States)

    Ortiz-Suslow, D. G.; Haus, B. K.; Laxague, N.; Williams, N. J.; Graber, H. C.

    2016-02-01

    The wind stress on the ocean surface generates waves, drives currents, and enhances gas exchange; and a significant amount of work has been done to characterize the air-sea momentum flux in terms of bulk oceanographic and atmospheric parameters. However, the majority of this work to develop operational algorithms has been focused on the deep ocean and the suitability of these methods in the coastal regime has not been evaluated. The findings from a two-part field campaign will be presented which highlight the divergence of nearshore wind stress observations from conventional, deep water results. The first set of data comes from a coastal region near a relatively small, natural tidal inlet. A high degree of spatial variability was observed in both the wind stress magnitude and direction, suggestive of coastal processes (e.g., depth-limited wave affects and horizontal current shear) modulating the momentum flux from the atmosphere to the ocean surface. These shallow-water processes are typically not accounted for in conventional parameterizations. Across the experimental domain and for a given wind speed, the stress magnitude was found to be nearly 2.5 times that predicted by conventional methods; also, a high propensity for stress steering off the mean azimuthal wind direction (up to ±70 degrees) was observed and linked to horizontal current gradients produced by the tidal inlet. The preliminary findings from a second data set taken in the vicinity of the macrotidal Columbia River Mouth will also be presented. Compared to the first data set, a similar degree of variability is observed here, but the processes responsible for this are present at a much larger scale. Specifically, the Columbia River Mouth observations were made in the presence of significant swell wave energy and during periods of very high estuarine discharge. The relative angle between the wind and swell direction is expected to be significant with regards to the observed momentum flux. Also, these

  14. Character strengths, social anxiety, and physiological stress reactivity

    Directory of Open Access Journals (Sweden)

    Tingting Li

    2017-05-01

    Full Text Available In this paper, the effects of character strengths on the physiological reactivity to social anxiety induced by the Trier Social Stress Task were reported. On the basis of their scores in the Chinese Virtues Questionnaire, 30 college students were assigned to either high- (n = 15 or low-character-strength (n = 15 groups. Their psychological stress and physiological data across three laboratory stages (namely, baseline, stress exposure, and post-stress were collected. Results indicated that individuals with high character strengths exhibited rapid cardiovascular recovery from baseline to post-stress even if high- and low-character-strength groups showed similar patterns of cardiovascular arousal in response to the stress at baseline and stress exposure. These results prove that character strengths are stress-defense factors that allow for psychological and physiological adaptation to stress.

  15. Ultimate strength of a large wind turbine blade

    DEFF Research Database (Denmark)

    Jensen, Find Mølholt

    2009-01-01

    reinforcements helping to prevent undesired structural elastic mechanisms are presented. The functionality of two of the suggested structural reinforcements was demonstrated in full-scale tests and the rest trough FE-studies. The blade design under investigation consisted of an aerodynamic airfoil and a load...... carrying box girder. In total, five full-scale tests have been performed involving one complete blade and two shortened box girders. The second box girder was submitted to three independent tests covering different structural reinforcement alternatives. The advantages and disadvantages of testing......The present PhD project contains a study of the structural static strength of wind turbine blades loaded in flap-wise direction. A combination of experimental and numerical work has been used to address the most critical failure mechanisms and to get an understanding of the complex structural...

  16. Enhancement of wind stress evaluation method under storm conditions

    Science.gov (United States)

    Chen, Yingjian; Yu, Xiping

    2016-12-01

    Wind stress is an important driving force for many meteorological and oceanographical processes. However, most of the existing methods for evaluation of the wind stress, including various bulk formulas in terms of the wind speed at a given height and formulas relating the roughness height of the sea surface with wind conditions, predict an ever-increasing tendency of the wind stress coefficient as the wind speed increases, which is inconsistent with the field observations under storm conditions. The wave boundary layer model, which is based on the momentum and energy conservation, has the advantage to take into account the physical details of the air-sea interaction process, but is still invalid under storm conditions without a modification. By including the energy dissipation due to the presence of sea spray, which is speculated to be an important aspect of the air-sea interaction under storm conditions, the wave boundary layer model is improved in this study. The improved model is employed to estimate the wind stress caused by an idealized tropical cyclone motion. The computational results show that the wind stress coefficient reaches its maximal value at a wind speed of about 40 m/s and decreases as the wind speed further increases. This is in fairly good agreement with the field data.

  17. Ultimate strength of a large wind turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Moelholt Jensen, Find

    2008-05-15

    The present PhD project contains a study of the structural static strength of wind turbine blades loaded in flap-wise direction. A combination of experimental and numerical work has been used to address the most critical failure mechanisms and to get an understanding of the complex structural behaviour of wind turbine blades. Four failure mechanisms observed during the fullscale tests and the corresponding FE-analysis are presented. Elastic mechanisms associated with failure, such as buckling, localized bending and the Brazier effect, are studied. Six different types of structural reinforcements helping to prevent undesired structural elastic mechanisms are presented. The functionality of two of the suggested structural reinforcements was demonstrated in full-scale tests and the rest trough FE-studies. The blade design under investigation consisted of an aerodynamic airfoil and a load carrying box girder. In total, five full-scale tests have been performed involving one complete blade and two shortened box girders. The second box girder was submitted to three independent tests covering different structural reinforcement alternatives. The advantages and disadvantages of testing a shortened load carrying box girder vs. an entire blade are discussed. Changes in the boundary conditions, loads and additional reinforcements, which were introduced in the box girder tests in order to avoid undesired structural elastic mechanisms, are presented. New and advanced measuring equipment was used in the fullscale tests to detect the critical failure mechanisms and to get an understanding of the complex structural behaviour. Traditionally, displacement sensors and strain gauges in blade tests are arranged based on an assumption of a Bernoulli-Euler beam structural response. In the present study it is shown that when following this procedure important information about distortions of the cross sections is lost. In the tests presented here, one of the aims was to measure distortion

  18. Temporal and spatial patterns in wind stress and wind stress curl over the central Southern California Bight

    Science.gov (United States)

    Noble, Marlene A.; Rosenberger, Kurt J.; Rosenfeld, Leslie K.; Robertson, George L.

    2012-01-01

    In 2001, the U.S. Geological Survey, together with several other federal and municipal agencies, began a series of field programs to determine along and cross-shelf transport patterns over the continental shelves in the central Southern California Bight. As a part of these programs, moorings that monitor winds were deployed off the Palos Verdes peninsula and within San Pedro Bay for six 3–4 month summer and winter periods between 2001 and 2008. In addition, nearly continuous records of winds for this 7-year period were obtained from a terrestrial site at the coast and from a basin site offshore of the long-term coastal site. The mean annual winds are downcoast at all sites. The alongshelf components of wind stress, which are the largest part of the low-frequency wind stress fields, are well correlated between basin, shelf and coastal sites. On average, the amplitude of alongshelf fluctuations in wind stress are 3–4 times larger over the offshore basin, compared to the coastal site, irrespective of whether the fluctuations represent the total, or just the correlated portion of the wind stress field. The curl in the large-scale wind stress tends to be positive, especially in the winter season when the mean wind stress is downcoast and larger at the offshore basin site than at the beach. However, since the fluctuation in wind stress amplitudes are usually larger than the mean, periods of weak negative curl do occur, especially in the summer season when the largest normalized differences in the amplitude of wind stress fluctuations are found in the nearshore region of the coastal ocean. Even though the low-frequency wind stress field is well-correlated over the continental shelf and offshore basins, out to distances of 35 km or more from the coast, winds even 10 km inshore of the beach do not represent the coastal wind field, at least in the summer months. The seasonal changes in the spatial structures in wind stress amplitudes suggest that an assessment of the

  19. Statistical considerations of graphite strength for assessing design allowable stresses

    International Nuclear Information System (INIS)

    Ishihara, M.; Mogi, H.; Ioka, I.; Arai, T.; Oku, T.

    1987-01-01

    Several aspects of statistics need to be considered to determine design allowable stresses for graphite structures. These include: 1) Statistical variation of graphite material strength. 2) Uncertainty of calculated stress. 3) Reliability (survival probability) required from operational and safety performance of graphite structures. This paper deals with some statistical considerations of structural graphite for assessing design allowable stress. Firstly, probability distribution functions of tensile and compressive strengths are investigated on experimental Very High Temperature candidated graphites. Normal, logarithmic normal and Weibull distribution functions are compared in terms of coefficient of correlation to measured strength data. This leads to the adaptation of normal distribution function. Then, the relation between factor of safety and fracture probability is discussed on the following items: 1) As the graphite strength is more variable than metalic material's strength, the effect of strength variation to the fracture probability is evaluated. 2) Fracture probability depending on survival probability of 99 ∼ 99.9 (%) with confidence level of 90 ∼ 95 (%) is discussed. 3) As the material properties used in the design analysis are usually the mean values of their variation, the additional effect of these variations on the fracture probability is discussed. Finally, the way to assure the minimum ultimate strength with required survival probability with confidence level is discussed in view of statistical treatment of the strength data from varying sample numbers in a material acceptance test. (author)

  20. The structure and strength of public attitudes towards wind farm development

    Science.gov (United States)

    Bidwell, David Charles

    A growing social science literature seeks to understand why, despite broad public support for wind energy, proposals for specific projects are often met with strong local opposition. This gap between general and specific attitudes is viewed as a significant obstacle to the deployment of wind energy technologies. This dissertation applies theoretical perspectives and methodological tools from social psychology to provide insights on the structure and strength of attitudes towards the potential development of commercial wind farm in three coastal areas of Michigan. A survey of attitudes was completed by 375 residents in these communities and structural equation modeling was used to explore the relationship among variables. The analysis found that attitudes towards wind farm development are shaped by anticipated economic benefits to the community, but expectations of economic benefit are driven by personal values. Social psychology has long recognized that all attitudes are not created equal. Weak attitudes are fleeting and prone to change, while strong attitudes are stable over time and resistant to change. There are two fundamental paths to strong attitudes: repeated experience with an attitude object or the application of deeply held principles or values to that object. Structural equation models were also used to understand the strength of attitudes among the survey respondents. Both the anticipated effects of wind farm development and personal values were found to influence the strength of attitudes towards wind farms. However, while expectations that wind farm development will have positive effects on the economy bolster two measures of attitude strength (collective identity and importance), these expectations are associated with a decline in a third measure (confidence). A follow-up survey asking identical questions was completed by completed by 187 respondents to the initial survey. Linear regressions models were used to determine the effects of attitude

  1. Relaxation of stress and density, strength (fatigue)

    CERN Document Server

    Gräfe, Wolfgang

    2015-01-01

    This treatment of ""Time-Dependent Mechanical Properties of Solids"" beginswith a phenomenological description of the transport of some unspecifiedentity. It is assumed that the transport is caused by mechanical stresses ortemperature fields. Using these assumptions, it is possible to deduceformulae for a theoretically based description of several phenomena withoutreferring to any specific process or entity. These theoretical results thenprovide the tools for performing methodologically better scientific work andfor a better analysis of data in the practical application of materials. Bypublish

  2. Strength conditions for the elastic structures with a stress error

    Science.gov (United States)

    Matveev, A. D.

    2017-10-01

    As is known, the constraints (strength conditions) for the safety factor of elastic structures and design details of a particular class, e.g. aviation structures are established, i.e. the safety factor values of such structures should be within the given range. It should be noted that the constraints are set for the safety factors corresponding to analytical (exact) solutions of elasticity problems represented for the structures. Developing the analytical solutions for most structures, especially irregular shape ones, is associated with great difficulties. Approximate approaches to solve the elasticity problems, e.g. the technical theories of deformation of homogeneous and composite plates, beams and shells, are widely used for a great number of structures. Technical theories based on the hypotheses give rise to approximate (technical) solutions with an irreducible error, with the exact value being difficult to be determined. In static calculations of the structural strength with a specified small range for the safety factors application of technical (by the Theory of Strength of Materials) solutions is difficult. However, there are some numerical methods for developing the approximate solutions of elasticity problems with arbitrarily small errors. In present paper, the adjusted reference (specified) strength conditions for the structural safety factor corresponding to approximate solution of the elasticity problem have been proposed. The stress error estimation is taken into account using the proposed strength conditions. It has been shown that, to fulfill the specified strength conditions for the safety factor of the given structure corresponding to an exact solution, the adjusted strength conditions for the structural safety factor corresponding to an approximate solution are required. The stress error estimation which is the basis for developing the adjusted strength conditions has been determined for the specified strength conditions. The adjusted strength

  3. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Curl

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  4. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  5. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  6. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  7. Effect of internal stress on the strength of PZT ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Tai, Weon Pil; Yun, Yeo Bum; Kim, Song Hee [Kangwon National Univ., Chunchon (Korea, Republic of)

    1996-01-01

    The aim of this study is to investigate the change of bending strength and fatigue strength in the unpolled and poled Pb(Zr, Ti)O ferroelectrics of tetragonal, morphotropic phase boundary (MPB) and rhombohedral composition in terms of internal stress which is measured by XRD method. Before poling treatment the highest bending strength was found in rhombohedral composition. After poling treatment, the bending strength decreased in all compositions but it decreased most remarkably in tetragonal composition. The most prominent decrease of bending strength after poling treatment in tetragonal was attributed to the occurrence of microcracks due to high anisotropic internal stress around grain boundary which was induced by domain alignment toward electric field direction in the microstructure having tetragonality. The decrease of bending strength after poling in MPB and rhombohedral composition was not due to the occurrence of microcracks but to the increase in tensile internal stress perpendicular to the direction of crack propagation by domain alignment. Fatigue strength was higher before poling treatment than after poling treatment for various compositions. 13 refs., 2 tabs., 5 figs.

  8. Test Results of a Nb3Sn Wind/React ''Stress-Managed'' Block Dipole

    International Nuclear Information System (INIS)

    McInturff, A.; Bish, P.; Blackburn, R.; Diaczenko, N.; Elliott, T.; Hafalia Jr., R.; Henchel, W.; Jaisle, A.; Lau, W.; Lietzke, A.; McIntyre, P.; Noyes, P.; Nyman, M.; Sattarov, A.; Sattarov, A.

    2006-01-01

    A second phase of a highfield dipole technology development has been tested. A Nb3Sn block-coil model dipole was fabricated, using magnetic mirror geometry and wind/react coil technology. The primary objective of this phase was to make a first experimental test of the stress-management strategy pioneered at Texas A and M. In this strategy a high-strength support matrix is integrated with the windings to intercept Lorentz stress from the inner winding so that it does not accumulate in the outer winding. The magnet attained a field that was consistent with short sample limit on the first quench; there was no training. The decoupling of Lorentz stress between inner and outer windings was validated. In ramp rate studies the magnet exhibited a remarkable robustness in rapid ramping operation. It reached 85 percent of short sample(ss) current even while ramping 2-3 T/s. This robustness is attributed to the orientation of the Rutherford cables parallel to the field in the windings, instead of the transverse orientation that characterizes common dipole designs. Test results are presented and the next development phase plans are discussed

  9. Strength and fatigue of wind turbine rotor laminates and subcomponents

    NARCIS (Netherlands)

    Nijssen, R.X.T.; Westphal, T.; Stammes, E.; Sari, J.K.

    2010-01-01

    This paper gives an overview of current wind turbine rotor blade composite materials research carried out in the material's laboratory of WMC within the framework of European projects. It outlines the collection and analysis of reference data, research into the effect of temperature and frequency on

  10. design of ceramic membrane supports: permeability, tensile strength and stress

    NARCIS (Netherlands)

    Biesheuvel, Pieter Maarten; Biesheuvel, P.M.; Verweij, H.

    1999-01-01

    A membrane support provides mechanical strength to a membrane top layer to withstand the stress induced by the pressure difference applied over the entire membrane and must simultaneously have a low resistance to the filtrate flow. In this paper an experimental and a theoretical approach toward the

  11. Strength and residual stress of Mg-PSZ after grinding

    NARCIS (Netherlands)

    van den Berg, P.H.J.; With, de G.

    1993-01-01

    The influence of grinding with two grinding wheels, differing mainly in diamond-grain size, on the properties of MgO-partially stabilized ZrO2 ceramics (Mg-PSZ) was examd. The residual stress, the amt. of monoclinic zirconia, and the strength of the material were detd. From these measurements, depth

  12. Estimation of wind stress using dual-frequency TOPEX data

    Science.gov (United States)

    Elfouhaily, Tanos; Vandemark, Douglas; Gourrion, Jéro‸me; Chapron, Bertrand

    1998-10-01

    The TOPEX/POSEIDON satellite carries the first dual-frequency radar altimeter. Monofrequency (Ku-band) algorithms are presently used to retrieve surface wind speed from the altimeter's radar cross-section measurement (σ0Ku). These algorithms work reasonably well, but it is also known that altimeter wind estimates can be contaminated by residual effects, such as sea state, embedded in the σ0Ku measurement. Investigating the potential benefit of using two frequencies for wind retrieval, it is shown that a simple evaluation of TOPEX data yields previously unavailable information, particularly for high and low wind speeds. As the wind speed increases, the dual-frequency data provides a measurement more directly linked to the short-scale surface roughness, which in turn is associated with the local surface wind stress. Using a global TOPEX σ0° data set and TOPEX's significant wave height (Hs) estimate as a surrogate for the sea state's degree of development, it is also shown that differences between the two TOPEX σ0 measurements strongly evidence nonlocal sea state signature. A composite scattering theory is used to show how the dual-frequency data can provide an improved friction velocity model, especially for winds above 7 m/s. A wind speed conversion is included using a sea state dependent drag coefficient fed with TOPEX Hs data. Two colocated TOPEX-buoy data sets (from the National Data Buoy Center (NDBC) and the Structure des Echanges Mer-Atmosphre, Proprietes des Heterogeneites Oceaniques: Recherche Expérimentale (SEMAPHORE) campaign) are employed to test the new wind speed algorithm. A measurable improvement in wind speed estimation is obtained when compared to the monofrequency Witter and Chelton [1991] model.

  13. Stress corrosion in high-strength aluminum alloys

    Science.gov (United States)

    Dorward, R. C.; Hasse, K. R.

    1980-01-01

    Report describes results of stress-corrosion tests on aluminum alloys 7075, 7475, 7050, and 7049. Tests compare performance of original stress-corrosion-resistant (SCR) aluminum, 7075, with newer, higher-strength SCR alloys. Alloys 7050 and 7049 are found superior in short-transverse cross-corrosion resistance to older 7075 alloy; all alloys are subject to self-loading effect caused by wedging of corrosion products in cracks. Effect causes cracks to continue to grow, even at very-low externally applied loads.

  14. Variation of air--water gas transfer with wind stress and surface viscoelasticity

    OpenAIRE

    Frew, Nelson M.; Bock, Erik J.; McGillis, Wade R.; Karachintsev, Andrey V.; Hara, Tetsu; Münsterer, Thomas; Jähne, Bernd

    1995-01-01

    Previous parameterizations of gas transfer velocity have attempted to cast this quantity as a function of wind speed or wind-stress. This study demonstrates that the presence of a surface film is effective at reducing the gas transfer velocity at constant wind-stress. Gas exchange experiments were performed at WHOI and UH using annular wind-wave tanks of different scales. Systematic variations of wind-stress and surfactant concentration (Triton-X-100) were explored to determ...

  15. Northeast storms ranked by wind stress and wave-generated bottom stress observed in Massachusetts Bay, 1990-2006

    Science.gov (United States)

    Butman, B.; Sherwood, C.R.; Dalyander, P.S.

    2008-01-01

    Along the coast of the northeastern United States, strong winds blowing from the northeast are often associated with storms called northeasters, coastal storms that strongly influence weather. In addition to effects caused by wind stress, the sea floor is affected by bottom stress associated with these storms. Bottom stress caused by orbital velocities associated with surface waves integrated over the duration of a storm is a metric of storm strength at the sea floor. Near-bottom wave-orbital velocities calculated by using measurements of significant wave height and dominant wave period and the parametric spectral method described in Wiberg and Sherwood [Wiberg, P.L., Sherwood, C.R. Calculating wave-generated bottom orbital velocities from surface wave parameters. Computers in Geosciences, in press] compared well with observations in Massachusetts Bay. Integrated bottom-wave stress (called IWAVES), calculated at 30 m water depth, and a companion storm-strength metric, integrated surface wind stress at 10 m (called IWINDS), are used to provide an overview of the strength, frequency, and timing of large storms in Massachusetts Bay over a 17-year period from January 1990 through December 2006. These new metrics reflect both storm duration and intensity. Northeast storms were the major cause of large waves in Massachusetts Bay because of the long fetch to the east: of the strongest 10% of storms (n=38) ranked by IWAVES, 22 had vector-averaged wind stress from the northeast quadrant. The Blizzard of December 1992, the Perfect Storm of October 1991, and a December 2003 storm were the strongest three storms ranked by IWAVES and IWINDS, and all were northeasters. IWAVES integrated over the winter season (defined as October-May) ranged by about a factor of 11; the winters with the highest integrated IWAVES were 1992-1993 and 2004-2005 and the winter with the lowest integrated IWAVES was 2001-2002. May 2005 was the only month in the 17-year record that two of the nine

  16. Soil erosion rates caused by wind and saltating sand stresses in a wind tunnel

    International Nuclear Information System (INIS)

    Ligotke, M.W.

    1993-02-01

    Wind erosion tests were performed in a wind tunnel in support of the development of long-term protective barriers to cap stabilized waste sites at the Hanford Site. Controlled wind and saltating sand erosive stresses were applied to physical models of barrier surface layers to simulate worst-case eolian erosive stresses. The goal of these tests was to provide information useful to the design and evaluation of the surface layer composition of an arid-region waste site barrier concept that incorporates a deep fine-soil reservoir. A surface layer composition is needed that will form an armor resistant to eolian erosion during periods of extreme dry climatic conditions, especially when such conditions result in the elimination or reduction of vegetation by water deprivation or wildfire. Because of the life span required of Hanford waste barriers, it is important that additional work follow these wind tunnel studies. A modeling effort is planned to aid the interpretation of test results with respect to the suitability of pea gravel to protect the finite-soil reservoir during long periods of climatic stress. It is additionally recommended that wind tunnel tests be continued and field data be obtained at prototype or actual barrier sites. Results wig contribute to barrier design efforts and provide confidence in the design of long-term waste site caps for and regions

  17. Wind stress, curl and vertical velocity in the Bay of Bengal during southwest monsoon, 1984

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, M.T.; Heblekar, A.K.; Murty, C.S.

    Wind distribution observed during southwest monsoon of 1984 has used to derive the mean wind stress for the season at every 1 degree square grid and curl over the Bay of Bengal. Two regions of maximum wind stress are present over the Bay of Bengal...

  18. Blended 6-Hourly Sea Surface Wind Vectors and Wind Stress on a Global 0.25 Degree Grid (1987-2011)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Blended Global Sea Surface Winds products contain ocean surface wind vectors and wind stress on a global 0.25 degree grid, in multiple time resolutions of...

  19. Stress-strength reliability for general bivariate distributions

    Directory of Open Access Journals (Sweden)

    Alaa H. Abdel-Hamid

    2016-10-01

    Full Text Available An expression for the stress-strength reliability R=P(X1

  20. Bond strength and stress measurements in thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Gell, M.; Jordan, E. [Univ. of Connecticut, Storrs, CT (United States)

    1995-10-01

    Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. To meet the aggressive Advanced Turbine Systems goals for efficiency, durability and the environment, it will be necessary to employ thermal barrier coatings on turbine airfoils and other hot section components. For The successful application of TBCs to ATS engines with 2600{degrees}F turbine inlet temperatures and required component lives 10 times greater than those for aircraft gas turbine engines, it is necessary to develop quantitative assessment techniques for TBC coating integrity with time and cycles in ATS engines. Thermal barrier coatings in production today consist of a metallic bond coat, such as an MCrAlY overlay coating or a platinum aluminide (Pt-Al) diffusion coating. During heat treatment, both these coatings form a thin, tightly adherent alumina (Al{sub 2}O{sub 3}) film. Failure of TBC coatings in engine service occurs by spallation of the ceramic coating at or near the bond coat to alumina or the alumina to zirconia bonds. Thus, it is the initial strength of these bonds and the stresses at the bond plane, and their changes with engine exposure, that determines coating durability. The purpose of this program is to provide, for the first time, a quantitative assessment of TBC bond strength and bond plane stresses as a function of engine time and cycles.

  1. Suction pressure, yield strength and effective stress of partially saturated unbound granular pavement layers

    CSIR Research Space (South Africa)

    Theyse, HL

    2006-09-01

    Full Text Available to the ratio of the imposed stress over the shear strength of the material. Conventionally, the shear strength of the material was characterised with the Mohr-Coulomb shear strength parameters. This paper further develops a recent yield strength model...

  2. Wind stress over the Arabian Sea from ship reports and Seasat scatterometer data

    Science.gov (United States)

    Perigaud, C.; Minster, J. F.; Delecluse, P.

    1989-01-01

    Seasat scatterometer data over the Arabian Sea are used to build wind-stress fields during July and August 1978. They are first compared with 3-day wind analyses from ship data along the Somali coast. Seasat scatterometer specifications of 2-m/s and 20-deg accuracy are fulfilled in almost all cases. The exceptions are for winds stronger than 14 m/s, which are underestimated by the scatterometer by 15 percent. Wind stress is derived from these wind data using a bulk formula with a drag coefficient depending on the wind intensity. A successive-correction objective analysis is used to build the wind-stress field over the Arabian Sea with 2 x 2-deg and 6-day resolution. The final wind-stress fields are not significantly dependent on the objective analysis because of the dense coverage of the scatterometer. The combination of scatterometer and coastal ship data gives the best coverage to resolve monsoon wind structures even close to the coast. The final wind stress fields show wind features consistent with other monthly mean wind stress field. However, a high variability is observed on the 6-day time scale.

  3. A dependent stress-strength interference model based on mixed copula function

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Jian Xiong; An, Zong Wen; Liu, Bo [School of Mechatronics Engineering, Lanzhou University of Technology, Lanzhou (China)

    2016-10-15

    In the traditional Stress-strength interference (SSI) model, stress and strength must satisfy the basic assumption of mutual independence. However, a complex dependence between stress and strength exists in practical engineering. To evaluate structural reliability under the case that stress and strength are dependent, a mixed copula function is introduced to a new dependent SSI model. This model can fully characterize the dependence between stress and strength. The residual square sum method and genetic algorithm are also used to estimate the unknown parameters of the model. Finally, the validity of the proposed model is demonstrated via a practical case. Results show that traditional SSI model ignoring the dependence between stress and strength more easily overestimates product reliability than the new dependent SSI model.

  4. The benefits of personal strengths in mental health of stressed students: A longitudinal investigation.

    Science.gov (United States)

    Duan, Wenjie

    2016-11-01

    This study used a two-wave longitudinal research design to explore the role of individual strengths, including interpersonal strength, intellectual strength, and temperance strength, in affecting the mental health of stressed college students. A total of 404 stressed Chinese college students were screened to participate in this 12-month longitudinal study. At the beginning of the study (Time 1), students who had not experienced stressful events within the last 12 months were invited to assess their strengths, psychological well-being, and psychological symptoms. After 12 months (Time 2), 404 students who reported stressful experiences completed the scales again and were retained for the final analyses. Academics-related stressors were the most endorsed life events among college students, whose states of mental health showed downward trends from Time 1 to Time 2. Three strengths had weak to modest correlations to mental health at both Time 1 and Time 2. Although the additional variances of mental health explained by the three strengths were very modest, the mediational roles of the strengths were identified. The perceived stress completely mediated the relationship between the strengths and the psychological symptoms and partly mediated the relationship between the strengths and psychological well-being. Individual strengths may function as a defense against perceived stress and are protective factors of mental health. These strengths maintain mental health by enhancing the psychological well-being and reducing the psychological symptoms of individuals.

  5. Swell impact on wind stress and atmospheric mixing in a regional coupled atmosphere-wave model

    DEFF Research Database (Denmark)

    Wu, Lichuan; Rutgersson, Anna; Sahlée, Erik

    2016-01-01

    Over the ocean, the atmospheric turbulence can be significantly affected by swell waves. Change in the atmospheric turbulence affects the wind stress and atmospheric mixing over swell waves. In this study, the influence of swell on atmospheric mixing and wind stress is introduced into an atmosphere-wave-coupled...... regional climate model, separately and combined. The swell influence on atmospheric mixing is introduced into the atmospheric mixing length formula by adding a swell-induced contribution to the mixing. The swell influence on the wind stress under wind-following swell, moderate-range wind, and near......-neutral and unstable stratification conditions is introduced by changing the roughness length. Five year simulation results indicate that adding the swell influence on atmospheric mixing has limited influence, only slightly increasing the near-surface wind speed; in contrast, adding the swell influence on wind stress...

  6. A discrete stress-strength interference model based on universal generating function

    International Nuclear Information System (INIS)

    An Zongwen; Huang Hongzhong; Liu Yu

    2008-01-01

    Continuous stress-strength interference (SSI) model regards stress and strength as continuous random variables with known probability density function. This, to some extent, results in a limitation of its application. In this paper, stress and strength are treated as discrete random variables, and a discrete SSI model is presented by using the universal generating function (UGF) method. Finally, case studies demonstrate the validity of the discrete model in a variety of circumstances, in which stress and strength can be represented by continuous random variables, discrete random variables, or two groups of experimental data

  7. Compressive strength evolution of thermally-stressed Saint Maximin limestone.

    Science.gov (United States)

    Farquharson, J.; Griffiths, L.; Baud, P.; Wadsworth, F. B.; Heap, M. J.

    2017-12-01

    The Saint Maximin quarry (Oise, France) opened in the early 1600s, and its limestone has been used extensively as masonry stone, particularly during the classical era of Parisian architecture from the 17th century onwards. Its widespread use has been due to a combination of its regional availability, its high workability, and its aesthetic appeal. Notable buildings completed using this material include sections of the Place de la Concorde and the Louvre in Paris. More recently, however, it has seen increasing use in the construction of large private residences throughout the United States as well as extensions to private institutions such as Stanford University. For any large building, fire hazard can be a substantial concern, especially in tectonically active areas where catastrophic fires may arise following large-magnitude earthquakes. Typically, house fires burn at temperatures of around 600 °C ( 1000 F). Given the ubiquity of this geomaterial as a building stone, it is important to ascertain the influence of heating on the strength of Saint Maximin limestone (SML), and in turn the structural stability of the buildings it is used in. We performed a series of compressive tests and permeability measurements on samples of SML to determine its strength evolution in response to heating to incrementally higher temperatures. We observe that the uniaxial compressive strength of SML decreases from >12 MPa at room temperature to 400 °C). We anticipate that this substantial weakening is in part a result of thermal microcracking, whereby changes in temperature induce thermal stresses due to a mismatch in thermal expansion between the constituent grains. This mechanism is compounded by the volumetric increase of quartz through its alpha - beta transition at 573 °C, and by the thermal decomposition of calcite. To track the formation of thermal microcracks, we monitor acoustic emissions, a common proxy for microcracking, during the heating of an SML sample. The

  8. Strength and fatigue testing of large size wind turbines rotors. Vol. II: Full size natural vibration and static strength test, a reference case

    Energy Technology Data Exchange (ETDEWEB)

    Arias, F.; Soria, E.

    1996-12-01

    This report shows the methods and procedures selected to define a strength test for large size wind turbine, anyway in particular it application on a 500 kW blade and it results obtained in the test carried out in july of 1995 in Asinel`s test plant (Madrid). Henceforth, this project is designed in an abbreviate form whit the acronym SFAT. (Author)

  9. Strength and fatigue testing of large size wind turbines rotors. Volume II. Full size natural vibration and static strength test, a reference case

    International Nuclear Information System (INIS)

    Arias, F.; Soria, E.

    1996-01-01

    This report shows the methods and procedures selected to define a strength test for large size wind turbine, anyway in particularly it application on a 500 kW blade and it results obtained in the test carried out in july of 1995 in Asinel test plant (Madrid). Henceforth, this project is designed in an abbreviate form whit the acronym SFAT. (Author)

  10. The relationships of character strengths with coping, work-related stress, and job satisfaction.

    Science.gov (United States)

    Harzer, Claudia; Ruch, Willibald

    2015-01-01

    Personality traits have often been highlighted to relate to how people cope with stressful events. The present paper focuses on character strengths as positive personality traits and examines two basic assumptions that were derived from a core characteristic of character strengths (i.e., to determine how individuals deal with adversities): (1) character strengths correlate with coping and (2) buffer the effects of work-related stress on job satisfaction. Two different samples (i.e., a mixed sample representing various occupations [N = 214] and a nurses sample [N = 175]) filled in measures for character strengths, coping, work-related stress, and job satisfaction. As expected, intellectual, emotional, and interpersonal strengths were related to coping. Interpersonal strengths played a greater role for coping among nurses, as interactions with others are an essential part of their workday. Furthermore, intellectual strengths partially mediated the negative effect of work-related stress on job satisfaction. These findings open a new field for research on the role of personality in coping with work-related stress. Character strengths are trainable personal characteristics, and therefore valuable resources to improve coping with work-related stress and to decrease the negative effects of stress. Further research is needed to investigate this assumed causality.

  11. The relationships of character strengths with coping, work-related stress, and job satisfaction

    Directory of Open Access Journals (Sweden)

    Claudia eHarzer

    2015-02-01

    Full Text Available Personality traits have often been highlighted to relate to how people cope with stressful events. The present paper focuses on character strengths as positive personality traits and examines two basic assumptions that were derived from a core characteristic of character strengths (i.e., to determine how individuals deal with adversities: (1 Character strengths correlate with coping and (2 buffer the effects of work-related stress on job satisfaction. Two different samples (i.e., a mixed sample representing various occupations [N = 214] and a nurses sample [N = 175] filled in measures for character strengths, coping, work-related stress, and job satisfaction. As expected, intellectual, emotional, and interpersonal strengths were related to coping. Interpersonal strengths played a greater role for coping among nurses, as interactions with others are an essential part of their workday. Furthermore, intellectual strengths partially mediated the negative effect of work-related stress on job satisfaction. These findings open a new field for research on the role of personality in coping with work-related stress. Character strengths are trainable personal characteristics, and therefore valuable resources to improve coping with work-related stress and to decrease the negative effects of stress. Further research is needed to investigate this assumed causality.

  12. Strength and Reliability of Wood for the Components of Low-cost Wind Turbines: Computational and Experimental Analysis and Applications

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Freere, Peter; Sharma, Ranjan

    2009-01-01

    of experiments and computational investigations. Low cost testing machines have been designed, and employed for the systematic analysis of different sorts of Nepali wood, to be used for the wind turbine construction. At the same time, computational micromechanical models of deformation and strength of wood......This paper reports the latest results of the comprehensive program of experimental and computational analysis of strength and reliability of wooden parts of low cost wind turbines. The possibilities of prediction of strength and reliability of different types of wood are studied in the series...... are developed, which should provide the basis for microstructure-based correlating of observable and service properties of wood. Some correlations between microstructure, strength and service properties of wood have been established....

  13. Influence of mechanical stress level in preliminary stress-corrosion testing on fatigue strength of a low-carbon steel

    International Nuclear Information System (INIS)

    Aleskerova, S.A.; Pakharyan, V.A.

    1978-01-01

    Effect of corrosion and mechanical factors of preliminary stress corrosion of a metal in its fatigue strength, has been investigated. Smooth cylindrical samples of 20 steel have been tested. Preliminary corrosion under stress has been carried out under natural sea conditions. It is shown that mechanical stresses in the case of preliminary corrosion affect fatigue strength of low-carbon steels, decreasing the range of limited durability and fatigue limit. This effect increases with the increase of stress level and agressivity of corrosive medium

  14. Methodology of strength calculation under alternating stresses using the diagram of limiting amplitudes

    Science.gov (United States)

    Konovodov, V. V.; Valentov, A. V.; Kukhar, I. S.; Retyunskiy, O. Yu; Baraksanov, A. S.

    2016-08-01

    The work proposes the algorithm to calculate strength under alternating stresses using the developed methodology of building the diagram of limiting stresses. The overall safety factor is defined by the suggested formula. Strength calculations of components working under alternating stresses in the great majority of cases are conducted as the checking ones. It is primarily explained by the fact that the overall fatigue strength reduction factor (Kσg or Kτg) can only be chosen approximately during the component design as the engineer at this stage of work has just the approximate idea on the component size and shape.

  15. Experimental investigation on ultimate strength and failure response of composite box beams used in wind turbine blades

    DEFF Research Database (Denmark)

    Tang, Jing; Chen, Xiao

    2018-01-01

    This study focuses on the ultimate strength and failure response of composite box beams under three-point bending. The box beams consist of spar caps and shear webs and they are typically used in wind turbine blades as load-carrying members. Different spar cap configurations and loading directions...

  16. A Thermodamage Strength Theoretical Model of Ceramic Materials Taking into Account the Effect of Residual Stress

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2012-01-01

    Full Text Available A thermodamage strength theoretical model taking into account the effect of residual stress was established and applied to each temperature phase based on the study of effects of various physical mechanisms on the fracture strength of ultrahigh-temperature ceramics. The effects of SiC particle size, crack size, and SiC particle volume fraction on strength corresponding to different temperatures were studied in detail. This study showed that when flaw size is not large, the bigger SiC particle size results in the greater effect of tensile residual stress in the matrix grains on strength reduction, and this prediction coincides with experimental results; and the residual stress and the combined effort of particle size and crack size play important roles in controlling material strength.

  17. Braze alloy process and strength characterization studies for 18 nickel grade 200 maraging steel with application to wind tunnel models

    Science.gov (United States)

    Bradshaw, James F.; Sandefur, Paul G., Jr.; Young, Clarence P., Jr.

    1991-01-01

    A comprehensive study of braze alloy selection process and strength characterization with application to wind tunnel models is presented. The applications for this study include the installation of stainless steel pressure tubing in model airfoil sections make of 18 Ni 200 grade maraging steel and the joining of wing structural components by brazing. Acceptable braze alloys for these applications are identified along with process, thermal braze cycle data, and thermal management procedures. Shear specimens are used to evaluate comparative shear strength properties for the various alloys at both room and cryogenic (-300 F) temperatures and include the effects of electroless nickel plating. Nickel plating was found to significantly enhance both the wetability and strength properties for the various braze alloys studied. The data are provided for use in selecting braze alloys for use with 18 Ni grade 200 steel in the design of wind tunnel models to be tested in an ambient or cryogenic environment.

  18. Bone geometry, strength, and muscle size in runners with a history of stress fracture.

    Science.gov (United States)

    Popp, Kristin L; Hughes, Julie M; Smock, Amanda J; Novotny, Susan A; Stovitz, Steven D; Koehler, Scott M; Petit, Moira A

    2009-12-01

    Our primary aim was to explore differences in estimates of tibial bone strength, in female runners with and without a history of stress fractures. Our secondary aim was to explore differences in bone geometry, volumetric density, and muscle size that may explain bone strength outcomes. A total of 39 competitive distance runners aged 18-35 yr, with (SFX, n = 19) or without (NSFX, n = 20) a history of stress fracture were recruited for this cross-sectional study. Peripheral quantitative computed tomography (XCT 3000; Orthometrix, White Plains, NY) was used to assess volumetric bone mineral density (vBMD, mg x mm(-3)), bone area (ToA, mm(2)), and estimated compressive bone strength (bone strength index (BSI) = ToA x total volumetric density (ToD(2))) at the distal tibia (4%). Total (ToA, mm(2)) and cortical (CoA, mm(2)) bone area, cortical vBMD, and estimated bending strength (strength-strain index (SSIp), mm(3)) were measured at the 15%, 25%, 33%, 45%, 50%, and 66% sites. Muscle cross-sectional area (MCSA) was measured at the 50% and 66% sites. Participants in the SFX group had significantly smaller (7%-8%) CoA at the 45%, 50%, and 66% sites (P stress fracture. However, the lower strength was appropriate for the smaller muscle size, suggesting that interventions to reduce stress fracture risk might be aimed at improving muscle size and strength.

  19. Stress Analysis and Strength Prediction of Adhesively Bonded Composite Joints

    National Research Council Canada - National Science Library

    Rastogi, Naveen

    1998-01-01

    .... Further, the submodeling technique available in the commercial finite element package ABAQUS is explored to study the three-dimensional stress field in the vicinity of joint edges and debond cracks...

  20. Stress analysis of composite wind turbine blade by finite element method

    Science.gov (United States)

    Yeh, Meng-Kao; Wang, Chen-Hsu

    2017-10-01

    In this study, the finite element analysis software ANSYS was used to analyze the composite wind turbine blade. The wind turbine blade model used is adopted from the 5 MW model of US National Renewable Energy Laboratory (NREL). The wind turbine blade is a sandwich structure, comprising outermost carbon fiber cloth/epoxy composites, the inner glass fiber/vinylester layers, and PVC foam core, together with stiffeners. The wind pressure is converted into the load on the blade structure. The stress distribution and deformation of wind turbine blade were obtained by considering different pitch angles and at different angular positions. The Tsai-Hill criterion was used to determine the failure of wind turbine blade. The results show that at the 0° pitch angle, the wind turbine blade is subjected to the largest combined load and therefore the stress is the largest; with the increasing pitch angle, the load gradually decreases and the stress is also smaller. The stress and displacement are the greatest when the wind blade is located at 120° angular position from its highest vertex.

  1. Residual stress in a thick section high strength T-butt weld

    International Nuclear Information System (INIS)

    Pearce, S.V.; Linton, V.M.; Oliver, E.C.

    2008-01-01

    Residual stresses in a structure are generated as a result of the various fabrication and welding processes used to make the component. Being able to quantify these residual stresses is a key step in determining the continuing integrity of a structure in service. In this work, the residual stresses around a high strength, quenched and tempered steel T-butt web to curved plate weld have been measured using neutron strain scanning. The results show that the residual stresses near the weld were dominated by the welding residual stresses, while the stresses further from the weld were dominated by the bending residual stresses. The results suggest that the combination of welding-induced residual stress and significant pre-welding residual stress, as in the case of a thick bent section of plate can significantly alter the residual stress profile from that in a flat plate

  2. TAO/TRITON, RAMA, and PIRATA Buoys, Daily, 1989-present, Wind Stress

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has daily Wind Stress data from the TAO/TRITON (Pacific Ocean, https://www.pmel.noaa.gov/gtmba/ ), RAMA (Indian Ocean,...

  3. TAO/TRITON, RAMA, and PIRATA Buoys, 5-Day, 1989-present, Wind Stress

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has 5-day Wind Stress data from the TAO/TRITON (Pacific Ocean, https://www.pmel.noaa.gov/gtmba/ ), RAMA (Indian Ocean,...

  4. TAO/TRITON, RAMA, and PIRATA Buoys, Monthly, 1989-present, Wind Stress

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has monthly Wind Stress data from the TAO/TRITON (Pacific Ocean, https://www.pmel.noaa.gov/gtmba/ ), RAMA (Indian Ocean,...

  5. Econometric analysis of the changing effects in wind strength and significant wave height on the probability of casualty in shipping.

    Science.gov (United States)

    Knapp, Sabine; Kumar, Shashi; Sakurada, Yuri; Shen, Jiajun

    2011-05-01

    This study uses econometric models to measure the effect of significant wave height and wind strength on the probability of casualty and tests whether these effects changed. While both effects are in particular relevant for stability and strength calculations of vessels, it is also helpful for the development of ship construction standards in general to counteract increased risk resulting from changing oceanographic conditions. The authors analyzed a unique dataset of 3.2 million observations from 20,729 individual vessels in the North Atlantic and Arctic regions gathered during the period 1979-2007. The results show that although there is a seasonal pattern in the probability of casualty especially during the winter months, the effect of wind strength and significant wave height do not follow the same seasonal pattern. Additionally, over time, significant wave height shows an increasing effect in January, March, May and October while wind strength shows a decreasing effect, especially in January, March and May. The models can be used to simulate relationships and help understand the relationships. This is of particular interest to naval architects and ship designers as well as multilateral agencies such as the International Maritime Organization (IMO) that establish global standards in ship design and construction. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Effects of drought stress on seed sink strength and leaf protein ...

    African Journals Online (AJOL)

    Assimilate availability and the capacity to utilise them in the reproductive structures to a large extent determine reproductive sink establishment and yield of crops under drought stress. This study was carried out to investigate the effect of drought stress imposed at early pod-fill stage on seed sink strength of common bean ...

  7. Comparison of Positive Character Strengths in Employees with Healthy and Unhealthy Occupational Stress Coping Styles

    Directory of Open Access Journals (Sweden)

    simin dokht kalani

    2017-05-01

    Full Text Available The aim of the study was to compare the protective and interpersonal strengths as positive personality traits in employees with healthy (G: good health pattern, S: sparing pattern and unhealthy (A: ambitious pattern, B: burnout pattern job stress coping styles. Therefore, 146 employees of an industrial organization in Mashhad were selected by stratified random sampling and asked to respond to research tools. The instruments were the Values in Action Inventory of Strengths from Peterson & Seligman and Work-related Behavior and Experience Patterns Questionnaire from Schaarschmidt & Fischer. The results of multivariate analysis of variance showed that employees with healthy coping styles had higher means of protective and interpersonal strengths than unhealthy subjects. These findings open a new field for research on the role of personality in coping with work-related stress. Character strengths are trainable personal characteristics. Therefore, they are valuable resources to improve coping with work-related stress and to decreasing its negative effects.

  8. Growth of marine yeast on different strength of stress solutes

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, R.

    tested against the stress solutes NaCl (0-16%), potassium chloride (KCl) and sodium sulphate (Na sub(2) SO sub(4)) at 0.4%, 4% and 8% concentrations. D. hansenii and D. marama were the most versatile isolates exhibiting excellent growth in all...

  9. Stress corrosion cracking of several high strength ferrous and nickel alloys

    Science.gov (United States)

    Nelson, E. E.

    1971-01-01

    The stress corrosion cracking resistance of several high strength ferrous and nickel base alloys has been determined in a sodium chloride solution. Results indicate that under these test conditions Multiphase MP35N, Unitemp L605, Inconel 718, Carpenter 20Cb and 20Cb-3 are highly resistant to stress corrosion cracking. AISI 410 and 431 stainless steels, 18 Ni maraging steel (250 grade) and AISI 4130 steel are susceptible to stress corrosion cracking under some conditions.

  10. Bone strength estimates relative to vertical ground reaction force discriminates women runners with stress fracture history.

    Science.gov (United States)

    Popp, Kristin L; McDermott, William; Hughes, Julie M; Baxter, Stephanie A; Stovitz, Steven D; Petit, Moira A

    2017-01-01

    To determine differences in bone geometry, estimates of bone strength, muscle size and bone strength relative to load, in women runners with and without a history of stress fracture. We recruited 32 competitive distance runners aged 18-35, with (SFX, n=16) or without (NSFX, n=16) a history of stress fracture for this case-control study. Peripheral quantitative computed tomography (pQCT) was used to assess volumetric bone mineral density (vBMD, mg/mm 3 ), total (ToA) and cortical (CtA) bone areas (mm 2 ), and estimated compressive bone strength (bone strength index; BSI, mg/mm 4 ) at the distal tibia. ToA, CtA, cortical vBMD, and estimated strength (section modulus; Zp, mm 3 and strength strain index; SSIp, mm 3 ) were measured at six cortical sites along the tibia. Mean active peak vertical (pkZ) ground reaction forces (GRFs), assessed from a fatigue run on an instrumented treadmill, were used in conjunction with pQCT measurements to estimate bone strength relative to load (mm 2 /N∗kg -1 ) at all cortical sites. SSIp and Zp were 9-11% lower in the SFX group at mid-shaft of the tibia, while ToA and vBMD did not differ between groups at any measurement site. The SFX group had 11-17% lower bone strength relative to mean pkZ GRFs (phistory of stress fracture. Bone strength relative to load is also lower in this same region suggesting that strength deficits in the middle 1/3 of the tibia and altered gait biomechanics may predispose an individual to stress fracture. Copyright © 2016. Published by Elsevier Inc.

  11. Fault roughness and strength heterogeneity control earthquake size and stress drop

    KAUST Repository

    Zielke, Olaf

    2017-01-13

    An earthquake\\'s stress drop is related to the frictional breakdown during sliding and constitutes a fundamental quantity of the rupture process. High-speed laboratory friction experiments that emulate the rupture process imply stress drop values that greatly exceed those commonly reported for natural earthquakes. We hypothesize that this stress drop discrepancy is due to fault-surface roughness and strength heterogeneity: an earthquake\\'s moment release and its recurrence probability depend not only on stress drop and rupture dimension but also on the geometric roughness of the ruptured fault and the location of failing strength asperities along it. Using large-scale numerical simulations for earthquake ruptures under varying roughness and strength conditions, we verify our hypothesis, showing that smoother faults may generate larger earthquakes than rougher faults under identical tectonic loading conditions. We further discuss the potential impact of fault roughness on earthquake recurrence probability. This finding provides important information, also for seismic hazard analysis.

  12. Wind-Induced Fatigue Analysis of High-Rise Steel Structures Using Equivalent Structural Stress Method

    Directory of Open Access Journals (Sweden)

    Zhao Fang

    2017-01-01

    Full Text Available Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on the meshing styles and massive curves selected. To address this problem, in this paper, the equivalent structural stress method with advantages of mesh-insensitive quality and capability of unifying different stress-life curves (S-N curves into one is introduced to the wind-induced fatigue assessment of a large-scale complicated high-rise steel structure. The multi-scale finite element model is established and the corresponding wind loading is simulated. Fatigue life assessments using equivalent structural stress method, hot spot stress method and nominal stress method are performed, and the results are verified and comparisons are made. The mesh-insensitive quality is also verified. The results show that the lateral weld toe of the butt weld connecting the beam flange plate and the column is the location where fatigue damage most likely happens. Nominal stress method considers fatigue assessment of welds in a more global way by averaging all the stress on the weld section while in equivalent structural stress method and hot spot method local stress concentration can be taken into account more precisely.

  13. The relationship between the statistics of open ocean currents and the temporal correlations of the wind stress

    International Nuclear Information System (INIS)

    Bel, Golan; Ashkenazy, Yosef

    2013-01-01

    We study the statistics of wind-driven open ocean currents. Using the Ekman layer model for the integrated currents, we investigate analytically and numerically the relationship between the wind-stress distribution and its temporal correlations and the statistics of the open ocean currents. We found that temporally long-range correlated winds result in currents whose statistics is proportional to the wind-stress statistics. On the other hand, short-range correlated winds lead to Gaussian distributions of the current components, regardless of the stationary distribution of the winds, and therefore to a Rayleigh distribution of the current amplitude, if the wind stress is isotropic. We found that the second moment of the current speed exhibits a maximum as a function of the correlation time of the wind stress for a non-zero Coriolis parameter. The results were validated using an oceanic general circulation model. (paper)

  14. A Non-Linear Upscaling Approach for Wind Turbines Blades Based on Stresses

    NARCIS (Netherlands)

    Castillo Capponi, P.; Van Bussel, G.J.W.; Ashuri, T.; Kallesoe, B.

    2011-01-01

    The linear scaling laws for upscaling wind turbine blades show a linear increase of stresses due to the weight. However, the stresses should remain the same for a suitable design. Application of linear scaling laws may lead to an upscaled blade that may not be any more a feasible design. In this

  15. Experimental study on ultimate strength and strain behavior of concrete under biaxial compressive stresses

    International Nuclear Information System (INIS)

    Onuma, Hiroshi; Aoyagi, Yukio

    1976-01-01

    The purpose of this investigation was to study the ultimate strength failure mode and deformation behavior of concrete under short-term biaxial compressive stresses, as an aid to design and analyze the concrete structures subjected to multiaxial compression such as prestressed or reinforced concrete vessel structures. The experimental work on biaxial compression was carried out on the specimens of three mix proportions and different ages with 10cm x 10cm x 10cm cubic shape in a room controlled at 20 0 C. The results are summarized as follows. (1) To minimize the surface friction between specimens and loading platens, the pads of teflon sheets coated with silicone grease were used. The coefficient of friction was measured and was 3 percent on the average. (2) The test data showed that the strength of the concrete subjected to biaxial compression increased as compared to uniaxial compressive strength, and that the biaxial strength increase was mainly dependent on the ratio of principal stresses, and it was hardly affected by mix proportions and ages. (3) The maximum increase of strength, which occurred at the stress ratio of approximately sigma 2 /sigma 1 = 0.6, was about 27 percent higher than the uniaxial strength of concrete. (4) The ultimate strength in case of biaxial compression could be approximated by the parabolic equation. (Kako, I.)

  16. Strength and deformability of graphite under cyclic stresses and temperatures

    International Nuclear Information System (INIS)

    Umanskij, Eh.S.; Uskov, E.I.; Bogomolov, A.V.; Aleksyuk, M.M.

    1978-01-01

    Presented are the results of investigations into a durability of two types of reactor graphites with the average density of 1.8 and 1.65 g/cm 2 under static and cyclic stresses (0.65-0.75 kg/mm 2 ) and temperatures (800 deg C, 250 reversible 800 deg C 250 reversible 1500 deg C). The considerable anisotropy is stated: the durability of the samples under study cut out parallel to the billet axis, is more than twice higher in comparison with that of samples cut out normal to it

  17. Homogeneity of small-scale earthquake faulting, stress, and fault strength

    Science.gov (United States)

    Hardebeck, J.L.

    2006-01-01

    Small-scale faulting at seismogenic depths in the crust appears to be more homogeneous than previously thought. I study three new high-quality focal-mechanism datasets of small (M angular difference between their focal mechanisms. Closely spaced earthquakes (interhypocentral distance stress orientation and fault strength (coefficient of friction) are inferred to be homogeneous as well, to produce such similar earthquakes. Over larger length scales (???2-50 km), focal mechanisms become more diverse with increasing interhypocentral distance (differing on average by 40-70??). Mechanism variability on ???2- to 50 km length scales can be explained by ralatively small variations (???30%) in stress or fault strength. It is possible that most of this small apparent heterogeneity in stress of strength comes from measurement error in the focal mechanisms, as negligibble variation in stress or fault strength (<10%) is needed if each earthquake is assigned the optimally oriented focal mechanism within the 1-sigma confidence region. This local homogeneity in stress orientation and fault strength is encouraging, implying it may be possible to measure these parameters with enough precision to be useful in studying and modeling large earthquakes.

  18. Acceptance and stress effects of aircraft obstruction markings of wind turbines

    International Nuclear Information System (INIS)

    Pohl, Johannes; Hübner, Gundula; Mohs, Anja

    2012-01-01

    A dominant resistance factor against wind power projects seems to be their visual impact on the landscape. In addition stress effects from aircraft obstruction markings are an emerging topic related to acceptance. As the height of wind turbines increases, so does the number of mandatory obstruction markings. Recently, obstruction markings have caused a growing number of complaints from residents. Whether obstruction markings indeed cause stress or even substantial annoyance remains an open question. To analyse the stress impact of obstruction markings, we used environmental and stress psychology methodologies. Residents (N=420) with direct sight of turbines at 13 wind farms participated in a questionnaire survey. Evidence of substantial annoyance caused by obstruction markings was not found. However, residents exposed to xenon lights reported more intense and multifaceted stress responses than exposed to LED or colour markings on blades. Moreover, xenon lights negatively affected the general acceptance of wind energy. Additionally, synchronised navigation lights were found to be less annoying than non-synchronised lights under certain weather conditions. Markings with light intensity adjustment proved to be advantageous. To reduce stress and increase social acceptance of wind power, xenon lights should be abandoned, navigation lights synchronised, and light intensity adjustment applied. - Research highlights: ► Wind turbine obstruction markings influence the social acceptance of wind energy. ► Residents exposed to xenon lights reported more intense stress responses than exposed to LED or colour markings. ► Synchronised lights were found to be less annoying under certain weather conditions. ► Markings with light intensity adjustment proved to be advantageous. ► Evidence of substantial annoyance caused by obstruction markings was not found.

  19. Effects of residual stress on fatigue strength of small diameter welded pipe joint

    International Nuclear Information System (INIS)

    Yamashita, Tetsuo; Hattori, Takahiro; Nomoto, Toshiharu; Iida, Kunihiro; Sato, Masanobu

    1996-01-01

    A power plant consists of many welded components, therefore, it is essential in establishing the reliability of the power plant to maintain the reliability of all welded components. The fatigue failure caused by mechanical vibrations of small diameter welded joints, which is represented by socket welded joints, is one of the major causes of trouble for the welded parts of the power plant. Here, bending fatigue tests were conducted to investigate the fatigue strength of small diameter socket welded pipe joints. In the most cases of large diameter socket joints, a fatigue crack started from the root of the fillet weld though the stress amplitude at the root was smaller than that at the toe of fillet weld. Additionally, the fatigue strength was affected by the weld bead sequence. The residual stress was considered to be one of the important parameters governing fatigue strength, therefore, its effects were investigated. In several types of pipe joints, the local stress and residual stress distributions were calculated by finite element analysis. The residual stresses were compressive at the toe and tensile at the root of the socket welded joints. Based on these results, the effects of residual stresses on the fatigue strength are discussed for small diameter welded pipe joints in the present work

  20. Sensitivity of ocean oxygenation to variations in tropical zonal wind stress magnitude

    Science.gov (United States)

    Ridder, Nina N.; England, Matthew H.

    2014-09-01

    Ocean oxygenation has been observed to have changed over the past few decades and is projected to change further under global climate change due to an interplay of several mechanisms. In this study we isolate the effect of modified tropical surface wind stress conditions on the evolution of ocean oxygenation in a numerical climate model. We find that ocean oxygenation varies inversely with low-latitude surface wind stress. Approximately one third of this response is driven by sea surface temperature anomalies; the remaining two thirds result from changes in ocean circulation and marine biology. Global mean O2 concentration changes reach maximum values of +4 μM and -3.6 μM in the two most extreme perturbation cases of -30% and +30% wind change, respectively. Localized changes lie between +92 μM under 30% reduced winds and -56 μM for 30% increased winds. Overall, we find that the extent of the global low-oxygen volume varies with the same sign as the wind perturbation; namely, weaker winds reduce the low-oxygen volume on the global scale and vice versa for increased trade winds. We identify two regions, one in the Pacific Ocean off Chile and the other in the Indian Ocean off Somalia, that are of particular importance for the evolution of oxygen minimum zones in the global ocean.

  1. Effect of residual stresses on fatigue strength of plasma nitrided 4140 steel

    International Nuclear Information System (INIS)

    Aghazadeh, J.; Amidi, M.R.

    2004-01-01

    Almost every method that has been presented to determine residual stress has some limitation and complexities. The aim of this work is to present a new, yet simple method so called strain indentation for measuring the residual stresses particularly in thin layers. In this method in addition to the precision measurements, components of residual stress at different directions may be determined. AISI 4140 steel specimens nitrided at 350 d ig C , 450 d ig C and 550 d ig C for 5 hours in the mixture of 75% nitrogen- 25% hydrogen gas. The, components of residual stress in the radials axial and hoop directions in the nitrided layer were determined considering the elastic strain recovery after removal of residual stress inducer(i.e. the nitrided layer). Fatigue strength of the nitrided specimens was obtained by plotting the S-N curves and fractographic studies carried out on the fracture surface of the specimens. The effect of residual stress on the stress pattern was simulated. The calculated residual stress components were in the range of 40-210 Mpa and the radial components of residual stress were more than the other two directions. Maximum fatigue strength improvement of up to 110% was observed in the plasma nitrided specimens at 550 d ig C and also 40% improvement in fatigue strength was detected by increasing the nitriding temperature from 350 d ig C to 550 d ig C . This was due to 100% increase in residual stress. Fatigue crack growth velocity in the hoop direction was more than that of radial direction. This seems to be due to higher radial residual stress component compared with the hoop stress component in the sub layer

  2. Comparison of Positive Character Strengths in Employees with Healthy and Unhealthy Occupational Stress Coping Styles

    OpenAIRE

    simin dokht kalani; Zahra Zahra; hamidreza oreyzi

    2017-01-01

    The aim of the study was to compare the protective and interpersonal strengths as positive personality traits in employees with healthy (G: good health pattern, S: sparing pattern) and unhealthy (A: ambitious pattern, B: burnout pattern) job stress coping styles. Therefore, 146 employees of an industrial organization in Mashhad were selected by stratified random sampling and asked to respond to research tools. The instruments were the Values in Action Inventory of Strengths from Peterson & Se...

  3. Residual stress stability and alternating bending strength of AISI 4140 after shot peening and successive annealing

    Energy Technology Data Exchange (ETDEWEB)

    Menig, R.; Schulze, V.; Voehringer, O. [Inst. fuer Werkstoffkunde I, Univ. of Karlsruhe (TH), Karlsruhe (Germany)

    2002-07-01

    Increases of residual stress stability and alternating bending strength of shot peened AISI 4140 are obtained by successive annealing treatments. This is caused by static strain aging effects, which lead to pinning of dislocations by carbon atoms and finest carbides. It will be shown that by short-time annealing of a quenched and tempered AISI 4140 it is possible to maximize the positive effect of static strain aging, while minimizing the detrimental effect of thermal residual stress relaxation, which was measured by X-ray diffraction method. Static strain aging effects were also found to be responsible for an increase of the quasi static and cyclic surface yield strengths. (orig.)

  4. Alignment of stress, mean wind, and vertical gradient of the velocity vector

    DEFF Research Database (Denmark)

    Berg, Jacob; Mann, Jakob; Patton, E.G.

    2012-01-01

    In many applications in the atmospheric surface layer the turbulent-viscosity hypothesis is applied, i.e. the stress vector can be described through the vertical gradient of velocity. In the atmospheric surface layer, where the Coriolis force and baroclinic effects are considered negligible......, this is supposedly a good approximation. High resolution large-eddy simulation (LES) data show that it is indeed the case. Through analysis of WindCube lidar measurements accompanied by sonic measurements we show that this is, on the other hand, rarely the case in the real atmosphere. This might indicate that large...... of atmospheric boundary layer modeling. The measurements are from the Danish wind turbine test sites at Høvsøre. With theWindCube lidar we are able to reach heights of 250 meters and hence capture the entire atmospheric surface layer both in terms of wind speed and the direction of the mean stress vector....

  5. An Exploration of Wind Stress Calculation Techniques in Hurricane Storm Surge Modeling

    Directory of Open Access Journals (Sweden)

    Kyra M. Bryant

    2016-09-01

    Full Text Available As hurricanes continue to threaten coastal communities, accurate storm surge forecasting remains a global priority. Achieving a reliable storm surge prediction necessitates accurate hurricane intensity and wind field information. The wind field must be converted to wind stress, which represents the air-sea momentum flux component required in storm surge and other oceanic models. This conversion requires a multiplicative drag coefficient for the air density and wind speed to represent the air-sea momentum exchange at a given location. Air density is a known parameter and wind speed is a forecasted variable, whereas the drag coefficient is calculated using an empirical correlation. The correlation’s accuracy has brewed a controversy of its own for more than half a century. This review paper examines the lineage of drag coefficient correlations and their acceptance among scientists.

  6. The theoretical shear strength of fcc crystals under superimposed triaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Cerny, M., E-mail: cerny.m@fme.vutbr.cz [Institute of Engineering Physics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, CZ-616 69 Brno (Czech Republic); Pokluda, J. [Institute of Engineering Physics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, CZ-616 69 Brno (Czech Republic)

    2010-05-15

    The influence of a triaxial stress applied normally to shear planes and shear direction during affine shear deformation of face-centered cubic crystals on the theoretical shear strength is studied for the <112-bar >{l_brace}111{r_brace} shear system using first-principles methods. The applied relaxation procedure guarantees that the modeled system is subjected to a superposition of shear, normal and in-plane stresses with individually adjustable in-plane and normal stress values. The theoretical shear strengths of individual elements prove to be qualitatively different functions of the superimposed stresses. In the special case of hydrostatic loading, however, these functions are qualitatively uniform. This behavior is discussed in terms of the electronic structure.

  7. Effect of nonlinear stress-strain relationship on bending strength of isotropic graphite

    International Nuclear Information System (INIS)

    Arai, Taketoshi; Oku, Tatsuo

    1978-05-01

    Four-point bending tests were made on rectangular isotropic 7477PT graphite specimens of different sizes to observe the relation between load and outermost fiber strain. Analytical methods, allowing for nonlinear stress-strain relationships different between tension and compression, were developed for calculating the fiber stress distribution in a beam and the failure probability based on the Weibull statistical theory for bending fracture. With increase of the stress, the stress-strain curves for tension deviate from the linearity and also from those for compression. The true bending strengths of the rectangular bars are 10 -- 20 percent lower than elastic bending strengths. Revised Weibull theory gives failure probability distributions agreeing with measured ones, compared with the theory based on elastic behavior. (auth.)

  8. Attachment Strength and Relationship Expectancies in the Prediction of Adolescent Stress and Depression

    Science.gov (United States)

    Goh, Yun Lin Daphne; Wilkinson, Ross B.

    2017-01-01

    Interpersonal relationships are the recent focus of research identifying protective factors in adolescent psychological health. Using an attachment theory perspective, this study examines the relationship of normative attachment strength and individual differences in attachment expectancies on self-reports of depression and stress in 511…

  9. Thermomechanical processing of 5083 aluminum to increase strength without increasing susceptibility to stress corrosion cracking

    International Nuclear Information System (INIS)

    Edstrom, C.M.; Blakeslee, J.J.

    1980-01-01

    5083 aluminium with 25% cold work must be processed above 215 0 C or below 70 0 C to avoid forming continuous precipitate in the grain boundaries which makes the material susceptible to stress corrosion cracking. Time at temperature above 215 0 C should be held to minimum (less than 30 min) to retain some strength from the 25% cold work

  10. Transformation of localized necking of strain space into stress space for advanced high strength steel sheet

    Science.gov (United States)

    Nakwattanaset, Aeksuwat; Suranuntchai, Surasak

    2018-03-01

    Normally, Forming Limit Curves (FLCs) can’t explain for shear fracture better than Damage Curve, this article aims to show the experimental of Forming Limit Curve (FLC) for Advanced High Strength Steel (AHSS) sheets grade JAC780Y with the Nakazima forming test and tensile tests of different sample geometries. From these results, the Forming Limit Curve (strain space) was transformed to damage curve (stress space) between plastic strain and stress triaxiality. Therefore, Stress space transformed using by Hill-48 and von-Mises yield function. This article shows that two of these yield criterions can use in the transformation.

  11. Residual stresses and strength of multilayer tape cast solid oxide fuel and electrolysis half-cells

    DEFF Research Database (Denmark)

    Charlas, Benoit; Frandsen, Henrik Lund; Brodersen, Karen

    2015-01-01

    those with 3 layers (MTC3: without barrier layer). The bending strength of MTC3 and MTC4 under various loading orientations (electrolyte on the tensile or compressive side of the loading) is compared. The analysis, by taking residual stresses into account, shows that the strength of the half...... coefficient (TEC) mismatch between the layers, cumulated from high temperature, induces significant residual stresses in the half-cells. Furthermore, it has been observed that MTC half-cells with 4 layers (MTC4: support, fuel electrode, electrolyte and barrier layer) are sometimes more fragile to handle than...... stresses, especially in the outer barrier-layer, possible changes to the layer properties are discussed and some optimization guidelines proposed....

  12. Rock Strength Anisotropy in High Stress Conditions: A Case Study for Application to Shaft Stability Assessments

    Directory of Open Access Journals (Sweden)

    Watson Julian Matthew

    2015-03-01

    Full Text Available Although rock strength anisotropy is a well-known phenomenon in rock mechanics, its impact on geotechnical design is often ignored or underestimated. This paper explores the concept of anisotropy in a high stress environment using an improved unified constitutive model (IUCM, which can account for more complex failure mechanisms. The IUCM is used to better understand the typical responses of anisotropic rocks to underground mining. This study applies the IUCM to a proposed rock shaft located in high stress/anisotropic conditions. Results suggest that the effect of rock strength anisotropy must be taken into consideration when assessing the rock mass response to mining in high stress and anisotropic rock conditions.

  13. Stress orientations in subduction zones and the strength of subduction megathrust faults.

    Science.gov (United States)

    Hardebeck, Jeanne L

    2015-09-11

    Subduction zone megathrust faults produce most of the world's largest earthquakes. Although the physical properties of these faults are difficult to observe directly, their frictional strength can be estimated indirectly by constraining the orientations of the stresses that act on them. A global investigation of stress orientations in subduction zones finds that the maximum compressive stress axis plunges systematically trenchward, consistently making an angle of 45° to 60° with respect to the subduction megathrust fault. These angles indicate that the megathrust fault is not substantially weaker than its surroundings. Together with several other lines of evidence, this implies that subduction zone megathrusts are weak faults in a low-stress environment. The deforming outer accretionary wedge may decouple the stress state along the megathrust from the constraints of the free surface. Copyright © 2015, American Association for the Advancement of Science.

  14. Satellite Observations of Imprint of Oceanic Current on Wind Stress by Air-Sea Coupling.

    Science.gov (United States)

    Renault, Lionel; McWilliams, James C; Masson, Sebastien

    2017-12-18

    Mesoscale eddies are present everywhere in the ocean and partly determine the mean state of the circulation and ecosystem. The current feedback on the surface wind stress modulates the air-sea transfer of momentum by providing a sink of mesoscale eddy energy as an atmospheric source. Using nine years of satellite measurements of surface stress and geostrophic currents over the global ocean, we confirm that the current-induced surface stress curl is linearly related to the current vorticity. The resulting coupling coefficient between current and surface stress (s τ [N s m -3 ]) is heterogeneous and can be roughly expressed as a linear function of the mean surface wind. s τ expresses the sink of eddy energy induced by the current feedback. This has important implications for air-sea interaction and implies that oceanic mean and mesoscale circulations and their effects on surface-layer ventilation and carbon uptake are better represented in oceanic models that include this feedback.

  15. WIND TURBINES CAUSE CHRONIC STRESS IN BADGERS (MELES MELES) IN GREAT BRITAIN.

    Science.gov (United States)

    Agnew, Roseanna C N; Smith, Valerie J; Fowkes, Robert C

    2016-07-01

    A paucity of data exists with which to assess the effects of wind turbines noise on terrestrial wildlife, despite growing concern about the impact of infrasound from wind farms on human health and well-being. In 2013, we assessed whether the presence of turbines in Great Britain impacted the stress levels of badgers ( Meles meles ) in nearby setts. Hair cortisol levels were used to determine if the badgers were physiologically stressed. Hair of badgers living 10 km from a wind farm. This demonstrates that affected badgers suffer from enhanced hypothalamo-pituitary-adrenal activity and are physiologically stressed. No differences were found between the cortisol levels of badgers living near wind farms operational since 2009 and 2012, indicating that the animals do not become habituated to turbine disturbance. Cortisol levels in the affected badgers did not vary in relation to the distance from turbines within 1 km, wind farm annual power output, or number of turbines. We suggest that the higher cortisol levels in affected badgers is caused by the turbines' sound and that these high levels may affect badgers' immune systems, which could result in increased risk of infection and disease in the badger population.

  16. Strength Analysis of a Large-Size Supporting Structure for an Offshore Wind Turbine

    Directory of Open Access Journals (Sweden)

    Niklas Karol

    2017-04-01

    Full Text Available The offshore wind power industry is the branch of electric energy production from renewable sources which is most intensively developed in EU countries. At present, there is a tendency to install larger-power wind turbines at larger distances from the seashore, on relatively deep waters. Consequently, technological solutions for new supporting structures intended for deeper water regions are undergoing rapid development now. Various design types are proposed and analysed, starting from gravitational supports (GBS, through monopiles and 3D frame structures (jackets, tripods, and ending with floating and submerged supports anchored to the seabed by flexible connectors, including TLP type solutions.

  17. Scales of North Atlantic wind stress curl determined from the comprehensive ocean-atmosphere data set

    Science.gov (United States)

    Ehret, Laura L.; O'Brien, James J.

    1989-01-01

    Nineteen years of wind data over the North Atlantic are used to calculate a field of wind stress curl. An empirical orthogonal function (EOF) analysis is performed on this field, resulting in spatial patterns of wind stress curl and associated time series. A Monte Carlo technique is used to establish the statistical significance of each spatial pattern, and the associated time series are spectrally analyzed. The first four statistically significant EOF modes represent more than 50 percent of the curl variance, and the spatial patterns of curl associated with these modes exhibit the major elements of North Atlantic climatology. Most of the time series spectral variance is contained in annual and semiannual frequencies. The features observed include the individual annual variation of the subtropical high and the subpolar low, the annual oscillation of intensity between pressure centers, the influence of localized strong SST gradients and associated cyclogenesis regions, and the constant nature of the trades.

  18. The Internal Stress Evaluation of Pultruded Blades for a Darrieus Wind Turbine

    DEFF Research Database (Denmark)

    Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

    2013-01-01

    This paper investigates the integrated modeling of a pultruded NACA0018 blade profile which is a part of the FP7 EU project DeepWind. The pultrusion process simulation is combined with the preliminary subsequent in-service load scenario. In particular, the process induced residual stresses...

  19. The Internal Stress Evaluation of Pultruded Blades for a Darrieus Wind Turbine

    NARCIS (Netherlands)

    Baran, Ismet; Tutum, Cem C.; Hattel, Jesper Henri

    2013-01-01

    This paper investigates the integrated modeling of a pultruded NACA0018 blade profile which is a part of the FP7 EU project DeepWind. The pultrusion process simulation is combined with the preliminary subsequent in-service load scenario. In particular, the process induced residual stresses and

  20. Monthly mean wind stress along the coast of the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Shenoi, S.S.C.; Antony, M.K.; Krishnakumar, V.

    Monthly-mean wind stress and its longshore and offshore components have been computed using the bulk aerodynamic method for each of a string of 36 two-degree-latitude by two-degree-longitude squares along the coast of the north Indian Ocean...

  1. TropFlux wind stresses over the tropical oceans: Evaluation and comparison with other products

    Digital Repository Service at National Institute of Oceanography (India)

    PraveenKumar, B.; Vialard, J.; Lengaigne, M.; Murty, V.S.N.; McPhaden, M.J.; Cronin, M.F.; Pinsard, F.; Reddy, K.G.

    Convergence Zones. ERA-I and TropFlux display the best agreement with in situ data, with correlations more than 0.93 and rms-differences less than 0.012 Nm sup(-2). TropFlux wind stresses exhibit a small, but consistent improvement (at all timescales and most...

  2. Initialization shock in decadal hindcasts due to errors in wind stress over the tropical Pacific

    Science.gov (United States)

    Pohlmann, Holger; Kröger, Jürgen; Greatbatch, Richard J.; Müller, Wolfgang A.

    2017-10-01

    Low prediction skill in the tropical Pacific is a common problem in decadal prediction systems, especially for lead years 2-5 which, in many systems, is lower than in uninitialized experiments. On the other hand, the tropical Pacific is of almost worldwide climate relevance through its teleconnections with other tropical and extratropical regions and also of importance for global mean temperature. Understanding the causes of the reduced prediction skill is thus of major interest for decadal climate predictions. We look into the problem of reduced prediction skill by analyzing the Max Planck Institute Earth System Model (MPI-ESM) decadal hindcasts for the fifth phase of the Climate Model Intercomparison Project and performing a sensitivity experiment in which hindcasts are initialized from a model run forced only by surface wind stress. In both systems, sea surface temperature variability in the tropical Pacific is successfully initialized, but most skill is lost at lead years 2-5. Utilizing the sensitivity experiment enables us to pin down the reason for the reduced prediction skill in MPI-ESM to errors in wind stress used for the initialization. A spurious trend in the wind stress forcing displaces the equatorial thermocline in MPI-ESM unrealistically. When the climate model is then switched into its forecast mode, the recovery process triggers artificial El Niño and La Niña events at the surface. Our results demonstrate the importance of realistic wind stress products for the initialization of decadal predictions.

  3. Impacts of Wind Stress Changes on the Global Heat Transport, Baroclinic Instability, and the Thermohaline Circulation

    Directory of Open Access Journals (Sweden)

    Jeferson Prietsch Machado

    2016-01-01

    Full Text Available The wind stress is a measure of momentum transfer due to the relative motion between the atmosphere and the ocean. This study aims to investigate the anomalous pattern of atmospheric and oceanic circulations due to 50% increase in the wind stress over the equatorial region and the Southern Ocean. In this paper we use a coupled climate model of intermediate complexity (SPEEDO. The results show that the intensification of equatorial wind stress causes a decrease in sea surface temperature in the tropical region due to increased upwelling and evaporative cooling. On the other hand, the intensification of wind stress over the Southern Ocean induces a regional increase in the air and sea surface temperatures which in turn leads to a reduction in Antarctic sea ice thickness. This occurs in association with changes in the global thermohaline circulation strengthening the rate of Antarctic Bottom Water formation and a weakening of the North Atlantic Deep Water. Moreover, changes in the Southern Hemisphere thermal gradient lead to modified atmospheric and oceanic heat transports reducing the storm tracks and baroclinic activity.

  4. The Inclusion of Arbitrary Load Histories in the Strength Decay Model for Stress Rupture

    Science.gov (United States)

    Reeder, James R.

    2014-01-01

    Stress rupture is a failure mechanism where failures can occur after a period of time, even though the material has seen no increase in load. Carbon/epoxy composite materials have demonstrated the stress rupture failure mechanism. In a previous work, a model was proposed for stress rupture of composite overwrap pressure vessels (COPVs) and similar composite structures based on strength degradation. However, the original model was limited to constant load periods (holds) at constant load. The model was expanded in this paper to address arbitrary loading histories and specifically the inclusions of ramp loadings up to holds and back down. The broadening of the model allows for failures on loading to be treated as any other failure that may occur during testing instead of having to be treated as a special case. The inclusion of ramps can also influence the length of the "safe period" following proof loading that was previously predicted by the model. No stress rupture failures are predicted in a safe period because time is required for strength to decay from above the proof level to the lower level of loading. Although the model can predict failures during the ramp periods, no closed-form solution for the failure times could be derived. Therefore, two suggested solution techniques were proposed. Finally, the model was used to design an experiment that could detect the difference between the strength decay model and a commonly used model for stress rupture. Although these types of models are necessary to help guide experiments for stress rupture, only experimental evidence will determine how well the model may predict actual material response. If the model can be shown to be accurate, current proof loading requirements may result in predicted safe periods as long as 10(13) years. COPVs design requirements for stress rupture may then be relaxed, allowing more efficient designs, while still maintaining an acceptable level of safety.

  5. Fatigue life prediction and strength degradation of wind turbine rotor blade composites

    NARCIS (Netherlands)

    Nijssen, R.P.L.

    2006-01-01

    Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude

  6. Fractographic investigation of stress corrosion cracking of steels for high-strength bolts

    International Nuclear Information System (INIS)

    Gladshtejn, L.I.; Goritskij, V.M.; Evtushenko, N.A.; Sokolov, S.P.; Panfilova, L.M.

    1980-01-01

    By the methods of quantitative fractography studied is the effect of chemical composition on stress corrosion cracking resistance in the mean agressive medium (pH=2.2) and the fracture structure of cylindrical delta samples with the notch (K=2.75) of high-strength chromium steel. It is shown that the alloying of the 40 steel with Cr, Si, V increases its strength under short-time loading but leads to forming of brittle areas in fracture under long time effect of corrosion medium

  7. Variability of wind stress and currents at selected locations over the north Indian Ocean during 1977 and 1979 summer monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Sadhuram, Y.; RameshBabu, V.; Rao, M.V.

    Intra-seasonal variability of wind stress, wind stress curl and currents at different locations over the northern Indian Ocean during two contrasting monsoon seasons has been investigated making use of the time series data collected during MONSOON...

  8. Analysis of Mechanical Stresses Due to Voltage Dips in Fixed-Speed Wind Turbines

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2011-01-01

    stresses transients that may have a detrimental effect on the fatigue life of drivetrain system due to voltage dips. A rainflow cycle counting method for the stress history during the voltage dip event, analyses mean and amplitudes of the counted cycles, their occurrence moment and time of duration.......Voltage dips due to electrical grid faults generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system. These events may also have a detrimental effect on the fatigue life of important...

  9. Fatigue strength evaluation of friction stir welded aluminium joints using the nominal and notch stress concepts

    International Nuclear Information System (INIS)

    Barsoum, Z.; Khurshid, M.; Barsoum, I.

    2012-01-01

    Highlights: ► Fatigue testing and evaluation of friction stir welded butt and overlap joints. ► Evaluation based on nominal and effective notch stress concept. ► Comparison with different design recommendations and codes. ► Higher fatigue strength and SN-slopes is observed. ► New fatigue design recommendations proposed for FSW joints. -- Abstract: In this study the fatigue strength is investigated for Friction Stir Welded (FSW) overlap and butt welded joints in different thicknesses based on nominal and effective notch stress concepts. The fatigue test results are compared with fatigue strength recommendations according to EN 1999-1-3 and International Institute of Welding (IIW). The results are also compared with available published data and Finite Element Analysis (FEA) is carried out to investigate the effect of plate thickness and nugget size on the fatigue strength of overlap joints. 3–3 mm butt welded joints shows the highest fatigue strength in comparison with 3–5 mm butt welded and overlap joints. Slopes of the SN-curves for two different joint types differ from the slope recommended by IIW. A specific failure trend is observed in overlap FSW joints. However, the slopes of the SN-curves are in close agreement with slopes found in EN 1999-1-3. The slopes of various published results and test results presented in this study are in good agreement with each other. The suggested fatigue design curves for the nominal and effective notch stress concept have a higher slope than given for fusion welds by IIW.

  10. Stress-strain relationship of high-strength steel (HSS) reinforcing bars

    Science.gov (United States)

    Anggraini, Retno; Tavio, Raka, I. Gede Putu; Agustiar

    2018-05-01

    The introduction of High-Strength Steel (HSS) reinforcing bars in reinforced concrete members has gained much attention in recent years and led to many advantages such as construction timesaving. It is also more economical since it can reduce the amount of reinforcing steel bars used in concrete members which in turn alleviates the congestion of reinforcement. Up to present, the building codes, e.g. American Concrete Institute (ACI) 318M-14 and Standard National Indonesia (SNI) 2847:2013, still restrict the use of higher-strength steel reinforcing bars for concrete design up to Grade 420 MPa due to the possible suspected brittle behavior of concrete members. This paper evaluates the characteristics of stress-strain relationships of HSS bars if they are comparable to the characteristics of those of Grade 420 MPa. To achieve the objective of the study, a series of steel bars from various grades (420, 550, 650, and 700 MPa) was selected. Tensile tests of these steel samples were conducted under displacement-controlled mode to capture the complete stress-strain curves and particularly the post-yield response of the steel bars. The results indicate that all the steel bars tested had the actual yield strengths greater than the corresponding specified values. The stress-strain curves of HSS reinforcing bars (Grade 550, 650, and 700 MPa) performed slightly different characteristics with those of Grade 420 MPa.

  11. Implementation of a Stress-dependent Strength Material Model in PLAXIS 3D

    DEFF Research Database (Denmark)

    Knudsen, Bjørn S.; Østergaard, Martin Underlin; Clausen, Johan

    To perform tests on bucket foundations, full-scale testing is rarely used since it is rather expensive. Instead small-scale testing is done to examine the static and dynamic behaviour of such structures. In the laboratory at Aalborg University, small-scale testing of offshore support structures can...... be performed in a pressure tank, where a pressure can be applied in order to simulate deep water situations. Since the test set-up is downscaled 15 to 30 times compared to real-life structures, stresses and strains will be downscaled too. For soils, normally a Mohr-Coulomb failure criterion is used......, and in the region of small stresses, a non-linear behaviour is observed - unlike the linear behaviour normally assumed in Mohr-Coulomb. To better model this non-linearity, a stress-dependent model for the strength of the soil material is sought to be implemented in PLAXIS 3D through FORTRAN to improve...

  12. Sandblasting induced stress release and enhanced adhesion strength of diamond films deposited on austenite stainless steel

    Science.gov (United States)

    Li, Xiao; Ye, Jiansong; Zhang, Hangcheng; Feng, Tao; Chen, Jianqing; Hu, Xiaojun

    2017-08-01

    We firstly used sandblasting to treat austenite stainless steel and then deposited a Cr/CrN interlayer by close field unbalanced magnetron sputtering on it. After that, diamond films were prepared on the interlayer. It is found that the sandblasting process induces phase transition from austenite to martensite in the surface region of the stainless steel, which decreases thermal stress in diamond films due to lower thermal expansion coefficient of martensite phase compared with that of austenite phase. The sandblasting also makes stainless steel's surface rough and the Cr/CrN interlayer film inherits the rough surface. This decreases the carburization extent of the interlayer, increases nucleation density and modifies the stress distribution. Due to lower residual stress and small extent of the interlayer's carburization, the diamond film on sandblast treated austenite stainless steel shows enhanced adhesion strength.

  13. A marker of biological age explains individual variation in the strength of the adult stress response.

    Science.gov (United States)

    Andrews, Clare; Nettle, Daniel; Larriva, Maria; Gillespie, Robert; Reichert, Sophie; Brilot, Ben O; Bedford, Thomas; Monaghan, Pat; Spencer, Karen A; Bateson, Melissa

    2017-09-01

    The acute stress response functions to prioritize behavioural and physiological processes that maximize survival in the face of immediate threat. There is variation between individuals in the strength of the adult stress response that is of interest in both evolutionary biology and medicine. Age is an established source of this variation-stress responsiveness diminishes with increasing age in a range of species-but unexplained variation remains. Since individuals of the same chronological age may differ markedly in their pace of biological ageing, we asked whether biological age-measured here via erythrocyte telomere length-predicts variation in stress responsiveness in adult animals of the same chronological age. We studied two cohorts of European starlings in which we had previously manipulated the rate of biological ageing by experimentally altering the competition experienced by chicks in the fortnight following hatching. We predicted that individuals with greater developmental telomere attrition, and hence greater biological age, would show an attenuated corticosterone (CORT) response to an acute stressor when tested as adults. In both cohorts, we found that birds with greater developmental telomere attrition had lower peak CORT levels and a more negative change in CORT levels between 15 and 30 min following stress exposure. Our results, therefore, provide strong evidence that a measure of biological age explains individual variation in stress responsiveness: birds that were biologically older were less stress responsive. Our results provide a novel explanation for the phenomenon of developmental programming of the stress response: observed changes in stress physiology as a result of exposure to early-life adversity may reflect changes in ageing.

  14. Four-Point Bending Strength Testing of Pultruded Fiberglass Composite Wind Turbine Blade Sections

    International Nuclear Information System (INIS)

    Musial, W.; Bourne, B; Hughes, S; Zuteck, M. D.

    2001-01-01

    The ultimate strength of the PS Enterprises pultruded blade section was experimentally determined under four-point bending at the National Renewable Energy Laboratory. Thirteen 8-foot long full-scale blade segments were individually tested to determine their maximum moment carrying capability. Three airfoil-bending configurations were tested: high- and low-pressure skin buckling, and low pressure skin buckling with foam interior reinforcement. Maximum strain was recorded for each sample on the compressive and tensile surfaces of each test blade. Test data are compared to the results of three analytical buckling prediction methods. Based on deviations from the linear strain versus load curve, data indicate a post-buckling region. High-pressure side buckling occurred sooner than low-pressure side buckling. The buckling analyses were conservative for both configurations, but high-pressure side buckling in particular was substantially under-predicted. Both high- and low-pressure buckling configurations had very similar failure loads. These results suggests that a redundant load path may be providing strength to the section in the post-buckling region, making the onset of panel buckling a poor predictor of ultimate strength for the PS Enterprises pultrusion

  15. Macro-mesoscopic Fracture and Strength Character of Pre-cracked Granite Under Stress Relaxation Condition

    Science.gov (United States)

    Liu, Junfeng; Yang, Haiqing; Xiao, Yang; Zhou, Xiaoping

    2018-05-01

    The fracture characters are important index to study the strength and deformation behavior of rock mass in rock engineering. In order to investigate the influencing mechanism of loading conditions on the strength and macro-mesoscopic fracture character of rock material, pre-cracked granite specimens are prepared to conduct a series of uniaxial compression experiments. For parts of the experiments, stress relaxation tests of different durations are also conducted during the uniaxial loading process. Furthermore, the stereomicroscope is adopted to observe the microstructure of the crack surfaces of the specimens. The experimental results indicate that the crack surfaces show several typical fracture characters in accordance with loading conditions. In detail, some cleavage fracture can be observed under conventional uniaxial compression and the fractured surface is relatively rough, whereas as stress relaxation tests are attached, relative slip trace appears between the crack faces and some shear fracture starts to come into being. Besides, the crack faces tend to become smoother and typical terrace structures can be observed in local areas. Combining the macroscopic failure pattern of the specimens, it can be deduced that the duration time for the stress relaxation test contributes to the improvement of the elastic-plastic strain range as well as the axial peak strength for the studied material. Moreover, the derived conclusion is also consistent with the experimental and analytical solution for the pre-peak stage of the rock material. The present work may provide some primary understanding about the strength character and fracture mechanism of hard rock under different engineering environments.

  16. Response of the Benguela upwelling systems to spatial variations in the wind stress

    Science.gov (United States)

    Fennel, Wolfgang; Junker, Tim; Schmidt, Martin; Mohrholz, Volker

    2012-08-01

    In this paper we combine field observations, numerical modeling and an idealized analytical theory to study some features of the Benguela upwelling system. The current system can be established through a combination of observations and realistic simulations with an advanced numerical model. The poleward undercurrent below the equator-ward coastal jet is often found as a countercurrent that reaches the sea surface seaward of the coastal jet. The coastal band of cold upwelled water appears to broaden from south to north and at the northern edge of the wind band an offshore flow is often detected, which deflects the coastal Angola current to the west. These features can be explained and understood with an idealized analytical model forced by a spatially variable wind. A crucial role is played by the wind stress curl, which shapes the oceanic response through Ekman-pumping. The interplay of the curl driven effects and the coastal Ekman upwelling together with the coastal jet, Kelvin waves, and the undercurrent is the key to understand the formation of the three-dimensional circulation patterns in the Benguela system. While the numerical model is based on the full set of primitive equations, realistic topography and forcing, the analytic model uses a linear, flat-bottomed f-plane ocean, where the coast is a straight wall and the forcing is represented by an alongshore band of dome-shaped wind stress. Although the analytical model is highly idealized it is very useful to grasp the basic mechanisms leading to the response patterns.

  17. The direct-stress fatigue strength of 17S-T aluminum alloy throughout the range from 1/2 to 500,000,000 cycles of stress

    Science.gov (United States)

    Hartmann, E C; Stickley, G W

    1942-01-01

    Fatigue-test were conducted on six specimens made from 3/4-inch-diameter 17S-T rolled-and-drawn rod for the purpose of obtaining additional data on the fatigue life of the material at stresses up to the static strength. The specimens were tested in direct tension using a stress range from zero to a maximum in tension. A static testing machine was used to apply repeated loads in the case of the first three specimens; the other three specimens were tested in a direct tension-compression fatigue machine. The direct-stress fatigue curve obtained for the material indicates that, in the range of stresses above about two-thirds the tensile strength, the fatigue strength is higher than might be expected by simply extrapolating the ordinary curve of stress plotted against the number of cycles determined at lower stresses.

  18. True Triaxial Strength and Failure Modes of Cubic Rock Specimens with Unloading the Minor Principal Stress

    Science.gov (United States)

    Li, Xibing; Du, Kun; Li, Diyuan

    2015-11-01

    True triaxial tests have been carried out on granite, sandstone and cement mortar using cubic specimens with the process of unloading the minor principal stress. The strengths and failure modes of the three rock materials are studied in the processes of unloading σ 3 and loading σ 1 by the newly developed true triaxial test system under different σ 2, aiming to study the mechanical responses of the rock in underground excavation at depth. It shows that the rock strength increases with the raising of the intermediate principal stress σ 2 when σ 3 is unloaded to zero. The true triaxial strength criterion by the power-law relationship can be used to fit the testing data. The "best-fitting" material parameters A and n ( A > 1.4 and n plastic deformation. The maximum extension strain criterion Stacey (Int J Rock Mech Min Sci Geomech Abstr 651 18(6):469-474, 1981) can be used to explain the change of failure mode from shear to slabbing for strong and hard rocks under true triaxial unloading test condition.

  19. Intercomparison of the Charnock and COARE bulk wind stress formulations for coastal ocean modelling

    Directory of Open Access Journals (Sweden)

    J. M. Brown

    2013-08-01

    Full Text Available The accurate parameterisation of momentum and heat transfer across the air–sea interface is vital for realistic simulation of the atmosphere–ocean system. In most modelling applications accurate representation of the wind stress is required to numerically reproduce surge, coastal ocean circulation, surface waves, turbulence and mixing. Different formulations can be implemented and impact the accuracy of the instantaneous and long-term residual circulation, the surface mixed layer, and the generation of wave-surge conditions. This, in turn, affects predictions of storm impact, sediment pathways, and coastal resilience to climate change. The specific numerical formulation needs careful selection to ensure the accuracy of the simulation. Two wind stress parameterisations widely used in the ocean circulation and the storm surge communities respectively are studied with focus on an application to the NW region of the UK. Model–observation validation is performed at two nearshore and one estuarine ADCP (acoustic Doppler current profiler stations in Liverpool Bay, a hypertidal region of freshwater influence (ROFI with vast intertidal areas. The period of study covers both calm and extreme conditions to test the robustness of the 10 m wind stress component of the Coupled Ocean–Atmosphere Response Experiment (COARE bulk formulae and the standard Charnock relation. In this coastal application a realistic barotropic–baroclinic simulation of the circulation and surge elevation is set-up, demonstrating greater accuracy occurs when using the Charnock relation, with a constant Charnock coefficient of 0.0185, for surface wind stress during this one month period.

  20. Investigation of residual stresses in thick-walled vessels with combination of autofrettage and wire-winding

    International Nuclear Information System (INIS)

    Sedighi, M.; Jabbari, A.H.

    2013-01-01

    Wire-winding and autofrettage processes can be used to introduce beneficial residual stress in the cylinder of thick-walled pressure vessels. In both techniques, internal residual compressive stress will increase internal pressure capacity, improve fatigue life and reduce fatigue crack initiation. The purpose of this paper is to analyze the effects of wire-winding on an autofrettaged thick-walled vessel. Direct method which is a modified Variable Material Properties (VMP) method has been used in order to calculate residual stresses in an autofrettaged vessel. Since wire-winding is done after autofrettage process, the tangent and/or Young's modulus could be changed. For this reason, a new wire-winding method based on Direct Method is introduced. The obtained results for wire-wound autofrettaged vessels are validated by finite element method. The results show that by using this approach, the residual hoop stresses in a wire-wound autofrettaged vessel have a more desirable distribution in the cylinder. -- Highlights: • Combination of autofrettage and wire-winding in pressure vessels has been presented. • A new method based on Direct method is presented for wire-winding process. • Residual hoop stresses are compared in vessels cylinders for different cases. • The residual hoop stress has a more desirable stress distribution. • The benefits of the combined vessel are highlighted in comparison with single cases

  1. Adding insult to injury: The development of psychosocial stress in Ontario wind turbine communities.

    Science.gov (United States)

    Walker, Chad; Baxter, Jamie; Ouellette, Danielle

    2015-05-01

    Though historically dismissed as not-in-my-backyard (NIMBY) attitudes, reports of psychosocial stress linked to wind energy developments have emerged in Ontario, Canada. While the debate and rhetoric intensify concerning whether wind turbines 'actually' cause 'health' effects, less sincere attention has been given to the lived experience and mental well-being of those near turbines. Drawing on theories of environmental stress, this grounded theory, mixed-method (n = 26 interviews; n = 152 questionnaires) study of two communities in 2011 and 2012 traces how and why some wind turbine community residents suffer substantial changes to quality of life, develop negative perceptions of 'the other' and in some cases, experience intra-community conflict. Policy-related forces, along with existing community relationships may help explain much of these differences between communities. We suggest a move beyond debating simply whether or not 'annoyance' represents a 'health impact' and instead focus on ways to minimize and attenuate these feelings of threat (risk) and stress at the community level. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Fractures in high-strength bolts due to hydrogen induced stress corrosion. Causes and corrective actions

    International Nuclear Information System (INIS)

    Hoche, Holger; Oechsner, Matthias

    2017-01-01

    Delayed brittle fractures of high-strength bolts of the strength class 10.9 are presented, taking the example of three damage cases. The respective damage mechanisms could be attributed to hydrogen induced stress corrosion which was caused, in turn, by hydrogen absorption during operation. The examples were chosen with a particular focus on the material condition's susceptibility which explains the cause for the occurrence of the damage mechanism. However, in only one of the three cases the susceptibility was evident and could be explained by violations of normative specifications and an unfavorable material choice. Whereas in the two other examples, only slight or no deviations from the standards and/or regulations could be found. The influencing parameters that caused the damage, those that further promoted the damage, as well as possible corrective actions are discussed taking into account the three exemplary damage cases.

  3. Bayesian and Classical Estimation of Stress-Strength Reliability for Inverse Weibull Lifetime Models

    Directory of Open Access Journals (Sweden)

    Qixuan Bi

    2017-06-01

    Full Text Available In this paper, we consider the problem of estimating stress-strength reliability for inverse Weibull lifetime models having the same shape parameters but different scale parameters. We obtain the maximum likelihood estimator and its asymptotic distribution. Since the classical estimator doesn’t hold explicit forms, we propose an approximate maximum likelihood estimator. The asymptotic confidence interval and two bootstrap intervals are obtained. Using the Gibbs sampling technique, Bayesian estimator and the corresponding credible interval are obtained. The Metropolis-Hastings algorithm is used to generate random variates. Monte Carlo simulations are conducted to compare the proposed methods. Analysis of a real dataset is performed.

  4. A Simplified Model for the Effect of Weld-Induced Residual Stresses on the Axial Ultimate Strength of Stiffened Plates

    Science.gov (United States)

    Chen, Bai-Qiao; Guedes Soares, C.

    2018-03-01

    The present work investigates the compressive axial ultimate strength of fillet-welded steel-plated ship structures subjected to uniaxial compression, in which the residual stresses in the welded plates are calculated by a thermo-elasto-plastic finite element analysis that is used to fit an idealized model of residual stress distribution. The numerical results of ultimate strength based on the simplified model of residual stress show good agreement with those of various methods including the International Association of Classification Societies (IACS) Common Structural Rules (CSR), leading to the conclusion that the simplified model can be effectively used to represent the distribution of residual stresses in steel-plated structures in a wide range of engineering applications. It is concluded that the widths of the tension zones in the welded plates have a quasi-linear behavior with respect to the plate slenderness. The effect of residual stress on the axial strength of the stiffened plate is analyzed and discussed.

  5. Investigation of smooth specimen scc test procedures; variations in environment, specimen size, stressing frame, and stress state. [for high strength aluminum alloys

    Science.gov (United States)

    Lifka, B. W.; Sprowls, D. O.; Kelsey, R. A.

    1975-01-01

    The variables studied in the stress-corrosion cracking performance of high strength aluminum alloys were: (1) corrosiveness of the environment, (2) specimen size and stiffness of the stressing system, (3) interpretation of transgranular cracking, and (4) interaction of the state of stress and specimen orientation in a product with an anisotropic grain structure. It was shown that the probability of failure and time to fracture for a specimen loaded in direct tension are influenced by corrosion pattern, the stressing assembly stiffness, and the notch tensile strength of the alloy. Results demonstrate that the combination of a normal tension stress and a shear stress acting on the plane of maximum susceptibility in a product with a highly directional grain cause the greatest tendency for stress-corrosion cracking.

  6. Mechanical strength calculation of the disk type windings with elastic couplings by the finite element method

    International Nuclear Information System (INIS)

    Sivkova, G.N.; Spirchenko, Yu.V.; Chvartatskij, P.V.

    1981-01-01

    Stressed-deformed state of toroidal field coils of the disc type with elastic couplings of the tokamaks has been investigated with provision for the effect of the central core pliability by means of the two-dimensional version of the finite element method. Numerical solution of the finite element method is performed by means of the ES 1040 computer according to the computer code permitting taking account of boundary conditions of elastic support. The calculation has been performed using as the example the project of T-20 facility coil of the disc type. Consideration of pliability of the central core of the facility inductor is accomplished by the introduction of additional rigidities to the complete matrix of rigidity. Scheme of the structure distretization includes 141 units, 211 elements. The accuracy of solution depends on the reduction accuracy of the volume load to unit forces and on the number of finite elements. Analysis of the solution convergence is performed by the comparison of solutions obtained for three different schemes of the disk discretization without regard for the inductor pliability. The comparative analysis of the results shows that transfer epures for all the three discretization versions practically coincide and stresses differ not more than by 10%. On the whole the above investigation has demonstrated good convergence of the problem solution [ru

  7. Turbulent Reynolds stress and quadrant event activity in wind flow over a coastal foredune

    Science.gov (United States)

    Chapman, Connie A.; Walker, Ian J.; Hesp, Patrick A.; Bauer, Bernard O.; Davidson-Arnott, Robin G. D.

    2012-05-01

    Recent research on quasi-instantaneous turbulent kinematic Reynolds stresses (RS, - u'w') and decomposed quadrant event activity (e.g., ejections and sweeps) over dunes in fluvial settings and in wind tunnels has shown that turbulent stresses at the toe of a dune often exceed time-averaged, streamwise shear stress (ρ u * 2) estimates. It is believed that semi-coherent turbulent structures are conveyed toward the bed along concave streamlines in this region and that impact of these structures cause fluctuations in local surface stresses that assist in grain entrainment. This has been hypothesized to explain how sand is supplied to the windward slope through a region of flow stagnation. Toward the crest, surface stress increases and becomes dominated by streamwise accelerations resulting from streamline compression and convexity that suppress vertical motions. High-frequency (32 Hz) measurements of turbulent wind flow from 3-D ultrasonic anemometers are analyzed for oblique onshore flow over a vegetated coastal foredune in Prince Edward Island, Canada. Reynolds stress and quadrant activity distributions varied with height (0.60 m and 1.66 m) and location over the dune. In general, quadrant 2 ejection (u' 0) and quadrant 4 sweep activity (u' > 0, w' 0, w' > 0) and quadrant 3 inward interaction (u' dune and may help to explain sand transport potential and dune maintenance. For example, areas with a high frequency of ejection and sweep activity may have higher rates of sediment entrainment and transport, whereas areas with lower ejection and sweep activity and an increase in outward and inward interactions, which contribute negatively to Reynolds stress generation, may experience a greater potential for deposition. Further research on associations between quadrant event activity and coincident sand transport is required to confirm this hypothesis and the resultant significance of the flow exuberance effect in aeolian dune morphodynamics.

  8. Fatigue Behavior of Steel Fiber Reinforced High-Strength Concrete under Different Stress Levels

    Science.gov (United States)

    Zhang, Chong; Gao, Danying; Gu, Zhiqiang

    2017-12-01

    The investigation was conducted to study the fatigue behavior of steel fiber reinforced high-strength concrete (SFRHSC) beams. A series of 5 SFRHSC beams was conducted flexural fatigue tests at different stress level S of 0.5, 0.55, 0.6, 0.7 and 0.8 respectively. Static test was conducted to determine the ultimate static capacity prior to fatigue tests. Fatigue modes and S-N curves were analyzed. Besides, two fatige life prediction model were analyzed and compared. It was found that stress level S significantly influenced the fatigue life of SFRHSC beams and the fatigue behavior of SFRHSC beams was mainly determined by the tensile reinforcement.

  9. Ankle and toe muscle strength characteristics in runners with a history of medial tibial stress syndrome.

    Science.gov (United States)

    Saeki, Junya; Nakamura, Masatoshi; Nakao, Sayaka; Fujita, Kosuke; Yanase, Ko; Morishita, Katsuyuki; Ichihashi, Noriaki

    2017-01-01

    A high proportion of flexor digitorum longus attachment is found at the posteromedial border of the tibia, which is the most common location of medial tibial stress syndrome (MTSS). Therefore, plantar flexion strength of the lesser toes could be related to MTSS; however, the relationship between MTSS and muscle strength of the hallux and lesser toes is not yet evaluated due to the lack of quantitative methods. This study investigated the muscle strength characteristics in runners with a history of MTSS by using a newly developed device to measure the muscle strength of the hallux, lesser toes, and ankle. This study comprised 27 collegiate male runner participants (20.0 ± 1.6 years, 172.1 ± 5.1 cm, 57.5 ± 4.0 kg). Maximal voluntary isometric contraction (MVIC) torque of the plantar flexion, dorsiflexion, inversion, and eversion of the ankle were measured by using an electric dynamometer. MVIC torque of the 1st metatarsophalangeal joint (MTPJ) and 2nd-5th MTPJ were measured by using a custom-made torque-measuring device. MVIC torques were compared between runners with and without a history of MTSS. MVIC torque of the 1st MTPJ plantar flexion was significantly higher in runners with a history of MTSS than in those without it. In contrast, there were no significant differences in the MVIC torque values of the 2nd-5th MTPJ plantar flexion and each MVIC torque of the ankle between runners with and without a history of MTSS. A history of MTSS increased the isometric FHL strength.

  10. Influence of Wind Strength and Duration on Relative Hypoxia Reductions by Opposite Wind Directions in an Estuary with an Asymmetric Channel

    Directory of Open Access Journals (Sweden)

    Ping Wang

    2016-09-01

    Full Text Available Computer model experiments are applied to analyze hypoxia reductions for opposing wind directions under various speeds and durations in the north–south oriented, two-layer-circulated Chesapeake estuary. Wind’s role in destratification is the main mechanism in short-term reduction of hypoxia. Hypoxia can also be reduced by wind-enhanced estuarine circulation associated with winds that have down-estuary straining components that promote bottom-returned oxygen-rich seawater intrusion. The up-bay-ward along-channel component of straining by the southerly or easterly wind induces greater destratification than the down-bay-ward straining by the opposite wind direction, i.e., northerly or westerly winds. While under the modulation of the west-skewed asymmetric cross-channel bathymetry in the Bay’s hypoxic zone, the westward cross-channel straining by easterly or northerly winds causes greater destratification than its opposite wind direction. The wind-induced cross-channel circulation can be completed much more rapidly than the wind-induced along-channel circulation, and the former is usually more effective than the latter in destratification and hypoxia reduction in an early wind period. The relative importance of cross-channel versus along-channel circulation for a particular wind direction can change with wind speed and duration. The existence of month-long prevailing unidirectional winds in the Chesapeake is explored, and the relative hypoxia reductions among different prevailing directions are analyzed. Scenarios of wind with intermittent calm or reversing directions on an hourly scale are also simulated and compared.

  11. Elevated stress hormone diminishes the strength of female preferences for acoustic signals in the green treefrog.

    Science.gov (United States)

    Davis, A Gabriell; Leary, Christopher J

    2015-03-01

    Mate selection can be stressful; time spent searching for mates can increase predation risk and/or decrease food consumption, resulting in elevated stress hormone levels. Both high predation risk and low food availability are often associated with increased variation in mate choice by females, but it is not clear whether stress hormone levels contribute to such variation in female behavior. We examined how the stress hormone corticosterone (CORT) affects female preferences for acoustic signals in the green treefrog, Hyla cinerea. Specifically, we assessed whether CORT administration affects female preferences for call rate - an acoustic feature that is typically under directional selection via mate choice by females in most anurans and other species that communicate using acoustic signals. Using a dual speaker playback paradigm, we show that females that were administered higher doses of CORT were less likely to choose male advertisement calls broadcast at high rates. Neither CORT dose nor level was related to the latency of female phonotactic responses, suggesting that elevated CORT does not influence the motivation to mate. Results were also not related to circulating sex steroids (i.e., progesterone, androgens or estradiol) that have traditionally been the focus of studies examining the hormonal basis for variation in female mate choice. Our results thus indicate that elevated CORT levels decrease the strength of female preferences for acoustic signals. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Laterality strength is linked to stress reactivity in Port Jackson sharks (Heterodontus portusjacksoni).

    Science.gov (United States)

    Byrnes, Evan E; Vila Pouca, Catarina; Brown, Culum

    2016-05-15

    Cerebral lateralization is an evolutionarily deep-rooted trait, ubiquitous among the vertebrates and present even in some invertebrates. Despite the advantages of cerebral lateralization in enhancing cognition and facilitating greater social cohesion, large within population laterality variation exists in many animal species. It is proposed that this variation is maintained due links with inter-individual personality trait differences. Here we explored for lateralization in Port Jackson sharks (Heterodontus portusjacksoni) using T-maze turn and rotational swimming tasks. Additionally, we explored for a link between personality traits, boldness and stress reactivity, and cerebral lateralization. Sharks demonstrated large individual and sex biased laterality variation, with females demonstrating greater lateralization than males overall. Stress reactivity, but not boldness, was found to significantly correlate with lateralization strength. Stronger lateralized individuals were more reactive to stress. Demonstrating laterality in elasmobranchs for the first time indicates ancient evolutionary roots of vertebrate lateralization approximately 240 million years old. Greater lateralization in female elasmobranchs may be related enhancing females' ability to process multiple stimuli during mating, which could increase survivability and facilitate insemination. Despite contrasting evidence in teleost fishes, the results of this study suggest that stress reactivity, and other personality traits, may be linked to variation in lateralization. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Study of flow stress and spall strength of additively manufactured Ti-6-4 alloy

    Science.gov (United States)

    Cohen, Amitay; Paris, Vitaly; Yosef-Hai, Arnon; Gudinetsky, Eli; Tiferet, Eitan

    2017-06-01

    The use of additive manufacturing (AM) by Electron Beam Melting (EBM) or Selective Laser Melting (SLM) has extensively grown in the past few years. A major goal in AM is to manufacture materials with mechanical properties at least as good as traditionally manufactured materials. In this work we present results of planar impact tests and Split Hopkinson Pressure Bar tests (SHPB) on Ti-6-4 manufactured by EBM and SLM processes. Results of planar impact tests on SLM samples display slightly higher spall strength compared to EBM while the stress at Hugoniot elastic limit (HEL) is practically the same. Stress strain curves based on SHPB measurements at two different strain rates present similar plastic flow stresses for SLM and EBM processed Ti-6-4 alloy, while the flow stress is about 20% higher than reported for commercial reference material. The strain to failure of both materials shows considerable strain rate sensitivity. The results of post-mortem analysis of spall fracture will also be presented.

  14. Investigation of Stress Concentration and Casing Strength Degradation Caused by Corrosion Pits

    Directory of Open Access Journals (Sweden)

    Wei Yan

    2016-01-01

    Full Text Available Downhole casing and tubing are subjected to corrosion in many cases because of the exposure to corrosive environment. A more serious problem is that pitting corrosion occurs in the casing inner surface. Meanwhile, downhole strings are subjected to various forms of mechanical loads, for example, internal pressure load, external collapse load, or both. These loads acting on the corrosion pits will cause stress concentration and degrade the casing strength. Thus, it is essential to evaluate the stress concentration degree reasonably. The SCF (stress concentration factor is usually used to characterize the degree of stress concentration induced by corrosion pits. This paper presented a comparison on the SCFs regarding the analytical method for a single pit and experimental method for double pits. The results show that the SCF of a single pit depends mainly on the depth of the corrosion pit; however, the SCF of the double pits strongly depends on the pits distance. A correction factor of 1.3 was recommended in the double pits SCF prediction model.

  15. On the impact of multi-axial stress states on trailing edge bondlines in wind turbine rotor blades

    Science.gov (United States)

    Noever Castelos, Pablo; Balzani, Claudio

    2016-09-01

    For a reliable design of wind turbine systems all of their components have to be designed to withstand the loads appearing in the turbine's lifetime. When performed in an integral manner this is called systems engineering, and is exceptionally important for components that have an impact on the entire wind turbine system, such as the rotor blade. Bondlines are crucial subcomponents of rotor blades, but they are not much recognized in the wind energy research community. However, a bondline failure can lead to the loss of a rotor blade, and potentially of the entire turbine, and is extraordinarily relevant to be treated with strong emphasis when designing a wind turbine. Modern wind turbine rotor blades with lengths of 80 m and more offer a degree of flexibility that has never been seen in wind energy technology before. Large deflections result in high strains in the adhesive connections, especially at the trailing edge. The latest edition of the DNV GL guideline from end of 2015 demands a three-dimensional stress analysis of bondlines, whereas before an isolated shear stress proof was sufficient. In order to quantify the lack of safety from older certification guidelines this paper studies the influence of multi-axial stress states on the ultimate and fatigue load resistance of trailing edge adhesive bonds. For this purpose, detailed finite element simulations of the IWES IWT-7.5-164 reference wind turbine blades are performed. Different yield criteria are evaluated for the prediction of failure and lifetime. The results show that the multi-axial stress state is governed by span-wise normal stresses. Those are evidently not captured in isolated shear stress proofs, yielding non-conservative estimates of lifetime and ultimate load resistance. This finding highlights the importance to include a three-dimensional stress state in the failure analysis of adhesive bonds in modern wind turbine rotor blades, and the necessity to perform a three-dimensional characterization

  16. The effect of edge interlaminar stresses on the strength of carbon/epoxy laminates of different stacking geometry

    OpenAIRE

    MOMCILO STEVANOVIC; MILAN GORDIC; DANIELA SEKULIC; ISIDOR DJORDJEVIC

    2006-01-01

    The effect of edge interlaminar stresses on strength of carbon/epoxy laminates of different stacking geometry: cross-ply, quasi-isotropic and angle-ply laminates with additional 0º and 90º ply was studied. Coupons with two widths of laminates with an inverse stacking sequence were tested in static tensile tests. The effect of edge interlaminar stresses on strength was studied, by comparing the values of the tensile strength of laminate coupons of the same width with an inverse stacking sequen...

  17. Strength evolution of simulated carbonate-bearing faults: The role of normal stress and slip velocity

    Science.gov (United States)

    Mercuri, Marco; Scuderi, Marco Maria; Tesei, Telemaco; Carminati, Eugenio; Collettini, Cristiano

    2018-04-01

    A great number of earthquakes occur within thick carbonate sequences in the shallow crust. At the same time, carbonate fault rocks exhumed from a depth plasticity). We performed friction experiments on water-saturated simulated carbonate-bearing faults for a wide range of normal stresses (from 5 to 120 MPa) and slip velocities (from 0.3 to 100 μm/s). At high normal stresses (σn > 20 MPa) fault gouges undergo strain-weakening, that is more pronounced at slow slip velocities, and causes a significant reduction of frictional strength, from μ = 0.7 to μ = 0.47. Microstructural analysis show that fault gouge weakening is driven by deformation accommodated by cataclasis and pressure-insensitive deformation processes (pressure solution and granular plasticity) that become more efficient at slow slip velocity. The reduction in frictional strength caused by strain weakening behaviour promoted by the activation of pressure-insensitive deformation might play a significant role in carbonate-bearing faults mechanics.

  18. Lithospheric Strength and Stress State: Persistent Challenges and New Directions in Geodynamics

    Science.gov (United States)

    Hirth, G.

    2017-12-01

    The strength of the lithosphere controls a broad array of geodynamic processes ranging from earthquakes, the formation and evolution of plate boundaries and the thermal evolution of the planet. A combination of laboratory, geologic and geophysical observations provides several independent constraints on the rheological properties of the lithosphere. However, several persistent challenges remain in the interpretation of these data. Problems related to extrapolation in both scale and time (rate) need to be addressed to apply laboratory data. Nonetheless, good agreement between extrapolation of flow laws and the interpretation of microstructures in viscously deformed lithospheric mantle rocks demonstrates a strong foundation to build on to explore the role of scale. Furthermore, agreement between the depth distribution of earthquakes and predictions based on extrapolation of high temperature friction relationships provides a basis to understand links between brittle deformation and stress state. In contrast, problems remain for rationalizing larger scale geodynamic processes with these same rheological constraints. For example, at face value the lab derived values for the activation energy for creep are too large to explain convective instabilities at the base of the lithosphere, but too low to explain the persistence of dangling slabs in the upper mantle. In this presentation, I will outline these problems (and successes) and provide thoughts on where new progress can be made to resolve remaining inconsistencies, including discussion of the role of the distribution of volatiles and alteration on the strength of the lithosphere, new data on the influence of pressure on friction and fracture strength, and links between the location of earthquakes, thermal structure, and stress state.

  19. Maintaining the Background Dust Opacity During Northern Hemisphere Summer Mars Using Wind Stress Based Dust Lifting

    Science.gov (United States)

    Jha, V.; Kahre, M. A.

    2017-12-01

    The Mars atmosphere has low levels of dust during Northern Hemisphere (NH) spring and summer (the non-dusty season) and increased levels during NH autumn and winter (the dusty season). In the absence of regional or global storms, dust devils and local storms maintain a background minimum dust loading during the non-dusty season. While observational surveys and Global Climate Model (GCM) studies suggest that dust devils are likely to be major contributors to the background haze during NH spring and summer, a complete understanding of the relative contribution of dust devils and local dust storms has not yet been achieved. We present preliminary results from an investigation that focuses on the effects of radiatively active water ice clouds on dust lifting processes during these seasons. Water ice clouds are known to affect atmospheric temperatures directly by absorption and emission of thermal infrared radiation and indirectly through dynamical feedbacks. Our goal is to understand how clouds affect the contribution by local (wind stress) dust storms to the background dust haze during NH spring and summer. The primary tool for this work is the NASA Ames Mars GCM, which contains physical parameterizations for a fully interactive dust cycle. Three simulations that included wind stress dust lifting were executed for a period of 5 Martian years: a case that included no cloud formation, a case that included radiatively inert cloud formation and a case that included radiatively active cloud (RAC) formation. Results show that when radiatively active clouds are included, the clouds in the aphelion cloud belt radiatively heat the atmosphere aloft in the tropics (Figure 1). This heating produces a stronger overturning circulation, which in turn produces an enhanced low-level flow in the Hadley cell return branch. The stronger low-level flow drives higher surface stresses and increased dust lifting in those locations. We examine how realistic these simulated results are by

  20. The Alignment of the Mean Wind and Stress Vectors in the Unstable Surface Layer

    Science.gov (United States)

    Bernardes, M.; Dias, N. L.

    2010-01-01

    A significant non-alignment between the mean horizontal wind vector and the stress vector was observed for turbulence measurements both above the water surface of a large lake, and over a land surface (soybean crop). Possible causes for this discrepancy such as flow distortion, averaging times and the procedure used for extracting the turbulent fluctuations (low-pass filtering and filter widths etc.), were dismissed after a detailed analysis. Minimum averaging times always less than 30 min were established by calculating ogives, and error bounds for the turbulent stresses were derived with three different approaches, based on integral time scales (first-crossing and lag-window estimates) and on a bootstrap technique. It was found that the mean absolute value of the angle between the mean wind and stress vectors is highly related to atmospheric stability, with the non-alignment increasing distinctively with increasing instability. Given a coordinate rotation that aligns the mean wind with the x direction, this behaviour can be explained by the growth of the relative error of the u- w component with instability. As a result, under more unstable conditions the u- w and the v- w components become of the same order of magnitude, and the local stress vector gives the impression of being non-aligned with the mean wind vector. The relative error of the v- w component is large enough to make it undistinguishable from zero throughout the range of stabilities. Therefore, the standard assumptions of Monin-Obukhov similarity theory hold: it is fair to assume that the v- w stress component is actually zero, and that the non-alignment is a purely statistical effect. An analysis of the dimensionless budgets of the u- w and the v- w components confirms this interpretation, with both shear and buoyant production of u- w decreasing with increasing instability. In the v- w budget, shear production is zero by definition, while buoyancy displays very low-intensity fluctuations around

  1. Stress Linearization and Strength Evaluation of the BEP's Flow Plates for a Dual Cooled Fuel Assembly

    International Nuclear Information System (INIS)

    Kim, Jae Yong; Yoon, Kyung Ho; Kang, Heung Seok; Lee, Young Ho; Lee, Kang Hee; Kim, Hyung Kyu

    2009-01-01

    A fuel assembly is composed of 5 major components, such as a top end piece (TEP), a bottom end piece (BEP), spacer grids (SGs), guide tubes (GTs) and an instrumentation tube (IT) and fuel rods (FRs). There are no ASME criteria about all components except for a TEP/BEP. The TEP/BEP should satisfy stress intensity limits in case of condition A and B of ASME, Section III, Division 1 . Subsection NB. In a dual cooled fuel assembly, the array and position of fuels are changed from those of a conventional PWR fuel assembly to achieve a power uprating. The flow plates of top/bottom end pieces (TEP/BEP) have to be modified into proper shape to provide flow holes to direct the heated coolant into/out of the fuel assembly but structural intensity of these plates within a 22.241 kN axial loading should satisfy Tresca stress limits in ASME code. In this paper, stress linearization procedure and strength evaluation of a newly designed BEP for the dual cooled fuel assembly are described

  2. Variations of Sea Surface Temperature, Wind Stress, and Rainfall over the Tropical Atlantic and South America.

    Science.gov (United States)

    Nobre, Paulo; Srukla, J.

    1996-10-01

    Empirical orthogonal functions (E0Fs) and composite analyses are used to investigate the development of sea surface temperature (SST) anomaly patterns over the tropical Atlantic. The evolution of large-scale rainfall anomaly patterns over the equatorial Atlantic and South America are also investigated. 71e EOF analyses revealed that a pattern of anomalous SST and wind stress asymmetric relative to the equator is the dominant mode of interannual and longer variability over the tropical Atlantic. The most important findings of this study are as follows.Atmospheric circulation anomalies precede the development of basinwide anomalous SST patterns over the tropical Atlantic. Anomalous SST originate off the African coast simultaneously with atmospheric circulation anomalies and expand westward afterward. The time lag between wind stress relaxation (strengthening) and maximum SST warming (cooling) is about two months.Anomalous atmospheric circulation patterns over northern tropical Atlantic are phase locked to the seasonal cycle. Composite fields of SLP and wind stress over northern tropical Atlantic can be distinguished from random only within a few months preceding the March-May (MAM) season. Observational evidence is presented to show that the El Niño-Southern Oscillation phenomenon in the Pacific influences atmospheric circulation and SST anomalies over northern tropical Atlantic through atmospheric teleconnection patterns into higher latitudes of the Northern Hemisphere.The well-known droughts over northeastern Brazil (Nordeste) are a local manifestation of a much larger-scale rainfall anomaly pattern encompassing the whole equatorial Atlantic and Amazon region. Negative rainfall anomalies to the south of the equator during MAM, which is the rainy season for the Nordeste region, are related to an early withdrawal of the intertropical convergence zone toward the warm SST anomalies over the northern tropical Atlantic. Also, it is shown that precipitation anomalies

  3. FEM Modeling of In-Plane Stress Distribution in Thick Brittle Coatings/Films on Ductile Substrates Subjected to Tensile Stress to Determine Interfacial Strength.

    Science.gov (United States)

    Wang, Kaishi; Zhang, Fangzhou; Bordia, Rajendra K

    2018-03-27

    The ceramic-metal interface is present in various material structures and devices that are vulnerable to failures, like cracking, which are typically due to their incompatible properties, e.g., thermal expansion mismatch. In failure of these multilayer systems, interfacial shear strength is a good measure of the robustness of interfaces, especially for planar films. There is a widely-used shear lag model and method by Agrawal and Raj to analyse and measure the interfacial shear strength of thin brittle film on ductile substrates. The use of this classical model for a type of polymer derived ceramic coatings (thickness ~18 μm) on steel substrate leads to high values of interfacial shear strength. Here, we present finite element simulations for such a coating system when it is subjected to in-plane tension. Results show that the in-plane stresses in the coating are non-uniform, i.e., varying across the thickness of the film. Therefore, they do not meet one of the basic assumptions of the classical model: uniform in-plane stress. Furthermore, effects of three significant parameters, film thickness, crack spacing, and Young's modulus, on the in-plane stress distribution have also been investigated. 'Thickness-averaged In-plane Stress' (TIS), a new failure criterion, is proposed for estimating the interfacial shear strength, which leads to a more realistic estimation of the tensile strength and interfacial shear strength of thick brittle films/coatings on ductile substrates.

  4. Yield strength, shear stress and toughness of YBCO samples textured by Bridgman technique

    International Nuclear Information System (INIS)

    Roa, J J; Capdevila, X G; Martinez, M; Segarra, M; Jimenez-Pique, E

    2008-01-01

    Mechanical properties of the orthorhombic phase of YBa 2 Cu 3 O 7-δ (Y-123) at room temperature have been investigated at different applied loads using nanoindentation technique. The study was carried out for several monodomains on the (001) planes for textured Bridgman samples with dispersed Y 2 BaCuO 5 (Y-211) particles as pinning centers. The yield strength (σ ys ), shear stress (τ m ) and toughness (K IC ) of Y123/Y211composite was determined at different applied loads. First and second mechanical properties have been calculated though the Hertz equations and the last one with Lawn et al. equations. Finally, the ultra-low imprints obtained by nanoindentation have been correlated with parameters obtained by Field Emission Scanning Electron Microscope (FE-SEM)

  5. Effect of microstructure on the sulphide stress cracking susceptibility of a high strength pipeline steel

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, E. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas-UAEM, Av. Universidad 1001, 62209-Cuernavaca, Mor. (Mexico); Gonzalez-Rodriguez, J.G. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas-UAEM, Av. Universidad 1001, 62209-Cuernavaca, Mor. (Mexico)], E-mail: ggonzalez@uaem.mx; Torres-Islas, A.; Serna, S. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas-UAEM, Av. Universidad 1001, 62209-Cuernavaca, Mor. (Mexico); Campillo, B. [Intituto de Ciencias Fisicas-Facultad de Quimicas-Universidad Nacional Autonoma de Mexico Cuernavaca, Mor. (Mexico); Dominguez-Patino, G. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas-UAEM, Av. Universidad 1001, 62209-Cuernavaca, Mor. (Mexico); Juarez-Islas, J.A. [Instituto de Investigaciones en Materiales-Universidad Nacional Autonoma de Mexico, Circuito Exterior S/N, Cd. Universitaria, C.P. 04510, Mexico, D.F. (Mexico)

    2008-12-15

    The sulphide stress cracking (SSC) susceptibility of a newly developed high strength microalloyed steel with three different microstructures has been evaluated using the slow strain rate testing (SSRT) technique. Studies were complemented with potentiodynamic polarization curves and hydrogen permeation measurements. Material included a C-Mn steel having Ni, Cu, and Mo as main microalloying elements with three microstructures: martensitic, ferritic and ferritic + bainitic. Testing temperatures included 25, 50, 70 and 90 deg. C. Detailed SEM observations of the microstructure and fracture surfaces were done to identify possible degradation mechanisms. The results showed that in all cases, the corrosion rate, number of hydrogen atoms at the surface and the percentage reduction in area increased with temperature. The steel with a martensitic microstructure had the highest SSC susceptibility at all temperatures, whereas the ferritic steels were susceptible only at 25 deg. C, and the most likely mechanism is hydrogen embrittlement assisted by anodic dissolution.

  6. Influence of Welding Strength Matching Coefficient and Cold Stretching on Welding Residual Stress in Austenitic Stainless Steel

    Science.gov (United States)

    Lu, Yaqing; Hui, Hu; Gong, Jianguo

    2018-05-01

    Austenitic stainless steel is widely used in pressure vessels for the storage and transportation of liquid gases such as liquid nitrogen, liquid oxygen, and liquid hydrogen. Cryogenic pressure vessel manufacturing uses cold stretching technology, which relies heavily on welding joint performance, to construct lightweight and thin-walled vessels. Residual stress from welding is a primary factor in cases of austenitic stainless steel pressure vessel failure. In this paper, on the basis of Visual Environment 10.0 finite element simulation technology, the residual stress resulting from different welding strength matching coefficients (0.8, 1, 1.2, 1.4) for two S30408 plates welded with three-pass butt welds is calculated according to thermal elastoplastic theory. In addition, the stress field was calculated under a loading as high as 410 MPa and after the load was released. Path 1 was set to analyze stress along the welding line, and path 2 was set to analyze stress normal to the welding line. The welding strength matching coefficient strongly affected both the longitudinal residual stress (center of path 1) and the transverse residual stress (both ends of path 1) after the welding was completed. However, the coefficient had little effect on the longitudinal and transverse residual stress of path 2. Under the loading of 410 MPa, the longitudinal and transverse stress decreased and the stress distribution, with different welding strength matching coefficients, was less diverse. After the load was released, longitudinal and transverse stress distribution for both path 1 and path 2 decreased to a low level. Cold stretching could reduce the effect of residual stress to various degrees. Transverse strain along the stretching direction was also taken into consideration. The experimental results validated the reliability of the partial simulation.

  7. Tests on creep and influence of creep on strength of concrete under multiaxial stresses

    International Nuclear Information System (INIS)

    Lanig, N.; Stoeckl, S.; Kupfer, H.

    1988-12-01

    Long-time tests of three-axially loaded, sealed cylindrical specimens d = 15 cm, h = 40 cm, were carried out. The 20-cm-cube strength of the concrete was app. 45 N/mm 2 . The creep stresses were chosen in the following ranges: 0,3 ≤ σ c /β c ≤ 2,1; 0 ≤ σ r /σ l ≤ 1,0. The creep coefficients obtained were clearly depending on the multi-axial stress conditions. The creep coefficients for a t = 2 years loading were reaching app. 1 for σ l /β c = 0,3 and app. 3 for σ l /β c = 2,1, when the test evaluation was based on the initial deformations meausred after 1 minute. For σ l /β c = 2,1 the creep coefficients obtained were about 4 times as large, proceeding form calculated elastic deformations. Further evaluations concerned the Young's modulus E, Poisson's ratio μ, the bulk modulus K and the shear modulus G. The preceding permanent load leads to an increase in the Young's modulus of the concrete in longitudinal direction of the specimen up to about 4 times the value of not preloaded comparative specimens. (orig.) [de

  8. FEM Modeling of In-Plane Stress Distribution in Thick Brittle Coatings/Films on Ductile Substrates Subjected to Tensile Stress to Determine Interfacial Strength

    Directory of Open Access Journals (Sweden)

    Kaishi Wang

    2018-03-01

    Full Text Available The ceramic-metal interface is present in various material structures and devices that are vulnerable to failures, like cracking, which are typically due to their incompatible properties, e.g., thermal expansion mismatch. In failure of these multilayer systems, interfacial shear strength is a good measure of the robustness of interfaces, especially for planar films. There is a widely-used shear lag model and method by Agrawal and Raj to analyse and measure the interfacial shear strength of thin brittle film on ductile substrates. The use of this classical model for a type of polymer derived ceramic coatings (thickness ~18 μm on steel substrate leads to high values of interfacial shear strength. Here, we present finite element simulations for such a coating system when it is subjected to in-plane tension. Results show that the in-plane stresses in the coating are non-uniform, i.e., varying across the thickness of the film. Therefore, they do not meet one of the basic assumptions of the classical model: uniform in-plane stress. Furthermore, effects of three significant parameters, film thickness, crack spacing, and Young’s modulus, on the in-plane stress distribution have also been investigated. ‘Thickness-averaged In-plane Stress’ (TIS, a new failure criterion, is proposed for estimating the interfacial shear strength, which leads to a more realistic estimation of the tensile strength and interfacial shear strength of thick brittle films/coatings on ductile substrates.

  9. Does perceived stress moderate the association between depressive symptoms and socioemotional and behavioural strengths and difficulties in adolescence?

    Science.gov (United States)

    Lätsch, Alexander

    2018-04-01

    More and more students report high level of perceived stress during childhood and adolescence, which is associated with socioemotional and behavioural strengths and difficulties. This study aims-based on the cognitive vulnerability-transactional stress theory-to examine perceived stress in early adolescence as a potential moderator in the association between depressive symptoms and socioemotional and behavioural strengths and difficulties from early to middle adolescence. Results of latent moderated structural equations with questionnaire data from a longitudinal study with 1,088 German students (Time 1: M age  = 13.70, SD = 0.53; Time 2: N = 845, M age  = 15.32, SD = 0.49) indicate that perceived stress functions as a moderator in the above-mentioned association and dominates the interaction if perceived strongly. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Tropical Atlantic biases and their relation to surface wind stress and terrestrial precipitation

    Science.gov (United States)

    Richter, Ingo; Xie, Shang-Ping; Wittenberg, Andrew T.; Masumoto, Yukio

    2012-03-01

    Most coupled general circulation models (GCMs) perform poorly in the tropical Atlantic in terms of climatological seasonal cycle and interannual variability. The reasons for this poor performance are investigated in a suite of sensitivity experiments with the Geophysical Fluid Dynamics Laboratory (GFDL) coupled GCM. The experiments show that a significant portion of the equatorial SST biases in the model is due to weaker than observed equatorial easterlies during boreal spring. Due to these weak easterlies, the tilt of the equatorial thermocline is reduced, with shoaling in the west and deepening in the east. The erroneously deep thermocline in the east prevents cold tongue formation in the following season despite vigorous upwelling, thus inhibiting the Bjerknes feedback. It is further shown that the surface wind errors are due, in part, to deficient precipitation over equatorial South America and excessive precipitation over equatorial Africa, which already exist in the uncoupled atmospheric GCM. Additional tests indicate that the precipitation biases are highly sensitive to land surface conditions such as albedo and soil moisture. This suggests that improving the representation of land surface processes in GCMs offers a way of improving their performance in the tropical Atlantic. The weaker than observed equatorial easterlies also contribute remotely, via equatorial and coastal Kelvin waves, to the severe warm SST biases along the southwest African coast. However, the strength of the subtropical anticyclone and along-shore winds also play an important role.

  11. Tropical Atlantic biases and their relation to surface wind stress and terrestrial precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Ingo [Research Institute for Global Change, JAMSTEC, Yokohama (Japan); University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); Xie, Shang-Ping [University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); University of Hawaii at Manoa, Department of Meteorology, Honolulu, HI (United States); Wittenberg, Andrew T. [NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, NJ (United States); Masumoto, Yukio [Research Institute for Global Change, JAMSTEC, Yokohama (Japan)

    2012-03-15

    Most coupled general circulation models (GCMs) perform poorly in the tropical Atlantic in terms of climatological seasonal cycle and interannual variability. The reasons for this poor performance are investigated in a suite of sensitivity experiments with the Geophysical Fluid Dynamics Laboratory (GFDL) coupled GCM. The experiments show that a significant portion of the equatorial SST biases in the model is due to weaker than observed equatorial easterlies during boreal spring. Due to these weak easterlies, the tilt of the equatorial thermocline is reduced, with shoaling in the west and deepening in the east. The erroneously deep thermocline in the east prevents cold tongue formation in the following season despite vigorous upwelling, thus inhibiting the Bjerknes feedback. It is further shown that the surface wind errors are due, in part, to deficient precipitation over equatorial South America and excessive precipitation over equatorial Africa, which already exist in the uncoupled atmospheric GCM. Additional tests indicate that the precipitation biases are highly sensitive to land surface conditions such as albedo and soil moisture. This suggests that improving the representation of land surface processes in GCMs offers a way of improving their performance in the tropical Atlantic. The weaker than observed equatorial easterlies also contribute remotely, via equatorial and coastal Kelvin waves, to the severe warm SST biases along the southwest African coast. However, the strength of the subtropical anticyclone and along-shore winds also play an important role. (orig.)

  12. Dependence of Wave-Breaking Statistics on Wind Stress and Wave Development

    Science.gov (United States)

    Katsaros, Kristina B.; Atakturk, Serhad S.

    1992-01-01

    Incidence of wave breaking for pure wind driven waves has been studied on Lake Washington at wind speeds up to 8 m/s. Video recordings were employed to identify and categorize the breaking events in terms of micro-scale, spilling and plunging breakers. These events were correlated with the magnitude of the wave spectrum measured with a resistance wire wave gauge and band pass filtered between 6 and 10 Hz. An equivalent percentage of breaking crests were found for spilling and plunging events. Wave forcing as measured by wind stress (or friction velocity, u(sub *), squared) and by inverse wave age, u(sub *)/Cp where Cp is the phase velocity of the waves at the peak of the frequency spectrum, were found to be good prerictors of percentage of breaking crests. When combined in a two parameter regression, those two variables gave small standard deviation and had a high correlation coefficient (66 percent). The combination of u(sub *)(exp 2) and u(sub *)/Cp can be understood in physical terms. Furthermore, for the larger values of u(sub *)(exp 2) the dependence of wave braking and wave age was stronger than at the low end of the values u(sub *)(exp 2) and u(sub *)/Cp. Thus, both the level of wave development as determined by inverse wave age, which we may term relative wind effectiveness for wave forcing and the wind forcing on the water surface determine the incidence of wave breaking. Substituting U(sub 10)(sup 3.75) (which is the dependence of whitecap cover found by Monahan and coworkers) an equivalent correlation was found to the prediction by u(sub *)(exp 2). Slightly better standard deviation value and higher correlation coefficient were found by using a Reynolds number as predictor. A two-parameter regression involving u(sub *)(exp 2) and a Reynold's number proposed by Toba and his colleagues which relates u(sub *)(exp 2) and peak wave frequency, improves the correlation even more but is less easy to interpret in physical terms. The equivalent percentage of

  13. Mean Stress Effect on the Axial Fatigue Strength of DIN 34CrNiMo6 Quenched and Tempered Steel

    Directory of Open Access Journals (Sweden)

    Luis Pallarés-Santasmartas

    2018-03-01

    Full Text Available The present study consists of a theoretical and experimental investigation of the effect of axial mean stresses on the high cycle fatigue behaviour of DIN 34CrNiMo6 high strength steel in quenched and tempered conditions. The axial S-N curves under 4 different stresses ratios were obtained. Experimental results show that increasing the value of the tension mean stresses gradually reduces the axial stress amplitude the material can withstand without failure. Moreover, the compressive mean stresses show a beneficial effect in terms of the axial fatigue strength, resulting in a non-symmetrical Haigh diagram. A historic review of the axial mean stress effect is presented, showing the shape of the Haigh diagrams for ductile metals and presenting the most-known empirical and physical theories. The results for this steel are compared with the physical theories of Findley based on the critical plane; the Froustey’s and Marin’s methods, based on energetic theories; and the Crossland invariants method based on the Gough’s theory of fatigue damage. Taking into account the experimental results, a physical fatigue function based on energetic considerations is proposed. Its application to the fatigue case with mean stresses can be interpreted in terms of a balance of elastic energies of distortion and volume change. Macro-analyses of specimen fracture appearance were conducted in order to obtain the fracture characteristics for different mean stress values.

  14. Remote wind stress influence on mean sea level in a subtropical coastal region

    Directory of Open Access Journals (Sweden)

    Mabel Calim Costa

    2012-09-01

    Full Text Available The purpose of this study was to assess the relative influence of remote wind stress on mean sea level (MSL variations in the coastal region of Cananeia (Sao Paulo State, Southern Brazil during the period from 1/1/1955 to 12/31/1993. An optimized low-pass Thompson filter for the study area, and spectral analysis (cross spectrum, coherence and phase lag of the relationship between the MSL and both parallel (T// and perpendicular (T| wind stress components were applied. These were extracted from four grid points of the NCEP/NCAR global model. The predominance of annual oscillations as those of greatest coherence and energy, of periods of approximately 341 days (frequency of 0.00293 cpd and 410 days (frequency of 0.00244 cpd, respectively, were observed. Offshore NCEP/NCAR grid points were those with the highest coherence and energy throughout the study in relation to the observed MSL. This may be linked to the restriction of the NCEP/NCAR model as regards the inland limit. It is also concluded that remote wind stress may play an important role in several MSL time scales, including the annual ones. Based on criteria such as coherence and energy peaks, the wind stress component of greatest effect on MSL was the parallel one.O presente estudo tem por objetivo avaliar a influência relativa de tensão do vento remoto na variação do nível médio do mar (NMM para a região costeira de Cananéia (SP durante o período de 1/1/1955 a 31/12/1993. Foram aplicados um filtro de passa-baixa de Thompson (1983, otimizado para a região de Cananéia, além de análise espectral (espectro cruzado, coerência e defasagem entre o NMM e as componentes paralela (T// e perpendicular (T| da tensão do vento. Estas foram extraídas de quatro pontos de grade do modelo global NCEP/NCAR. Observou-se a predominância das oscilações anuais como aquelas de maior coerência e energia, destacando-se os períodos de aproximadamente 341 dias (frequência de 0,00293 cpd e 410

  15. Effect of load eccentricity and stress level on monopile support for offshore wind turbines

    DEFF Research Database (Denmark)

    Klinkvort, Rasmus Tofte; Hededal, Ole

    2014-01-01

    on which load is applied with a large eccentricity. With centrifuge tests as the basis, this paper investigates the behaviour of a rigid pile loaded with a high eccentricity. A test series was carried out to simulate idealized monotonic load cases for monopiles supporting an offshore wind turbine....... Centrifuge tests were performed on model monopiles subjected to stress distributions equal to prototype monopiles with pile diameters ranging from 1–5 m and eccentricities ranging from 8.25–17.75 pile diameters. It was possible to identify a unified response of all of these tests by using dimensional...... analysis and Rankine’s passive earth pressure coefficient as a normalization parameter. The normalized ultimate soil resistance was unaffected by acceleration level and load eccentricity, indicating that the failure mechanism was the same for all tests. Based on the centrifuge tests, a reformulation...

  16. Evaluation of shear bond strength and shear stress on zirconia reinforced lithium silicate and high translucency zirconia.

    Directory of Open Access Journals (Sweden)

    Amanda Maria de Oliveira Dal Piva

    2018-01-01

    Full Text Available This study evaluated the shear stress distribution on the adhesive interface and the bond strength between resin cement and two ceramics. For finite element analysis (FEA, a tridimensional model was made using computer-aided design software. This model consisted of a ceramic slice (10x10x2mm partially embedded on acrylic resin with a resin cement cylinder (Ø=3.4 mm and h=3mm cemented on the external surface. Results of maximum principal stress and maximum principal shear were obtained to evaluate the stress generated on the ceramic and the cylinder surfaces. In order to reproduce the in vitro test, similar samples to the computational model were manufactured according to ceramic material (Zirconia reinforced lithium silicate - ZLS and high translucency Zirconia - YZHT, (N=48, n=12. Half of the specimens were submitted to shear bond test after 24h using a universal testing machine (0.5 mm/min, 50kgf until fracture. The other half was stored (a (180 days, water, 37ºC prior to the test. Bond strength was calculated in MPa and submitted to analysis of variance. The results showed that ceramic material influenced bond strength mean values (p=0.002, while aging did not: YZHT (19.80±6.44a, YZHTa (17.95±7.21a, ZLS (11.88±5.40b, ZLSa (11.76±3.32b. FEA results showed tensile and shear stress on ceramic and cylinder surfaces with more intensity on their periphery. Although the stress distribution was similar for both conditions, YZHT showed higher bond strength values; however, both materials seemed to promote durable bond strength.

  17. The stress-corrosion cracking behavior of high-strength aluminum powder metallurgy alloys

    Science.gov (United States)

    Pickens, J. R.; Christodoulou, L.

    1987-01-01

    The susceptibility to stress-corrosion cracking (SCC) of rapidly solidified (RS) aluminum powder metallurgy (P/M) alloys 7090 and 7091, mechanically alloyed aluminum P/M alloy IN* 9052, and ingot metallurgy (I/M) alloys of similar compositions was compared using bolt-loaded double cantilever beam specimens. In addition, the effects of aging, grain size, grain boundary segregation, pre-exposure embrittlement, and loading mode on the SCC of 7091 were independently assessed. Finally, the data generated were used to elucidate the mechanisms of SCC in the three P/M alloys. The IN 9052 had the lowest SCC susceptibility of all alloys tested in the peak-strength condition, although no SCC was observed in the two RS alloys in the overaged condition. The susceptibility of the RS alloys was greater in the underaged than the peak-aged temper. We detected no significant differences in susceptibility of 7091 with grain sizes varying from 2 to 300 μm. Most of the crack advance during SCC of 7091 was by hydrogen embrittlement (HE). Furthermore, both RS alloys were found to be susceptible to preexposure embrittlement—also indicative of HE. The P/M alloys were less susceptible to SCC than the I/M alloys in all but one test.

  18. Wind Shear and the Strength of Severe Convective Phenomena—Preliminary Results from Poland in 2011–2015

    Directory of Open Access Journals (Sweden)

    Wojciech Pilorz

    2016-10-01

    Full Text Available Severe convective phenomena cause significant loss in the economy and, primarily, casualties. Therefore, it is essential to forecast such extreme events to avoid or minimize the negative consequences. Wind shear provides an updraft-downdraft separation in the convective cell, which extends the cell lifetime. Wind shears between a few different air layers have been examined in all damaging convective cases in Poland, taken from the European Severe Weather Database between 2011 and 2015, in order to find their values and patterns according to the intensity of this phenomenon. Each severe weather report was assigned wind shear values from the nearest sounding station, and subsequently the presented summary was made. It was found that wind shear values differ between the given phenomena and their intensity. This regularity is particularly visible in shears containing 0 km wind. The highest shears occur within wind reports. Lower values are associated with hail reports. An important difference between weak and F1+ tornadoes was found in most of the wind shears. Severe phenomena probability within 0–6 km and 0–1 km shears show different patterns according to the phenomena and their intensity. This finding has its application in severe weather forecasting.

  19. Theoretical Conversions of Different Hardness and Tensile Strength for Ductile Materials Based on Stress-Strain Curves

    Science.gov (United States)

    Chen, Hui; Cai, Li-Xun

    2018-04-01

    Based on the power-law stress-strain relation and equivalent energy principle, theoretical equations for converting between Brinell hardness (HB), Rockwell hardness (HR), and Vickers hardness (HV) were established. Combining the pre-existing relation between the tensile strength ( σ b ) and Hollomon parameters ( K, N), theoretical conversions between hardness (HB/HR/HV) and tensile strength ( σ b ) were obtained as well. In addition, to confirm the pre-existing σ b -( K, N) relation, a large number of uniaxial tensile tests were conducted in various ductile materials. Finally, to verify the theoretical conversions, plenty of statistical data listed in ASTM and ISO standards were adopted to test the robustness of the converting equations with various hardness and tensile strength. The results show that both hardness conversions and hardness-strength conversions calculated from the theoretical equations accord well with the standard data.

  20. Effects of static strain aging on residual stress stability and alternating bending strength of shot peened AISI 4140

    Energy Technology Data Exchange (ETDEWEB)

    Menig, R.; Schulze, V.; Voehringer, O. [Inst. fuer Werkstoffkunde 1, Univ. Karlsruhe (TH), Karlsruhe (Germany)

    2002-07-01

    Increases of residual stress stability and alternating bending strength of shot peened AISI 4140 are obtained by successive annealing treatments. This is caused by static strain aging effects, which lead to pinning of dislocations by carbon atoms and very small carbides. It will be shown that by well directed annealing of a quenched and tempered AISI 4140 it is possible to maximize the positive effects of static strain aging, without causing extended thermal residual stress relaxation. The amount of yield stress increases caused by static strain aging is quantified using tensile tests. Static strain aging is also found to be responsible for an increase of the quasi static and cyclic surface yield strength present after shot peening. (orig.)

  1. Role of sea surface wind stress forcing on transport between Tropical Pacific and Indian Ocean

    Science.gov (United States)

    Zhao, Q.

    Using an Indian-Pacific Ocean Circulation Model (IPOM) a simulation study on the Transports of between Tropical Pacific and Indian Ocean such as Indonesian Through flow (ITF) has been done. IPOM covered the area 25°E-70°W, 35°S-60°N. There are 31 levels in the vertical with 22 levels upper 400m in it. The horizontal resolution is 1/3° lat x 1.5° lon between 10°S and 10°N. The coastline and ocean topography of IPOM is prepared from Scripps topography data on 1x1°grid. Forcing IPOM with monthly observational wind stress in 1990-1999 the interannual variation of sea temperature has been reproduced well, not only on El Nino in the Pacific but also on Indian Ocean Dipole (IOD). Therefore, the oceanic circulations in the tropical ocean are reasonable. The analyses of the oceanic circulations from the simulations suggest that the transport southward through Makassar Strait is the primary route of thermocline water masses from the North Pacific to the Indonesian sea. The transport westward through Bali-Western Australian Transect (BWAT, at 117.5E) can be thought as the final output of ITF through the archipelago to Indian Ocean. The transport westward through BWAT is in 8-12S above 150m, its core centered near surface 10S, which looks like a jet. The westward velocity is more than 50 cm/s. The transport shows significant seasonal and interannual variations. The maximum is in Jul-Oct, minimum in Jan-Mar. These results are consistent with some observation basically. The correlation analyses indict that the variations of transport westward is related with the southeasterly anomaly in the east tropical Indian ocean. The transport variation lags wind anomaly about 3 months. The correlation coefficient is more than 0.6. The transport is strong during IOD, for example in 1994 and 1997. The variations are also related with the northwesterly anomaly in the center equatorial Pacific and the easterly in the eastern equatorial Pacific. The transport is strong in most ENSO

  2. Application of stress relaxation testing in evaluation of creep strength of a tungsten-alloyed 10% Cr cast steel

    International Nuclear Information System (INIS)

    Raghavender Rao, G.; Gupta, O.P.; Pradhan, B.

    2011-01-01

    Uniaxial isothermal stress relaxation tests (SRT) were performed on a tungsten-alloyed 10% Cr cast steel (G-X12Cr Mo W V Nb N 10 1 1) at temperatures of 580, 600 and 620 o C and initial strain levels of 0.2, 0.5 and 0.8%. Inelastic strain rates for different stresses were estimated from the stress versus time data generated from the tests. Conventional creep tests were also conducted on the same material at 580, 600 and 620 o C and at different stress levels. The strain rate data estimated from SRT were compared with minimum creep rates derived from the creep tests; the strain rates estimated from SRT with 0.8% initial strain level are in better agreement than those estimated from SRT with 0.2 and 0.5% initial strain levels. In order to ascertain the technique, stress relaxation behaviour was estimated from creep test data and compared with the stress relaxation curves obtained from SRT at corresponding temperatures. The stress relaxation curves obtained from SRT with 0.8% initial strain level are in good agreement with the stress relaxation curves estimated from the creep tests. It is concluded that the stress relaxation test with initial strain level of 0.8% could be considered as an appropriate short-term test technique for estimation of creep strength of newly developed materials.

  3. Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

    National Research Council Canada - National Science Library

    Underwood, John

    2000-01-01

    ...; overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid...

  4. Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

    Science.gov (United States)

    Sullivan, Roy M.

    2016-01-01

    The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.

  5. Estimates of stress drop and crustal tectonic stress from the 27 February 2010 Maule, Chile, earthquake: Implications for fault strength

    Science.gov (United States)

    Luttrell, K.M.; Tong, X.; Sandwell, D.T.; Brooks, B.A.; Bevis, M.G.

    2011-01-01

    The great 27 February 2010 Mw 8.8 earthquake off the coast of southern Chile ruptured a ???600 km length of subduction zone. In this paper, we make two independent estimates of shear stress in the crust in the region of the Chile earthquake. First, we use a coseismic slip model constrained by geodetic observations from interferometric synthetic aperture radar (InSAR) and GPS to derive a spatially variable estimate of the change in static shear stress along the ruptured fault. Second, we use a static force balance model to constrain the crustal shear stress required to simultaneously support observed fore-arc topography and the stress orientation indicated by the earthquake focal mechanism. This includes the derivation of a semianalytic solution for the stress field exerted by surface and Moho topography loading the crust. We find that the deviatoric stress exerted by topography is minimized in the limit when the crust is considered an incompressible elastic solid, with a Poisson ratio of 0.5, and is independent of Young's modulus. This places a strict lower bound on the critical stress state maintained by the crust supporting plastically deformed accretionary wedge topography. We estimate the coseismic shear stress change from the Maule event ranged from-6 MPa (stress increase) to 17 MPa (stress drop), with a maximum depth-averaged crustal shear-stress drop of 4 MPa. We separately estimate that the plate-driving forces acting in the region, regardless of their exact mechanism, must contribute at least 27 MPa trench-perpendicular compression and 15 MPa trench-parallel compression. This corresponds to a depth-averaged shear stress of at least 7 MPa. The comparable magnitude of these two independent shear stress estimates is consistent with the interpretation that the section of the megathrust fault ruptured in the Maule earthquake is weak, with the seismic cycle relieving much of the total sustained shear stress in the crust. Copyright 2011 by the American

  6. Strength through adversity: Moderate lifetime stress exposure is associated with psychological resilience in breast cancer survivors.

    Science.gov (United States)

    Dooley, Larissa N; Slavich, George M; Moreno, Patricia I; Bower, Julienne E

    2017-12-01

    Stress research typically emphasizes the toxic effects of stress, but recent evidence has suggested that stress exposure, in moderation, can facilitate resilience. To test whether moderate stress exposure promotes psychological resilience to cancer, we examined the relationship between lifetime stress exposure prior to cancer diagnosis and postdiagnosis psychological functioning among 122 breast cancer survivors. Lifetime acute and chronic stress was assessed using an interview-based measure, and psychological functioning was assessed using measures of cancer-related intrusive thoughts and positive and negative affect. Results indicated that acute stress exposure was associated with cancer-related intrusive thoughts in a quadratic fashion (p = .016), such that participants with moderate acute stress reported fewer intrusive thoughts compared to those with low or high acute stress. Similarly, a quadratic relationship emerged between acute stress exposure and positive affect (p = .009), such that individuals with moderate acute stress reported the highest levels of positive affect. In contrast, acute and chronic stress were related to negative affect in a positive, linear fashion (ps < .05). In conclusion, moderate stress exposure was associated with indicators of psychological resilience among breast cancer survivors, supporting stress exposure as a key factor influencing adjustment to breast cancer and providing evidence for stress-induced resilience in a novel population. Copyright © 2017 John Wiley & Sons, Ltd.

  7. Role of microstructure in the mean stress dependence of fatigue strength in Ti-6Al-4V alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ivanova, S.G.; Cohen, F.S.; Biederman, R.R.; Sisson, R.D. Jr.

    1999-07-01

    The high cycle fatigue properties of Ti-6Al-4V alloy with six different microstructure/texture combinations were investigated. Only materials with lamellar and fine bimodal microstructures exhibited linear Goodman relationship on the constant fatigue life diagram. Materials with coarse bimodal and equiaxed microstructures had anomalous mean stress dependency, with HCF strength at intermediate mean stresses being significantly lower than predicted by Goodman relationship, regardless of whether material was forged or cross-rolled. The role of microstructure in mean stress sensitivity behavior of Ti-6Al-4V is studied. Cyclic strain tests were conducted for all microstructures, and the results of strain-controlled and stress-controlled cyclic tests are compared and discussed.

  8. The adhesion strength and residual stress of colloidal-sol gel derived β-Tricalcium-Phosphate/Fluoridated-Hydroxyapatite biphasic coatings

    International Nuclear Information System (INIS)

    Cheng Kui; Zhang, Sam; Weng Wenjian; Khor, Khiam Aik; Miao Shundong; Wang Yongsheng

    2008-01-01

    β-tricalcium phosphate (β-TCP) powders are embedded in a fluoridated hydroxyapatite (FHA) matrix to form β-TCP-FHA composites via colloidal-sol gel method. This composite layer is deposited on top of a FHA layer to form a β-TCP-FHA/FHA biphasic coating. The effect of the nanosized powder on the residual stress is characterized through the X-ray diffraction peak shift. The powder incorporation increases the residual stress, while a large amount of β-TCP (Ca powder /Ca sol ratio is higher than 1/2) results in less gel shrinkage that partially compensates the mismatch of thermal expansion coefficient and thus the residual stress. Despite the elevated residual stress as more powders are embedded, the coating adhesion strength remains virtually constant: around 430 mN-500 mN in scanning scratch test

  9. Life estimation and analysis of dielectric strength, hydrocarbon backbone and oxidation of high voltage multi stressed EPDM composites

    Science.gov (United States)

    Khattak, Abraiz; Amin, Muhammad; Iqbal, Muhammad; Abbas, Naveed

    2018-02-01

    Micro and nanocomposites of ethylene propylene diene monomer (EPDM) are recently studied for different characteristics. Study on life estimation and effects of multiple stresses on its dielectric strength and backbone scission and oxidation is also vital for endorsement of these composites for high voltage insulation and other outdoor applications. In order to achieve these goals, unfilled EPDM and its micro and nanocomposites are prepared at 23 phr micro silica and 6 phr nanosilica loadings respectively. Prepared samples are energized at 2.5 kV AC voltage and subjected for a long time to heat, ultraviolet radiation, acid rain, humidity and salt fog in accelerated manner in laboratory. Dielectric strength, leakage current and intensity of saturated backbone and carbonyl group are periodically measured. Loss in dielectric strength, increase in leakage current and backbone degradation and oxidation were observed in all samples. These effects were least in the case of EPDM nanocomposite. The nanocomposite sample also demonstrated longest shelf life.

  10. Study of new heat treatment parameters for increasing mechanical strength and stress corrosion cracking resistance of 7075 Aluminium alloy

    OpenAIRE

    Silva, G.; Rivolta, B.; Gerosa, R.; Derudi, U.

    2013-01-01

    For many years 7075 Aluminum alloys have been widely used especially in those applications for which highmechanical performances are required. It is well known that the alloy in the T6 condition is characterized bythe highest ultimate and yield strengths, but, at the same time, by poor stress corrosion cracking (SCC)resistance. For this reason, in the aeronautic applications, new heat treatments have been introduced toproduce T7X conditions, which are characterized by lower mechanical strengt...

  11. Evaluation of strength-controlling defects in paper by stress concentration analyses

    Science.gov (United States)

    John M. Considine; David W. Vahey; James W. Evans; Kevin T. Turner; Robert E. Rowlands

    2011-01-01

    Cellulosic webs, such as paper materials, are composed of an interwoven, bonded network of cellulose fibers. Strength-controlling parameters in these webs are influenced by constituent fibers and method of processing and manufacture. Instead of estimating the effect on tensile strength of each processing/manufacturing variable, this study modifies and compares the...

  12. Fault roughness and strength heterogeneity control earthquake size and stress drop

    KAUST Repository

    Zielke, Olaf; Galis, Martin; Mai, Paul Martin

    2017-01-01

    An earthquake's stress drop is related to the frictional breakdown during sliding and constitutes a fundamental quantity of the rupture process. High-speed laboratory friction experiments that emulate the rupture process imply stress drop values

  13. Residual stress effects on the impact resistance and strength of fiber composites

    Science.gov (United States)

    Chamis, C. C.

    1973-01-01

    Equations have been derived to predict degradation effects of microresidual stresses on impact resistance of unidirectional fiber composites. Equations also predict lamination residual stresses in multilayered angle ply composites.

  14. BEM-DDM modelling of rock damage and its implications on rock laboratory strength and in-situ stresses

    International Nuclear Information System (INIS)

    Matsui, Hiroya

    2008-03-01

    Within the framework of JAEA's Research and Development on deep geological environments for assessing the safety and reliability of the disposal technology for nuclear waste, this study was conducted to determine the effects of sample damage on the strength obtained from laboratory results (uniaxial compression and Brazilian test). Results of testing on samples of Toki granite taken at Shobasama and at the construction site for the Mizunami Underground Research Laboratory (MIU) at Mizunami, Gifu Pref., Japan, were analysed. Some spatial variation of the results along the boreholes suggested the presence of a correlation between the laboratory strength and the in-situ stresses measured by means of the hydro-fracturing method. To confirm this, numerical analyses of the drilling process in brittle rock by means of a BEM-DDM program (FRACOD 2D ) were carried out to study the induced fracture patterns. These fracture patterns were compared with similar results reported by other published studies and were found to be realistic. The correlation between strength and in-situ stresses could then be exploited to estimate the stresses and the location of core discing observed in boreholes where stress measurements were not available. A correction of the laboratory strength results was also proposed to take into account sample damage during drilling. Modelling of Brazilian tests shows that the calculated fracture patterns determine the strength of the models. This is different from the common assumption that failure occurs when the uniform tensile stress in the sample reaches the tensile strength of the rock material. Based on the modelling results, new Brazilian tests were carried out on samples from borehole MIZ-1 that confirmed the failure mechanism numerically observed. A numerical study of the fracture patterns induced by removal of the overburden on a large scale produces fracture patterns and stress distributions corresponding to observations in crystalline hard rock in

  15. Residual stress development and relief in high strength aluminium alloys using standard and retrogression thermal treatments

    OpenAIRE

    Robinson, J.S; Tanner, D.A

    2003-01-01

    peer-reviewed Residual stresses develop in the aluminium alloy 7010 when the material is quenched from the solution heat treatment temperature. Residual stress measurements have been made using the X-ray diffraction technique and a longitudinal split sawcut method to determine the magnitude of residual stress that develops in specimens sectioned from large open die forgings as a result of (a) quenching these specimens into water at different temperatures, and (b) cold water quenching from ...

  16. Comparison of residual stresses in sand- and chill casting of ductile cast iron wind turbine main shafts

    International Nuclear Information System (INIS)

    Sonne, M R; Hattel, J H; Frandsen, J O

    2015-01-01

    In this work, simulations of pouring, solidification and cooling, and residual stress evolution of sand and chill cast wind turbine main shafts is performed. The models are made in the commercial software MAGMAsoft. As expected, the cooling rate of the sand casting is shown to be much lower than for the chill casting, resulting in a very course microstructure. From the simulations the nodule count is found to be 17 nodules per mm 2 and 159 nodules per mm 2 for the sand and chill casting, respectively, in the critical region of the main bearing seat. This is verified from nodule counts performed on the real cast main shafts. Residual stress evaluations show an overall increase of the maximum principal stress field for the chill casting, which is expected. However, the stresses are found to be in compression on the surface of the chill cast main shaft, which is unforeseen. (paper)

  17. Spatial and Temporal Variations in Earthquake Stress Drop on Gofar Transform Fault, East Pacific Rise: Implications for Fault Strength

    Science.gov (United States)

    Moyer, P. A.; Boettcher, M. S.; McGuire, J. J.; Collins, J. A.

    2017-12-01

    During the last five seismic cycles on Gofar transform fault on the East Pacific Rise, the largest earthquakes (6.0 ≤ Mw ≤ 6.2) have repeatedly ruptured the same fault segment (rupture asperity), while intervening fault segments host swarms of microearthquakes. Previous studies on Gofar have shown that these segments of low (≤10%) seismic coupling contain diffuse zones of seismicity and P-wave velocity reduction compared with the rupture asperity; suggesting heterogeneous fault properties control earthquake behavior. We investigate the role systematic differences in material properties have on earthquake rupture along Gofar using waveforms from ocean bottom seismometers that recorded the end of the 2008 Mw 6.0 seismic cycle.We determine stress drop for 117 earthquakes (2.4 ≤ Mw ≤ 4.2) that occurred in and between rupture asperities from corner frequency derived using an empirical Green's function spectral ratio method and seismic moment obtained by fitting the omega-square source model to the low frequency amplitude of earthquake spectra. We find stress drops from 0.03 to 2.7 MPa with significant spatial variation, including 2 times higher average stress drop in the rupture asperity compared to fault segments with low seismic coupling. We interpret an inverse correlation between stress drop and P-wave velocity reduction as the effect of damage on earthquake rupture. Earthquakes with higher stress drops occur in more intact crust of the rupture asperity, while earthquakes with lower stress drops occur in regions of low seismic coupling and reflect lower strength, highly fractured fault zone material. We also observe a temporal control on stress drop consistent with log-time healing following the Mw 6.0 mainshock, suggesting a decrease in stress drop as a result of fault zone damage caused by the large earthquake.

  18. Fear of pain and cortisol reactivity predict the strength of stress-induced hypoalgesia

    NARCIS (Netherlands)

    Timmers, Inge; Kaas, Amanda L.; Quaedflieg, Conny Wem; Biggs, Emma E.; Smeets, Tom; de Jong, Jeroen R.

    2018-01-01

    BACKGROUND: Acute stress can have an effect on pain sensitivity, yet the direction of the effect - whether it is hypoalgesic or hyperalgesic - is mixed across studies. Moreover, which part of the stress response influences pain sensitivity is still unclear. In the current experimental study, we aim

  19. Impacts of the Mesoscale Ocean-Atmosphere Coupling on the Peru-Chile Ocean Dynamics: The Current-Induced Wind Stress Modulation

    Science.gov (United States)

    Oerder, V.; Colas, F.; Echevin, V.; Masson, S.; Lemarié, F.

    2018-02-01

    The ocean dynamical responses to the surface current-wind stress interaction at the oceanic mesoscale are investigated in the South-East Pacific using a high-resolution regional ocean-atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current-stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.

  20. Effect of shear span, concrete strength and strrup spacing on behavior of pre-stressed concrete beams

    International Nuclear Information System (INIS)

    Ahmad, S.; Bukhari, I.A.

    2007-01-01

    The shear strength of pre-stressed concrete beams is one of the most important factors to be considered in their design. The available data on shear behavior of pre-tensioned prestressed concrete beams is very limited. In this experimental study, pre-tensioned prestressed concrete I-beams are fabricated with normal and high- strength concretes, varying stirrup spacing and shear span-to-depth ratios. 1Wenty one I-beam specimens that are 300 mm deep and 3745-4960mm long are tested up to failure while deflections, cracking pattern, cracking and failure loads were recorded. The research results are compared with ACI 318-02 and Structure Analysis Program, Response 2000. It was observed that with the decrease in concrete strength, failure mode of prestressed concrete beams changes from flexure shear to web shear cracking for values of shear span-to-depth ratio less than 4.75. Increase in stirrup spacing decreased the effectiveness of stirrups in transmitting shear across crack as a result of which failure mode is changed to web shear cracking especially for beams with lower values of shear span-to-depth ratios. ACI code underestimates the shear carrying capacity of prestressed concrete beams with lower values of shear span- to-depth ratios. Response 2000 can be used more effectively in predicting shear behavior of normal strength prestressed concrete beams. (author)

  1. Cyclic Strain Resistance, Stress Response, Fatigue Life, and Fracture Behavior of High Strength Low Alloy Steel 300 M

    Science.gov (United States)

    Manigandan, K.; Srivatsan, T. S.; Tammana, Deepthi; Poorgangi, Behrang; Vasudevan, Vijay K.

    2014-05-01

    The focus of this technical manuscript is a record of the specific role of microstructure and test specimen orientation on cyclic stress response, cyclic strain resistance, and cyclic stress versus strain response, deformation and fracture behavior of alloy steel 300 M. The cyclic strain amplitude-controlled fatigue properties of this ultra-high strength alloy steel revealed a linear trend for the variation of log elastic strain amplitude with log reversals-to-failure, and log plastic strain amplitude with log reversals-to-failure for both longitudinal and transverse orientations. Test specimens of the longitudinal orientation showed only a marginal improvement over the transverse orientation at equivalent values of plastic strain amplitude. Cyclic stress response revealed a combination of initial hardening for the first few cycles followed by gradual softening for a large portion of fatigue life before culminating in rapid softening prior to catastrophic failure by fracture. Fracture characteristics of test specimens of this alloy steel were different at both the macroscopic and fine microscopic levels over the entire range of cyclic strain amplitudes examined. Both macroscopic and fine microscopic observations revealed fracture to be a combination of both brittle and ductile mechanisms. The underlying mechanisms governing stress response, deformation characteristics, fatigue life, and final fracture behavior are presented and discussed in light of the competing and mutually interactive influences of test specimen orientation, intrinsic microstructural effects, deformation characteristics of the microstructural constituents, cyclic strain amplitude, and response stress.

  2. Effects of trade-wind strength and direction on the leeside circulations and rainfall of the island of Hawaii

    Science.gov (United States)

    Yang Yang; Yi-Leng Chen; Francis M. Fujioka

    2009-01-01

    The leeside circulations and weather of the island of Hawaii were studied from the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) land surface model simulations for eight strong (∼7.9 m s−1) and eight weak (∼5.2 m s−1) trade-wind days and for five days with southeasterly trades (∼7.1 m s

  3. The influence of cellular structures on flow stress of high strength components manufactured using SLM

    DEFF Research Database (Denmark)

    Mahshid, Rasoul; Hansen, Hans Nørgaard; Loft Højbjerre, Klaus

    2016-01-01

    Additive manufacturing has shown significant improvement in material and machines for high-quality solid freeform fabrication processes such as selective laser melting (SLM). In particular, manufacturing lattice structures using the SLM procedure is of interest. This research examines the effect...... of cellular materials on compression strength. The specimens are manufactured additively using industrial 3D printing systems from high-strength alloy. The material has the right mechanical properties for manufacturing tool components. This includes samples with solid and lattice structures. The Compression...

  4. Reliability of CRBR primary piping: critique of stress-strength overlap method for cold-leg inlet downcomer

    International Nuclear Information System (INIS)

    Bari, R.A.; Buslik, A.J.; Papazoglou, I.A.

    1976-04-01

    A critique is presented of the strength-stress overlap method for the reliability of the CRBR primary heat transport system piping. The report addresses, in particular, the reliability assessment of WARD-D-0127 (Piping Integrity Status Report), which is part of the CRBR PSAR docket. It was found that the reliability assessment is extremely sensitive to the assumed shape for the probability density function for the strength (regarded as a random variable) of the cold-leg inlet downcomer section of the primary piping. Based on the rigorous Chebyschev inequality, it is shown that the piping failure probability is less than 10 -2 . On the other hand, it is shown that the failure probability can be much larger than approximately 10 -13 , the typical value put forth in WARD-D-0127

  5. ION KINETIC ENERGY CONSERVATION AND MAGNETIC FIELD STRENGTH CONSTANCY IN MULTI-FLUID SOLAR WIND ALFVÉNIC TURBULENCE

    Energy Technology Data Exchange (ETDEWEB)

    Matteini, L.; Horbury, T. S.; Schwartz, S. J. [The Blackett Laboratory, Imperial College London, SW7 2AZ (United Kingdom); Pantellini, F. [LESIA, Observatoire de Paris, CNRS, UPMC, Universit Paris-Diderot, 5 Place Jules Janssen, F-92195 Meudon (France); Velli, M. [Department of Earth, Planetary, and Space Sciences, UCLA, California (United States)

    2015-03-20

    We investigate the properties of plasma fluid motion in the large-amplitude, low-frequency fluctuations of highly Alfvénic fast solar wind. We show that protons locally conserve total kinetic energy when observed from an effective frame of reference comoving with the fluctuations. For typical properties of the fast wind, this frame can be reasonably identified by alpha particles which, due to their drift with respect to protons at about the Alfvén speed along the magnetic field, do not partake in the fluid low-frequency fluctuations. Using their velocity to transform the proton velocity into the frame of Alfvénic turbulence, we demonstrate that the resulting plasma motion is characterized by a constant absolute value of the velocity, zero electric fields, and aligned velocity and magnetic field vectors as expected for unidirectional Alfvénic fluctuations in equilibrium. We propose that this constraint, via the correlation between velocity and magnetic field in Alfvénic turbulence, is the origin of the observed constancy of the magnetic field; while the constant velocity corresponding to constant energy can only be observed in the frame of the fluctuations, the corresponding constant total magnetic field, invariant for Galilean transformations, remains the observational signature in the spacecraft frame of the constant total energy in the Alfvén turbulence frame.

  6. Study on fatigue strength of specimens with stress concentrators accounting for inelastic cyclic strains

    International Nuclear Information System (INIS)

    Troshchenko, V.T.; Khamaza, L.A.; Mishchenko, Yu.D.

    1978-01-01

    A possibility of plotting the fatigue curves for structural elements with stress concentrators was examined according to the results of testing smooth specimens made of 1Kh2M steel. The technique has been suggested, based on using the Neuber formula, while taking into account the dependence of the effective coefficient of stresses concentration on the number of cycles prior to failure. A good agreement between the calculated and the experimental data has been obtained

  7. Effects of low strength pedaling exercise on stress sensitivity and pain threshold

    OpenAIRE

    坂野, 裕洋

    2017-01-01

     This study conducted a comparative assessment of the effects of low intensity lower limb pedaling exercise on the stress sensitivity and pain threshold in healthy subjects and those with chronic stiff neck or lower back pain. The results showed a reduction in pain threshold depending on the applied mechanical stress in both healthy and chronic pain groups. The individuals with chronic pain felt pain more intensely compared to the healthy individuals, and showed a significant reduction in pai...

  8. Use of anabolic androgenic steroids produces greater oxidative stress responses to resistance exercise in strength-trained men

    Directory of Open Access Journals (Sweden)

    Hamid Arazi

    Full Text Available The aim of this study was to determine the effect of anabolic androgenic steroids (AAS use on oxidative stress responses to a single session of resistance exercise in strength-trained men. Twenty-three strength trained men, with 11 self-reporting regular AAS use and 12 self-reporting never taking AAS (NAAS volunteered to participate in this study. Blood draws were obtained pre and post resistance exercise in order to evaluate changes in oxidative stress biomarkers levels (i.e., 8-hydroxy-2-deoxyguanosine [8-OHdG], malondialdehyde [MDA], and nitric oxide [NO], antioxidant defense systems (i.e., glutathione peroxidase [GPx] and catalase [CAT], and glucose (GLU levels. The AAS users had higher level of 8-OHdG (77.3 ± 17 vs. 57.7 ± 18.2 ng/mg, MDA (85.6 ± 17.8 vs. 52.3 ± 15.1 ng/mL, and GPx (9.1 ± 2.3 vs. 7.1 ± 1.3 mu/mL compared to NAAS at pre exercise (p < 0.05. Both the experimental groups showed increases in 8-OHdG (p = 0.001, MDA (p = 0.001, GPx (p = 0.001, NO (p = 0.04, CAT (p = 0.02 and GLU (p = 0.001 concentrations after resistance exercise, and the AAS group indicated significant differences in 8-OHdG (p = 0.02 and MDA (p = 0.05 concentrations compared with NAAS users at post exercise. In conclusion, use of AAS is associated with alterations in immune function resulting in oxidative stress, and cell damage; however, high-intensity resistance exercise could increase greater oxidative stress biomarkers in strength-trained men. Keywords: ROS, Strength exercise, Anabolic

  9. Stress-deformed state of cylindrical specimens during indirect tensile strength testing

    Directory of Open Access Journals (Sweden)

    Levan Japaridze

    2015-10-01

    Full Text Available In this study, the interaction between cylindrical specimen made of homogeneous, isotropic, and linearly elastic material and loading jaws of any curvature is considered in the Brazilian test. It is assumed that the specimen is diametrically compressed by elliptic normal contact stresses. The frictional contact stresses between the specimen and platens are neglected. The analytical solution starts from the contact problem of the loading jaws of any curvature and cylindrical specimen. The contact width, corresponding loading angle (2θ0, and elliptical stresses obtained through solution of the contact problems are used as boundary conditions for a cylindrical specimen. The problem of the theory of elasticity for a cylinder is solved using Muskhelishvili's method. In this method, the displacements and stresses are represented in terms of two analytical functions of a complex variable. In the main approaches, the nonlinear interaction between the loading bearing blocks and the specimen as well as the curvature of their surfaces and the elastic parameters of their materials are taken into account. Numerical examples are solved using MATLAB to demonstrate the influence of deformability, curvature of the specimen and platens on the distribution of the normal contact stresses as well as on the tensile and compressive stresses acting across the loaded diameter. Derived equations also allow calculating the modulus of elasticity, total deformation modulus and creep parameters of the specimen material based on the experimental data of radial contraction of the specimen.

  10. Comparison of residual stresses in sand- and chill casting of ductile cast iron wind turbine main shafts

    DEFF Research Database (Denmark)

    Sonne, Mads Rostgaard; Frandsen, J. O.; Hattel, Jesper Henri

    2015-01-01

    In this work, simulations of pouring, solidification and cooling, and residual stress evolution of sand and chill cast wind turbine main shafts is performed. The models are made in the commercial software MAGMAsoft. As expected, the cooling rate of the sand casting is shown to be much lower than...... for the chill casting, resulting in a very course microstructure.From the simulations the nodule count is found to be 17 nodules per mm2 and 159 nodules permm2 for the sand and chill casting, respectively, in the critical region of the main bearing seat.This is verified from nodule counts performed on the real...... cast main shafts. Residual stressevaluations show an overall increase of the maximum principal stress field for the chill casting,which is expected. However, the stresses are found to be in compression on the surface of thechill cast main shaft, which is unforeseen....

  11. Weathering effects on tensile and stress rupture strength of glass fiber reinforced vinylester and epoxy thermoset pipes

    Science.gov (United States)

    Nizamuddin, Syed

    Glass fiber reinforced vinylester (GFRE) and epoxy (GFRE) pipes have been used for more than three decades to mitigate corrosion problems in oil fields, chemical and industrial plants. In these services, both GFRV and GFRE pipes are exposed to various environmental conditions. Long-term mechanical durability of these pipes after exposure to environmental conditions, which include natural weathering exposure to seasonal temperature variation, sea water, humidity and other corrosive fluids like crude oil, should be well known. Although extensive research has been undertaken, several major issues pertaining to the performance of these pipes under a number of environmental conditions still remain unresolved. The main objective of this study is to investigate the effects of natural weathering, combined natural weathering with seawater and crude oil exposure, for time periods ranging from 3 to 36 months respectively, on the tensile and stress rupture behavior of GFRV and GFRE pipes. Ring specimens are machined from GFRV and GFRE pipes and tested before and after exposure to different weathering conditions prevalent in the eastern region (Dhahran) of Saudi Arabia and present under service conditions. The natural weathering and combined natural weathering with crude oil exposure of GFRV specimens revealed increased tensile strength even after 36 months of exposure when compared with that of the as received samples. However, the combined natural weathering with seawater exposure of GFRV samples revealed better tensile behavior till 24 months of exposure, and after 36 months their tensile strength was seen to be below that of the as received GFRV samples. The stress rupture behavior of natural weather exposed GFRV samples showed an improvement after 12 months of exposure and it decreased after 24 and 36 months of exposure when compared with the as received GFRV samples. The combined natural weathering with crude oil and seawater exposure of GFRV sample revealed improved

  12. Differentiation of molecular chain entanglement structure through laser Raman spectrum measurement of High strength PET fibers under stress

    Science.gov (United States)

    Go, D.; Takarada, W.; Kikutani, T.

    2017-10-01

    The aim of this study was to investigate the mechanism for the improvement of mechanical properties of poly(ethylene terephthalate) (PET) fibers based on the concept of controlling the state of molecular entanglement. For this purpose, five different PET fibers were prepared through either the conventional melt spinning and drawing/annealing process or the high-speed melt spinning process. In both cases, the melt spinning process was designed so as to realize different Deborah number conditions. The prepared fibers were subjected to the laser Raman spectroscopy measurement and the characteristics of the scattering peak at around 1616 cm-1, which corresponds to the C-C/C=C stretching mode of the aromatic ring in the main chain, were investigated in detail. It was revealed that the fibers drawn and annealed after the melt spinning process of lower Deborah number showed higher tensile strength as well as lower value of full width at half maximum (FWHM) in the laser Raman spectrum. Narrow FWHM was considered to represent the homogeneous state of entanglement structure, which may lead to the higher strength and toughness of fibers because individual molecular chains tend to bare similar level of tensile stress when the fiber is stretched. In case of high-speed spun fibers prepared with a high Deborah number condition, the FWHM was narrow presumably because much lower tensile stress in comparison with the drawing/annealing process was applied when the fiber structure was developed, however the value increased significantly upon applying tensile load to the fibers during the laser Raman spectrum measurement. From these results, it was concluded that the Laser Raman spectroscopy could differentiate molecular chain entanglement structure of various fiber samples, in that low FWHM, which corresponds to either homogeneous state of molecular entanglement or lower level of mean residual stress, and small increase of FWTH upon applying tensile stress are considered to be the key

  13. Effects on stress rupture life and tensile strength of tin additions to Inconel 718

    Science.gov (United States)

    Dreshfield, R. L.; Johnson, W.

    1982-01-01

    Because Inconel 718 represents a major use of columbium and a large potential source of columbium for aerospace alloys could be that of columbium derived from tin slags, the effects of tin additions to Inconel 718 at levels which might be typical of or exceed those anticipated if tin slag derived columbium were used as a melting stock were investigated. Tin was added to 15 pound Inconel 718 heats at levels varying from none added to approximately 10,000 ppm (1 wt%). Limited 1200 F stress rupture testing was performed at stresses from 68,000 to 115,000 psi and a few tensile tests were performed at room temperature, 800 and 1200 F. Additions of tin in excess of 800 ppm were detrimental to ductility and stress rupture life.

  14. Interpretation of bend strength increase of graphite by the couple-stress theory

    International Nuclear Information System (INIS)

    Tang, P.Y.

    1981-05-01

    This paper presents a continued evaluation of the applicability of the couple-stress constitutive theory to graphite. The evaluation is performed by examining four-point bend and uniaxial tensile data of various sized cylindrical and square specimens for three grades of graphites. These data are superficially inconsistent and, usually, at variance with the predictions of classical theories. Nevertheless, this evaluation finds that they can be consistently interpreted by the couple-stress theory. This is compatible with results of an initial evaluation that considered one size of cylindrical specimen for H-451 graphite

  15. Residual stress and bending strength of ZnO films deposited on polyimide sheet by RF sputtering system

    Energy Technology Data Exchange (ETDEWEB)

    Kusaka, Kazuya, E-mail: kusaka@tokushima-u.ac.jp [Institute of Technology and Science, Tokushima University, 2-1, Minamijosanjima, Tokushima, Tokushima 7708506 (Japan); Maruoka, Yutaka, E-mail: ymaruoka1116@gmail.com [Graduate School of Advanced Technology and Science, Tokushima University, 2-1, Minamijosanjima, Tokushima, Tokushima 7708506 (Japan); Matsue, Tatsuya, E-mail: tmatsue@mat.niihama-nct.ac.jp [Department of Environmental Materials Engineering National Institute of Technology, NIIHAMA College, 7-1, Yakumo-cho, Niihama, Ehime 7928580 (Japan)

    2016-05-15

    Zinc oxide (ZnO) films were deposited on a soft polyimide sheet substrate by radio frequency sputtering with a ZnO powder target, and the films' crystal orientations and residual stress were investigated using x-ray diffraction as a function of substrate temperature. C-axis oriented ZnO films were achieved using this ZnO powder target method. The ZnO films exhibited high compressive residual stresses between −0.7 and −1.4 GPa. Finally, the authors examined the strength of the obtained film by applying tensile bending loads. No cracks were observed on the surfaces of the ZnO films after a bending test using cylinders with diameters >25 mm. After a bending test using a cylinder with a diameter of 19 mm, large cracks were formed on the films. Therefore, the authors concluded that the tensile bending strength of the obtained films was greater than ∼420 MPa.

  16. Effect of yield strength on stress corrosion crack propagation under PWR and BWR environments of hardened stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Castano, M.L.; Garcia, M.S.; Diego, G. de; Gomez-Briceno, D. [CIEMAT, Nuclear Fission Department, Structural Materials Program, Avda. Complutense 22, 28040 Madrid (Spain)

    2004-07-01

    stress corrosion cracking of austenitic stainless steels (SS) and to quantify the effect on the crack propagation rate, an experimental research program was performed using cold and warm worked 304, 316L and 347 SS. Stress corrosion crack growth rate tests, under BWR and PWR environments have been carried out. The results obtained have permitted to determine the yield strength effect in the crack propagation of austenitic stainless steels in PWR and BWR conditions. In addition, similarities on cold work and radiation hardening in enhancing the yield strength and the stress corrosion cracking propagation at high temperature water have been evaluated. (authors)

  17. Transformer sound level caused by core magnetostriction and winding stress displacement variation

    Directory of Open Access Journals (Sweden)

    Chang-Hung Hsu

    2017-05-01

    Full Text Available Magnetostriction caused by the exciting variation of the magnetic core and the current conducted by the winding wired to the core has a significant result impact on a power transformer. This paper presents the sound of a factory transformer before on-site delivery for no-load tests. This paper also discusses the winding characteristics from the transformer full-load tests. The simulation and the measurement for several transformers with capacities ranging from 15 to 60 MVA and high voltage 132kV to low voltage 33 kV are performed. This study compares the sound levels for transformers by no-load test (core/magnetostriction and full-load test (winding/displacement ε. The difference between the simulated and the measured sound levels is about 3dB. The results show that the sound level depends on several parameters, including winding displacement, capacity, mass of the core and windings. Comparative results of magnetic induction of cores and the electromagnetic force of windings for no-load and full-load conditions are examined.

  18. Influence of mean stress on fatigue strength of ferritic-pearlite ductile cast iron with small defects

    Science.gov (United States)

    Deguchi, T.; Kim, H. J.; Ikeda, T.; Yanase, K.

    2017-05-01

    Because of their excellent mechanical properties, low cost and good workability, the application of ductile cast iron has been increased in various industries such as the automotive, construction and rail industries. For safety designing of the ductile cast iron component, it is necessary to understand the effect of stress ratio, R, on fatigue limit of ductile cast iron in the presence of small defects. Correspondingly in this study, rotating bending fatigue tests at R = -1 and tension-compression fatigue tests at R = -1 and 0.1 were performed by using a ferritic-pearlitic ductile cast iron. To study the effects of small defects, we introduced a small drilled hole at surface of a specimen. The diameter and depth of a drilled hole were 50, 200 and 500 μm, respectively. The non-propagating cracks emanating from graphite particles and holes edge were observed at fatigue limit, irrespective of the value of stress ratio. From the microscopic observation of crack propagation behavior, it can be concluded that the fatigue limit is determined by the threshold condition for propagation of a small crack. It was found that the effect of stress ratio on the fatigue limit of ductile cast iron with small defects can be successfully predicted based on \\sqrt {area} parameter model. Furthermore, a use of the tensile strength, σ B, instead of the Vickers hardness, HV, is effective for fatigue limit prediction.

  19. Direct relationship between breakdown strength and tracking index of composites

    DEFF Research Database (Denmark)

    Madsen, Søren Find; Henriksen, Mogens; Holbøll, Joachim

    2006-01-01

    . The breakdown field strength of specimens cut from similar samples is determined by a new method capable of estimating the stressed volume. The results from the two tests are finally compared and incorporated in a single analytical formula. All test specimens are supplied by Danish manufacturers of wind turbine...

  20. Modelling the effect of coating on the stresses and microstructure evolution in chill casting of wind turbine main shafts

    DEFF Research Database (Denmark)

    Sonne, Mads Rostgaard; Thorborg, J.; Hattel, Jesper Henri

    2017-01-01

    The purpose of the present work is to quantify the effect of the inside coating on chills for casting of large wind turbine main shafts with respect to the evolution of internal stresses. These are known to affect the lifetime of the chills, and this is a major cost for the foundries today. Simul......, it is concluded that the material quality obtained from casting the main shafts in chills (and hence the performance of the part) is still much better than for sand casting, even though a very thick layer of coating is applied. Copyright © 2017 John Wiley & Sons, Ltd....... in the simulations. The outcome is validated by comparisons with samples taken out from a critical region of main shafts cast in sand and in chills. The results reveal minor reductions in the maximum principal stresses on the inner and outer surfaces of the chill of 3.1% and 18.5%, respectively, from changing...

  1. Sulphide stress corrosion behaviour of a nickel coated high-strength low-alloyed steel

    Energy Technology Data Exchange (ETDEWEB)

    Salvago, G; Fumagalli, G; Cigada, A; Scolari, P

    1987-01-01

    The sulphide stress corrosion cracking (SSCC) of the quenched and tempered AISI 4137 H steel either bare or coated with nickel alloys was examined. Both traditional electrochemical and linear elastic fracture mechanics methods were used to examine cracking in the NACE environment and in environments simulating the geothermal fluids found in the area of Larderello in Italy. Some tests were carried out on a geothermal well in Ferrara. High nickel content coatings seem to increase the SSCC resistance of the AISI 4137-H steel. Galvanic couplings effects are possible factors responsible for the behaviour in SSCC.

  2. Osmotic stress regulates the strength and kinetics of sugar binding to the maltoporin channel

    International Nuclear Information System (INIS)

    Gurnev, Philip A; Bezrukov, Sergey M; Harries, Daniel; Adrian Parsegian, V

    2010-01-01

    We study the effect of osmotic stress, exerted by salts, on carbohydrate binding to the sugar-specific bacterial channel maltoporin. When the channel is reconstituted into planar lipid bilayers, single events of its occlusion by sugar are seen as transient interruptions in the flow of small ions. We find that, for most salts, changes in the free energy of maltoporin-sugar binding vary linearly with solution osmotic pressure. Such a change in binding with solution osmolarity indicates that for each salt a constant number of salt-excluding water molecules is released upon sugar-maltoporin association at all salt concentrations. We find that larger numbers of water molecules are released upon binding of the cyclic carbohydrate β-cyclodextrin (CD) than upon binding of the corresponding linear homologue maltoheptaose (m7). Remarkably, the extent to which salts affect the binding constants and rates depends sensitively on the type of salt; dehydration in solutions of different anions corresponds to the Hofmeister series. In sodium sulfate solutions, CD and m7 respectively release about 120 and 35 salt-excluding water molecules; in sodium chloride solutions, 35 and 15 waters. No water release is observed with sodium bromide. Finally, by adding adamantane, known to form an inclusion complex with CD, we can infer that CD not only dehydrates but also undergoes a conformational change upon binding to the channel. As a practical outcome, our results also demonstrate how osmotic stress can improve single-molecule detection of different solutes using protein-based nanopores.

  3. Restoration of strength despite low stress and abnormal imaging after Achilles injury.

    Science.gov (United States)

    Trudel, Guy; Doherty, Geoffrey P; Koike, Yoichi; Ramachandran, Nanthan; Lecompte, Martin; Dinh, Laurent; Uhthoff, Hans K

    2009-11-01

    To determine the usefulness of clinical imaging in predicting the mechanical properties of rabbit Achilles tendons after acute injury. We created a 2 x 7-mm full-thickness central tendon defect in one Achilles tendon of healthy rabbits. Rabbits in groups of 10 were killed immediately and 4 and 8 wk after surgery (n = 30). We then performed magnetic resonance (MR) imaging, ultrasonography (US), bone mineral densitometry (BMD), and mechanical testing to failure using a dual-cryofixation assembly on experimental and contralateral tendons. The main outcome measures included tendon dimensions, optical density (OD) of T1-weighted, proton density (PD), and T2-weighted MR sequences, US focal abnormalities, BMD of the calcaneus, and stress and peak load to failure. On MR imaging and US, all dimensions of the injured tendons after 2 wk and more were greater than those of the contralateral tendons (P tendons at both 4 wk (39 +/- 9 vs 77 +/- 16 N x mm(-2)) and 8 wk (58 +/- 6 vs 94 +/- 26 N x mm(-2); P tendons, higher T1-weighted OD correlated with lower peak load (r = -0.46; P tendon of lower stress. These findings support progressive physical loading 4 wk after an Achilles tendon injury. T1-weighted OD constituted a marker of tendon mechanical recovery.

  4. Reading the Bible for guidance, comfort, and strength during stressful life events.

    Science.gov (United States)

    Hamilton, Jill B; Moore, Angelo D; Johnson, Khishaana A; Koenig, Harold G

    2013-01-01

    The use of religious practices to promote mental health among African Americans is well documented. African Americans are more likely to report strong religious affiliations and to use religion over prescribed medications for mental health problems. However, few studies have explored how African Americans use religious practices in response to stressful life events. The aim of this study is to examine how African American women and men find comfort in using scripture passages from The Bible. Fifty-four African American adults residing in the Southeastern United States participated in a qualitative descriptive study using open-ended semistructured interviews. Participants were asked to describe their use of scripture passages from The Bible and the personal meanings associated with these scriptures in the context of a family death or life-threatening illness. These participants used scripture passages categorized as God as Protector, God as Beneficent, Praise and Thanksgiving, God as Healer, Memory of Forefathers, Prayers to God, and Life after Death. Few gender differences were noted. However, women were more likely to use scripture passages of God as Protector and Life after Death, whereas men were more likely to use God as Beneficent and God as Healer. The religious practice of reading scripture passages from The Bible is a mental health-promoting strategy used during stressful life events. The findings of this study have practical uses for nurses and can be used to inform acceptable and sensitive approaches in addressing mental health issues and spiritual care needs in African American patients.

  5. A Technique for Mitigating Thermal Stress and Extending Life Cycle of Power Electronic Converters Used for Wind Turbines

    Directory of Open Access Journals (Sweden)

    Canras Batunlu

    2015-11-01

    Full Text Available Over the last two decades, various models have been developed to assess and improve the reliability of power electronic conversion systems (PECs with a focus on those used for wind turbines. However, only few studies have dealt with mitigating the PECs thermo-mechanical effects on their reliability taking into account variations in wind characteristics. This work critically investigates this issue and attempts to offer a mitigating technique by, first, developing realistic full scale (FS and partial scale (PS induction generator models combined with two level back-to-back PECs. Subsequently, deriving a driving algorithm, which reduces PEC’s operating temperature by controlling its switching patterns. The developed switching procedure ensures minimum temperature fluctuations by adapting the variable DC link and system’s frequency of operation. It was found for both FS and PS topologies, that the generator side converters have higher mean junction temperatures where the grid side ones have more fluctuations on their thermal profile. The FS and PS cycling temperatures were reduced by 12 °C and 5 °C, respectively. Moreover, this led to a significant improvement in stress; approximately 27 MPa stress reduction for the FS induction generator PEC.

  6. High Load Ratio Fatigue Strength and Mean Stress Evolution of Quenched and Tempered 42CrMo4 Steel

    Science.gov (United States)

    Bertini, Leonardo; Le Bone, Luca; Santus, Ciro; Chiesi, Francesco; Tognarelli, Leonardo

    2017-08-01

    The fatigue strength at a high number of cycles with initial elastic-plastic behavior was experimentally investigated on quenched and tempered 42CrMo4 steel. Fatigue tests on unnotched specimens were performed both under load and strain controls, by imposing various levels of amplitude and with several high load ratios. Different ratcheting and relaxation trends, with significant effects on fatigue, are observed and discussed, and then reported in the Haigh diagram, highlighting a clear correlation with the Smith-Watson-Topper model. High load ratio tests were also conducted on notched specimens with C (blunt) and V (sharp) geometries. A Chaboche model with three parameter couples was proposed by fitting plain specimen cyclic and relaxation tests, and then finite element analyses were performed to simulate the notched specimen test results. A significant stress relaxation at the notch root became clearly evident by reporting the numerical results in the Haigh diagram, thus explaining the low mean stress sensitivity of the notched specimens.

  7. Rigid MATLAB drivetrain model of a 500 kW wind turbine for predicting maximum gear tooth stresses in a planetary gearbox using multibody gear constraints

    DEFF Research Database (Denmark)

    Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

    2014-01-01

    multiple planetary gears are not taken into account. Finite Element Method (FEM) calculations show that when the wind turbine runs close to the maximum wind speed, the maximum gear tooth stress is in the range of 500–700 MPa, which is considered to be realistic using a “worst-case” method. The presented...... for not only transferring torque but also for calculating the gear tooth and internal body reaction forces. The method is appropriate for predicting gear tooth stresses without considering all the complexity of gear tooth geometries. This means that, e.g. gear tooth load-sharing and load-distribution among...

  8. Maternal obesity and perinatal oxidative stress: the strength of the association.

    Science.gov (United States)

    Negro, S; Boutsikou, T; Briana, D D; Tataranno, M L; Longini, M; Proietti, F; Bazzini, F; Dani, C; Malamitsi-Puchner, A; Buonocore, G; Perrone, S

    2017-01-01

    Maternal obesity is a chronic inflammatory state, which has been shown to induce increased levels of free fatty acids, reactive oxygen species and inflammatory cells. Recent evidence reveals increased levels of lipid peroxidation products in the plasma of obese women during pregnancy. The aim of this study was to test the hypothesis that maternal overweight or obesity is associated with increased oxidative stress (OS) in offspring. Two hundred and forty-five pregnant women and their newborns were prospectively enrolled. Mothers were divided in two groups: lean control - LC (n=175, Group I); overweight or obese (n=70, Group II) according to BMI ≥ 25 before pregnancy. Cord blood F2-isoprostanes (F2-IsoPs), as reliable markers of OS, were measured in all newborns. Lower 1 minute APGAR score and higher weight at discharge were found in Group II neonates, compared to those of Group I (p less than 0.05). Small for gestational age (SGA) newborns of both groups showed increased levels of F2-IsoPs than appropriate (AGA) or large (LGA) for gestational age (GA) (p less than 0.01). SGA newborns of Group II had higher F2-IsoPs levels compared to SGA of Group I (p less than 0.01), which were significantly correlated to maternal BMI at the end of pregnancy (r=0.451, p less than 0.01). Multivariate regression analysis corrected for confounding factors, showed that maternal overweight or obesity was significantly associated with high F2-IsoPs levels in SGA offspring (p less than 0.01). Maternal overweight or obesity is associated with increased OS in their SGA newborns. Data suggest the need of antioxidant protection for both mothers during pregnancy and infants soon after birth.

  9. The relationship between the microwave radar cross section and both wind speed and stress: Model function studies using Frontal Air-Sea Interaction Experiment data

    Science.gov (United States)

    Weissman, David E.; Davidson, Kenneth L.; Brown, Robert A.; Friehe, Carl A.; Li, Fuk

    1994-01-01

    The Frontal Air-Sea Interaction Experiment (FASINEX) provided a unique data set with coincident airborne scatterometer measurements of the ocean surface radar cross section (RCS)(at Ku band) and near-surface wind and wind stress. These data have been analyzed to study new model functions which relate wind speed and surface friction velocity (square root of the kinematic wind stress) to the radar cross section and to better understand the processes in the boundary layer that have a strong influence on the radar backscatter. Studies of data from FASINEX indicate that the RCS has a different relation to the friction velocity than to the wind speed. The difference between the RCS models using these two variables depends on the polarization and the incidence angle. The radar data have been acquired from the Jet Propulsion Laboratory airborne scatterometer. These data span 10 different flight days. Stress measurements were inferred from shipboard instruments and from aircraft flying at low altitudes, closely following the scatterometer. Wide ranges of radar incidence angles and environmental conditions needed to fully develop algorithms are available from this experiment.

  10. Effect of fabric structure and polymer matrix on flexural strength, interlaminar shear stress, and energy dissipation of glass fiber-reinforced polymer composites

    Science.gov (United States)

    We report the effect of glass fiber structure and the epoxy polymer system on the flexural strength, interlaminar shear stress (ILSS), and energy absorption properties of glass fiber-reinforced polymer (GFRP) composites. Four different GFRP composites were fabricated from two glass fiber textiles of...

  11. Coupled wave and surge modelling for the eastern Irish Sea and implications for model wind-stress

    Science.gov (United States)

    Brown, Jennifer M.; Wolf, Judith

    2009-05-01

    We revisit the surge of November 1977, a storm event which caused damage on the Sefton coast in NW England. A hindcast has been made with a coupled surge-tide-wave model, to investigate whether a wave-dependent surface drag is necessary for accurate surge prediction, and also if this can be represented by an optimised Charnock parameter. The Proudman Oceanographic Laboratory Coastal Modelling System-Wave Model (POLCOMS-WAM) has been used to model combined tides, surges, waves and wave-current interaction in the Irish Sea on a 1.85 km grid. This period has been previously thoroughly studied, e.g. Jones and Davies [Jones, J.E., Davies, A.M., 1998. Storm surge computations for the Irish Sea using a three-dimensional numerical model including wave-current interaction. Continental Shelf Research 18(2), 201-251] and we build upon this previous work to validate the POLCOMS-WAM model to test the accuracy of surge elevation predictions in the study area. A one-way nested approach has been set up from larger scale models to the Irish Sea model. It was demonstrated that (as expected) swell from the North Atlantic does not have a significant impact in the eastern Irish Sea. To capture the external surge generated outside of the Irish Sea a (1/9° by 1/6°) model extending beyond the continental shelf edge was run using the POLCOMS model for tide and surge. The model results were compared with tide gauge observations around the eastern Irish Sea. The model was tested with different wind-stress formulations including Smith and Banke [Smith, S.D., Banke, E.G., 1975. Variation of the surface drag coefficient with wind speed. Quarterly Journal of the Royal Meteorology Society, 101(429), 665-673] and Charnock [Charnock, H., 1955. Wind-stress on a water surface. Quarterly Journal of the Royal Meteorological Society, 81(350), 639-640]. In order to get a single parameterisation that works with wave-coupling, the wave-derived surface roughness length has been imposed in the surge model

  12. Mind-Body Interventions to Reduce Risk for Health Disparities Related to Stress and Strength Among African American Women: The Potential of Mindfulness-Based Stress Reduction, Loving-Kindness, and the NTU Therapeutic Framework.

    Science.gov (United States)

    Woods-Giscombé, Cheryl L; Black, Angela R

    2010-12-14

    In the current article, the authors examine the potential role of mind-body interventions for preventing or reducing health disparities in a specific group-African American women. The authors first discuss how health disparities affect this group, including empirical evidence regarding the influence of biopsychosocial processes (e.g., psychological stress and social context) on disparate health outcomes. They also detail how African American women's unique stress experiences as a result of distinct sociohistorical and cultural experiences related to race and gender potentially widen exposure to stressors and influence stress responses and coping behaviors. Using two independent, but related, frameworks (Superwoman Schema [SWS] and the Strong Black Woman Script [SBW-S]), they discuss how, for African American women, stress is affected by "strength" (vis-à-vis resilience, fortitude, and self-sufficiency) and the emergent health-compromising behaviors related to strength (e.g., emotional suppression, extraordinary caregiving, and self-care postponement). The authors then describe the potential utility of three mind-body interventions-mindfulness-based stress reduction (MBSR), loving-kindness meditation (LKM), and NTU psychotherapy-for specifically targeting the stress-, strength-, and contextually related factors that are thought to influence disparate outcomes for African American women. Self-awareness, self-care, inter- and intrapersonal restorative healing and a redefinition of inner strength may manifest through developing a mindfulness practice to decrease stress-related responses; using LKM to cultivate compassion and forgiveness for self and others; and the balance of independence and interdependence as a grounding NTU principle for redefining strength. The authors conclude with a discussion of potential benefits for integrating key aspects of the interventions with recommendations for future research.

  13. Role of multiaxial stress state in the hydrogen-assisted rolling-contact fatigue in bearings for wind turbines

    Directory of Open Access Journals (Sweden)

    J. Toribio

    2015-07-01

    Full Text Available Offshore wind turbines often involve important engineering challenges such as the improvement of hydrogen embrittlement resistance of the turbine bearings. These elements frequently suffer the so-called phenomenon of hydrogen-assisted rolling-contact fatigue (HA-RCF as a consequence of the synergic action of the surrounding harsh environment (the lubricant supplying hydrogen to the material and the cyclic multiaxial stress state caused by in-service mechanical loading. Thus the complex phenomenon could be classified as hydrogen-assisted rolling-contact multiaxial fatigue (HA-RC-MF. This paper analyses, from the mechanical and the chemical points of view, the so-called ball-on-rod test, widely used to evaluate the hydrogen embrittlement susceptibility of turbine bearings. Both the stress-strain states and the steady-state hydrogen concentration distribution are studied, so that a better elucidation can be obtained of the potential fracture places where the hydrogen could be more harmful and, consequently, where the turbine bearings could fail during their life in service.

  14. Structural experiment of wind turbine blades; Fushayo blade no zairyo rikigakuteki jikken kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Seki, K; Shimizu, Y; Kuroyanagi, H [Tokai University, Tokyo (Japan)

    1997-11-25

    Aluminum, GFRP and composite of aluminum coated with carbon as structural materials for wind turbine blades were bending-tested, to improve blade bending stiffness, understand stress conditions at each position, and clarify structural dynamic strength by the bending-failure test. It is possible to estimate stress conditions at each position from the test results of displacement and strain at each load. The test results with GFRP are well explained qualitatively by the boundary theory, known as a theory for composite materials. The test gives reasonable material strength data, useful for designing wind turbines of high functions and safety. The results of the blade bending-failure test are in good agreement with the calculated structural blade strength. It is also found that GFRP is a good material of high structural strength for wind turbines. 8 refs., 6 tabs.

  15. Barotropic Eulerian residual circulation in the Gulf of California due to the M{sub 2} tide and wind stress

    Energy Technology Data Exchange (ETDEWEB)

    Argote, M. L.; Lavin, M. F.; Amador, A. [Departamento de Oceanografia Fisica, CICESE, Ensenada, Baja California (Mexico)

    1998-07-01

    A vertically integrated, non-linear numerical model in finite differences is used to analyze two forcing mechanisms of the mean barotropic circulation in the Gulf of California: topographic rectification due to tidal currents (M{sub 2}) and wind stress. Under tidal forcing the nonlinearities of the momentum equations induce unorganized strong tidal induced residual currents (u{sub e} > 5 cm s{sup -}1) in the channels between the islands, and along-isobath anticyclonic circulation in the Northern Gulf, with speeds u{sub 3} < 2.5 cm s{sup -}1 over the edge of Delfin Basin. These numerical results are in agreement with analytical results, which indicate that the tidal-induced currents are mostly due to the advective terms, and that continuity and the Coriolis term (but regulated by bottom friction) are responsible for the along-isobath flow. The quadratic bottom friction plays a role in generating mean currents only in the very shallow area off the Colorado River Delta. The effect of wind stress was modeled by imposing upon the running M{sub 2} model a constant surface stress ( r = 0.016 Pa), from the NW for winter conditions and from the SE for summer conditions. The wind-induced circulation was obtained by averaging over a tidal cycle and then subtracting the tidal residuals. The two wind directions produce almost identical circulation patterns, but with opposite directions. For the NW wind stress, the main features of the predicted circulation are: (a) In the Northern Gulf an anticyclonic circulation pattern, with the strongest currents (up to {approx} 10 cm s-1) following the bathymetry of the rim of Delfin Basin, Wagner Basin and the mainland coast off Bahia Adair and Bahia San Jorge. There is also a southward flow along the peninsula coast, from the Colorado River to Bahia San Luis Gonzaga. (b) In the Southern Gulf, there is a strong flow ({approx} 10 to 15 cm s{sup -}1) to the SE over the continental shelf along the mainland coast. A somewhat less well

  16. Ultimate stress increase in unbonded tendons in post-tensioned indeterminate I-beams cast with high strength normal and self compacting concrete

    Directory of Open Access Journals (Sweden)

    Yousef Askari Dolatabad

    2018-06-01

    Full Text Available The use of un-bonded tendons is prevalent in post-tensioned concrete structures. Equations for prediction of stress in un-bonded tendons of post-tensioned normal (vibrating concrete flexural members have been given in various codes. They are based on experience and don’t account all of important parameters such as concrete strength (normal and high strength and its type (vibrating and non-vibrating concrete. Since self-compacting concrete (SCC is nearly a new innovation therefore, understanding the implementation of this type of non-vibrating concrete on the ultimate unbonded tendon stress is critical. For this aim, in this paper there are presented experimental results of six continuous un-bonded post-tensioned I-beams in two groups were casted and monitored by different electrical strain gauges. In the first tested group, the beams (UPN1-12, UPN1-18, UPN1-22 were consisting of high strength normal concrete (HSNC where as in the second group (UPS1-12, UPS1-18, UPS1-22 high strength self-compacting concrete (HSSCC were tested. The variables included the type of concrete and percentage of bounded non-prestressed steel. Experimental monitored results of ultimate stress increase in unbonded tendons are compared with predicted equations of different researchers and standards. It was found that, the proposed equation is in better agreement with the test results. The results of standard error of estimate Sy/x, indicates that for two types of HSCs, the ACI 318-2011 provides better estimates than AASHTO-2010 model whereas this model provides better estimates than BS 8110-97. Keywords: Post-tensioned, Unbonded tendons, Stress increase, High strength normal and self-compacting concrete, Continuous beams

  17. Monitoring the residual life of atomic power station equipment based on the indices of stress-corrosion strength of constructional materials

    International Nuclear Information System (INIS)

    Stepanov, I.A.

    1994-01-01

    The properties of a constructional material determining life are strength, plasticity, and crack resistance. Loss of properties occurs as the result of corrosion, temperature action, actual and residual stresses, and neutron and gamma-radiation. Corrosion leads to a decrease in thickness, loss of density, changes in the composition and structure of the surface layers, and a reduction in strength, plasticity, and crack resistance of constructional materials. The influence of temperature on the loss of properties of materials is revealed as possible phase and structural transformations of the metal and the surface layers and a reduction in the stress-rupture, plastic, and thermal-fatigue properties. The actual and residual stresses not only strengthen the influence of corrosive media but also directly determine the stress-rupture strength and cyclic life. The influence of neutron and gamma-radiation is based o the change in composition of the corrosive medium (radiolysis), radiation embrittlement of the material, and the change in properties of the surface and oxide layers. The authors discuss the concepts and design of automated monitoring systems for determining the fitness of the components of on atomic power plant

  18. Surface Buoyancy Fluxes and the Strength of the Subpolar Gyre

    Science.gov (United States)

    Hogg, A. M.; Gayen, B.

    2017-12-01

    Midlatitude ocean gyres have long been considered to be driven by the mechanical wind stress on the ocean's surface (strictly speaking, the potential vorticity input from wind stress curl). However, surface buoyancy forcing (i.e. heating/cooling or freshening/salinification) also modifies the potential vorticity at the surface. Here, we present a simple argument to demonstrate that ocean gyres may (in principle) be driven by surface buoyancy forcing. This argument is derived in two ways: A Direct Numerical Simulation, driven purely by buoyancy forcing, which generates strong nonlinear gyers in the absence of wind stress; and A series of idealised eddy-resolving numerical ocean model simulations, in which wind stress and buoyancy flux are varied independently and together, are used to understand the relative importance of these two types of forcing. In these simulations, basin-scale gyres and western boundary currents with realistic magnitudes, remain even in the absence of mechanical forcing by surface wind stress. These results support the notion that surface buoyancy forcing can reorganise the potential vorticity in the ocean in such a way as to drive basin-scale gyres. The role of buoyancy is stronger in the subpolar gyre than in the subtropical gyre. We infer that surface buoyancy fluxes are likely to play a contributing role in governing the strength, variability and predictability of the North Atlantic subpolar gyre.

  19. Temporal Changes in Stress Drop, Frictional Strength, and Earthquake Size Distribution in the 2011 Yamagata-Fukushima, NE Japan, Earthquake Swarm, Caused by Fluid Migration

    Science.gov (United States)

    Yoshida, Keisuke; Saito, Tatsuhiko; Urata, Yumi; Asano, Youichi; Hasegawa, Akira

    2017-12-01

    In this study, we investigated temporal variations in stress drop and b-value in the earthquake swarm that occurred at the Yamagata-Fukushima border, NE Japan, after the 2011 Tohoku-Oki earthquake. In this swarm, frictional strengths were estimated to have changed with time due to fluid diffusion. We first estimated the source spectra for 1,800 earthquakes with 2.0 ≤ MJMA < 3.0, by correcting the site-amplification and attenuation effects determined using both S waves and coda waves. We then determined corner frequency assuming the omega-square model and estimated stress drop for 1,693 earthquakes. We found that the estimated stress drops tended to have values of 1-4 MPa and that stress drops significantly changed with time. In particular, the estimated stress drops were very small at the beginning, and increased with time for 50 days. Similar temporal changes were obtained for b-value; the b-value was very high (b 2) at the beginning, and decreased with time, becoming approximately constant (b 1) after 50 days. Patterns of temporal changes in stress drop and b-value were similar to the patterns for frictional strength and earthquake occurrence rate, suggesting that the change in frictional strength due to migrating fluid not only triggered the swarm activity but also affected earthquake and seismicity characteristics. The estimated high Q-1 value, as well as the hypocenter migration, supports the presence of fluid, and its role in the generation and physical characteristics of the swarm.

  20. Creep and long-term strength of heat-resistant steels with different structures with the account taken of the type of stress deviator

    International Nuclear Information System (INIS)

    Giginyak, F.F.; Dragunov, Yu.G.; Mozharovskaya, T.N.; Titov, V.F.

    1993-01-01

    The results of the experimental investigations into creep and long-term strength of heat-resistant steels 15Kh2MFA and 15Kh2NMFA in the initial state and after heat-treatment simulating the metal irradiation embrittlement at the end of the product service date under static loading at the complex stress state and at high temperatures are presented. The experimentally substantiated equations of state describing creep and long-term stability of materials taking into account the type of the stress state are derived. (author)

  1. Evaluation of the interfacial shear strength and residual stress of TiAlN coating on ZIRLO™ fuel cladding using a modified shear-lag model approach

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y., E-mail: troy.liu@manchester.ac.uk [Materials Performance Centre, School of Materials, The University of Manchester, M13 9PL (United Kingdom); Bhamji, I., E-mail: imran.bhamji@manchester.ac.uk [Materials Performance Centre, School of Materials, The University of Manchester, M13 9PL (United Kingdom); Withers, P.J., E-mail: p.j.withers@manchester.ac.uk [Materials Performance Centre, School of Materials, The University of Manchester, M13 9PL (United Kingdom); Wolfe, D.E., E-mail: dew125@arl.psu.edu [The Pennsylvania State University, University Park, State College, PA 16801 (United States); Motta, A.T., E-mail: atmnuc@engr.psu.edu [The Pennsylvania State University, University Park, State College, PA 16801 (United States); Preuss, M., E-mail: michael.preuss@manchester.ac.uk [Materials Performance Centre, School of Materials, The University of Manchester, M13 9PL (United Kingdom)

    2015-11-15

    This paper investigates the residual stresses and interfacial shear strength of a TiAlN coating on Zr–Nb–Sn–Fe alloy (ZIRLO™) substrate designed to improve corrosion resistance of fuel cladding used in water-cooled nuclear reactors, both during normal and exceptional conditions, e.g. a loss of coolant event (LOCA). The distribution and maximum value of the interfacial shear strength has been estimated using a modified shear-lag model. The parameters critical to this analysis were determined experimentally. From these input parameters the interfacial shear strength between the TiAlN coating and ZIRLO™ substrate was inferred to be around 120 MPa. It is worth noting that the apparent strength of the coating is high (∼3.4 GPa). However, this is predominantly due to the large compressive residuals stress (3 GPa in compression), which must be overcome for the coating to fail in tension, which happens at a load just 150 MPa in excess of this.

  2. Human cold stress of strong local-wind "Hijikawa-arashi" in Japan, based on the UTCI index and thermo-physiological responses

    Science.gov (United States)

    Ohashi, Yukitaka; Katsuta, Takumi; Tani, Haruka; Okabayashi, Taiki; Miyahara, Satoshi; Miyashita, Ryoji

    2018-03-01

    We investigated the cold stress caused by a strong local wind called "Hijikawa-arashi," through in situ vital measurements and the Universal Thermal Climate Index (UTCI). This wind is a very interesting winter phenomenon, localized in an area within 1 km of the seashore in Ozu City, Ehime Prefecture in Japan. When a strong Hijikawa-arashi (HA) occurred at 14-15 m s-1, the UTCI decreased to - 30 °C along the bridge where commuting residents are the most exposed to strong and cold winds. On the bridge, most participants in our experiment felt "very cold" or "extremely cold." The UTCI of HA can be predicted from a multiple regression equation using wind speed and air temperature. The cold HA wind is also harmful to human thermo-physiological responses. It leads to higher blood pressure and increased heart rate, both of which act as cardiovascular stress triggers. Increases of 6-10 mmHg and 3-6 bpm for every 10 °C reduction in UTCI were seen on all observational days, including HA and non-HA days. In fact, the participants' body skin temperatures decreased by approximately 1.2 to 1.7 °C for every 10 °C reduction in UTCI. Thus, the UTCI variation due to the HA outbreak corresponded well with the cold sensation and thermo-physiological responses in humans. This result suggests that daily UTCI monitoring enables the prediction of thermo-physiological responses to the HA cold stress.

  3. Human cold stress of strong local-wind "Hijikawa-arashi" in Japan, based on the UTCI index and thermo-physiological responses.

    Science.gov (United States)

    Ohashi, Yukitaka; Katsuta, Takumi; Tani, Haruka; Okabayashi, Taiki; Miyahara, Satoshi; Miyashita, Ryoji

    2018-03-30

    We investigated the cold stress caused by a strong local wind called "Hijikawa-arashi," through in situ vital measurements and the Universal Thermal Climate Index (UTCI). This wind is a very interesting winter phenomenon, localized in an area within 1 km of the seashore in Ozu City, Ehime Prefecture in Japan. When a strong Hijikawa-arashi (HA) occurred at 14-15 m s -1 , the UTCI decreased to - 30 °C along the bridge where commuting residents are the most exposed to strong and cold winds. On the bridge, most participants in our experiment felt "very cold" or "extremely cold." The UTCI of HA can be predicted from a multiple regression equation using wind speed and air temperature. The cold HA wind is also harmful to human thermo-physiological responses. It leads to higher blood pressure and increased heart rate, both of which act as cardiovascular stress triggers. Increases of 6-10 mmHg and 3-6 bpm for every 10 °C reduction in UTCI were seen on all observational days, including HA and non-HA days. In fact, the participants' body skin temperatures decreased by approximately 1.2 to 1.7 °C for every 10 °C reduction in UTCI. Thus, the UTCI variation due to the HA outbreak corresponded well with the cold sensation and thermo-physiological responses in humans. This result suggests that daily UTCI monitoring enables the prediction of thermo-physiological responses to the HA cold stress.

  4. Experimental Investigation of the Relationship between Breakdown Strength and Tracking Characteristics of Composites

    DEFF Research Database (Denmark)

    Madsen, Søren Find; Holbøll, Joachim; Henriksen, Mogens

    2005-01-01

    ]. The breakdown field strength of specimens cut from similar samples is then determined by a new method capable of estimating the stressed volume [8]. The two values are finally compared and sought incorporated in an analytical formula. All test specimens are supplied by Danish manufacturers of wind turbine...

  5. On the impact of multi-axial stress states on trailing edge bondlines in wind turbine rotor blades

    OpenAIRE

    Castelos, Pablo Noever; Balzani, Claudio

    2016-01-01

    For a reliable design of wind turbine systems all of their components have to be designed to withstand the loads appearing in the turbine's lifetime. When performed in an integral manner this is called systems engineering, and is exceptionally important for components that have an impact on the entire wind turbine system, such as the rotor blade. Bondlines are crucial subcomponents of rotor blades, but they are not much recognized in the wind energy research community. However, a bondline fai...

  6. Effectiveness of various isometric exercises at improving bone strength in cortical regions prone to distal tibial stress fractures.

    Science.gov (United States)

    Florio, C S

    2018-06-01

    A computational model was used to compare the local bone strengthening effectiveness of various isometric exercises that may reduce the likelihood of distal tibial stress fractures. The developed model predicts local endosteal and periosteal cortical accretion and resorption based on relative local and global measures of the tibial stress state and its surface variation. Using a multisegment 3-dimensional leg model, tibia shape adaptations due to 33 combinations of hip, knee, and ankle joint angles and the direction of a single or sequential series of generated isometric resultant forces were predicted. The maximum stress at a common fracture-prone region in each optimized geometry was compared under likely stress fracture-inducing midstance jogging conditions. No direct correlations were found between stress reductions over an initially uniform circular hollow cylindrical geometry under these critical design conditions and the exercise-based sets of active muscles, joint angles, or individual muscle force and local stress magnitudes. Additionally, typically favorable increases in cross-sectional geometric measures did not guarantee stress decreases at these locations. Instead, tibial stress distributions under the exercise conditions best predicted strengthening ability. Exercises producing larger anterior distal stresses created optimized tibia shapes that better resisted the high midstance jogging bending stresses. Bent leg configurations generating anteriorly directed or inferiorly directed resultant forces created favorable adaptations. None of the studied loads produced by a straight leg was significantly advantageous. These predictions and the insight gained can provide preliminary guidance in the screening and development of targeted bone strengthening techniques for those susceptible to distal tibial stress fractures. Copyright © 2018 John Wiley & Sons, Ltd.

  7. Experimental determination of the micro-scale strength and stress-strain relation of an epoxy resin

    DEFF Research Database (Denmark)

    Zike, Sanita; Sørensen, Bent F.; Mikkelsen, Lars Pilgaard

    2016-01-01

    An approach is developed for determining the stress-strain law and a failure stress appropriate for micro-mechanical models of polymer materials. Double cantilever beam test specimens, made of an epoxy polymer with notches having finite root radius, were subjected to pure bending moments in an en......An approach is developed for determining the stress-strain law and a failure stress appropriate for micro-mechanical models of polymer materials. Double cantilever beam test specimens, made of an epoxy polymer with notches having finite root radius, were subjected to pure bending moments......-scale (5–6%). The hardening exponent of a power law hardening material was obtained by the use of the J-integral, estimating the strain energy density around the notch. The hardening exponent was found to be within the range of 5–6 and the corresponding micro-scale failure stress was in the range of 220...

  8. Extreme wind estimate for Hornsea wind farm

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo

    The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...... strength is taken as 0.1. The shear exponents at several heights were calculated from the measurements. The values at 100 m are less than the limit given by IEC standard for all sectors. The 50-year winds have been calculated from various global reanalysis and analysis products as well as mesoscale models...

  9. Effect of Strength and Microstructure on Stress Corrosion Cracking Behavior and Mechanism of X80 Pipeline Steel in High pH Carbonate/Bicarbonate Solution

    Science.gov (United States)

    Zhu, Min; Du, Cuiwei; Li, Xiaogang; Liu, Zhiyong; Wang, Shengrong; Zhao, Tianliang; Jia, Jinghuan

    2014-04-01

    The stress corrosion cracking (SCC) behaviors and mechanisms of X80 pipeline steels with different strength and microstructure in high pH carbonate/bicarbonate solution were investigated by slow strain rate testing and electrochemical test. The results showed that the cracking mode of low strength X80 steel composed of bulky polygonal ferrite and granular bainite in high pH solution was intergranular (IGSCC), and the SCC mechanism was anodic dissolution (AD). While the mixed cracking mode of high strength X80 steel consisted of fine acicular ferrite and granular bainite was intergranular (IGSCC) in the early stage, and transgranular (TGSCC) in the later stage. The decrease of pH value of crack tip was probably the key reason for the occurrence of TGSCC. The SCC mechanism may be a mixed mode of AD and hydrogen embrittlement (HE), and the HE mechanism may play a significant role in the deep crack propagation at the later stage. The cracking modes and SCC mechanisms of the two X80 steels were associated with its microstructure and strength.

  10. Characteristics of structural loess strength and preliminary framework for joint strength formula

    OpenAIRE

    Rong-jian Li; Jun-ding Liu; Rui Yan; Wen Zheng; Sheng-jun Shao

    2014-01-01

    The strength of structural loess consists of the shear strength and tensile strength. In this study, the stress path, the failure envelope of principal stress (Kf line), and the strength failure envelope of structurally intact loess and remolded loess were analyzed through three kinds of tests: the tensile strength test, the uniaxial compressive strength test, and the conventional triaxial shear strength test. Then, in order to describe the tensile strength and shear strength of structural lo...

  11. Ultimate strength, low stress creep characteristics, and thermal intercept methods for an epoxy fiberglass tension member support

    International Nuclear Information System (INIS)

    Niemann, R.C.; Gonczy, J.D.; Hoffman, J.A.; Mataya, K.F.; Smelser, P.; Young, W.C.

    1979-01-01

    A support system utilizing epoxy fiberglass tension members will be used for the UTSI Superconducting Dipole Magnet. Elements of a support system have a basic member which is a link in which a composite is wound around a mandrel. This element uses the strength of the material fibers in a most advantageous way. The flexural and torsional load imputs to the link at its end must be minimized. A spherical bearing with a cylindrical outer surface functions as the central pin. Experience gained in the application with emphasis on tension member material, ultimate strength, creep, and heat intercepts is presented

  12. Thermal expansion, modulus of elasticity, shrinkage, creep and residual strength of concrete for PCRVs at uniaxial stress state and elevated temperatures

    International Nuclear Information System (INIS)

    Aschl, H.; Stoeckl, S.

    1981-01-01

    At the Institut fuer Massivbau of the Technical University of Munich testing machines were built, which allow to test sealed and unsealed cylinders with uniaxial stress state at elevated temperatures till 523 K (250 0 C). With this equipment tests were carried out at predried, unsealed and sealed specimens to study - thermal expansion coefficient - modulus of elasticity - shrinkage and - creep of concrete at elevated temperatures of 353 K (80 0 C) and 393 K (120 0 C) and at a normal temperature of 293 K (20 0 C). In addition the residual strength of all specimens was measured. In the worst case (unsealed, i.e. drying specimens) some showed a maximum decrease in strength up to 60%. (orig.) [de

  13. Anisotropy of the Reynolds stress tensor in the wakes of wind turbine arrays in Cartesian arrangements with counter-rotating rotors

    Science.gov (United States)

    Hamilton, Nicholas; Cal, Raúl Bayoán

    2015-01-01

    A 4 × 3 wind turbine array in a Cartesian arrangement was constructed in a wind tunnel setting with four configurations based on the rotational sense of the rotor blades. The fourth row of devices is considered to be in the fully developed turbine canopy for a Cartesian arrangement. Measurements of the flow field were made with stereo particle-image velocimetry immediately upstream and downstream of the selected model turbines. Rotational sense of the turbine blades is evident in the mean spanwise velocity W and the Reynolds shear stress - v w ¯ . The flux of kinetic energy is shown to be of greater magnitude following turbines in arrays where direction of rotation of the blades varies. Invariants of the normalized Reynolds stress anisotropy tensor (η and ξ) are plotted in the Lumley triangle and indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids representing the balance of components in the normalized anisotropy tensor are composed with the eigenvalues yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates trends in the streamwise coordinate following the rotors, especially trailing the top-tip of the rotor and below the hub. Direction of rotation of rotor blades is shown by the orientation of characteristic spheroids according to principle axes. In the inflows of exit row turbines, the normalized Reynolds stress anisotropy tensor shows cumulative effects of the upstream turbines, tending toward prolate shapes for uniform rotational sense, oblate spheroids for streamwise organization of rotational senses, and a mixture of characteristic shapes when the rotation varies by row. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean

  14. Wind Forcing of the Pacific Ocean Using Scatterometer Wind Data

    Science.gov (United States)

    Kelly, Kathryn A.

    1999-01-01

    The long-term objective of this research was an understanding of the wind-forced ocean circulation, particularly for the Pacific Ocean. To determine the ocean's response to the winds, we first needed to generate accurate maps of wind stress. For the ocean's response to wind stress we examined the sea surface height (SSH) both from altimeters and from numerical models for the Pacific Ocean.

  15. Effects of increasing the allowable compressive stress at release on the shear strength of prestressed concrete girders.

    Science.gov (United States)

    2008-09-01

    In recent years, several research projects have been conducted to study the feasibility of increasing the allowable : compressive stress in concrete at prestress transfer, currently defined as 0.60f'ci in the AASHTO LRFD Bridge : Design Specification...

  16. Modeling Slip System Strength Evolution in Ti 7Al Informed by In situ Grain Stress Measurements (Postprint)

    Science.gov (United States)

    2017-02-17

    incipient damage nucleation and growth , is that which comprises a local neighbor- hood of grains. Heterogeneities in the local intergranular stresses and...After yielding, there was a small drop in the flow stress to 525 MPa followed by work hardening to 535 MPa by the end of the test. Overall, the...collected on a large panel area detector that was located 756 mm downstream of the sample. The detector was a GE amorphous silicon area detector with 2048

  17. Investigation programme and procedure for creep and long-term rupture strength in materials with accounting for stress deviator and loading history

    International Nuclear Information System (INIS)

    Mozharovskaya, T.N.

    1984-01-01

    A programme and procedure are given to study 08Kh18N9 steel at 600 deg C and 15Kh2MFA steel at 550 deg C for creep and long-term strength at different parameters of proportional loading as well as at different parameters under loading in two-link irregular trajectories. This makes it possible to estimate the effect of the kind of a stress deviator, history and prehistory of loading on plastic deformation in creep and on failure under long-term loading

  18. Investigation programme and procedure for creep and long-term rupture strength in materials with accounting for stress deviator and loading history

    Energy Technology Data Exchange (ETDEWEB)

    Mozharovskaya, T N [AN Ukrainskoj SSR, Kiev. Inst. Problem Prochnosti

    1984-11-01

    A programme and procedure are given to study 08Kh18N9 steel at 600 deg C and 15Kh2MFA steel at 550 deg C for creep and long-term strength at different parameters of proportional loading as well as at different parameters under loading in two-link irregular trajectories. This makes it possible to estimate the effect of the kind of a stress deviator, history and prehistory of loading on plastic deformation in creep and on failure under long-term loading.

  19. Effect of temperature and humidity on post-gel shrinkage, cusp deformation, bond strength and shrinkage stress - Construction of a chamber to simulate the oral environment.

    Science.gov (United States)

    Bicalho, Aline Aredes; de Souza, Silas Júnior Boaventura; de Rosatto, Camila Maria Peres; Tantbirojn, Daranee; Versluis, Antheunis; Soares, Carlos José

    2015-12-01

    Evaluate the effect of environment on post-gel shrinkage (Shr), cuspal strains (CS), microtensile bond strength (μTBS), elastic modulus (E) and shrinkage stress in molars with large class II restorations. Sixty human molars received standardized Class II mesio-oclusal-distal cavity preparations. Restorations were made with two composites (CHA, Charisma Diamond, Heraus Kulzer and IPS Empress Direct, Ivoclar-Vivadent) using three environment conditions (22°C/50% humidity, 37°C/50% humidity and 37°C/90% humidity) simulated in custom developed chamber. Shr was measured using the strain gauge technique (n=10). CS was measured using strain gauges. Half of the teeth (n=5) were used to assess the elastic modulus (E) and Knoop hardness (KHN) at different depths using microhardness indentation. The other half (n=5) was used to measure the μTBS. The composites and environment conditions were simulated in a two-dimensional finite element analysis of a tooth restoration. Polymerization shrinkage was modeled using Shr data. The Shr, CS, μTBS, KHN and E data were statistically analyzed using two-way ANOVA and Tukey test (significance level: 0.05). Both composites had similar Shr, CS, μTBS and shrinkage stress. CHA had higher elastic modulus than IPS. Increasing temperature and humidity significantly increased Shr, CS and shrinkage stress. μTBS were similar for groups with lower humidity, irrespective of temperature, and higher with higher humidity. E and KHN were constant through the depth for CHA. E and KHN values were affected by environment only for IPS, mainly deeper in the cavity. Shrinkage stress at dentin/composite interface had high inverse correlation with μTBS. Shrinkage stress in enamel had high correlation with CS. Increasing temperature and humidity caused higher post-gel shrinkage and cusp deformation with higher shrinkage stresses in the tooth structure and tooth/restoration interface for both composites tested. The chamber developed for simulating the

  20. Literature review of models for estimating soil erosion and deposition from wind stresses on uranium-mill-tailings covers

    Energy Technology Data Exchange (ETDEWEB)

    Bander, T.J.

    1982-11-01

    Pacific Northwest Laboratory (PNL) is investigating the use of a rock armoring blanket (riprap) to mitigate wind and water erosion of an earthen radon-suppression cover applied to uranium-mill tailings. The mechanics of wind erosion, as well as of soil deposition, are discussed in this report. Several wind erosion models are reviewed to determine if they can be used to estimate the erosion of soil from a mill-tailings cover. One model, developed by W.S. Chepil, contains the most-important factors that describe variables that influence wind erosion. Particular features of other models are also discussed, as well as the application of Chepil's model to a particular tailings pile. For this particular tailings pile, the estimated erosion was almost one inch per year for an unprotected tailings soil surface. Wide variability in the deposition velocity and lack of adequate deposition models preclude reliable estimates of the rate at which airborne particles are deposited.

  1. Literature review of models for estimating soil erosion and deposition from wind stresses on uranium-mill-tailings covers

    International Nuclear Information System (INIS)

    Bander, T.J.

    1982-11-01

    Pacific Northwest Laboratory (PNL) is investigating the use of a rock armoring blanket (riprap) to mitigate wind and water erosion of an earthen radon-suppression cover applied to uranium-mill tailings. The mechanics of wind erosion, as well as of soil deposition, are discussed in this report. Several wind erosion models are reviewed to determine if they can be used to estimate the erosion of soil from a mill-tailings cover. One model, developed by W.S. Chepil, contains the most-important factors that describe variables that influence wind erosion. Particular features of other models are also discussed, as well as the application of Chepil's model to a particular tailings pile. For this particular tailings pile, the estimated erosion was almost one inch per year for an unprotected tailings soil surface. Wide variability in the deposition velocity and lack of adequate deposition models preclude reliable estimates of the rate at which airborne particles are deposited

  2. Effect of cyclic block loading on character of deformation and strength of structural materials in plane stressed state

    International Nuclear Information System (INIS)

    Kul'chitskij, N.M.; Troshchenko, A.V.; Koval'chuk, B.I.; Khamaza, L.A.; Nikolaev, I.A.

    1982-01-01

    The paper is concerned with choice of conditions for preliminary cyclic block loading, determination of fatigue failure resistance characteristics for various structural materials under regular and selected block loading, investigation of the preliminary cyclic loading effect on regularities of elastoplastic deformation of materials concerned in the biaxial stressed state. Under selected conditions of cyclic block loading the character of damage accumulation is close to the linear law for the materials of high-srength doped steel, and VT6 alloys of concern. These materials in the initial state and after preliminary cyclic loading are anisotropic. Axial direction is characterized by a higher plastic strain resistance for steel and tangential direction - for VT6 alloy. The generalized strain curves for the materials in question are not invariant as to the stressed state type. It is stated that the effect of preliminary unsteady cyclic loading on resistance and general regularities of material deformation in the complex stressed state is insignificant. It is observed that stress-strain properties of the materials tend to vary in the following way: plastic strain resistance of the steel lowers and that of VT6 rises, anisotropy of the materials somehow decreases. The variation in the material anisotropy may be attributed to a decrease in residual stresses resulting from preliminary cyclic loading

  3. Energy-Based Yield Criteria for Orthotropic Materials, Exhibiting Strength-Differential Effect. Specification for Sheets under Plane Stress State

    Directory of Open Access Journals (Sweden)

    Szeptyński P.

    2017-06-01

    Full Text Available A general proposition of an energy-based limit condition for anisotropic materials exhibiting strength-differential effect (SDE based on spectral decomposition of elasticity tensors and the use of scaling pressure-dependent functions is specified for the case of orthotropic materials. A detailed algorithm (based on classical solutions of cubic equations for the determination of elastic eigenstates and eigenvalues of the orthotropic stiffness tensor is presented. A yield condition is formulated for both two-dimensional and three-dimensional cases. Explicit formulas based on simple strength tests are derived for parameters of criterion in the plane case. The application of both criteria for the description of yielding and plastic deformation of metal sheets is discussed in detail. The plane case criterion is verified with experimental results from the literature.

  4. Effect Mo Addition on Corrosion Property and Sulfide Stress Cracking Susceptibility of High Strength Low Alloy Steels

    International Nuclear Information System (INIS)

    Lee, Woo Yong; Koh, Seong Ung; Kim, Kyoo Young

    2005-01-01

    The purpose of this work is to understand the effect of Mo addition on SSC susceptibility of high strength low alloy steels in terms of microstructure and corrosion property. Materials used in this study are high strength low alloy (HSLA) steels with carbon content of 0.04wt% and Mo content varying from 0.1 to 0.3wt%. The corrosion property of steels was evaluated by immersion test in NACE-TM01-77 solution A and by analyzing the growth behavior of surface corrosion products. SSC resistance of steels was evaluated using constant load test. Electrochemical test was performed to investigate initial corrosion rate. Addition of Mo increased corrosion rate of steels by enhancing the porosity of surface corrosion products. however, corrosion rate was not directly related to SSC susceptibility of steels

  5. Solar wind stagnation near comets

    International Nuclear Information System (INIS)

    Galeev, A.A.; Cravens, T.E.; Gombosi, T.I.

    1983-03-01

    The nature of the solar wind flow near comets is examined analytically. In particular, the typical values for the stagnation pressure and magnetic barrier strength are estimated, taking into account the magnetic field line tension and the charge exchange cooling of the mass loaded solar wind. Knowledge of the strength of the magnetic barrier is required in order to determine the location of the contact discontinuity which separates the contaminated solar wind plasma and the outflowing plasma of the cometary ionosphere. (author)

  6. Evaluation of polymerization shrinkage, polymerization shrinkage stress, wear resistance, and compressive strength of a silorane-based composite: A finite element analysis study

    Directory of Open Access Journals (Sweden)

    Suresh Mitthra

    2017-01-01

    Full Text Available Background: Understanding the mechanical properties is important in predicting the clinical behavior of composites. Finite element analysis (FEA evaluates properties of materials replicating clinical scenario. Aim: This study evaluated polymerization shrinkage and stress, wear resistance (WR, and compressive strength (CS of silorane in comparison with two methacrylate resins. Settings and Design: This study design was a numerical study using FEA. Materials and Methods: Three-dimensional (3D models of maxillary premolar with Class I cavities (2 mm depth, 4 mm length, and 2.5 mm width created and restored with silorane, nanohybrid, and microhybrid; Groups I, II, and III, respectively. Loads of 200–600 N were applied. Polymerization shrinkage was first determined by displacement produced in the X, Y, and Z planes. Maximum stress distribution due to shrinkage was calculated using AN SYS software. 3D cube models of composite resins were simulated with varying filler particle size. Similar loads were applied. WR and compressive stress were calculated: K W L/H and load/cross-sectional area, respectively. Statistical analysis done using one-way ANOVA, Kruskal–Wallis, and Tukey's honestly significant difference test (P < 0.05. Results: Polymerization shrinkage (0.99% and shrinkage stress (233.21 Mpa of silorane were less compared to microhybrid (2.14% and 472.43 Mpa and nanohybrid (2.32% and 464.88 Mpa. Silorane (7.92×/1011 μm/mm3 and nanohybrid (7.79×/1011 showed superior WR than microhybrid (1.113×/1017. There was no significant difference in compressive stress among the groups. Conclusion: Silorane exhibited less polymerization shrinkage and shrinkage stress compared to methacrylates. Silorane and nanohybrid showed greater WR compared to microhybrid. CS of all groups was similar.

  7. Stress

    Science.gov (United States)

    ... can be life-saving. But chronic stress can cause both physical and mental harm. There are at least three different types of stress: Routine stress related to the pressures of work, family, and other daily responsibilities Stress brought about ...

  8. Investigation of cause of cracking of high-strength 30HGSNA grade steel subjected to stresses and corrosive agents

    International Nuclear Information System (INIS)

    Sitko, E.

    1995-01-01

    It has been found out that 30HGSNA steel undergo cracking under action of stresses in aqueous solutions containing oxygen, while it show high resistance in deoxidated solutions. The purpose of such phenomena is the existence of sulfur inclusions in steel which are a centers of denting corrosion. That points acting as a stresses concentrators where pH factor decreases including hydrogen formation and its absorption in the metal. That mechanism is the main purpose of brittle steel cracking observed in oxygen rich solutions. (author)

  9. Welding Residual Stress Analysis and Fatigue Strength Assessment at Elevated Temperature for Multi-pass Dissimilar Material Weld Between Alloy 617 and P92 Steel

    Science.gov (United States)

    Lee, Juhwa; Hwang, Jeongho; Bae, Dongho

    2018-03-01

    In this paper, welding residual stress analysis and fatigue strength assessment were performed at elevated temperature for multi-pass dissimilar material weld between Alloy 617 and P92 steel, which are used in thermal power plant. Multi-pass welding between Alloy 617 and P92 steel was performed under optimized welding condition determined from repeated pre-test welding. In particular, for improving dissimilar material weld-ability, the buttering welding technique was applied on the P92 steel side before multi-pass welding. Welding residual stress distribution at the dissimilar material weld joint was numerically analyzed by using the finite element method, and compared with experimental results which were obtained by the hole-drilling method. Additionally, fatigue strength of dissimilar material weld joint was assessed at the room temperature (R.T), 300, 500, and 700 °C. In finite element analysis results, numerical peak values; longitudinal (410 MPa), transverse (345 MPa) were higher than those of experiments; longitudinal (298 MPa), transverse (245 MPa). There are quantitatively big differences between numerical and experimental results, due to some assumption about the thermal conductivity, specific heat, effects of enforced convection of the molten pool, dilution, and volume change during phase transformation caused by actual shield gas. The low fatigue limit at R.T, 300 °C, 500 °C and 700 °C was assessed to be 368, 276, 173 and 137 MPa respectively.

  10. Welding Residual Stress Analysis and Fatigue Strength Assessment at Elevated Temperature for Multi-pass Dissimilar Material Weld Between Alloy 617 and P92 Steel

    Science.gov (United States)

    Lee, Juhwa; Hwang, Jeongho; Bae, Dongho

    2018-07-01

    In this paper, welding residual stress analysis and fatigue strength assessment were performed at elevated temperature for multi-pass dissimilar material weld between Alloy 617 and P92 steel, which are used in thermal power plant. Multi-pass welding between Alloy 617 and P92 steel was performed under optimized welding condition determined from repeated pre-test welding. In particular, for improving dissimilar material weld-ability, the buttering welding technique was applied on the P92 steel side before multi-pass welding. Welding residual stress distribution at the dissimilar material weld joint was numerically analyzed by using the finite element method, and compared with experimental results which were obtained by the hole-drilling method. Additionally, fatigue strength of dissimilar material weld joint was assessed at the room temperature (R.T), 300, 500, and 700 °C. In finite element analysis results, numerical peak values; longitudinal (410 MPa), transverse (345 MPa) were higher than those of experiments; longitudinal (298 MPa), transverse (245 MPa). There are quantitatively big differences between numerical and experimental results, due to some assumption about the thermal conductivity, specific heat, effects of enforced convection of the molten pool, dilution, and volume change during phase transformation caused by actual shield gas. The low fatigue limit at R.T, 300 °C, 500 °C and 700 °C was assessed to be 368, 276, 173 and 137 MPa respectively.

  11. Reliability estimation of a N- M-cold-standby redundancy system in a multicomponent stress-strength model with generalized half-logistic distribution

    Science.gov (United States)

    Liu, Yiming; Shi, Yimin; Bai, Xuchao; Zhan, Pei

    2018-01-01

    In this paper, we study the estimation for the reliability of a multicomponent system, named N- M-cold-standby redundancy system, based on progressive Type-II censoring sample. In the system, there are N subsystems consisting of M statistically independent distributed strength components, and only one of these subsystems works under the impact of stresses at a time and the others remain as standbys. Whenever the working subsystem fails, one from the standbys takes its place. The system fails when the entire subsystems fail. It is supposed that the underlying distributions of random strength and stress both belong to the generalized half-logistic distribution with different shape parameter. The reliability of the system is estimated by using both classical and Bayesian statistical inference. Uniformly minimum variance unbiased estimator and maximum likelihood estimator for the reliability of the system are derived. Under squared error loss function, the exact expression of the Bayes estimator for the reliability of the system is developed by using the Gauss hypergeometric function. The asymptotic confidence interval and corresponding coverage probabilities are derived based on both the Fisher and the observed information matrices. The approximate highest probability density credible interval is constructed by using Monte Carlo method. Monte Carlo simulations are performed to compare the performances of the proposed reliability estimators. A real data set is also analyzed for an illustration of the findings.

  12. Wind energy

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    This chapter discusses the role wind energy may have in the energy future of the US. The topics discussed in the chapter include historical aspects of wind energy use, the wind energy resource, wind energy technology including intermediate-size and small wind turbines and intermittency of wind power, public attitudes toward wind power, and environmental, siting and land use issues

  13. Coastal upwelling by wind-driven forcing in Jervis Bay, New South Wales: A numerical study for 2011

    Science.gov (United States)

    Sun, Youn-Jong; Jalón-Rojas, Isabel; Wang, Xiao Hua; Jiang, Donghui

    2018-06-01

    The Princeton Ocean Model (POM) was used to investigate an upwelling event in Jervis Bay, New South Wales (SE Australia), with varying wind directions and strengths. The POM was adopted with a downscaling approach for the regional ocean model one-way nested to a global ocean model. The upwelling event was detected from the observed wind data and satellite sea surface temperature images. The validated model reproduced the upwelling event showing the input of bottom cold water driven by wind to the bay, its subsequent deflection to the south, and its outcropping to the surface along the west and south coasts. Nevertheless, the behavior of the bottom water that intruded into the bay varied with different wind directions and strengths. Upwelling-favorable wind directions for flushing efficiency within the bay were ranked in the following order: N (0°; northerly) > NNE (30°; northeasterly) > NW (315°; northwesterly) > NE (45°; northeasterly) > ENE (60°; northeasterly). Increasing wind strengths also enhance cold water penetration and water exchange. It was determined that wind-driven downwelling within the bay, which occurred with NNE, NE and ENE winds, played a key role in blocking the intrusion of the cold water upwelled through the bay entrance. A northerly wind stress higher than 0.3 N m-2 was required for the cold water to reach the northern innermost bay.

  14. Fault strength in Marmara region inferred from the geometry of the principle stress axes and fault orientations: A case study for the Prince's Islands fault segment

    Science.gov (United States)

    Pinar, Ali; Coskun, Zeynep; Mert, Aydin; Kalafat, Dogan

    2015-04-01

    The general consensus based on historical earthquake data point out that the last major moment release on the Prince's islands fault was in 1766 which in turn signals an increased seismic risk for Istanbul Metropolitan area considering the fact that most of the 20 mm/yr GPS derived slip rate for the region is accommodated mostly by that fault segment. The orientation of the Prince's islands fault segment overlaps with the NW-SE direction of the maximum principle stress axis derived from the focal mechanism solutions of the large and moderate sized earthquakes occurred in the Marmara region. As such, the NW-SE trending fault segment translates the motion between the two E-W trending branches of the North Anatolian fault zone; one extending from the Gulf of Izmit towards Çınarcık basin and the other extending between offshore Bakırköy and Silivri. The basic relation between the orientation of the maximum and minimum principal stress axes, the shear and normal stresses, and the orientation of a fault provides clue on the strength of a fault, i.e., its frictional coefficient. Here, the angle between the fault normal and maximum compressive stress axis is a key parameter where fault normal and fault parallel maximum compressive stress might be a necessary and sufficient condition for a creeping event. That relation also implies that when the trend of the sigma-1 axis is close to the strike of the fault the shear stress acting on the fault plane approaches zero. On the other hand, the ratio between the shear and normal stresses acting on a fault plane is proportional to the coefficient of frictional coefficient of the fault. Accordingly, the geometry between the Prince's islands fault segment and a maximum principal stress axis matches a weak fault model. In the frame of the presentation we analyze seismological data acquired in Marmara region and interpret the results in conjuction with the above mentioned weak fault model.

  15. Improved Stress Corrosion Cracking Resistance and Strength of a Two-Step Aged Al-Zn-Mg-Cu Alloy Using Taguchi Method

    Science.gov (United States)

    Lin, Lianghua; Liu, Zhiyi; Ying, Puyou; Liu, Meng

    2015-12-01

    Multi-step heat treatment effectively enhances the stress corrosion cracking (SCC) resistance but usually degrades the mechanical properties of Al-Zn-Mg-Cu alloys. With the aim to enhance SCC resistance as well as strength of Al-Zn-Mg-Cu alloys, we have optimized the process parameters during two-step aging of Al-6.1Zn-2.8Mg-1.9Cu alloy by Taguchi's L9 orthogonal array. In this work, analysis of variance (ANOVA) was performed to find out the significant heat treatment parameters. The slow strain rate testing combined with scanning electron microscope and transmission electron microscope was employed to study the SCC behaviors of Al-Zn-Mg-Cu alloy. Results showed that the contour map produced by ANOVA offered a reliable reference for selection of optimum heat treatment parameters. By using this method, a desired combination of mechanical performances and SCC resistance was obtained.

  16. Variations of fracture toughness and stress-strain curve of cold worked stainless steel and their influence on failure strength of cracked pipe

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2016-01-01

    In order to assess failure probability of cracked components, it is important to know the variations of the material properties and their influence on the failure load assessment. In this study, variations of the fracture toughness and stress-strain curve were investigated for cold worked stainless steel. The variations of the 0.2% proof and ultimate strengths obtained using 8 specimens of 20% cold worked stainless steel (CW20) were 77 MPa and 81 MPa, respectively. The respective variations were decreased to 13 and 21 MPa for 40% cold worked material (CW40). Namely, the variation in the tensile strength was decreased by hardening. The COVs (coefficients of variation) of fracture toughness were 7.3% and 16.7% for CW20 and CW40, respectively. Namely, the variation in the fracture toughness was increased by hardening. Then, in order to investigate the influence of the variations in the material properties on failure load of a cracked pipe, flaw assessments were performed for a cracked pipe subjected to a global bending load. Using the obtained material properties led to variation in the failure load. The variation in the failure load of the cracked pipe caused by the variation in the stress-strain curve was less than 1.5% for the COV. The variation in the failure load caused by fracture toughness variation was relatively large for CW40, although it was less than 2.0% for the maximum case. It was concluded that the hardening induced by cold working does not cause significant variation in the failure load of cracked stainless steel pipe. (author)

  17. Generalization of the existing relations between microstructure and yield stress from ferrite-pearlite to high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Iza-Mendia, A., E-mail: aiza@ceit.es [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain); Gutierrez, I. [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain)

    2013-01-20

    A series of available equations allows the yield and the tensile strength of low carbon ferrite-pearlite microstructures to be expressed as a function of the optical grain size, steel composition and interstitials in solution. Over the years, as the complexity of steel microstructures has increased, some additional terms have been added to account for precipitation and forest dislocation contributions. In theory, this opens the door for an extension of these equations to bainitic microstructures. Nevertheless, there is a series of difficulties that needs to be overcome in order to improve prediction accuracy. In the present work, different microstructures (ferrite-pearlite, bainite, quenched, and quenched and tempered) were produced and tension tested in a C-Mn-Nb steel. Optical microscopy and EBSD (Electron Back Scattered Diffraction) were applied and the results were compared as a function of the tolerance angle. Based on this work, an adaptation to Pickering's equation is proposed, including its extension to other microstructures rather than ferrite-pearlite.

  18. In-situ damage localization for a wind turbine blade through outlier analysis of SDDLV-induced stress resultants

    DEFF Research Database (Denmark)

    Ulriksen, Martin Dalgaard; Tcherniak, Dmitri; Hansen, Lasse Majgaard

    2017-01-01

    . In this article, it is examined whether a vibration-based damage localization approach proposed by the authors can provide such reliable monitoring of the location of a structural damage in a wind turbine blade. The blade, which is analyzed in idle condition, is subjected to unmeasured hits from a mounted...... proved to mitigate noise-induced anomalies and systematic, non-damage-associated adverse effects....

  19. Back-propagation neural network-based approximate analysis of true stress-strain behaviors of high-strength metallic material

    International Nuclear Information System (INIS)

    Doh, Jaeh Yeok; Lee, Jong Soo; Lee, Seung Uk

    2016-01-01

    In this study, a Back-propagation neural network (BPN) is employed to conduct an approximation of a true stress-strain curve using the load-displacement experimental data of DP590, a high-strength material used in automobile bodies and chassis. The optimized interconnection weights are obtained with hidden layers and output layers of the BPN through intelligent learning and training of the experimental data; by using these weights, a mathematical model of the material's behavior is suggested through this feed-forward neural network. Generally, the material properties from the tensile test cannot be acquired until the fracture regions, since it is difficult to measure the cross-section area of a specimen after diffusion necking. For this reason, the plastic properties of the true stress-strain are extrapolated using the weighted-average method after diffusion necking. The accuracies of BPN-based meta-models for predicting material properties are validated in terms of the Root mean square error (RMSE). By applying the approximate material properties, the reliable finite element solution can be obtained to realize the different shapes of the finite element models. Furthermore, the sensitivity analysis of the approximate meta-model is performed using the first-order approximate derivatives of the BPN and is compared with the results of the finite difference method. In addition, we predict the tension velocity's effect on the material property through a first-order sensitivity analysis.

  20. Wind: new wind markets

    International Nuclear Information System (INIS)

    Cameron, A.

    2005-01-01

    The June 2005 edition of 'Wind Force 12' suggests that wind could generate 12% of global electricity requirements by 2020. But what moves a potential market into an emerging one? Geographical factors include a good wind resource, plenty of open space and the ability to get the generated electricity to end-users. A country's political framework is equally important, with fixed price systems, renewable quota systems and political will all playing a part. Some potential wind markets around the world are thought to have the conditions necessary to become key players in the wind industry. The emerging markets in countries such as Australia, Brazil, Canada, France, Japan and the Philippines are highlighted as examples

  1. Renewable Energy Essentials: Wind

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-07-01

    Subjects for further research, specific to wind energy technology, include more refined resource assessment; materials with higher strength to mass ratios; advanced grid integration and power quality and control technologies; standardisation and certification; development of low-wind regime turbines; improved forecasting; increased fatigue resistance of major components such as gearboxes; better models for aerodynamics and aeroelasticity; generators based on superconductor technology; deep-offshore foundations; and high-altitude 'kite' concepts.

  2. Decadal Variations of the Western Subarctic Gyre and Main Pycnocline Depth due to Wind Stress Change in the Northern North Pacific

    Science.gov (United States)

    Nagano, A.; Wakita, M.

    2017-12-01

    From the late 1990s to the early 2000s, the western subarctic gyre of the North Pacific, a cyclonic circulation in the western subarctic region, shrank northward associated with a decadal increase of sea surface height (SSH). This gyre change displaced the main pycnocline (halocline) downward and is expected to contribute to the deepening of the overlying temperature minimum layer. This is considered to affect the biogeochemical conditions in the western subarctic region, where is known as substantially slow ocean acidification region. In this study, on the basis of wind stress field data in the subpolar region (40˚N—54˚N, 160˚E—135˚W) during 1979—2014 provided by U.S. National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis, we estimated the variation in SSH, solving the vorticity gradient equation on the beta plane. Decadal increase in SSH at Station K2 (47˚N, 160˚E), representative point of the western subarctic region, was well produced by the calculation, and the correlation coefficient with altimetric SSH exceeds 0.6. The calculated SSH variation consists of the variations due to the barotropic and baroclinic Rossby wave modes. The gyre shrinkage is found to be caused primarily by the barotropic response to the wind change in the whole subpolar region and secondary by the first baroclinic response. Meanwhile, the decadal deepening of the main pycnocline at K2 is attributed to the baroclinic responses of the higher (second, third, and fourth) vertical modes to the local wind change.

  3. The roles of vertical mixing, solar radiation, and wind stress in a model simulation of the sea surface temperature seasonal cycle in the tropical Pacfic Ocean

    Science.gov (United States)

    Chen, Dake; Busalacchi, Antonio J.; Rothstein, Lewis M.

    1994-01-01

    The climatological seasonal cycle of sea surface temperature (SST) in the tropical Pacific is simulated using a newly developed upper ocean model. The roles of vertical mixing, solar radiation, and wind stress are investigated in a hierarchy of numerical experiments with various combinations of vertical mixing algorithms and surface-forcing products. It is found that the large SST annual cycle in the eastern equatorial Pacific is, to a large extent, controlled by the annually varying mixed layer depth which, in turn, is mainly determined by the competing effects of solar radiation and wind forcing. With the application of our hybrid vertical mixing scheme the model-simulated SST annual cycle is much improved in both amplitude and phase as compared to the case of a constant mixed layer depth. Beside the strong effects on vertical mixing, solar radiation is the primary heating term in the surface layer heat budget, and wind forcing influences SST by driving oceanic advective processes that redistribute heat in the upper ocean. For example, the SST seasonal cycle in the western Pacific basically follows the semiannual variation of solar heating, and the cycle in the central equatorial region is significantly affected by the zonal advective heat flux associated with the seasonally reversing South Equatorial Current. It has been shown in our experiments that the amount of heat flux modification needed to eliminate the annual mean SST errors in the model is, on average, no larger than the annual mean uncertainties among the various surface flux products used in this study. Whereas a bias correction is needed to account for remaining uncertainties in the annual mean heat flux, this study demonstrates that with proper treatment of mixed layer physics and realistic forcing functions the seasonal variability of SST is capable of being simulated successfully in response to external forcing without relying on a relaxation or damping formulation for the dominant surface heat

  4. Metric of the 2–6 day sea-surface temperature response to wind stress in the Tropical Pacific and its sensitivity to the K-Profile Parameterization of vertical mixing

    KAUST Repository

    Wagman, Benjamin M.

    2014-05-04

    Uncertainty in wind forcing has long hampered direct tests of ocean model output against observations for the purpose of refining the boundary layer K-Profile Parameterization (KPP) of oceanic vertical mixing. Considered here is a short-term metric that could be sensitive to the ways in which the KPP directly affects the adjustment of sea surface temperatures for a given change in wind stress. In particular a metric is developed based on the lagged correlation between the 2–6 day filtered wind stress and sea surface temperature. The metric is normalized by estimated observational and model uncertainties such that the significance of differences may be assessed. For this purpose multiple wind reanalysis products and their blended combinations were used to represent the range of forcing uncertainty, while perturbed KPP parameter model runs explore the sensitivity of the metric to the parameterization of vertical mixing. The correlation metric is sensitive to perturbations to most KPP parameters, in ways that accord with expectations, although only a few parameters show a sensitivity on the same order as the sensitivity to switching between wind products. This suggests that uncertainties in wind forcing continue to be a significant limitation for applying direct observational tests of KPP physics. Moreover, model correlations are biased high, suggesting that the model lacks or does not resolve sources of variability on the 2–6 day time scale.

  5. Metric of the 2–6 day sea-surface temperature response to wind stress in the Tropical Pacific and its sensitivity to the K-Profile Parameterization of vertical mixing

    KAUST Repository

    Wagman, Benjamin M.; Jackson, Charles S.; Yao, Fengchao; Zedler, Sarah; Hoteit, Ibrahim

    2014-01-01

    Uncertainty in wind forcing has long hampered direct tests of ocean model output against observations for the purpose of refining the boundary layer K-Profile Parameterization (KPP) of oceanic vertical mixing. Considered here is a short-term metric that could be sensitive to the ways in which the KPP directly affects the adjustment of sea surface temperatures for a given change in wind stress. In particular a metric is developed based on the lagged correlation between the 2–6 day filtered wind stress and sea surface temperature. The metric is normalized by estimated observational and model uncertainties such that the significance of differences may be assessed. For this purpose multiple wind reanalysis products and their blended combinations were used to represent the range of forcing uncertainty, while perturbed KPP parameter model runs explore the sensitivity of the metric to the parameterization of vertical mixing. The correlation metric is sensitive to perturbations to most KPP parameters, in ways that accord with expectations, although only a few parameters show a sensitivity on the same order as the sensitivity to switching between wind products. This suggests that uncertainties in wind forcing continue to be a significant limitation for applying direct observational tests of KPP physics. Moreover, model correlations are biased high, suggesting that the model lacks or does not resolve sources of variability on the 2–6 day time scale.

  6. Stress

    Science.gov (United States)

    ... taking care of an aging parent. With mental stress, the body pumps out hormones to no avail. Neither fighting ... with type 1 diabetes. This difference makes sense. Stress blocks the body from releasing insulin in people with type 2 ...

  7. DISTRIBUTED EXTERNAL SURFACE HARDENING OF CAR DESIGN BY WINDING

    Directory of Open Access Journals (Sweden)

    O. V. Fomin

    2017-04-01

    Full Text Available Purpose. The paper involves coverage of features and results of the research conducted by the authors to determine the feasibility and establishment of pre-stressed-strained state of freight cars by winding in order to improve their strength characteristics. It is also necessary to present the theoretical justification for the effectiveness of the application of this method for car designs and an appropriate example for the tank-car. Methodology. The conducted study is based on an analysis of known works on the subject, mathematical justification and computer modeling. At the calculations of rolling stock components contemporary conventional techniques were used. Findings. Authors found that the winding method for pre-stressed-strained state is effective and appropriate for use in the construction of railway rolling stock and, in particular freight cars. Freight car designs with the pre-stressed-strained state are characterized by a number of strength advantages, among which there is an improvement of the work on the perception of operational loads and resource conservation. Originality. For the first time it is proposed the improvement of bearing capacity of freight car constructions through the creation of its component in the directed stress-strained state. It is also for the first time proposed the use of distributed external surface hardening by the method of winding to create a pre-stress-strained state of structural components of freight cars. The methods for winding designs of freight cars and their implementation were considered. Practical value. The studies developed a number of technical solutions for improving the design of freight cars and tank-container, which has been patented. Corresponding solutions for the tank-car are partially presented. Practical implementation of such solutions will significantly improve the technical, economic and operational performances of car designs.

  8. Effects of short fiber reinforcement and mean stress on tensile fatigue strength characteristics of polyethersulfone; Tansen`i kyoka porieterusaruhon no hippari hiro tokusei ni oyobosu heikin oryoku no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Furue, H.; Nonaka, K. [Mechanical Engineering Lab., Tsukuba, Ibaraki (Japan)

    1996-01-15

    Thermoplastics are often reinforced with short fibers with aims of improvement of their strengths, rigidities and hardness or maintenance of their dimensional stabilities. Such short fiber reinforced plastic materials have more expectation for high performance plastics. Authors already examined of some effects of reinforced fiber and of orientation in injection molding on flexural fatigue characteristics of the injection-molded high performance thermoplastic materials. However, the examination of short fiber reinforced effects on fatigue strength characteristics was not always sufficient. In this study, in order to obtain a guiding principle for fatigue resistant design of the short fiber reinforced injection molding materials, polyethersulfones (PES) was examined on its tensile fatigue strength and an effect of short fiber reinforcement for improvement of its fundamental dynamic properties on its fatigue characteristics. Especially, its fatigue life characteristics was elucidated mainly on relationship of mean stress, stress amplitude and number of repeating fracture in tensile fatigue behavior. 10 refs., 15 figs., 2 tabs.

  9. Remarkable weakness against cleavage stress for YBCO-coated conductors and its effect on the YBCO coil performance

    International Nuclear Information System (INIS)

    Yanagisawa, Y.; Nakagome, H.; Takematsu, T.; Takao, T.; Sato, N.; Takahashi, M.; Maeda, H.

    2011-01-01

    Cleavage strength for YBCO-coated conductor is extremely low, typically 0.5 MPa. The remarkable weakness is due to cracks on the slit edge of the conductor. The cleavage stress appears on YBCO double pancake coils impregnated with epoxy. The cleavage stress should be avoided in the coil winding. Cleavage strength for an YBCO-coated conductor at 77 K was investigated with a model experiment. The nominal cleavage strength for an YBCO-coated conductor is extremely low, typically 0.5 MPa. This low nominal cleavage strength is due to stress concentration on a small part of the YBCO-coated conductor in cleavage fracture. Debonding by the cleavage stress occurs at the interface between the buffer layer and the Hastelloy substrate. The nominal cleavage strength for a slit edge of the conductor is 2.5-times lower than that for the original edge of the conductor; cracks and micro-peel existing over the slit edge reduce the cleavage strength for the slit edge. Cleavage stress and peel stress should be avoided in coil winding, as they easily delaminate the YBCO-coated conductor, resulting in substantial degradation of coil performance. These problems are especially important for epoxy impregnated YBCO-coated conductor coils. It appears that effect of cleavage stress and peel stress are mostly negligible for paraffin impregnated YBCO-coated conductor coils or dry wound YBCO-coated conductor coils.

  10. Characterizing the influence of stress-induced microcracks on the laboratory strength and fracture development in brittle rocks using a finite-discrete element method-micro discrete fracture network FDEM-μDFN approach

    Directory of Open Access Journals (Sweden)

    Pooya Hamdi

    2015-12-01

    Full Text Available Heterogeneity is an inherent component of rock and may be present in different forms including mineral heterogeneity, geometrical heterogeneity, weak grain boundaries and micro-defects. Microcracks are usually observed in crystalline rocks in two forms: natural and stress-induced; the amount of stress-induced microcracking increases with depth and in-situ stress. Laboratory results indicate that the physical properties of rocks such as strength, deformability, P-wave velocity and permeability are influenced by increase in microcrack intensity. In this study, the finite-discrete element method (FDEM is used to model microcrack heterogeneity by introducing into a model sample sets of microcracks using the proposed micro discrete fracture network (μDFN approach. The characteristics of the microcracks required to create μDFN models are obtained through image analyses of thin sections of Lac du Bonnet granite adopted from published literature. A suite of two-dimensional laboratory tests including uniaxial, triaxial compression and Brazilian tests is simulated and the results are compared with laboratory data. The FDEM-μDFN models indicate that micro-heterogeneity has a profound influence on both the mechanical behavior and resultant fracture pattern. An increase in the microcrack intensity leads to a reduction in the strength of the sample and changes the character of the rock strength envelope. Spalling and axial splitting dominate the failure mode at low confinement while shear failure is the dominant failure mode at high confinement. Numerical results from simulated compression tests show that microcracking reduces the cohesive component of strength alone, and the frictional strength component remains unaffected. Results from simulated Brazilian tests show that the tensile strength is influenced by the presence of microcracks, with a reduction in tensile strength as microcrack intensity increases. The importance of microcrack heterogeneity in

  11. Wind Energy

    International Nuclear Information System (INIS)

    Rodriguez D, J.M.

    1998-01-01

    The general theory of the wind energy conversion systems is presented. The availability of the wind resource in Colombia and the ranges of the speed of the wind in those which is possible economically to use the wind turbines are described. It is continued with a description of the principal technological characteristics of the wind turbines and are split into wind power and wind-powered pumps; and its use in large quantities grouped in wind farms or in autonomous systems. Finally, its costs and its environmental impact are presented

  12. 49 CFR 192.505 - Strength test requirements for steel pipeline to operate at a hoop stress of 30 percent or more...

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Strength test requirements for steel pipeline to...: MINIMUM FEDERAL SAFETY STANDARDS Test Requirements § 192.505 Strength test requirements for steel pipeline... as provided in paragraph (e) of this section, the strength test must be conducted by maintaining the...

  13. Modelling the water mass circulation in the Aegean Sea. Part I: wind stresses, thermal and haline fluxes

    Directory of Open Access Journals (Sweden)

    I. A. Valioulis

    1994-07-01

    Full Text Available The aim of this work is to develop a computer model capable of simulating the water mass circulation in the Aegean Sea. There is historical, phenomenological and recent experimental evidence of important hydrographical features whose causes have been variably identified as the highly complex bathymetry, the extreme seasonal variations in temperature, the considerable fresh water fluxes, and the large gradients in salinity or temperature across neighbouring water masses (Black Sea and Eastern Mediterranean. In the approach taken here, physical processes are introduced into the model one by one. This method reveals the parameters responsible for permanent and seasonal features of the Aegean Sea circulation. In the first part of the work reported herein, wind-induced circulation appears to be seasonally invariant. This yearly pattern is overcome by the inclusion of baroclinicity in the model in the form of surface thermohaline fluxes. The model shows an intricate pattern of sub-basin gyres and locally strong currents, permanent or seasonal, in accord with the experimental evidence.

  14. Modelling the water mass circulation in the Aegean Sea. Part I: wind stresses, thermal and haline fluxes

    Directory of Open Access Journals (Sweden)

    I. A. Valioulis

    Full Text Available The aim of this work is to develop a computer model capable of simulating the water mass circulation in the Aegean Sea. There is historical, phenomenological and recent experimental evidence of important hydrographical features whose causes have been variably identified as the highly complex bathymetry, the extreme seasonal variations in temperature, the considerable fresh water fluxes, and the large gradients in salinity or temperature across neighbouring water masses (Black Sea and Eastern Mediterranean. In the approach taken here, physical processes are introduced into the model one by one. This method reveals the parameters responsible for permanent and seasonal features of the Aegean Sea circulation. In the first part of the work reported herein, wind-induced circulation appears to be seasonally invariant. This yearly pattern is overcome by the inclusion of baroclinicity in the model in the form of surface thermohaline fluxes. The model shows an intricate pattern of sub-basin gyres and locally strong currents, permanent or seasonal, in accord with the experimental evidence.

  15. Wind speed perception and risk.

    Directory of Open Access Journals (Sweden)

    Duzgun Agdas

    Full Text Available BACKGROUND: How accurately do people perceive extreme wind speeds and how does that perception affect the perceived risk? Prior research on human-wind interaction has focused on comfort levels in urban settings or knock-down thresholds. No systematic experimental research has attempted to assess people's ability to estimate extreme wind speeds and perceptions of their associated risks. METHOD: We exposed 76 people to 10, 20, 30, 40, 50, and 60 mph (4.5, 8.9, 13.4, 17.9, 22.3, and 26.8 m/s winds in randomized orders and asked them to estimate wind speed and the corresponding risk they felt. RESULTS: Multilevel modeling showed that people were accurate at lower wind speeds but overestimated wind speeds at higher levels. Wind speed perceptions mediated the direct relationship between actual wind speeds and perceptions of risk (i.e., the greater the perceived wind speed, the greater the perceived risk. The number of tropical cyclones people had experienced moderated the strength of the actual-perceived wind speed relationship; consequently, mediation was stronger for people who had experienced fewer storms. CONCLUSION: These findings provide a clearer understanding of wind and risk perception, which can aid development of public policy solutions toward communicating the severity and risks associated with natural disasters.

  16. Wind speed perception and risk.

    Science.gov (United States)

    Agdas, Duzgun; Webster, Gregory D; Masters, Forrest J

    2012-01-01

    How accurately do people perceive extreme wind speeds and how does that perception affect the perceived risk? Prior research on human-wind interaction has focused on comfort levels in urban settings or knock-down thresholds. No systematic experimental research has attempted to assess people's ability to estimate extreme wind speeds and perceptions of their associated risks. We exposed 76 people to 10, 20, 30, 40, 50, and 60 mph (4.5, 8.9, 13.4, 17.9, 22.3, and 26.8 m/s) winds in randomized orders and asked them to estimate wind speed and the corresponding risk they felt. Multilevel modeling showed that people were accurate at lower wind speeds but overestimated wind speeds at higher levels. Wind speed perceptions mediated the direct relationship between actual wind speeds and perceptions of risk (i.e., the greater the perceived wind speed, the greater the perceived risk). The number of tropical cyclones people had experienced moderated the strength of the actual-perceived wind speed relationship; consequently, mediation was stronger for people who had experienced fewer storms. These findings provide a clearer understanding of wind and risk perception, which can aid development of public policy solutions toward communicating the severity and risks associated with natural disasters.

  17. Wind Speed Perception and Risk

    Science.gov (United States)

    Agdas, Duzgun; Webster, Gregory D.; Masters, Forrest J.

    2012-01-01

    Background How accurately do people perceive extreme wind speeds and how does that perception affect the perceived risk? Prior research on human–wind interaction has focused on comfort levels in urban settings or knock-down thresholds. No systematic experimental research has attempted to assess people's ability to estimate extreme wind speeds and perceptions of their associated risks. Method We exposed 76 people to 10, 20, 30, 40, 50, and 60 mph (4.5, 8.9, 13.4, 17.9, 22.3, and 26.8 m/s) winds in randomized orders and asked them to estimate wind speed and the corresponding risk they felt. Results Multilevel modeling showed that people were accurate at lower wind speeds but overestimated wind speeds at higher levels. Wind speed perceptions mediated the direct relationship between actual wind speeds and perceptions of risk (i.e., the greater the perceived wind speed, the greater the perceived risk). The number of tropical cyclones people had experienced moderated the strength of the actual–perceived wind speed relationship; consequently, mediation was stronger for people who had experienced fewer storms. Conclusion These findings provide a clearer understanding of wind and risk perception, which can aid development of public policy solutions toward communicating the severity and risks associated with natural disasters. PMID:23226230

  18. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    2015-01-01

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  19. Stress !!!

    OpenAIRE

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten. Opvallend is dat mannelijke studenten uit Twente zich veel minder druk lijken te maken over hun studie. Onder vrouwen ligt de stress juist erg hoog ten opzichte van het landelijk gemiddelde.

  20. Local fatigue behavior in tapered areas of large offshore wind turbine blades

    DEFF Research Database (Denmark)

    Raeis Hosseiny, Seyed Aydin; Jakobsen, Johnny

    2016-01-01

    failure of an entire blade structure. The local strength degradation under an ultimate static loading, subsequent to several years of fatigue, is predicted for an offshore wind turbine blade. Fatigue failure indexes of different damage modes are calculated using a sub-modeling approach. Multi axial...... knock-down factors for ply-drop effects in wind turbine blades under multi-axial static and fatigue loadings can be obtained.......Thickness transitions in load carrying elements lead to improved geometries and efficient material utilization. However, these transitions may introduce localized areas with high stress concentrations and may act as crack initiators that could potentially cause delamination and further catastrophic...

  1. Wind Turbines Adaptation to the Variability of the Wind Field

    Science.gov (United States)

    Ulianov, Yuriy; Martynenko, Gennadii; Misaylov, Vitaliy; Soliannikova, Iuliia

    2010-05-01

    including combined RF-acoustic antenna installed coaxially with the gondola of the wind power turbine. The work of the technique is synchronized with rotation of blades to eliminate their shielding action. Dangerous in terms of dynamic strength is the wind load pulse, the rise time which is comparable with the period of the natural frequency of the wind turbine elements (blade, tower, rotor, etc.). The amplitude decay of resonant vibrations at critical values of the speed of rotation can be realized through the use of mechanical elastic supports with nonlinear artificial dampers. They have a high coefficient of resistance, but may cause self-excited oscillations. We propose the way to deal with raised vibration of wind turbine elements at the expense of short-term increase of damping in the range of critical rotary axis speeds or during impulsive effects of wind loadings (wind gusts). This is possible through the use of non-linear electromagnetic dampers or active magnetic bearings. Their feature is the possibility of varying the mechanical stiffness and damping properties by changing the electrical parameters of electromagnets. The controlling of these parameters is carried out by the control system (CS) with the information feedback on the spatial-temporal structure of the wind field obtained from IRASS. In the composition of the CS can also be included the rotational speed sensor of the WPT rotor. This approach to the adaptation of wind turbines will allow to reduce vibration and to perform early compensation of the load on their components, which arise under the wind gusts. In addition, corrections about the wind field obtained with IRASS, would increase the mean power of WPT.

  2. Stress !!!

    NARCIS (Netherlands)

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten.

  3. Wind Shear Identification with the Retrieval Wind of Doppler Wearth Radar

    Science.gov (United States)

    Zhou, S.; Cui, Y.; Zheng, H.; Zhang, T.

    2018-05-01

    A new method, which based on the wind field retrieval algorithm of Volume Velocity Process (VVP), has been used to identified the intensity of wind shear occurred in a severe convection process in Guangzhou. The intensity of wind shear's strength shown that new cells would be more likely to generate in areas where the magnitude generally larger than 3.0 m/(s*km). Moreover, in the areas of potential areas of rainfall, the wind shear's strength would larger than 4.5 m/(s*km). This wind shear identify method is very helpful to forecasting severe convections' moving and developments.

  4. Wind energy

    International Nuclear Information System (INIS)

    Kotevski, Darko

    2003-01-01

    Wind is not only free, it is inexhaustible. Wind energy has come a very long way since the prototypes of just 20 years ago. today's wind turbines are state-of-the-art technology - modular and quick to install anywhere where there is sufficient wind potential to provide secure, centralised or distributed generation. It is a global phenomenon, the world's fastest growing energy sector, a clean and effective modern technology that completely avoids pollution and thus reducing the 'green house' effect. (Original)

  5. Wind Structure and Wind Loading

    DEFF Research Database (Denmark)

    Brorsen, Michael

    The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...

  6. Wind power

    International Nuclear Information System (INIS)

    Gipe, P.

    2007-01-01

    This book is a translation of the edition published in the USA under the title of ''wind power: renewable energy for home, farm and business''. In the wake of mass blackouts and energy crises, wind power remains a largely untapped resource of renewable energy. It is a booming worldwide industry whose technology, under the collective wing of aficionados like author Paul Gipe, is coming of age. Wind Power guides us through the emergent, sometimes daunting discourse on wind technology, giving frank explanations of how to use wind technology wisely and sound advice on how to avoid common mistakes. Since the mid-1970's, Paul Gipe has played a part in nearly every aspect of wind energy development from installing small turbines to promoting wind energy worldwide. As an American proponent of renewable energy, Gipe has earned the acclaim and respect of European energy specialists for years, but his arguments have often fallen on deaf ears at home. Today, the topic of wind power is cropping up everywhere from the beaches of Cape Cod to the Oregon-Washington border, and one wind turbine is capable of producing enough electricity per year to run 200 average American households. Now, Paul Gipe is back to shed light on this increasingly important energy source with a revised edition of Wind Power. Over the course of his career, Paul Gipe has been a proponent, participant, observer, and critic of the wind industry. His experience with wind has given rise to two previous books on the subject, Wind Energy Basics and Wind Power for Home and Business, which have sold over 50,000 copies. Wind Power for Home and Business has become a staple for both homeowners and professionals interested in the subject, and now, with energy prices soaring, interest in wind power is hitting an all-time high. With chapters on output and economics, Wind Power discloses how much you can expect from each method of wind technology, both in terms of energy and financial savings. The book updated models

  7. Influencia de la fuerza muscular isométrica de las extremidades superiores en el estrés oxidativo en niños. (Influence of handgrip strength in oxidative stress in children.

    Directory of Open Access Journals (Sweden)

    Manuel Guillén-del Castillo

    2011-01-01

    Full Text Available ResumenEl ejercicio físico puede producir estrés oxidativo en el individuo lo que pueden condicionar el riesgo cardiovascular en niños y adolescentes. Este estudio pretende analizar el estrés oxidativo según la fuerza muscular isométrica de las extremidades superiores en la edad pediátrica. Se estudiaron 70 niños sanos con edades entre 10 y 14 años, y se analizaron en saliva los lipoperóxidos (LPO, el glutatión reducido (GSH, la ratio GSH/LPO y la catalasa, como marcadores de estrés oxidativo. La muestra se dividió en dos grupos según una condición física superior o inferior medida a través de dinamometría manual (TKK 5110; se diferenció la serie en sujetos prepuberales y puberales. Se encontraron niveles significativamente inferiores de GSH y GSH/LPO en el grupo de niños con fuerza superior, y en los puberales con la mismas características; estos resultados podrían indicar la existencia de un mayor estrés oxidativo en esta situación. En conclusión, los mayores niveles de fuerza músculo esquelética, medida a través de dinamometría manual, posiblemente pueden estar asociados a un mayor estrés oxidativo en niños púberes con condición física musculoesquelética superior.AbstractPhysical exercise can produce oxidative stress, this situation could contribute cardiovascular risk in children and adolescents. The following study tries to evaluate the oxidative stress produced according to the handgrip strength in infancy. 70 healthy male subjects, ages 10 to 14 years, were studied. In the saliva samples, lipoperoxides (LPO, reduced glutathione (GSH, glutathione/lipoperoxides ratio and catalase were analyzed as biomarkers of oxidative stress. Children were divided into two groups according to their handgrip strength (high or low measured by handgrip strength (TKK 5110. The groups were also divided into prepubertal and pubertal subjects. We found GSH’s significantly low levels and of GSH/LPO in pubertal group with high

  8. Stress.

    Science.gov (United States)

    Chambers, David W

    2008-01-01

    We all experience stress as a regular, and sometimes damaging and sometimes useful, part of our daily lives. In our normal ups and downs, we have our share of exhaustion, despondency, and outrage--matched with their corresponding positive moods. But burnout and workaholism are different. They are chronic, dysfunctional, self-reinforcing, life-shortening habits. Dentists, nurses, teachers, ministers, social workers, and entertainers are especially susceptible to burnout; not because they are hard-working professionals (they tend to be), but because they are caring perfectionists who share control for the success of what they do with others and perform under the scrutiny of their colleagues (they tend to). Workaholics are also trapped in self-sealing cycles, but the elements are ever-receding visions of control and using constant activity as a barrier against facing reality. This essay explores the symptoms, mechanisms, causes, and successful coping strategies for burnout and workaholism. It also takes a look at the general stress response on the physiological level and at some of the damage American society inflicts on itself.

  9. Gearless wind power generator

    Energy Technology Data Exchange (ETDEWEB)

    Soederlund, L.; Ridanpaeae, P.; Vihriaelae, H.; Peraelae, R. [Tampere Univ. of Technology (Finland). Lab. of Electricity and Magnetism

    1998-12-31

    During the wind power generator project a design algorithm for a gearless permanent magnet generator with an axially orientated magnetic flux was developed and a 10 kW model machine was constructed. Utilising the test results a variable wind speed system of 100 kW was designed that incorporates a permanent magnet generator, a frequency converter and a fuzzy controller. This system produces about 5-15% more energy than existing types and stresses to the blades are minimised. The type of generator designed in the project represents in general a gearless solution for slow-speed electrical drives. (orig.)

  10. Current state of low-cycle fatigue research based on multiaxial stress intensity and its challenges. Part 1. Focusing on low-cycle fatigue strength evaluation method of elbow piping subjected to in-plane cyclic bending displacement load

    International Nuclear Information System (INIS)

    Urabe, Yoshio

    2017-01-01

    The R and D of fatigue strength at multiaxial stress intensity is recognized to become extremely important in the future in terms of the elaboration of low-cycle fatigue evaluation of various structures including piping systems and reflection on those standards. This paper focuses on the evaluation method developed by the author, namely cumulative damage rule in consideration of multiaxial stress intensity, and explains the concept and the results of verification and evaluation. It also discusses the engineering problems of the current low cycle fatigue assessment technology that were clarified in the process of developing low-cycle fatigue assessment method based on multiaxial stress intensity. The conservative lifespan and somewhat more conservative actual lifetime of elbow piping can be estimated by the conventional 'revised universal slope method' and 'advanced revised universal slope method.' However, these are empirical rules, and the theoretical basis is not clear. From 'cumulative damage rule in consideration of multiaxial stress intensity,' the author calculated furthermore 'low cycle fatigue evaluation formula based on cumulative damage rule in consideration of multi-axial stress intensity,' and examined it. As a result, an evaluation formula that can reasonably assume the equivalent thermoplastic strain range could be obtained at half of the repeat count as targeted. Furthermore, at the stage where future high precision FEM analysis can be used, direct low-cycle fatigue life curve can be established. (A.O.)

  11. Astrospheres and Solar-like Stellar Winds

    Directory of Open Access Journals (Sweden)

    Wood Brian E.

    2004-07-01

    Full Text Available Stellar analogs for the solar wind have proven to be frustratingly difficult to detect directly. However, these stellar winds can be studied indirectly by observing the interaction regions carved out by the collisions between these winds and the interstellar medium (ISM. These interaction regions are called "astrospheres", analogous to the "heliosphere" surrounding the Sun. The heliosphere and astrospheres contain a population of hydrogen heated by charge exchange processes that can produce enough H I Ly alpha absorption to be detectable in UV spectra of nearby stars from the Hubble Space Telescope (HST. The amount of astrospheric absorption is a diagnostic for the strength of the stellar wind, so these observations have provided the first measurements of solar-like stellar winds. Results from these stellar wind studies and their implications for our understanding of the solar wind are reviewed here. Of particular interest are results concerning the past history of the solar wind and its impact on planetary atmospheres.

  12. Contact stresses modeling at the Panda-type fiber single-layer winding and evaluation of their impact on the fiber optic properties

    Science.gov (United States)

    Lesnikova, Yu I.; Smetannikov, O. Yu; Trufanov, A. N.; Trufanov, N. A.

    2017-02-01

    The impact of contact transverse forces on the birefringence of the single-mode polarization-maintaining Panda-type fiber is numerically modeled. It has been established that with a single-row power winding on a cylindrical mandrel, the fiber tension at winding is the principal factor that influences birefringence. When coiling the fiber based on the local defect microbending, the birefringence at the microbending point differs from that of the free fiber by 1.3%.

  13. Effect of reactor irradiation on long-term strength and creep of 0Kh16N15M3B steel under plane stressed state

    International Nuclear Information System (INIS)

    Khristov, G.P.; Kosov, B.D.

    1982-01-01

    The paper deals with analysis of results of experimental studies in creep of the austenitic OKh16n15m3b steel with various size of initial-structure grain under conditions of high-intensity reactor irradiation and control tests. It is suggested to consider the material initial structure effect on intensity of minimum creep rates both under ordinary and intrareactor conditions of loading by means of the function grain size effect on the equivalent stress. It is shown that the criterial expression previously suggested by the authors is invariant to the type of stressed and structural states and relative to intensity of minimal creep rates. It is established that the creep rate of the irradiated steel may be calculated from dependence for nonirradiated steel using as an argument a certain reduced equivalent stress which is a function of the acting stress and irradiation parameter

  14. Spectrum Fatigue Lifetime and Residual Strength for Fiberglass Laminates; TOPICAL

    International Nuclear Information System (INIS)

    WAHL, NEIL K.; MANDELL, JOHN F.; SAMBORSKY, DANIEL D.

    2002-01-01

    This report addresses the effects of spectrum loading on lifetime and residual strength of a typical fiberglass laminate configuration used in wind turbine blade construction. Over 1100 tests have been run on laboratory specimens under a variety of load sequences. Repeated block loading at two or more load levels, either tensile-tensile, compressive-compressive, or reversing, as well as more random standard spectra have been studied. Data have been obtained for residual strength at various stages of the lifetime. Several lifetime prediction theories have been applied to the results. The repeated block loading data show lifetimes that are usually shorter than predicted by the most widely used linear damage accumulation theory, Miner's sum. Actual lifetimes are in the range of 10 to 20 percent of predicted lifetime in many cases. Linear and nonlinear residual strength models tend to fit the data better than Miner's sum, with the nonlinear providing a better fit of the two. Direct tests of residual strength at various fractions of the lifetime are consistent with the residual strength models. Load sequencing effects are found to be insignificant. The more a spectrum deviates from constant amplitude, the more sensitive predictions are to the damage law used. The nonlinear model provided improved correlation with test data for a modified standard wind turbine spectrum. When a single, relatively high load cycle was removed, all models provided similar, though somewhat non-conservative correlation with the experimental results. Predictions for the full spectrum, including tensile and compressive loads were slightly non-conservative relative to the experimental data, and accurately captured the trend with varying maximum load. The nonlinear residual strength based prediction with a power law S-N curve extrapolation provided the best fit to the data in most cases. The selection of the constant amplitude fatigue regression model becomes important at the lower stress, higher

  15. Wind energy.

    Science.gov (United States)

    Leithead, W E

    2007-04-15

    From its rebirth in the early 1980s, the rate of development of wind energy has been dramatic. Today, other than hydropower, it is the most important of the renewable sources of power. The UK Government and the EU Commission have adopted targets for renewable energy generation of 10 and 12% of consumption, respectively. Much of this, by necessity, must be met by wind energy. The US Department of Energy has set a goal of 6% of electricity supply from wind energy by 2020. For this potential to be fully realized, several aspects, related to public acceptance, and technical issues, related to the expected increase in penetration on the electricity network and the current drive towards larger wind turbines, need to be resolved. Nevertheless, these challenges will be met and wind energy will, very likely, become increasingly important over the next two decades. An overview of the technology is presented.

  16. A calculation method of cracking moment for the high strength ...

    Indian Academy of Sciences (India)

    mal stress and crack width for the tensional behaviour of concrete and has been proposed by ... stresses. To calculate concrete stress in a cross section of high strength concrete beams, failure strain is ..... American Concrete. Institute, Detroit.

  17. Fatigue properties for the fracture strength of columnar accessory minerals embedded within metamorphic tectonites: implications for stress magnitude in continental crust at the depth of the brittle-plastic transition zone

    Science.gov (United States)

    Kimura, N.; Iwashita, N.; Masuda, T.

    2009-04-01

    1. Introduction Previous studies have compiled yield-strength profiles of continental lithosphere based on the results of laboratory measurements and numerical calculations; however, yield-strength values remain poorly constrained, especially at depths below the brittle-plastic transition zone. Recent studies by the authors have refined the microboudin technique for estimating palaeostress magnitude in the deep crust (> 10 km depth). This technique has the potential to provide important information on stress levels in the deep continental crust, an environment to which available in situ stress measurements and palaeopiezometric methods cannot be applied. In applying the microboudinage technique, obtaining an estimate of the palaeostress magnitude requires knowledge of the fracture strength of columnar accessory minerals (e.g., tourmaline, amphibole, and epidote) that are subjected to brittle fracturing during plastic deformation of the surrounding matrix minerals. The absolute magnitude of fracture strength is known to show a marked reduction in the case of fatigue fracture. Fatigue fracture falls into two categories: static fatigue and cyclic fatigue. In the field of experimental rock deformation, stress corrosion by water molecules (static fatigue) is commonly invoked as the mechanism of fatigue fracture; however, evidence of both static and cyclic fatigue has been reported from studies of natural geological samples. The present study focused on the fatigue properties of columnar accessory minerals at high temperatures, with the aim of improving the accuracy of estimates of natural palaeostress magnitude at depth in the crust. 2. Constant stress-rate test A constant stress-rate test was performed to determine the influence of static fatigue on the strength of columnar accessory minerals. The test was conducted under three-point bending with a span distance of 10 mm. Temperature conditions and the crosshead speed were set in the ranges of ambient to 600°C, and 0

  18. Grid Integration of Offshore Wind | Wind | NREL

    Science.gov (United States)

    Grid Integration of Offshore Wind Grid Integration of Offshore Wind Much can be learned from the existing land-based integration research for handling the variability and uncertainty of the wind resource Arklow Bank offshore wind park consists of seven GE Wind 3.6-MW wind turbines. Integration and

  19. Wind Energy

    Energy Technology Data Exchange (ETDEWEB)

    Beurskens, H.J.M. [SET Analysis, Kievitlaan 26, 1742 AD Schagen (Netherlands); Brand, A.J. [Energy research Centre of the Netherlands ECN, Unit Wind Energy, P.O. Box 1, 1755 ZG Petten (Netherlands)

    2013-02-15

    Over the years, wind energy has become a major source of renewable energy worldwide. The present chapter addresses the wind resource, which is available for exploitation for large-scale electricity production, and its specific physical properties. Furthermore, the technical options available to convert the energy of the air flow into mechanical energy and electricity are described. Specific problems of large-scale integration of wind energy into the grid as well as the present and future market developments are described in this chapter. Finally, environmental aspects are discussed briefly.

  20. Attitude Strength.

    Science.gov (United States)

    Howe, Lauren C; Krosnick, Jon A

    2017-01-03

    Attitude strength has been the focus of a huge volume of research in psychology and related sciences for decades. The insights offered by this literature have tremendous value for understanding attitude functioning and structure and for the effective application of the attitude concept in applied settings. This is the first Annual Review of Psychology article on the topic, and it offers a review of theory and evidence regarding one of the most researched strength-related attitude features: attitude importance. Personal importance is attached to an attitude when the attitude is perceived to be relevant to self-interest, social identification with reference groups or reference individuals, and values. Attaching personal importance to an attitude causes crystallizing of attitudes (via enhanced resistance to change), effortful gathering and processing of relevant information, accumulation of a large store of well-organized relevant information in long-term memory, enhanced attitude extremity and accessibility, enhanced attitude impact on the regulation of interpersonal attraction, energizing of emotional reactions, and enhanced impact of attitudes on behavioral intentions and action. Thus, important attitudes are real and consequential psychological forces, and their study offers opportunities for addressing behavioral change.

  1. Computation of radionuclide particulate finite area fugitive source strengths

    Energy Technology Data Exchange (ETDEWEB)

    Fields, D E

    1983-06-01

    Atmospheric source strengths quantifying particulate re-suspension from wind and non-wind disturbance-driven processes are computed for sites of small area. These values are useful in computing downwind air concentration values to evaluate risk to exposed populations. The net source strength for the site is the sum of the wind- and disturbance-driven components. A unified source strength approach includes both classes of re-suspension processes. More research is needed to satisfactorily express the time-dependence of re-suspension parameters, especially in non-arid climates where population densities are greater. (JMT)

  2. Wind energy market study Eastern Europe. Poland

    International Nuclear Information System (INIS)

    Skjerk Christensen, P.

    1994-04-01

    The main objective of the THERMIE Associated Measure WE05 is to study market conditions and estimate the market for wind power in Eastern Europe. This report describes the results of a study of the conditions in Poland, which has been concentrated on the following areas: wind energy potential in Poland; data concerning the present structure of the power production system including costs; payback prices, subsidies, etc. with relation to renewable energy sources, especially wind power; information on existing wine turbines and their production in Poland; possibilities for co-production of wind turbines by Polish and EC factories, and rules and legislation pertaining to the establishment of wind turbines and to power production by wind, eg regulations related to grid connection, safety and environment. According to existing data there are possibilities for using the wind potential in certain parts of poland. The wind data have to be improved if particular sites are considered for wind parks. The current official plans concerning the energy system have taken renewable sources into consideration, including wind power that is estimated to contribute ∼ 1 GWh by 2005-2010. Wind turbines may be connected to the public grid with due regard to the strength of the line. Presently, the owner has to pay all the costs, however, new rules are under consideration. The conditions for the connection and operation of wind turbines have to be discussed with the particular utility on an an-hoc basis. (EG)

  3. World Wind

    Data.gov (United States)

    National Aeronautics and Space Administration — World Wind allows any user to zoom from satellite altitude into any place on Earth, leveraging high resolution LandSat imagery and SRTM elevation data to experience...

  4. Wind power

    International Nuclear Information System (INIS)

    2009-01-01

    At the end of 2008,the European wind power capacity had risen to 65,247 MW which is a 15,1% increase on 2007. The financial crisis does not appear to have any real consequences of the wind power sector's activity in 2008. At the end of 2008 the European Union accommodated 53,9% of the world's wind power capacity. The top ten countries in terms of installed wind capacities are: 1) Usa with 25,388 MW, 2) Germany with 23,903 MW, 3) Spain with 16,740 MW, 4) China with 12,200 MW, 5) India with 9,645 MW, 6) Italy with 3,736 MW, 7) France with 3,542 MW, 8) U.K. with 3,406 MW, 9) Denmark with 3,166 MW and 10) Portugal with 2,862 MW. (A.C.)

  5. Wind power

    Energy Technology Data Exchange (ETDEWEB)

    1979-01-01

    This publication describes some of the technical, economic, safety and institutional considerations involved in the selection, installation and evaluation of a wind generation system. This information is presented, where possible, in practical, non-technical terms. The first four sections provide background information, theory, and general knowledge, while the remaining six sections are of a more specific nature to assist the prospective owner of a wind generator in his calculations and selections. Meteorological information is provided relating to the wind regime in Nova Scotia. The section on cost analysis discusses some of the factors and considerations which must be examined in order to provide a logical comparison between the alternatives of electricity produced from other sources. The final two sections are brief summaries of the regulations and hazards pertaining to the use of wind generators. The cost of wind-generated electricity is high compared to present Nova Scotia Power Corporation rates, even on Sable Island, Nova Scotia's highest wind area. However, it may be observed that Sable Island is one of the areas of Nova Scotia which is not presently supplied through the power grid and, particularly if there was a significant increase in the price of diesel oil, wind-generated electricity may well be the most economical alternative in that area. Generally speaking, however, where a consumer can purchase electricity at the normal domestic rate, wind generators are not economical, and they will not become economical unless there is a great reduction in their cost, an great increase in electricity rates, or both. Includes glossary. 23 figs., 11 tabs.

  6. Noise immission from wind turbines

    International Nuclear Information System (INIS)

    1999-01-01

    The project has dealt with practical ways to reduce the influence of background noise caused by wind acting on the measuring microphones. The uncertainty of measured noise emission (source strength) has been investigated. The main activity was a Round Robin Test involving measurements by five laboratories at the same wind turbine. Each laboratory brought its own instrumentation and performed the measurements and analyses according to their interpretation. The tonality of wind turbine noise is an essential component of the noise impact on the environment. In the present project the uncertainty in the newest existing methods for assessing tonality was investigated. The project included noise propagation measurements in different weather conditions around wind turbines situated in different types of terrain. The results were used to validate a noise propagation model developed in the project. Finally, the project also included a study with listeners evaluating recordings of wind turbine noise. The results are intended as guidance for wind turbine manufacturers in identifying the aspects of wind turbine noise most important to annoyance. (author)

  7. Influence of orographically steered winds on Mutsu Bay surface currents

    Science.gov (United States)

    Yamaguchi, Satoshi; Kawamura, Hiroshi

    2005-09-01

    Effects of spatially dependent sea surface wind field on currents in Mutsu Bay, which is located at the northern end of Japanese Honshu Island, are investigated using winds derived from synthetic aperture radar (SAR) images and a numerical model. A characteristic wind pattern over the bay was evidenced from analysis of 118 SAR images and coincided with in situ observations. Wind is topographically steered with easterly winds entering the bay through the terrestrial gap and stronger wind blowing over the central water toward its mouth. Nearshore winds are weaker due to terrestrial blockages. Using the Princeton Ocean Model, we investigated currents forced by the observed spatially dependent wind field. The predicted current pattern agrees well with available observations. For a uniform wind field of equal magnitude and average direction, the circulation pattern departs from observations demonstrating that vorticity input due to spatially dependent wind stress is essential in generation of the wind-driven current in Mutsu Bay.

  8. Turbulent wind at the equatorial segment of an operating Darrieus wind turbine blade

    Science.gov (United States)

    Connell, J. R.; Morris, V. R.

    1989-09-01

    Six turbulent wind time series, measured at equally spaced equator-height locations on a circle 3 m outside a 34-m Darrieus rotor, are analyzed to approximate the wind fluctuations experienced by the rotor. The flatwise lower root-bending stress of one blade was concurrently recorded. The wind data are analyzed in three ways: wind components that are radial and tangential to the rotation of a blade were rotationally sampled; induction and wake effects of the rotor were estimated from the six Eulerian time series; and turbulence spectra of both the measured wind and the modeled wind from the PNL theory of rotationally sampled turbulence. The wind and the rotor response are related by computing the spectral response function of the flatwise lower root-bending stress. Two bands of resonant response that surround the first and second flatwise modal frequencies shift with the rotor rotation rate.

  9. Thermal loading of wind power converter considering dynamics of wind speed

    DEFF Research Database (Denmark)

    Baygildina, Elvira; Peltoniemi, Pasi; Pyrhönen, Olli

    2013-01-01

    The thermal loading of power semiconductors is a crucial performance related to the reliability and cost of the wind power converter. However, the thermal loading impacts by the variation of wind speeds have not yet been clarified, especially when considering the aerodynamic behavior of the wind...... turbines. In this paper, the junction temperatures in the wind power converter are studied under not only steady state, but also turbulent wind speed conditions. The study is based on a 1.5 MW direct-driven turbine system with aerodynamic model described by Unsteady Blade Element Momentum Method (BEMM......), and the thermal stress of power devices is investigated from the frequency spectrum point of view of wind speed. It is concluded that because of the strong inertia effects by the aerodynamic behavior of wind turbines, thermal stress of the semiconductors is relatively more stable and only influenced by the low...

  10. Strength evaluation code STEP for brittle materials

    International Nuclear Information System (INIS)

    Ishihara, Masahiro; Futakawa, Masatoshi.

    1997-12-01

    In a structural design using brittle materials such as graphite and/or ceramics it is necessary to evaluate the strength of component under complex stress condition. The strength of ceramic materials is said to be influenced by the stress distribution. However, in the structural design criteria simplified stress limits had been adopted without taking account of the strength change with the stress distribution. It is, therefore, important to evaluate the strength of component on the basis of the fracture model for brittle material. Consequently, the strength evaluation program, STEP, on a brittle fracture of ceramic materials based on the competing risk theory had been developed. Two different brittle fracture modes, a surface layer fracture mode dominated by surface flaws and an internal fracture mode by internal flaws, are treated in the STEP code in order to evaluate the strength of brittle fracture. The STEP code uses stress calculation results including complex shape of structures analyzed by the generalized FEM stress analysis code, ABAQUS, so as to be possible to evaluate the strength of brittle fracture for the structures having complicate shapes. This code is, therefore, useful to evaluate the structural integrity of arbitrary shapes of components such as core graphite components in the HTTR, heat exchanger components made of ceramics materials etc. This paper describes the basic equations applying to the STEP code, code system with a combination of the STEP and the ABAQUS codes and the result of the verification analysis. (author)

  11. Wind forces and related saltation transport

    NARCIS (Netherlands)

    Leenders, J.K.; van Boxel, J.H.; Sterk, G.

    2005-01-01

    The effect of several wind characteristics on sand transport was studied in three experiments in north Burkina Faso, West Africa. The first experiment is used to analyse the relation between wind speed and shear stress fluctuations across height. The second experiment is used to study the relation

  12. Wind effect in turbulence parametrization

    Science.gov (United States)

    Colombini, M.; Stocchino, A.

    2005-09-01

    The action of wind blowing over a closed basin ultimately results in a steady shear-induced circulation pattern and in a leeward rising of the free surface—and a corresponding windward lowering—known as wind set-up. If the horizontal dimensions of the basin are large with respect to the average flow depth, the occurrence of local quasi-equilibrium conditions can be expected, i.e. the flow can be assumed to be locally driven only by the wind stress and by the opposing free surface gradient due to set-up. This wind-induced flow configuration shows a strong similarity with turbulent Couette-Poiseuille flow, the one dimensional flow between parallel plates generated by the simultaneous action of a constant pressure gradient and of the shear induced by the relative motion of the plates. A two-equation turbulence closure is then employed to perform a numerical study of turbulent Couette-Poiseuille flows for different values of the ratio of the shear stresses at the two walls. The resulting eddy viscosity vertical distributions are analyzed in order to devise analytical profiles of eddy viscosity that account for the effect of wind. The results of this study, beside allowing for a physical insight on the turbulence process of this class of flows, will allow for a more accurate description of the wind effect to be included in the formulation of quasi-3D and 3D models of lagoon hydrodynamics.

  13. No Differences Between Alter G-Trainer and Active and Passive Recovery Strategies on Isokinetic Strength, Systemic Oxidative Stress and Perceived Muscle Soreness After Exercise-Induced Muscle Damage.

    Science.gov (United States)

    Cooke, Matthew B; Nix, Carrie M; Greenwood, Lori D; Greenwood, Mike C

    2018-03-01

    Cooke, MB, Nix, C, Greenwood, L, and Greenwood, M. No Differences Between Alter G-Trainer and Active and Passive Recovery Strategies on Isokinetic Strength, Systemic Oxidative Stress and Perceived Muscle Soreness After Exercise-Induced Muscle Damage. J Strength Cond Res 32(3): 736-747, 2018-The incidence of muscle injuries is prevalent in elite sport athletes and weekend warriors and strategies that safely and effectively hasten recovery are highly desirable. The purpose of this study was to examine the differences between 3 recovery methods after eliciting muscle damage in recreationally active men relative to maximal isokinetic contractions, perceived muscle soreness, and psychological mood states. Twenty-five recreationally active men (22.15 ± 3.53 years, 75.75 ± 11.91 kg, 180.52 ± 7.3 cm) were randomly matched by V[Combining Dot Above]O2 peak (53.86 ± 6.65 ml·kg·min) and assigned to one of 3 recovery methods: anti-gravity treadmill (G-Trainer) (N = 8), conventional treadmill (N = 8) or static stretching (N = 9). Recovery methods were performed 30 minutes, 24, 48, and 72 hours after a 45-minute downhill run. Following eccentrically biased running, no significant differences were noted in isokinetic knee flexion and extension peak torque, systemic markers of muscle damage, oxidative stress and lipid peroxidation such as serum creatine kinase (CK), superoxide dismutase (SOD), and malondialdehyde (MDA), respectively, and subjective ratings of perceived muscle soreness between recovery methods. The G-Trainer group did however display a higher mood state as indicated by the Profile of Mood State global scores at 24 hours postexercise when compared to the conventional treadmill recovery group (p = 0.035). The improved mood state after the use of the anti-gravity treadmill may provide clinical relevance to other populations.

  14. Long-term strength and allowable stresses of grade 10Kh9MFB and X10CrMoVNb9-1 (T91/P91) chromium heat-resistant steels

    Science.gov (United States)

    Skorobogatykh, V. N.; Danyushevskiy, I. A.; Schenkova, I. A.; Prudnikov, D. A.

    2015-04-01

    Currently, grade X10CrMoVNb9-1 (T91, P91) and 10Kh9MFB (10Kh9MFB-Sh) chromium steels are widely applied in equipment manufacturing for thermal power plants in Russia and abroad. Compilation and comparison of tensile, impact, and long-term strength tests results accumulated for many years of investigations of foreign grade X10CrMoVNb9-1, T91, P91, and domestic grade 10Kh9MFB (10Kh9MFB-Sh) steels is carried out. The property identity of metals investigated is established. High strength and plastic properties of steels, from which pipes and other products are made, for operation under creep conditions are confirmed. Design characteristics of long-term strength on the basis of tests with more than one million of hour-samples are determined ( and at temperatures of 500-650°C). The table of recommended allowable stresses for grade 10Kh9MFB, 10Kh9MFB-SH, X10CrMoVNb9-1, T91, and P91 steels is developed. The long-time properties of pipe welded joints of grade 10Kh9MFB+10Kh9MFB, 10Kh9MFB-Sh+10Kh9MFB-Sh, X10CrMoVNb9-1+X10CrMoVNb9-1, P91+P91, T91+T91, 10Kh9MFB (10Kh9MFB-Sh)+X10CrMoVNb9-1(T/P91) steels is researched. The welded joint reduction factor is experimentally determined.

  15. Effect of the cold-rolling parameters and the yield strength of the strip material on the friction stresses in a deformation zone

    Science.gov (United States)

    Garber, E. A.; Yagudin, I. V.; Ermilov, V. V.; Traino, A. I.

    2009-10-01

    The reliability of the methods of determining the friction coefficient is analyzed, since the friction stresses in the deformation zone during cold rolling significantly affect the quality of cold-rolled sheets and the energy consumption. The well-known experimental data and empirical dependences are shown to contradict each other, and the statistical assurance of these dependences is absent. A database on the interrelated technological and energy-force parameters of a five-stand cold-rolling mill, which includes a wide range of steel grades and strip sizes and shapes, is analyzed. Regression analysis is used to obtain a statistically reliable regression dependence of the friction coefficient in the deformation zone on the most significant technological parameters. The application of this dependence decreases the error of energy-force calculations by more than two times.

  16. Wind Generators

    Science.gov (United States)

    1989-01-01

    When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.

  17. Wind turbine

    Science.gov (United States)

    Cheney, Jr., Marvin C.

    1982-01-01

    A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

  18. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Science.gov (United States)

    2013-05-20

    ...-005, QF07-55-005, QF07-56-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains...

  19. Optimal Structural Reliability of Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Tarp-Johansen, N.J.

    2005-01-01

    The main failure modes of modern large wind turbines are fatigue failure of wings, hub, shaft and main tower, local buckling of main tower, and failure of the foundation. This paper considers reliability-based optimal design of wind turbines. Compared to onshore wind turbines and building...... structures, humans spent little time in the vicinity of offshore wind turbines and the probability of human injury during storm conditions is small. Further environmental pollution will also in general be small in case of failure. One could therefore argue that the reliability level of offshore wind turbines...... can be lower than for onshore wind turbines and other civil engineering structures and can be assessed by reliability-based cost-optimization. Specifically this paper considers the main tower and foundation. Both fatigue and ultimate strength failure modes are included. Different formulations...

  20. Rock strength under explosive loading

    International Nuclear Information System (INIS)

    Rimer, N.; Proffer, W.

    1993-01-01

    This presentation emphasizes the importance of a detailed description of the nonlinear deviatoric (strength) response of the surrounding rock in the numerical simulation of underground nuclear explosion phenomenology to the late times needed for test ban monitoring applications. We will show how numerical simulations which match ground motion measurements in volcanic tuffs and in granite use the strength values obtained from laboratory measurements on small core samples of these rocks but also require much lower strength values after the ground motion has interacted with the rock. The underlying physical mechanisms for the implied strength reduction are not yet well understood, and in fact may depend on the particular rock type. However, constitutive models for shock damage and/or effective stress have been used successfully at S-Cubed in both the Geophysics Program (primarily for DARPA) and the Containment Support Program (for DNA) to simulate late time ground motions measured at NTS in many different rock types

  1. Imaging Shear Strength Along Subduction Faults

    Science.gov (United States)

    Bletery, Quentin; Thomas, Amanda M.; Rempel, Alan W.; Hardebeck, Jeanne L.

    2017-11-01

    Subduction faults accumulate stress during long periods of time and release this stress suddenly, during earthquakes, when it reaches a threshold. This threshold, the shear strength, controls the occurrence and magnitude of earthquakes. We consider a 3-D model to derive an analytical expression for how the shear strength depends on the fault geometry, the convergence obliquity, frictional properties, and the stress field orientation. We then use estimates of these different parameters in Japan to infer the distribution of shear strength along a subduction fault. We show that the 2011 Mw9.0 Tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength. This observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength. With increasing constraints on the different parameters at play, our approach could, in the future, help identify favorable locations for large earthquakes.

  2. Imaging shear strength along subduction faults

    Science.gov (United States)

    Bletery, Quentin; Thomas, Amanda M.; Rempel, Alan W.; Hardebeck, Jeanne L.

    2017-01-01

    Subduction faults accumulate stress during long periods of time and release this stress suddenly, during earthquakes, when it reaches a threshold. This threshold, the shear strength, controls the occurrence and magnitude of earthquakes. We consider a 3-D model to derive an analytical expression for how the shear strength depends on the fault geometry, the convergence obliquity, frictional properties, and the stress field orientation. We then use estimates of these different parameters in Japan to infer the distribution of shear strength along a subduction fault. We show that the 2011 Mw9.0 Tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength. This observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength. With increasing constraints on the different parameters at play, our approach could, in the future, help identify favorable locations for large earthquakes.

  3. Wind - Prototypes on the landscape

    Science.gov (United States)

    Smith, M. L.

    1981-12-01

    Large wind turbines are shown to be attractive to utilities because of the potential for decreasing gas and oil consumption, the relatively low costs for entry into the field, and the wide distribution of wind energy. The total generating capacity can be increased in incremental steps, experience in construction and operation of large turbines have been gained from the NASA Mod O, OA, 1, and 2 models, and advances in manufacturing processes will make the large turbines competitive as replacement power for oil and gas burning utility generators. The 300 ft rotor Mod 2 machines are described, along with designs for the Mod 5A and Mod 5B wind turbines, with 400 and 422 ft, 6.2 and 7.2 MW rotors and outputs, respectively. Current plans for multi-MW windfarms are reviewed, and the option of using the land around large wind turbines for other purposes is stressed.

  4. Bond strength of masonry

    NARCIS (Netherlands)

    Pluijm, van der R.; Vermeltfoort, A.Th.

    1992-01-01

    Bond strength is not a well defined property of masonry. Normally three types of bond strength can be distinguished: - tensile bond strength, - shear (and torsional) bond strength, - flexural bond strength. In this contribution the behaviour and strength of masonry in deformation controlled uniaxial

  5. Epoxy cracking in the epoxy-impregnated superconducting winding: nonuniform dissipation of stress energy in a wire-epoxy matrix model

    International Nuclear Information System (INIS)

    Tsukamoto, O.; Iwasa, Y.

    1985-01-01

    The authors present the epoxy-crack-induced temperature data of copper wires imbedded in wire-epoxy resin composite model at 4.2 K. The experimental results show that the epoxy-crackinduced temperature rise is higher in the copper wires than in the epoxy matrix, indicating that in stress-induced wire-epoxy failure, stress energy stored in the wire-epoxy matrix is preferrentially dissipated in the wire. A plausible mechanism of the nonuniform dissipation is presented

  6. Worldwide potential of wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Flavin, C

    1982-01-01

    A well-documented discussion is presented dealing with the worldwide potential of wind energy as a source of electrical and mechanical power. It is pointed out that 2% of the solar insolation is converted to wind kinetic energy; it is constantly renewed and nondepletable. Efficiency of windmills are discussed (20 to 40%) and payback periods of less than 5 years are cited. Effects of wind velocity and site location are described. Wind pumps are reviewed and the need for wind pumps, particularly in the developing countries is stressed. The generation of electricity by windmills using small turbines is reviewed and appears promising in areas with wind velocities greater than 12 mi/hr. The development of large windmills and groups of windmills (windfarms) for large scale electrical power is discussed, illustrated, and reviewed (offshore sites included). Environmental and safety problems are considered as well as the role of electrical utilities, government support and research activities. It is concluded that the potential contribution of wind energy is immense and that mechanical windmills may become one of the most important renewable technologies. Electrical generating potential is estimated at 20 to 30% of electrical needs. International programs are discussed briefly. 57 references. (MJJ)

  7. Remote Sensing Wind and Wind Shear System.

    Science.gov (United States)

    Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.

  8. Composite wind turbine towers

    Energy Technology Data Exchange (ETDEWEB)

    Polyzois, D. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Civil Engineering

    2008-07-01

    This paper discussed experiments conducted to optimized the advanced composite materials such as fiberglass reinforced plastics (FRP) used to fabricate wind turbine towers. FRP materials are used in tubular steel, lattice, guyed, and reinforced concrete towers. The towers and turbine blades are transported in segments and assembled on-site, sometimes in offshore or remote locations.The FRP composites are used to build towers with a high strength-to-weight ratio as well as to provide resistance to chemical attacks and corrosion. Use of the materials has resulted in towers that do not require heavy installation equipment. Experimental programs were conducted to verify the structural behaviour of the tower structure's individual-scaled cells as well as to evaluate the performance of multi-cell assemblies. Joint assembly designs were optimized, and a filament winding machine was used to conduct the experimental study and to test individual cells. Failure mode analyses were conducted to determine local buckling and shear rupture. Tension, compression, and shear properties of the FRP materials were tested experimentally, and data from the test were then used to develop finite element models of the composite towers as well as to obtain load deflection curves and tip oscillation data. A case study of a 750 kW wind turbine in Churchill, Manitoba was used to test the design. tabs., figs.

  9. Strength Tests on Hulls and Floats

    Science.gov (United States)

    Matthaes, K

    1942-01-01

    The present report deals with strength tests on hulls and floats intended in part for the collection of construction data for the design of these components and in part for the stress analysis of the finished hulls and floats.

  10. Wind energy

    International Nuclear Information System (INIS)

    Portilla S, L.A.

    1995-01-01

    The wind energy or eolic energy is a consequence of solar energy, the one which is absorbed by the atmosphere and is transformed into energy of movement of large bulks of air. In this process the atmosphere acts as the filter to the solar radiation and demotes the ultraviolet beams that result fatal to life in the Earth. The ionosphere is the most external cap and this is ionized by means of absorption process of ultraviolet radiation arising to the Sun. The atmosphere also acts as a trap to the infrared radiation, it that results from the continual process of energetic degradation. In this way, the interaction between Earth - Atmospheres, is behaved as a great greenhouse, maintaining the constant temperatures, including in the dark nights. Processes as the natural convection (that occur by the thermodynamic phenomenon), equatorial calmness, trade winds and against trade winds and global distribution of the air currents are described. The other hand, techniques as the transformation of the wind into energy and its parameters also are shown

  11. Wind power

    International Nuclear Information System (INIS)

    2006-06-01

    This road-map proposes by the Group Total aims to inform the public on the wind power. It presents the principles, the technology takes off, its applications and technology focus, the global market trends and the outlooks and Total commitments in the domain. (A.L.B.)

  12. Design and Analysis of Wind Turbine Blade Hub using Aluminium Alloy AA 6061-T6

    Science.gov (United States)

    Ravikumar, S.; Jaswanthvenkatram, V.; Sai kumar, Y. J. N. V.; Sohaib, S. Md.

    2017-05-01

    This work presents the design and analysis of horizontal axis wind turbine blade hub using different material. The hub is very crucial part of the wind turbine, which experience the loads from the blades and the loads were transmitted to the main shaft. At present wind turbine is more expensive and weights more than a million pounds, with the nacelle, rotor hub and blades accounting for most of the weight. In this work Spheroidal graphite cast iron GGG 40.3 is replaced by aluminium alloy 6061-T6 to enhance the casting properties and also to improve the strength-weight ratio. This transition of material leads to reduction in weight of the wind turbine. All the loads caused by wind and extreme loads on the blades are transferred to the hub. Considering the IEC 61400-1 standard for defining extreme loads on the hub the stress and deflection were calculated on the hub by using Finite element Analysis. Result obtained from ANSYS is compared and discussed with the existing design.

  13. Wind Energy Japan

    Energy Technology Data Exchange (ETDEWEB)

    Komatsubara, Kazuyo [Embassy of the Kingdom of the Netherlands, Tokyo (Japan)

    2012-06-15

    An overview is given of wind energy in Japan: Background; Wind Energy in Japan; Japanese Wind Energy Industry; Government Supports; Useful Links; Major Japanese Companies; Profiles of Major Japanese Companies; Major Wind Energy Projects in Japan.

  14. Wind energy systems

    Science.gov (United States)

    Stewart, H. J.

    1978-01-01

    A discussion on wind energy systems involved with the DOE wind energy program is presented. Some of the problems associated with wind energy systems are discussed. The cost, efficiency, and structural design of wind energy systems are analyzed.

  15. Optimization design of spar cap layup for wind turbine blade

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Based on the aerodynamic shape and structural form of the blade are fixed,a mathematical model of optimization design for wind turbine blade is established.The model is pursued with respect to minimum the blade mass to reduce the cost of wind turbine production.The material layup numbers of the spar cap are chosen as the design variables;while the demands of strength,stiffness and stability of the blade are employed as the constraint conditions.The optimization design for a 1.5 MW wind turbine blade is carried out by combing above objective and constraint conditions at the action of ultimate flapwise loads with the finite element software ANSYS.Compared with the original design,the optimization design result achieves a reduction of 7.2% of the blade mass,the stress and strain distribution of the blade is more reasonable,and there is no occurrence of resonance,therefore its effectiveness is verified.

  16. Differences in the heat stress associated with white sportswear and being semi-nude in exercising humans under conditions of radiant heat and wind at a wet bulb globe temperature of greater than 28 °C.

    Science.gov (United States)

    Tsuji, Michio; Kume, Masashi; Tuneoka, Hideyuki; Yoshida, Tetsuya

    2014-08-01

    This study investigated whether wearing common white sportswear can reduce heat stress more than being semi-nude during exercise of different intensities performed under radiant heat and wind conditions, such as a hot summer day. After a 20-min rest period, eight male subjects performed three 20 min sessions of cycling exercise at a load intensity of 20 % or 50 % of their peak oxygen uptake (VO2peak) in a room maintained at a wet bulb globe temperature (WBGT) of 28.7 ± 0.1 °C using two spot lights and a fan (0.8 m/s airflow). Subjects wore common white sportswear (WS) consisting of a long-sleeved shirt (45 % cotton and 55 % polyester) and short pants (100 % polyester), or only swimming pants (SP) under the semi-nude condition. The mean skin temperature (Tsk) was greater when subjects wore SP than WS under both the 20 % and 50 % exercise conditions. During the 50 % exercise, the rating of perceived exertion (RPE) and thermal sensation (TS), and the increases in esophageal temperature (ΔTes) and heart rate were significantly higher (Pheat storage (S), calculated from the changes in the mean body temperature (0.9Tes + 0.1 Tsk), was significantly lower in the WS trials than in the SP trials during the 20 min resting period before exercise session. However, S was similar between conditions during the 20 % exercise, but was greater in the WS than in the SP trials during 50 % exercise. These results suggest that, under conditions of radiant heat and wind at a WBGT greater than 28 °C, the heat stress associated with wearing common WS is similar to that of being semi-nude during light exercise, but was greater during moderate exercise, and the storage of body heat can be reduced by wearing WS during rest periods.

  17. Wind influence on a coastal buoyant outflow

    Science.gov (United States)

    Whitney, Michael M.; Garvine, Richard W.

    2005-03-01

    This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ Wind events, however, overwhelm the buoyancy-driven flow (∣Ws∣ > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

  18. Enhancing paper strength by optimizing defect configuration

    Science.gov (United States)

    J.M. Considine; W. Skye; W. Chen; D. Matthys; David W. Vahey; K. Turner; R. Rowlands

    2009-01-01

    Poor formation in paper, as denoted by large local variation of mass, tends to reduce maximum tensile strength but has not been well characterized. The effect of grammage variation on tensile strength was studied by introducing carefully placed holes in tensile specimens made of three different paper materials. Previous researchers demonstrated that the point-stress...

  19. The Development of Confidence Limits for Fatigue Strength Data

    International Nuclear Information System (INIS)

    SUTHERLAND, HERBERT J.; VEERS, PAUL S.

    1999-01-01

    Over the past several years, extensive databases have been developed for the S-N behavior of various materials used in wind turbine blades, primarily fiberglass composites. These data are typically presented both in their raw form and curve fit to define their average properties. For design, confidence limits must be placed on these descriptions. In particular, most designs call for the 95/95 design values; namely, with a 95% level of confidence, the designer is assured that 95% of the material will meet or exceed the design value. For such material properties as the ultimate strength, the procedures for estimating its value at a particular confidence level is well defined if the measured values follow a normal or a log-normal distribution. Namely, based upon the number of sample points and their standard deviation, a commonly-found table may be used to determine the survival percentage at a particular confidence level with respect to its mean value. The same is true for fatigue data at a constant stress level (the number of cycles to failure N at stress level S(sub 1)). However, when the stress level is allowed to vary, as with a typical S-N fatigue curve, the procedures for determining confidence limits are not as well defined. This paper outlines techniques for determining confidence limits of fatigue data. Different approaches to estimating the 95/95 level are compared. Data from the MSU/DOE and the FACT fatigue databases are used to illustrate typical results

  20. Atmospheric Wind Relaxations and the Oceanic Response in the California Current Large Marine Ecosystem

    Science.gov (United States)

    Fewings, M. R.; Dorman, C. E.; Washburn, L.; Liu, W.

    2010-12-01

    On the West Coast of North America in summer, episodic relaxation of the upwelling-favorable winds causes warm water to propagate northward from southern to central California, against the prevailing currents [Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. Similar wind relaxations are an important characteristic of coastal upwelling ecosystems worldwide. Although these wind relaxations have an important influence on coastal ocean dynamics, no description exists of the regional atmospheric patterns that lead to wind relaxations in southern California, or of the regional ocean response. We use QuikSCAT wind stress, North American Regional Reanalysis atmospheric pressure products, water temperature and velocity from coastal ocean moorings, surface ocean currents from high-frequency radars, and MODIS satellite sea-surface temperature and ocean color images to analyze wind relaxation events and the ocean response. We identify the events based on an empirical index calculated from NDBC buoy winds [Melton et al. 2009]. We describe the regional evolution of the atmosphere from the Gulf of Alaska to Baja California over the few days leading up to wind relaxations, and the coastal ocean temperature, color, and current response off southern and central California. We analyze ~100 wind relaxation events in June-September during the QuikSCAT mission, 1999-2009. Our results indicate south-central California wind relaxations in summer are tied to mid-level atmospheric low-pressure systems that form in the Gulf of Alaska and propagate southeastward over 3-5 days. As the low-pressure systems reach southern California, the atmospheric pressure gradient along the coast weakens, causing the surface wind stress to relax to near zero. The weak wind signal appears first at San Diego and propagates northward. QuikSCAT data indicate the relaxed winds extend over the entire Southern California Bight and up to 200 km offshore of central California. Atmospheric dynamics in

  1. WIND VARIABILITY IN BZ CAMELOPARDALIS

    International Nuclear Information System (INIS)

    Honeycutt, R. K.; Kafka, S.; Robertson, J. W.

    2013-01-01

    -axisymmetric nature of the stream/disk interaction. Simultaneous photometry and spectroscopy were acquired on three nights in order to test the possible connection between flickering continuum light and the strength of the front-side wind. We found strong agreement on one night, some agreement on another, and no agreement on the third. We suggest that some flickering events lead to only back-side winds which will not have associated P-Cygni profiles.

  2. Structural Analysis of Basalt Fiber Reinforced Plastic Wind Turbine Blade

    Directory of Open Access Journals (Sweden)

    Mengal Ali Nawaz

    2014-07-01

    Full Text Available In this study, Basalt fiber reinforced plastic (BFRP wind turbine blade was analyzed and compared with Glass fiber reinforced plastic blade (GFRP. Finite element analysis (FEA of blade was carried out using ANSYS. Data for FEA was obtained by using rule of mixture. The shell element in ANSYS was used to simulate the wind turbine blade and to conduct its strength analysis. The structural analysis and comparison of blade deformations proved that BFRP wind turbine blade has better strength compared to GFRP wind turbine blade.

  3. Wind Loads on Structures

    DEFF Research Database (Denmark)

    Dyrbye, Claes; Hansen, Svend Ole

    Wind loads have to be taken into account when designing civil engineering structures. The wind load on structures can be systematised by means of the wind load chain: wind climate (global), terrain (wind at low height), aerodynamic response (wind load to pressure), mechanical response (wind...... pressure to structural response) and design criteria. Starting with an introduction of the wind load chain, the book moves on to meteorological considerations, atmospheric boundary layer, static wind load, dynamic wind load and scaling laws used in wind-tunnel tests. The dynamic wind load covers vibrations...... induced by wind turbulence, vortex shedding, flutter and galloping. The book gives a comprehensive treatment of wind effects on structures and it will be useful for consulting engineers designing wind-sensitive structures. It will also be valuable for students of civil engineering as textbook...

  4. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  5. Inverse Relationship of Marine Aerosol and Dust in Antarctic Ice with Fine-Grained Sediment in the South Atlantic Ocean: Implications for Sea-Ice Coverage and Wind Strength

    Directory of Open Access Journals (Sweden)

    Sharon L. Kanfoush

    2012-03-01

    Full Text Available This research seeks to test the hypothesis that natural gamma radiation (NGR from Ocean Drilling Program Site 1094, which displays variability over the last glacial-interglacial cycle similar to dust in the Vostok ice core, reflects fine-grained terrigenous sediment delivered by eolian processes. Grain size was measured on 400 samples spanning 0–20 m in a composite core. Accumulation of the <63μ size fraction at Site 1094 and dust in Vostok exhibit a negative correlation, suggesting the fine sediments are not dominantly eolian. However the technique used for grain size measurements cannot distinguish between terrigenous and biogenous materials; therefore it is possible much fine-grained material is diatoms. An inverse correlation between fine sediments and NGR supports this interpretation, and implies terrigenous materials were at times diluted by microfossils from high biological productivity. Fine marine sediments correlate positively with temperature and negatively with marine aerosol Na+ in Vostok. One plausible explanation is extensive sea-ice of cold intervals steepened ocean-continent temperature gradients, intensified winds, and led to increased transport of dust and marine aerosol to Antarctica yet also reduced biological productivity at Site 1094. Such a reduction despite increases in NGR, potentially representing Fe-rich dust influx, would require light limitation or stratification associated with sea-ice.

  6. Wind conditions for wind turbine design

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B.

    1999-04-01

    Delegates from Europe and USA attended the meeting and discussed general aspects of wind conditions for wind turbine design. The subjects and the presented papers covered a very broad range of aspects of wind conditions and related influence on the wind turbine. (EHS)

  7. Strength properties of concrete at elevated temperatures

    International Nuclear Information System (INIS)

    Freskakis, G.N.; Burrow, R.C.; Debbas, E.B.

    1979-01-01

    A study is presented concerning the compressive strength, modulus of elasticity, and stress-strain relationships of concrete at elevated temperatures. A review of published results provides information for the development of upper and lower bound relationships for compressive strength and the modulus of elasticity and establishes exposure conditions for a lower bound thermal response. The relationships developed from the literature review are confirmed by the results of a verification test program. The strength and elasticity relationships provide a basis for the development of design stress-strain curves for concrete exposed to elevated temperatures

  8. Strength and life under creeping

    International Nuclear Information System (INIS)

    Pospishil, B.

    1982-01-01

    Certain examples of the application of the Lepin modified creep model, which are of interest from technical viewpoint, are presented. Mathematical solution of the dependence of strength limit at elevated temperatures on creep characteristics is obtained. Tensile test at elevated temperatures is a particular case of creep or relaxation and both strength limit and conventional yield strength at elevated temperatures are completely determined by parameters of state equations during creep. The equation of fracture summing during creep is confirmed not only by the experiment data when stresses change sporadically, but also by good reflection of durability curve using the system of equations. The system presented on the basis of parameters of the equations obtained on any part of durability curve, permits to forecast the following parameters of creep: strain, strain rate, life time, strain in the process of fracture. Tensile test at elevated temperature is advisable as an addition when determining creep curves (time-strain curves) [ru

  9. Study on unified fatigue strength assessment method for welded structure. Hot spot stress evaluating method for various combinations of plate thickness and weld leg length; Yosetsu kozo no toitsutekina hiro kyodo hyokaho ni kansuru kenkyu. Itaatsu to yosetsu ashinaga no kumiawase ni taisuru hot spot oryoku sanshutsu ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Nihei, K.; Inamura, F.; Koe, S. [Kawasaki Heavy Industries, Ltd., Kobe (Japan)

    1996-12-31

    There has been tried to apply unified assessment method using hot spot stress, which is effective to evaluate fatigue strength of fillet welded structures for ships and marine structures. This method can be applied to complicated structures and is independent of welding processes. In this study, first, stress analysis has been conducted for two-dimensional fillet welded joint models with various combinations of plate thickness and weld leg length of general fillet structures by means of boundary element method. Then, critical position, which is not affected by local stress concentration due to bead, was determined from the detailed stress distribution in the vicinity of weld toe. As a result, a general equation has been proposed to estimate the hot spot stress by one-point representative method. Second, the fatigue tests of typical fillet welded joints have been conducted by applying this method. Consequently, it was demonstrated that the unified fatigue strength can be evaluated by the S-N data based on hot spot stress range determined from the proposed equation, independent of structural stress concentration. 22 refs., 14 figs.

  10. Study on unified fatigue strength assessment method for welded structure. Hot spot stress evaluating method for various combinations of plate thickness and weld leg length; Yosetsu kozo no toitsutekina hiro kyodo hyokaho ni kansuru kenkyu. Itaatsu to yosetsu ashinaga no kumiawase ni taisuru hot spot oryoku sanshutsu ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Nihei, K; Inamura, F; Koe, S [Kawasaki Heavy Industries, Ltd., Kobe (Japan)

    1997-12-31

    There has been tried to apply unified assessment method using hot spot stress, which is effective to evaluate fatigue strength of fillet welded structures for ships and marine structures. This method can be applied to complicated structures and is independent of welding processes. In this study, first, stress analysis has been conducted for two-dimensional fillet welded joint models with various combinations of plate thickness and weld leg length of general fillet structures by means of boundary element method. Then, critical position, which is not affected by local stress concentration due to bead, was determined from the detailed stress distribution in the vicinity of weld toe. As a result, a general equation has been proposed to estimate the hot spot stress by one-point representative method. Second, the fatigue tests of typical fillet welded joints have been conducted by applying this method. Consequently, it was demonstrated that the unified fatigue strength can be evaluated by the S-N data based on hot spot stress range determined from the proposed equation, independent of structural stress concentration. 22 refs., 14 figs.

  11. Wind Power Meteorology

    DEFF Research Database (Denmark)

    Lundtang Petersen, Erik; Mortensen, Niels Gylling; Landberg, Lars

    Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind...... resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed......: wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed...

  12. Pore pressure buildup and soil stress relaxation in monopile foundations of offshore wind converters; Porenwasserdruckaufbau und Bodenentfestigung um Pfahlgruendungen von Offshore-Windenergieanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Cuellar, Pablo; Baessler, Matthias; Georgi, Steven; Ruecker, Werner [BAM Bundesanstalt fuer Materialforschung und -pruefung, Berlin (Germany). Fachbereich 7.2 Ingenieurbau

    2012-09-15

    For the installation of wind turbines in the offshore environment and their foundation in the seabed it is customary to employ large-diameter steel piles, either in monopile or multi-pile configurations (jacket, tripod, etc..). The effects of cyclic lateral loading on the offshore piles and particularly the possibility of a progressive accumulation of residual pore water pressure within the saturated embedding soil are discussed in this article. Here it is shown that this can lead to significant changes of their behaviour under external loading, which can potentially compromise the foundation's stability or serviceability. Furthermore, some of the singular effects arising during a realistic storm of moderate magnitude as well as their potential for transient damages to the foundation's stiffness are addressed in the paper. For the investigation of these phenomena the authors have employed a coupled bi-phasic analytical model of the offshore foundation. The constitutive model employed for the seabed, in the frame of the theory of Generalized Plasticity, can reproduce some complex features of cyclic soil behaviour such as the tendency for a progressive densification under cyclic loading, which is responsible for the soil liquefaction phenomena in undrained conditions. Finally, some implications and specific recommendations for the design of offshore monopiles in the frame of the limit states are provided. (orig.)

  13. The Strength Compass

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    In the Ph.D-project ͚Strengths-based Learning - Children͛s character strengths as a means to their learning potential͛ 750 Danish children have assessed ͚The Strength Compass͛ in order to identify their strengths and to create awareness of strengths. This was followed by a strengths......-based intervention program in order to explore the strengths. Finally different methods to apply the strength in everyday life at school were applied. The paper presentation will show the results for strengths display for children aged 6-16 in different categories: Different age groups: Are the same strengths...... present in both small children and youths? Gender: Do the results show differences between the two genders? Danish as a mother- tongue language: Do the results show any differences in the strengths display when considering different language and cultural backgrounds? Children with Special Needs: Do...

  14. Sonic Detection and Ranging (SODAR) Wind Profiler Instrument Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Coulter, Richard L. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-04-01

    The SODAR (Sonic Detection and Ranging) wind profiler measures wind profiles and backscattered signal strength between (nominally) 15 meters (m) and 500 m. It operates by transmitting acoustic energy into the atmosphere and measuring the strength and frequency of backscattered energy. The strength of the backscattered signal is determined by the strength of temperature inhomogeneities with size on the order of 10 centimeters (cm). Assuming the scattering elements in the atmosphere are moving with the mean wind, the horizontal wind field can be derived. The U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility Mobile Facility (AMF) has a system developed by Scintec, Inc. that transmits a sequence of frequencies to enhance signal determination.

  15. Wind Energy Basics | NREL

    Science.gov (United States)

    Wind Energy Basics Wind Energy Basics We have been harnessing the wind's energy for hundreds of grinding grain. Today, the windmill's modern equivalent-a wind turbine can use the wind's energy to most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and

  16. Prospecting for Wind

    Science.gov (United States)

    Swapp, Andy; Schreuders, Paul; Reeve, Edward

    2011-01-01

    Many people use wind to help meet their needs. Over the years, people have been able to harness or capture the wind in many different ways. More recently, people have seen the rebirth of electricity-generating wind turbines. Thus, the age-old argument about technology being either good or bad can also be applied to the wind. The wind can be a…

  17. Careers in Wind Energy

    Science.gov (United States)

    Liming, Drew; Hamilton, James

    2011-01-01

    As a common form of renewable energy, wind power is generating more than just electricity. It is increasingly generating jobs for workers in many different occupations. Many workers are employed on wind farms: areas where groups of wind turbines produce electricity from wind power. Wind farms are frequently located in the midwestern, western, and…

  18. Increasing the Strength of Adhesively Bonded Joints by Tapering the Adherends

    International Nuclear Information System (INIS)

    GUESS, TOMMY R.; METZINGER, KURT E.

    1999-01-01

    Wind turbine blades are often fabricated with composite materials. These composite blades are frequently attached to a metallic structure with an adhesive bond. For the baseline composite-to-steel joint considered in this study, failure typically occurs when the adhesive debonds from the steel adherend. Previous efforts established that the adhesive peel stresses strongly influence the strength of these joints for both single-cycle and fatigue loading. This study focused on reducing the adhesive peel stresses present in these joints by tapering the steel adherends. Several different tapers were evaluated using finite element analysis before arriving at a final design. To confirm that the selected taper was an improvement to the existing design, the baseline joint and the modified joint were tested in both compression and tension. In these axial tests, the compressive strengths of the joints with tapered adherends were greater than those of the baseline joints for both single-cycle and low-cycle fatigue. In addition, only a minor reduction in tensile strength was observed for the joints with tapered adherends when compared to the baseline joints. Thus, the modification would be expected to enhance the overall performance of this joint

  19. Differences in the heat stress associated with white sportswear and being semi-nude in exercising humans under conditions of radiant heat and wind at a wet bulb globe temperature of greater than 28 °C

    Science.gov (United States)

    Tsuji, Michio; Kume, Masashi; Tuneoka, Hideyuki; Yoshida, Tetsuya

    2014-08-01

    This study investigated whether wearing common white sportswear can reduce heat stress more than being semi-nude during exercise of different intensities performed under radiant heat and wind conditions, such as a hot summer day. After a 20-min rest period, eight male subjects performed three 20 min sessions of cycling exercise at a load intensity of 20 % or 50 % of their peak oxygen uptake (VO2peak) in a room maintained at a wet bulb globe temperature (WBGT) of 28.7 ± 0.1 °C using two spot lights and a fan (0.8 m/s airflow). Subjects wore common white sportswear (WS) consisting of a long-sleeved shirt (45 % cotton and 55 % polyester) and short pants (100 % polyester), or only swimming pants (SP) under the semi-nude condition. The mean skin temperature was greater when subjects wore SP than WS under both the 20 % and 50 % exercise conditions. During the 50 % exercise, the rating of perceived exertion (RPE) and thermal sensation (TS), and the increases in esophageal temperature (ΔTes) and heart rate were significantly higher ( P < 0.001-0.05), or tended to be higher ( P < 0.07), in the WS than SP trials at the end of the third 20-min exercise session. The total sweat loss ( m sw,tot) was also significantly higher in the WS than in the SP trials ( P < 0.05). However, during the 20 % exercise, the m sw,tot during exercise, and the ΔTes, RPE and TS at the end of the second and third sessions of exercise did not differ significant between conditions. The heat storage (S), calculated from the changes in the mean body temperature (0.9Tes + 0.1 ), was significantly lower in the WS trials than in the SP trials during the 20 min resting period before exercise session. However, S was similar between conditions during the 20 % exercise, but was greater in the WS than in the SP trials during 50 % exercise. These results suggest that, under conditions of radiant heat and wind at a WBGT greater than 28 °C, the heat stress associated with wearing common WS is similar to that

  20. Fates of dissolved and particulate materials from the Mississippi river immediately after discharge into the northern Gulf of Mexico, USA, during a period of low wind stress

    Science.gov (United States)

    Dagg, M. J.; Bianchi, T.; McKee, B.; Powell, R.

    2008-07-01

    In June 2003, we conducted a two-part field exercise to examine biogeochemical characteristics of water in the lower Mississippi river during the 4 days prior to discharge and in the Mississippi river plume over 2 days after discharge. Here we describe the fates of materials immediately after their discharge through Southwest Pass of the Mississippi delta into the northern Gulf of Mexico. Changes in surface water properties immediately after discharge were much larger and more rapid than changes prior to discharge. Total suspended matter (TSM) declined, probably due to sinking, dissolved macronutrients were rapidly diminished by mixing and biological uptake, and phytoplankton populations increased dramatically, and then declined. This decline appeared to begin at salinities of approximately 10 and was nearly complete by 15. A large increase in dissolved organic carbon (DOC) occurred over approximately the same salinity range. Weak winds (releasing large amounts of DOC. Macronutrients from the river were utilized by the river phytoplankton community in the extensive freshwater lens. This contrasted with the more typical situation in which river nutrients stimulate a marine phytoplankton bloom at salinities in the mid-20s. We concluded that the direct effects of dissolved and particulate bio-reactive materials discharged by the Mississippi river were spatially restricted at this time to low-salinity water, at least as surface phenomena. After being transported through the lower river essentially unaltered, these materials were biogeochemically processed within days and tens of km. More generally, the mixing rate of plume water with receiving oceanic water has profound effects on the food web structure and biogeochemical cycling in the plume.

  1. Wind energy program overview

    International Nuclear Information System (INIS)

    1992-02-01

    This overview emphasizes the amount of electric power that could be provided by wind power rather than traditional fossil fuels. New wind power markets, advances in technology, technology transfer, and wind resources are some topics covered in this publication

  2. Coupled effects of wind-storms and drought on tree mortality across 115 forest stands from the Western Alps and the Jura mountains.

    Science.gov (United States)

    Csilléry, Katalin; Kunstler, Georges; Courbaud, Benoît; Allard, Denis; Lassègues, Pierre; Haslinger, Klaus; Gardiner, Barry

    2017-12-01

    Damage due to wind-storms and droughts is increasing in many temperate forests, yet little is known about the long-term roles of these key climatic factors in forest dynamics and in the carbon budget. The objective of this study was to estimate individual and coupled effects of droughts and wind-storms on adult tree mortality across a 31-year period in 115 managed, mixed coniferous forest stands from the Western Alps and the Jura mountains. For each stand, yearly mortality was inferred from management records, yearly drought from interpolated fields of monthly temperature, precipitation and soil water holding capacity, and wind-storms from interpolated fields of daily maximum wind speed. We performed a thorough model selection based on a leave-one-out cross-validation of the time series. We compared different critical wind speeds (CWSs) for damage, wind-storm, and stand variables and statistical models. We found that a model including stand characteristics, drought, and storm strength using a CWS of 25 ms -1 performed the best across most stands. Using this best model, we found that drought increased damage risk only in the most southerly forests, and its effect is generally maintained for up to 2 years. Storm strength increased damage risk in all forests in a relatively uniform way. In some stands, we found positive interaction between drought and storm strength most likely because drought weakens trees, and they became more prone to stem breakage under wind-loading. In other stands, we found negative interaction between drought and storm strength, where excessive rain likely leads to soil water saturation making trees more susceptible to overturning in a wind-storm. Our results stress that temporal data are essential to make valid inferences about ecological impacts of disturbance events, and that making inferences about disturbance agents separately can be of limited validity. Under projected future climatic conditions, the direction and strength of these

  3. Casting defects and fatigue behaviour of ductile cast iron for wind turbine components: A comprehensive study

    Energy Technology Data Exchange (ETDEWEB)

    Haerkegaard, G. [Norwegian University of Science and Technology, Dept. of Engineering Design and Materials, Trondheim (Norway); Shirani, M.

    2011-12-15

    Two types of EN-GJS-400-18-LT ductile cast iron were investigated in this research, clean baseline material in the shape of castings with different thicknesses and also defective material from a rejected wind turbine hub. P-S-N curves for baseline EN-GJS-400-18-LT specimens with different dimensions and from castings with different thicknesses at different load ratios were established. Geometrical size effect, technological size effects and mean stress effect on fatigue strength of baseline EN-GJS-400-18-LT were evaluated. Fatigue strength of baseline EN-GJS-400-18-LT was compared with that of defective material from the rejected hub. The effect of defects type, shape, size and position on fatigue strength of this material was evaluated. The hypothesis that the endurance observed in an S-N test can be predicted based on the analysis of crack growth from casting defects through defect-free 'base' material was tested for the analyzed defective material. 3D X-ray computed tomography was use to detect defects in defective specimens and find the defect size distribution. The obtained defect size distribution for the defective material was used in random defect analysis to establish the scatter of fatigue life for defective specimens. Finally both safe-life design and damage tolerant design of wind turbine castings were analyzed and compared. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    OpenAIRE

    Ju Feng; Wen Zhong Shen

    2015-01-01

    Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data a...

  5. Wind farm project economics : value of wind

    Energy Technology Data Exchange (ETDEWEB)

    Bills-Everett, T. [Mainstream Renewable Power, Toronto, ON (Canada)

    2010-07-01

    This PowerPoint presentation discussed methods of increasing the value of wind power projects. Appropriate turbine selection and layout is needed to ensure that wind resources are fully developed. Construction costs have a significant impact on project costs. The world turbine price index has not significantly fluctuated since 2006. Operating costs, and the value of wind power projects, are linked with OPEX fluctuations. Wind power projects can significantly reduce greenhouse gas (GHG) emissions. An increase in wind power capacity will reduce the overall cost of energy produced from wind power. Countries can use wind power as part of a renewable energy portfolio designed to reduce risks related to diminishing petroleum supplies. Wind power will help to ensure a global transition to renewable energy use. tabs., figs.

  6. Wind turbines, is it just wind?

    International Nuclear Information System (INIS)

    Boiteux, M.

    2012-01-01

    The author first outlines that wind energy is not only random, but almost absent in extreme situations when it would be needed (for example and notably, very cold weather without wind). He suggests the association of a gas turbine to each wind turbine, so that the gas turbine will replace non operating wind turbines. He notices that wind turbines are not proximity energy as they were said to be, and that profitability in fact requires tens of grouped giant wind turbines. He also outlines the high cost of construction of grids for the connection of these wind turbines. Thus, he states that wind energy is far from being profitable in the present conditions of electricity tariffs in France

  7. Wind Tunnel Tests of Parabolic Trough Solar Collectors: March 2001--August 2003

    Energy Technology Data Exchange (ETDEWEB)

    Hosoya, N.; Peterka, J. A.; Gee, R. C.; Kearney, D.

    2008-05-01

    Conducted extensive wind-tunnel tests on parabolic trough solar collectors to determine practical wind loads applicable to structural design for stress and deformation, and local component design for concentrator reflectors.

  8. European wind power integration study. Periodic report 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1992-12-31

    This periodic report no. 1 describes the work done in the Danish part of the European Wind Power Integration Study in the period until 1.4.1991. The R and D project was initiated January 1, 1989 upon prior establishment of registration equipment at 7 wind farms and at the Tjaereborg turbine. ELSAM and the meteorological service centre in Karup (VTC-Karup) have supplied data for the task. Wind Predictability, Potential and Benefits, Wind Farm - Grid Interface, Distribution System Strength, Wind Farm Cost and Operation, and Co-generation Wind Turbines/Other renewables were measured and modelled. The statistical distribution of the wind speed variations (changes in wind speed from one period of time to another) has been established with great certainty in the report. The wind speed variations follow a Weibull distribution, irrespective of the time intervals with which the data are considered. Duration curves and power distributions for the 7 wind farms have been estimated. Registration equipment for one-minute measurements was chosen in order to clarify the short-term variations in the wind power production. The possibility of working out production forecasts, to be applied in the daily load dispatching, were to be assessed for the total amount of wind power production in Jutland and Funen. The report has examined whether it would be possible to have only one wind measurement and then let it be `guiding` for the total wind farm production. Some simulations are to be carried out in the attempt to set up guidelines for the connection between the strength of distribution systems and the requirements which must be made to the wind farms which are to be places in the system. (EG)

  9. Wind of opportunity

    International Nuclear Information System (INIS)

    Jamieson, Peter

    1999-01-01

    This article traces the move towards the offshore exploitation of wind energy in Europe, and presents information on existing offshore wind energy projects and proposed wind turbine prototypes for offshore operation. The building of the first major offshore wind project at Vindeby, the use of rock socketed monopile foundations for pile drilling and erection of the wind turbines from a mobile jack-up barge, the costs of wind turbines, the fatigue loads on the support structures due to the wind loading, and the offshore wind market in the UK and Europe are discussed. (UK)

  10. Advanced structural wind engineering

    CERN Document Server

    Kareem, Ahsan

    2013-01-01

    This book serves as a textbook for advanced courses as it introduces state-of-the-art information and the latest research results on diverse problems in the structural wind engineering field. The topics include wind climates, design wind speed estimation, bluff body aerodynamics and applications, wind-induced building responses, wind, gust factor approach, wind loads on components and cladding, debris impacts, wind loading codes and standards, computational tools and computational fluid dynamics techniques, habitability to building vibrations, damping in buildings, and suppression of wind-induced vibrations. Graduate students and expert engineers will find the book especially interesting and relevant to their research and work.

  11. Opportunities in Canada's growing wind energy industry

    International Nuclear Information System (INIS)

    Lovshin Moss, S.; Bailey, M.

    2006-01-01

    Investment in Canada's wind sector is projected to reach $8 billion by 2012, and growth of the sector is expected to create over 16,000 jobs. Canada's wind energy capacity grew by 54 per cent in 2005 alone, aided in part by supportive national policies and programs such as the Wind Power Production Incentive (WPPI); the Canadian Renewable Conservation Expense (CRCE) and Class 43.1 Capital Cost Allowance; and support for research and development. Major long-term commitments for clean power purchases, standard offer contracts and renewable portfolio standards in several provinces are encouraging further development of the wind energy sector. This paper argued that the development of a robust Canadian wind turbine manufacturing industry will enhance economic development, create opportunities for export; and mitigate the effects of international wind turbine supply shortages. However, it is not known whether Canadian wind turbine firms are positioned to capitalize on the sector's recent growth. While Canada imports nearly all its large wind turbine generators and components, the country has technology and manufacturing strengths in advanced power electronics and small wind systems, as well as in wind resource mapping. Wind-diesel and wind-hydrogen systems are being developed in Canada, and many of the hybrid systems will offer significant opportunities for remote communities and off-grid applications. Company partnerships for technology transfer, licensing and joint ventures will accelerate Canada's progress. A recent survey conducted by Industry Canada and the Canadian Wind Energy Association (CanWEA) indicated that the total impact of wind energy related expenditures on economic output is nearly $1.38 billion for the entire sector. Annual payroll for jobs in Canada was estimated at $50 million, and substantial employment growth in the next 5 years is expected. Canada offers a strong industrial supply base capable of manufacturing wind turbine generators and

  12. 'Wind turbine syndrome': fact or fiction?

    Science.gov (United States)

    Farboud, A; Crunkhorn, R; Trinidade, A

    2013-03-01

    Symptoms, including tinnitus, ear pain and vertigo, have been reported following exposure to wind turbine noise. This review addresses the effects of infrasound and low frequency noise and questions the existence of 'wind turbine syndrome'. This review is based on a search for articles published within the last 10 years, conducted using the PubMed database and Google Scholar search engine, which included in their title or abstract the terms 'wind turbine', 'infrasound' or 'low frequency noise'. There is evidence that infrasound has a physiological effect on the ear. Until this effect is fully understood, it is impossible to conclude that wind turbine noise does not cause any of the symptoms described. However, many believe that these symptoms are related largely to the stress caused by unwanted noise exposure. There is some evidence of symptoms in patients exposed to wind turbine noise. The effects of infrasound require further investigation.

  13. The Offshore New European Wind Atlas

    Science.gov (United States)

    Karagali, I.; Hahmann, A. N.; Badger, M.; Hasager, C.; Mann, J.

    2017-12-01

    The New European Wind Atlas (NEWA) is a joint effort of research agencies from eight European countries, co-funded under the ERANET Plus Program. The project is structured around two areas of work: development of dynamical downscaling methodologies and measurement campaigns to validate these methodologies, leading to the creation and publication of a European wind atlas in electronic form. This atlas will contain an offshore component extending 100 km from the European coasts. To achieve this, mesoscale models along with various observational datasets are utilised. Scanning lidars located at the coastline were used to compare the coastal wind gradient reproduced by the meso-scale model. Currently, an experimental campaign is occurring in the Baltic Sea, with a lidar located in a commercial ship sailing from Germany to Lithuania, thus covering the entire span of the south Baltic basin. In addition, satellite wind retrievals from scatterometers and Synthetic Aperture Radar (SAR) instruments were used to generate mean wind field maps and validate offshore modelled wind fields and identify the optimal model set-up parameters.The aim of this study is to compare the initial outputs from the offshore wind atlas produced by the Weather & Research Forecasting (WRF) model, still in pre-operational phase, and the METOP-A/B Advanced Scatterometer (ASCAT) wind fields, reprocessed to stress equivalent winds at 10m. Different experiments were set-up to evaluate the model sensitivity for the various domains covered by the NEWA offshore atlas. ASCAT winds were utilised to assess the performance of the WRF offshore atlases. In addition, ASCAT winds were used to create an offshore atlas covering the years 2007 to 2016, capturing the signature of various spatial wind features, such as channelling and lee effects from complex coastal topographical elements.

  14. The strength compass

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    of agreement/disagreement. Also the child/teacher is asked whether the actual strength is important and if he or she has the possibilities to apply the strength in the school. In a PhDproject ‘Strengths-based Learning - Children’s Character Strengths as Means to their Learning Potential’ 750 Danish children......Individual paper presentation: The ‘Strength Compass’. The results of a PhDresearch project among schoolchildren (age 6-16) identifying VIAstrengths concerning age, gender, mother-tongue-langue and possible child psychiatric diagnosis. Strengths-based interventions in schools have a theoretical...... Psychological Publishing Company. ‘The Strength Compass’ is a computer/Ipad based qualitative tool to identify the strengths of a child by a self-survey or a teacher’s survey. It is designed as a visual analogue scale with a statement of the strength in which the child/teacher may declare the degree...

  15. Kinetics model of bainitic transformation with stress

    Science.gov (United States)

    Zhou, Mingxing; Xu, Guang; Hu, Haijiang; Yuan, Qing; Tian, Junyu

    2018-01-01

    Thermal simulations were conducted on a Gleeble 3800 simulator. The main purpose is to investigate the effects of stress on the kinetics of bainitic transformation in a Fe-C-Mn-Si advanced high strength bainitic steel. Previous studies on modeling the kinetics of stress affected bainitic transformation only considered the stress below the yield strength of prior austenite. In the present study, the stress above the yield strength of prior austenite is taken into account. A new kinetics model of bainitic transformation dependent on the stress (including the stresses below and above the yield strength of prior austenite) and the transformation temperature is proposed. The new model presents a good agreement with experimental results. In addition, it is found that the acceleration degree of stress on bainitic transformation increases with the stress whether its magnitude is below or above the yield strength of austenite, but the increasing rate gradually slows down when the stress is above the yield strength of austenite.

  16. Computational testing and design of materials for wind energy and structural applications

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon

    2012-01-01

    The requirements to wind turbine blades and other elements are quite high, In the ideal case, a wind turbine should work for 20.30 years without or with minimum maintenance. That is why the damage resistance and strength of wind blade materials is of great importance. A way to enhance the strengt...

  17. Computational Modelling of Materials for Wind Turbine Blades: Selected DTU Wind Energy Activities.

    Science.gov (United States)

    Mikkelsen, Lars Pilgaard; Mishnaevsky, Leon

    2017-11-08

    Computational and analytical studies of degradation of wind turbine blade materials at the macro-, micro-, and nanoscale carried out by the modelling team of the Section Composites and Materials Mechanics, Department of Wind Energy, DTU, are reviewed. Examples of the analysis of the microstructural effects on the strength and fatigue life of composites are shown. Computational studies of degradation mechanisms of wind blade composites under tensile and compressive loading are presented. The effect of hybrid and nanoengineered structures on the performance of the composite was studied in computational experiments as well.

  18. The theoretical tensile strength of fcc crystals predicted from shear strength calculations

    International Nuclear Information System (INIS)

    Cerny, M; Pokluda, J

    2009-01-01

    This work presents a simple way of estimating uniaxial tensile strength on the basis of theoretical shear strength calculations, taking into account its dependence on a superimposed normal stress. The presented procedure enables us to avoid complicated and time-consuming analyses of elastic stability of crystals under tensile loading. The atomistic simulations of coupled shear and tensile deformations in cubic crystals are performed using first principles computational code based on pseudo-potentials and the plane wave basis set. Six fcc crystals are subjected to shear deformations in convenient slip systems and a special relaxation procedure controls the stress tensor. The obtained dependence of the ideal shear strength on the normal tensile stress seems to be almost linearly decreasing for all investigated crystals. Taking these results into account, the uniaxial tensile strength values in three crystallographic directions were evaluated by assuming a collapse of the weakest shear system. Calculated strengths for and loading were found to be mostly lower than previously calculated stresses related to tensile instability but rather close to those obtained by means of the shear instability analysis. On the other hand, the strengths for loading almost match the stresses related to tensile instability.

  19. Influence of multiaxial preloading on the strength of concrete

    International Nuclear Information System (INIS)

    Linse, D.

    1975-01-01

    In a preliminary study about the influence of the loading direction discs of 20/20/5 cm were loaded at different stress-rates in one direction, then unloaded and loaded up to failure again. Two series of each about 15 specimens were tested: the first series was reloaded in the same direction as it was loaded before. If the preloading was not greater than about 90% of the original short-term uniaxial strength βsub(p), one could achieve in the second loading a higher strength than the strength βsub(p). The second series was reloaded normal to the direction of preloading. By an other series of about 50 specimens the influence of triaxial preloading on the uniaxial strength of concrete was tested. Cubes of 10cm were loaded by brush bearing platens up to a stress which was maximally three times higher than the uniaxial short-term strength βsub(p), then unloaded and tested again under uniaxial compression. The achieved ultimate strength of the cubes at the second loading was obviously dependent upon the stress-state and the stress-rate of the preloading. Multiaxial preloading which is far below the ultimate multiaxial strength can considerably defect the remaining strength of concrete. The decrease in strength was defined by the reduction of the uniaxial strength. It can be assumed that the remaining multiaxial strength is reduced at least to the same rate. Further tests are planned

  20. Wind engineering in Africa

    NARCIS (Netherlands)

    Wisse, J.A.; Stigter, C.J.

    2007-01-01

    The International Association for Wind Engineering (IAWE) has very few contacts in Africa, the second-largest continent. This paper reviews important wind-related African issues. They all require data on wind climate, which are very sparse in Africa. Wind engineering in Africa can assist in

  1. Modeling of Sylgard Adhesive Strength

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, Ralph Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-02-03

    Sylgard is the name of a silicone elastomeric potting material manufactured by Dow Corning Corporation.1 Although the manufacturer cites its low adhesive strength as a feature of this product, thin layers of Sylgard do in fact have a non-negligible strength, which has been measured in recent tensile and shear debonding tests. The adhesive strength of thin layers of Sylgard potting material can be important in applications in which components having signi cantly di erent thermal expansion properties are potted together, and the potted assembly is subjected to temperature changes. The tensile and shear tractions developed on the potted surfaces of the components can cause signi cant internal stresses, particularly for components made of low-strength materials with a high area-to-volume ratio. This report is organized as follows: recent Sylgard debonding tests are rst brie y summarized, with particular attention to the adhesion between Sylgard and PBX 9501, and also between Sylgard and aluminum. Next, the type of numerical model that will be used to simulate the debonding behavior exhibited in these tests is described. Then the calibration of the debonding model will be illustrated. Finally, the method by which the model parameters are adjusted (scaled) to be applicable to other, non- tested bond thicknesses is summarized, and all parameters of the model (scaled and unscaled) are presented so that other investigators can reproduce all of the simulations described in this report as well as simulations of the application of interest.

  2. Numerical Model of High Strength Concrete

    Science.gov (United States)

    Wang, R. Z.; Wang, C. Y.; Lin, Y. L.

    2018-03-01

    The purpose of this paper is to present a three-dimensional constitutive model based on the concept of equivalent uniaxial strain. closed Menetrey-Willam (CMW) failure surfaces which combined with Menetrey-Willam meridian and the cap model are introduced in this paper. Saenz stress-strain model is applied and adjusted by the ultimate strength parameters from CMW failure surface to reflect the latest stress or strain condition. The high strength concrete (HSC) under tri-axial non-proportional loading is considered and the model in this paper performed a good prediction.

  3. Effect of shallow angles on compressive strength of biaxial and triaxial laminates.

    Science.gov (United States)

    Jia, Hongli; Yang, Hyun-Ik

    2016-01-01

    Biaxial (BX) and triaxial (TX) composite laminates with ±45° angled plies have been widely used in wind turbine blades. As the scale of blades increases, BX and TX laminates with shallow-angled plies (i.e. off-axis ply angle shallow-angled BX and TX laminates are critical considering their locations in a wind turbine blade, and therefore in this study, the uniaxial static compression tests were conducted using BX and TX laminates with angled-plies of ±45°, ±35°, and ±25°, for the purpose of evaluation. On the other hand, Mori-Tanaka mean field homogenization method was employed to predict elastic constants of plies in BX and TX laminates involved in tests; linear regression analyses of experimentally measured ply strengths collected from various sources were then performed to estimate strengths of plies in BX and TX laminates; finally, Tsai-Wu, Hashin, and Puck failure criteria were chosen to predict compressive strengths of BX and TX laminates. Comparison between theoretical predictions and test results were carried out to illustrate the effectiveness of each criterion. The compressive strength of BX laminate decreases as ply angle increases, and the trend was successfully predicted by all three failure criteria. For TX laminates, ±35° angled plies rather than ±45° angled plies led to the lowest laminate compressive strength. Hashin and Puck criteria gave good predictions at certain ply angles for TX laminates, but Tsai-Wu criterion was able to capture the unexpected strength variation of TX laminates with ply angle. It was concluded that the transverse tensile stress in 0° plies of TX laminates, which attains its maximum when the off-axis ply angle is 35°, is the dominant factor in failure determination if using Tsai-Wu criterion. This explains the unexpected strength variation of TX laminates with ply angle, and also indicates that proper selection of ply angle is the key to fully utilizing the advantages of shallow-angled laminates.

  4. Accelerated Strength Testing of Thermoplastic Composites

    Science.gov (United States)

    Reeder, J. R.; Allen, D. H.; Bradley, W. L.

    1998-01-01

    Constant ramp strength tests on unidirectional thermoplastic composite specimens oriented in the 90 deg. direction were conducted at constant temperatures ranging from 149 C to 232 C. Ramp rates spanning 5 orders of magnitude were tested so that failures occurred in the range from 0.5 sec. to 24 hrs. (0.5 to 100,000 MPa/sec). Below 204 C, time-temperature superposition held allowing strength at longer times to be estimated from strength tests at shorter times but higher temperatures. The data indicated that a 50% drop in strength might be expected for this material when the test time is increased by 9 orders of magnitude. The shift factors derived from compliance data applied well to the strength results. To explain the link between compliance and strength, a viscoelastic fracture model was investigated. The model, which used compliance as input, was found to fit the strength data only if the critical fracture energy was allowed to vary with temperature reduced stress rate. This variation in the critical parameter severely limits its use in developing a robust time-dependent strength model. The significance of this research is therefore seen as providing both the indication that a more versatile acceleration method for strength can be developed and the evidence that such a method is needed.

  5. SMES for wind energy systems

    Science.gov (United States)

    Paul Antony, Anish

    copper oxide (BSCCO), Yttrium barium copper oxide (YBCO) and Magnesium diboride (MgB 2)] is carried out. The assessed attributes include superconducting transition temperature (Tc), critical current density (Jc ), the irreversibility field (H*) and the superconducting critical field (Hc). Chapter 4 presents the design of a solenoid shaped 1MJ MgB2 SMES. This SMES is used to mitigate the problem of momentary interruptions on a wind turbine. The total length of superconducting wire required for a 1MJ solenoid is calculated to be 21km. The maximum wire lengths currently available are 6km thus we hypothesize that either wire lengths have to be increased or work has to be done on MgB2 superconducting splice technology for multifilament wire. Another design consisting of 8 solenoids storing 120 kJ each is presented. The stress analysis on the proposed coil is performed using finite element analysis exhibiting the safety of the proposed design. Chapter 5 presents the design of a toroid shaped 20MJ MgB2 SMES. This is used to mitigate the problem of sustained interruptions on a wind turbine. The toroid coil is chosen since the magnetic field could be completely contained within the coil, thus reducing stray magnetic fields. A combination of genetic algorithm and nonlinear programming is used in determining the design. In Chapter 6, the different methods of operation of the SMES are examined. The Voltage Source Convertor (VSC) based SMES topology was chosen based on its ease of switching. The VSC switching strategy is based on a sinusoidal pulse width modulation technique. EMTDC/PSCAD software was used to demonstrate the efficacy of the VSC based SMES coupled to a wind turbine. The wind generator was modeled as an induction machine feeding into a load. The simulation results established that SMES connected to wind turbines improved output quality. Although the efficacy of SMES for wind energy has been stated previously in other work, this chapter specifically demonstrates through

  6. Field measurement of wind pressure and wind-induced vibration of large-span spatial cable-truss system under strong wind or typhoon

    Directory of Open Access Journals (Sweden)

    ZHANG Zhihong

    2013-10-01

    Full Text Available In order to ensure wind-resistance safety of large-span pre-stressed flexible system in southeast coast area of China,and to prepare something for revising of current codes of practice or technical standards,the present paper conducts field measurement of wind pressure and wind-induced vibration of a practical and typical large-span spatial cable-truss system-lunar stadium in Yueqing city.Wind loading and wind effects on full-scale structure under strong wind or typhoon in real architectural environment can be obtained directly and effectively.Field measurement is the best way to investigate the wind loading property,wind effects,and wind-structure interactions of large-span flexible system.Measured data will be highly valuable for scientific research and practical design.On the other hand,it also provides the basis of wind-resistance safety design of this kind of tension structures.If any creative development,it would dramatically improve the research level of large-span pre-stressed flexible system in our country.

  7. Wind power plant

    Energy Technology Data Exchange (ETDEWEB)

    Caneghem, A.E. von

    1975-07-24

    The invention applies to a wind power plant in which the wind is used to drive windmills. The plant consists basically of a vertical tube with a lateral wind entrance opening with windmill on its lower end. On its upper end, the tube carries a nozzle-like top which increases the wind entering the tube by pressure decrease. The wind is thus made suitable for higher outputs. The invention is illustrated by constructional examples.

  8. Wind energy analysis system

    OpenAIRE

    2014-01-01

    M.Ing. (Electrical & Electronic Engineering) One of the most important steps to be taken before a site is to be selected for the extraction of wind energy is the analysis of the energy within the wind on that particular site. No wind energy analysis system exists for the measurement and analysis of wind power. This dissertation documents the design and development of a Wind Energy Analysis System (WEAS). Using a micro-controller based design in conjunction with sensors, WEAS measure, calcu...

  9. Wind power. [electricity generation

    Science.gov (United States)

    Savino, J. M.

    1975-01-01

    A historical background on windmill use, the nature of wind, wind conversion system technology and requirements, the economics of wind power and comparisons with alternative systems, data needs, technology development needs, and an implementation plan for wind energy are presented. Considerable progress took place during the 1950's. Most of the modern windmills feature a wind turbine electricity generator located directly at the top of their rotor towers.

  10. Welding stresses

    International Nuclear Information System (INIS)

    Poirier, J.; Barbe, B.; Jolly, N.

    1976-01-01

    The aim is to show how internal stresses are generated and to fix the orders of magnitude. A realistic case, the vertical welding of thick plates free to move one against the other, is described and the deformations and stresses are analyzed. The mathematical model UEDA, which accounts for the elastic modulus, the yield strength and the expansion coefficient of the metal with temperature, is presented. The hypotheses and results given apply only to the instantaneous welding of a welded plate and to a plate welded by a moving electrode [fr

  11. Wind turbines and human health.

    Science.gov (United States)

    Knopper, Loren D; Ollson, Christopher A; McCallum, Lindsay C; Whitfield Aslund, Melissa L; Berger, Robert G; Souweine, Kathleen; McDaniel, Mary

    2014-01-01

    The association between wind turbines and health effects is highly debated. Some argue that reported health effects are related to wind turbine operation [electromagnetic fields (EMF), shadow flicker, audible noise, low-frequency noise, infrasound]. Others suggest that when turbines are sited correctly, effects are more likely attributable to a number of subjective variables that result in an annoyed/stressed state. In this review, we provide a bibliographic-like summary and analysis of the science around this issue specifically in terms of noise (including audible, low-frequency noise, and infrasound), EMF, and shadow flicker. Now there are roughly 60 scientific peer-reviewed articles on this issue. The available scientific evidence suggests that EMF, shadow flicker, low-frequency noise, and infrasound from wind turbines are not likely to affect human health; some studies have found that audible noise from wind turbines can be annoying to some. Annoyance may be associated with some self-reported health effects (e.g., sleep disturbance) especially at sound pressure levels >40 dB(A). Because environmental noise above certain levels is a recognized factor in a number of health issues, siting restrictions have been implemented in many jurisdictions to limit noise exposure. These setbacks should help alleviate annoyance from noise. Subjective variables (attitudes and expectations) are also linked to annoyance and have the potential to facilitate other health complaints via the nocebo effect. Therefore, it is possible that a segment of the population may remain annoyed (or report other health impacts) even when noise limits are enforced. Based on the findings and scientific merit of the available studies, the weight of evidence suggests that when sited properly, wind turbines are not related to adverse health. Stemming from this review, we provide a number of recommended best practices for wind turbine development in the context of human health.

  12. Wind turbines and human health

    Directory of Open Access Journals (Sweden)

    Loren eKnopper

    2014-06-01

    Full Text Available The association between wind turbines and health effects is highly debated. Some argue that reported health effects are related to wind turbine operation (electromagnetic fields (EMF, shadow flicker, audible noise, low frequency noise, infrasound. Others suggest that when turbines are sited correctly, effects are more likely attributable to a number of subjective variables that result in an annoyed/stressed state. In this review we provide a bibliographic-like summary and analysis of the science around this issue specifically in terms of noise (including audible, low frequency noise and infrasound, EMF and shadow flicker. Now there are roughly 60 scientific peer-reviewed articles on this issue. The available scientific evidence suggests that EMF, shadow flicker, low frequency noise and infrasound from wind turbines are not likely to affect human health; some studies have found that audible noise from wind turbines can be annoying to some. Annoyance may be associated with some self-reported health effects (e.g., sleep disturbance especially at sound pressure levels >40 dB(A. Because environmental noise above certain levels is a recognized factor in a number of health issues, siting restrictions have been implemented in many jurisdictions to limit noise exposure. These setbacks should help alleviate annoyance from noise. Subjective variables (attitudes and expectations are also linked to annoyance and have the potential to facilitate other health complaints via the nocebo effect. Therefore, it is possible that a segment of the population may remain annoyed (or report other health impacts even when noise limits are enforced. Based on the findings and scientific merit of the available studies, the weight of evidence suggests that when sited properly, wind turbines are not related to adverse health. Stemming from this review, we provide a number of recommended best practices for wind turbine development in the context of human health.

  13. Wind Turbines and Human Health

    Science.gov (United States)

    Knopper, Loren D.; Ollson, Christopher A.; McCallum, Lindsay C.; Whitfield Aslund, Melissa L.; Berger, Robert G.; Souweine, Kathleen; McDaniel, Mary

    2014-01-01

    The association between wind turbines and health effects is highly debated. Some argue that reported health effects are related to wind turbine operation [electromagnetic fields (EMF), shadow flicker, audible noise, low-frequency noise, infrasound]. Others suggest that when turbines are sited correctly, effects are more likely attributable to a number of subjective variables that result in an annoyed/stressed state. In this review, we provide a bibliographic-like summary and analysis of the science around this issue specifically in terms of noise (including audible, low-frequency noise, and infrasound), EMF, and shadow flicker. Now there are roughly 60 scientific peer-reviewed articles on this issue. The available scientific evidence suggests that EMF, shadow flicker, low-frequency noise, and infrasound from wind turbines are not likely to affect human health; some studies have found that audible noise from wind turbines can be annoying to some. Annoyance may be associated with some self-reported health effects (e.g., sleep disturbance) especially at sound pressure levels >40 dB(A). Because environmental noise above certain levels is a recognized factor in a number of health issues, siting restrictions have been implemented in many jurisdictions to limit noise exposure. These setbacks should help alleviate annoyance from noise. Subjective variables (attitudes and expectations) are also linked to annoyance and have the potential to facilitate other health complaints via the nocebo effect. Therefore, it is possible that a segment of the population may remain annoyed (or report other health impacts) even when noise limits are enforced. Based on the findings and scientific merit of the available studies, the weight of evidence suggests that when sited properly, wind turbines are not related to adverse health. Stemming from this review, we provide a number of recommended best practices for wind turbine development in the context of human health. PMID:24995266

  14. Optimization of Bolt Stress

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2013-01-01

    The state of stress in bolts and nuts with ISO metric thread design is examined and optimized. The assumed failure mode is fatigue so the applied preload and the load amplitude together with the stress concentrations define the connection strength. Maximum stress in the bolt is found at, the fillet...... under the head, at the thread start or at the thread root. To minimize the stress concentration shape optimization is applied....

  15. Backup Mechanical Brake System of the Wind Turbine

    Science.gov (United States)

    Sirotkin, E. A.; Solomin, E. V.; Gandzha, S. A.; Kirpichnikova, I. M.

    2018-01-01

    Paper clarifies the necessity of the emergency mechanical brake systems usage for wind turbines. We made a deep analysis of the wind turbine braking methods available on the market, identifying their strengths and weaknesses. The electromechanical braking appeared the most technically reasonable and economically attractive. We described the developed combined electromechanical brake system for vertical axis wind turbine driven from electric drive with variable torque enough to brake over the turbine even on the storm wind speed up to 45 m/s. The progress was made due to the development of specific kinematic brake system diagram and intelligent control system managed by special operation algorithm.

  16. Strengths-based Learning

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    -being. The Ph.D.-project in Strength-based learning took place in a Danish school with 750 pupils age 6-16 and a similar school was functioning as a control group. The presentation will focus on both the aware-explore-apply processes and the practical implications for the schools involved, and on measurable......Strength-based learning - Children͛s Character Strengths as Means to their Learning Potential͛ is a Ph.D.-project aiming to create a strength-based mindset in school settings and at the same time introducing strength-based interventions as specific tools to improve both learning and well...

  17. Slippage of steel in high and normal strength concrete

    International Nuclear Information System (INIS)

    Ahmed, K.; Siddiqi, Z.A.; Yousaf, M.

    2007-01-01

    Composite action of any reinforced concrete member is only possible if sufficient bond strength exists between steel reinforcing bars and concrete, which can adequately transfer shear stress between them. Bond strength is a function of compressive strength of concrete and hence high strength concrete has higher bond strength (1-2). Therefore required development length can be reduced. In order to investigate the effect of development length on bond stress and slip relationships, experimental investigation was carried out. In this experimentation 24 pull-out samples of high strength concrete and normal strength concrete were casted and tested. The results of this investigation revealed that by increasing the development length from 5db to 10db bond strength increases for both high and normal strength concrete as shown in Figure 11, 12 and 13. However in case of normal strength concrete increase in bond strength is more compared to that in high strength concrete as it is clear from Figure 11 and Figure 13. The increase in bond strength is observed even at 10db development length but the extent is less for 19 mm than 16 mm bars as shown in Figure 12 and Figure 13. This is in agreement with the earlier findings of Chen et al (3) and Harajli et al (1). However in case of HSC the total slippage at 10db is 50% greater than at 5db. This may be due to the fact that more no of concrete keys participate in resisting the slippage. (author)

  18. High-strength beryllium block

    International Nuclear Information System (INIS)

    Pinto, N.P.; Keith, G.H.

    1977-01-01

    Beryllium billets hot isopressed using fine powder of high purity have exceptionally attractive properties; average tensile ultimate, 0.2% offset yield strength and elongation are 590 MPa, 430 MPa and 4.0% respectively. Properties are attributed to the fine grain size (about 4.0 μm average diameter) and the relatively low levels of BeO present as fine, well-dispersed particles. Dynamic properties, e.g., fracture toughness, are similar to those of standard grade, high-purity beryllium. The modulus of beryllium is retained to very high stress levels, and the microyield stress or precision elastic limit is higher than for other grades, including instrument grades. Limited data for billets made from normal-purity fine powders show similar room temperature properties. (author)

  19. Climatic wind tunnel for wind engineering tasks

    Czech Academy of Sciences Publication Activity Database

    Kuznetsov, Sergeii; Pospíšil, Stanislav; Král, Radomil

    2015-01-01

    Roč. 112, 2-B (2015), s. 303-316 ISSN 1897-628X R&D Projects: GA ČR(CZ) GA14-12892S Keywords : climatic tunnel * wind tunnel * atmospheric boundary layer * flow resistance * wind tunnel contraction Subject RIV: JM - Building Engineering https://suw.biblos.pk.edu.pl/resources/i5/i6/i6/i7/i6/r56676/KuznetsovS_ClimaticWind.pdf

  20. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  1. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling; Said Said, Usama; Badger, Jake

    2006-01-01

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  2. Ultimate Strength of Wind Turbine Blades under Multiaxial Loading

    DEFF Research Database (Denmark)

    Haselbach, Philipp Ulrich

    the thickness location. Another modelling approach shows a modelling strategy, where shell and solid elements where combined with the purpose to estimate the strain energy release rate of transversely orientated crack in the trailing edge for different loading conditions. Furthermore, state-of-the-art failure...

  3. Calculation and design of steel bearing structure for wind turbine

    Directory of Open Access Journals (Sweden)

    Bešević Miroslav

    2014-01-01

    Full Text Available Wind represents directed movement of the air and is caused by differences in atmospheric pressure which are caused by uneven heating of air masses. Global and local winds can be distinguished. Global winds have high altitude, while local winds occur in the ground layer of the atmosphere. Given that the global wings have high altitude they cannot be used as propellant for wind generators, but they should be known for their effects on the winds in the lower atmosphere. Modern wind turbines are made with a horizontal axle that has a system for the swiveling axis in the horizontal plane for tracking wind direction changes. They can have different number of blades, but for larger forces three blades are commonly used because they provide the greatest efficiency. Rotor diameter of these turbines depends on the strength and it ranges from 30 m for the power of 300 kW to 115 m for the power of 5 MW. Wind turbines are mounted on vertical steel tower which can be high even more than 100 m. Depending on the diameter of the turbine rotor, column is usually built as steel conical and less often as a steel-frame. This study includes analysis and design of steel tower for wind generator made by manufacturer Vestas, type V112 3MW HH 119 (power 3.2 MW for the construction of wind farm 'Kovačica'.

  4. Adhesive Joints in Wind Turbine Blades

    DEFF Research Database (Denmark)

    Jørgensen, Jeppe Bjørn

    to be determined in several different ways. The accuracy of different ways of measuring residual stresses in the adhesive was tested by applying five different methods on a single sandwich test specimen (laminate/adhesive/laminate) that was instrumented with strain gauges and fiber Bragg gratings. Quasi...... of the project is to develop new- and to improve the existing design rules for adhesive joints in wind turbine blades. The first scientific studies of adhesive joints were based on stress analysis, which requires that the bond-line is free of defects, but this is rarely the case for a wind turbine blade. Instead...... curing and test temperatures) on the formation of transverse cracks in the adhesive were tested experimentally. It was assumed that the transverse cracks evolved due to a combination of mechanical- and residual stresses in the adhesive. A new approach was developed that allows the residual stress...

  5. 75 FR 23263 - Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC...

    Science.gov (United States)

    2010-05-03

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL10-62-000] Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC; Alta Wind VI, LLC; Alta Wind VII, LLC; Alta Wind VIII, LLC; Alta Windpower Development, LLC; TGP Development Company, LLC...

  6. 77 FR 29633 - Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC...

    Science.gov (United States)

    2012-05-18

    ... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-68-000] Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC, Alta Wind XIII, LLC, Alta Wind XIV, LLC, Alta Wind XV, LLC, Alta Windpower Development, LLC, TGP Development Company, LLC...

  7. Aeroelastic analysis of an offshore wind turbine: Design and Fatigue Performance of Large Utility-Scale Wind Turbine Blades

    OpenAIRE

    Fossum, Peter Kalsaas

    2012-01-01

    Aeroelastic design and fatigue analysis of large utility-scale wind turbine blades are performed. The applied fatigue model is based on established methods and is incorporated in an iterative numerical design tool for realistic wind turbine blades. All aerodynamic and structural design properties are available in literature. The software tool FAST is used for advanced aero-servo-elastic load calculations and stress-histories are calculated with elementary beam theory.According to wind energy ...

  8. Wind energy information guide

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-04-01

    This book is divided into nine chapters. Chapters 1--8 provide background and annotated references on wind energy research, development, and commercialization. Chapter 9 lists additional sources of printed information and relevant organizations. Four indices provide alphabetical access to authors, organizations, computer models and design tools, and subjects. A list of abbreviations and acronyms is also included. Chapter topics include: introduction; economics of using wind energy; wind energy resources; wind turbine design, development, and testing; applications; environmental issues of wind power; institutional issues; and wind energy systems development.

  9. Arctic wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Peltola, E. [Kemijoki Oy (Finland); Holttinen, H.; Marjaniemi, M. [VTT Energy, Espoo (Finland); Tammelin, B. [Finnish Meteorological Institute, Helsinki (Finland)

    1998-12-31

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  10. Arctic wind energy

    International Nuclear Information System (INIS)

    Peltola, E.; Holttinen, H.; Marjaniemi, M.; Tammelin, B.

    1998-01-01

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  11. Wind power today

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    This publication highlights initiatives of the US DOE`s Wind Energy Program. 1997 yearly activities are also very briefly summarized. The first article describes a 6-megawatt wind power plant installed in Vermont. Another article summarizes technical advances in wind turbine technology, and describes next-generation utility and small wind turbines in the planning stages. A village power project in Alaska using three 50-kilowatt turbines is described. Very brief summaries of the Federal Wind Energy Program and the National Wind Technology Center are also included in the publication.

  12. Wind Power Career Chat

    Energy Technology Data Exchange (ETDEWEB)

    L. Flowers

    2011-01-01

    This document will teach students about careers in the wind energy industry. Wind energy, both land-based and offshore, is expected to provide thousands of new jobs in the next several decades. Wind energy companies are growing rapidly to meet America's demand for clean, renewable, and domestic energy. These companies need skilled professionals. Wind power careers will require educated people from a variety of areas. Trained and qualified workers manufacture, construct, operate, and manage wind energy facilities. The nation will also need skilled researchers, scientists, and engineers to plan and develop the next generation of wind energy technologies.

  13. Fatigue strength of socket welded pipe joint

    International Nuclear Information System (INIS)

    Iida, K.; Matsuda, F.; Sato, M.; Higuchi, M.; Nakagawa, A.

    1994-01-01

    Fully reversed four point bending fatigue tests were carried out of small diameter socket welded joints made of carbon steels. Experimental parameters are pipe diameter, thickness of pipe and socket wall, throat depth and shape of fillet welds, slip-on and diametral gaps in the socket welding, lack of penetration at the root of fillet welds, and peening of fillet welds. In most cases a fatigue crack started from the root of the fillet, but in the case of higher stress amplitude, it tended to start from the toe of fillet. The standard socket welded joint of 50 mm diameter showed relatively low fatigue strength, 46 MPa in stress amplitude at the 10 7 cycles failure life. This value corresponds to about 1/5 of that of the smoothed base metal specimens in axial fatigue. The fatigue strength showed decrease with increasing pipe diameter, and increase with increasing the thickness of pipe and socket wall. The effects of throat depth and shape of fillet welds on fatigue strength were not significant. Contrary to the expectation, the fatigue strength of the socket welded joint without slip-on gap is higher than that of the joint with the normal gap. A lack of penetration at the root deleteriously reduced fatigue strength, showing 14 MPa in stress amplitude at the 10 7 cycles failure life for the 50 mm diameter socket joint. (orig.)

  14. Zonal wind observations during a geomagnetic storm

    Science.gov (United States)

    Miller, N. J.; Spencer, N. W.

    1986-01-01

    In situ measurements taken by the Wind and Temperature Spectrometer (WATS) onboard the Dynamics Explorer 2 spacecraft during a geomagnetic storm display zonal wind velocities that are reduced in the corotational direction as the storm intensifies. The data were taken within the altitudes 275 to 475 km in the dusk local time sector equatorward of the auroral region. Characteristic variations in the value of the Dst index of horizontal geomagnetic field strength are used to monitor the storm evolution. The detected global rise in atmospheric gas temperature indicates the development of thermospheric heating. Concurrent with that heating, reductions in corotational wind velocities were measured equatorward of the auroral region. Just after the sudden commencement, while thermospheric heating is intense in both hemispheres, eastward wind velocities in the northern hemisphere show reductions ranging from 500 m/s over high latitudes to 30 m/s over the geomagnetic equator. After 10 hours storm time, while northern thermospheric heating is diminishing, wind velocity reductions, distinct from those initially observed, begin to develop over southern latitudes. In the latter case, velocity reductions range from 300 m/s over the highest southern latitudes to 150 m/s over the geomagnetic equator and extend into the Northern Hemisphere. The observations highlight the interhemispheric asymmetry in the development of storm effects detected as enhanced gas temperatures and reduced eastward wind velocities. Zonal wind reductions over high latitudes can be attributed to the storm induced equatorward spread of westward polar cap plasma convection and the resulting plasma-neutral collisions. However, those collisions are less significant over low latitudes; so zonal wind reductions over low latitudes must be attributed to an equatorward extension of a thermospheric circulation pattern disrupted by high latitude collisions between neutrals transported via eastward winds and ions

  15. Comparison of Ares I-X Wind-Tunnel Derived Buffet Environment with Flight Data

    Science.gov (United States)

    Piatak, David J.; Sekula, Martin K.; Rausch, Russ D.

    2011-01-01

    The Ares I-X Flight Test Vehicle (FTV), launched in October 2009, carried with it over 243 buffet verification pressure sensors and was one of the most heavily instrumented launch vehicle flight tests. This flight test represented a unique opportunity for NASA and its partners to compare the wind-tunnel derived buffet environment with that measured during the flight of Ares I-X. It is necessary to define the launch vehicle buffet loads to ensure that structural components and vehicle subsystems possess adequate strength, stress, and fatigue margins when the vehicle structural dynamic response to buffet forcing functions are considered. Ares I-X buffet forcing functions were obtained via wind-tunnel testing of a rigid buffet model (RBM) instrumented with hundreds of unsteady pressure transducers designed to measure the buffet environment across the desired frequency range. This paper discusses the comparison of RBM and FTV buffet environments, including fluctuating pressure coefficient and normalized sectional buffet forcing function root-mean-square magnitudes, frequency content of power-spectral density functions, and force magnitudes of an alternating flow phenomena. Comparison of wind-tunnel model and flight test vehicle buffet environments show very good agreement with root-mean-square magnitudes of buffet forcing functions at the majority of vehicle stations. Spectra proved a challenge to compare because of different wind-tunnel and flight test conditions and data acquisition rates. However, meaningful and promising comparisons of buffet spectra are presented. Lastly, the buffet loads resulting from the transition of subsonic separated flow to supersonic attached flow were significantly over-predicted by wind-tunnel results.

  16. Give Me Strength.

    Institute of Scientific and Technical Information of China (English)

    维拉

    1996-01-01

    Mort had an absolutely terrible day at the office.Everythingthat could go wrong did go wrong.As he walked home he could beheard muttering strange words to himself:“Oh,give me strength,give me strength.”Mort isn’t asking for the kind of strength thatbuilds strong muscles:he’s asking for the courage or ability to

  17. Extreme winds in the Western North Pacific

    DEFF Research Database (Denmark)

    Ott, Søren

    2006-01-01

    satellite images is discussed with emphasis on the empirical basis, which, unfortunately, is not very strong. This is stressed by the fact that Japanese and US agencies arrive at markedly different estimates. Onthe other hand, best track data records cover a long period of time and if not perfect......A statistical model for extreme winds in the western North Pacific is developed, the region on the Planet where tropical cyclones are most common. The model is based on best track data derived mostly from satellite images of tropical cyclones. The methodsused to estimate surface wind speeds from...... they are at least coherent over time in their imperfections. Applying the the Holland model to the best track data, wind profiles can be assigned along the tracks. Fromthis annual wind speed maxima at any particular point in the region can be derived. The annual maxima, in turn, are fitted to a Gumbel distribution...

  18. Creep Strength of Discontinuous Fibre Composites

    DEFF Research Database (Denmark)

    Pedersen, Ole Bøcker

    1974-01-01

    relation between stress and strain rate. Expressions for the interface stress, the creep velocity profile adjacent to the fibres and the creep strength of the composite are derived. Previous results for the creep strength, sc = aVfs0 ( \\frac[( Î )\\dot] [( Î )\\dot] 0 )1/nr1 + 1/n c=Vf001n1+1n in which[( Î...... )\\dot] is the composite creep rate,V f is the fibre volume fraction,sgr 0,epsi 0 andn are the constants in the matrix creep law. The creep strength coefficient agr is found to be very weakly dependent onV f and practically independent ofn whenn is greater than about 6....

  19. Siting wind farms in and around forests

    Energy Technology Data Exchange (ETDEWEB)

    Douglas, N. [Natural Power Consultants, Vancouver, BC (Canada)

    2010-07-01

    This PowerPoint presentation discussed methods of assessing the impact of trees on wind resources. Turbulence is generated and also absorbed by trees. Disturbances generated at tree level are then transported upwards and down-wind by the wind. The turbulence induced by trees can be felt kilometers downwind of forests at wind turbine hub heights. Wind speeds can be less than predicted, and significant over-estimations can occur with modelled results. The effects of high shear and high turbulence can also have an impact on power curve performance and lead to higher levels of mechanical stress. A SCADA analysis was used to demonstrate the impact of forests on power curves. Wind power predictions near forests can be optimized by using a full year of data capture at hub height, full rotor measurements, and a consideration of seasonal variations. Accurate tree maps are needed to determine the effects of trees on wind shear. Various forestry scenarios were modelled to demonstrate the effects of forestry management over time. tabs., figs.

  20. Evolution of wind towards wind turbine

    NARCIS (Netherlands)

    Giyanani, A.H.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.

    2015-01-01

    Remote sensing of the atmospheric variables with the use of LiDAR is a relatively new technology field for wind resource assessment in wind energy. The validation of LiDAR measurements and comparisons is of high importance for further applications of the data.

  1. Fatigue Life of Wind Turbine Blades

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    2010-01-01

    The present paper analyses the possibility of reducing the expected damage accumulation during tower passage by modifying the wind turbine tower design from a traditional mono-tower to a tripod. Due to a narrow stagnation zone the stress reversals and hence the damage accumulation in the blades...

  2. Urban Wind Energy

    DEFF Research Database (Denmark)

    Beller, Christina

    important for the implementation of wind energy conversion systems are the macro and micro wind climate, the siting within a micro wind climate and the choice of a wind turbine model most appropriate for the selected site. In the frame of this work, all these important elements are analyzed and a row......New trends e.g. in architecture and urban planning are to reduce energy needs. Several technologies are employed to achieve this, and one of the technologies, not new as such, is wind energy. Wind turbines are installed in cities, both by companies and private persons on both old and new buildings....... However, an overview of the energy content of the wind in cities and how consequently turbines shall be designed for such wind climates is lacking. The objective of the present work is to deliver an objective and fundamental overview of the social, practical and physical conditions relevant...

  3. Leadership Team | Wind | NREL

    Science.gov (United States)

    Leadership Team Leadership Team Learn more about the expertise and technical skills of the wind Initiative and provides leadership in the focus areas of high-fidelity modeling, wind power plant controls

  4. Danish Wind Power

    DEFF Research Database (Denmark)

    Lund, Henrik; Hvelplund, Frede; Østergaard, Poul Alberg

    In a normal wind year, Danish wind turbines generate the equivalent of approx. 20 percent of the Danish electricity demand. This paper argues that only approx. 1 percent of the wind power production is exported. The rest is used to meet domestic Danish electricity demands. The cost of wind power...... misleading. The cost of CO2 reduction by use of wind power in the period 2004-2008 was only 20 EUR/ton. Furthermore, the Danish wind turbines are not paid for by energy taxes. Danish wind turbines are given a subsidy via the electricity price which is paid by the electricity consumers. In the recent years...... is paid solely by the electricity consumers and the net influence on consumer prices was as low as 1-3 percent on average in the period 2004-2008. In 2008, the net influence even decreased the average consumer price, although only slightly. In Denmark, 20 percent wind power is integrated by using both...

  5. Superconducting Wind Turbine Generators

    Directory of Open Access Journals (Sweden)

    Yunying Pan

    2016-08-01

    Full Text Available Wind energy is well known as a renewable energy because its clean and less polluted characteristic, which is the foundation of development modern wind electricity. To find more efficient wind turbine is the focus of scientists around the world. Compared from conventional wind turbines, superconducting wind turbine generators have advantages at zero resistance, smaller size and lighter weight. Superconducting wind turbine will inevitably become the main trends in this area. This paper intends to introduce the basic concept and principle of superconductivity, and compare form traditional wind turbine to obtain superiority, then to summary three proposed machine concept.While superconductivity have difficulty  in modern technology and we also have proposed some challenges in achieving superconducting wind turbine finally.

  6. High Resolution Atmospheric Modeling for Wind Energy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, M; Bulaevskaya, V; Glascoe, L; Singer, M

    2010-03-18

    The ability of the WRF atmospheric model to forecast wind speed over the Nysted wind park was investigated as a function of time. It was found that in the time period we considered (August 1-19, 2008), the model is able to predict wind speeds reasonably accurately for 48 hours ahead, but that its forecast skill deteriorates rapidly after 48 hours. In addition, a preliminary analysis was carried out to investigate the impact of vertical grid resolution on the forecast skill. Our preliminary finding is that increasing vertical grid resolution does not have a significant impact on the forecast skill of the WRF model over Nysted wind park during the period we considered. Additional simulations during this period, as well as during other time periods, will be run in order to validate the results presented here. Wind speed is a difficult parameter to forecast due the interaction of large and small length scale forcing. To accurately forecast the wind speed at a given location, the model must correctly forecast the movement and strength of synoptic systems, as well as the local influence of topography / land use on the wind speed. For example, small deviations in the forecast track or strength of a large-scale low pressure system can result in significant forecast errors for local wind speeds. The purpose of this study is to provide a preliminary baseline of a high-resolution limited area model forecast performance against observations from the Nysted wind park. Validating the numerical weather prediction model performance for past forecasts will give a reasonable measure of expected forecast skill over the Nysted wind park. Also, since the Nysted Wind Park is over water and some distance from the influence of terrain, the impact of high vertical grid spacing for wind speed forecast skill will also be investigated.

  7. An evaluation of the WindEye wind lidar

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Sjöholm, Mikael; Mann, Jakob

    Prevision of the wind field by remote sensing wind lidars has the potential to improve the performance of wind turbines. The functionality of a WindEye lidar developed by Windar Photonics A/S (Denmark) for the wind energy market was tested in a two months long field experiment. The WindEye sensor...... with a high accuracy during the whole campaign....

  8. Strength and lifetime of polymer glasses

    Energy Technology Data Exchange (ETDEWEB)

    Bartenev, G.M.; Kartasov, E.M.

    1981-03-01

    A kinetic equation of the time-dependence of strength (complete isotherm of lifetime) of polymer glasses at stress values ranging from the limiting stress of the occurence of separation breaks to the critical stress is derived. The curvature of lifetime plots occuring at low and high periods of time in the experiments are considered. The ranges of noncritical state, breaks caused by a thermofluctuation mechanism, a transition range and athermal breaks are discerned. The limitations of applicability of the basic empirical equation of the kinetic theory of the time-dependence of strength are explained. Theoretical equations are suggested for calculating various characteristics of the brittle break, as limiting stress and critical stress, relative critical craze length and coefficient of stress concentration at the craze tip with respect to various geometrical configurations of the craze and its position in the sample. With polymethylmethacrylate as an example in the brittle and quasi-brittle state, as characterized by the transition from the rupture of sets of chemical bonds to individual chemical bonds, the thermofluctuation processes of break in polymer glasses are discussed. The application of the thermofluctuation theory of solids to the quasi-brittle fracture is considered. The growth kinetics of crazes and the corresponding equation of lifetime were found to be described by identical (corresponding) analytical expressions by which the changes of the coefficients of stress concentration in the range of microplastic deformation in front of the growing is covered within a wide region of temperature including the brittle temperature.

  9. Wind Power Utilization Guide.

    Science.gov (United States)

    1981-09-01

    The expres- sions for the rotor torque for a Darrieus machine can be found in Reference 4.16. The Darrieus wind turbine offers the following... turbine generators, wind -driven turbines , power conditioning, wind power, energy conservation, windmills, economic ana \\sis. 20 ABS 1"ACT (Conti,on... turbines , power conditioning requirements, siting requirements, and the economics of wind power under different conditions. Three examples are given to

  10. Wind electric power generation

    International Nuclear Information System (INIS)

    Koch, M.K.; Wind, L.; Canter, B.; Moeller, T.

    2001-01-01

    The monthly statistics of wind electric power generation in Denmark are compiled from information given by the owners of the private wind turbines. For each wind turbine the name of the site and of the type of turbine is given, and the power generation data are given for the month in question together with the total production in 1999 and 2000. Also the data of operation start are given. On the map of Denmark the sites of the wind turbines are marked. (CLS)

  11. Wind electric power generation

    International Nuclear Information System (INIS)

    Koch, M. K.; Wind, L.; Canter, B.; Moeller, T.

    2002-01-01

    The monthly statistics of wind electric power generation in Denmark are compiled from information given by the owners of the private wind turbines. For each wind turbine the name of the site and of the type of turbine is given, and the power generation data are given for the month in question together with the total production in 2000 and 2001. Also the data of operation start are given. On the map of Denmark the sites of the wind turbines are marked. (SM)

  12. Turbulence and wind turbines

    DEFF Research Database (Denmark)

    Brand, Arno J.; Peinke, Joachim; Mann, Jakob

    2011-01-01

    The nature of turbulent flow towards, near and behind a wind turbine, the effect of turbulence on the electricity production and the mechanical loading of individual and clustered wind turbines, and some future issues are discussed.......The nature of turbulent flow towards, near and behind a wind turbine, the effect of turbulence on the electricity production and the mechanical loading of individual and clustered wind turbines, and some future issues are discussed....

  13. The Irish Wind Atlas

    Energy Technology Data Exchange (ETDEWEB)

    Watson, R [Univ. College Dublin, Dept. of Electronic and Electrical Engineering, Dublin (Ireland); Landberg, L [Risoe National Lab., Meteorology and Wind Energy Dept., Roskilde (Denmark)

    1999-03-01

    The development work on the Irish Wind Atlas is nearing completion. The Irish Wind Atlas is an updated improved version of the Irish section of the European Wind Atlas. A map of the irish wind resource based on a WA{sup s}P analysis of the measured data and station description of 27 measuring stations is presented. The results of previously presented WA{sup s}P/KAMM runs show good agreement with these results. (au)

  14. Interpretation of observed relations between solar wind characteristics and effects at ionospheric altitudes

    International Nuclear Information System (INIS)

    Cowley, S.W.H.

    1983-01-01

    This chapter discusses recent developments and remaining questions concerning the behavior of high latitude ionospheric flows and how they depend on solar wind conditions via magnetospheric coupling to the latter. The magnitude and direction of the interplanetary magnetic field (IMF) is found to be the primary factor. The relationships which have been found between the strength of high-latitude flows and solar wind and IMF conditions, and the inferences which can be drawn therefrom concerning the solar wind-magnetosphere coupling processes which result in convection are examined. The east-west asymmetries in highlatitude flows which are found to be associated with the B /SUB y/ (dawn-dusk) component of the IMF are investigated. Related asymmetries are shown to occur in the magnetosphere at large, and the unity of these effects as arising from one straightforward cause is stressed. Recent work on the ''reversed'' sunward flows which occur at high latitudes in association with strong B /SUB z/ in the IMF is described

  15. The Solar Wind Environment in Time

    Science.gov (United States)

    Pognan, Quentin; Garraffo, Cecilia; Cohen, Ofer; Drake, Jeremy J.

    2018-03-01

    We use magnetograms of eight solar analogs of ages 30 Myr–3.6 Gyr obtained from Zeeman Doppler Imaging and taken from the literature, together with two solar magnetograms, to drive magnetohydrodynamical wind simulations and construct an evolutionary scenario of the solar wind environment and its angular momentum loss rate. With observed magnetograms of the radial field strength as the only variant in the wind model, we find that a power-law model fitted to the derived angular momentum loss rate against time, t, results in a spin-down relation Ω ∝ t ‑0.51, for angular speed Ω, which is remarkably consistent with the well-established Skumanich law Ω ∝ t ‑0.5. We use the model wind conditions to estimate the magnetospheric standoff distances for an Earth-like test planet situated at 1 au for each of the stellar cases, and to obtain trends of minimum and maximum wind ram pressure and average ram pressure in the solar system through time. The wind ram pressure declines with time as \\overline{{P}ram}}\\propto {t}2/3, amounting to a factor of 50 or so over the present lifetime of the solar system.

  16. Ultimate Strength of Ship Hulls under Torsion

    DEFF Research Database (Denmark)

    Paik, Jeom Kee; Thayamballi, Anil K.; Pedersen, Preben Terndrup

    2001-01-01

    For a ship hull with large deck openings such as container vessels and some large bulk carriers, the analysis of warping stresses and hatch opening deformations is an essential part of ship structural analyses. It is thus of importance to better understand the ultimate torsional strength characte......For a ship hull with large deck openings such as container vessels and some large bulk carriers, the analysis of warping stresses and hatch opening deformations is an essential part of ship structural analyses. It is thus of importance to better understand the ultimate torsional strength...... characteristics of ships with large hatch openings. The primary aim of the present study is to investigate the ultimate strength characteristics of ship hulls with large hatch openings under torsion. Axial (warping) as well as shear stresses are normally developed for thin-walled beams with open cross sections...... subjected to torsion. A procedure for calculating these stresses is briefly described. As an illustrative example, the distribution and magnitude of warping and shear stresses for a typical container vessel hull cross section under unit torsion is calculated by the procedure. By theoretical and numerical...

  17. Havsnaes wind farm - The project financing of a Swedish wind farm

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-07-01

    In March 2008 the ground breaking project financing of the 95 MW Havsnaes wind farm was completed. Havsnaes represents one of the cornerstones in portfolio of Venus Vind, controlled by HgCapital, where sustainable Scandinavian strength is build through industrial scale wind farms with local presence. At the time, Havsnaes represented the largest energy project financing in the market, it is also the first true project financing of a major Swedish wind farm. The aim of this study is to highlight the process of project financing and additional lessons learnt from the Havsnaes transaction. Investment in renewable energy projects often includes international investors. We welcome the growing Swedish wind market, banks and other financial institutions, politicians and other relevant decision makers to take part of our findings. Sponsorship provided by the Swedish Energy Agency has enabled the completion of this study.

  18. Wind and Yaw correlation

    DEFF Research Database (Denmark)

    Kock, Carsten Weber; Vesth, Allan

    The report describes measurements carried out on a given turbine and period. The measurements are carried out in accordance to Ref. [1]. A comparison between wind speed and wind direction on the met mast and nacelle wind speed and yaw direction is made in accordance to Ref. [2] and the results...

  19. Offshore wind energy developments

    DEFF Research Database (Denmark)

    Stolpe, Mathias; Buhl, Thomas; Sumer, B. Mutlu

    2014-01-01

    This chapter will give a brief overview of a few of the activities within offshore wind energy research, specifically 1) Support structure optimization, 2) Blade coatings for wind turbines; 3) Scour protection of foundations, 4) Offshore HVDC and 5) Offshore wind services....

  20. Wind power outlook 2006

    Energy Technology Data Exchange (ETDEWEB)

    anon.

    2006-04-15

    This annual brochure provides the American Wind Energy Association's up-to-date assessment of the wind industry in the United States. This 2006 general assessment shows positive signs of growth, use and acceptance of wind energy as a vital component of the U.S. energy mix.

  1. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    DEFF Research Database (Denmark)

    Feng, Ju; Shen, Wen Zhong

    2015-01-01

    Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distribu...

  2. Canadian small wind market

    International Nuclear Information System (INIS)

    Moorhouse, E.

    2010-01-01

    This PowerPoint presentation discussed initiatives and strategies adopted by the Canadian Wind Energy Association (CanWEA) to support the development of Canada's small wind market. The general public has shown a significant interest in small wind projects of 300 kW. Studies have demonstrated that familiarity and comfort with small wind projects can help to ensure the successful implementation of larger wind projects. Small wind markets include residential, farming and commercial, and remote community applications. The results of CanWEA market survey show that the small wind market grew by 78 percent in 2008 over 2007, and again in 2009 by 32 percent over 2008. The average turbine size is 1 kW. A total of 11,000 turbines were purchased in 2007 and 2008. Global small wind market growth increased by 110 percent in 2008, and the average turbine size was 2.4 kW. Eighty-seven percent of the turbines made by Canadian mid-size wind turbine manufacturers are exported, and there is now a significant risk that Canada will lose its competitive advantage in small wind manufacturing as financial incentives have not been implemented. American and Canadian-based small wind manufacturers were listed, and small wind policies were reviewed. The presentation concluded with a set of recommendations for future incentives, educational programs and legislation. tabs., figs.

  3. Wind Power Now!

    Science.gov (United States)

    Inglis, David Rittenhouse

    1975-01-01

    The government promotes and heavily subsidizes research in nuclear power plants. Federal development of wind power is slow in comparison even though much research with large wind-electric machines has already been conducted. Unless wind power programs are accelerated it will not become a major energy alternative to nuclear power. (MR)

  4. Power from the Wind

    Science.gov (United States)

    Roman, Harry T.

    2004-01-01

    Wind energy is the fastest-growing renewable energy source in the world. Over the last 20 years, the wind industry has done a very good job of engineering machines, improving materials, and economies of production, and making this energy source a reality. Like all renewable energy forms, wind energy's successful application is site specific. Also,…

  5. Wind power soars

    Energy Technology Data Exchange (ETDEWEB)

    Flavin, C. [Worldwatch Inst., Washington, DC (United States)

    1996-12-31

    Opinions on the world market for wind power are presented in this paper. Some data for global wind power generating capacity are provided. European and other markets are discussed individually. Estimated potential for wind power is given for a number of countries. 3 figs.

  6. Wind and Yaw correlation

    DEFF Research Database (Denmark)

    Kock, Carsten Weber; Vesth, Allan

    The report describes measurements carried out on a given turbine and period. The measurements are carried out in accordance to Ref. [1]. A comparison between wind speed and wind direction on the met mast and nacelle wind speed and yaw direction is made in accordance to Ref. [2] and the results ar...

  7. Wind and Yaw correlation

    DEFF Research Database (Denmark)

    Federici, Paolo; Kock, Carsten Weber

    The report describes measurements carried out on a given turbine and period. The measurements are carried out in accordance to Ref. [1]. A comparison between wind speed and wind direction on the met mast and nacelle wind speed and yaw direction is made in accordance to Ref. [2] and the results...... are presented on graphs and in a table....

  8. Denmark Wind Energy Programme

    DEFF Research Database (Denmark)

    Shen, Wen Zhong

    2015-01-01

    In this chapter, a summary of some ongoing wind energy projects in Denmark is given. The research topics comprise computational model development, wind turbine (WT) design, low-noise airfoil and blade design, control device development, wake modelling and wind farm layout optimization....

  9. Wind: French revolutions

    International Nuclear Information System (INIS)

    Jones, C.

    2006-01-01

    Despite having the second best wind resources in Europe after the UK, the wind industry in France lags behind its European counterparts with just 6 W of installed wind capacity per person. The electricity market in France is dominated by the state-owned Electricite de France (EdF) and its nuclear power stations. However, smaller renewable generators are now in theory allowed access to the market and France has transposed the EU renewables directive into national law. The French governement has set a target of generating 10,000 MW of renewable capacity by 2010. The announcement of an increased feed-in tariff and the introduction of 'development zones' (ZDEs) which could allow fast-tracking of planning for wind projects are also expected to boost wind projects. But grid access and adminstrative burdens remain major barriers. In addition, French politicians and local authorities remain committed to nuclear, though encouraged by the European Commission, wind is beginning to gain acceptance; some 325 wind farms (representing 1557 MW of capacity) were approved between February 2004 and January 2005. France is now regarded by the international wind energy sector as a target market. One of France's leading independent wind developers and its only listed wind company, Theolia, is expected to be one of the major beneficiaries of the acceleration of activity in France, though other companies are keen to maximise the opportunities for wind. France currently has only one indigenous manufacturer of wind turbines, but foreign suppliers are winning orders

  10. Yield strength of attached copper film

    International Nuclear Information System (INIS)

    Zhang Yan; Zhang Jian-Min

    2011-01-01

    Variation of stress in attached copper film with an applied strain is measured by X-ray diffraction combined with a four-point bending method. A lower slope of the initial elastic segment of the curve of X-ray measured stress versus applied strain results from incomplete elastic strain transferred from the substrate to the film due to insufficiently strong interface cohesion. So the slope of the initial elastic segment of the X-ray stress (or X-ray strain directly) of the film against the substrate applied strain may be used to measure the film-substrate cohesive strength. The yield strength of the attached copper film is much higher than that of the bulk material and varies linearly with the inverse of the film thickness. (condensed matter: structural, mechanical, and thermal properties)

  11. Wind energy in Mediterranean Basin

    International Nuclear Information System (INIS)

    Gaudiosi, G.

    1991-01-01

    In its examination of wind energy potential in the Mediterranean Basin, this paper provides brief notes on the Basin's geography; indicates power production and demand; describes the area's wind characteristics and wind monitoring activities; illustrates wind velocity distributions; estimates local wind power production potential; reviews the Basin's wind energy marketing situation and each bordering country's wind energy programs; surveys installed wind energy farms; and assesses national research and commercialization efforts

  12. Finite Element Simulation of Diametral Strength Test of Hydroxyapatite

    International Nuclear Information System (INIS)

    Ozturk, Fahrettin; Toros, Serkan; Evis, Zafer

    2011-01-01

    In this study, the diametral strength test of sintered hydroxyapatite was simulated by the finite element software, ABAQUS/Standard. Stress distributions on diametral test sample were determined. The effect of sintering temperature on stress distribution of hydroxyapatite was studied. It was concluded that high sintering temperatures did not reduce the stress on hydroxyapatite. It had a negative effect on stress distribution of hydroxyapatite after 1300 deg. C. In addition to the porosity, other factors (sintering temperature, presence of phases and the degree of crystallinity) affect the diametral strength of the hydroxyapatite.

  13. Anisotropic Concrete Compressive Strength

    DEFF Research Database (Denmark)

    Gustenhoff Hansen, Søren; Jørgensen, Henrik Brøner; Hoang, Linh Cao

    2017-01-01

    When the load carrying capacity of existing concrete structures is (re-)assessed it is often based on compressive strength of cores drilled out from the structure. Existing studies show that the core compressive strength is anisotropic; i.e. it depends on whether the cores are drilled parallel...

  14. High strength ferritic alloy

    International Nuclear Information System (INIS)

    1977-01-01

    A high strength ferritic steel is specified in which the major alloying elements are chromium and molybdenum, with smaller quantities of niobium, vanadium, silicon, manganese and carbon. The maximum swelling is specified for various irradiation conditions. Rupture strength is also specified. (U.K.)

  15. Photon strength functions

    International Nuclear Information System (INIS)

    Bergqvist, I.

    1976-01-01

    Methods for extracting photon strength functions are briefly discussed. We follow the Brink-Axel approach to relate the strength functions to the giant resonances observed in photonuclear work and summarize the available data on the E1, E2 and M1 resonances. Some experimental and theoretical problems are outlined. (author)

  16. Interviewing to Understand Strengths

    Science.gov (United States)

    Hass, Michael R.

    2018-01-01

    Interviewing clients about their strengths is an important part of developing a complete understanding of their lives and has several advantages over simply focusing on problems and pathology. Prerequisites for skillfully interviewing for strengths include the communication skills that emerge from a stance of not knowing, developing a vocabulary…

  17. Overall bolt stress optimization

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2013-01-01

    The state of stress in bolts and nuts with International Organization for Standardization metric thread design is examined and optimized. The assumed failure mode is fatigue, so the applied preload and the load amplitude together with the stress concentrations define the connection strength....... Maximum stress in the bolt is found at the fillet under the head, at the thread start, or at the thread root. To minimize the stress concentration, shape optimization is applied. Nut shape optimization also has a positive effect on the maximum stress. The optimization results show that designing a nut......, which results in a more evenly distribution of load along the engaged thread, has a limited influence on the maximum stress due to the stress concentration at the first thread root. To further reduce the maximum stress, the transition from bolt shank to the thread must be optimized. Stress reduction...

  18. Simulation of the Impact of New Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Black, Peter; Chen, Shuyi; Hood, Robbie; Johnson, James; Jones, Linwood; Ruf, Chris; Uhlhorn, Eric

    2008-01-01

    The H*Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of surface wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa.gov/hrd/data sub/wind.html. The Hurricane Imaging Radiometer (HIRAD) is a new passive microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRAD is being designed to enhance the current real-time airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft using the operational airbome Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath (approximately 3 x the aircraft altitude, or approximately 2 km from space). The instrument is described in a separate paper presented at this conference. The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a numerical model from the University of Miami, and those results are used to construct H*Wind analyses. Evaluations will be presented on the relative impact of HIRAD and other instruments on H*Wind analyses, including the use of HIRAD from 2 aircraft altitudes and from a space-based platform.

  19. Analysis of bone mineral density of human bones for strength ...

    Indian Academy of Sciences (India)

    Different types of bone strength are required for various ... To statically analyse various methods to find BMD and related material ... bone study for research purpose. ..... and Dagoberto Vela Arvizo 2007 A qualitative stress analysis of a cross ...

  20. Wind Effects on Retention Time in Highway Ponds

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby; Larsen, Torben; Rasmussen, Michael R.

    2007-01-01

    is to evaluate the quality of long term simulations based on historical rain series of the pollutant discharges from roads and highways. The idea of this paper is to evaluate the effects of wind on the retention time and compare the retention time for the situation of a spatial uniform wind shear stress...... with the situation of a "real" spatial non-uniform shear stress distribution on the surface of the pond. The result of this paper shows that wind plays a dominant role for the retention time and flow pattern. Furthermore, the results shows that the differences in retention time between the use of uniform and non...

  1. Wind Effects on Retention Time in Highway Ponds

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby; Larsen, Torben; Rasmussen, Michael R.

    2008-01-01

    is to evaluate the quality of long term simulations based on historical rain series of the pollutant discharges from roads and highways. The idea of this paper is to evaluate the effects of wind on the retention time and compare the retention time for the situation of a spatial uniform wind shear stress...... with the situation of a "real" spatial non-uniform shear stress distribution on the surface of the pond. The result of this paper shows that wind plays a dominant role for the retention time and flow pattern. Furthermore, the results shows that the differences in retention time between the use of uniform and non...

  2. A Wind Forecasting System for Energy Application

    Science.gov (United States)

    Courtney, Jennifer; Lynch, Peter; Sweeney, Conor

    2010-05-01

    Accurate forecasting of available energy is crucial for the efficient management and use of wind power in the national power grid. With energy output critically dependent upon wind strength there is a need to reduce the errors associated wind forecasting. The objective of this research is to get the best possible wind forecasts for the wind energy industry. To achieve this goal, three methods are being applied. First, a mesoscale numerical weather prediction (NWP) model called WRF (Weather Research and Forecasting) is being used to predict wind values over Ireland. Currently, a gird resolution of 10km is used and higher model resolutions are being evaluated to establish whether they are economically viable given the forecast skill improvement they produce. Second, the WRF model is being used in conjunction with ECMWF (European Centre for Medium-Range Weather Forecasts) ensemble forecasts to produce a probabilistic weather forecasting product. Due to the chaotic nature of the atmosphere, a single, deterministic weather forecast can only have limited skill. The ECMWF ensemble methods produce an ensemble of 51 global forecasts, twice a day, by perturbing initial conditions of a 'control' forecast which is the best estimate of the initial state of the atmosphere. This method provides an indication of the reliability of the forecast and a quantitative basis for probabilistic forecasting. The limitation of ensemble forecasting lies in the fact that the perturbed model runs behave differently under different weather patterns and each model run is equally likely to be closest to the observed weather situation. Models have biases, and involve assumptions about physical processes and forcing factors such as underlying topography. Third, Bayesian Model Averaging (BMA) is being applied to the output from the ensemble forecasts in order to statistically post-process the results and achieve a better wind forecasting system. BMA is a promising technique that will offer calibrated

  3. Offshore wind resource estimation for wind energy

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Badger, Merete; Mouche, A.

    2010-01-01

    Satellite remote sensing from active and passive microwave instruments is used to estimate the offshore wind resource in the Northern European Seas in the EU-Norsewind project. The satellite data include 8 years of Envisat ASAR, 10 years of QuikSCAT, and 23 years of SSM/I. The satellite observati......Satellite remote sensing from active and passive microwave instruments is used to estimate the offshore wind resource in the Northern European Seas in the EU-Norsewind project. The satellite data include 8 years of Envisat ASAR, 10 years of QuikSCAT, and 23 years of SSM/I. The satellite...... observations are compared to selected offshore meteorological masts in the Baltic Sea and North Sea. The overall aim of the Norsewind project is a state-of-the-art wind atlas at 100 m height. The satellite winds are all valid at 10 m above sea level. Extrapolation to higher heights is a challenge. Mesoscale...... modeling of the winds at hub height will be compared to data from wind lidars observing at 100 m above sea level. Plans are also to compare mesoscale model results and satellite-based estimates of the offshore wind resource....

  4. Stresses in Dolosse

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Liu, Zhou; Howell, Gary L.

    1991-01-01

    Failures of rubble mound breakwaters armoured with complex types of unreinforced concrete armour units are often due to breakage. This happens when the stresses exceed the material strength. Sufficient parametric studies of the stresses are not yet available to produce design diagrams for structu......Failures of rubble mound breakwaters armoured with complex types of unreinforced concrete armour units are often due to breakage. This happens when the stresses exceed the material strength. Sufficient parametric studies of the stresses are not yet available to produce design diagrams...... for structural integrity. The paper presents the results and the analyses of model tests with 200 kg and 200 g load-cell instrumented Dolosse. Static stresses and wave generated stresses were studied as well as model and scale effects. A preliminary design diagram for Dolosse is presented as well....

  5. Golf in the Wind: Exploring the Effect of Wind on the Accuracy of Golf Shots

    Science.gov (United States)

    Yaghoobian, Neda; Mittal, Rajat

    2015-11-01

    Golf play is highly dependent on the weather conditions with wind being the most significant factor in the unpredictability of the ball landing position. The direction and strength of the wind alters the aerodynamic forces on a ball in flight, and consequently its speed, distance and direction of travel. The fact that local wind conditions on any particular hole change over times-scales ranging all the way from a few seconds to minutes, hours and days introduces an element of variability in the ball trajectory that is not understood. Any such analysis is complicated by the effect of the local terrestrial and vegetation topology, as well as the inherent complexity of golf-ball aerodynamics. In the current study, we use computational modeling to examine the unpredictability of the shots under different wind conditions over Hole-12 at the Augusta National Golf Club, where the Masters Golf Tournament takes place every year. Despite this being the shortest hole on the course, the presence of complex vegetation canopy around this hole introduces a spatial and temporal variability in wind conditions that evokes uncertainty and even fear among professional golfers. We use our model to examine the effect of wind direction and wind-speed on the accuracy of the golf shots at this hole and use the simulations to determine the key aerodynamic factors that affect the accuracy of the shot.

  6. Wind power plant

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, G

    1975-11-20

    A wind power plant is proposed suitable for electicity generation or water pumping. This plant is to be self-adjusting to various wind velocities and to be kept in operation even during violent storms. For this purpose the mast, carrying the wind rotor and pivotable around a horizontal axis is tiltable and equipped with a wind blind. Further claims contain various configurations of the tilting base resp. the cut in of an elastic link, the attachment and design of the wind blind as well as the constructive arrangement of one or more dynamos.

  7. Visualization of wind farms

    International Nuclear Information System (INIS)

    Pahlke, T.

    1994-01-01

    With the increasing number of wind energy installations the visual impact of single wind turbines or wind parks is a growing problem for landscape preservation, leading to resistance of local authorities and nearby residents against wind energy projects. To increase acceptance and to form a basis for planning considerations, it is necessary to develop instruments for the visualization of planned wind parks, showing their integration in the landscape. Photorealistic montages and computer animation including video sequences may be helpful in 'getting the picture'. (orig.)

  8. Wind electric power generation

    International Nuclear Information System (INIS)

    Groening, B.; Koch, M.; Canter, B.; Moeller, T.

    1995-01-01

    The monthly statistics of wind electric power generation in Denmark are compiled from information given by the owners of private wind turbines. For each wind turbine the name of the site and of the type of turbine is given, and the power generation data are given for the month in question together with the total production in 1988 and 1989. Also the data of operation start are given. On the map of Denmark the sites of the wind turbines are marked. The statistics for December 1994 comprise 2328 wind turbines

  9. Potentials of wind power

    International Nuclear Information System (INIS)

    Bezrukikh, P.P.; Bezrukikh, P.P.

    2000-01-01

    The ecological advantages of the wind power facilities (WPF) are considered. The possibilities of small WPF, generating the capacity from 40 W up to 10 kW, are discussed. The basic technical data on the national and foreign small WPF are presented. The combined wind power systems are considered. Special attention is paid to the most perspective wind-diesel systems, which provide for all possible versions of the electro-power supply. Useful recommendations and information on the wind power engineering are given for those, who decided to build up a wind facility [ru

  10. Mapping Wind Energy Controversies

    DEFF Research Database (Denmark)

    Munk, Anders Kristian

    As part the Wind2050 project funded by the Danish Council for Strategic Research we have mapped controversies on wind energy as they unfold online. Specifically we have collected two purpose built datasets, a web corpus containing information from 758 wind energy websites in 6 different countries......, and a smaller social media corpus containing information from 14 Danish wind energy pages on Facebook. These datasets have been analyzed to answer questions like: How do wind proponents and opponents organize online? Who are the central actors? And what are their matters of concern? The purpose of this report...

  11. Wind energy systems

    International Nuclear Information System (INIS)

    Richardson, R.D.; McNerney, G.M.

    1993-01-01

    Wind energy has matured to a level of development where it is ready to become a generally accepted utility generation technology. A brief discussion of this development is presented, and the operating and design principles are discussed. Alternative designs for wind turbines and the tradeoffs that must be considered are briefly compared. Development of a wind energy system and the impacts on the utility network including frequency stability, voltage stability, and power quality are discussed. The assessment of wind power station economics and the key economic factors that determine the economic viability of a wind power plant are presented

  12. The Crab Pulsar and Relativistic Wind

    Science.gov (United States)

    Coroniti, F. V.

    2017-12-01

    The possibility that the Crab pulsar produces a separated ion-dominated and pair-plasma-dominated, magnetically striped relativistic wind is assessed by rough estimates of the polar cap acceleration of the ion and electron primary beams, the pair production of secondary electrons and positrons, and a simple model of the near-magnetosphere-wind zone. For simplicity, only the orthogonal rotator is considered. Below (above) the rotational equator, ions (electrons) are accelerated in a thin sheath, of order (much less than) the width of the polar cap, to Lorentz factor {γ }i≈ (5{--}10)× {10}7({γ }e≈ {10}7). The accelerating parallel electric field is shorted out by ion-photon (curvature synchrotron) pair production. With strong, but fairly reasonable, assumptions, a set of general magnetic geometry relativistic wind equations is derived and shown to reduce to conservation relations that are similar to those of the wind from a magnetic monopole. The strength of the field-aligned currents carried by the primary beams is determined by the wind’s Alfvén critical point condition to be about eight times the Goldreich-Julian value. A simple model for the transition from the dipole region wind to the asymptotic monopole wind zone is developed. The asymptotic ratio of Poynting flux to ion (pair plasma) kinetic energy flux—the wind {σ }w∞ -parameter—is found to be of order {σ }w∞ ≈ 1/2({10}4). The far wind zone is likely to be complex, with the ion-dominated and pair-plasma-dominated magnetic stripes merging, and the oppositely directed azimuthal magnetic fields annihilating.

  13. Danish extreme wind atlas: Background and methods for a WAsP engineering option

    Energy Technology Data Exchange (ETDEWEB)

    Rathmann, O; Kristensen, L; Mann, J [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark); Hansen, S O [Svend Ole Hansen ApS, Copenhagen (Denmark)

    1999-03-01

    Extreme wind statistics is necessary design information when establishing wind farms and erecting bridges, buildings and other structures in the open air. Normal mean wind statistics in terms of directional and speed distribution may be estimated by wind atlas methods and are used to estimate e.g. annual energy output for wind turbines. It is the purpose of the present work to extend the wind atlas method to also include the local extreme wind statistics so that an extreme value as e.g. the 50-year wind can be estimated at locations of interest. Together with turbulence estimates such information is important regarding the necessary strength of wind turbines or structures to withstand high wind loads. In the `WAsP Engineering` computer program a flow model, which includes a model for the dynamic roughness of water surfaces, is used to realise such an extended wind atlas method. With basis in an extended wind atlas, also containing extreme wind statistics, this allows the program to estimate extreme winds in addition to mean winds and turbulence intensities at specified positions and heights. (au) EFP-97. 15 refs.

  14. A compact multi-wire-layered secondary winding for Tesla transformer.

    Science.gov (United States)

    Zhao, Liang; Su, Jian-Cang; Li, Rui; Wu, Xiao-Long; Xu, Xiu-Dong; Qiu, Xu-Dong; Zeng, Bo; Cheng, Jie; Zhang, Yu; Gao, Peng-Cheng

    2017-05-01

    A compact multi-wire-layered (MWL) secondary winding for a Tesla transformer is put forward. The basic principle of this winding is to wind the metal wire on a polymeric base tube in a multi-layer manner. The tube is tapered and has high electrical strength and high mechanical strength. Concentric-circle grooves perpendicular to the axis of the tube are carved on the surface of the tube to wind the wire. The width of the groove is basically equal to the diameter of the wire so that the metal wire can be fixed in the groove without glue. The depth of the groove is n times of the diameter of the wire to realize the n-layer winding manner. All the concentric-circle grooves are connected via a spiral groove on the surface of the tube to let the wire go through. Compared with the traditional one-wire-layered (OWL) secondary winding for the Tesla transformer, the most conspicuous advantage of the MWL secondary winding is that the latter is compact with only a length of 2/n of the OWL. In addition, the MWL winding has the following advantages: high electrical strength since voids are precluded from the surface of the winding, high mechanical strength because polymer is used as the material of the base tube, and reliable fixation in the Tesla transformer as special mechanical connections are designed. A 2000-turn MWL secondary winding is fabricated with a winding layer of 3 and a total length of 1.0 m. Experiments to test the performance of this winding on a Tesla-type pulse generator are conducted. The results show that this winding can boost the voltage to 1 MV at a repetition rate of 50 Hz reliably for a lifetime longer than 10 4 pulses, which proves the feasibility of the MWL secondary winding.

  15. Wind Tunnel Measurements at LM Wind Power

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2012-01-01

    This section presents the results obtained during the experimental campaign that was conducted in the wind tunnel at LM Wind Power in Lunderskov from August 16th to 26th, 2010. The goal of this study is to validate the so-called TNO trailing edge noise model through measurements of the boundary...... layer turbulence characteristics and the far-field noise generated by the acoustic scattering of the turbulent boundary layer vorticies as they convect past the trailing edge. This campaign was conducted with a NACA0015 airfoil section that was placed in the wind tunnel section. It is equipped with high...

  16. Fiber Laser for Wind Speed Measurements

    DEFF Research Database (Denmark)

    Olesen, Anders Sig

    This PhD thesis evaluates the practical construction and use of a Frequency Stepped Pulse Train modulated coherent Doppler wind lidar (FSPT lidar) for wind speed measurement. The concept of Doppler lidar is introduced as a means to measure line of sight wind speed by the Doppler shift of reflected...... Sweeper (LSFS) is introduced and analyzed as a light source for the FSPT lidar. The setup of the LSFS is discussed, and the necessary concepts for modeling and analyzing LSFS noise are developed. The model and measurements are then used to discuss the growth of optical noise in the LSFS and the impact...... on its use in the FSPT lidar. A complex ABCD model is developed and described as a method for calculating spatial and frequency dependency of a lidar’s signal strength. The model includes both spatial and temporal components of the lidar system, enabling a model capable of describing both CW, pulsed...

  17. Wind energy in Europe

    International Nuclear Information System (INIS)

    Evans, L.C.

    1992-01-01

    Wind energy should be an important part of the energy supply mix, both at home and abroad, to provide cleaner air and a more stable fuel supply. Not only can wind energy contribute to solving complex global issues, it also can provide a large market for American technological leadership. Even though utilities are paying more attention to wind in a number of states, there are no plans for major installations of wind power plants in the United States. At the same time, European nations have developed aggressive wind energy development programs, including both ambitious research and development efforts and market incentives. Many countries recognize the importance of the clean energy provided by wind technology and are taking steps to promote their fledgling domestic industries. The emphasis on market incentives is starting to pay off. In 1991, European utilities and developers installed nearly twice as much wind capacity as Americans did. In 1992 the gap will be even greater. This article reviews aggressive incentives offered by European governments to boost their domestic wind industries at home and abroad in this almost $1 billion per year market. By offering substantial incentives - considerably more than the American Wind Energy Association (AWEA) is proposing - European nations are ensuring dramatic near-term wind energy development and are taking a major step toward dominating the international wind industry of the 21st century

  18. Wind integration in Alberta

    International Nuclear Information System (INIS)

    Frost, W.

    2007-01-01

    This presentation described the role of the Alberta Electric System Operator (AESO) for Alberta's interconnected electric system with particular reference to wind integration in Alberta. The challenges of wind integration were discussed along with the requirements for implementing the market and operational framework. The AESO is an independent system operator that directs the reliable operation of Alberta's power grid; develops and operates Alberta's real-time wholesale energy market to promote open competition; plans and develops the province's transmission system to ensure reliability; and provides transmission system access for both generation and load customers. Alberta has over 280 power generating station, with a total generating capacity of 11,742 MW, of which 443 is wind generated. Since 2004, the AESO has been working with industry on wind integration issues, such as operating limits, need for mitigation measures and market rules. In April 2006, the AESO implemented a temporary 900 MW reliability threshold to ensure reliability. In 2006, a Wind Forecasting Working Group was created in collaboration with industry and the Canadian Wind Energy Association in an effort to integrate as much wind as is feasible without compromising the system reliability or the competitive operation of the market. The challenges facing wind integration include reliability issues; predictability of wind power; the need for dispatchable generation; transmission upgrades; and, defining a market and operational framework for the large wind potential in Alberta. It was noted that 1400 MW of installed wind energy capacity can be accommodated in Alberta with approved transmission upgrades. figs

  19. Wind power takes over

    International Nuclear Information System (INIS)

    2002-01-01

    All over the industrialized world concentrated efforts are being made to make wind turbines cover some of the energy demand in the coming years. There is still a long way to go, however, towards a 'green revolution' as far as energy is concerned, for it is quite futile to use wind power for electric heating. The article deals with some of the advantages and disadvantages of developing wind power. In Norway, for instance, environmentalists fear that wind power plants along the coast may have serious consequences for the stocks of white-tailed eagle and golden eagle. An other factor that delays the large-scale application of wind power in Norway is the low price of electricity. Some experts, however, maintain that wind power may already compete with new hydroelectric power of intermediate cost. The investment costs are expected to go down with one third by 2020, when wind power may be the most competitive energy source to utilize

  20. Wind energy conversion system

    Science.gov (United States)

    Longrigg, Paul

    1987-01-01

    The wind energy conversion system includes a wind machine having a propeller connected to a generator of electric power, the propeller rotating the generator in response to force of an incident wind. The generator converts the power of the wind to electric power for use by an electric load. Circuitry for varying the duty factor of the generator output power is connected between the generator and the load to thereby alter a loading of the generator and the propeller by the electric load. Wind speed is sensed electro-optically to provide data of wind speed upwind of the propeller, to thereby permit tip speed ratio circuitry to operate the power control circuitry and thereby optimize the tip speed ratio by varying the loading of the propeller. Accordingly, the efficiency of the wind energy conversion system is maximized.

  1. Estonian wind climate

    International Nuclear Information System (INIS)

    Kull, Ain

    1999-01-01

    Estonia is situated on the eastern coast of the Baltic Sea. This is a region with intensive cyclonic activity and therefore with a relatively high mean wind speed. Atmospheric circulation and its seasonal variation determine the general character of the Estonian wind regime over the Atlantic Ocean and Eurasia. However, the Baltic sea itself is a very important factor affecting wind climate, it has an especially strong influence on the wind regime in costal areas. The mean energy density (W/m 2 ) is a wind energy characteristic that is proportional to the third power of wind speed and describes energy available in a flow of air through a unit area. The mean energy density is a characteristic which has practical importance in regional assessment of snowdrift, storm damage and wind energy

  2. Extreme winds in Denmark

    DEFF Research Database (Denmark)

    Kristensen, L.; Rathmann, O.; Hansen, S.O.

    2000-01-01

    (Technical Report, Danish Technical press, 1970) and by Abild (Technical Report R-522 (EN), Riso National Laboratory, 1994). A short discussion of the wind storm on the 3rd of December 1999 is included. It is demonstrated how the data can be applied to non-standard situations where the roughness length......Wind-speed data from four sites in Denmark have been analyzed in order to obtain estimates of the basic wind velocity, defined as the 50 yr wind speed (10 min averages) under standard conditions, i.e., 10 m over a homogeneous terrain with the roughness length 0.05 m, The sites are Skjern (15 yr......), Kegnaes (7 yr), Sprogo (20 yr), and Tystofte (16 yr). The measured data are wind speed, wind direction, temperature and pressure. The wind records are cleaned for terrain effects by means of WASP (Mortensew ct al., Technical Report I-666 (EN), Riso National Laboratory, 1993. Vol. 2. User's Guide...

  3. Wind tower service lift

    Science.gov (United States)

    Oliphant, David; Quilter, Jared; Andersen, Todd; Conroy, Thomas

    2011-09-13

    An apparatus used for maintaining a wind tower structure wherein the wind tower structure may have a plurality of legs and may be configured to support a wind turbine above the ground in a better position to interface with winds. The lift structure may be configured for carrying objects and have a guide system and drive system for mechanically communicating with a primary cable, rail or other first elongate member attached to the wind tower structure. The drive system and guide system may transmit forces that move the lift relative to the cable and thereby relative to the wind tower structure. A control interface may be included for controlling the amount and direction of the power into the guide system and drive system thereby causing the guide system and drive system to move the lift relative to said first elongate member such that said lift moves relative to said wind tower structure.

  4. Kansas Wind Energy Consortium

    Energy Technology Data Exchange (ETDEWEB)

    Gruenbacher, Don [Kansas State Univ., Manhattan, KS (United States)

    2015-12-31

    This project addresses both fundamental and applied research problems that will help with problems defined by the DOE “20% Wind by 2030 Report”. In particular, this work focuses on increasing the capacity of small or community wind generation capabilities that would be operated in a distributed generation approach. A consortium (KWEC – Kansas Wind Energy Consortium) of researchers from Kansas State University and Wichita State University aims to dramatically increase the penetration of wind energy via distributed wind power generation. We believe distributed generation through wind power will play a critical role in the ability to reach and extend the renewable energy production targets set by the Department of Energy. KWEC aims to find technical and economic solutions to enable widespread implementation of distributed renewable energy resources that would apply to wind.

  5. The strength research of the adhesive joints of sheet structures ...

    African Journals Online (AJOL)

    The research results of stress-strained condition of constructional sheet materials are given in the article. The strength dependence on type, configuration and sizes of adhesive joints is analyzed. The research of the strength dependence was made on the samples from bakelite plywood with the main types of adhesive joints ...

  6. Monitoring of wind load and response for cable-supported bridges in Hong Kong

    Science.gov (United States)

    Wong, Kai-yuen; Chan, Wai-Yee K.; Man, King-Leung

    2001-08-01

    Structural health monitoring for the three cable-supported bridges located in the West of Hong Kong or the Tsing Ma Control Area has been carried out since the opening of these bridges to public traffic. The three cable-supported bridges are referred to as the Tsing Ma (suspension) Bridge, the Kap Shui Mun (cable-stayed) Bridge and the Ting Kau (cable-stayed) Bridge. The structural health monitoring works involved are classified as six monitoring categories, namely, wind load and response, temperature load and response, traffic load and response, geometrical configuration monitoring, strains and stresses/forces monitoring and global dynamic characteristics monitoring. As wind loads and responses had been a major concern in the design and construction stages, this paper therefore outlines the work of wind load and response monitoring on Tsing Ma, Kap Shui Mun and Ting Kau Bridges. The paper starts with a brief description of the sensory systems. The description includes the layout and performance requirements of sensory systems for wind load and responses monitoring. Typical results of wind load and response monitoring in graphical forms are then presented. These graphical forms include the plots of wind rose diagrams, wind incidences vs wind speeds, wind turbulence intensities, wind power spectra, gust wind factors, coefficient of terrain roughness, extreme wind analyses, deck deflections/rotations vs wind speeds, acceleration spectra, acceleration/displacement contours, and stress demand ratios. Finally conclusions on wind load and response monitoring on the three cable-supported bridges are drawn.

  7. IIW guidelines on weld quality in relationship to fatigue strength

    CERN Document Server

    Jonsson, Bertil; Hobbacher, A F; Kassner, M; Marquis, G

    2016-01-01

    This book presents guidelines on quantitative and qualitative measures of the geometric features and imperfections of welds to ensure that it meets the fatigue strength requirements laid out in the recommendations of the IIW (International Institute of Welding). Welds that satisfy these quality criteria can be assessed in accordance with existing IIW recommendations based on nominal stress, structural stress, notch stress or linear fracture mechanics. Further, the book defines more restrictive acceptance criteria based on weld geometry features and imperfections with increased fatigue strength. Fatigue strength for these welds is defined as S-N curves expressed in terms of nominal applied stress or hot spot stress. Where appropriate, reference is made to existing quality systems for welds.In addition to the acceptance criteria and fatigue assessment curves, the book also provides guidance on their inspection and quality control. The successful implementation of these methods depends on adequate training for o...

  8. Second wind in the offshore wind industry

    International Nuclear Information System (INIS)

    Philippe, Edouard; Neyme, Eric; Deboos, Christophe; Villageois, Jean-Remy; Gouverneur, Philippe; Gerard, Bernard; Fournier, Eric; Petrus, Raymond; Lemarquis, David; Dener, Marc; Bivaud, Jean-Pierre; Lemaire, Etienne; Nielsen, Steffen; Lafon, Xavier; Lagandre, Pierre; Nadai, Alain; Pinot de Villechenon, Edouard; Westhues, Markus; Herpers, Frederick; Bisiaux, Christophe; Sperlich, Miriam; Bales, Vincent; Vandenbroeck, Jan; His, Stephane; Derrey, Thierry; Barakat, Georges; Dakyo, Brayima; Carme, Laurent; Petit, Frederic; Ytournel, Sophie; Westhues, Markus; Diller, Armin; Premont, Antoine de; Ruer, Jacques; Lanoe, Frederic; Declercq, Jan; Holmager, Morten; Fidelin, Daniel; Guillet, Jerome; Dudziak, Gregory; Lapierre, Anne; Couturier, Ludovic; Audineau, Jean-Pierre; Rouaix, Eric; De Roeck, Yann-Herve; Quesnel, Louis; Duguet, Benjamin

    2011-06-01

    After several keynote addresses, this publication contains contributions and Power Point presentations proposed during this conference on the development of offshore wind energy. The successive sessions addressed the following issues: the offshore mass production of electricity (examples of Denmark and Belgium, laying and protecting offshore cables), the space, economic and environmental planning (the Danish experience, the role of the Coastal area integrated management, importance of the public debate, so on), the logistics of port infrastructures (simulation tools, example of Bremerhaven, issues related to project management), innovation at the core of industrial strategies (high power wind turbines, the 6 MW Alstom turbine, chain value and innovation in offshore wind energy, the Vertiwing innovating project of a floating wind turbine, a bench test in Charleston, foundations, gravity base structures, the British experience, the Danish experience), the economic and organisational conditions for development, the validation and certification of technologies

  9. Wind Turbine Contingency Control Through Generator De-Rating

    Science.gov (United States)

    Frost, Susan; Goebel, Kai; Balas, Mark

    2013-01-01

    Maximizing turbine up-time and reducing maintenance costs are key technology drivers for wind turbine operators. Components within wind turbines are subject to considerable stresses due to unpredictable environmental conditions resulting from rapidly changing local dynamics. In that context, systems health management has the aim to assess the state-of-health of components within a wind turbine, to estimate remaining life, and to aid in autonomous decision-making to minimize damage to the turbine. Advanced contingency control is one way to enable autonomous decision-making by providing the mechanism to enable safe and efficient turbine operation. The work reported herein explores the integration of condition monitoring of wind turbines with contingency control to balance the trade-offs between maintaining system health and energy capture. The contingency control involves de-rating the generator operating point to achieve reduced loads on the wind turbine. Results are demonstrated using a high fidelity simulator of a utility-scale wind turbine.

  10. SUSTAINABLE CONCRETE FOR WIND TURBINE FOUNDATIONS.

    Energy Technology Data Exchange (ETDEWEB)

    BERNDT,M.L.

    2004-06-01

    % by volume steel fibers. The use of recycled concrete aggregate in the conventional and 50% slag mixes was also studied. Properties investigated included compressive and tensile strengths, elastic modulus, coefficient of permeability, thermal conductivity and durability in seawater and sulfate solutions. It was determined that the mixes containing 50% slag gave the best overall performance. Slag was particularly beneficial for concrete that used recycled aggregate and could reduce strength losses. Initial durability results indicated that corrosion of fibers in the different concrete mixes when exposed to seawater was minimal. Future research needs to include more detailed studies of mix design and properties of concrete for wind turbine foundations. Emphasis on slag-modified mixes with natural and recycled concrete aggregate is recommended. The proportion of slag that can be incorporated in the concrete needs to be optimized, as does the grading of recycled aggregate. The potential for using silica fume in conjunction with slag is worth exploring as this may further enhance strength and durability. Longer-term durability studies are necessary and other pertinent properties of concrete that require investigation include damping characteristics, pullout strength, fatigue strength and risk of thermal cracking. The properties of sustainable concrete mixes need to be integrated with studies on the structural behavior of wind turbine foundations in order to determine the optimal mix design and to examine means of reducing conservatism and cost of foundations.

  11. Creep strength and rupture ductility of creep strength enhanced ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Kushima, Hideaki; Sawada, Kota; Kimura, Kazuhiro [National Inst. for Materials Science, Tsukuba, Ibaraki (Japan)

    2010-07-01

    Creep strength and rupture ductility of Creep Strength Enhanced Ferritic (CSEF) steels were investigated from a viewpoint of stress dependence in comparison with conventional low alloy ferritic creep resistant steels. Inflection of stress vs. time to rupture curve was observed at 50% of 0.2% offset yield stress for both CSEF and conventional ferritic steels. Creep rupture ductility tends to decrease with increase in creep exposure time, however, those of conventional low alloy steels indicate increase in the long-term. Creep rupture ductility of the ASME Grades 92 and 122 steels indicates drastic decrease with decrease in stress at 50% of 0.2% offset yield stress. Stress dependence of creep rupture ductility of the ASME Grades 92 and 122 steels is well described by stress ratio to 0.2% offset yield stress, regardless of temperature. Drop of creep rupture ductility is caused by inhomogeneous recovery at the vicinity of prior austenite grain boundary, and remarkable drop of creep rupture ductility of CSEF steels should be derived from those stabilized microstructure. (orig.)

  12. Wind impact on the Black Sea ecosystem

    Science.gov (United States)

    Stanichny, Sergey; Ratner, Yuriy; Shokurov, Mike; Stanychna, Rimma; Soloviev, Dmytro; Burdyugov, Vyacheslav

    2010-05-01

    Combination of the recent satellite and meteorological data for the regional investigation allowed to describe new features of the processes in marine ecosystem and detect some relations with wind variability for different time scales. Next topics are highlighted in presentation: 1. Inter-annual variability of the wind stress curl over the Black Sea. Shift in the atmospheric processes after 2003 year and related variations in chlorophyll concentration and intensity of the mesoscale currents. 2. Like-tropical cyclone in September 2005 and its impact o the Black Sea upper layer. 3. Strong storm November 11, 2007 and oil pollutions of the Kerch Strait. 4. Relation of the Danube waters transport with wind fields for summer 2007 and 2008. 5. "Valley" wind in the Eastern part of the Black Sea and its impact on the Rim current formation. 6. Low wind conditions and blue -green algae bloom. NCEP, SKIRON and MHI MM5 wind data together with AVHRR, MODIS, MERIS, ETM+, QuikSCAT, ASAR (ESA) satellite data were used for investigation. Work was done with support of the SESAME FP7, "Stable Ecosystem" and Operational Oceanography NASU projects.

  13. Observability of wind power

    International Nuclear Information System (INIS)

    Gonot, J.P.; Fraisse, J.L.

    2009-01-01

    The total installed capacity of wind power grows from a few hundred MW at the beginning of 2005 to 3400 MW at the end of 2008. With such a trend, a total capacity of 7000 MW could be reached by 2010. The natural variability of wind power and the difficulty of its predictability require a change in the traditional way of managing supply/demand balance, day-ahead margins and the control of electrical flows. As a consequence, RTE operators should be informed quickly and reliably of the real time output power of wind farms and of its evolvement some hours or days ahead to ensure the reliability of the French electrical power system. French specificities are that wind farms are largely spread over the territory, that 95 % of wind farms have an output power below 10 MW and that they are connected to the distribution network. In this context, new tools were necessary to acquire as soon as possible data concerning wind power. In two years long, RTE set up an observatory of wind production 'IPES system' enable to get an access to the technical characteristics of the whole wind farms, to observe in real time 75 % of the wind generation and to implement a forecast model related to wind generation. (authors)

  14. Financing wind projects

    International Nuclear Information System (INIS)

    Manson, J.

    2006-01-01

    This presentation reviewed some of the partnership opportunities available from GE Energy. GE Energy's ecomagination commitment has promised to double research investment, make customers true partners and reduce greenhouse gases (GHGs). GE Energy's renewable energy team provides a broad range of financial products, and has recently funded 30 wind farms and 2 large solar projects. The company has a diverse portfolio of technology providers and wind regimes, and is increasing their investment in technology. GE Energy recognizes that the wind industry is growing rapidly and has received increased regulatory support that is backed by strong policy and public support. It is expected that Canada will have 3006 wind projects either planned or under construction by 2007. According to GE Energy, successful wind financing is dependent on the location of the site and its wind resources, as well as on the wind developer's power sales agreement. The success of a wind project is also determined by clear financing goals. Site-specific data is needed to determine the quality of wind resource, and off-site data can also be used to provide validation. Proximity to load centres will help to minimize capital costs. Power sales agreements should be based on the project's realistic net capacity factor as well as on the cost of the turbines. The economics of many wind farms is driven by the size of the turbines used. Public consultations are also needed to ensure the success of wind power projects. It was concluded that a good partner will have staying power in the wind power industry, and will understand the time-lines and needs that are peculiar to wind energy developers. refs., tabs., figs

  15. Noise from wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Fegeant, Olivier [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Building Sciences

    2002-02-01

    A rapid growth of installed wind power capacity is expected in the next few years. However, the siting of wind turbines on a large scale raises concerns about their environmental impact, notably with respect to noise. To this end, variable speed wind turbines offer a promising solution for applications in densely populated areas like the European countries, as this design would enable an efficient utilisation of the masking effect due to ambient noise. In rural and recreational areas where wind turbines are sited, the ambient noise originates from the action of wind on the vegetation and about the listener's ear (pseudo-noise). It shows a wind speed dependence similar to that of the noise from a variable speed wind turbine and can therefore mask the latter for a wide range of conditions. However, a problem inherent to the design of these machines is their proclivity to pure tone generation, because of the enhanced difficulty of avoiding structural resonances in the mechanical parts. Pure tones are deemed highly annoying and are severely regulated by most noise policies. In relation to this problem, the vibration transmission of structure-borne sound to the tower of the turbine is investigated, in particular when the tower is stiffened at its upper end. Furthermore, since noise annoyance due to wind turbine is mostly a masking issue, the wind-related sources of ambient noise are studied and their masking potentials assessed. With this aim, prediction models for wind-induced vegetation noise and pseudo-noise have been developed. Finally, closely related to the effect of masking, is the difficulty, regularly encountered by local authorities and wind farm developers, to measure noise immission from wind turbines. A new measurement technique has thus been developed in the course of this work. Through improving the signal-to-noise ratio between wind turbine noise and ambient noise, the new technique yields more accurate measurement results.

  16. Lightweight structure design for wind energy by integrating nanostructured materials

    International Nuclear Information System (INIS)

    Li, Ying; Lu, Jian

    2014-01-01

    Highlights: • Integrate high-strength nano-materials into lightweight design. • Lightweight design scheme for wind turbine tower application. • Expand the bending formulae for tapered tubular structures with varying thickness. • We rewrite the Secant Formula for a tapered beam under eccentric compression. - Abstract: Wind power develops very fast nowadays with high expectation. Although at the mean time, the use of taller towers, however, smacks head-on into the issue of transportability. The engineering base and computational tools have to be developed to match machine size and volume. Consequently the research on the light weight structures of tower is carrying out in the main countries which are actively developing wind energy. This paper reports a new design scheme of light weight structure for wind turbine tower. This design scheme is based on the integration of the nanostructured materials produced by the Surface Mechanical Attrition Treatment (SMAT) process. The objective of this study is to accomplish the weight reduction by optimizing the wall thickness of the tapered tubular structure. The basic methods include the identification of the critical zones and the distribution of the high strength materials according to different necessities. The equivalent strength or stiffness design method and the high strength material properties after SMAT process are combined together. Bending and buckling are two main kinds of static loads concerned in consideration. The study results reveal that there is still enough margin for weight reduction in the traditional wind turbine tower design

  17. Diamagnetic effect in the foremoon solar wind observed by Kaguya

    Science.gov (United States)

    Nishino, Masaki N.; Saito, Yoshifumi; Tsunakawa, Hideo; Miyake, Yohei; Harada, Yuki; Yokota, Shoichiro; Takahashi, Futoshi; Matsushima, Masaki; Shibuya, Hidetoshi; Shimizu, Hisayoshi

    2017-04-01

    Direct interaction between the lunar surface and incident solar wind is one of the crucial phenomena of the planetary plasma sciences. Recent observations by lunar orbiters revealed that strength of the interplanetary magnetic field (IMF) at spacecraft altitude often increases over crustal magnetic fields on the dayside. In addition, variations of the IMF on the lunar night side have been reported in the viewpoint of diamagnetic effect around the lunar wake. However, few studies have been performed for the IMF over non-magnetized regions on the dayside. Here we show an event where strength of the IMF decreases at 100 km altitude on the lunar dayside (i.e. in the foremoon solar wind) when the IMF is almost parallel to the incident solar wind flow, comparing the upstream solar wind data from ACE with Kaguya magnetometer data. The lunar surface below the Kaguya orbit is not magnetized (or very weakly magnetized), and the sunward-travelling protons show signatures of those back-scattered at the lunar surface. We find that the decrease in the magnetic pressure is compensated by the thermal pressure of the back-scattered protons. In other words, the IMF strength in the foremoon solar wind decreases by diamagnetic effect of sunward-travelling protons back-scattered at the lunar dayside surface. Such an effect would be prominent in the high-beta solar wind, and may be ubiquitous in the environment where planetary surface directly interacts with surrounding space plasma.

  18. Wind Turbine Converter Control Interaction with Complex Wind Farm Systems

    DEFF Research Database (Denmark)

    Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth

    2013-01-01

    . The same wind turbine converter control strategy is evaluated in two different wind farms. It is emphasised that the grid-side converter controller should be characterised by sufficient harmonic/noise rejection and adjusted depending on wind farms to which it is connected. Various stability indices......This study presents wind turbine converter stability analysis of wind farms in frequency domain. The interaction between the wind turbine control system and the wind farm structure in wind farms is deeply investigated. Two wind farms (i.e. Horns Rev II and Karnice) are taken into consideration...... in this study. It is shown that wind farm components, such as long high-voltage alternating current cables and park transformers, can introduce significant low-frequency series resonances seen from the wind turbine terminals that can affect wind turbine control system operation and overall wind farm stability...

  19. Burst strength of tubing and casing based on twin shear unified strength theory.

    Science.gov (United States)

    Lin, Yuanhua; Deng, Kuanhai; Sun, Yongxing; Zeng, Dezhi; Liu, Wanying; Kong, Xiangwei; Singh, Ambrish

    2014-01-01

    The internal pressure strength of tubing and casing often cannot satisfy the design requirements in high pressure, high temperature and high H2S gas wells. Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design. The ISO 10400: 2007 provides the model which can calculate the burst strength of tubing and casing better than API 5C3 standard, but the calculation accuracy is not desirable because about 50 percent predictive values are remarkably higher than real burst values. So, for the sake of improving strength design of tubing and casing, this paper deduces the plastic limit pressure of tubing and casing under internal pressure by applying the twin shear unified strength theory. According to the research of the influence rule of yield-to-tensile strength ratio and mechanical properties on the burst strength of tubing and casing, the more precise calculation model of tubing-casing's burst strength has been established with material hardening and intermediate principal stress. Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models. The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.

  20. Statistical Analysis Of Failure Strength Of Material Using Weibull Distribution

    International Nuclear Information System (INIS)

    Entin Hartini; Mike Susmikanti; Antonius Sitompul

    2008-01-01

    In evaluation of ceramic and glass materials strength a statistical approach is necessary Strength of ceramic and glass depend on its measure and size distribution of flaws in these material. The distribution of strength for ductile material is narrow and close to a Gaussian distribution while strength of brittle materials as ceramic and glass following Weibull distribution. The Weibull distribution is an indicator of the failure of material strength resulting from a distribution of flaw size. In this paper, cumulative probability of material strength to failure probability, cumulative probability of failure versus fracture stress and cumulative probability of reliability of material were calculated. Statistical criteria calculation supporting strength analysis of Silicon Nitride material were done utilizing MATLAB. (author)