The Pneumatic Actuators As Vertical Dynamic Load Simulators On Medium Weighted Wheel Suspension Mechanism

Science.gov (United States)

Ka'ka, Simon; Himran, Syukri; Renreng, Ilyas; Sutresman, Onny

2018-02-01

Almost all of road damage can be caused by dynamic loads of vehicles that fluctuate according to the type of vehicle that passes through. This study aims to calculate the vertical dynamic load of the vehicle actually occurs on road construction by the mechanism of vehicle wheel suspension. Pneumatic cylinders driven by pressurized air directly load the spring and shock absorber installed on the wheels of the vehicle. The load fluctuations of the medium weight categorized vehicles are determined by the regulation of the amount of pressurized air that enters into the pneumatic cylinder chamber, pushing the piston and connecting rods. The displacement that occurs during compression on the spring and shock absorber, is substituted into the equation of vehicle dynamic load while taking into account the spring stiffness constant, and the fluid or damper gas coefficient. The results show that the magnitude of the displacement when the compression force works has significant influences to the amount of vertical dynamic load of the vehicle that overlies the road construction. The presence of dynamic load of vehicles that fluctuates and repeats, also affects on the reduction of road ability to receive the load. Experimental results using pneumatic actuators instead of real dynamic vehicle loads illustrate the characteristics of the relationship between work pressure and dynamic load. If the working pressure of P2 (bar) is greater, the vertical dynamic load Ft (N) that overloads the road structure is also greater. The associate graphs show that the shock absorber has a greater ability to reduce dynamic load vertically that burden the road structure when compared with the ability of screw spring.

Effect of loading rate on dynamic fracture of reaction bonded silicon nitride

Science.gov (United States)

Liaw, B. M.; Kobayashi, A. S.; Emery, A. F.

1986-01-01

Wedge-loaded, modified tapered double cantilever beam (WL-MTDCB) specimens under impact loading were used to determine the room temperature dynamic fracture response of reaction bonded silicon nitride (RBSN). The crack extension history, with the exception of the terminal phase, was similar to that obtained under static loading. Like its static counterpart, a distinct crack acceleration phase, which was not observed in dynamic fracture of steel and brittle polymers, was noted. Unlike its static counterpart, the crack continued to propagate at nearly its terminal velocity under a low dynamic stress intensity factor during the terminal phase of crack propagation. These and previously obtained results for glass and RBSN show that dynamic crack arrest under a positive dynamic stress intensity factor is unlikely in static and impact loaded structural ceramics.

Effects of static pre-loading on the dynamic stability of a column on ...

African Journals Online (AJOL)

This paper presents, from strictly analytical consideration, the dynamic analysis of a finite column stressed by a step load but in the presence of a previously imposed static load. The results show that (a) the dynamic buckling load for this type of loading is relatively higher than that of a similar column stressed by a step load ...

Behavior of Brittle Materials Under Dynamic Loading

National Research Council Canada - National Science Library

Kanel, G

2000-01-01

Dynamic loading of brittle materials is related to many applications, including explosive excavation of rocks, design of ceramic armor, meteor impact on spacecraft windows, particle damage to turbine blades, etc...

Current scaling of axially radiated power in dynamic hohlraums and dynamic hohlraum load design for ZR

International Nuclear Information System (INIS)

Mock, Raymond Cecil; Nash, Thomas J.; Sanford, Thomas W. L.

2007-01-01

We present designs for dynamic hohlraum z-pinch loads on the 28 MA, 140 ns driver ZR. The scaling of axially radiated power with current in dynamic hohlraums is reviewed. With adequate stability on ZR this scaling indicates that 30 TW of axially radiated power should be possible. The performance of the dynamic hohlraum load on the 20 MA, 100 ns driver Z is extensively reviewed. The baseline z-pinch load on Z is a nested tungsten wire array imploding onto on-axis foam. Data from a variety of x-ray diagnostics fielded on Z are presented. These diagnostics include x-ray diodes, bolometers, fast x-ray imaging cameras, and crystal spectrometers. Analysis of these data indicates that the peak dynamic radiation temperature on Z is between 250 and 300 eV from a diameter less than 1 mm. Radiation from the dynamic hohlraum itself or from a radiatively driven pellet within the dynamic hohlraum has been used to probe a variety of matter associated with the dynamic hohlraum: the tungsten z-pinch itself, tungsten sliding across the end-on apertures, a titanium foil over the end aperture, and a silicon aerogel end cap. Data showing the existence of asymmetry in radiation emanating from the two ends of the dynamic hohlraum is presented, along with data showing load configurations that mitigate this asymmetry. 1D simulations of the dynamic hohlraum implosion are presented and compared to experimental data. The simulations provide insight into the dynamic hohlraum behavior but are not necessarily a reliable design tool because of the inherently 3D behavior of the imploding nested tungsten wire arrays

Dynamic intelligent cleaning model of dirty electric load data

International Nuclear Information System (INIS)

Zhang Xiaoxing; Sun Caixin

2008-01-01

There are a number of dirty data in the load database derived from the supervisory control and data acquisition (SCADA) system. Thus, the data must be carefully and reasonably adjusted before it is used for electric load forecasting or power system analysis. This paper proposes a dynamic and intelligent data cleaning model based on data mining theory. Firstly, on the basis of fuzzy soft clustering, the Kohonen clustering network is improved to fulfill the parallel calculation of fuzzy c-means soft clustering. Then, the proposed dynamic algorithm can automatically find the new clustering center (the characteristic curve of the data) with the updated sample data; At last, it is composed with radial basis function neural network (RBFNN), and then, an intelligent adjusting model is proposed to identify the dirty data. The rapid and dynamic performance of the model makes it suitable for real time calculation, and the efficiency and accuracy of the model is proved by test results of electrical load data analysis in Chongqing

Material properties under intensive dynamic loading

CERN Document Server

Cherne, Frank J; Zhernokletov, Mikhail V; Glushak, B L; Zocher, Marvin A

2007-01-01

Understanding the physical and thermomechanical response of materials subjected to intensive dynamic loading is a challenge of great significance in engineering today. This volume assumes the task of gathering both experimental and diagnostic methods in one place, since not much information has been previously disseminated in the scientific literature.

Numerical evaluation of cracked pipes under dynamic loading

International Nuclear Information System (INIS)

Petit, M.; Jamet, P.

1989-01-01

In order to apply the leak-before-break concept to piping systems, the behavior of cracked pipes under dynamic, and especially seismic, loadings must be studied. A simple finite element model of a cracked pipe has been developed and implemented in the general purpose computer code CASTEM 2000. The model is a generalization of the approach proposed by Paris and Tada (1). Considered loads are bending moment and axial force (representing thermal expansion and internal pressure.) The elastic characteristics of the model are determined using the Zahoor formulae for the geometry-dependent factors. Owing to the material behabior plasticity must be taken into account. To represent the crack growth, the material is defined by two characteristic values: J 1c which is the level of energy corresponding to crack initiation and the tearing modulus, T, which governs the length of propagation of the crack. For dynamic loads, unilateral conditions are imposed to represent crack closure. The model has been used for the design of dynamic tests to be conducted on shaking tables. Test principle is briefly described and numerical results are presented. Finally evaluation of margin, due to plasticity, in comparison with the standard design procedure is made

Dynamical prediction and pattern mapping in short-term load forecasting

Energy Technology Data Exchange (ETDEWEB)

Aguirre, Luis Antonio; Rodrigues, Daniela D.; Lima, Silvio T. [Departamento de Engenharia Eletronica, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, 31270-901 Belo Horizonte, MG (Brazil); Martinez, Carlos Barreira [Departamento de Engenharia Hidraulica e Recursos Hidricos, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, 31270-901 Belo Horizonte, MG (Brazil)

2008-01-15

This work will not put forward yet another scheme for short-term load forecasting but rather will provide evidences that may improve our understanding about fundamental issues which underlay load forecasting problems. In particular, load forecasting will be decomposed into two main problems, namely dynamical prediction and pattern mapping. It is argued that whereas the latter is essentially static and becomes nonlinear when weekly features in the data are taken into account, the former might not be deterministic at all. In such cases there is no determinism (serial correlations) in the data apart from the average cycle and the best a model can do is to perform pattern mapping. Moreover, when there is determinism in addition to the average cycle, the underlying dynamics are sometimes linear, in which case there is no need to resort to nonlinear models to perform dynamical prediction. Such conclusions were confirmed using real load data and surrogate data analysis. In a sense, the paper details and organizes some general beliefs found in the literature on load forecasting. This sheds some light on real model-building and forecasting problems and helps understand some apparently conflicting results reported in the literature. (author)

Decrease of dynamic loads in mobile energy means

Science.gov (United States)

Polivaev, O. I.; Gorban, L. K.; Vorohobin, A. V.; Vedrinsky, O. S.

2018-03-01

The increase in the productivity of machine and tractor units is possible due to the increase in operating speeds, this leads to the emergence of increased dynamic loads in the system “engine-transmission-propulsion unit-soil”, which worsens the performance of machine-tractor aggregates. To reduce fluctuations in the “engine-transmission” system, special vibration dampers are used, which installed in close proximity to the engine and protect well the transmission from uneven engine operation; however, such dampers practically do not eliminate the oscillations of external loads. Reducing dynamic loads on the transmission and the mobile power engine (MPE) is an important issue directly related to improving the performance, reliability and durability of the tractor, as well as reducing the slippage of the drive wheels. In order to reduce effectively dynamic loads on the transmission and on the MPE, it is necessary to introduce resilient damping elements closer to the sources of oscillations, namely, to the driving wheels. At the same time, the elastic-damping element should provide accumulation of vibration energy caused by external influences and have a large energy capacity. The installation of an elastic-damping element in the final link of the tractor transmission ensures a reduction in the magnitude of external influences, thereby protecting the engine and transmission from large dynamic loads, and allows one to reduce the slippage of the propellers, which has a positive effect on the traction and energy characteristics of the tractor. Traction tests of the LTP-55 tractor on a concrete road showed that the use of an elasto-damping drive makes it possible to increase the maximum tractive power from 33.5 to 35.3 kW and to reduce the slipping of propellers by 12-30%, the specific fuel consumption by 6-10%. When driving on stubble, the use of an elastic-damping drive increases the maximum tractive power from 25 to 26 kW, reduces the skidding of propellers by

Design of dynamic loading support on high temperature pipe

International Nuclear Information System (INIS)

Sitandung, Y.B.; Bandriyana, B.

2002-01-01

As a follow up to pipe stress analysis result caused by high temperature operation loading, a design of dynamic loading support was made. The type of variable and constant support as acceptable choosing are applicated for reduce of over stress and over load on piping system. Analysis line schedule of AP600 as an example with apply three dynamic loading support (two type variable and one type constant support). The pre-design of the third support above are based on analysis result with follow the support catalog and field condition wherein its supports are installed. To guarantee the performance and accurate of the support, checking is performed for spring working rate tolerance, support variability and swing angle. The design results of variable spring are loads, size, working rate, type tolerance, spring rate, variability, long and sway angle with each values 5000; 15; 1,25; VM; 0.655; 1080; 0.114; 114,5; 0,48 for S1 and 2045; 12; 0,583; VS; 0,237; 900; 0,132; 130; 0,34 for S3

Characterization of dynamic loads on the LMFBR rotating shield

International Nuclear Information System (INIS)

Morris, E.

1979-01-01

The rotating shields structure is a potential weak point of some current designs of primary containment against postulated whole core explosions. The calculation of the effect of transient loads on this structure, resulting from such an explosion, is therefore important in developing a safety case. The transient loads are usually calculated by computer codes such as ASTARTE, SEURBNUK, REXCO or ICECO and the effect of these loads on the structure by a suitable finite element code. Such procedure can be lengthly and costly. The present paper proposed a procedure which allows the consequences of changes in the transient loads, resulting from design changes for example, to be quickly and simply gauged. The load-impulse method of characterizing dynamic response of a structural system is well established. Provided loads with a similar temporal variation are compared, it can be shown that the dynamic response depends on only two features of the load, an average load and a time intregrated load or impulse. The scope of this approach has been extended by Youngdahl who has shown, for structures which deform in a rigid-plastic manner, that complex laoding histories can be equated to a rectangular form of loading, in a precise manner for simple structures and in an approximate manner for more complicated structures. This paper proposes that the failure characteristics of the rotating shields for which extensive plastic deformation is involved, be calculated for rectangular type loadings. The complex transient loadings calculated for various explosions and various changes in the primary vessel design can then be reduced to an equivalent rectangular form and the consequencial response of the shields structure deduced. (orig.)

Features wear nodes mechanization wing aircraft operating under dynamic loads

Directory of Open Access Journals (Sweden)

А.М. Хімко

2009-03-01

Full Text Available  The conducted researches of titanic alloy ВТ-22 at dynamic loading with cycled sliding and dynamic loading in conditions of rolling with slipping. It is established that roller jamming in the carriage increases wear of rod of mechanization of a wing to twenty times. The optimum covering for strengthening wearied sites and restoration of working surfaces of wing’s mechanization rod is defined.

A STUDY ON DYNAMIC LOAD HISTORY RECONSTRUCTION USING PSEUDO-INVERSE METHODS

OpenAIRE

Santos, Ariane Rebelato Silva dos; Marczak, Rogério José

2017-01-01

Considering that the vibratory forces generally cannot be measured directly at the interface of two bodies, an inverse method is studied in the present work to recover the load history in such cases. The proposed technique attempts to reconstruct the dynamic loads history by using a frequency domain analysis and Moore-Penrose pseudo-inverses of the frequency response function (FRF) of the system. The methodology consists in applying discrete dynamic loads on a finite element model in the time...

A Dynamic Model for Load Balancing in Cloud Infrastructure

Directory of Open Access Journals (Sweden)

Jitendra Bhagwandas Bhatia

2015-08-01

Full Text Available This paper analysis various challenges faced in optimizing computing resource utilization via load balancing and presents a platform-independent model for load balancing which targets high availability of resources, low SLA (Service Level agreement violations and saves power. To achieve this, incoming requests are monitored for sudden burst, a prediction model is employed to maintain high availability and a power-aware algorithm is applied for choosing a suitable physical node for a virtual host. The proposed dynamic load balancing model provides a way to conflicting goals of saving power and maintaining high resource availability.For anyone building a private, public or hybrid IaaS cloud infrastructure, load balancing of virtual hosts on a limited number of physical nodes, becomes a crucial aspect. This paper analysis various challenges faced in optimizing computing resource utilization via load balancing and presents a platform independent model for load balancing which targets high availability of resources, low SLA (Service Level agreement violations and saves power. To achieve this, incoming requests are monitored for sudden burst, prediction model is employed to maintain high availability and power aware algorithm is applied for choosing a suitable physical node for virtual host. The proposed dynamic load balancing model provides a way to conflicting goals of saving power and maintaining high resource availability.

Loading dynamics of a sliding DNA clamp.

KAUST Repository

Cho, Won-Ki; Jergic, Slobodan; Kim, Daehyung; Dixon, Nicholas E; Lee, Jong-Bong

2014-01-01

8° during clamp closure. The single-molecule polarization and FRET studies thus revealed the real-time dynamics of the ATP-hydrolysis-dependent 3D conformational change of the β clamp during loading at a ss/dsDNA junction.

Analysis of pile foundations under dynamic loads

International Nuclear Information System (INIS)

Waas, G.; Hartmann, H.G.

1981-01-01

A method is presented for the analysis of pile foundations which are subjected to horizontal dynamic loads from earthquakes, airplane impact, gas explosion or other sources. The motion of the pile cap and the pile forces are computed. - The loads may be applied to the pile cap or directly to the piles (e.g. by earthquake wave motion). The soil may be stratified and is considered to be an elastic or visco-elastic medium. The piles are assumed vertical. The method makes use of an approximate fundamental solution for displacements caused by a dynamic point load in a layered visco-elastic medium. The approximation involves a discretization of the medium in the vertical direction. In horizontal directions the medium is treated by continuum theory. The soil medium supports each pile at about 10 to 20 nodes. A dynamic flexiblity matrix for the soil is derived which relates the elastic, damping and inertial forces of the soil to the displacements at each node. It includes effects of radiation damping. All piles are coupled through the soil flexibility matrix. The piles are modelled by beam elements. Transient response is computed using fast discrete Fourier transforms. The arrangement of the piles is arbitrary. However, simple and double symmetry can be accounted for by the computer program. When the pile arrangement is axisymmetric, the degrees of freedom can be reduced to only those of two piles per ring. The influence of the number of piles and the influence of the pile spacing on group stiffness and on pile forces is presented for two soil profiles. Dynamic effects on pile forces of a foundation for a reactor building are studied. They are significant when soils are soft. (orig.)

Effects of moving dynamic tyre loads on tyre-pavement contact stresses

CSIR Research Space (South Africa)

Steyn, WJvdM

2002-01-01

Full Text Available The purpose of this paper is to indicate the effect that moving dynamic tyre loads has on the tyre-pavement contact stresses used in pavement analysis. Traditionally tyre loads (in pavement analysis) are modelled as constant loads applied through...

DYNAMIC TIME HISTORY ANALYSIS OF BLAST RESISTANT DOOR USING BLAST LOAD MODELED AS IMPACT LOAD

Directory of Open Access Journals (Sweden)

Y. A. Pranata

2012-06-01

Full Text Available A blast resistant single door was designed to withstand a 0.91 bar blast pressure and 44 ms blast duration. The analysis was done using Dynamic Time History Analysis using Blast Load modeled as Impact Load for given duration. The material properties used have been modified to accommodate dynamic effects. The analysis was done using dynamic finite element method (fem for time of the blast duration, and the maximum/minimum internal forces and displacement were taken from the time history output, in order to know the behavior under blast load and estimate the safety margin of the door. Results obtained from this research indicated that the maximum z-displacement is 1.709 mm, while in the term of serviceability, the permitted is 25 mm. The maximum reaction force is 73,960 N, while the maximum anchor capacity is 82,069 N. On blast condition, the maximum frame stress is 71.71 MPa, the maximum hinge shear stress is 45.28 MPa. While on rebound condition, the maximum frame stress is 172.11 MPa, the maximum hinge shear stress is 29.46 MPa. The maximum door edge rotation is 0.44 degree, which is not exceed the permitted boundary (1.2 degree. Keywords: Dynamic time history, blast resistant door, single door, finite element method.

Dynamic analysis of solid propellant grains subjected to ignition pressurization loading

Science.gov (United States)

Chyuan, Shiang-Woei

2003-11-01

Traditionally, the transient analysis of solid propellant grains subjected to ignition pressurization loading was not considered, and quasi-elastic-static analysis was widely adopted for structural integrity because the analytical task gets simplified. But it does not mean that the dynamic effect is not useful and could be neglected arbitrarily, and this effect usually plays a very important role for some critical design. In order to simulate the dynamic response for solid rocket motor, a transient finite element model, accompanied by concepts of time-temperature shift principle, reduced integration and thermorheologically simple material assumption, was used. For studying the dynamic response, diverse ignition pressurization loading cases were used and investigated in the present paper. Results show that the dynamic effect is important for structural integrity of solid propellant grains under ignition pressurization loading. Comparing the effective stress of transient analysis and of quasi-elastic-static analysis, one can see that there is an obvious difference between them because of the dynamic effect. From the work of quasi-elastic-static and transient analyses, the dynamic analysis highlighted several areas of interest and a more accurate and reasonable result could be obtained for the engineer.

Mechanical behavior of ultrafine-grained materials under combined static and dynamic loadings

Directory of Open Access Journals (Sweden)

Guo Y.Z.

2015-01-01

Full Text Available Ultrafine-grained (UFG materials have extensive prospects for engineering application due to their excellent mechanical properties. However, the grain size decrease reduces their strain hardening ability and makes UFG materials more susceptible to deformation instability such as shear localization. In most cases, critical shear strain is taken as the criterion for formation of shear localization under impact loading or adiabatic shear band (ASB. Recently, some researchers found that the formation of ASB was determined only by the dynamic loading process and had nothing to do with its static loading history. They proposed for coarse-grained metals a dynamic stored energy-based criterion for ASB and verified it by some experiments. In this study, we will focus on the shear localization behavior of UFG metals such as UFG titanium and magnesium alloy AZ31. Quasi-static loading and dynamic loading will be applied on the same specimen alternately. The shear localization behavior will be analyzed and the criterion of its formation will be evaluated.

Feasibility of Applying Controllable Lubrication to Dynamically Loaded Journal Bearings

DEFF Research Database (Denmark)

Estupinan, Edgar Alberto; Santos, Ilmar

2009-01-01

A multibody dynamic model of the main mechanical components of a hermetic reciprocating compressor is presented in this work. Considering that some of the mechanical elements are interconnected via thin fluid films, the multibody dynamic model is coupled to the equations from the dynamics...... of the fluid films, based on fluid film theory. For a dynamically loaded journal bearing, the fluid film pressure distribution can be computed by numerically solving the Reynolds equation, by means of finite-difference method. Particularly, in this study the main focus is on the lubrication behavior...... and reaction forces in a reciprocating compressor have a cyclic behavior, periodic oil pressure injection rules based on the instantaneous crank angle and load bearing condition can be established. In this paper, several bearing configurations working under different oil pressure injection rules conditions...

Dynamic Loading of Carrara Marble in a Heated State

Science.gov (United States)

Wong, Louis Ngai Yuen; Li, Zhihuan; Kang, Hyeong Min; Teh, Cee Ing

2017-06-01

Useable land is a finite space, and with a growing global population, countries have been exploring the use of underground space as a strategic resource to sustain the growth of their society and economy. However, the effects of impact loading on rocks that have been heated, and hence the integrity of the underground structure, are still not fully understood and has not been included in current design standards. Such scenarios include traffic accidents and explosions during an underground fire. This study aims to provide a better understanding of the dynamic load capacity of Carrara marble at elevated temperatures. Dynamic uniaxial compression tests are performed on Carrara marble held at various temperatures using a split-Hopkinson Pressure Bar (SHPB) setup with varying input force. A customized oven is included in the SHPB setup to allow for testing of the marble specimens in a heated state. After the loading test, a three-wave analysis is performed to obtain the dynamic stress-strain curve of the specimen under loading. The fragments of the failed specimens were also collected and dry-sieved to obtain the particle size distribution. The results reveal that the peak stress of specimens that have been heated is negatively correlated with the heating temperature. However, the energy absorbed by the specimens at peak stress at all temperatures is similar, indicating that a significant amount of energy is dissipated via plastic deformation. Generally, fragment size is also found to show a negative correlation with heating temperature and loading pressure. However, in some cases this relationship does not hold true, probably due to the occurrence of stress shadowing. Linear Elastic Fracture Mechanics has been found to be generally applicable to specimens tested at low temperatures; but at higher temperatures, Elastic-Plastic Fracture Mechanics will give a more accurate prediction. Another contribution of this study is to show that other than the peak stress of the

Dynamic Response and Failure Mechanism of Brittle Rocks Under Combined Compression-Shear Loading Experiments

Science.gov (United States)

Xu, Yuan; Dai, Feng

2018-03-01

A novel method is developed for characterizing the mechanical response and failure mechanism of brittle rocks under dynamic compression-shear loading: an inclined cylinder specimen using a modified split Hopkinson pressure bar (SHPB) system. With the specimen axis inclining to the loading direction of SHPB, a shear component can be introduced into the specimen. Both static and dynamic experiments are conducted on sandstone specimens. Given carefully pulse shaping, the dynamic equilibrium of the inclined specimens can be satisfied, and thus the quasi-static data reduction is employed. The normal and shear stress-strain relationships of specimens are subsequently established. The progressive failure process of the specimen illustrated via high-speed photographs manifests a mixed failure mode accommodating both the shear-dominated failure and the localized tensile damage. The elastic and shear moduli exhibit certain loading-path dependence under quasi-static loading but loading-path insensitivity under high loading rates. Loading rate dependence is evidently demonstrated through the failure characteristics involving fragmentation, compression and shear strength and failure surfaces based on Drucker-Prager criterion. Our proposed method is convenient and reliable to study the dynamic response and failure mechanism of rocks under combined compression-shear loading.

Dynamic Load Balancing for PIC code using Eulerian/Lagrangian partitioning

OpenAIRE

Sauget, Marc; Latu, Guillaume

2017-01-01

This document presents an analysis of different load balance strategies for a Plasma physics code that models high energy particle beams with PIC method. A comparison of different load balancing algorithms is given: static or dynamic ones. Lagrangian and Eulerian partitioning techniques have been investigated.

The Effect of the Loading on Dynamic Stability and Scapular Asymmetry

Directory of Open Access Journals (Sweden)

Mohammad Hassan Azarsa

2014-03-01

Full Text Available Background: Scapular stabilization and neuromuscular control provide an important parameter to characterize shoulder function during dynamic activities. Many studies have confirmed the effect of the loading on scapular position and scapulohumeral rhythm. Therefore, the evaluation of stabilizer muscles involvement in scapular asymmetry may assist in the development of clinical examination and rehabilitation program. The aim of this study was to evaluate the effect of loading on dynamic stability and scapular asymmetry in basketball players. Methods: Thirty healthy male basketball players aged between 20 to 31 years old were tested. The linear distance between scapular inferior angle and T7 spinous process was measured using a caliper in 90 degrees of unloaded scaption and with 1, 2 and 4 kg loading. The difference of distances of two sides in the above 4 positions was analyzed. Results: The amount of distances difference in two sides with 1 kg loading was minimal (9.36 mm. This difference increased to 10.19 mm and 12.22 mm, with increasing the loading to 2 and 4 kg respectively; although the 4 positions of the test did not show significant differences in distances difference (P>0.05. Conclusion: This study shows that dynamic stability of the scapula is dependent on the role of muscles, so that with increasing load on the muscles, the scapular asymmetry is more pronounced.

Using Gait Dynamics to Estimate Load from a Body-Worn Accelerometer

Science.gov (United States)

2016-02-05

dynamics, ambulation, correlation structure, musculoskeletal injury I. INTRODUCTION ilitary personnel commonly engage in training and operational...according to their load estimation accuracy, which is defined by the Pearson correlation , r, of its load estimates with the true loads (see Tables...method. In Table IV are shown the mean absolute error, MAE, and Pearson correlation , r, of the load estimates using estimates from GS alone, PLS alone

Dynamic analysis of a pumped-storage hydropower plant with random power load

Science.gov (United States)

Zhang, Hao; Chen, Diyi; Xu, Beibei; Patelli, Edoardo; Tolo, Silvia

2018-02-01

This paper analyzes the dynamic response of a pumped-storage hydropower plant in generating mode. Considering the elastic water column effects in the penstock, a linearized reduced order dynamic model of the pumped-storage hydropower plant is used in this paper. As the power load is always random, a set of random generator electric power output is introduced to research the dynamic behaviors of the pumped-storage hydropower plant. Then, the influences of the PI gains on the dynamic characteristics of the pumped-storage hydropower plant with the random power load are analyzed. In addition, the effects of initial power load and PI parameters on the stability of the pumped-storage hydropower plant are studied in depth. All of the above results will provide theoretical guidance for the study and analysis of the pumped-storage hydropower plant.

Loading Processes Dynamics Modelling Taking into Account the Bucket-Soil Interaction

Directory of Open Access Journals (Sweden)

Carmen Debeleac

2007-10-01

Full Text Available The author propose three dynamic models specialized for the vibrations and resistive forces analysis that appear at the loading process with different construction equipment like frontal loaders and excavators.The models used putting into evidence the components of digging: penetration, cutting, and loading.The conclusions of this study consist by evidentiate the dynamic overloads that appear on the working state and that induced the self-oscillations into the equipment structure.

Effect of dynamic monotonic and cyclic loading on fracture behavior for Japanese carbon steel pipe STS410

Energy Technology Data Exchange (ETDEWEB)

Kinoshita, Kanji; Murayama, Kouichi; Ogata, Hiroyuki [and others

1997-04-01

The fracture behavior for Japanese carbon steel pipe STS410 was examined under dynamic monotonic and cyclic loading through a research program of International Piping Integrity Research Group (EPIRG-2), in order to evaluate the strength of pipe during the seismic event The tensile test and the fracture toughness test were conducted for base metal and TIG weld metal. Three base metal pipe specimens, 1,500mm in length and 6-inch diameter sch.120, were employed for a quasi-static monotonic, a dynamic monotonic and a dynamic cyclic loading pipe fracture tests. One weld joint pipe specimen was also employed for a dynamic cyclic loading test In the dynamic cyclic loading test, the displacement was controlled as applying the fully reversed load (R=-1). The pipe specimens with a circumferential through-wall crack were subjected four point bending load at 300C in air. Japanese STS410 carbon steel pipe material was found to have high toughness under dynamic loading condition through the CT fracture toughness test. As the results of pipe fracture tests, the maximum moment to pipe fracture under dynamic monotonic and cyclic loading condition, could be estimated by plastic collapse criterion and the effect of dynamic monotonic loading and cyclic loading was a little on the maximum moment to pipe fracture of the STS410 carbon steel pipe. The STS410 carbon steel pipe seemed to be less sensitive to dynamic and cyclic loading effects than the A106Gr.B carbon steel pipe evaluated in IPIRG-1 program.

Effect of dynamic monotonic and cyclic loading on fracture behavior for Japanese carbon steel pipe STS410

International Nuclear Information System (INIS)

Kinoshita, Kanji; Murayama, Kouichi; Ogata, Hiroyuki

1997-01-01

The fracture behavior for Japanese carbon steel pipe STS410 was examined under dynamic monotonic and cyclic loading through a research program of International Piping Integrity Research Group (EPIRG-2), in order to evaluate the strength of pipe during the seismic event The tensile test and the fracture toughness test were conducted for base metal and TIG weld metal. Three base metal pipe specimens, 1,500mm in length and 6-inch diameter sch.120, were employed for a quasi-static monotonic, a dynamic monotonic and a dynamic cyclic loading pipe fracture tests. One weld joint pipe specimen was also employed for a dynamic cyclic loading test In the dynamic cyclic loading test, the displacement was controlled as applying the fully reversed load (R=-1). The pipe specimens with a circumferential through-wall crack were subjected four point bending load at 300C in air. Japanese STS410 carbon steel pipe material was found to have high toughness under dynamic loading condition through the CT fracture toughness test. As the results of pipe fracture tests, the maximum moment to pipe fracture under dynamic monotonic and cyclic loading condition, could be estimated by plastic collapse criterion and the effect of dynamic monotonic loading and cyclic loading was a little on the maximum moment to pipe fracture of the STS410 carbon steel pipe. The STS410 carbon steel pipe seemed to be less sensitive to dynamic and cyclic loading effects than the A106Gr.B carbon steel pipe evaluated in IPIRG-1 program

The dynamic behavior of mortar under impact-loading

Science.gov (United States)

Kawai, Nobuaki; Inoue, Kenji; Misawa, Satoshi; Tanaka, Kyoji; Hayashi, Shizuo; Kondo, Ken-Ichi; Riedel, Werner

2007-06-01

Concrete and mortar are the most fundamental structural material. Therefore, considerable interest in characterizing the dynamic behavior of them under impact-loading exists. In this study, plate impact experiments have been performed to determine the dynamic behavior of mortar. Longitudinal and lateral stresses have been directly measured by means of embedded polyvinylidene fluoride (PVDF) gauges up to 1 GPa. A 200 mm-cal. powder gun enable us to measure longitudinal and lateral stresses at several point from the impact surface, simultaneously. The shear strength under impact-loading has been obtained from measured longitudinal and lateral stresses. The longitudinal stress profile shows a two-wave structure. It is indicated that this structure is associated with the onset of pore compaction and failure of mortar by comparing with hydrocode simulations using an elastic-plastic damage model for concrete.

Dynamic fracture initiation in brittle materials under combined mode I/II loading

International Nuclear Information System (INIS)

Nakano, M.; Kishida, K.; Yamauchi, Y.; Sogabe, Y.

1994-01-01

A new test method has been developed to measure the resistance of dynamic fracture initiation in brittle materials under combined mode I/II loadings. The Brazilian disks with center-cracks have been fractured under oblique impact loadings in diametral-compression. The dynamic stress intensity factors of mode I and II are evaluated from the superposition integrals of the step response functions for the cracked disk. The experimental results are presented to elucidate the influence of loading rate on the combined mode fracture toughness for ceramics and glasses. (orig.)

Shaft Center Orbit in Dynamically Loaded Bearings

DEFF Research Database (Denmark)

Klit, Peder

2005-01-01

The aim of this work is to demonstrate how to utilize the bearings damping coe±cients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 [1]and described further in 1972 [2]. Several authors have re¯ned this metho...

Applicability of laboratory data to large scale tests under dynamic loading conditions

International Nuclear Information System (INIS)

Kussmaul, K.; Klenk, A.

1993-01-01

The analysis of dynamic loading and subsequent fracture must be based on reliable data for loading and deformation history. This paper describes an investigation to examine the applicability of parameters which are determined by means of small-scale laboratory tests to large-scale tests. The following steps were carried out: (1) Determination of crack initiation by means of strain gauges applied in the crack tip field of compact tension specimens. (2) Determination of dynamic crack resistance curves of CT-specimens using a modified key-curve technique. The key curves are determined by dynamic finite element analyses. (3) Determination of strain-rate-dependent stress-strain relationships for the finite element simulation of small-scale and large-scale tests. (4) Analysis of the loading history for small-scale tests with the aid of experimental data and finite element calculations. (5) Testing of dynamically loaded tensile specimens taken as strips from ferritic steel pipes with a thickness of 13 mm resp. 18 mm. The strips contained slits and surface cracks. (6) Fracture mechanics analyses of the above mentioned tests and of wide plate tests. The wide plates (960x608x40 mm 3 ) had been tested in a propellant-driven 12 MN dynamic testing facility. For calculating the fracture mechanics parameters of both tests, a dynamic finite element simulation considering the dynamic material behaviour was employed. The finite element analyses showed a good agreement with the simulated tests. This prerequisite allowed to gain critical J-integral values. Generally the results of the large-scale tests were conservative. 19 refs., 20 figs., 4 tabs

Dynamic Loads and Wake Prediction for Large Wind Turbines Based on Free Wake Method

Institute of Scientific and Technical Information of China (English)

Cao Jiufa; Wang Tongguang; Long Hui; Ke Shitang; Xu Bofeng

2015-01-01

With large scale wind turbines ,the issue of aerodynamic elastic response is even more significant on dy-namic behaviour of the system .Unsteady free vortex wake method is proposed to calculate the shape of wake and aerodynamic load .Considering the effect of aerodynamic load ,inertial load and gravity load ,the decoupling dy-namic equations are established by using finite element method in conjunction of the modal method and equations are solved numerically by Newmark approach .Finally ,the numerical simulation of a large scale wind turbine is performed through coupling the free vortex wake modelling with structural modelling .The results show that this coupling model can predict the flexible wind turbine dynamic characteristics effectively and efficiently .Under the influence of the gravitational force ,the dynamic response of flapwise direction contributes to the dynamic behavior of edgewise direction under the operational condition of steady wind speed .The difference in dynamic response be-tween the flexible and rigid wind turbines manifests when the aerodynamics/structure coupling effect is of signifi-cance in both wind turbine design and performance calculation .

Dynamic Aftershock Triggering Correlated with Cyclic Loading in the Slip Direction

Science.gov (United States)

Hardebeck, J.

2014-12-01

Dynamic stress changes have been shown to contribute to aftershock triggering, but the physical triggering mechanisms are not fully understood. Some proposed mechanisms are based on dynamic stress loading of the target fault in a direction that encourages earthquake slip (e.g. dynamic Coulomb stress triggering), while other mechanisms are based on fault weakening due to shaking. If dynamic stress loading in the fault slip direction plays a role in aftershock triggering, we would expect to see a relationship between the dynamic stress orientations and the aftershock focal mechanisms. Alternatively, if dynamic stress change triggering functions only through a fault weakening mechanism that is independent of the slip direction of the target fault, no such relationship is expected. I study aftershock sequences of 4 M≥6.7 mainshocks in southern California, and find a small but significant relationship between modeled dynamic stress direction and aftershock focal mechanisms. The mainshock dynamic stress changes have two observed impacts: changing the focal mechanisms in a given location to favor those aligned with the dynamic stress change, and changing the spatial distribution of seismicity to favor locations where the dynamic stress change aligns with the background stress. The aftershock focal mechanisms are significantly more aligned with the dynamic stress changes than the preshock mechanisms for only the first 0.5-1 year following most mainshocks, although for at least 10 years following Hector Mine. Dynamic stress effects on focal mechanisms are best observed at long periods (30-60 sec). Dynamic stress effects are only observed when using metrics based on repeated stress cycling in the same direction, for example considering the dominant stress orientation over the full time series, and not for the peak dynamic stress. These results imply that dynamic aftershock triggering operates at least in part through cyclic loading in the direction of fault slip, although

Effect of Static-Dynamic Coupling Loading on Fracture Toughness and Failure Characteristics in Marble

Directory of Open Access Journals (Sweden)

Z. Q. Yin

2014-03-01

Full Text Available Fracture experiments in a notched semi-circular bend configuration were conducted to test the dynamic fracture toughness of a marble under static-dynamic coupling load using a modified split Hopkinson pressure bar. The fracture process of the specimen was monitored using a high speed (HS camera. Based on digital image correlation (DIC and strain gauges, the full-field strain fields and time-to-fracture of the marble were measured under static-dynamic coupling load. Experimental results show that dynamic fracture toughness was well determined, and the HS-DIC technique provides reliable full-field strain fields in the specimens under static-dynamic coupling loads. The failure characteristics of the marble under external impact were affected obviously by pre-compression stress. Increase of axial pre-compression stress was helpful to improve the crack propagation velocity, and dynamic crack initiation toughness was decreased.

Influence of the implant abutment types and the dynamic loading on initial screw loosening

Science.gov (United States)

Kim, Eun-Sook

2013-01-01

PURPOSE This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at 30° to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for 105 cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (α=0.05). RESULTS Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION The abutment types did not have a significant influence on short term screw loosening. On the other hand, after 105 cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not. PMID:23509006

Dynamical Model of Rocket Propellant Loading with Liquid Hydrogen

Data.gov (United States)

National Aeronautics and Space Administration — A dynamical model describing the multi-stage process of rocket propellant loading has been developed. It accounts for both the nominal and faulty regimes of...

Dynamic load balancing algorithm for molecular dynamics based on Voronoi cells domain decompositions

Energy Technology Data Exchange (ETDEWEB)

Fattebert, J.-L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Richards, D.F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Glosli, J.N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2012-12-01

We present a new algorithm for automatic parallel load balancing in classical molecular dynamics. It assumes a spatial domain decomposition of particles into Voronoi cells. It is a gradient method which attempts to minimize a cost function by displacing Voronoi sites associated with each processor/sub-domain along steepest descent directions. Excellent load balance has been obtained for quasi-2D and 3D practical applications, with up to 440·10⁶ particles on 65,536 MPI tasks.

Strength and behavior in shear of reinforced concrete deep beams under dynamic loading conditions

Energy Technology Data Exchange (ETDEWEB)

Adhikary, Satadru Das [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Li, Bing, E-mail: cbli@ntu.edu.sg [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Fujikake, Kazunori [Department of Civil and Environmental Engineering, National Defense Academy, Yokosuka 239 8686 (Japan)

2013-06-15

Highlights: ► Effects of wider range of loading rates on dynamic shear behavior of RC deep beams. ► Experimental investigation of RC deep beam with and without shear reinforcements. ► Verification of experimental results with truss model and FE simulation results. ► Empirical equations are proposed to predict the dynamic increase factor of maximum resistance. -- Abstract: Research on reinforced concrete (RC) deep beams has seen considerable headway over the past three decades; however, information on the dynamic shear strength and behavior of RC deep beams under varying rates of loads remains limited. This paper describes the experimental results of 24 RC deep beams with and without shear reinforcements under varying rates of concentrated loading. Results obtained serve as useful data on shear resistance, failure patterns and strain rates corresponding to varying loading rates. An analytical truss model approach proves its efficacy in predicting the dynamic shear resistance under varying loading rates. Furthermore, three-dimensional nonlinear finite element (FE) model is described and the simulation results are verified with the experimental results. A parametric study is then conducted to investigate the influence of longitudinal reinforcement ratio, transverse reinforcement ratio and shear span to effective depth ratio on shear behavior. Subsequently, two empirical equations were proposed by integrating the various parameters to assess the dynamic increase factor (DIF) of maximum resistance under varying rates of concentrated loading.

Dynamic Load Balanced Clustering using Elitism based Random Immigrant Genetic Approach for Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

K. Mohaideen Pitchai

2017-07-01

Full Text Available Wireless Sensor Network (WSN consists of a large number of small sensors with restricted energy. Prolonged network lifespan, scalability, node mobility and load balancing are important needs for several WSN applications. Clustering the sensor nodes is an efficient technique to reach these goals. WSN have the characteristics of topology dynamics because of factors like energy conservation and node movement that leads to Dynamic Load Balanced Clustering Problem (DLBCP. In this paper, Elitism based Random Immigrant Genetic Approach (ERIGA is proposed to solve DLBCP which adapts to topology dynamics. ERIGA uses the dynamic Genetic Algorithm (GA components for solving the DLBCP. The performance of load balanced clustering process is enhanced with the help of this dynamic GA. As a result, the ERIGA achieves to elect suitable cluster heads which balances the network load and increases the lifespan of the network.

Dynamic Axle Load of an Automotive Vehicle When Driven on a Mobile Measurement Platform

OpenAIRE

Jagiełowicz-Ryznar C.

2014-01-01

An analysis of the dynamic axle load of an automotive vehicle (AV) when it is driven on a mobile measurement platform is presented in this paper. During the ride, the time characteristic of the dynamic force N(t), acting on the axle, was recorded. The effect of the vehicle axle mass on the maximum dynamic force value and the dynamic coefficient were studied. On this basis it was attempted to calculate the total vehicle’s weight. Conclusions concerning the dynamic loads of the vehicle axles in...

Impact of the variation in dynamic vehicle load on flexible pavement responses

Science.gov (United States)

Ahsanuzzaman, Md

The purpose of this research was to evaluate the dynamic variation in asphalt pavement critical responses due to dynamic tire load variations. An attempt was also made to develop generalized regression equations to predict the dynamic response variation in flexible pavement under various dynamic load conditions. The study used an extensive database of computed pavement response histories for five different types of sites (smooth, rough, medium rough, very rough and severely rough), two different asphalt pavement structures (thin and thick) at two temperatures (70 °F and 104 °F), subjected to a tandem axle dual tire at three speeds 25, 37 and 50 mph (40, 60 and 80 km/h). All pavement responses were determined using the 3D-Move Analysis program (Version 1.2) developed by University of Nevada, Reno. A new term called Dynamic Response Coefficient (DRC) was introduced in this study to address the variation in critical pavement responses due to dynamic loads as traditionally measured by the Dynamic Load Coefficient (DLC). While DLC represents the additional varying component of the tire load, DRC represents the additional varying component of the response value (standard deviation divided by mean response). In this study, DRC was compared with DLC for five different sites based on the roughness condition of the sites. Previous studies showed that DLC varies with vehicle speed and suspension types, and assumes a constant value for the whole pavement structure (lateral and vertical directions). On the other hand, in this study, DRC was found to be significantly varied with the asphalt pavement and function of pavement structure, road roughness conditions, temperatures, vehicle speeds, suspension types, and locations of the point of interest in the pavement. A major contribution of the study is that the variation of pavement responses due to dynamic load in a flexible pavement system can be predicted with generalized regression equations. Fitting parameters (R2) in the

Efficient graph-based dynamic load-balancing for parallel large-scale agent-based traffic simulation

NARCIS (Netherlands)

Xu, Y.; Cai, W.; Aydt, H.; Lees, M.; Tolk, A.; Diallo, S.Y.; Ryzhov, I.O.; Yilmaz, L.; Buckley, S.; Miller, J.A.

2014-01-01

One of the issues of parallelizing large-scale agent-based traffic simulations is partitioning and load-balancing. Traffic simulations are dynamic applications where the distribution of workload in the spatial domain constantly changes. Dynamic load-balancing at run-time has shown better efficiency

Fatigue behaviour of core-spun yarns containing filament by means of cyclic dynamic loading

Science.gov (United States)

Esin, S.; Osman, B.

2017-10-01

The behaviour of yarns under dynamic loading is important that leads to understand the growth characteristics which is exposed to repetitive loadings during usage of fabric made from these yarns. Fabric growth is undesirable property that originated from low resilience characteristics of fabric. In this study, the effects of the filament fineness and yarn linear density on fatigue behaviour of rigid-core spun yarns were determined. Cotton covered yarns containing different filament fineness of polyester (PET) draw textured yarns (DTY) (100d/36f, 100d/96f, 100d/144f, 100d/192f and 100d/333f) and yarn linear densities (37 tex, 30 tex, 25 tex and 21 tex) were manufactured by using a modified ring spinning system at the same spinning parameters. Repetitive loads were applied for 25 cycles at levels between 0.1 and 3 N. Dynamic modulus and dynamic strain of yarn samples were analyzed statistically. Results showed that filament fineness and yarn linear density have significance effect on dynamic modulus and dynamic strain after cyclic loading.

On the dynamic stability of shear deformable beams under a tensile load

Science.gov (United States)

Caddemi, S.; Caliò, I.; Cannizzaro, F.

2016-07-01

Loss of stability of beams in a linear static context due to the action of tensile loads has been disclosed only recently in the scientific literature. However, tensile instability in the dynamic regime has been only marginally covered. Several aspects concerning the role of shear deformation on the tensile dynamic instability on continuous and discontinuous beams are still to be addressed. It may appear as a paradox, but also for the case of the universally studied Timoshenko beam model, despite its old origin, frequency-axial load diagrams in the range of negative values of the load (i.e. tensile load) has never been brought to light. In this paper, for the first time, the influence of a conservative tensile axial loads on the dynamic behaviour of the Timoshenko model, according to the Haringx theory, is assessed. It is shown that, under increasing tensile loads, regions of positive/negative fundamental frequency variations can be distinguished. In addition, the beam undergoes eigen-mode changes, from symmetric to anti-symmetric shapes, until tensile instability of divergence type is reached. As a further original contribution on the subject, taking advantage of a new closed form solution, it is shown that the same peculiarities are recovered for an axially loaded Euler-Bernoulli vibrating beam with multiple elastic sliders. This latter model can be considered as the discrete counterpart of the Timoshenko beam-column in which the internal sliders concentrate the shear deformation that in the Timoshenko model is continuously distributed. Original aspects regarding the evolution of the vibration frequencies and the relevant mode shapes with the tensile load value are highlighted.

Influence of the implant abutment types and the dynamic loading on initial screw loosening

OpenAIRE

Kim, Eun-Sook; Shin, Soo-Yeon

2013-01-01

PURPOSE This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at ...

Shaft centre orbit for dynamically loaded radial bearings

DEFF Research Database (Denmark)

Klit, Peder; Vølund, Anders

2002-01-01

The aim of this work is to demonstrate how to utilize the bearings damping coefficients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 Booker1 and described further in 1972 Booker2. Several authors have refine...

Dynamic load effects on gate valve operability

International Nuclear Information System (INIS)

Steele, R. Jr.; MacDonald, P.E.; Arendts, J.G.

1986-01-01

The Idaho National Engineering Laboratory (INEL) participated in an internationally sponsored seismic research program conducted at the decommissioned Heissdampfreaktor (HDR) located in the Federal Republic of Germany. An existing piping system was modified by installation of an 8-in., naturally aged, motor-operated gate valve from a US nuclear power plant and a piping support system of US design. Six other piping support systems of varying flexibility from stiff to flexible were also installed at various times during the tests. Additional valve loadings included internal hydraulic loads and, during one block of tests, elevated temperature. The operability and integrity of the aged gate valve and the dynamic response of the various piping support system were measured during 25 representative seismic events

Dynamic control of a bistable wing under aerodynamic loading

International Nuclear Information System (INIS)

Bilgen, Onur; Arrieta, Andres F; Friswell, Michael I; Hagedorn, Peter

2013-01-01

The aerodynamic evaluation of a dynamic control technique applied to a bistable unsymmetrical cross-ply composite plate with surface bonded piezoelectric actuators is presented. The plate is clamped on one end to form a low-aspect-ratio wing. A previously proposed dynamic control method, utilizing bending resonance in different stable equilibrium positions, is used to induce snap-through between the two equilibrium states. Compared to quasi-static actuation, driving the bistable plate near resonance using surface bonded piezoelectric materials requires, theoretically, a lower peak excitation voltage to achieve snap-through. First, a set of extensive wind tunnel experiments are conducted on the passive bistable wing to understand the change in the dynamic behavior under various aerodynamic conditions. The passive wing demonstrated sufficient bending stiffness to sustain its shape under aerodynamic loading while preserving the desired bistable behavior. Next, by the use of the resonant control technique, the plate is turned into an effectively monostable structure, or alternatively, both stable equilibrium positions can be reached actively from the other stable equilibrium. Dynamic forward and reverse snap-through is demonstrated in the wind tunnel which shows both the effectiveness of the piezoelectric actuation as well as the load carrying capability of both states of the bistable wing. (paper)

Loading technique for dynamic response studies of geological materials

International Nuclear Information System (INIS)

Butler, R.I.; Forrestal, M.J.

1979-04-01

A loading technique to study the dynamic response of tuff was explored. Loading is provided by electrically exploding etched copper mesh patterns with current from a capacitor discharge. Pressure pulses with peak pressures up to 1.25 kbar and 0.10 to 0.20 ms durations were measured with a pressure bar. The upper value of peak pressure was limited by the strength of the experimental apparatus, and higher pressure generation is possible with a redesign of test hardware. 6 figures, 2 tables

Dynamic Response of Coarse Granular Material to Wave Load

DEFF Research Database (Denmark)

Ibsen, Lars Bo

1998-01-01

The soil beneath vertical breakwaters is subjected to a combination of forces induced by the waves. The forces acting on the soil can be characterized as 1) static load due to submerged weight of the structure, 2) quasi-static forces induced by cyclic wave loading, and 3) wave impact from breaking...... waves. The stress conditions in the soil below a foundation exposed to these types of loading are very complex. The key to explain and quantify the soil response beneath a vertical breakwater is to understand the role of the volume changes and to be able to model these correctly. It is shown...... that the volume changes in soil subjected to static and dynamic loading are controlled by the characteristic line. Experiments have been performed to study the factors that influence the location of the characteristic line in drained and undrained tests for various types of sand and various types of loading...

Dynamic stresses in a Francis model turbine at deep part load

Science.gov (United States)

Weber, Wilhelm; von Locquenghien, Florian; Conrad, Philipp; Koutnik, Jiri

2017-04-01

A comparison between numerically obtained dynamic stresses in a Francis model turbine at deep part load with experimental ones is presented. Due to the change in the electrical power mix to more content of new renewable energy sources, Francis turbines are forced to operate at deep part load in order to compensate stochastic nature of wind and solar power and to ensure grid stability. For the extension of the operating range towards deep part load improved understanding of the harsh flow conditions and their impact on material fatigue of hydraulic components is required in order to ensure long life time of the power unit. In this paper pressure loads on a model turbine runner from unsteady two-phase computational fluid dynamics simulation at deep part load are used for calculation of mechanical stresses by finite element analysis. Therewith, stress distribution over time is determined. Since only few runner rotations are simulated due to enormous numerical cost, more effort has to be spent to evaluation procedure in order to obtain objective results. By comparing the numerical results with measured strains accuracy of the whole simulation procedure is verified.

Evaluation of muscle activity for loaded and unloaded dynamic squats during vertical whole-body vibration.

Science.gov (United States)

Hazell, Tom J; Kenno, Kenji A; Jakobi, Jennifer M

2010-07-01

The purpose of this investigation was to examine if the addition of a light external load would enhance whole-body vibration (WBV)-induced increases in muscle activity during dynamic squatting in 4 leg muscles. Thirteen recreationally active male university students performed a series of dynamic squats (unloaded with no WBV, unloaded with WBV, loaded with no WBV, and loaded with WBV). The load was set to 30% of body mass and WBV included 25-, 35-, and 45-Hz frequencies with 4-mm amplitude. Muscle activity was recorded with surface electromyography (EMG) on the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GC) and is reported as EMGrms (root mean square) normalized to %maximal voluntary exertion. During unloaded dynamic squats, exposure to WBV (45 Hz) significantly (p squat exercise in all muscles but decreased the TA. This loaded level of muscle activity was further increased with WBV (45 Hz) in all muscles. The WBV-induced increases in muscle activity in the loaded condition (approximately 3.5%) were of a similar magnitude to the WBV-induced increases during the unloaded condition (approximately 2.5%) demonstrating the addition of WBV to unloaded or loaded dynamic squatting results in an increase in muscle activity. These results demonstrate the potential effectiveness of using external loads with exposure to WBV.

A technique for measuring dynamic friction coefficient under impact loading.

Science.gov (United States)

Lin, Y L; Qin, J G; Chen, R; Zhao, P D; Lu, F Y

2014-09-01

We develop a novel setup based on the split Hopkinson pressure bar technique to test the dynamic friction coefficient under impact loading. In the setup, the major improvement is that the end of the incident bar near the specimen is wedge-shaped, which results in a combined compressive and shear loading applied to the specimen. In fact, the shear loading is caused by the interfacial friction between specimen and bars. Therefore, when the two loading force histories are measured, the friction coefficient histories can be calculated without any assumptions and theoretical derivations. The geometry of the friction pairs is simple, and can be either cuboid or cylindrical. Regarding the measurements, two quartz transducers are used to directly record the force histories, and an optical apparatus is designed to test the interfacial slip movement. By using the setup, the dynamic friction coefficient of PTFE/aluminum 7075 friction pairs was tested. The time resolved dynamic friction coefficient and slip movement histories were achieved. The results show that the friction coefficient changes during the loading process, the average data of the relatively stable flat plateau section of the friction coefficient curves is 0.137, the maximum normal pressure is 52 MPa, the maximum relative slip velocity is 1.5 m/s, and the acceleration is 8400 m(2)/s. Furthermore, the friction test was simulated using an explicit FEM code LS-DYNA. The simulation results showed that the constant pressure and slip velocity can both be obtained with a wide flat plateau incident pulse. For some special friction pairs, normal pressure up to a few hundred MPa, interfacial slip velocities up to 10 m/s, and slip movement up to centimeter-level can be expected.

Response of porous beryllium to static and dynamic loading

Energy Technology Data Exchange (ETDEWEB)

Isbell, W.M.; Walton, O.R.; Ree, F.H.

1977-07-01

Previous investigstions of the mechanical response of porous materials to dynamic loading have been extended to include the shock wave response of a brittle metal. The complex response of berylliums of 85 to 90 percent porosity in two initial conditions has been examined in a theoretical and experimental program to be described. The study has resulted in the development of constitutive relations placed in hydrocodes which are capable of accurately predicting wave propagation in the berylliums. A comprehensive set of static (0 to 4 Gpa) and dynamic (0 to 35 Gpa) experiments was performed to measure the behavior of these brittle, porous materials to imposed loads. The results of the experiments guided a modeling effort which added several new features to previous models, including deviatoric stresses, porosity-dependent relaxation time of pore closure, elastic-plastic reopening of pores, and improved compaction functions.

Response of porous beryllium to static and dynamic loading

International Nuclear Information System (INIS)

Isbell, W.M.; Walton, O.R.; Ree, F.H.

1977-07-01

Previous investigstions of the mechanical response of porous materials to dynamic loading have been extended to include the shock wave response of a brittle metal. The complex response of berylliums of 85 to 90 percent porosity in two initial conditions has been examined in a theoretical and experimental program to be described. The study has resulted in the development of constitutive relations placed in hydrocodes which are capable of accurately predicting wave propagation in the berylliums. A comprehensive set of static (0 to 4 Gpa) and dynamic (0 to 35 Gpa) experiments was performed to measure the behavior of these brittle, porous materials to imposed loads. The results of the experiments guided a modeling effort which added several new features to previous models, including deviatoric stresses, porosity-dependent relaxation time of pore closure, elastic-plastic reopening of pores, and improved compaction functions

Dynamic Analysis of Helical Planetary Gear Sets under Combined Force and Moment Loading

Directory of Open Access Journals (Sweden)

Yanfang Liu

2017-01-01

Full Text Available The dynamic behavior of a single-stage planetary gear set with helical gears of multishaft automotive automatic transmissions has been studied, in which one component of the planetary gear set is imposed by additional external vertical and axial loading from countershaft gear pair in addition to the moment. Under these combined loading conditions, the contributions of the deflections of the ring gear and the carrier cannot be neglected. A three-dimensional nonlinear time-variant dynamic model considering not only the transverse, torsional, axial, and rotational motions of the gears but also the elasticity of the mounted shafts has been developed by combining the lumped parameter method with finite element method. The natural modes and the forced vibration responses due to static transmission errors have been obtained. The proposed dynamic model is employed to describe the effects of the combined external loading condition and positioning on the dynamic behavior of a four-planet system.

Dynamic analysis of elastic rubber tired car wheel breaking under variable normal load

Science.gov (United States)

Fedotov, A. I.; Zedgenizov, V. G.; Ovchinnikova, N. I.

2017-10-01

The purpose of the paper is to analyze the dynamics of the braking of the wheel under normal load variations. The paper uses a mathematical simulation method according to which the calculation model of an object as a mechanical system is associated with a dynamically equivalent schematic structure of the automatic control. Transfer function tool analyzing structural and technical characteristics of an object as well as force disturbances were used. It was proved that the analysis of dynamic characteristics of the wheel subjected to external force disturbances has to take into account amplitude and phase-frequency characteristics. Normal load variations impact car wheel braking subjected to disturbances. The closer slip to the critical point is, the higher the impact is. In the super-critical area, load variations cause fast wheel blocking.

46 CFR 154.409 - Dynamic loads from vessel motion.

Science.gov (United States)

2010-10-01

... in length and is an analysis by the following formulae that corresponds to a 10−8 probability level... EC02FE91.086 (d) If a cargo tank is designed to avoid fatigue, the dynamic loads determined under paragraph...

Dynamic load-sharing characteristic analysis of face gear power-split gear system based on tooth contact characteristics

Science.gov (United States)

Dong, Hao; Hu, Yahui

2018-04-01

The bend-torsion coupling dynamics load-sharing model of the helicopter face gear split torque transmission system is established by using concentrated quality standard, to analyzing the dynamic load-sharing characteristic. The mathematical models include nonlinear support stiffness, time-varying meshing stiffness, damping, gear backlash. The results showed that the errors collectively influenced the load sharing characteristics, only reduce a certain error, it is never fully reached the perfect loading sharing characteristics. The system load-sharing performance can be improved through floating shaft support. The above-method will provide a theoretical basis and data support for its dynamic performance optimization design.

Self-organized dynamics in local load-sharing fiber bundle models.

Science.gov (United States)

Biswas, Soumyajyoti; Chakrabarti, Bikas K

2013-10-01

We study the dynamics of a local load-sharing fiber bundle model in two dimensions under an external load (which increases with time at a fixed slow rate) applied at a single point. Due to the local load-sharing nature, the redistributed load remains localized along the boundary of the broken patch. The system then goes to a self-organized state with a stationary average value of load per fiber along the (increasing) boundary of the broken patch (damaged region) and a scale-free distribution of avalanche sizes and other related quantities are observed. In particular, when the load redistribution is only among nearest surviving fiber(s), the numerical estimates of the exponent values are comparable with those of the Manna model. When the load redistribution is uniform along the patch boundary, the model shows a simple mean-field limit of this self-organizing critical behavior, for which we give analytical estimates of the saturation load per fiber values and avalanche size distribution exponent. These are in good agreement with numerical simulation results.

Long-term dynamic loading improves the mechanical properties of chondrogenic mesenchymal stem cell-laden hydrogel

Directory of Open Access Journals (Sweden)

AH Huang

2010-02-01

Full Text Available Mesenchymal stem cells (MSCs are an attractive cell source for cartilage tissue engineering given their ability to undergo chondrogenesis in 3D culture systems. Mechanical forces play an important role in regulating both cartilage development and MSC chondrogenic gene expression, however, mechanical stimulation has yet to enhance the mechanical properties of engineered constructs. In this study, we applied long-term dynamic compression to MSC-seeded constructs and assessed whether varying pre-culture duration, loading regimens and inclusion of TGF-beta3 during loading would influence functional outcomes and these phenotypic transitions. Loading initiated before chondrogenesis decreased functional maturation, although chondrogenic gene expression increased. In contrast, loading initiated after chondrogenesis and matrix elaboration further improved the mechanical properties of MSC-based constructs, but only when TGF-beta3 levels were maintained and under specific loading parameters. Although matrix quantity was not affected by dynamic compression, matrix distribution, assessed histologically and by FT-IRIS analysis, was significantly improved on the micro- (pericellular and macro- (construct expanse scales. Further, whole genome expression profiling revealed marked shifts in the molecular topography with dynamic loading. These results demonstrate, for the first time, that dynamic compressive loading initiated after a sufficient period of chondro-induction and with sustained TGF-beta exposure enhances matrix distribution and the mechanical properties of MSC-seeded constructs.

Dynamic Regression Intervention Modeling for the Malaysian Daily Load

Directory of Open Access Journals (Sweden)

Fadhilah Abdrazak

2014-05-01

Full Text Available Malaysia is a unique country due to having both fixed and moving holidays.  These moving holidays may overlap with other fixed holidays and therefore, increase the complexity of the load forecasting activities. The errors due to holidays’ effects in the load forecasting are known to be higher than other factors.  If these effects can be estimated and removed, the behavior of the series could be better viewed.  Thus, the aim of this paper is to improve the forecasting errors by using a dynamic regression model with intervention analysis.   Based on the linear transfer function method, a daily load model consists of either peak or average is developed.  The developed model outperformed the seasonal ARIMA model in estimating the fixed and moving holidays’ effects and achieved a smaller Mean Absolute Percentage Error (MAPE in load forecast.

The Comprehensive Biomechanics and Load-Sharing of Semirigid PEEK and Semirigid Posterior Dynamic Stabilization Systems

Directory of Open Access Journals (Sweden)

D. K. Sengupta

2013-01-01

Full Text Available Alternatives to conventional rigid fusion have been proposed for several conditions related to degenerative disc disease when nonoperative treatment has failed. Semirigid fixation, in the form of dynamic stabilization or PEEK rods, is expected to provide compression under loading as well as an intermediate level of stabilization. This study systematically examines both the load-sharing characteristics and kinematics of these two devices compared to the standard of internal rigid fixators. Load-sharing was studied by using digital pressure films inserted between an artificially machined disc and two loading fixtures. Rigid rods, PEEK rods, and the dynamic stabilization system were inserted posteriorly for stabilization. The kinematics were quantified on ten, human, cadaver lumbosacral spines (L3-S1 which were tested under a pure bending moment, in flexion-extension, lateral bending, and axial rotation. The magnitude of load transmission through the anterior column was significantly greater with the dynamic device compared to PEEK rods and rigid rods. The contact pressures were distributed more uniformly, throughout the disc with the dynamic stabilization devices, and had smaller maximum point-loading (pressures on any particular point within the disc. Kinematically, the motion was reduced by both semirigid devices similarly in all directions, with slight rigidity imparted by a lateral interbody device.

Dynamic loading of galvanized parts

Directory of Open Access Journals (Sweden)

Michal Černý

2010-01-01

Full Text Available This work is divided into two parts: the theoretical part includes actual knowledge and points of view about degradation processes in construction materials, anticorrosion protection, zinc coat composition and high frequency fatigue. The laboratory part follow-up existing regulations contents Czech standards and formulate specifications for acquisition of objective information from acceleration la­bo­ra­to­ry tests in condensation chests, mechanical high frequency fatigue tests on pulsator machine and possibilities of evaluation of fatigue tests. Laboratory findings declare to fundamental types of damage of constructions with anticorrosion protection in real loading conditions with dynamic high frequency character. Laboratory tests were made in sulphide and chloride environments.

The Influence of External Load on Quadriceps Muscle and Tendon Dynamics during Jumping.

Science.gov (United States)

Earp, Jacob E; Newton, Robert U; Cormie, Prue; Blazevich, Anthony J

2017-11-01

Tendons possess both viscous (rate-dependent) and elastic (rate-independent) properties that determine tendon function. During high-speed movements external loading increases both the magnitude (FT) and rate (RFDT) of tendon loading. The influence of external loading on muscle and tendon dynamics during maximal vertical jumping was explored. Ten resistance-trained men performed parallel-depth, countermovement vertical jumps with and without additional load (0%, 30%, 60%, and 90% of maximum squat lift strength), while joint kinetics and kinematics, quadriceps tendon length (LT) and patellar tendon FT and RFDT were estimated using integrated ultrasound, motion analysis and force platform data and muscle tendon modelling. Estimated FT and RFDT, but not peak LT, increased with external loading. Temporal comparisons between 0% and 90% loads revealed that FT was greater with 90% loading throughout the majority of the movement (11%-81% and 87%-95% movement duration). However, RFDT was greater with 90% load only during the early movement initiation phase (8%-15% movement duration) but was greater in the 0% load condition later in the eccentric phase (27%-38% movement duration). LT was longer during the early movement (12%-23% movement duration) but shorter in the late eccentric and early concentric phases (48%-55% movement duration) with 90% load. External loading positively influenced peak FT and RFDT but tendon strain appeared unaffected, suggesting no additive effect of external loading on patellar tendon lengthening during human jumping. Temporal analysis revealed that external loading resulted in a large initial RFDT that may have caused dynamic stiffening of the tendon and attenuated tendon strain throughout the movement. These results suggest that external loading influences tendon lengthening in both a load- and movement-dependent manner.

Quality of computerized blast load simulation for non-linear dynamic ...

African Journals Online (AJOL)

Quality of computerized blast load simulation for non-linear dynamic response ... commercial software system and a special-purpose, blast-specific software product to ... depend both on the analysis model of choice and the stand-off distances.

Loading dynamics of a sliding DNA clamp.

KAUST Repository

Cho, Won-Ki

2014-05-22

Sliding DNA clamps are loaded at a ss/dsDNA junction by a clamp loader that depends on ATP binding for clamp opening. Sequential ATP hydrolysis results in closure of the clamp so that it completely encircles and diffuses on dsDNA. We followed events during loading of an E. coli β clamp in real time by using single-molecule FRET (smFRET). Three successive FRET states were retained for 0.3 s, 0.7 s, and 9 min: Hydrolysis of the first ATP molecule by the γ clamp loader resulted in closure of the clamp in 0.3 s, and after 0.7 s in the closed conformation, the clamp was released to diffuse on the dsDNA for at least 9 min. An additional single-molecule polarization study revealed that the interfacial domain of the clamp rotated in plane by approximately 8° during clamp closure. The single-molecule polarization and FRET studies thus revealed the real-time dynamics of the ATP-hydrolysis-dependent 3D conformational change of the β clamp during loading at a ss/dsDNA junction.

Variation of Pore Water Pressure in Tailing Sand under Dynamic Loading

Directory of Open Access Journals (Sweden)

Jia-xu Jin

2018-01-01

Full Text Available Intense vibration affects the pore water pressure in a tailing dam, with the tendency to induce dam liquefaction. In this study, experiments were performed wherein model tailing dams were completely liquefied by sustained horizontal dynamic loading to determine the effects of the vibration frequency, vibration amplitude, and tailing density on the pore water pressure. The results revealed four stages in the increase of the tailing pore water pressure under dynamic loading, namely, a slow increase, a rapid increase, inducement of structural failure, and inducement of complete liquefaction. A lower frequency and smaller amplitude of the vibration were found to increase the time required to achieve a given pore water pressure in dense tailings. Under the effect of these three factors—vibration frequency and amplitude and tailing density—the tailing liquefaction time varied nonlinearly with the height from the base of the tailing dam, with an initial decrease followed by an increase. The pore pressure that induced structural failure also gradually decreased with increasing height. The increase in the tailing pore pressure could be described by an S-shaped model. A complementary multivariate nonlinear equation was also derived for predicting the tailing pore water pressure under dynamic loading.

Analysis of Dynamic Properties of Piezoelectric Structure under Impact Load

Directory of Open Access Journals (Sweden)

Taotao Zhang

2015-10-01

Full Text Available An analytical model of the dynamic properties is established for a piezoelectric structure under impact load, without considering noise and perturbations in this paper. Based on the general theory of piezo-elasticity and impact mechanics, the theoretical solutions of the mechanical and electrical fields of the smart structure are obtained with the standing and traveling wave methods, respectively. The comparisons between the two methods have shown that the standing wave method is better for studying long-time response after an impact load. In addition, good agreements are found between the theoretical and the numerical results. To simulate the impact load, both triangle and step pulse loads are used and comparisons are given. Furthermore, the influence of several parameters is discussed so as to provide some advices for practical use. It can be seen that the proposed analytical model would benefit, to some extent, the design and application (especially the airport runway of the related smart devices by taking into account their impact load performance.

Dynamic supplier selection problem considering full truck load in probabilistic environment

Science.gov (United States)

Sutrisno, Wicaksono, Purnawan Adi

2017-11-01

In this paper, we propose a mathematical model in a probabilistic dynamic optimization to solve a dynamic supplier selection problem considering full truck load in probabilistic environment where some parameters are uncertain. We determine the optimal strategy for this problem by using stochastic dynamic programming. We give some numerical experiments to evaluate and analyze the model. From the results, the optimal supplier and the optimal product volume from the optimal supplier were determined for each time period.

Ensuring dynamic load smoothness in problem of controlling Atomic Electric Power Stations exclusive mechanisms

International Nuclear Information System (INIS)

Shumilov, V.F.

2003-01-01

New methods for the investigation of automatic systems based on the inverse tasks of dynamics with the use of rational, trigonometric and polynomial spline functions are discussed. By means of SH function the technological regimes: start-up, steadiness, racing, braking, reverse, stop were determined. Procedure for the provision of dynamic load smoothness is suggested, and example of control over the transport systems for fuel load is considered [ru

HOLD MODE BASED DYNAMIC PRIORITY LOAD ADAPTIVE INTERPICONET SCHEDULING FOR BLUETOOTH SCATTERNETS

Directory of Open Access Journals (Sweden)

G.S. Mahalakshmi

2011-09-01

Full Text Available Scheduling in piconets has emerged as a challenging research area. Interpiconet scheduling focuses on when a bridge is switched among various piconets and how a bridge node communicates with the masters in different piconets. This paper proposes an interpiconet scheduling algorithm named, hold mode based dynamic traffic priority load adaptive scheduling. The bridges are adaptively switched between the piconets according to various traffic loads. The main goal is to maximize the utilization of the bridge by reducing the bridge switch wastes, utilize intelligent decision making algorithm, resolve conflict between the masters, and allow negotiation for bridge utilization in HDPLIS using bridge failure-bridge repair procedure . The Hold mode - dynamic traffic - priority based - load adaptive scheduling reduces the number of bridge switch wastes and hence increases the efficiency of the bridge which results in increased performance of the system.

Dynamic load-balancing-extended gradient mechanism: Graphic representation

International Nuclear Information System (INIS)

Muniz, Francisco J.

2017-01-01

Load-balancing methods are quite well described in the open literature (hundreds of articles can be found about this subject). In particularly, about the Dynamic Load-balancing mechanism Extended Gradient (EG), several articles of the author are available. Even though, there are some overlap, each one of them is focused on a particular aspect of the mechanism, in a complementary way. In this article, a graphic representation of the Extended Gradient mechanism is done: this representation way had not yet been explored. However, for an in-depth knowledge of the Extended Gradient mechanism, at least, some other articles should to be read. In the CDTN, Clusters are used, mainly, in deterministic methods (CFD) and non-deterministic methods (Monte Carlo). (author)

Dynamic load-balancing-extended gradient mechanism: Graphic representation

Energy Technology Data Exchange (ETDEWEB)

Muniz, Francisco J., E-mail: muniz@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2017-07-01

Load-balancing methods are quite well described in the open literature (hundreds of articles can be found about this subject). In particularly, about the Dynamic Load-balancing mechanism Extended Gradient (EG), several articles of the author are available. Even though, there are some overlap, each one of them is focused on a particular aspect of the mechanism, in a complementary way. In this article, a graphic representation of the Extended Gradient mechanism is done: this representation way had not yet been explored. However, for an in-depth knowledge of the Extended Gradient mechanism, at least, some other articles should to be read. In the CDTN, Clusters are used, mainly, in deterministic methods (CFD) and non-deterministic methods (Monte Carlo). (author)

Ductile Crack Initiation Criterion with Mismatched Weld Joints Under Dynamic Loading Conditions.

Science.gov (United States)

An, Gyubaek; Jeong, Se-Min; Park, Jeongung

2018-03-01

Brittle failure of high toughness steel structures tends to occur after ductile crack initiation/propagation. Damages to steel structures were reported in the Hanshin Great Earthquake. Several brittle failures were observed in beam-to-column connection zones with geometrical discontinuity. It is widely known that triaxial stresses accelerate the ductile fracture of steels. The study examined the effects of geometrical heterogeneity and strength mismatches (both of which elevate plastic constraints due to heterogeneous plastic straining) and loading rate on critical conditions initiating ductile fracture. This involved applying the two-parameter criterion (involving equivalent plastic strain and stress triaxiality) to estimate ductile cracking for strength mismatched specimens under static and dynamic tensile loading conditions. Ductile crack initiation testing was conducted under static and dynamic loading conditions using circumferentially notched specimens (Charpy type) with/without strength mismatches. The results indicated that the condition for ductile crack initiation using the two parameter criterion was a transferable criterion to evaluate ductile crack initiation independent of the existence of strength mismatches and loading rates.

Nonlinear modeling and dynamic analysis of hydro-turbine governing system in the process of load rejection transient

International Nuclear Information System (INIS)

Zhang, Hao; Chen, Diyi; Xu, Beibei; Wang, Feifei

2015-01-01

Graphical abstract: Nonlinear dynamic transfer coefficients are introduced to the hydro-turbine governing system. In the process of load reject ion transient, the nonlinear dynamical behaviors of the system are studied in detail. - Highlights: • A novel mathematical model of a hydro-turbine governing system is established. • The process of load rejection transient is considered. • Nonlinear dynamic transfer coefficients are introduced to the system. • The bifurcation diagram with the variable t has better engineering significance. • The nonlinear dynamical behaviors of the system are studied in detail. - Abstract: This article pays attention to the mathematical modeling of a hydro-turbine governing system in the process of load rejection transient. As a pioneer work, the nonlinear dynamic transfer coefficients are introduced in a penstock system. Considering a generator system, a turbine system and a governor system, we present a novel nonlinear dynamical model of a hydro-turbine governing system. Fortunately, for the unchanged of PID parameters, we acquire the stable regions of the governing system in the process of load rejection transient by numerical simulations. Moreover, the nonlinear dynamic behaviors of the governing system are illustrated by bifurcation diagrams, Poincare maps, time waveforms and phase orbits. More importantly, these methods and analytic results will present theoretical groundwork for allowing a hydropower station in the process of load rejection transient

Performance of various types of containment support under quasi-static and dynamic loading conditions, Part I.

CSIR Research Space (South Africa)

Kuijpers, JS

2002-05-01

Full Text Available deformations. In this project, the effects of dynamic loading are therefore specifically addressed. In order to monitor the effects of extreme dynamic loading conditions on various tunnel support systems, a real scale physical model has been used... systems and allow the identification of shortcomings and potential improvements. A conceptual, analytical model representing the load deformation behaviour of strings (lacing and mesh) has been developed. This model does allow for a quantification...

Optimization of structures subjected to dynamic load: deterministic and probabilistic methods

Directory of Open Access Journals (Sweden)

Élcio Cassimiro Alves

Full Text Available Abstract This paper deals with the deterministic and probabilistic optimization of structures against bending when submitted to dynamic loads. The deterministic optimization problem considers the plate submitted to a time varying load while the probabilistic one takes into account a random loading defined by a power spectral density function. The correlation between the two problems is made by one Fourier Transformed. The finite element method is used to model the structures. The sensitivity analysis is performed through the analytical method and the optimization problem is dealt with by the method of interior points. A comparison between the deterministic optimisation and the probabilistic one with a power spectral density function compatible with the time varying load shows very good results.

Dynamic characterization and modeling of magneto-rheological elastomers under compressive loadings

International Nuclear Information System (INIS)

Koo, J H; Khan, F; Jang, D D; Jung, H J

2009-01-01

The primary goal of this paper is to characterize and model the compression properties of Magneto-Rheological Elastomers (MREs). MRE samples were fabricated by curing a two component elastomer resin with 30% content of 10 μm sized iron particles by volume. In order to vary the magnetic field during compressive testing, a test fixture was designed and fabricated in which two permanent magnets could be variably positioned on either side of the specimen. By changing the distance between the magnets, the fixture allowed for varying the magnetic field that passes uniformly through the sample. Using this test setup and a dynamic test frame, a series of compression tests of MRE samples was performed by varying the magnetic field and frequency of loading. The results show the MR effect (percent increase in the materials 'stiffness') increases as the magnetic field increases and loading frequency increases within the range of the magnetic field and input frequency considered in this study. Furthermore, a phenomenological model was developed to capture the dynamic behaviours of the MREs under compression loadings.

Substantiation of strength of TVSA-ALPHA fuel assembly under dynamic seismic loads

International Nuclear Information System (INIS)

Tutnov, A.; Kiselev, A.; Kiselev, A.; Krutko, E.; Kiselev, I.; Samoilov, O.; Kaydalov, V.

2009-01-01

A special place in the substantiation of the safe operation of fuel assemblies is the assessment their operating capability under seismic loads, leading to short-term (several seconds or tens of seconds) the dynamic effects on the reactor core. The level of acceleration of various elements of the reactor installation can be higher than 1,5 g (g - acceleration of gravity) and depends on the height of these elements relatively the ground, which movement causes an earthquake. This dynamic load cause significant deformation of the active zones design element, in particular of the fuel assemblies (FA), which could lead to a contact (or impact) interaction between them. The report presents the results of studies of stress-strain state of FA of TVSA-ALPHA type under the influence of seismic loads of the 8th level on Richter scale using standard approach. According to a normative approach the natural frequencies and modes of FA are calculated in the preliminary stage. The obtained results are conservative from the point of view that in the real FA design the most loaded SG in the middle of the fuel assemblies are made in a combined with mixing grid variant, which are joint by a common rim. This increases the overall carrying capacity of SG as compared with the calculation SG model. It is also necessary to bear in mind that the dynamic (impact) loading the basic mechanical properties of the material may have a significant difference from static (standard) values. This refers in particular to the yield limit, the value of which can be several times higher than specified in the calculation

Research of thermal dynamic characteristics for variable load single screw refrigeration compressor with different capacity control mechanism

International Nuclear Information System (INIS)

Wang, Zengli; Wang, Zhenbo; Wang, Jun; Jiang, Wenchun; Feng, Quanke

2017-01-01

Highlights: • Theoretical models of SSRC under part-load condition have been established. • The experiment of SSRC performance under part-load condition was conducted. • Thermal dynamic characteristic of SSRC under part-load condition was gained. • Economy and reliability of SSRC under part-load condition was analyzed. - Abstract: In the single screw refrigeration compressor (SSRC), the capacity control mechanism is normally employed to meet the actual required cooling capacity under different load conditions. In this paper, theoretical calculation models describing the working process of the SSRC with the single slide valve capacity control mechanism (SVCCM) and SSRC with the frequency conversion regulating mechanism (FCRM) are established to research the thermal dynamic characteristics for variable load SSRC under part-load conditions. Experimental investigation on a SSRC under part-load conditions is also carried out to verify the theoretical calculation models. By using these validated models, the thermodynamic performances and dynamic characteristics of the SSRC with different capacity control mechanism under part-load conditions have been analyzed and compared. Through the comparison, the economical efficiency and reliability of the SSRC with different capacity control mechanism were obtained. All of these works can provide the basis for the later optimization design for the variable load single screw refrigeration compressor.

A Reduced-Order Model for Evaluating the Dynamic Response of Multilayer Plates to Impulsive Loads

Science.gov (United States)

2016-04-12

A REDUCED-ORDER MODEL FOR EVALUATING THE DYNAMIC RESPONSE OF MULTILAYER PLATES TO IMPULSIVE LOADS Weiran Jiang, Alyssa Bennett, Nickolas...innovative multilayer materials or structures to optimize the dynamic performance as a mechanism to absorb and spread energy from an impulsive load...models. • Optimizing the structural weight and levels of protection of the multilayer plates with a good combination of materials. Technical Approach 2016

Evaluation of dynamic loads induced by transient regimes of fluid flows in the pipe systems and devices of reducing the loads and their effects

International Nuclear Information System (INIS)

Serban, Viorel; Chirita, Alexandru Mihai; Androne, Marian; Alexandru, Constantin; Ciuca, Camelia; Badara, Janina; Alexandru, Carmen

1995-01-01

The paper presents the analytic methods for estimating the dynamic effects induced in pipe systems in transient regimes. They are based on computation programs developed in order to check the behaviour of ECCS and EWS under 'water hammer effect' and the behaviour of the primary circuit system under stresses caused by pipe cracks. Computation examples are presented in order to emphasize the capabilities of the programs to model transient phenomena in complex pipe networks. The overpressure induced by the water hammer effect, as revealed by comparing several transient regimes, depends on the fluid viscosity, the initial speed, the duration of starting the transient regime, the system rigidity, etc. Values several ten times higher that the initial one could be thus reached. An overview of new types of devices designed for damping the effect of water hammer phenomenon, as well as of sustaining supports for pipe systems and equipment able to damp the vibrations produced by the transient regimes of fluid flows and seismic movements is presented. These devices have also to cope with the high shocks produced by pipe breakage as well as high static loads. The paper contains the following sections: 1. Introduction; 2. Evaluating dynamic loads associated to the water hammer phenomenon; 3. Determining loads associated to the water hammer phenomenon for the ECC system of the Cernavoda NPP Unit 1; 4. Device for reducing the water hammer effects; 5. Evaluating dynamic loads associated to pipe cracks; 6. Determining loads associated to pipe cracks in the Cernavoda NPP primary circuit; 7. Devices for absorbing and damping the dynamic loads in pipe systems and equipment; 8. Conclusions. (authors)

STAMINA OF A GASKETED BOLTED FLANGED PIPE JOINT UNDER DYNAMIC LOADING

Directory of Open Access Journals (Sweden)

Muhammad Abid

2016-11-01

Full Text Available Gasketed bolted flange joints are the most critical components in pipelines for their sealing and strength under operating conditions. Most of the work available in literature is under static loading, whereas in industry, cyclic loads are applied due to the vibrating machinery such as motors, pumps, sloshing in offshore applications and in the ships etc. In this study a three dimensional finite element analysis of a gasketed joint is carried out using a spiral wound gasket under bolt up and dynamic operating conditions (internal pressure, axial and bending singly and in combination. The cyclic axial loads are concluded relatively more challenging for both the sealing and strength of the joint. Higher magnitudes of loads and frequencies are also observed more challenging to the joints performance.

Strain-rate effect on initial crush stress of irregular honeycomb under dynamic loading and its deformation mechanism

Science.gov (United States)

Wang, Peng; Zheng, Zhijun; Liao, Shenfei; Yu, Jilin

2018-02-01

The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored. The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.

Vortex-induced dynamic loads on a non-spinning volleyball

Science.gov (United States)

Qing-ding, Wei; Rong-sheng, Lin; Zhi-jie, Liu

1988-09-01

An experiment on vortex-induced dynamic loads on a non-spinning Volleyball was conducted in a wind tunnel. The flow past the Volleyball was visualized, and the aerodynamic load was measured by use of a strain gauge balance. The separation on the Volleyball was measured with hot-film. The experimental results suggest that under the action of an unstable tail vortex system the separation region is changeable, and that the fluctuation of drag and lateral forces is the same order of magnitude as the mean drag, no matter whether the seam of the Volleyball is symmetric or asymmetric, with regard to the flow. Based on the experimental data a numerical simulation of Volleyball swerve motion was made.

Dynamic loads during failure risk assessment of bridge crane structures

Science.gov (United States)

Gorynin, A. D.; Antsev, V. Yu; Shaforost, A. N.

2018-03-01

The paper presents the method of failure risk assessment associated with a bridge crane metal structure at the design stage. It also justifies the necessity of taking into account dynamic loads with regard to the operational cycle of a bridge crane during failure risk assessment of its metal structure.

Dynamic modelling of heavy metals - time scales and target loads

NARCIS (Netherlands)

Posch, M.; Vries, de W.

2009-01-01

Over the past decade steady-state methods have been developed to assess critical loads of metals avoiding long-term risks in view of food quality and eco-toxicological effects on organisms in soils and surface waters. However, dynamic models are needed to estimate the times involved in attaining a

Damage propagation in a masonry arch subjected to slow cyclic and dynamic loadings

Directory of Open Access Journals (Sweden)

J. Toti

2014-07-01

Full Text Available In the present work, the damage propagation of a masonry arch induced by slow cyclic and dynamic loadings is studied. A two-dimensional model of the arch is proposed. A nonlocal damage-plastic constitutive law is adopted to reproduce the hysteretic characteristics of the masonry material, subjected to cyclic static loadings or to harmonic dynamic excitations. In particular, the adopted cohesive model is able to take into account different softening laws in tension and in compression, plastic strains, stiffness recovery and loss due to crack closure and reopening. The latter effect is an unavoidable feature for realistically reproducing hysteretic cycles. In the studied case, an inverse procedure is used to calibrate the model parameters. Then, nonlinear static and dynamic responses of the masonry arch are described together with damage propagation paths.

Two Stage Secure Dynamic Load Balancing Architecture for SIP Server Clusters

Directory of Open Access Journals (Sweden)

G. Vennila

2014-08-01

Full Text Available Session Initiation Protocol (SIP is a signaling protocol emerged with an aim to enhance the IP network capabilities in terms of complex service provision. SIP server scalability with load balancing has a greater concern due to the dramatic increase in SIP service demand. Load balancing of session method (request/response and security measures optimizes the SIP server to regulate of network traffic in Voice over Internet Protocol (VoIP. Establishing a honeywall prior to the load balancer significantly reduces SIP traffic and drops inbound malicious load. In this paper, we propose Active Least Call in SIP Server (ALC_Server algorithm fulfills objectives like congestion avoidance, improved response times, throughput, resource utilization, reducing server faults, scalability and protection of SIP call from DoS attacks. From the test bed, the proposed two-tier architecture demonstrates that the ALC_Server method dynamically controls the overload and provides robust security, uniform load distribution for SIP servers.

Pipe rupture and steam/water hammer design loads for dynamic analysis of piping systems

International Nuclear Information System (INIS)

Strong, B.R. Jr.; Baschiere, R.J.

1978-01-01

The design of restraints and protection devices for nuclear Class I and Class II piping systems must consider severe pipe rupture and steam/water hammer loadings. Limited stress margins require that an accurate prediction of these loads be obtained with a minimum of conservatism in the loads. Methods are available currently for such fluid transient load development, but each method is severely restricted as to the complexity and/or the range of fluid state excursions which can be simulated. This paper presents a general technique for generation of pipe rupture and steam/water hammer design loads for dynamic analysis of nuclear piping systems which does not have the limitations of existing methods. Blowdown thrust loadings and unbalanced piping acceleration loads for restraint design of all nuclear piping systems may be found using this method. The technique allows the effects of two-phase distributed friction, liquid flashing and condensation, and the surrounding thermal and mechanical equipment to be modeled. A new form of the fluid momentum equation is presented which incorporates computer generated fluid acceleration histories by inclusion of a geometry integral termed the 'force equivalent area' (FEA). The FEA values permit the coupling of versatile thermal-hydraulic programs to piping dynamics programs. Typical applications of the method to pipe rupture problems are presented and the resultant load histories compared with existing techniques. (Auth.)

A simplified model of dynamic interior cooling load evaluation for office buildings

International Nuclear Information System (INIS)

Ding, Yan; Zhang, Qiang; Wang, Zhaoxia; Liu, Min; He, Qing

2016-01-01

Highlights: • The core interior disturbance was determined by principle component analysis. • Influences of occupants on cooling load should be described using time series. • A simplified model was built to evaluate dynamic interior building cooling load. - Abstract: Predicted cooling load is a valuable tool for assessing the operation of air-conditioning systems. Compared with exterior cooling load, interior cooling load is more unpredictable. According to principle components analysis, occupancy was proved to be a typical factor influencing interior cooling loads in buildings. By exploring the regularity of interior disturbances in an office building, a simplified evaluation model for interior cooling load was established in this paper. The stochastic occupancy rate was represented by a Markov transition model. Equipment power, lighting power and fresh air were all related to occupancy rate based on time sequence. The superposition of different types of interior cooling loads was also considered in the evaluation model. The error between the evaluation results and measurement results was found to be lower than 10%. In reference to the cooling loads calculated by the traditional design method and area-based method in case study office rooms, the evaluated cooling loads were suitable for operation regulation.

Dynamic characterization and modeling of magneto-rheological elastomers under compressive loadings

International Nuclear Information System (INIS)

Koo, Jeong-Hoi; Khan, Fazeel; Jang, Dong-Doo; Jung, Hyung-Jo

2010-01-01

The primary goal of the research reported in this paper has been to characterize and model the compression properties of magneto-rheological elastomers (MREs). MRE samples were fabricated by curing a two-component elastomer resin with 30% content of 10 µm sized iron particles by volume. In order to vary the magnetic field during compressive testing, a test fixture was designed and fabricated in which two permanent magnets could be variably positioned on either side of the specimen. Changing the distance between the magnets of the fixture allowed the strength of the magnetic field passing uniformly through the sample to be varied. Using this test setup and a dynamic test frame, a series of compression tests of MRE samples were performed, by varying the magnetic field and the frequency of loading. The results show that the MR effect (per cent increase in the material 'stiffness') increases as the magnetic field increases and the loading frequency increases within the range of the magnetic field and input frequency considered in this study. Furthermore, a phenomenological model was developed to capture the dynamic behaviors of the MREs under compression loadings. (technical note)

Discontinuity effects in dynamically loaded tilting pad journal bearings

DEFF Research Database (Denmark)

Thomsen, Kim; Klit, Peder; Vølund, Anders

2011-01-01

This paper describes two discontinuity effects that can occur when modelling radial tilting pad bearings subjected to high dynamic loads. The first effect to be treated is a pressure build-up discontinuity effect. The second effect is a contact-related discontinuity that disappears when a contact...... force is included in the theoretical model. Methods for avoiding the pressure build-up discontinuity effect are proposed....

Infrared Thermographic Diagnosis Mechanism for Fault Detection of Ball Bearing under Dynamic Loading Conditions

International Nuclear Information System (INIS)

Seo, Jin Ju; Yoon, Hanvit; Kim, Dong Yeon; Hong, Dong Pyo; Kim, Won Tae

2011-01-01

Fault detection for dynamic loading conditions of rotational machineries was considered from the contactless, non-destructive infrared thermographic method, rather than the traditional diagnosis method. In this paper, by applying a rotating deep-grooved ball bearing, passive thermographic experiment was performed as an alternative way proceeding the traditional fault monitoring. In addition, the thermographic experiments were compared with the vibration spectrum analysis to evaluate the efficiency of the proposed method. Based on the results, it was concluded the temperature characteristics of the ball bearing under dynamic loading conditions were analyzed thoroughly

In vitro evaluation of stiffness and load sharing in a two-level corpectomy: comparison of static and dynamic cervical plates.

Science.gov (United States)

Fogel, Guy R; Li, Zhenyu; Liu, Weiqiang; Liao, Zhenhua; Wu, Jia; Zhou, Wenyu

2010-05-01

Anterior cervical plating has been accepted in corpectomy and fusion of the cervical spine. Constrained plates were criticized for stress shielding that may lead to subsidence and pseudarthrosis. A dynamic plate allows load sharing as the graft subsides. Ideally, the dynamic plate design should maintain adequate stiffness of the construct while providing a reasonable load sharing with the strut graft. The purpose of the study was to compare dynamic and static plate kinematics with graft subsidence. The study designed was an in vitro biomechanical study in a porcine cervical spine model. Twelve spines were initially tested in intact condition with 20-N axial load in 15 degrees of flexion and extension range of motion (ROM). Then, a two-level corpectomy was created in all specimens with spines randomized to receive either a static or dynamic plate. The spines were retested under identical conditions with optimal length and undersized graft. Range of motion and graft loading were analyzed with a one-way analysis of variance (p<.05). Both plates significantly limited ROM compared with the intact spine in both graft length conditions. In extension graft, load was significantly higher (p=.001) in the static plate with optimal length, and in flexion, there was a significant loss of graft load (p=.0004). In flexion, the dynamic plate with undersized graft demonstrated significantly more load sustained (p=.0004). Both plates reasonably limited the ROM of the corpectomy. The static plate had significantly higher graft loads in extension and significant loss of graft load in flexion, whereas the dynamic plate maintained a reasonable graft load in ROM even when graft contact was imperfect. Copyright 2010 Elsevier Inc. All rights reserved.

Dynamic load indicators for take-off-landing sequence in blocks and attacks of elite female volleyball players.

Science.gov (United States)

Kabaciński, Jarosław; Dworak, Lechosław Bogdan; Murawa, Michał; Rzepnicka, Agata

2016-01-01

Dynamic loads during landings determined by the ground reaction forces (GRFs) may elaborate internal loads and increase the risk of overload knee injuries as a result of performing volleyball jumps many times. The study dealt with a biomechanical assessment of dynamic load indicators in female volleyball players for the motion sequence of take-off-landing in blocks and attacks. Twelve professional female volleyball players participated in the study. Blocks and attacks were filmed by two cameras. GRFs vs. time graphs were recorded with the use of a force platform. Values of dynamic load indicators in terms of the relations of peak of vertical component of GRF, build-up index of this force (BIF), and power output (P) during landing to the vGRF, BIF and P during take-off (L/T) were calculated. The statistically significant ( p volleyball players.

Influence of foundation mass and surface roughness on dynamic response of beam on dynamic foundation subjected to the moving load

Science.gov (United States)

Tran Quoc, Tinh; Khong Trong, Toan; Luong Van, Hai

2018-04-01

In this paper, Improved Moving Element Method (IMEM) is used to analyze the dynamic response of Euler-Bernoulli beam structures on the dynamic foundation model subjected to the moving load. The effects of characteristic foundation model parameters such as Winkler stiffness, shear layer based on the Pasternak model, viscoelastic dashpot and characteristic parameter of mass on foundation. Beams are modeled by moving elements while the load is fixed. Based on the principle of the publicly virtual balancing and the theory of moving element method, the motion differential equation of the system is established and solved by means of the numerical integration based on the Newmark algorithm. The influence of mass on foundation and the roughness of the beam surface on the dynamic response of beam are examined in details.

The dynamic response and perturbation of magnetic field vector of orthotropic cylinders under various shock loads

International Nuclear Information System (INIS)

Dai, H.L.; Wang, X.

2006-01-01

In this paper, an analytical method is introduced to solve the problem for the dynamic stress-focusing and centred-effect of perturbation of the magnetic field vector in orthotropic cylinders under thermal and mechanical shock loads. Analytical expressions for the dynamic stresses and the perturbation of the magnetic field vector are obtained by means of finite Hankel transforms and Laplace transforms. The response histories of dynamic stresses and the perturbation of the field vector are also obtained. In practical examples, the dynamic focusing effect on both magnetoelastic stress and perturbation of the axial magnetic field vector in an orthotropic cylinder subjected to various shock loads is presented and discussed

Flight Loads Prediction of High Aspect Ratio Wing Aircraft Using Multibody Dynamics

Directory of Open Access Journals (Sweden)

Michele Castellani

2016-01-01

Full Text Available A framework based on multibody dynamics has been developed for the static and dynamic aeroelastic analyses of flexible high aspect ratio wing aircraft subject to structural geometric nonlinearities. Multibody dynamics allows kinematic nonlinearities and nonlinear relationships in the forces definition and is an efficient and promising methodology to model high aspect ratio wings, which are known to be prone to structural nonlinear effects because of the high deflections in flight. The multibody dynamics framework developed employs quasi-steady aerodynamics strip theory and discretizes the wing as a series of rigid bodies interconnected by beam elements, representative of the stiffness distribution, which can undergo arbitrarily large displacements and rotations. The method is applied to a flexible high aspect ratio wing commercial aircraft and both trim and gust response analyses are performed in order to calculate flight loads. These results are then compared to those obtained with the standard linear aeroelastic approach provided by the Finite Element Solver Nastran. Nonlinear effects come into play mainly because of the need of taking into account the large deflections of the wing for flight loads computation and of considering the aerodynamic forces as follower forces.

Study on the Flare Load Estimation of the Deethanizer using Dynamic Simulation

Energy Technology Data Exchange (ETDEWEB)

Park, Kyungtae; Won, Wangyun [GS EC, Seoul (Korea, Republic of); Shin, Dongil [Myongji University, Yongin (Korea, Republic of)

2014-10-15

A flare system is a very important system that crucially affects on the process safety in chemical plants. If a flare system is designed too small, it cannot prevent catastrophic accidents of a chemical plant. On the other hand, if a flare system is designed too large, it will waste resources. Therefore, reasonable relief load estimation has been a crucial issue in the industry. American Petroleum Institute (API) suggests basic guidelines for relief load estimation, and a lot of engineering companies have developed their own relief load estimation methods that use an unbalanced heat and material method. However, these methods have to involve lots of conservative assumptions that lead to an overestimation of relief loads. In this study, the new design procedure for a flare system based on dynamic simulation was proposed in order to avoid the overestimation of relief loads. The relief load of a deethanizer process was tested to verify the performance of the proposed design procedure.

Feasibility of Applying Active Lubrication to Dynamically Loaded Fluid Film Bearings

DEFF Research Database (Denmark)

Estupinan, Edgar Alberto; Santos, Ilmar

2009-01-01

The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...... of this study is on the analysis of main crankshaft bearings, where the conventional hydrodynamic lubrication is modified by injecting oil at actively controllable pressures, through orifices circumferentially located along the bearing surface....

Dynamic analysis of maritime gasbag-type floating bridge subjected to moving loads

Directory of Open Access Journals (Sweden)

Huan-huan Wang

2016-03-01

Full Text Available This paper studied the dynamic response of a new gasbag-type floating bridge under the effect of a moving load. The arbitrary Lagrangian-Eulerian (ALE method was used to simulate the movement of seawater and air, and the penalty-based method was used to study the coupling between gasbags and fluid. A three-dimensional finite element model of the floating bridge was established, and the numerical model was verified by comparing with the experimental results. In order to prevent resonance, the natural frequencies and flexural mode shapes were analyzed. Based on the initial state analysis, the dynamic responses of the floating bridge subjected to different moving loads were investigated. Vertical displacements and radial deformations of gasbags under different loads were compared, and principal stress distributions of gasbags were researched while driving. The hinge forces between adjacent modules were calculated to ensure the connection strength. Besides, the floating bridge under wave impacting was analyzed. Those results can provide references for the analysis and design of this new floating bridge.

Analysis of the Dynamic Response in Blast-Loaded CFRP-Strengthened Metallic Beams

Directory of Open Access Journals (Sweden)

Zhenyu Wang

2013-01-01

Full Text Available Carbon fiber-reinforced polymer composites (CFRPs are good candidates in enhancing the blast resistant performance of vulnerable public buildings and in reinforcing old buildings. The use of CFRP in retrofitting and strengthening applications is traditionally associated with concrete structures. Nevertheless, more recently, there has been a remarkable aspiration in strengthening metallic structures and components using CFRP. This paper presents a relatively simple analytical solution for the deformation and ultimate strength calculation of hybrid metal-CFRP beams when subjected to pulse loading, with a particular focus on blast loading. The analytical model is based on a full interaction between the metal and the FRP and is capable of producing reasonable results in a dynamic loading scenario. A nonlinear finite element (FE model is also developed to reveal the full dynamic behavior of the CFRP-epoxy-steel hybrid beam, considering the detailed effects, that is, large strains, high strain rates in metal, and different failure modes of the hybrid beam. Experimental results confirm the analytical and the FE results and show a strong correlation.

Dynamic Load Balancing Based on Constrained K-D Tree Decomposition for Parallel Particle Tracing

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jiang; Guo, Hanqi; Yuan, Xiaoru; Hong, Fan; Peterka, Tom

2018-01-01

Particle tracing is a fundamental technique in flow field data visualization. In this work, we present a novel dynamic load balancing method for parallel particle tracing. Specifically, we employ a constrained k-d tree decomposition approach to dynamically redistribute tasks among processes. Each process is initially assigned a regularly partitioned block along with duplicated ghost layer under the memory limit. During particle tracing, the k-d tree decomposition is dynamically performed by constraining the cutting planes in the overlap range of duplicated data. This ensures that each process is reassigned particles as even as possible, and on the other hand the new assigned particles for a process always locate in its block. Result shows good load balance and high efficiency of our method.

Nonlinear dynamic response of electro-thermo-mechanically loaded piezoelectric cylindrical shell reinforced with BNNTs

International Nuclear Information System (INIS)

Yang, J H; Yang, J; Kitipornchai, S

2012-01-01

This paper presents an investigation on the nonlinear dynamic response of piezoelectric cylindrical shells reinforced with boron nitride nanotubes (BNNTs) under a combined axisymmetric electro-thermo-mechanical loading. By employing the classical Donnell shell theory, the von Kármán–Donnell kinematic relationship, and a piezo-elastic constitutive law including thermal effects, the nonlinear governing equations of motion of the shell are derived through the Reissner variational principle. The finite difference method and a time-integration scheme are used to obtain the nonlinear dynamic response of the BNNT-reinforced piezoelectric shell. A parametric study is conducted, showing the effects of geometrically nonlinear deformation, applied voltage, temperature change, mechanical load, BNNT volume fraction and boundary conditions on the nonlinear dynamic response. (paper)

On the equivalent static loads approach for dynamic response structural optimization

DEFF Research Database (Denmark)

Stolpe, Mathias

2014-01-01

The equivalent static loads algorithm is an increasingly popular approach to solve dynamic response structural optimization problems. The algorithm is based on solving a sequence of related static response structural optimization problems with the same objective and constraint functions...... as the original problem. The optimization theoretical foundation of the algorithm is mainly developed in Park and Kang (J Optim Theory Appl 118(1):191–200, 2003). In that article it is shown, for a certain class of problems, that if the equivalent static loads algorithm terminates then the KKT conditions...

Modeling the dynamic stiffness of cracked reinforced concrete beams under low-amplitude vibration loads

Science.gov (United States)

Xu, Tengfei; Castel, Arnaud

2016-04-01

In this paper, a model, initially developed to calculate the stiffness of cracked reinforced concrete beams under static loading, is used to assess the dynamic stiffness. The model allows calculating the average inertia of cracked beams by taking into account the effect of bending cracks (primary cracks) and steel-concrete bond damage (i.e. interfacial microcracks). Free and forced vibration experiments are used to assess the performance of the model. The respective influence of bending cracks and steel-concrete bond damage on both static and dynamic responses is analyzed. The comparison between experimental and simulated deflections confirms that the effects of both bending cracks and steel-concrete bond loss should be taken into account to assess reinforced concrete stiffness under service static loading. On the contrary, comparison of experimental and calculated dynamic responses reveals that localized steel-concrete bond damages do not influence significantly the dynamic stiffness and the fundamental frequency.

Excellent plasticity of a new Ti-based metallic glass matrix composite upon dynamic loading

Energy Technology Data Exchange (ETDEWEB)

Wu, R.F. [Laboratory of Applied Physics and Mechanics of Advanced Materials, College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China); Jiao, Z.M. [Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Wang, Y.S.; Wang, Z. [Laboratory of Applied Physics and Mechanics of Advanced Materials, College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Wang, Z.H.; Ma, S.G. [Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Qiao, J.W., E-mail: qiaojunwei@gmail.com [Laboratory of Applied Physics and Mechanics of Advanced Materials, College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China)

2016-11-20

Quasi-static and dynamic compressive properties of in-situ Ti{sub 60}Zr{sub 14}V{sub 12}Cu{sub 4}Be{sub 10} bulk metallic glass matrix composites containing ductile dendrites were investigated. Upon quasi-static compressive loading, the composite exhibits a high fracture strength of ~2,600 MPa, combined with a considerable plasticity of ~40% at room temperature. However, upon dynamic loading, an excellent plasticity of ~16% can be obtained due to the abundant dislocations and severe lattice distortions within dendrites and multiplication of shear bands within the glass matrix analyzed by transmission-electron microscopy. A constitutive relationship is obtained by Johnson-Cook plasticity model, which is employed to model the dynamic flow stress behavior. In addition, under dynamic compression, the adiabatic temperature rise increases with increasing strain rates, resulting in that the softening effect within the glass matrix is obviously enhanced during deformation.

Evaluation of resilient abutment components on measured strain using dynamic loading conditions.

Science.gov (United States)

Morton, D; Stanford, C M; Aquilino, S A

1998-07-01

Factors that affect transmission of strain from prostheses to bone may affect the long-term success of loaded implants. Current in vitro models are theoretically predictive (finite element modeling) or facsimile (photoelastic) in nature. A more clinically relevant in vitro model for strain evaluation should be investigated. This study attempted: (1) to validate a human cadaver bone model for vitro measurement of cortical bone strain, and (2) to evaluate the effect on cortical strain measurements of a resilient plastic component incorporated within a titanium implant in response to variable dynamic loading. Two IMZ (Interpore International) abutment alternatives were used: the titanium Abutment Complete and the polyoxymethylene Intra-mobile Element. The model system consisted of two implants placed in unfixed human cadaver ulna bone to simulate an implant bound edentulous region. Four biaxial rosette strain gauges simultaneously recorded cortical bone strain immediately mesial and distal to each implant. During experimentation a simulated prosthetic framework supported by either titanium or polyoxymethylene abutments was dynamically loaded 6 min from the terminal abutment along a cantilever extension. Cyclic nominal peak loads were applied with a materials testing machine at 20-N intervals from 20 to 200 N at a crosshead speed of 5 mm/minute. The protocol allowed frequency of load application to vary. A Newtonian linear correlation (r2 > or = 0.98) between load application and strain output was determined for each gauge position except for the terminal gauge located opposite the cantilever. Cortical strains recorded were within reported physiologic ranges involved in bone modeling and remodeling. Further, the polyoxymethylene abutment components did not result in reduction of peak microstrain at any gauge position. The Intra-mobile Element abutments, however, did increase the time required to complete 10 loading cycles when compared with the titanium Abutment

Wake Influence on Dynamic Load Characteristics of Offshore Floating Wind Turbines

DEFF Research Database (Denmark)

Jeon, Minu; Lee, Soogab; Kim, Taeseong

2016-01-01

Because the flow conditions of an offshore floating wind turbine and onshore fixed wind turbine differ, it is debatable whether the aerodynamic load predictions of an offshore floating wind turbine using the conventional blade-element momentum theory, which does not consider the dynamic wake effe...

Dynamic analysis of reactor containment subjected to aircraft impact loading

International Nuclear Information System (INIS)

Li Xiaotian; He Shuyan

2004-01-01

In this paper, dynamic character of reactor containment subjected to aircraft impact loading is analyzed with MSC.DYTRAN program. The displacement of concrete and velocity curve of airplane is obtained. The results of the different material model are compared with empirical formula. It is concluded that reasonable result can be obtained using cap model for concrete

Influence of dynamic compressive loading on the in vitro degradation behavior of pure PLA and Mg/PLA composite.

Science.gov (United States)

Li, Xuan; Qi, Chenxi; Han, Linyuan; Chu, Chenglin; Bai, Jing; Guo, Chao; Xue, Feng; Shen, Baolong; Chu, Paul K

2017-12-01

The effects of dynamic compressive loading on the in vitro degradation behavior of pure poly-lactic acid (PLA) and PLA-based composite unidirectionally reinforced with micro-arc oxidized magnesium alloy wires (Mg/PLA) are investigated. Dynamic compressive loading is shown to accelerate degradation of pure PLA and Mg/PLA. As the applied stress is increased from 0.1MPa to 0.9MPa or frequency from 0.5Hz to 2.5Hz, the overall degradation rate goes up. After immersion for 21days at 0.9MPa and 2.5Hz, the bending strength retention of the composite and pure PLA is 60.1% and 50%, respectively. Dynamic loading enhances diffusion of small acidic molecules resulting in significant pH decrease in the immersion solution. The synergistic reaction between magnesium alloy wires and PLA in the composite is further clarified by electrochemical tests. The degradation behavior of the pure PLA and PLA matrix in the composite under dynamic conditions obey the first order degradation kinetics and a numerical model is postulated to elucidate the relationship of the bending strength, stress, frequency, and immersion time under dynamic conditions. We systematically study the influence of dynamic loading on the degradation behavior of pure PLA and Mg/PLA. Dynamic compressive loading is shown to accelerate degradation of pure PLA and Mg/PLA. The synergistic reaction between magnesium alloy wires and PLA in the composite is firstly clarified by electrochemical tests. The degradation behavior of the pure PLA and PLA matrix in the composite under dynamic conditions obey the first order degradation kinetics. Then, a numerical model is postulated to elucidate the relationship of the bending strength, stress, frequency, and immersion time under dynamic conditions. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Investigation of switch designs for the dynamic load current multiplier scheme on the SPHYNX microsecond linear transformer driver

International Nuclear Information System (INIS)

Maysonnave, T.; Bayol, F.; Demol, G.; Almeida, T. d'; Lassalle, F.; Morell, A.; Grunenwald, J.; Chuvatin, A.S.; Pecastaing, L.; De Ferron, A.S.

2014-01-01

SPHINX is a microsecond linear transformer driver LTD, used essentially for implosion of Z-pinch loads in direct drive mode. It can deliver a 6-MA current pulse within 800 ns into a Z-pinch load. The dynamic load current multiplier concept enables the current pulse to be modified by increasing its amplitude while reducing its rise time before being delivered to the load. This compact system is made up of concentric electrodes (auto transformer), a dynamic flux extruder (cylindrical wire array), a vacuum convolute (eight post-holes), and a vacuum closing switch, which is the key component of the system. Several different schemes are investigated for designing a vacuum switch suitable for operating the dynamic load current multiplier on the SPHINX generator for various applications, including isentropic compression experiments and Z-pinch radiation effects studies. In particular, the design of a compact vacuum surface switch and a multichannel vacuum switch, located upstream of the load are studied. Electrostatic simulations supporting the switch designs are presented along with test bed experiments. Initial results from shots on the SPHINX driver are also presented. (authors)

Effect of random microstructure on crack propagation in cortical bone tissue under dynamic loading

International Nuclear Information System (INIS)

Gao, X; Li, S; Adel-Wahab, A; Silberschmidt, V

2013-01-01

A fracture process in a cortical bone tissue depends on various factors, such as bone loss, heterogeneous microstructure, variation of its material properties and accumulation of microcracks. Therefore, it is crucial to comprehend and describe the effect of microstructure and material properties of the components of cortical bone on crack propagation in a dynamic loading regime. At the microscale level, osteonal bone demonstrates a random distribution of osteons imbedded in an interstitial matrix and surrounded by a thin layer known as cement line. Such a distribution of osteons can lead to localization of deformation processes. The global mechanical behavior of bone and the crack-propagation process are affected by such localization under external loads. Hence, the random distribution of microstructural features plays a key role in the fracture process of cortical bone. The purpose of this study is two-fold: firstly, to develop two-dimensional microstructured numerical models of cortical bone tissue in order to examine the interaction between the propagating crack and bone microstructure using an extended finite-element method under both quasi-static and dynamic loading conditions; secondly, to investigate the effect of randomly distributed microstructural constituents on the crack propagation processes and crack paths. The obtained results of numerical simulations showed the influence of random microstructure on the global response of bone tissue at macroscale and on the crack-propagation process for quasi-static and dynamic loading conditions

Dynamic Load on a Pipe Caused by Acetylene Detonations – Experiments and Theoretical Approaches

Directory of Open Access Journals (Sweden)

Axel Sperber

1999-01-01

Full Text Available The load acting on the wall of a pipe by a detonation, which is travelling through, is not yet well characterized. The main reasons are the limited amount of sufficiently accurate pressure time history data and the requirement of considering the dynamics of the system. Laser vibrometry measurements were performed to determine the dynamic response of the pipe wall on a detonation. Different modelling approaches were used to quantify, theoretically, the radial displacements of the pipe wall. There is good agreement between measured and predicted values of vibration frequencies and the propagation velocities of transverse waves. Discrepancies mainly due to wave propagation effects were found in the amplitudes of the radial velocities. They might be overcome by the use of a dynamic load factor or improved modelling methods.

Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

Science.gov (United States)

Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason R.; Nash, Roxanne E.; Sinka, Joseph; Bloomberg, Jacob J.

2009-01-01

Maximal power output occurs when subjects perform ballistic exercises using loads of 30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of

Electromechanical responses of a long piezoelectric tube subjected to dynamic loading

International Nuclear Information System (INIS)

Huang, Jin H; Shiah, Y C; Lee, Bing Jean

2008-01-01

This paper deals with the fully coupled electromechanical response of a long piezoelectric tube subjected to periodic excitation loads. By adopting the variation approach for generalized loading conditions and utilizing Hamilton's principle, the governing differential equations are described in this paper. For studying the direct and converse effect of the piezoelectric tube, the equations of motion are then solved to give exact solutions corresponding to different boundary conditions prescribed for the tube functioning as sensors or actuators. For numerical illustrations of our analysis, a long tube made of polyvinylidene difluoride is investigated for its dynamic responses under different harmonic excitation loads. Contributing to the development of novel acousto-optic, actuator and sensor devices, this work may be extended to investigating the electromechanical responses of piezoelectric coatings on optical fibres

Composite slab behavior and strength analysis under static and dynamic loads

Directory of Open Access Journals (Sweden)

Florin Radu HARIGA

2012-07-01

Full Text Available Steel-framed buildings are typically constructed using steel-deck-reinforced concrete floor slabs. The in-plane (or diaphragm strength and stiffness of the floor system are frequently utilized in the lateral load-resisting system design. This paper presents the results of an experimental research program in which four full size composite diaphragms were vertically loaded to the limit state, under static or dynamic loads. Two test specimens were provided with longitudinal steel-deck ribs, and the other two specimens with cross steel-deck ribs. Typical composite diaphragm limit states are described, and the controlling limit state for each of the full size tests is indicated. The interaction effects between the reinforced concrete slab and the steel girder on the composite slab strength and stiffness were mainly studied.

Static and dynamic load-balancing strategies for parallel reservoir simulation

International Nuclear Information System (INIS)

Anguille, L.; Killough, J.E.; Li, T.M.C.; Toepfer, J.L.

1995-01-01

Accurate simulation of the complex phenomena that occur in flow in porous media can tax even the most powerful serial computers. Emergence of new parallel computer architectures as a future efficient tool in reservoir simulation may overcome this difficulty. Unfortunately, major problems remain to be solved before using parallel computers commercially: production serial programs must be rewritten to be efficient in parallel environments and load balancing methods must be explored to evenly distribute the workload on each processor during the simulation. This study implements both a static load-balancing algorithm and a receiver-initiated dynamic load-sharing algorithm to achieve high parallel efficiencies on both the IBM SP2 and Intel IPSC/860 parallel computers. Significant speedup improvement was recorded for both methods. Further optimization of these algorithms yielded a technique with efficiencies as high as 90% and 70% on 8 and 32 nodes, respectively. The increased performance was the result of the minimization of message-passing overhead

Numerical modelling of closed-cell aluminium foam under dynamic loading

Science.gov (United States)

Hazell, Paul; Kader, M. A.; Islam, M. A.; Escobedo, J. P.; Saadatfar, M.

2015-06-01

Closed-cell aluminium foams are extensively used in aerospace and automobile industries. The understanding of their behaviour under impact loading conditions is extremely important since impact problems are directly related to design of these engineering structures. This research investigates the response of a closed-cell aluminium foam (CYMAT) subjected to dynamic loading using the finite element software ABAQUS/explicit. The aim of this research is to numerically investigate the material and structural properties of closed-cell aluminium foam under impact loading conditions with interest in shock propagation and its effects on cell wall deformation. A μ-CT based 3D foam geometry is developed to simulate the local cell collapse behaviours. A number of numerical techniques are applied for modelling the crush behaviour of aluminium foam to obtain the more accurate results. The simulation results are compared with experimental data. Comparison of the results shows a good correlation between the experimental results and numerical predictions.

Electrical load modeling

Energy Technology Data Exchange (ETDEWEB)

Valgas, Helio Moreira; Pinto, Roberto del Giudice R.; Franca, Carlos [Companhia Energetica de Minas Gerais (CEMIG), Belo Horizonte, MG (Brazil); Lambert-Torres, Germano; Silva, Alexandre P. Alves da; Pires, Robson Celso; Costa, Junior, Roberto Affonso [Escola Federal de Engenharia de Itajuba, MG (Brazil)

1994-12-31

Accurate dynamic load models allow more precise calculations of power system controls and stability limits, which are critical mainly in the operation planning of power systems. This paper describes the development of a computer program (software) for static and dynamic load model studies using the measurement approach for the CEMIG system. Two dynamic load model structures are developed and tested. A procedure for applying a set of measured data from an on-line transient recording system to develop load models is described. (author) 6 refs., 17 figs.

Dynamic loads on reactor vessel components by low pressure waves

International Nuclear Information System (INIS)

Benkert, J.; Mika, C.; Stegemann, D.; Valero, M.

1978-01-01

Starting from the conservation theorems for mass and impulses the code DRUWE has been developed enabling the calculation of dynamic loads of the reactor shell on the basis of simplified assumptions for the first period shortly after rupture. According to the RSK-guidelines it can be assumed that the whole weld size is opened within 15 msec. This time-dependent opening of the fractured plane can be taken into account in the computer program. The calculation is composed in a way that for a reactor shell devided into cross and angle sections the local, chronological pressure and strength curves, the total dynamic load as well as the moments acting on the fastenings of the reactor shell can be calculated. As input data only geometrical details concerning the concept of the pressure vessel and its components as well as the effective subcooling of the fluid are needed. By means of several parameters the program can be operated in a way that the results are available in form of listings or diagrams, respectively, but also as card pile for further examinations, e.g. strength analysis. (orig./RW) [de

Prediction-based dynamic load-sharing heuristics

Science.gov (United States)

Goswami, Kumar K.; Devarakonda, Murthy; Iyer, Ravishankar K.

1993-01-01

The authors present dynamic load-sharing heuristics that use predicted resource requirements of processes to manage workloads in a distributed system. A previously developed statistical pattern-recognition method is employed for resource prediction. While nonprediction-based heuristics depend on a rapidly changing system status, the new heuristics depend on slowly changing program resource usage patterns. Furthermore, prediction-based heuristics can be more effective since they use future requirements rather than just the current system state. Four prediction-based heuristics, two centralized and two distributed, are presented. Using trace driven simulations, they are compared against random scheduling and two effective nonprediction based heuristics. Results show that the prediction-based centralized heuristics achieve up to 30 percent better response times than the nonprediction centralized heuristic, and that the prediction-based distributed heuristics achieve up to 50 percent improvements relative to their nonprediction counterpart.

Collapse mechanisms of metal foam matrix composites under static and dynamic loading conditions

Energy Technology Data Exchange (ETDEWEB)

Linul, Emanoil, E-mail: emanoil.linul@upt.ro [Department of Mechanics and Strength of Materials, Politehnica University of Timisoara, 1 Mihai Viteazu Avenue, 300 222 Timisoara (Romania); Marsavina, Liviu [Department of Mechanics and Strength of Materials, Politehnica University of Timisoara, 1 Mihai Viteazu Avenue, 300 222 Timisoara (Romania); Kováčik, Jaroslav [Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Dúbravská cesta 9, 845 13 Bratislava (Slovakia)

2017-04-06

The collapse mechanisms of metal foam matrix composites under static and dynamic loading conditions were experimentally and analytically investigated. Closed-cell aluminium foam AlSi10 with 325±10 kg/m{sup 3} density was used as core material, while stainless-steel-mesh is the faces materials. Prior to characterizing the composite sandwich structure, the stainless steel mesh face material and closed-cell aluminium foam were characterized by tensile testing and compression testing, respectively. Experimental tests were performed on sandwich beams using both High Speed Camera and Digital Image Correlation system for strain distribution. All experimental tests were performed at room temperature with constant crosshead speed of 1.67×10{sup −4} m/s for static tests and 2 m/s impact loading speed for dynamic tests. Two main deformation behaviours of investigated metal foam matrix composites were observed following post-failure collapse: face failure and core shear. It was showed that the initiation, propagation and interaction of failure modes depend on the type of loading, constituent material properties and geometrical parameters.

Computer simulation of yielding supports under static and short-term dynamic load

Directory of Open Access Journals (Sweden)

Kumpyak Oleg

2018-01-01

Full Text Available Dynamic impacts that became frequent lately cause large human and economic losses, and their prevention methods are not always effective and reasonable. The given research aims at studying the way of enhancing explosion safety of building structures by means of yielding supports. The paper presents results of numerical studies of strength and deformation property of yielding supports in the shape of annular tubes under static and short-term dynamic loading. The degree of influence of yielding supports was assessed taking into account three peculiar stages of deformation: elastic; elasto-plastic; and elasto-plastic with hardening. The methodology for numerical studies performance was described using finite element analysis with program software Ansys Mechanical v17.2. It was established that rigidity of yielding supports influences significantly their stress-strain state. The research determined that with the increase in deformable elements rigidity dependence between load and deformation of the support in elastic and plastic stages have linear character. Significant reduction of the dynamic response and increase in deformation time of yielding supports were observed due to increasing the plastic component. Therefore, it allows assuming on possibility of their application as supporting units in RC beams.

Dynamic analysis of Free-Piston Stirling Engine/Linear Alternator-load system-experimentally validated

Science.gov (United States)

Kankam, M. David; Rauch, Jeffrey S.; Santiago, Walter

1992-01-01

This paper discusses the effects of variations in system parameters on the dynamic behavior of the Free-Piston Stirling Engine/Linear Alternator (FPSE/LA)-load system. The mathematical formulations incorporate both the mechanical and thermodynamic properties of the FPSE, as well as the electrical equations of the connected load. A state-space technique in the frequency domain is applied to the resulting system of equations to facilitate the evaluation of parametric impacts on the system dynamic stability. Also included is a discussion on the system transient stability as affected by sudden changes in some key operating conditions. Some representative results are correlated with experimental data to verify the model and analytic formulation accuracies. Guidelines are given for ranges of the system parameters which will ensure an overall stable operation.

Evaluation of MOSTAS computer code for predicting dynamic loads in two bladed wind turbines

Science.gov (United States)

Kaza, K. R. V.; Janetzke, D. C.; Sullivan, T. L.

1979-01-01

Calculated dynamic blade loads were compared with measured loads over a range of yaw stiffnesses of the DOE/NASA Mod-O wind turbine to evaluate the performance of two versions of the MOSTAS computer code. The first version uses a time-averaged coefficient approximation in conjunction with a multi-blade coordinate transformation for two bladed rotors to solve the equations of motion by standard eigenanalysis. The second version accounts for periodic coefficients while solving the equations by a time history integration. A hypothetical three-degree of freedom dynamic model was investigated. The exact equations of motion of this model were solved using the Floquet-Lipunov method. The equations with time-averaged coefficients were solved by standard eigenanalysis.

Dynamics of defect-loaded grain boundary under shear deformation in alpha iron

Science.gov (United States)

Yang, L.; Zhou, H. L.; Liu, H.; Gao, F.; Zu, X. T.; Peng, S. M.; Long, X. G.; Zhou, X. S.

2018-02-01

Two symmetric tilt grain boundaries (GBs) (Σ3〈110〉{112} and Σ11〈110〉{332}) in alpha iron were performed to investigate the dynamics of defect-loaded GBs under shear deformation. The results show that the loaded self-interstitial atoms (SIAs) reduce the critical stress of the coupled GB motion in the Σ3 GB, but increase the critical stress in the Σ11 GB. The loaded SIAs in the Σ3 GB easily form 〈111〉 clusters and remain in the bulk when the GB moves away. However, the SIAs move along with the Σ11 GB and combine with the vacancies in the bulk, leading to the defect self-healing. The helium (He) atoms loaded into the GBs significantly affect the coupled GB motion. Once He clusters emit interstitials, the Σ11 GB carries those interstitials away but the Σ3 does not. The loaded He atoms reduce the critical stress of the Σ3 GB, but increase the critical stress of the Σ11 GB.

Mechanical properties of stanene under uniaxial and biaxial loading: A molecular dynamics study

Energy Technology Data Exchange (ETDEWEB)

Mojumder, Satyajit [Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000 (Bangladesh); Amin, Abdullah Al [Department of Mechanical and Aerospace Engineering, Case western Reverse University, Cleveland, Ohio 44106 (United States); Islam, Md Mahbubul, E-mail: mmi122@psu.edu [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2015-09-28

Stanene, a graphene like two dimensional honeycomb structure of tin has attractive features in electronics application. In this study, we performed molecular dynamics simulations using modified embedded atom method potential to investigate mechanical properties of stanene. We studied the effect of temperature and strain rate on mechanical properties of α-stanene for both uniaxial and biaxial loading conditions. Our study suggests that with the increasing temperature, both the fracture strength and strain of the stanene decrease. Uniaxial loading in zigzag direction shows higher fracture strength and strain compared to the armchair direction, while no noticeable variation in the mechanical properties is observed for biaxial loading. We also found at a higher loading rate, material exhibits higher fracture strength and strain. These results will aid further investigation of stanene as a potential nano-electronics substitute.

A parallel 3D particle-in-cell code with dynamic load balancing

International Nuclear Information System (INIS)

Wolfheimer, Felix; Gjonaj, Erion; Weiland, Thomas

2006-01-01

A parallel 3D electrostatic Particle-In-Cell (PIC) code including an algorithm for modelling Space Charge Limited (SCL) emission [E. Gjonaj, T. Weiland, 3D-modeling of space-charge-limited electron emission. A charge conserving algorithm, Proceedings of the 11th Biennial IEEE Conference on Electromagnetic Field Computation, 2004] is presented. A domain decomposition technique based on orthogonal recursive bisection is used to parallelize the computation on a distributed memory environment of clustered workstations. For problems with a highly nonuniform and time dependent distribution of particles, e.g., bunch dynamics, a dynamic load balancing between the processes is needed to preserve the parallel performance. The algorithm for the detection of a load imbalance and the redistribution of the tasks among the processes is based on a weight function criterion, where the weight of a cell measures the computational load associated with it. The algorithm is studied with two examples. In the first example, multiple electron bunches as occurring in the S-DALINAC [A. Richter, Operational experience at the S-DALINAC, Proceedings of the Fifth European Particle Accelerator Conference, 1996] accelerator are simulated in the absence of space charge fields. In the second example, the SCL emission and electron trajectories in an electron gun are simulated

A parallel 3D particle-in-cell code with dynamic load balancing

Energy Technology Data Exchange (ETDEWEB)

Wolfheimer, Felix [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstr.8, 64283 Darmstadt (Germany)]. E-mail: wolfheimer@temf.de; Gjonaj, Erion [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstr.8, 64283 Darmstadt (Germany); Weiland, Thomas [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstr.8, 64283 Darmstadt (Germany)

2006-03-01

A parallel 3D electrostatic Particle-In-Cell (PIC) code including an algorithm for modelling Space Charge Limited (SCL) emission [E. Gjonaj, T. Weiland, 3D-modeling of space-charge-limited electron emission. A charge conserving algorithm, Proceedings of the 11th Biennial IEEE Conference on Electromagnetic Field Computation, 2004] is presented. A domain decomposition technique based on orthogonal recursive bisection is used to parallelize the computation on a distributed memory environment of clustered workstations. For problems with a highly nonuniform and time dependent distribution of particles, e.g., bunch dynamics, a dynamic load balancing between the processes is needed to preserve the parallel performance. The algorithm for the detection of a load imbalance and the redistribution of the tasks among the processes is based on a weight function criterion, where the weight of a cell measures the computational load associated with it. The algorithm is studied with two examples. In the first example, multiple electron bunches as occurring in the S-DALINAC [A. Richter, Operational experience at the S-DALINAC, Proceedings of the Fifth European Particle Accelerator Conference, 1996] accelerator are simulated in the absence of space charge fields. In the second example, the SCL emission and electron trajectories in an electron gun are simulated.

Dynamic response analysis of an aircraft structure under thermal-acoustic loads

International Nuclear Information System (INIS)

Cheng, H; Li, H B; Zhang, W; Wu, Z Q; Liu, B R

2016-01-01

Future hypersonic aircraft will be exposed to extreme combined environments includes large magnitude thermal and acoustic loads. It presents a significant challenge for the integrity of these vehicles. Thermal-acoustic test is used to test structures for dynamic response and sonic fatigue due to combined loads. In this research, the numerical simulation process for the thermal acoustic test is presented, and the effects of thermal loads on vibro-acoustic response are investigated. To simulate the radiation heating system, Monte Carlo theory and thermal network theory was used to calculate the temperature distribution. Considering the thermal stress, the high temperature modal parameters are obtained with structural finite element methods. Based on acoustic finite element, modal-based vibro-acoustic analysis is carried out to compute structural responses. These researches are very vital to optimum thermal-acoustic test and structure designs for future hypersonic vehicles structure (paper)

Strength of tensed and compressed concrete segments in crack spacing under short-term dynamic load

Directory of Open Access Journals (Sweden)

Galyautdinov Zaur

2018-01-01

Full Text Available Formation of model describing dynamic straining of reinforced concrete requires taking into account the basic aspects influencing the stress-strain state of structures. Strength of concrete segments in crack spacing is one of the crucial aspects that affect general strain behavior of reinforced concrete. Experimental results demonstrate significant change in strength of tensed and compressed concrete segments in crack spacing both under static and under dynamic loading. In this case, strength depends on tensile strain level and the slope angle of rebars towards the cracks direction. Existing theoretical and experimental studies estimate strength of concrete segments in crack spacing under static loading. The present work presents results of experimental and theoretical studies of dynamic strength of plates between cracks subjected to compression-tension. Experimental data was analyzed statistically; the dependences were suggested to describe dynamic strength of concrete segments depending on tensile strain level and slope angle of rebars to cracks direction.

Dynamic tensile loading improves the functional properties of mesenchymal stem cell-laden nanofiber-based fibrocartilage.

Science.gov (United States)

Baker, Brendon M; Shah, Roshan P; Huang, Alice H; Mauck, Robert L

2011-05-01

Fibrocartilaginous tissues such as the meniscus serve critical load-bearing roles, relying on arrays of collagen fibers to resist tensile loads experienced with normal activity. As these structures are frequently injured and possess limited healing capacity, there exists great demand for tissue-engineered replacements. Toward recreating the structural features of these anisotropic tissues in vitro, we employ scaffolds composed of co-aligned nanofibers that direct mesenchymal stem cell (MSC) orientation and the formation of organized extracellular matrix (ECM). Concomitant with ECM synthesis, the mechanical properties of constructs increase with free-swelling culture, but ultimately failed to achieve equivalence with meniscal fibrocartilage. As mechanical forces are essential to the development and maintenance of musculoskeletal tissues, this work examined the effect of cyclic tensile loading on MSC-laden nanofibrous constructs. We hypothesized that loading would modulate the transcriptional behavior of MSCs, spur the deposition of ECM, and lead to enhancements in construct mechanical properties compared to free-swelling controls. Fiber-aligned scaffolds were seeded with MSCs and dynamically loaded daily in tension or maintained as nonloaded controls for 4 weeks. With mechanical stimulation, fibrous gene expression increased, collagen deposition increased, and the tensile modulus increased by 16% relative to controls. These results show that dynamic tensile loading enhances the maturation of MSC-laden aligned nanofibrous constructs, suggesting that recapitulation of the structural and mechanical environment of load-bearing tissues results in increases in functional properties that can be exploited for tissue engineering applications.

A novel reformulation of the Theory of Critical Distances to design notched metals against dynamic loading

International Nuclear Information System (INIS)

Yin, T.; Tyas, A.; Plekhov, O.; Terekhina, A.; Susmel, L.

2015-01-01

Highlights: • The proposed method is successful in estimating dynamic strength of metals. • The critical distance varies as the loading/strain/displacement rate increases. • The reference strength varies as the loading/strain/displacement rate increases. • This method is recommended to be used with safety factors larger than 1.25. - Abstract: In the present study the linear-elastic Theory of Critical Distances (TCD) is reformulated to make it suitable for predicting the strength of notched metallic materials subjected to dynamic loading. The accuracy and reliability of the proposed reformulation of the TCD was checked against a number of experimental results generated by testing, under different loading/strain rates, notched cylindrical samples of aluminium alloy 6063-T5, titanium alloy Ti–6Al–4V, aluminium alloy AlMg6, and an AlMn alloy. To further validate the proposed design method also different data sets taken from the literature were considered. Such an extensive validation exercise allowed us to prove that the proposed reformulation of the TCD is successful in predicting the dynamic strength of notched metallic materials, this approach proving to be capable of estimates falling within an error interval of ±20%. Such a high level of accuracy is certainly remarkable, especially in light of the fact that it was reached without the need for explicitly modelling the stress vs. strain dynamic behaviour of the investigated ductile metals

Evaluation of Induced Settlements of Piled Rafts in the Coupled Static-Dynamic Loads Using Neural Networks and Evolutionary Polynomial Regression

Directory of Open Access Journals (Sweden)

Ali Ghorbani

2017-01-01

Full Text Available Coupled Piled Raft Foundations (CPRFs are broadly applied to share heavy loads of superstructures between piles and rafts and reduce total and differential settlements. Settlements induced by static/coupled static-dynamic loads are one of the main concerns of engineers in designing CPRFs. Evaluation of induced settlements of CPRFs has been commonly carried out using three-dimensional finite element/finite difference modeling or through expensive real-scale/prototype model tests. Since the analyses, especially in the case of coupled static-dynamic loads, are not simply conducted, this paper presents two practical methods to gain the values of settlement. First, different nonlinear finite difference models under different static and coupled static-dynamic loads are developed to calculate exerted settlements. Analyses are performed with respect to different axial loads and pile’s configurations, numbers, lengths, diameters, and spacing for both loading cases. Based on the results of well-validated three-dimensional finite difference modeling, artificial neural networks and evolutionary polynomial regressions are then applied and introduced as capable methods to accurately present both static and coupled static-dynamic settlements. Also, using a sensitivity analysis based on Cosine Amplitude Method, axial load is introduced as the most influential parameter, while the ratio l/d is reported as the least effective parameter on the settlements of CPRFs.

On the application of the dynamic plasticity theory for the treatment of reinforced concrete structures under transient loading

International Nuclear Information System (INIS)

Ammann, W.

1983-01-01

After a short introduction of the theory of dynamic plasticity, the possible applications of this theory on reinforced concrete structures under transient loading are discussed. Estimates can be obtained by relations giving lower and upper limits for dynamically loaded supporting beams. A procedure similar for the mode approximation method is described for the calculation of beams after a sudden failure of a support. (orig.) [de

Study on the Vehicle Dynamic Load Considering the Vehicle-Pavement Coupled Effect

Science.gov (United States)

Xu, H. L.; He, L.; An, D.

2017-11-01

The vibration of vehicle-pavement interaction system is sophisticated random vibration process and the vehicle-pavement coupled effect was not considered in the previous study. A new linear elastic model of the vehicle-pavement coupled system was established in the paper. The new model was verified with field measurement which could reflect the real vibration between vehicle and pavement. Using the new model, the study on the vehicle dynamic load considering the vehicle-pavement coupled effect showed that random forces (centralization) between vehicle and pavement were influenced largely by vehicle-pavement coupled effect. Numerical calculation indicated that the maximum of random forces in coupled model was 2.4 times than that in uncoupled model. Inquiring the reason, it was found that the main vibration frequency of the vehicle non-suspension system was similar with that of the vehicle suspension system in the coupled model and the resonance vibration lead to vehicle dynamic load increase significantly.

Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading.

Science.gov (United States)

Ignasiak, Dominika; Dendorfer, Sebastian; Ferguson, Stephen J

2016-04-11

Musculoskeletal modeling offers an invaluable insight into the spine biomechanics. A better understanding of thoracic spine kinetics is essential for understanding disease processes and developing new prevention and treatment methods. Current models of the thoracic region are not designed for segmental load estimation, or do not include the complex construct of the ribcage, despite its potentially important role in load transmission. In this paper, we describe a numerical musculoskeletal model of the thoracolumbar spine with articulated ribcage, modeled as a system of individual vertebral segments, elastic elements and thoracic muscles, based on a previously established lumbar spine model and data from the literature. The inverse dynamics simulations of the model allow the prediction of spinal loading as well as costal joints kinetics and kinematics. The intradiscal pressure predicted by the model correlated well (R(2)=0.89) with reported intradiscal pressure measurements, providing a first validation of the model. The inclusion of the ribcage did not affect segmental force predictions when the thoracic spine did not perform motion. During thoracic motion tasks, the ribcage had an important influence on the predicted compressive forces and muscle activation patterns. The compressive forces were reduced by up to 32%, or distributed more evenly between thoracic vertebrae, when compared to the predictions of the model without ribcage, for mild thoracic flexion and hyperextension tasks, respectively. The presented musculoskeletal model provides a tool for investigating thoracic spine loading and load sharing between vertebral column and ribcage during dynamic activities. Further validation for specific applications is still necessary. Copyright © 2015 Elsevier Ltd. All rights reserved.

DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING

Data.gov (United States)

National Aeronautics and Space Administration — DYNAMIC STRAIN MAPPING AND REAL-TIME DAMAGE STATE ESTIMATION UNDER BIAXIAL RANDOM FATIGUE LOADING SUBHASISH MOHANTY*, ADITI CHATTOPADHYAY, JOHN N. RAJADAS, AND CLYDE...

Fluid-structure interaction dynamic simulation of spring-loaded pressure relief valves under seismic wave

Science.gov (United States)

Lv, Dongwei; Zhang, Jian; Yu, Xinhai

2018-05-01

In this paper, a fluid-structure interaction dynamic simulation method of spring-loaded pressure relief valve was established. The dynamic performances of the fluid regions and the stress and strain of the structure regions were calculated at the same time by accurately setting up the contact pairs between the solid parts and the coupling surfaces between the fluid regions and the structure regions. A two way fluid-structure interaction dynamic simulation of a simplified pressure relief valve model was carried out. The influence of vertical sinusoidal seismic waves on the performance of the pressure relief valve was preliminarily investigated by loading sine waves. Under vertical seismic waves, the pressure relief valve will flutter, and the reseating pressure was affected by the amplitude and frequency of the seismic waves. This simulation method of the pressure relief valve under vertical seismic waves can provide effective means for investigating the seismic performances of the valves, and make up for the shortcomings of the experiment.

Experimental investigation of dynamic performance and transient responses of a kW-class PEM fuel cell stack under various load changes

International Nuclear Information System (INIS)

Tang Yong; Yuan Wei; Pan Minqiang; Li Zongtao; Chen Guoqing; Li Yong

2010-01-01

The dynamic performance is a very important evaluation index of proton exchange membrane (PEM) fuel cells used for real application, which is mostly related with water, heat and gas management. A commercial PEM fuel cell system of Nexa module is employed to experimentally investigate the dynamic behavior and transient response of a PEM fuel cell stack and reveal involved influential factors. Five groups of dynamic tests are conducted and divided into different stage such as start-up, shut-down, step-up load, regular load variation and irregular load variation. It is observed that the external load changes the current output proportionally and reverses stack voltage accordingly. The purge operation benefits performance recovery and enhancement during a constant load and its time strongly depends on the operational current level. Overshoot and undershoot behaviors are observed during transience. But the current undershoot does not appear due to charge double-layer effect. Additionally, magnitudes of the peaks of the voltage overshoot and undershoot vary at different current levels. The operating temperature responds fast to current load but changes slowly showing an arc-like profile without any overshoot and undershoot events. The air flow rate changes directly following the dynamic load demand. But the increased amount of air flow rate during different step-change is not identical, which depends on the requirement of internal reaction and flooding intensity. The results can be utilized for validation of dynamic fuel cell models, and regarded as reference for effective control and management strategies.

Dynamic load balancing in a concurrent plasma PIC code on the JPL/Caltech Mark III hypercube

International Nuclear Information System (INIS)

Liewer, P.C.; Leaver, E.W.; Decyk, V.K.; Dawson, J.M.

1990-01-01

Dynamic load balancing has been implemented in a concurrent one-dimensional electromagnetic plasma particle-in-cell (PIC) simulation code using a method which adds very little overhead to the parallel code. In PIC codes, the orbits of many interacting plasma electrons and ions are followed as an initial value problem as the particles move in electromagnetic fields calculated self-consistently from the particle motions. The code was implemented using the GCPIC algorithm in which the particles are divided among processors by partitioning the spatial domain of the simulation. The problem is load-balanced by partitioning the spatial domain so that each partition has approximately the same number of particles. During the simulation, the partitions are dynamically recreated as the spatial distribution of the particles changes in order to maintain processor load balance

The effect of loading time on flexible pavement dynamic response: a finite element analysis

Science.gov (United States)

Yin, Hao; Solaimanian, Mansour; Kumar, Tanmay; Stoffels, Shelley

2007-12-01

Dynamic response of asphalt concrete (AC) pavements under moving load is a key component for accurate prediction of flexible pavement performance. The time and temperature dependency of AC materials calls for utilizing advanced material characterization and mechanistic theories, such as viscoelasticity and stress/strain analysis. In layered elastic analysis, as implemented in the new Mechanistic-Empirical Pavement Design Guide (MEPDG), the time dependency is accounted for by calculating the loading times at different AC layer depths. In this study, the time effect on pavement response was evaluated by means of the concept of “pseudo temperature.” With the pavement temperature measured from instrumented thermocouples, the time and temperature dependency of AC materials was integrated into one single factor, termed “effective temperature.” Via this effective temperature, pavement responses under a transient load were predicted through finite element analysis. In the finite element model, viscoelastic behavior of AC materials was characterized through relaxation moduli, while the layers with unbound granular material were assumed to be in an elastic mode. The analysis was conducted for two different AC mixtures in a simplified flexible pavement structure at two different seasons. Finite element analysis results reveal that the loading time has a more pronounced impact on pavement response in the summer for both asphalt types. The results indicate that for reasonable prediction of dynamic response in flexible pavements, the effect of the depth-dependent loading time on pavement temperature should be considered.

Analyses of the dynamic behaviour of nuclear installation under external loads

International Nuclear Information System (INIS)

Alex, H.; Kaestle, H.J.; Kuntze, W.M.

1976-04-01

This paper demonstrates the dynamic analysis of a reactor building which is subject to earthquake loading. The purpose of this investigation is to calculate characteristic dynamical parameters at certain positions of the structure, such as floor time histories. Following the selection of a typical earthquake time history the reactor building is modelled with Finite Elements. The calculations are performed with the program system ASKA using Time History Modal Analysis. Prior to the response calculation the eigenvalue problem is solved. The results of the analysis, such as displacements, stresses and floor time histories will be discussed in view of the chosen earthquake excitation. (orig.) [de

Research on dynamic creep strain and settlement prediction under the subway vibration loading.

Science.gov (United States)

Luo, Junhui; Miao, Linchang

2016-01-01

This research aims to explore the dynamic characteristics and settlement prediction of soft soil. Accordingly, the dynamic shear modulus formula considering the vibration frequency was utilized and the dynamic triaxial test conducted to verify the validity of the formula. Subsequently, the formula was applied to the dynamic creep strain function, with the factors influencing the improved dynamic creep strain curve of soft soil being analyzed. Meanwhile, the variation law of dynamic stress with sampling depth was obtained through the finite element simulation of subway foundation. Furthermore, the improved dynamic creep strain curve of soil layer was determined based on the dynamic stress. Thereafter, it could to estimate the long-term settlement under subway vibration loading by norms. The results revealed that the dynamic shear modulus formula is straightforward and practical in terms of its application to the vibration frequency. The values predicted using the improved dynamic creep strain formula closed to the experimental values, whilst the estimating settlement closed to the measured values obtained in the field test.

A fast and optimized dynamic economic load dispatch for large scale power systems

International Nuclear Information System (INIS)

Musse Mohamud Ahmed; Mohd Ruddin Ab Ghani; Ismail Hassan

2000-01-01

This paper presents Lagrangian Multipliers (LM) and Linear Programming (LP) based dynamic economic load dispatch (DELD) solution for large-scale power system operations. It is to minimize the operation cost of power generation. units subject to the considered constraints. After individual generator units are economically loaded and periodically dispatched, fast and optimized DELD has been achieved. DELD with period intervals has been taken into consideration The results found from the algorithm based on LM and LP techniques appear to be modest in both optimizing the operation cost and achieving fast computation. (author)

Damage of plates due to impact, dynamic pressure and explosive loads

Directory of Open Access Journals (Sweden)

Norman Jones

Full Text Available It is the purpose of this article to present design equations which can be used to predict the damage of ductile plating when subjected to mass impact, dynamic pressure or impulsive loadings. The external loadings are sufficiently severe to produce inelastic material behaviour and produce finite transverse displacement, or geometry change, effects. The damage is characterised as the final or permanent transverse displacement of a plate. The theoretical method predicts values for the maximum permanent transverse displacements which agree reasonably well with the corresponding experimental results generated on aluminium alloy circular, square and rectangular plates. Thus, the equations presented in this article are valuable for preliminary design purposes and for forensic studies, while the experimental data can be used for validating numerical schemes.

The effects of combining dynamic pricing, AC load control, and real-time energy feedback. SMUD'S 2011 Residential Summer Solutions Study

Energy Technology Data Exchange (ETDEWEB)

Herter, K. [Herter Energy Research Solutions, El Dorado Hills, CA (United States); Wood, V. [Sacramento Municipal Utility District, Sacramento, CA (United States); Blozis, S. [University of California, Davis, CA (United States)

2013-11-15

The 2011 Residential Summer Solutions Study compared the hourly load effects of three different real-time information treatments and two program options. The information treatments included: Baseline information (no real-time data), real-time Home information (whole-house data), and real-time Appliance information (data for the whole house plus three individual appliances). Compared to the Baseline group, real-time Home information lowered overall energy use by about 4 %. Real-time information at both the Home and Appliance levels had a significant effect on non-event peak loads: compared to the Baseline group, real-time Home data lowered peak load by 5 %, while Appliance data lowered peak load by 7 %. All three information treatments averaged a 1-kW (40 %) load shed during events. The customer-chosen program options included a dynamic time-of-use rate and a load control incentive program. Customers were more likely to sign up for the dynamic rate, and those who did saved significantly more peak load on both event days (>50 % savings) and non-event days (>20 % savings) than did those on the load control program alone. In addition, those on the dynamic rate saved twice as much on their summer bills as did those who chose to remain on the standard tiered rate. At the end of the summer, more than 90 % of participants signed up to participate again the following year.

Minimization of Impact from Electric Vehicle Supply Equipment to the Electric Grid Using a Dynamically Controlled Battery Bank for Peak Load Shaving

Energy Technology Data Exchange (ETDEWEB)

Castello, Charles C [ORNL

2013-01-01

This research presents a comparison of two control systems for peak load shaving using local solar power generation (i.e., photovoltaic array) and local energy storage (i.e., battery bank). The purpose is to minimize load demand of electric vehicle supply equipment (EVSE) on the electric grid. A static and dynamic control system is compared to decrease demand from EVSE. Static control of the battery bank is based on charging and discharging to the electric grid at fixed times. Dynamic control, with 15-minute resolution, forecasts EVSE load based on data analysis of collected data. In the proposed dynamic control system, the sigmoid function is used to shave peak loads while limiting scenarios that can quickly drain the battery bank. These control systems are applied to Oak Ridge National Laboratory s (ORNL) solar-assisted electric vehicle (EV) charging stations. This installation is composed of three independently grid-tied sub-systems: (1) 25 EVSE; (2) 47 kW photovoltaic (PV) array; and (3) 60 kWh battery bank. The dynamic control system achieved the greatest peak load shaving, up to 34% on a cloudy day and 38% on a sunny day. The static control system was not ideal; peak load shaving was 14.6% on a cloudy day and 12.7% on a sunny day. Simulations based on ORNL data shows solar-assisted EV charging stations combined with the proposed dynamic battery control system can negate up to 89% of EVSE load demand on sunny days.

Dynamic analysis of crack growth and arrest in a pressure vessel subjected to thermal and pressure loading

International Nuclear Information System (INIS)

Brickstad, B.

1984-01-01

Predictions of crack arrest behaviour are performed for a cracked reactor pressure vessel under both thermal and pressure loading. The object is to compare static and dynamic calculations. The dynamic calculations are made using an explicit finite element technique where crack growth is simulated by gradual nodal release. Three different load cases and the effect of different velocity dependence on the crack propagation toughness are studied. It is found that for the analysed cases the static analysis is slightly conservative, thus justifying its use for these problems. (orig.)

Dynamic Responses of Continuous Girder Bridges with Uniform Cross-Section under Moving Vehicular Loads

OpenAIRE

Gao, Qingfei; Wang, Zonglin; Jia, Hongyu; Liu, Chenguang; Li, Jun; Guo, Binqiang; Zhong, Junfei

2015-01-01

To address the drawback of traditional method of investigating dynamic responses of the continuous girder bridge with uniform cross-section under moving vehicular loads, the orthogonal experimental design method is proposed in this paper. Firstly, some empirical formulas of natural frequencies are obtained by theoretical derivation and numerical simulation. The effects of different parameters on dynamic responses of the vehicle-bridge coupled vibration system are discussed using our own progr...

The effects of individual differences, prior experience and cognitive load on the transfer of dynamic decision-making performance.

Science.gov (United States)

Nicholson, Brad; O'Hare, David

2014-01-01

Situational awareness is recognised as an important factor in the performance of individuals and teams in dynamic decision-making (DDM) environments (Salmon et al. 2014 ). The present study was designed to investigate whether the scores on the WOMBAT™ Situational Awareness and Stress Tolerance Test (Roscoe and North 1980 ) would predict the transfer of DDM performance from training under different levels of cognitive load to a novel situation. Participants practised a simulated firefighting task under either low or high conditions of cognitive load and then performed a (transfer) test in an alternative firefighting environment under an intermediate level of cognitive load. WOMBAT™ test scores were a better predictor of DDM performance than scores on the Raven Matrices. Participants with high WOMBAT™ scores performed better regardless of their training condition. Participants with recent gaming experience who practised under low cognitive load showed better practice phase performance but worse transfer performance than those who practised under high cognitive load. The relationship between task experience, situational awareness ability, cognitive load and the transfer of dynamic decision-making (DDM) performance was investigated. Results showed that the WOMBAT™ test predicted transfer of DDM performance regardless of task cognitive load. The effects of cognitive load on performance varied according to previous task-relevant experience.

Thermal and dynamic loads on the EPR containment due to hydrogen combustion

International Nuclear Information System (INIS)

Eyink, J.; Movahed, M.; Petzold, K.G.; Kotchourko, A.; Royl, P.; Travis, J.R.

2001-01-01

A major aspect of the EPR safety concept is to cope with severe accidents including core melt and to maintain the integrity of the containment even for those hypothetical events. One potential threat for the containment is related to the combustion of hydrogen, which may be produced in a large amount during core degradation. The European Pressurized Water Reactor (EPR) hydrogen mitigation concept consists of about 44 recombiners, located mainly in the equipment rooms (only 4 recombiners are located in the dome area). This paper is devoted to two important potential threats on the containment related to hydrogen removal: - Thermal loads resulting from recombiner action and/or combustion are of importance also with respect to the integrity of the local composite liner foreseen at some crucial locations of the containment; - Dynamic loads resulting from fast deflagration may impair containment wall or internal walls even if the AICC (adiabatic isochoric complete combustion) pressure is below the design pressure. Two types of combustion calculations have been performed: a) In cases, where fast deflagration cannot be excluded, combustion has been calculated with COM3D, a special CFD code developed to calculate dynamic pressure loads on walls, and b) 'Standing flame' combustion as well as recombination processes have been calculated with GASFLOW for bounding scenarios in order to evaluate maximum containment wall surface temperatures for cases of long-lasting combustion, mainly with emphasis on the application of a partial liner. Because of the depressurization of the reactor coolant system directly into the containment atmosphere via a relief tank and rupture discs a high concentration of steam is available for nearly all scenarios. For these scenarios no threat to internal walls is expected based on the combustion loads identified by the analyses presented here. In case of fast secondary cool-down a large amount of energy is removed to the secondary side of the SG and

Relation between coordinate systems describing the dynamics of a loaded Stewart platform

Science.gov (United States)

Petrova, V. I.

2018-05-01

The paper puts forward formulae for transformation of coordinates in three coordinate frames used for the study of motion of a loaded Stewart platform, which is the central mechanism of the dynamic bench. A new method for finding the law of variation of coordinates is proposed. This method depends on solving the problem-specific system of differential equations.

Large Variations in HIV-1 Viral Load Explained by Shifting-Mosaic Metapopulation Dynamics

Science.gov (United States)

Lythgoe, Katrina A.; Blanquart, François

2016-01-01

The viral population of HIV-1, like many pathogens that cause systemic infection, is structured and differentiated within the body. The dynamics of cellular immune trafficking through the blood and within compartments of the body has also received wide attention. Despite these advances, mathematical models, which are widely used to interpret and predict viral and immune dynamics in infection, typically treat the infected host as a well-mixed homogeneous environment. Here, we present mathematical, analytical, and computational results that demonstrate that consideration of the spatial structure of the viral population within the host radically alters predictions of previous models. We study the dynamics of virus replication and cytotoxic T lymphocytes (CTLs) within a metapopulation of spatially segregated patches, representing T cell areas connected by circulating blood and lymph. The dynamics of the system depend critically on the interaction between CTLs and infected cells at the within-patch level. We show that for a wide range of parameters, the system admits an unexpected outcome called the shifting-mosaic steady state. In this state, the whole body’s viral population is stable over time, but the equilibrium results from an underlying, highly dynamic process of local infection and clearance within T-cell centers. Notably, and in contrast to previous models, this new model can explain the large differences in set-point viral load (SPVL) observed between patients and their distribution, as well as the relatively low proportion of cells infected at any one time, and alters the predicted determinants of viral load variation. PMID:27706164

Portable Parallel Programming for the Dynamic Load Balancing of Unstructured Grid Applications

Science.gov (United States)

Biswas, Rupak; Das, Sajal K.; Harvey, Daniel; Oliker, Leonid

1999-01-01

The ability to dynamically adapt an unstructured -rid (or mesh) is a powerful tool for solving computational problems with evolving physical features; however, an efficient parallel implementation is rather difficult, particularly from the view point of portability on various multiprocessor platforms We address this problem by developing PLUM, tin automatic anti architecture-independent framework for adaptive numerical computations in a message-passing environment. Portability is demonstrated by comparing performance on an SP2, an Origin2000, and a T3E, without any code modifications. We also present a general-purpose load balancer that utilizes symmetric broadcast networks (SBN) as the underlying communication pattern, with a goal to providing a global view of system loads across processors. Experiments on, an SP2 and an Origin2000 demonstrate the portability of our approach which achieves superb load balance at the cost of minimal extra overhead.

LDRD final report : mesoscale modeling of dynamic loading of heterogeneous materials

Energy Technology Data Exchange (ETDEWEB)

Robbins, Joshua [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Dingreville, Remi Philippe Michel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Voth, Thomas Eugene [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Furnish, Michael David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2013-12-01

Material response to dynamic loading is often dominated by microstructure (grain structure, porosity, inclusions, defects). An example critically important to Sandia's mission is dynamic strength of polycrystalline metals where heterogeneities lead to localization of deformation and loss of shear strength. Microstructural effects are of broad importance to the scientific community and several institutions within DoD and DOE; however, current models rely on inaccurate assumptions about mechanisms at the sub-continuum or mesoscale. Consequently, there is a critical need for accurate and robust methods for modeling heterogeneous material response at this lower length scale. This report summarizes work performed as part of an LDRD effort (FY11 to FY13; project number 151364) to meet these needs.

Computational fluid dynamics modeling of bun baking process under different oven load conditions.

Science.gov (United States)

Tank, A; Chhanwal, N; Indrani, D; Anandharamakrishnan, C

2014-09-01

A computational fluid dynamics (CFD) model was developed to study the temperature profile of the bun during baking process. Evaporation-condensation mechanism and effect of the latent heat during phase change of water was incorporated in this model to represent actual bun baking process. Simulation results were validated with experimental measurements of bun temperature at two different positions. Baking process is completed within 20 min, after the temperature of crumb become stable at 98 °C. Further, this study was extended to investigate the effect of partially (two baking trays) loaded and fully loaded (eight baking trays) oven on temperature profile of bun. Velocity and temperature profile differs in partially loaded and fully loaded oven. Bun placed in top rack showed rapid baking while bun placed in bottom rack showed slower baking due to uneven temperature distribution in the oven. Hence, placement of bun inside the oven affects temperature of bun and consequently, the quality of the product.

Dynamic Reliability Analysis of Gear Transmission System of Wind Turbine in Consideration of Randomness of Loadings and Parameters

Directory of Open Access Journals (Sweden)

Lei Wang

2014-01-01

Full Text Available A dynamic model of gear transmission system of wind turbine is built with consideration of randomness of loads and parameters. The dynamic response of the system is obtained using the theory of random sampling and the Runge-Kutta method. According to rain flow counting principle, the dynamic meshing forces are converted into a series of luffing fatigue load spectra. The amplitude and frequency of the equivalent stress are obtained using equivalent method of Geber quadratic curve. Moreover, the dynamic reliability model of components and system is built according to the theory of probability of cumulative fatigue damage. The system reliability with the random variation of parameters is calculated and the influence of random parameters on dynamic reliability of components is analyzed. In the end, the results of the proposed method are compared with that of Monte Carlo method. This paper can be instrumental in the design of wind turbine gear transmission system with more advantageous dynamic reliability.

Comparative study of two materials for dynamic hip screw during fall and gait loading: titanium alloy and stainless steel.

Science.gov (United States)

Taheri, Nooshin S; Blicblau, Aaron S; Singh, Manmohan

2011-11-01

Internal fixation with dynamic hip screw is a choice of treatment for hip fractures to stabilize a femoral fracture. Choosing the proper implant and its material has a great effect on the healing process and failure prevention. The purpose of this analysis was to assess biomechanical behavior of dynamic hip screw with two different materials implanted in the femur during fall and gait. A 3D finite element model of an intact femur and a 3D implant within the same femur were developed. A finite element analysis was carried out to establish the effect of load conditions and implant material properties on biomechanical behavior of the dynamic hip screw after internal fixation. Two load configurations are chosen: one simulating the stance phase of the normal gait cycle, and the other replicating a low-energy fall. The implanted femur was investigated with two different materials for the dynamic hip screw: stainless steel and titanium alloy. During stance, more stress is placed on the implanted femur compared with the intact femur. During a fall, the implanted femur is in a greater state of stress, which mostly occurs inside the dynamic hip screw. Titanium alloy decreases stress levels by an average of 40% compared with stainless steel. However, deformation is slightly reduced with a stainless steel dynamic hip screw during both load cases. After internal fixation, dynamic hip screw generates greater stresses within the implanted femur compared with the intact femur under the same loading conditions. A titanium alloy implant appears to undergo less stress from a low-energy fall compared with stainless steel and can be considered the preferred implant material. The critical parts of the dynamic hip screw are the forth distal screw and the plate.

Low-back electromyography (EMG data-driven load classification for dynamic lifting tasks.

Directory of Open Access Journals (Sweden)

Deema Totah

Full Text Available Numerous devices have been designed to support the back during lifting tasks. To improve the utility of such devices, this research explores the use of preparatory muscle activity to classify muscle loading and initiate appropriate device activation. The goal of this study was to determine the earliest time window that enabled accurate load classification during a dynamic lifting task.Nine subjects performed thirty symmetrical lifts, split evenly across three weight conditions (no-weight, 10-lbs and 24-lbs, while low-back muscle activity data was collected. Seven descriptive statistics features were extracted from 100 ms windows of data. A multinomial logistic regression (MLR classifier was trained and tested, employing leave-one subject out cross-validation, to classify lifted load values. Dimensionality reduction was achieved through feature cross-correlation analysis and greedy feedforward selection. The time of full load support by the subject was defined as load-onset.Regions of highest average classification accuracy started at 200 ms before until 200 ms after load-onset with average accuracies ranging from 80% (±10% to 81% (±7%. The average recall for each class ranged from 69-92%.These inter-subject classification results indicate that preparatory muscle activity can be leveraged to identify the intent to lift a weight up to 100 ms prior to load-onset. The high accuracies shown indicate the potential to utilize intent classification for assistive device applications.Active assistive devices, e.g. exoskeletons, could prevent back injury by off-loading low-back muscles. Early intent classification allows more time for actuators to respond and integrate seamlessly with the user.

Dynamics and mechanics of bed-load tracer particles

Directory of Open Access Journals (Sweden)

C. B. Phillips

2014-12-01

Full Text Available Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool bedrock tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement distances scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modeling framework based on momentum conservation at the grain scale. Tracer displacement is weakly negatively correlated with particle size at the individual flood scale; however cumulative travel distance begins to show a stronger inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the bedrock and alluvial channels collapse onto a single curve – despite more than an order of magnitude difference in channel slope – when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.

Dynamic simulation of knee-joint loading during gait using force-feedback control and surrogate contact modelling.

Science.gov (United States)

Walter, Jonathan P; Pandy, Marcus G

2017-10-01

The aim of this study was to perform multi-body, muscle-driven, forward-dynamics simulations of human gait using a 6-degree-of-freedom (6-DOF) model of the knee in tandem with a surrogate model of articular contact and force control. A forward-dynamics simulation incorporating position, velocity and contact force-feedback control (FFC) was used to track full-body motion capture data recorded for multiple trials of level walking and stair descent performed by two individuals with instrumented knee implants. Tibiofemoral contact force errors for FFC were compared against those obtained from a standard computed muscle control algorithm (CMC) with a 6-DOF knee contact model (CMC6); CMC with a 1-DOF translating hinge-knee model (CMC1); and static optimization with a 1-DOF translating hinge-knee model (SO). Tibiofemoral joint loads predicted by FFC and CMC6 were comparable for level walking, however FFC produced more accurate results for stair descent. SO yielded reasonable predictions of joint contact loading for level walking but significant differences between model and experiment were observed for stair descent. CMC1 produced the least accurate predictions of tibiofemoral contact loads for both tasks. Our findings suggest that reliable estimates of knee-joint loading may be obtained by incorporating position, velocity and force-feedback control with a multi-DOF model of joint contact in a forward-dynamics simulation of gait. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Aerodynamic loads calculation and analysis for large scale wind turbine based on combining BEM modified theory with dynamic stall model

Energy Technology Data Exchange (ETDEWEB)

Dai, J.C. [College of Mechanical and Electrical Engineering, Central South University, Changsha (China); School of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan (China); Hu, Y.P.; Liu, D.S. [School of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan (China); Long, X. [Hara XEMC Windpower Co., Ltd., Xiangtan (China)

2011-03-15

The aerodynamic loads for MW scale horizontal-axis wind turbines are calculated and analyzed in the established coordinate systems which are used to describe the wind turbine. In this paper, the blade element momentum (BEM) theory is employed and some corrections, such as Prandtl and Buhl models, are carried out. Based on the B-L semi-empirical dynamic stall (DS) model, a new modified DS model for NACA63-4xx airfoil is adopted. Then, by combing BEM modified theory with DS model, a set of calculation method of aerodynamic loads for large scale wind turbines is proposed, in which some influence factors such as wind shear, tower, tower and blade vibration are considered. The research results show that the presented dynamic stall model is good enough for engineering purpose; the aerodynamic loads are influenced by many factors such as tower shadow, wind shear, dynamic stall, tower and blade vibration, etc, with different degree; the single blade endures periodical changing loads but the variations of the rotor shaft power caused by the total aerodynamic torque in edgewise direction are very small. The presented study approach of aerodynamic loads calculation and analysis is of the university, and helpful for thorough research of loads reduction on large scale wind turbines. (author)

Predicting Dynamic Response of Structures under Earthquake Loads Using Logical Analysis of Data

Directory of Open Access Journals (Sweden)

Ayman Abd-Elhamed

2018-04-01

Full Text Available In this paper, logical analysis of data (LAD is used to predict the seismic response of building structures employing the captured dynamic responses. In order to prepare the data, computational simulations using a single degree of freedom (SDOF building model under different ground motion records are carried out. The selected excitation records are real and of different peak ground accelerations (PGA. The sensitivity of the seismic response in terms of displacements of floors to the variation in earthquake characteristics, such as soil class, characteristic period, and time step of records, peak ground displacement, and peak ground velocity, have also been considered. The dynamic equation of motion describing the building model and the applied earthquake load are presented and solved incrementally using the Runge-Kutta method. LAD then finds the characteristic patterns which lead to forecast the seismic response of building structures. The accuracy of LAD is compared to that of an artificial neural network (ANN, since the latter is the most known machine learning technique. Based on the conducted study, the proposed LAD model has been proven to be an efficient technique to learn, simulate, and blindly predict the dynamic response behaviour of building structures subjected to earthquake loads.

Stress Analysis and Fatigue Behaviour of PTFE-Bronze Layered Journal Bearing under Real-Time Dynamic Loading

Science.gov (United States)

Duman, M. S.; Kaplan, E.; Cuvalcı, O.

2018-01-01

The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. ‘Permaglide Plain Bearings P10’ type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.

EURDYN, Nonlinear Transient Analysis of Structure with Dynamic Loads

International Nuclear Information System (INIS)

Donea, J.; Giuliani, S.; Halleux, J.P.

1987-01-01

1 - Description of program or function: The EURDYN computer codes are under development at JRC-Ispra since 1973 for the simulation of non- linear dynamic response of fast-reactor components submitted to impulsive loading due to abnormal working conditions. They are thus mainly used in reactor safety analysis but can apply to other fields. Indeed the codes compute the elasto-plastic transient response of 2-D and thin 3-D structures submitted to fast dynamic loading generated by explosions, impacts... and represented by time dependent pressures, concentrated loads and prescribed displacements, or by initial speeds. Two releases of the structural computer codes EURDYN 01 (2-D beams and triangles and axisymmetric conical shells and triangular tori), 02 (axisymmetric and 2-D quadratic iso-parametric elements) and 03 (triangular plate elements) have already been produced in 1976(1) and 1980(2). They include material (elasto-plasticity using the classical flow theory approach) and geometrical (large displacements and rotations treated by a co-rotational technique) nonlinearities. The present version (Release 3) has been completed mid-1982 and is documented in EUR 8357 EN. The new features of Release 3, as compared to the former ones, roughly consist in: - full large strain capability for 9-node iso-parametric elements (EURDYN 02), - generalized array dimensions, - introduction of the radial return algorithm for elasto-plastic material modelling, - extension of the energy check facility to the case of prescribed displacements, - possible interface to a post-processing package including time plot facilities (TPLOT). The theoretical aspects can be found in refs. 2,4,5,6,7,8. 2 - Method of solution: - Finite element space discretization. - Explicit time integration. - Lumped masses. - EURDYN 01: 2-D co-rotational formulation including constant strain triangles (plane or axisymmetric), beams and conical shells, this last element being particularly useful for the study of thin

An improved model for considering strain rate effects on reinforced concrete elements behavior under dynamic loads

International Nuclear Information System (INIS)

Sim, J.; Soroushian, P.

1989-01-01

An improved model for predicting the reinforced concrete element behavior under dynamic strain rates was developed using the layer modeling technique. The developed strain rate sensitive model for axial/flexural analysis of reinforced concrete elements was used to predict the test results, performed at different loading rates, and the predictions were reasonable. The developed analysis technique was used to study the loading rate sensitivity of reinforced concrete beams and columns with different geometry and material properties. Two design formulas for computing the loading rate dependent axial and flexural strengths of reinforced concrete sections are suggested

An experimental study of the dynamic behavior of a 2 kW proton exchange membrane fuel cell stack under various loading conditions

International Nuclear Information System (INIS)

Jian, Qifei; Zhao, Yang; Wang, Haoting

2015-01-01

The dynamic behavior of the PEM (proton exchange membrane) fuel cell stack has great effect on the safety and effective operation of its applications. In this paper, a self-designed bulb-array is used to simulate the various loading conditions and study the dynamic behavior of a 2 kW PEM fuel cell stack. An evaluation index, including oscillation rate, pressure variation and dynamic resistance factor, is used to analyze the transient response of the PEM fuel cell stack. It is observed that the stack current increases about 8.6%, and the Oscillation rate decreases more rapidly after activation. In the step-up load stage, the oscillation rate and the dynamic resistance decrease more rapidly as the external load increases. Due to the periodic anodic purge process, a periodic voltage fluctuation can be seen. In addition, when the stack works in the open-loop state (working without the external load), the transient response of the stack current is significantly affected by the hydrogen humidity and the charge double-layer. - Highlights: • The working time of open-loop state significantly affects the transient response. • Oscillation rate decreases faster as the external load increases. • Dynamic resistance factor decreases as the external load increases. • The periodic anodic purge process leads to a slight periodic oscillation of voltage

The dependence of the Taylor-Quinney coefficient on the dynamic loading mode

Science.gov (United States)

Rittel, D.; Zhang, L. H.; Osovski, S.

2017-10-01

The efficiency of the thermomechanical conversion, expressed as the Taylor-Quinney coefficient (TQC) is seldom reported in the literature and generally assumed to be equal to 0.9. Moreover, an eventual dependence of this coefficient on the dynamic loading mode has not been investigated so far. This work presents a systematic characterization of the TQC for seven different metals and alloys loaded in dynamic tension, compression and dominant shear. The results show that the TQC varies greatly with the investigated material, instead of its assumed constant value of 0.9. Likewise, until final collapse of the specimen, the overall temperature rise remains quite modest. Moreover, we clearly observe that for commercially pure Titanium, which exhibits an asymmetric mechanical response in tension and compression, the measured TQC values are mode dependent too. Microstructural characterization reveals profuse twinning in compression and shear, as opposed to tension. Twinning is related to heat generation in accord with previous studies. In addition to reporting a wide database of TQC values, this study reveals a new correlation between the thermomechanical characteristics of a material and its deformation micromechanisms, that should find its way into constitutive models.

Estimation of dynamic load of mercury in a river with BASINS-HSPF model

Science.gov (United States)

Ying Ouyang; John Higman; Jeff Hatten

2012-01-01

Purpose Mercury (Hg) is a naturally occurring element and a pervasive toxic pollutant. This study investigated the dynamic loads of Hg from the Cedar-Ortega Rivers watershed into the Lower St. Johns River (LSJR), Florida, USA, using the better assessment science integrating point and nonpoint sources (BASINS)-hydrologic simulation program - FORTRAN (HSPF) model....

Dynamic load synthesis for shock numerical simulation in space structure design

Science.gov (United States)

Monti, Riccardo; Gasbarri, Paolo

2017-08-01

Pyroshock loads are the most stressing environments that a space equipment experiences during its operating life from a mechanical point of view. In general, the mechanical designer considers the pyroshock analysis as a very demanding constraint. Unfortunately, due to the non-linear behaviour of the structure under such loads, only the experimental tests can demonstrate if it is able to withstand these dynamic loads. By taking all the previous considerations into account, some preliminary information about the design correctness could be done by performing ;ad-hoc; numerical simulations, for example via commercial finite element software (i.e. MSC Nastran). Usually these numerical tools face the shock solution in two ways: 1) a direct mode, by using a time dependent enforcement and by evaluating the time-response and space-response as well as the internal forces; 2) a modal basis approach, by considering a frequency dependent load and of course by evaluating internal forces in the frequency domain. This paper has the main aim to develop a numerical tool to synthetize the time dependent enforcement based on deterministic and/or genetic algorithm optimisers. In particular starting from a specified spectrum in terms of SRS (Shock Response Spectrum) a time dependent discrete function, typically an acceleration profile, will be obtained to force the equipment by simulating the shock event. The synthetizing time and the interface with standards numerical codes will be two of the main topics dealt with in the paper. In addition a congruity and consistency methodology will be presented to ensure that the identified time dependent loads fully match the specified spectrum.

Dynamic Contractility and Efficiency Impairments in Stretch-Shortening Cycle Are Stretch-Load-Dependent After Training-Induced Muscle Damage

NARCIS (Netherlands)

Vaczi, Mark; Racz, Levente; Hortobagyi, Tibor; Tihanyi, Jozsef

Vaczi, M, Racz, L, Hortobagyi, T, and Tihanyi, J. Dynamic contractility and efficiency impairments in stretch-shortening cycle are stretch-load-dependent after training-induced muscle damage. J Strength Cond Res 27(8): 2171-2179, 2013To determine the acute task and stretch-load dependency of

Deflection Prediction of No-Fines Lightweight Concrete Wall Using Neural Network Caused Dynamic Loads

Directory of Open Access Journals (Sweden)

Ridho Bayuaji

2018-04-01

Full Text Available No-fines lightweight concrete wall with horizontal reinforcement refers to an alternative material for wall construction with an aim of improving the wall quality towards horizontal loads. This study is focused on artificial neural network (ANN application to predicting the deflection deformation caused by dynamic loads. The ANN method is able to capture the complex interactions among input/output variables in a system without any knowledge of interaction nature and without any explicit assumption to model form. This paper explains the existing data research, data selection and process of ANN modelling training process and validation. The results of this research show that the deformation can be predicted more accurately, simply and quickly due to the alternating horizontal loads.

Stochastic rocket dynamics under random nozzle side loads: Ornstein-Uhlenbeck boundary layer separation and its coarse grained connection to side loading and rocket response

Energy Technology Data Exchange (ETDEWEB)

Keanini, R.G.; Srivastava, N.; Tkacik, P.T. [Department of Mechanical Engineering, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28078 (United States); Weggel, D.C. [Department of Civil and Environmental Engineering, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28078 (United States); Knight, P.D. [Mitchell Aerospace and Engineering, Statesville, North Carolina 28677 (United States)

2011-06-15

A long-standing, though ill-understood problem in rocket dynamics, rocket response to random, altitude-dependent nozzle side-loads, is investigated. Side loads arise during low altitude flight due to random, asymmetric, shock-induced separation of in-nozzle boundary layers. In this paper, stochastic evolution of the in-nozzle boundary layer separation line, an essential feature underlying side load generation, is connected to random, altitude-dependent rotational and translational rocket response via a set of simple analytical models. Separation line motion, extant on a fast boundary layer time scale, is modeled as an Ornstein-Uhlenbeck process. Pitch and yaw responses, taking place on a long, rocket dynamics time scale, are shown to likewise evolve as OU processes. Stochastic, altitude-dependent rocket translational motion follows from linear, asymptotic versions of the full nonlinear equations of motion; the model is valid in the practical limit where random pitch, yaw, and roll rates all remain small. Computed altitude-dependent rotational and translational velocity and displacement statistics are compared against those obtained using recently reported high fidelity simulations [Srivastava, Tkacik, and Keanini, J. Appl. Phys. 108, 044911 (2010)]; in every case, reasonable agreement is observed. As an important prelude, evidence indicating the physical consistency of the model introduced in the above article is first presented: it is shown that the study's separation line model allows direct derivation of experimentally observed side load amplitude and direction densities. Finally, it is found that the analytical models proposed in this paper allow straightforward identification of practical approaches for: (i) reducing pitch/yaw response to side loads, and (ii) enhancing pitch/yaw damping once side loads cease. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Beam dynamics in THz dielectric-loaded waveguides for the AXSIS project

Science.gov (United States)

Vinatier, T.; Assmann, R. W.; Dorda, U.; Lemery, F.; Marchetti, B.

2017-07-01

In this paper, we investigate with ASTRA simulations the beam dynamics in dielectric-loaded waveguides driven by THz pulses, used as linac structure for the AXSIS project. We show that the bunch properties at the linac exit are very sensitive to the phase velocity of the THz pulse and are limited by the strong phase slippage of the bunch respective to it. We also show that the bunch properties are optimized when low frequencies (ERC Grant Agreement n. 609920.

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...

Controllability of Free-piston Stirling Engine/linear Alternator Driving a Dynamic Load

Science.gov (United States)

Kankam, M. David; Rauch, Jeffrey S.

1994-01-01

This paper presents the dynamic behavior of a Free-Piston Stirling Engine/linear alternator (FPSE/LA) driving a single-phase fractional horse-power induction motor. The controllability and dynamic stability of the system are discussed by means of sensitivity effects of variations in system parameters, engine controller, operating conditions, and mechanical loading on the induction motor. The approach used expands on a combined mechanical and thermodynamic formulation employed in a previous paper. The application of state-space technique and frequency domain analysis enhances understanding of the dynamic interactions. Engine-alternator parametric sensitivity studies, similar to those of the previous paper, are summarized. Detailed discussions are provided for parametric variations which relate to the engine controller and system operating conditions. The results suggest that the controllability of a FPSE-based power system is enhanced by proper operating conditions and built-in controls.

Fluid and structural dynamics calculations to determine core barrel loads during blowdown (EV 3,000)

International Nuclear Information System (INIS)

Krieg, R.; Schlechtendahl, E.G.

1977-01-01

To begin with, the main physical phenomena in connection with blowdown loads on the care barrel and the computer models used are briefly described. These models have also been used in the design of the HTR test care barrel. The fluid dynamics part of the calculations was carried out using the WHAMMOD and DAPSY codes; for the structural dynamics part, the STRUDL/Dynal code was employed. (orig./RW) [de

Analyzing the effect of dynamic loads on economic dispatch in the presence of interline power flow controller using modified BAT algorithm

Directory of Open Access Journals (Sweden)

Y.N. Vijay Kumar

2016-05-01

Full Text Available Now a day, non-uniform increase of demand on a power system turns the research toward the dynamic analysis. In this paper, to perform dynamic analysis and to solve economic load dispatch problem using optimal power flow (OPF, four realistic load levels are considered. Further, the effectiveness of the objective has been enhanced in the presence of interline power flow controller (IPFC. An optimal location identification methodology for IPFC based on line stability index (LSI is also presented. The effect of ramp-rate limits on generations and the effect of dynamic loads on generation fuel cost and transmission losses are also analyzed on standard IEEE-30 bus and real time 23 bus test systems with supporting validations, numerical and graphical results.

The Response of Simple Polymer Structures Under Dynamic Loading

Science.gov (United States)

Proud, William; Ellison, Kay; Yapp, Su; Cole, Cloe; Galimberti, Stefano; Institute of Shock Physics Team

2017-06-01

The dynamic response of polymeric materials has been widely studied with the effects of degree of crystallinity, strain rate, temperature and sample size being commonly reported. This study uses a simple PMMA structure, a right cylindrical sample, with structural features such as holes. The features are added an varied in a systematic fashion. Samples were dynamically loaded using a Split Hopkinson Pressure Bar up to failure. The resulting stress-strain curves are presented showing the change in sample response. The strain to failure is shown to increase initially with the presence of holes, while failure stress is relatively unaffected. The fracture patterns seen in the failed samples change, with tensile cracks, Hertzian cones, shear effects being dominant for different holes sizes and geometries. The sample were prepared by laser cutting and checked for residual stress before experiment. The data is used to validate predictive model predictions where material, structure and damage are included.. The Institute of Shock Physics acknowledges the support of Imperial College London and the Atomic Weapons Establishment.

Investigation of Dynamic Friction Induced by Shock Loading Conditions

International Nuclear Information System (INIS)

Juanicotena, A.; Szarzynski, S.

2006-01-01

Modeling the frictional sliding of one surface against another under high pressure is often required to correctly describe the response of complex systems to shock loading. In order to provide data for direct code and model comparison, a new friction experiment investigating dry sliding characteristics of metal on metal at normal pressures up to 10 GPa and sliding velocities up to 400 m/s has been developed. The test consists of a specifically designed target made of two materials. A plane shock wave generated by plate impact results in one material sliding against the other. The material velocity of the rear surface of the target is recorded versus time by Doppler Laser Interferometry. The dynamic friction coefficient μ is then indirectly determined by comparison with results of numerical simulations involving the conventional Coulomb law. Using this new experimental configuration, three dynamic friction experiments were performed on AA 5083-Al (H111) / AISI 321 stainless steel tribo-pair. Results suggest a decrease in the friction coefficient with increasing sliding velocity

Assessing pharmacokinetics of indocyanine green-loaded nanoparticle in tumor with a dynamic diffuse fluorescence tomography system

Science.gov (United States)

Zhang, Yanqi; Yin, Guoyan; Zhao, Huijuan; Ma, Wenjuan; Gao, Feng; Zhang, Limin

2018-02-01

Real-time and continuous monitoring of drug release in vivo is an important task in pharmaceutical development. Here, we devoted to explore a real-time continuous study of the pharmacokinetics of free indocyanine green (ICG) and ICG loaded in the shell-sheddable nanoparticles in tumor based on a dynamic diffuse fluorescence tomography (DFT) system: A highly-sensitive dynamic DFT system of CT-scanning mode generates informative and instantaneous sampling datasets; An analysis procedure extracts the pharmacokinetic parameters from the reconstructed time curves of the mean ICG concentration in tumor, using the Gauss-Newton scheme based on two-compartment model. Compared with the pharmacokinetic parameters of free ICG in tumor, the ICG loaded in the shell-sheddable nanoparticles shows efficient accumulation in tumor. The results demonstrate our proposed dynamic-DFT can provide an integrated and continuous view of the drug delivery of the injected agents in different formulations, which is helpful for the development of diagnosis and therapy for tumors.

Dynamic Strength and Accumulated Plastic Strain Development Laws and Models of the Remolded Red Clay under Long-Term Cyclic Loads: Laboratory Test Results

Directory of Open Access Journals (Sweden)

Li Jian

2015-09-01

Full Text Available The dynamic strength and accumulated plastic strain are two important parameters for evaluating the dynamic response of soil. As a special clay, the remolded red clay is often used as the high speed railway subgrade filling, but studies on its dynamic characteristics are few. For a thorough analysis of the suitability of the remolded red clay as the subgrade filling, a series of long-term cyclic load triaxial test under different load histories are carried out. Considering the influence of compactness, confining pressure, consolidation ratio, vibration frequency and dynamic load to the remolded red clay dynamic property, the tests obtain the development curves of the dynamic strength and accumulated plastic strain under different test conditions. Then, through curve fitting method, two different hyperbolic models respectively for the dynamic strength and accumulated plastic strain are built, which can match the test datum well. By applying the dynamic strength model, the critical dynamic strength of the remolded red clay are gained. Meanwhile, for providing basic datum and reference for relevant projects, all key parameters for the dynamic strength and accumulated plastic strain of the remolded red clay are given in the paper.

Normal dynamic deformation characteristics of non-consecutive jointed rock masses under impact loads

Science.gov (United States)

Zeng, Sheng; Jiang, Bowei; Sun, Bing

2017-08-01

In order to study deformation characteristics of non-consecutive single jointed rock masses under impact loads, we used the cement mortar materials to make simulative jointed rock mass samples, and tested the samples under impact loads by the drop hammer. Through analyzing the time-history signal of the force and the displacement, first we find that the dynamic compression displacement of the jointed rock mass is significantly larger than that of the intact jointless rock mass, the compression displacement is positively correlated with the joint length and the impact height. Secondly, the vertical compressive displacement of the jointed rock mass is mainly due to the closure of opening joints under small impact loads. Finally, the peak intensity of the intact rock mass is larger than that of the non-consecutive jointed rock mass and negatively correlated with the joint length under the same impact energy.

Study on dynamic measurement of fuel pellet length during loading into cladding tube

International Nuclear Information System (INIS)

Zhang Kai

1993-09-01

Various methods are presented for measuring the pellet length in the cladding tube (zirconium tube) during the loading process of the preparation of single rod of nuclear fuel assembly. These methods are used in former Soviet Union, west European countries and China in the manufacturing of nuclear power plant element. Different methods of dynamic measurement by using mechanics, optics and electricity and their special features are analysed and discussed. The structure and measuring principle of a developed measuring device,and its measuring precision and system deviation are also introduced. Finally, the length of loaded pellets is checked with analog pellets. The results are as expected and show that the method and principle used in the measuring device are feasible. It is an ideal and advanced method for the pellet loading of single cladding tube. The principle mentioned above can also be used in other industries

Dynamic Load Measurement of Ballistic Gelatin Impact Using an Instrumented Tube

Science.gov (United States)

Seidt, J. D.; Periira, J. M.; Hammer, J. T.; Gilat, A.; Ruggeri, C. R.

2012-01-01

Bird strikes are a common problem for the aerospace industry and can cause serious damage to an aircraft. Ballistic gelatin is frequently used as a surrogate for actual bird carcasses in bird strike tests. Numerical simulations of these tests are used to supplement experimental data, therefore it is necessary to use numerical modeling techniques that can accurately capture the dynamic response of ballistic gelatin. An experimental technique is introduced to validate these modeling techniques. A ballistic gelatin projectile is fired into a strike plate attached to a 36 in. long sensor tube. Dynamic load is measured at two locations relative to the strike plate using strain gages configured in a full Wheatstone bridge. Data from these experiments are used to validate a gelatin constitutive model. Simulations of the apparatus are analyzed to investigate its performance.

Dynamics of a Circular Mindlin Plate under Mechanical Loading and Elevated Temperature

Directory of Open Access Journals (Sweden)

Warminska Anna

2016-01-01

Full Text Available Dynamics of a nonlinear circular Midlin plate is studied in the paper. The mathematical model represented by partial differential equations includes nonlinear geometrical terms resulted from large displacements. The plate is subjected to mechanical and thermal loadings. The dynamics of a coupled thermo-mechanical problem is reduced from partial to ordinary differential equations. Considering the first mode reduction and uniformly distributed temperature just a single nonlinear differential equation is obtained. The bifurcation analysis shows that elevated temperature shifts the rezonanse curve and new solutions arise. Depending on initial conditions this may lead to buckling phenomenon and then relatively small oscillations around this state, symmetric periodic oscillations of large amplitude, or irregular oscillations.

Discrete meso-element simulation of the failure behavior of short-fiber composites under dynamic loading

International Nuclear Information System (INIS)

Liu Wenyan; Tang, Z.P.; Liu Yunxin

2000-01-01

In recent years, more attention has been paid to a better understanding of the failure behavior and mechanism of heterogeneous materials at the meso-scale level. In this paper, the crack initiation and development in epoxy composites reinforced with short steel fibers under dynamic loading were simulated and analyzed with the 2D Discrete Meso-Element Dynamic Method. Results show that the damage process depends greatly on the binding property between matrix and fibers

Estimation of structural reliability under combined loads

International Nuclear Information System (INIS)

Shinozuka, M.; Kako, T.; Hwang, H.; Brown, P.; Reich, M.

1983-01-01

For the overall safety evaluation of seismic category I structures subjected to various load combinations, a quantitative measure of the structural reliability in terms of a limit state probability can be conveniently used. For this purpose, the reliability analysis method for dynamic loads, which has recently been developed by the authors, was combined with the existing standard reliability analysis procedure for static and quasi-static loads. The significant parameters that enter into the analysis are: the rate at which each load (dead load, accidental internal pressure, earthquake, etc.) will occur, its duration and intensity. All these parameters are basically random variables for most of the loads to be considered. For dynamic loads, the overall intensity is usually characterized not only by their dynamic components but also by their static components. The structure considered in the present paper is a reinforced concrete containment structure subjected to various static and dynamic loads such as dead loads, accidental pressure, earthquake acceleration, etc. Computations are performed to evaluate the limit state probabilities under each load combination separately and also under all possible combinations of such loads

Variability in dynamic properties of tantalum : spall, attenuation and load/unload.

Energy Technology Data Exchange (ETDEWEB)

Furnish, Michael David; Reinhart, William Dodd; Trott, Wayne Merle; Vogler, Tracy John; Chhabildas, Lalit Chandra

2005-07-01

A suite of impact experiments was conducted to assess spatial and shot-to-shot variability in dynamic properties of tantalum. Samples had a uniform refined {approx}20 micron grain structure with a strong axisymmetric [111] crystallographic texture. Two experiments performed with sapphire windows (stresses of approximately 7 and 12 GPa) clearly showed elastic-plastic loading and slightly hysteretic unloading behavior. An HEL amplitude of 2.8 GPa (corresponding to Y 1.5 GPa) was observed. Free-surface spall experiments showed clear wave attenuation and spallation phenomena. Here, loading stresses were {approx} 12.5 GPa and various ratios of impactor to target thicknesses were used. Spatial and shot-to-shot variability of the spall strength was {+-} 20%, and of the HEL, {+-} 10%. Experiments conducted with smaller diameter flyer plates clearly showed edge effects in the line and point VISAR records, indicating lateral release speeds of roughly 5 km/s.

Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

Science.gov (United States)

Zhu, Yafei; McCowan, Andrew; Cook, Perran L. M.

2017-10-01

The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes) were investigated using a 3-D coupled hydrodynamic biogeochemical water quality model. The study showed that primary production was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment were the main drivers for the hypoxia and subsequent sediment phosphorus release in Lake King. High primary production stimulated by large nitrogen loading brought on by a winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads), which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria). Therefore, the current study highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.

Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

Directory of Open Access Journals (Sweden)

Y. Zhu

2017-10-01

Full Text Available The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes were investigated using a 3-D coupled hydrodynamic biogeochemical water quality model. The study showed that primary production was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment were the main drivers for the hypoxia and subsequent sediment phosphorus release in Lake King. High primary production stimulated by large nitrogen loading brought on by a winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads, which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria. Therefore, the current study highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.

Testing of tunnel support: dynamic load testing of rock support containment systems (eg wire mesh).

CSIR Research Space (South Africa)

Ortlepp, WD

1997-07-01

Full Text Available The objective of this project was to determine the performance characteristics of containment elements of tunnel support in common use in South African mines under dynamic loading. The magnitude of the energy levels in this testing had...

Compressive Loads on the Lumbar Spine During Lifting: 4D WATBAK versus Inverse Dynamics Calculations

Directory of Open Access Journals (Sweden)

M. H. Cole

2005-01-01

Full Text Available Numerous two- and three-dimensional biomechanical models exist for the purpose of assessing the stresses placed on the lumbar spine during the performance of a manual material handling task. More recently, researchers have utilised their knowledge to develop specific computer-based models that can be applied in an occupational setting; an example of which is 4D WATBAK. The model used by 4D WATBAK bases its predications on static calculations and it is assumed that these static loads reasonably depict the actual dynamic loads acting on the lumbar spine. Consequently, it was the purpose of this research to assess the agreement between the static predictions made by 4D WATBAK and those from a comparable dynamic model. Six individuals were asked to perform a series of five lifting tasks, which ranged from lifting 2.5 kg to 22.5 kg and were designed to replicate the lifting component of the Work Capacity Assessment Test used within Australia. A single perpendicularly placed video camera was used to film each performance in the sagittal plane. The resultant two-dimensional kinematic data were input into the 4D WATBAK software and a dynamic biomechanical model to quantify the compression forces acting at the L4/L5 intervertebral joint. Results of this study indicated that as the mass of the load increased from 2.5 kg to 22.5 kg, the static compression forces calculated by 4D WATBAK became increasingly less than those calculated using the dynamic model (mean difference ranged from 22.0% for 2.5 kg to 42.9% for 22.5 kg. This study suggested that, for research purposes, a validated three-dimensional dynamic model should be employed when a task becomes complex and when a more accurate indication of spinal compression or shear force is required. Additionally, although it is clear that 4D WATBAK is particularly suited to industrial applications, it is suggested that the limitations of such modelling tools be carefully considered when task-risk and employee

Chaotic Dynamics of the Partially Follower-Loaded Elastic Double Pendulum

DEFF Research Database (Denmark)

Thomsen, Jon Juel

1995-01-01

The non-linear dynamics of the elastically restrained double pendulum, with non-conservative follower-type loading and linear damping, is re-examined with specific reference to the occurrence of chaotic motion. A local non-linear perturbation analysis is performed, showing that in three distinct ...... by both linear and non-linear forces. Although heuristically based, this may be used as a practical and rather accurate predictive criterion for chaos to appear in the specific system. Copyright © 1995 Academic Press. All rights reserved....... regions of loading parameter space, small initial disturbances will result in, respectively, (1) static equilibrium solutions, (2) stable periodic motion, and (3) initially large changes in amplitude due to a destabilizing effect of both linear and non-linear forces. A global numerical analysis confirms...... the theoretical findings for regions (1) and (2), and shows that in region (3) almost all solutions are chaotic. It is suggested that chaos is triggered by a bifurcating cascade of large amplitude stable and unstable equilibrium points, which may be explored by orbits only when the zero-solution is destabilized...

Theoretical Analysis of the Dynamic Properties of a 2-2 Cement-Based Piezoelectric Dual-Layer Stacked Sensor under Impact Load.

Science.gov (United States)

Zhang, Taotao; Liao, Yangchao; Zhang, Keping; Chen, Jun

2017-05-04

Cement-based piezoelectric materials are widely used due to the fact that compared with common smart materials, they overcome the defects of structure-incompatibility and frequency inconsistency with a concrete structure. However, the present understanding of the mechanical behavior of cement-based piezoelectric smart materials under impact load is still limited. The dynamic characteristics under impact load are of importance, for example, for studying the anti-collision properties of engineering structures and aircraft takeoff-landing safety. Therefore, in this paper, an analytical model was proposed to investigate the dynamic properties of a 2-2 cement-based piezoelectric dual-layer stacked sensor under impact load based on the piezoelectric effect. Theoretical solutions are obtained by utilizing the variable separation and Duhamel integral method. To simulate the impact load and verify the theory, three types of loads, including atransient step load, isosceles triangle load and haversine wave load, are considered and the comparisons between the theoretical results, Li's results and numerical results are presented by using the control variate method and good agreement is found. Furthermore, the influences of several parameters were discussed and other conclusions about this sensor are also given. This should prove very helpful for the design and optimization of the 2-2 cement-based piezoelectric dual-layer stacked sensor in engineering.

Tests and calculations of reinforced concrete beams subject to dynamic reversed loads

International Nuclear Information System (INIS)

Livolant, M.; Hoffmann, A.; Gauvain, J.

1978-01-01

This study presents the tests of a reinforced concrete beam conducted by the Department of Mechanical and Thermal Studies at the Centre d'Etudes Nucleaires, Saclay, France. The actual behavior of nuclear power plant buildings submitted to seismic loads is generally non linear even for moderate seismic levels. The non linearity is specially important for reinforced concrete beams type buildings. To estimate the safety factors when the building is designed by standard methods, accurate non linear calculations are necessary. For such calculations one of the most difficult point is to define a correct model for the behavior of a reinforced beam subject to reversed loads. For that purpose, static and dynamic experimental tests on a shaking table have been carried out and a model reasonably accurate has been established and checked on the tests results

Dynamic Response of a Beam Resting on a Nonlinear Foundation to a Moving Load: Coiflet-Based Solution

Directory of Open Access Journals (Sweden)

Piotr Koziol

2012-01-01

Full Text Available This paper presents a new semi-analytical solution for the Timoshenko beam subjected to a moving load in case of a nonlinear medium underneath. The finite series of distributed moving loads harmonically varying in time is considered as a representation of a moving train. The solution for vibrations is obtained by using the Adomian's decomposition combined with the Fourier transform and a wavelet-based procedure for its computation. The adapted approximating method uses wavelet filters of Coiflet type that appeared a very effective tool for vibration analysis in a few earlier papers. The developed approach provides solutions for both transverse displacement and angular rotation of the beam, which allows parametric analysis of the investigated dynamic system to be conducted in an efficient manner. The aim of this article is to present an effective method of approximation for the analysis of complex dynamic nonlinear models related to the moving load problems.

Dynamic loads on human and animal surrogates at different test locations in compressed-gas-driven shock tubes

Science.gov (United States)

Alay, E.; Skotak, M.; Misistia, A.; Chandra, N.

2018-01-01

Dynamic loads on specimens in live-fire conditions as well as at different locations within and outside compressed-gas-driven shock tubes are determined by both static and total blast overpressure-time pressure pulses. The biomechanical loading on the specimen is determined by surface pressures that combine the effects of static, dynamic, and reflected pressures and specimen geometry. Surface pressure is both space and time dependent; it varies as a function of size, shape, and external contour of the specimens. In this work, we used two sets of specimens: (1) anthropometric dummy head and (2) a surrogate rodent headform instrumented with pressure sensors and subjected them to blast waves in the interior and at the exit of the shock tube. We demonstrate in this work that while inside the shock tube the biomechanical loading as determined by various pressure measures closely aligns with live-fire data and shock wave theory, significant deviations are found when tests are performed outside.

Dynamic Analysis of Cable-Stayed Bridges Affected by Accidental Failure Mechanisms under Moving Loads

Directory of Open Access Journals (Sweden)

Fabrizio Greco

2013-01-01

Full Text Available The dynamic behavior of cable-stayed bridges subjected to moving loads and affected by an accidental failure in the cable suspension system is investigated. The main aim of the paper is to quantify, numerically, the dynamic amplification factors of typical kinematic and stress design variables, by means of a parametric study developed in terms of the structural characteristics of the bridge components. The bridge formulation is developed by using a geometric nonlinear formulation, in which the effects of local vibrations of the stays and of large displacements in the girder and the pylons are taken into account. Explicit time dependent damage laws, reproducing the failure mechanism in the cable system, are considered to investigate the influence of the failure mode characteristics on the dynamic bridge behavior. The analysis focuses attention on the influence of the inertial characteristics of the moving loads, by accounting coupling effects arising from the interaction between girder and moving system. Sensitivity analyses of typical design bridge variables are proposed. In particular, the effects produced by the moving system characteristics, the tower typologies, and the failure mode characteristics involved in the cable system are investigated by means of comparisons between damaged and undamaged bridge configurations.

Calculation of equivalent static loads and its application

International Nuclear Information System (INIS)

Choi, Woo-Seok; Park, K.B.; Park, G.J.

2005-01-01

All the forces in the real world act dynamically on structures. Since dynamic loads are extremely difficult to handle in analysis and design, static loads are usually utilized with dynamic factors. Generally, the dynamic factors are determined from design codes or experience. Therefore, static loads may not give accurate solutions in analysis and design and structural engineers often come up with unreliable solutions. Two different methods are proposed for the transformation of dynamic loads into equivalent static loads (ESLs). One is an analytical method for exact ESLs and the other is an approximation method. The exact ESLs are calculated to generate identical response fields such as displacement and stress with those from dynamic loads at a certain time. Some approximation methods are proposed in engineering applications, which generate similar response fields from dynamic loads. They are divided into the displacement-based approach and the stress-based approach. The process is derived and evaluated mathematically. Standard examples are selected and solved by the proposed method and error analyses are conducted. Applications of the method to structural optimization are discussed

Aggregated Residential Load Modeling Using Dynamic Bayesian Networks

Energy Technology Data Exchange (ETDEWEB)

Vlachopoulou, Maria; Chin, George; Fuller, Jason C.; Lu, Shuai

2014-09-28

Abstract—It is already obvious that the future power grid will have to address higher demand for power and energy, and to incorporate renewable resources of different energy generation patterns. Demand response (DR) schemes could successfully be used to manage and balance power supply and demand under operating conditions of the future power grid. To achieve that, more advanced tools for DR management of operations and planning are necessary that can estimate the available capacity from DR resources. In this research, a Dynamic Bayesian Network (DBN) is derived, trained, and tested that can model aggregated load of Heating, Ventilation, and Air Conditioning (HVAC) systems. DBNs can provide flexible and powerful tools for both operations and planing, due to their unique analytical capabilities. The DBN model accuracy and flexibility of use is demonstrated by testing the model under different operational scenarios.

Dynamic mechanical behaviour of nanoparticle loaded biodegradable PVA films for vaginal drug delivery.

Science.gov (United States)

Traore, Yannick L; Fumakia, Miral; Gu, Jijin; Ho, Emmanuel A

2018-03-01

In this study, we investigated the viscoelastic and mechanical behaviour of polyvinyl alcohol films formulated along with carrageenan, plasticizing agents (polyethylene glycol and glycerol), and when loaded with nanoparticles as a model for potential applications as microbicides. The storage modulus, loss modulus and glass transition temperature were determined using a dynamic mechanical analyzer. Films fabricated from 2% to 5% polyvinyl alcohol containing 3 mg or 5 mg of fluorescently labeled nanoparticles were evaluated. The storage modulus and loss modulus values of blank films were shown to be higher than the nanoparticle-loaded films. Glass transition temperature determined using the storage modulus, and loss modulus was between 40-50℃ and 35-40℃, respectively. The tensile properties evaluated showed that 2% polyvinyl alcohol films were more elastic but less resistant to breaking compared to 5% polyvinyl alcohol films (2% films break around 1 N load and 5% films break around 7 N load). To our knowledge, this is the first study to evaluate the influence of nanoparticle and film composition on the physico-mechanical properties of polymeric films for vaginal drug delivery.

Quasi-static structural optimization under the seismic loads

International Nuclear Information System (INIS)

Choi, W. S.; Lee, K. M.; Kim, T. W.

2001-01-01

For preliminaries to optimization of SMART under the seismic loads, a quasi-static structural optimization for elastic structures under dynamic loads is presented. An equivalent static load (ESL) set is defined as a static load set, which generates the same displacement field as that from a dynamic load at a certain time. Multiple ESL sets calculated at all the time intervals are employed to represent the various states of the structure under the dynamic load. They can cover all the critical states that might happen at arbitrary times. The continuous characteristics of a dynamic load are considered by multiple static load sets. The calculated sets of ESLs are utilized as a multiple loading condition in the optimization process. A design cycle is defined as a circulated process between an analysis domain and a design domain. The analysis domain gives the loading condition needed in the design domain. The design domain gives a new updated design to be verified by the analysis domain in the next design cycle. The design cycles are iterated until the design converges. Structural optimization with dynamic loads is tangible by the proposed method. Standard example problems are solved to verify the validity of the method

Dynamic Response of AP1000 Nuclear Island Due to Safe Shutdown Earthquake Loading

Directory of Open Access Journals (Sweden)

Gan Buntara S.

2017-01-01

Full Text Available AP1000 is a standard nuclear power plant developed by Westinghouse and its partners by using an advanced passive safety feature. Among the five principle building structures, namely the nuclear island, turbine building, annex building, diesel generator building and radwaste building, the safety of the nuclear island building is the most concerned. This paper investigates the dynamic response of the nuclear island building of the AP1000 plant subjected to safe shutdown earthquake loadings. A finite element model for the building, which is assumed to be built in a hard-rock base, is developed and its dynamic response is computed with the aid of the commercial finite element package ANSYS. The dynamic characteristics, including the natural frequencies, the vibration modes, and the time histories for displacements, velocities, and accelerations of the building are obtained for two typical safe shutdown earthquakes, El Centro and Kobe earthquakes. The dynamic behavior of the building due to the earthquakes and its safety is examined and highlighted.

Failure mechanism and coupled static-dynamic loading theory in deep hard rock mining: A review

Directory of Open Access Journals (Sweden)

Xibing Li

2017-08-01

Full Text Available Rock failure phenomena, such as rockburst, slabbing (or spalling and zonal disintegration, related to deep underground excavation of hard rocks are frequently reported and pose a great threat to deep mining. Currently, the explanation for these failure phenomena using existing dynamic or static rock mechanics theory is not straightforward. In this study, new theory and testing method for deep underground rock mass under coupled static-dynamic loading are introduced. Two types of coupled loading modes, i.e. “critical static stress + slight disturbance” and “elastic static stress + impact disturbance”, are proposed, and associated test devices are developed. Rockburst phenomena of hard rocks under coupled static-dynamic loading are successfully reproduced in the laboratory, and the rockburst mechanism and related criteria are demonstrated. The results of true triaxial unloading compression tests on granite and red sandstone indicate that the unloading can induce slabbing when the confining pressure exceeds a certain threshold, and the slabbing failure strength is lower than the shear failure strength according to the conventional Mohr-Column criterion. Numerical results indicate that the rock unloading failure response under different in situ stresses and unloading rates can be characterized by an equivalent strain energy density. In addition, we present a new microseismic source location method without premeasuring the sound wave velocity in rock mass, which can efficiently and accurately locate the rock failure in hard rock mines. Also, a new idea for deep hard rock mining using a non-explosive continuous mining method is briefly introduced.

Enhanced IMC design of load disturbance rejection for integrating and unstable processes with slow dynamics.

Science.gov (United States)

Liu, Tao; Gao, Furong

2011-04-01

In view of the deficiencies in existing internal model control (IMC)-based methods for load disturbance rejection for integrating and unstable processes with slow dynamics, a modified IMC-based controller design is proposed to deal with step- or ramp-type load disturbance that is often encountered in engineering practices. By classifying the ways through which such load disturbance enters into the process, analytical controller formulae are correspondingly developed, based on a two-degree-of-freedom (2DOF) control structure that allows for separate optimization of load disturbance rejection from setpoint tracking. An obvious merit is that there is only a single adjustable parameter in the proposed controller, which in essence corresponds to the time constant of the closed-loop transfer function for load disturbance rejection, and can be monotonically tuned to meet a good trade-off between disturbance rejection performance and closed-loop robust stability. At the same time, robust tuning constraints are given to accommodate process uncertainties in practice. Illustrative examples from the recent literature are used to show effectiveness and merits of the proposed method for different cases of load disturbance. Copyright © 2010. Published by Elsevier Ltd.

A dynamic modelling approach for estimating critical loads of nitrogen based on plant community changes under a changing climate

International Nuclear Information System (INIS)

Belyazid, Salim; Kurz, Dani; Braun, Sabine; Sverdrup, Harald; Rihm, Beat; Hettelingh, Jean-Paul

2011-01-01

A dynamic model of forest ecosystems was used to investigate the effects of climate change, atmospheric deposition and harvest intensity on 48 forest sites in Sweden (n = 16) and Switzerland (n = 32). The model was used to investigate the feasibility of deriving critical loads for nitrogen (N) deposition based on changes in plant community composition. The simulations show that climate and atmospheric deposition have comparably important effects on N mobilization in the soil, as climate triggers the release of organically bound nitrogen stored in the soil during the elevated deposition period. Climate has the most important effect on plant community composition, underlining the fact that this cannot be ignored in future simulations of vegetation dynamics. Harvest intensity has comparatively little effect on the plant community in the long term, while it may be detrimental in the short term following cutting. This study shows: that critical loads of N deposition can be estimated using the plant community as an indicator; that future climatic changes must be taken into account; and that the definition of the reference deposition is critical for the outcome of this estimate. - Research highlights: → Plant community changes can be used to estimate critical loads of nitrogen. → Climate change is decisive for future changes of geochemistry and plant communities. → Climate change cannot be ignored in estimates of critical loads. → The model ForSAFE-Veg was successfully used to set critical loads of nitrogen. - Plant community composition can be used in dynamic modelling to estimate critical loads of nitrogen deposition, provided the appropriate reference deposition, future climate and target plant communities are defined.

Effect of support conditions on structural response under dynamic loading

International Nuclear Information System (INIS)

Akram, T.; Memon, S.A.

2008-01-01

In design practice, dynamic structural analysis is carried out with base of structure considered as fixed; this means that foundation is placed on rock like soil material. While conducting this type of analyses the role of foundation and soil behaviour is totally neglected. The actions in members and loads transferred at foundation level obtained in this manner do not depict the true structural behaviour. FEM (Finite Element Methods) analysis where both superstructure and foundation soil are coupled together is quite complicated and expensive for design environments. A simplified model is required to depict dynamic response of structures with foundations based on flexible soils. The primary purpose of this research is to compare the superstructure dynamic responses of structural systems with fixed base to that of simple soil model base. The selected simple soil model is to be suitable for use in a design environment to give more realistic results. For this purpose building models are idealized with various heights and structural systems in both 2D (Two Dimensional) and 3D (Three Dimensional) space. These models are then provided with visco-elastic supports representing three soil bearing capacities and the analysis results are compared to that of fixed supports models. The results indicate that fixed support system underestimates natural time period of the structures. Dynamic behavior and force response of visco-elastic support is different from fixed support model. Fixed support models result in over designed base columns and under designed beams. (author)

Design and testing of a surface switch for the dynamic load current multiplier on the SPHINX microsecond LTD

International Nuclear Information System (INIS)

Maysonnave, T.; Bayol, F.; Demol, G.; Almeida, T. d'; Morell, A.; Lassalle, F.; Grunenwald, J.; Chuvatin, A.S.; Pecastaing, L.; De Ferron, A.S.

2013-01-01

SPHINX is a microsecond linear transformer driver located at Atomic Energy Commission (CEA) Gramat (France), which can deliver a current pulse of 6 MA within 800 ns in a Z-pinch load. Using the concept of the dynamic load current multiplier (DLCM), which was proposed by Chuvatin, we expect to increase the load current above 6 MA, while decreasing its rise time to ∼300 ns. The DLCM developed by the CEA Gramat and International Technologies for High Pulsed Power (ITHPP) is a compact system made up of concentric electrodes (auto-transformer), a dynamic flux extruder (cylindrical wire array), a vacuum convolute (eight post-hole rods), and a closing switch (compact vacuum surface switch). The latter is a key component of the system, which is used to prevent the current from flowing into the load until the inductance builds up due to the implosion of the wire array. This paper presents the design and testing of the DLCM surface switch, resulting from both electrostatic simulations and experiments on the SPHINX generator. These studies, carried out either with or without load (open circuit), were valuable for a first experimental evaluation of the DLCM scheme in a microsecond regime and provided detailed information on the surface switch behavior. (authors)

Numerical Simulation of Shock Response and Dynamic Fracture of a Concrete Dam Subjected to Impact Load

Directory of Open Access Journals (Sweden)

Lu Lu

2016-01-01

Full Text Available The shock response and dynamic fracture of concrete gravity dams under impact load are the key problems to evaluate the antiknock safety of the dam. This study aims at understanding the effects of impact shock on the elastic response and dynamic fracture of concrete gravity dams. Firstly, this paper uses acceleration records of a concrete gravity dam under impact to establish the correct way to determine the concrete gravity dam of the fundamental frequency and present cut sheets multi-degree-of-freedom dynamic modeling. Under strong impact loading, the constitutive relation of concrete gravity dam and the highest frequency of the impact are uncertain. So, the main advantage of this method is avoiding the use of elastic modulus in the calculation. The result indicates that the calculation method is a reliable computational method for concrete gravity dams subjected to impact. Subsequently, the failure process of dam models was numerically simulated based on ABAQUS commercial codes. Finally, this paper puts forward suggestions for future research based on the results of the analysis.

Mechanical Assessment of the Drip Shield Subject to Vibratory Motion and Dynamic and Static Rock Loading

International Nuclear Information System (INIS)

R.C. Quittmeyer

2005-01-01

The purpose of the drip shield (DS) is to divert water that may seep into emplacement drifts from contacting the waste packages, and to protect the waste packages from impact or static loading from rockfall. The objective of this document is to summarize, into one location, the results of a series of supporting engineering calculations that were developed to study the effect of static and dynamic loads on the mechanical performance of the DS. The potential DS loads are a result of: (1) Potential earthquake vibratory ground motion, and resulting interaction of the DS, waste package and pallet, and drift invert; (2) Dynamic impacts of rockfall resulting from emplacement drift damage as a result of earthquake vibratory motion; and (3) Static load of the caved rock rubble that may come to rest on the DS as a result of vibratory motion or from time-dependent yielding of the rock mass surrounding the emplacement drift. The potential mechanical failure mechanisms that may result from these loads include: (1) Overturning and/or separation of the interlocking DS segments; (2) Loss of structural integrity and stability of the DS, including excessive deformation or buckling; and (3) Localized damage to the top and side-wall plates of the DS. The scope of this document is limited to summarizing results presented in the supporting calculations in the areas of analysis of the potential for DS collapse, and determination of the damaged surface area of the DS plates. New calculations are presented to determine whether or not separation of DSs occur under vibratory motion

Dynamic response of infrastructure to environmentally induced loads analysis, measurements, testing, and design

CERN Document Server

Manolis, George

2017-01-01

This book provides state of the art coverage of important current issues in the analysis, measurement, and monitoring of the dynamic response of infrastructure to environmental loads, including those induced by earthquake motion and differential soil settlement. The coverage is in five parts that address numerical methods in structural dynamics, soil–structure interaction analysis, instrumentation and structural health monitoring, hybrid experimental mechanics, and structural health monitoring for bridges. Examples that give an impression of the scope of the topics discussed include the seismic analysis of bridges, soft computing in earthquake engineering, use of hybrid methods for soil–structure interaction analysis, effects of local site conditions on the inelastic dynamic analysis of bridges, embedded models in wireless sensor networks for structural health monitoring, recent developments in seismic simulation methods, and seismic performance assessment and retrofit of structures. Throughout, the empha...

Theoretical Analysis of the Dynamic Properties of a 2-2 Cement-Based Piezoelectric Dual-Layer Stacked Sensor under Impact Load

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Taotao Zhang

2017-05-01

Full Text Available Cement-based piezoelectric materials are widely used due to the fact that compared with common smart materials, they overcome the defects of structure-incompatibility and frequency inconsistency with a concrete structure. However, the present understanding of the mechanical behavior of cement-based piezoelectric smart materials under impact load is still limited. The dynamic characteristics under impact load are of importance, for example, for studying the anti-collision properties of engineering structures and aircraft takeoff-landing safety. Therefore, in this paper, an analytical model was proposed to investigate the dynamic properties of a 2-2 cement-based piezoelectric dual-layer stacked sensor under impact load based on the piezoelectric effect. Theoretical solutions are obtained by utilizing the variable separation and Duhamel integral method. To simulate the impact load and verify the theory, three types of loads, including atransient step load, isosceles triangle load and haversine wave load, are considered and the comparisons between the theoretical results, Li’s results and numerical results are presented by using the control variate method and good agreement is found. Furthermore, the influences of several parameters were discussed and other conclusions about this sensor are also given. This should prove very helpful for the design and optimization of the 2-2 cement-based piezoelectric dual-layer stacked sensor in engineering.

Identification of Dynamic Loads Based on Second-Order Taylor-Series Expansion Method

OpenAIRE

Li, Xiaowang; Deng, Zhongmin

2016-01-01

A new method based on the second-order Taylor-series expansion is presented to identify the structural dynamic loads in the time domain. This algorithm expresses the response vectors as Taylor-series approximation and then a series of formulas are deduced. As a result, an explicit discrete equation which associates system response, system characteristic, and input excitation together is set up. In a multi-input-multi-output (MIMO) numerical simulation study, sinusoidal excitation and white no...

Response of Rubble Foundation to Dynamic Loading

DEFF Research Database (Denmark)

Burcharth, H. F.; Ibsen, Lars Bo

1993-01-01

The soil beneath vertical monolithic structures is subjected to a combination of static load due to the submerged weight of the structure and stochastic non-stationary loads as a result of the wave loads on the vertical wall. The stress conditions in the soil below a foundation exposed to both...

Response of Rubble Foundation to Dynamic Loading

DEFF Research Database (Denmark)

Burcharth, H. F.; Ibsen, Lars Bo

1994-01-01

The soil beneath vertical monolithic structures is subjected to a combination of static load due to the submerged weight of the structure and stochastic non-stationary loads as a result of the wave loads on the vertical wall. The stress conditions in the soil below a foundation exposed to both...

An efficient dynamic load balancing algorithm

Science.gov (United States)

Lagaros, Nikos D.

2014-01-01

In engineering problems, randomness and uncertainties are inherent. Robust design procedures, formulated in the framework of multi-objective optimization, have been proposed in order to take into account sources of randomness and uncertainty. These design procedures require orders of magnitude more computational effort than conventional analysis or optimum design processes since a very large number of finite element analyses is required to be dealt. It is therefore an imperative need to exploit the capabilities of computing resources in order to deal with this kind of problems. In particular, parallel computing can be implemented at the level of metaheuristic optimization, by exploiting the physical parallelization feature of the nondominated sorting evolution strategies method, as well as at the level of repeated structural analyses required for assessing the behavioural constraints and for calculating the objective functions. In this study an efficient dynamic load balancing algorithm for optimum exploitation of available computing resources is proposed and, without loss of generality, is applied for computing the desired Pareto front. In such problems the computation of the complete Pareto front with feasible designs only, constitutes a very challenging task. The proposed algorithm achieves linear speedup factors and almost 100% speedup factor values with reference to the sequential procedure.

Electric Resistance Tests on Compacted Clay Material under Dynamic Load Coupled with Dry-Wet Cycling

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Zheng Lu

2018-01-01

Full Text Available The study of compacted clay material under dynamic load coupled with dry-wet cycling is one of the most important areas in the field of transportation. In this paper, experiments in terms of compacted clay under dynamic load coupled with dry-wet cycling are performed, and synchronous resistivity tests are also conducted. According to the test results, the influences of cumulative plastic strain, dry-wet cycles, and amplitudes on the soil resistivity are analyzed. Then a new damage factor based on resistivity is proposed to evaluate the long-term performance of compacted clay material. The result of research shows that the evolution of the soil resistivity can be divided into two stages, which has a contrary tendency with that of cumulative plastic strain. The dry-wet cycles and amplitudes have a significant effect on the damage of the compacted soil, which indicates that the dry-wet cycling of compacted soil materials should not be ignored in road engineering, especially in rainy and humid areas.

Dead zone analysis of ECAL barrel modules under static and dynamic load

Science.gov (United States)

Pierre-Emile, T.; Anduze, M.

2018-03-01

In the context of ILD project, impact studies of environmental loads on the Electromagnetic CALorimeter (ECAL) have been initiated. The ECAL part considered is the barrel and it consists of several independent modules which are mounted on the Hadronic CALorimeter barrel (HCAL) itself mounted on the cryostat coil and the yoke. The estimate of the gap required between each ECAL modules is fundamental to define the assembly step and avoid mechanical contacts over the barrel lifetime. In the meantime, it has to be done in consideration to the dead spaces reduction and detector hermiticity optimization. Several Finite Element Analysis (FEA) with static and dynamic loads have been performed in order to define correctly the minimum values for those gaps. Due to the implantation site of the whole project in Japan, seismic analysis were carried out in addition to the static ones. This article shows results of these analysis done with the Finite Element Method (FEM) in ANSYS. First results show the impact of HCAL design on the ECAL modules motion in static load. The second study dedicated to seismic approach on a larger model (including yoke and cryostat) gives additional results on earthquake consequences.

Dynamic response of the high flux isotope reactor structure caused by nearby heavy load drop

International Nuclear Information System (INIS)

Chang, Shih-Jung.

1995-01-01

A heavy load of 50,000 lb is assumed to drop from 10 ft above the bottom of the High Flux Isotope Reactor (HFIR) pool at the loading station. The consequences of the dynamic impact to the bottom slab of the pool and to the nearby HFIR reactor vessel are analyzed by applying the ABAQUS computer code The results show that both the BM vessel structure and its supporting legs are subjected to elastic disturbances only and, therefore, will not be damaged. The bottom slab of the pool, however, will be damaged to about half of the slab thickness. The velocity response spectrum at the concrete floor next to the HFIR vessel as a result of the vibration caused by the impact is obtained. It is concluded, that the damage caused by heavy load drop at the loading station is controlled by the slab damage and the nearby HFIR vessel and the supporting legs will not be damaged

Dynamic characteristics of motor-gear system under load saltations and voltage transients

Science.gov (United States)

Bai, Wenyu; Qin, Datong; Wang, Yawen; Lim, Teik C.

2018-02-01

In this paper, a dynamic model of a motor-gear system is proposed. The model combines a nonlinear permeance network model (PNM) of a squirrel-cage induction motor and a coupled lateral-torsional dynamic model of a planetary geared rotor system. The external excitations including voltage transients and load saltations, as well as the internal excitations such as spatial effects, magnetic circuits topology and material nonlinearity in the motor, and time-varying mesh stiffness and damping in the planetary gear system are considered in the proposed model. Then, the simulation results are compared with those predicted by the electromechanical model containing a dynamic motor model with constant inductances. The comparison showed that the electromechanical system model with the PNM motor model yields more reasonable results than the electromechanical system model with the lumped-parameter electric machine. It is observed that electromechanical coupling effect can induce additional and severe gear vibrations. In addition, the external conditions, especially the voltage transients, will dramatically affect the dynamic characteristics of the electromechanical system. Finally, some suggestions are offered based on this analysis for improving the performance and reliability of the electromechanical system.

Nonlinear modelling and dynamic stability analysis of a flexible Cartesian robotic manipulator with base disturbance and terminal load

Directory of Open Access Journals (Sweden)

J. Ju

2017-07-01

Full Text Available The flexible Cartesian robotic manipulator (FCRM is coming into widespread application in industry. Because of the feeble rigidity and heavy deflection, the dynamic characteristics of the FCRM are easily influenced by external disturbances which mainly concentrate in the driving end and the load end. Thus, with the influence of driving base disturbance and terminal load considered, the motion differential equations of the FCRM under the plane motion of the base are constructed, which contain the forced and non-linear parametric excitations originated from the disturbances of base lateral and axial motion respectively. Considering the relationship between the coefficients of the motion differential equations and the mode shapes of the flexible manipulator, the analytic expressions of the mode shapes with terminal load are deduced. Then, based on multiple scales method and rectangular coordinate transformation, the average equations of the FCRM are derived to analyze the influence mechanism of base disturbance and terminal load on the system parametric vibration stability. The results show that terminal load mainly affects the node locations of mode shapes and mode frequencies of the FCRM, and the axial motion disturbance of the driving base introduces parametric excitation while the lateral motion disturbance generates forced excitation for the transverse vibration model of the FCRM. Furthermore, with the increase of the base excitation acceleration and terminal load, the parametric vibration instability region of the FCRM increases significantly. This study will be helpful for the dynamic characteristics analysis and vibration control of the FCRM.

Validation of the Dynamic Wake Meander model with focus on tower loads

Science.gov (United States)

Larsen, T. J.; Larsen, G. C.; Pedersen, M. M.; Enevoldsen, K.; Madsen, H. A.

2017-05-01

This paper presents a comparison between measured and simulated tower loads for the Danish offshore wind farm Nysted 2. Previously, only limited full scale experimental data containing tower load measurements have been published, and in many cases the measurements include only a limited range of wind speeds. In general, tower loads in wake conditions are very challenging to predict correctly in simulations. The Nysted project offers an improved insight to this field as six wind turbines located in the Nysted II wind farm have been instrumented to measure tower top and tower bottom moments. All recorded structural data have been organized in a database, which in addition contains relevant wind turbine SCADA data as well as relevant meteorological data - e.g. wind speed and wind direction - from an offshore mast located in the immediate vicinity of the wind farm. The database contains data from a period extending over a time span of more than 3 years. Based on the recorded data basic mechanisms driving the increased loading experienced by wind turbines operating in offshore wind farm conditions have been identified, characterized and modeled. The modeling is based on the Dynamic Wake Meandering (DWM) approach in combination with the state-of-the-art aeroelastic model HAWC2, and has previously as well as in this study shown good agreement with the measurements. The conclusions from the study have several parts. In general the tower bending and yaw loads show a good agreement between measurements and simulations. However, there are situations that are still difficult to match. One is tower loads of single-wake operation near rated ambient wind speed for single wake situations for spacing’s around 7-8D. A specific target of the study was to investigate whether the largest tower fatigue loads are associated with a certain downstream distance. This has been identified in both simulations and measurements, though a rather flat optimum is seen in the measurements.

Moment measurements in dynamic and quasi-static spine segment testing using eccentric compression are susceptible to artifacts based on loading configuration.

Science.gov (United States)

Van Toen, Carolyn; Carter, Jarrod W; Oxland, Thomas R; Cripton, Peter A

2014-12-01

The tolerance of the spine to bending moments, used for evaluation of injury prevention devices, is often determined through eccentric axial compression experiments using segments of the cadaver spine. Preliminary experiments in our laboratory demonstrated that eccentric axial compression resulted in "unexpected" (artifact) moments. The aim of this study was to evaluate the static and dynamic effects of test configuration on bending moments during eccentric axial compression typical in cadaver spine segment testing. Specific objectives were to create dynamic equilibrium equations for the loads measured inferior to the specimen, experimentally verify these equations, and compare moment responses from various test configurations using synthetic (rubber) and human cadaver specimens. The equilibrium equations were verified by performing quasi-static (5 mm/s) and dynamic experiments (0.4 m/s) on a rubber specimen and comparing calculated shear forces and bending moments to those measured using a six-axis load cell. Moment responses were compared for hinge joint, linear slider and hinge joint, and roller joint configurations tested at quasi-static and dynamic rates. Calculated shear force and bending moment curves had similar shapes to those measured. Calculated values in the first local minima differed from those measured by 3% and 15%, respectively, in the dynamic test, and these occurred within 1.5 ms of those measured. In the rubber specimen experiments, for the hinge joint (translation constrained), quasi-static and dynamic posterior eccentric compression resulted in flexion (unexpected) moments. For the slider and hinge joints and the roller joints (translation unconstrained), extension ("expected") moments were measured quasi-statically and initial flexion (unexpected) moments were measured dynamically. In the cadaver experiments with roller joints, anterior and posterior eccentricities resulted in extension moments, which were unexpected and expected, for those

High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

Science.gov (United States)

Shimer, Daniel W.; Lange, Arnold C.

1995-01-01

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

High voltage dc--dc converter with dynamic voltage regulation and decoupling during load-generated arcs

Science.gov (United States)

Shimer, D.W.; Lange, A.C.

1995-05-23

A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 Figs.

Contribution to the dynamic analysis of prestressed and preloaded spring-mass systems of variable structure under shock load

International Nuclear Information System (INIS)

Matthees, W.

1980-01-01

The purpose of this work is the development of a method to analyze on impact load structural systems whose topologically variable system arrangements are dependent on temporarily varying deformation conditions impact loads. This method serves to examine the prototype of a dynamically excited burst protection system for a nuclear power plant. Evidence is given that in case of hypothetical failure of the prestressed reactor pressure vessel the maximum load capacity of the reactor core is not exceeded, which in turn guarantees safe shutdown of the reactor. (orig./HP) [de

Dynamic MR cholangiography after fatty meal loading. Cystic contractility and dynamic evaluation of biliary stasis

International Nuclear Information System (INIS)

Omata, Takayuki; Saito, Kazuhiro; Kotake, Fumio; Mizokami, Yuji; Matsuoka, Takeshi; Abe, Kimihiko

2002-01-01

Dynamic MR cholangiography was conducted on patients with cholelithiasis or choledocholithiasis who had consumed a fatty test meal (Molyork) and the cystic contractility and dynamics of biliary stasis was evaluated. The subjects were 25 with intracystic cholelithiasis, 10 with choledocholithiasis and 10 normal controls. For an imaging sequence, the rapid acquisition with relaxation enhancement (RARE) method was employed and imaging was conducted for 40 min (every 30 s following Molyork administration) without breath-holding. The gallbladder contraction ratio was computed and the contractile ratio for the common bile duct was calculated. To determine the bile flow to the duodenum, the high-intensity signal, indicating the flow from the lower common bile duct, and perfusion of the duodenum were observed in dynamic mode on the monitor with the naked eye and interpreted as positive bile flow. The frequency of this flow was visually monitored. The gallbladder contractile ratio was significantly reduced in patients with cholelithiasis or choledocholithiasis compared with the controls. In a comparison with the normal controls, no sequential changes were noted in the mean contractile ratio of the common bile duct of the patients with cholelithiasis or choledocholithiasis. The mean frequency of bile flow observed for each 40 min period was 13±2.4, 6±2.2, and 4±1.3 times for the controls, those with intracystic cholelithiasis, and those with choledocholithiasis, respectively. Compared with the controls, the latter two patient groups showed evident reductions in the frequency of bile flow to the duodenum (p<0.001). Dynamic MRC combined with Molyork loading makes it possible to compute cystic contractile ratios and perform a dynamic examination of bile flow under non-invasive, near-physiological conditions. (author)

The Coupled Effect of Loading Rate and Grain Size on Tensile Strength of Sandstones under Dynamic Disturbance

Directory of Open Access Journals (Sweden)

Miao Yu

2017-01-01

Full Text Available It is of significance to comprehend the effects of rock microstructure on the tensile strength under different loading rates caused by mining disturbance. So, in this paper, three kinds of sandstones drilled from surrounding rocks in Xiao Jihan Coal to simulate the in situ stress state, whose average grain size is 30 μm (fine grain, FG, 105 μm (medium grain, MG, and 231 μm (Coarse grain, CG, are selected with the calculation of optical microscopic technique and moreover processed to Brazilian disc (BD to study the mechanical response of samples. The dynamic Brazilian tests of samples with three kinds of grain sizes are conducted with the Split Hopkinson Pressure Bar (SHPB driven by pendulum hammer, which can produce four different velocities (V=2.0 m/s, 2.5 m/s, 3.3 m/s, and 4.2 m/s when the incident bar is impacted by pendulum hammer. The incident wave produced by pendulum hammer is a slowly rising stress wave, which allows gradual stress accumulation in the specimen and maintains the load at both ends of the specimen in an equilibrium state. The results show that the dynamic strength of three kinds of BD samples represented loading rates dependence, and FG sandstones are more sensitive for loading rates than MG and CG samples. Moreover, the peak strength is observed to increase linearly with an increasing stress rates, and the relationship between the dynamic BD strength and stress rates can be built through a linear equation. Finally, the failure modes of different grain sizes are discussed and explained by microfailure mechanism.

Instability predictions for circumferentially cracked Type-304 stainless-steel pipes under dynamic loading. Final report

International Nuclear Information System (INIS)

Zahoor, A.; Wilkowski, G.; Abou-Sayed, I.; Marschall, C.; Broek, D.; Sampath, S.; Rhee, H.; Ahmad, J.

1982-04-01

This report provides methods to predict margins of safety for circumferentially cracked Type 304 stainless steel pipes subjected to applied bending loads. An integrated combination of experimentation and analysis research was pursued. Two types of experiments were performed: (1) laboratory-scale tests on center-cracked panels and bend specimens to establish the basic mechanical and fracture properties of Type 304 stainless steel, and (2) full-scale pipe fracture tests under quasi-static and dynamic loadings to assess the analysis procedures. Analyses were based upon the simple plastic collapse criterion, a J-estimation procedure, and elastic-plastic large-deformation finite element models

Dynamic analysis of maritime gasbag-type floating bridge subjected to moving loads

OpenAIRE

Huan-huan Wang; Xian-long Jin

2016-01-01

This paper studied the dynamic response of a new gasbag-type floating bridge under the effect of a moving load. The arbitrary Lagrangian-Eulerian (ALE) method was used to simulate the movement of seawater and air, and the penalty-based method was used to study the coupling between gasbags and fluid. A three-dimensional finite element model of the floating bridge was established, and the numerical model was verified by comparing with the experimental results. In order to prevent resonance, the...

Load bearing and deformation behaviour of dynamically loaded wide plate specimens

International Nuclear Information System (INIS)

Julisch, P.; Haedrich, H.J.; Stadtmueller, W.; Sturm, D.

1989-01-01

For the testing of large-scale specimens, a 12 MN-High Loading Rate Tensile Testing Machine was designed and built at MPA Stuttgart. The aim was to determine the influence of high loading rates on the stress and strain behaviour of unwelded and welded components of ferritic and austenitic materials. This new generation of testing machines is driven by a propellant charge, and generates a maximum tensile force of 12 MN with a piston velocity of 25 m/s after a stroke of 20 mm, or a maximum velocity of 60 m/s after a stroke of 400 mm. In a first test programme, welded and unwelded wide plate specimens made of material X 6 CrNi 18 11 were tested at room temperature with different strain rates from 10 -3 /s to 63/s. In addition to a description of the 12 MN-High Loading Rate Tensile Testing Machine, the results of the high loading rate tensile tests performed will be presented and compared with quasistatically tested wide plate specimens. (orig.)

Special aspects of hemo-dynamic and reaction of erythrocytes in blood to standard physical load of different qualification female volleyball players

Directory of Open Access Journals (Sweden)

S. L. Popel’

2017-10-01

Full Text Available Purpose: to study the aspects of organism’s cardio-hemo-dynamic and blood erythrocytes reaction of female volleyball players to standard physical load. Material: with functional methods we studied cardio-hemo-dynamic and with the help of scanning electronic microscopy - erythrocytes’ structure in 18 female volleyball players of different qualification (age - 22.0±0.60 years. Results: it was found that maximal physical load causes substantial changes in cardio-hemo-dynamic, which depend on female volleyball players’ qualification. These changes have intrinsic to them type of blood circulation system reacting, which is manifested in the following: appropriate changes of some indicators; natural changes of periphery blood erythrocytes. In the article possible mechanisms of realization of female volleyball players’ organism’s typological features, depending on blood circulation type and erythrocytes’ conformation, are discussed. Conclusions: In relaxed state all female volleyball players have non-uniform cardio-hemo-dynamic of blood circulation. With hyper-dynamic blood circulation type, higher indicators of strike and minute blood volume were observed. With hypo-kinetic blood circulation type the opposite picture was observed: indicators of strike and minute blood volume, heart index, load on cardio-vascular system in different periods of day were low.

Pre-study of dynamic loads on the internals caused by a large pipe break in a BWR; Foerstudie av stroemningsinducerade laster paa interndelar vid brott i huvudcirkulationskretsarna i BWR

Energy Technology Data Exchange (ETDEWEB)

Marcinkiewicz, Jerzy; Lindgren, Anders [Det Norske Veritas Nuclear Technology AB, Stockholm (Sweden)

2002-12-01

Det Norske Veritas Nuclear Technology has performed a literature study of dynamic load on a BWR (Boiling Water Reactor) internals caused by a large pipe break. The goal of the study was to improve the knowledge about the physics of phenomena occurring in the RPV (Reactor Pressure Vessel) after pipe break in the main circulation system and also to make a review of calculation methods, models and computer programs including their capabilities when calculating the dynamic loads. The report presents description of relevant parts of a BWR, initial and boundary conditions, and phenomena determining the loads - rapid depressurization and propagation of pressure wave (including none-equilibrium). Furthermore, the report generally describes possible methodologies for calculating the dynamic loads on internals after the pipe break and the experiences from calculations the dynamic loads with different methods (computer programs) including comparisons with experimental data. Fluid-Structure Interaction methodology and its importance for calculation of dynamic loads on reactor internals is discussed based on experimental data. A very intensive research program for studying and calculating the dynamic loads on internals after pipe breaks has been performed in USA and Germany during the seventies and the eighties. Several computer programs have been developed and a number of large-scale experiments have been performed to calibrate the calculation methods. In spite of the fact that all experiments were performed for PWR several experiences should be valid also for BWR. These experiences, connected mainly to capabilities of computer programs calculating dynamic loads, are discussed in the report.

Seismicity as dynamic load of pipes and fittings

International Nuclear Information System (INIS)

Rejent, B.

1984-01-01

The load is discussed of pipe systems and fittings for nuclear power plants which may result from earthquakes, etc. Modifications of the equation of motion are discussed which may be solved using the response spectrum method or the method of direct numerical integration. A mathematical description of both methods is given. The seismic resistance of fittings, pumps, etc., is experimentally determined by loking for their eigenfrequencies and monitoring the response of equipment to resonance oscillations. The principle is described of uniaxial hydraulic and mechanical shock absorbers and a viscous damper. The presented computation method was used for evaluating the primary circuit (Sigma Modrany) and rods for the remote control of fittings (Sigma Hodonin) supplied for the Mochovce nuclear power plant. Variants were compared of seismic protection of the primary circuit by hydraulic and mechanical shock absorbers with viscous dampers and of circuits without any protection. The unprotected system oscillates in the first harmonic, the system with shock absorbers keeps the deflections within the range of the shock absorber function (to 2 mm), and the system using viscous dampers oscillates approximately according to the first waveform with a deflection of around 11 mm. A diagram and a dynamic model are presented of a rod for the remote control of fittings. Figure shows the computation model and the response of this rod in individual time moments, both affected and not affected by play in the dilatation joint. Table shows the effect of play in the dilatation joint on deformation maxima and on rod bend stress from a symmetric load of 8g. (E.S.)

Dynamics of Inhomogeneous Shell Systems Under Non-Stationary Loading (Survey)

Science.gov (United States)

Lugovoi, P. Z.; Meish, V. F.

2017-09-01

Experimental works on the determination of dynamics of smooth and stiffened cylindrical shells contacting with a soil medium under various non-stationary loading are reviewed. The results of studying three-layer shells of revolution whose motion equations are obtained within the framework of the hypotheses of the Timoshenko geometrically nonlinear theory are stated. The numerical results for shells with a piecewise or discrete filler enable the analysis of estimation of the influence of geometrical and physical-mechanical parameters of structures on their dynamics and reveal new mechanical effects. Basing on the classical theory of shells and rods, the effect of the discrete arrangement of ribs and coefficients of the Winkler or Pasternak elastic foundation on the normal frequencies and modes of rectangular planar cylindrical and spherical shells is studied. The number and shape of dispersion curves for longitudinal harmonic waves in a stiffened cylindrical shell are determined. The equations of vibrations of ribbed shells of revolution on Winkler or Pasternak elastic foundation are obtained using the geometrically nonlinear theory and the Timoshenko hypotheses. On applying the integral-interpolational method, numerical algorithms are developed and the corresponding non-stationary problems are solved. The special attention is paid to the statement and solution of coupled problems on the dynamical interaction of cylindrical or spherical shells with the soil water-saturated medium of different structure.

Research of Charging(Discharging Orderly and Optimizing Load Curve for Electric Vehicles Based on Dynamic Electric Price and V2G

Directory of Open Access Journals (Sweden)

Yang Shuai

2016-01-01

Full Text Available Firstly, using the Monte Carlo method and simulation analysis, this paper builds models for the behaviour of electric vehicles, the conventional charging model and the fast charging model. Secondly, this paper studies the impact that the number of electric vehicles which get access to power grid has on the daily load curve. Then, the paper put forwards a dynamic pricing mechanism of electricity, and studies how this dynamic pricing mechanism guides the electric vehicles to charge orderly. Last but not the least, the paper presents a V2G mechanism. Under this mechanism, electric vehicles can charge orderly and take part in the peak shaving. Research finds that massive electric vehicles’ access to the power grid will increase the peak-valley difference of daily load curve. Dynamic pricing mechanism and V2G mechanism can effectively lead the electric vehicles to take part in peak-shaving, and optimize the daily load curve.

Study of the dynamic fragmentation of laser shock-loaded metallic target

International Nuclear Information System (INIS)

Lescoute, E.

2010-01-01

The irradiation of a metallic target by a high power laser pulse induces a shock wave in the material. Under some conditions, it leads to the production of high velocity ejecta which can damage the optical environment (lenses, mirrors, windows, etc.). With the ongoing development of high energy laser facilities designed to achieve inertial confinement fusion, such as the Laser MegaJoule in France or the National Ignition Facility in the USA, the question of debris ejection from metallic samples subjected to intense laser irradiation has become a key issue. It is necessary to understand fragmentation processes induced by laser shock, and to anticipate and quantify generated fragments, in order to design suitable protections and experiments, and to preserve laser facilities. The main fragmentation processes which can occur in a laser-shock-loaded metallic target and generate high velocity ejecta are: (i) micro-jetting, which occurs upon reflection of the incident compressive front from the free surface, (ii) spallation, which is due to the later interaction of the release wave reflected from that surface with the incident unloading wave and (iii) dynamic punching of thin targets. Experimental campaigns have been performed on high energy laser facilities in the Centre d'Etudes Scientifiques et Techniques d'Aquitaine (CESTA, CEA, Alise facility) and in the Laboratoire pour l'Utilisation des Lasers Intenses (LULI, Ecole Polytechnique, LULI 2000 facility). Gold and aluminium have been mainly studied because they are the two main metallic components of the target which will be used to achieved the inertial confinement fusion. Specific diagnostics have been developed and used during these experiments to study the dynamic fragmentation: transverse shadowgraphy, free surface velocity measurement and recovery of generated fragments. Experimental results have been compared with numerical predictions obtained with a bi-dimensional hydrodynamic code, where a specific numerical

Study on Dynamic Response of Downhole Tools under Perforation Impact Load

Directory of Open Access Journals (Sweden)

Liu Jun

2017-01-01

Full Text Available A model of a multibody system is established to investigate the dynamic response of an oil tube-shock absorber-perforating gun system in downhole perforation-test joint operation. In the model, the oil tube and perforating gun are modeled as elastic rods and the shock absorber is modeled as single particle system with damping and a spring. Two force continuity conditions are used to simulate the interactions among the three components. The perforation impact load is determined by an experiment of underwater explosion of perforating bullets. Using the model, the effects of charge quantity of perforating bullet, the number of shock absorbers, and the length of oil tube on the dynamic response of oil tube and packer are investigated. On this basis, a basic principle of the combination design of shock absorber and oil tube is proposed to improve the mechanical state of downhole tools. The study results can provide theoretical support for the design of downhole perforation-test joint operation.

Comparison of the dynamic response of the structures of a typical DWR-reactor-building to the load cases earthquake, aircraft impact and explosion

International Nuclear Information System (INIS)

Schrader, K.-H.; Kaiser, A.; Krutzik, N.

1978-01-01

For the design of equipment and components of nuclear power plants with respect to their dynamic behavior it is necessary to know the dynamic load due to shock, or vibrating excitations, which might arise during the life time of the plant. In Germany these load cases are those listed in the heading. The objective of the paper is to compare the characteristics of the responses of the structure, which then have to serve as dynamic loads for the equipment. The paper deals with the following subjects:-survey and introduction of the code in Germany -conclusions concerning the mathematical model and the mechanical system for the computation of the dynamic response-comparison of the results which includes eigensystems, an overall picture of max/min values for displacements, as well as times histories and response spectra for critical points of the structure. For the F.E. Model, composed structures of ring elements and the method of the modal analysis have been used. (Author)

Estimation of structural reliability under combined loads

International Nuclear Information System (INIS)

Shinozuka, M.; Kako, T.; Hwang, H.; Brown, P.; Reich, M.

1983-01-01

For the overall safety evaluation of seismic category I structures subjected to various load combinations, a quantitative measure of the structural reliability in terms of a limit state probability can be conveniently used. For this purpose, the reliability analysis method for dynamic loads, which has recently been developed by the authors, was combined with the existing standard reliability analysis procedure for static and quasi-static loads. The significant parameters that enter into the analysis are: the rate at which each load (dead load, accidental internal pressure, earthquake, etc.) will occur, its duration and intensity. All these parameters are basically random variables for most of the loads to be considered. For dynamic loads, the overall intensity is usually characterized not only by their dynamic components but also by their static components. The structure considered in the present paper is a reinforced concrete containment structure subjected to various static and dynamic loads such as dead loads, accidental pressure, earthquake acceleration, etc. Computations are performed to evaluate the limit state probabilities under each load combination separately and also under all possible combinations of such loads. Indeed, depending on the limit state condition to be specified, these limit state probabilities can indicate which particular load combination provides the dominant contribution to the overall limit state probability. On the other hand, some of the load combinations contribute very little to the overall limit state probability. These observations provide insight into the complex problem of which load combinations must be considered for design, for which limit states and at what level of limit state probabilities. (orig.)

Dynamic QoS management in Differentiated Services using bandwidth brokers, RSVP aggregation and load control protocols

NARCIS (Netherlands)

Westberg, Lars; Eriksson, Anders; Karagiannis, Georgios; Heijenk, Geert; Rexhepi, Vlora; Partain, David

2001-01-01

A method and network subsystem for providing on demand end to end Quality of Service (Qos) in a dynamic manner, use a combination of Resource Reservation Protocol (RSVP), load control protocol (and its successors) and Bandwidth Brokers (BBs)(1106) which communicate using a predetermined protocol.

Dynamic QoS management in Differentiated Services using bandwidth brokers, RSVP aggregation and load control protocols

NARCIS (Netherlands)

Westberg, Lars; Eriksson, Anders; Karagiannis, Georgios; Heijenk, Geert; Rexhepi, Vlora; Partain, David

2009-01-01

A method and network subsystem for providing on demand end to end Quality of Service (Qos) in a dynamic manner, use a combination of Resource Reservation Protocol (RSVP), load control protocol (and its successors) and Bandwidth Brokers (BBs)(1106) which communicate using a predetermined protocol.

Revival of pure titanium for dynamically loaded porous implants using additive manufacturing.

Science.gov (United States)

Wauthle, Ruben; Ahmadi, Seyed Mohammad; Amin Yavari, Saber; Mulier, Michiel; Zadpoor, Amir Abbas; Weinans, Harrie; Van Humbeeck, Jan; Kruth, Jean-Pierre; Schrooten, Jan

2015-09-01

Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous implants, and none or little interest goes to pure titanium for use in orthopedic or load-bearing implants. Given the special mechanical behavior of cellular structures and the material properties inherent to the additive manufacturing of metals, the aim of this study is to investigate the properties of selective laser melted pure unalloyed titanium porous structures. Therefore, the static and dynamic compressive properties of pure titanium structures are determined and compared to previously reported results for identical structures made from Ti6Al4V ELI and tantalum. The results show that porous Ti6Al4V ELI still remains the strongest material for statically loaded applications, whereas pure titanium has a mechanical behavior similar to tantalum and is the material of choice for cyclically loaded porous implants. These findings are considered to be important for future implant developments since it announces a potential revival of the use of pure titanium for additively manufactured porous implants. Copyright © 2015 Elsevier B.V. All rights reserved.

Revival of pure titanium for dynamically loaded porous implants using additive manufacturing

International Nuclear Information System (INIS)

Wauthle, Ruben; Ahmadi, Seyed Mohammad; Amin Yavari, Saber; Mulier, Michiel; Zadpoor, Amir Abbas; Weinans, Harrie; Van Humbeeck, Jan; Kruth, Jean-Pierre; Schrooten, Jan

2015-01-01

Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous implants, and none or little interest goes to pure titanium for use in orthopedic or load-bearing implants. Given the special mechanical behavior of cellular structures and the material properties inherent to the additive manufacturing of metals, the aim of this study is to investigate the properties of selective laser melted pure unalloyed titanium porous structures. Therefore, the static and dynamic compressive properties of pure titanium structures are determined and compared to previously reported results for identical structures made from Ti6Al4V ELI and tantalum. The results show that porous Ti6Al4V ELI still remains the strongest material for statically loaded applications, whereas pure titanium has a mechanical behavior similar to tantalum and is the material of choice for cyclically loaded porous implants. These findings are considered to be important for future implant developments since it announces a potential revival of the use of pure titanium for additively manufactured porous implants. - Highlights: • The mechanical properties of CP Ti grade 1 porous structures are studied. • The results are compared with identical structures in Ti6Al4V ELI and tantalum. • Ti6Al4V ELI structures are about two times stronger under a static compressive load. • CP Ti structures deform continuously without fracture while loaded statically. • CP Ti structures have a higher fatigue life compared to Ti6Al4V ELI structures

Revival of pure titanium for dynamically loaded porous implants using additive manufacturing

Energy Technology Data Exchange (ETDEWEB)

Wauthle, Ruben, E-mail: ruben.wauthle@3dsystems.com [KU Leuven, Department of Mechanical Engineering, Section Production Engineering, Machine Design and Automation (PMA), Celestijnenlaan 300B, 3001 Leuven (Belgium); 3D Systems - LayerWise NV, Grauwmeer 14, 3001 Leuven (Belgium); Ahmadi, Seyed Mohammad; Amin Yavari, Saber [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft (Netherlands); Mulier, Michiel [KU Leuven, Department of Orthopaedics, Weligerveld 1, 3212 Pellenberg (Belgium); Zadpoor, Amir Abbas [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft (Netherlands); Weinans, Harrie [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft (Netherlands); Department of Orthopedics & department of Rheumatology, UMC Utrecht, Heidelberglaan 100, 3584 CX, Utrecht (Netherlands); Van Humbeeck, Jan [KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, PB 2450, 3001 Leuven (Belgium); Kruth, Jean-Pierre [KU Leuven, Department of Mechanical Engineering, Section Production Engineering, Machine Design and Automation (PMA), Celestijnenlaan 300B, 3001 Leuven (Belgium); Schrooten, Jan [KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, PB 2450, 3001 Leuven (Belgium); KU Leuven, Prometheus, Division of Skeletal Tissue Engineering, PB 813, O& N1, Herestraat 49, 3000 Leuven (Belgium)

2015-09-01

Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous implants, and none or little interest goes to pure titanium for use in orthopedic or load-bearing implants. Given the special mechanical behavior of cellular structures and the material properties inherent to the additive manufacturing of metals, the aim of this study is to investigate the properties of selective laser melted pure unalloyed titanium porous structures. Therefore, the static and dynamic compressive properties of pure titanium structures are determined and compared to previously reported results for identical structures made from Ti6Al4V ELI and tantalum. The results show that porous Ti6Al4V ELI still remains the strongest material for statically loaded applications, whereas pure titanium has a mechanical behavior similar to tantalum and is the material of choice for cyclically loaded porous implants. These findings are considered to be important for future implant developments since it announces a potential revival of the use of pure titanium for additively manufactured porous implants. - Highlights: • The mechanical properties of CP Ti grade 1 porous structures are studied. • The results are compared with identical structures in Ti6Al4V ELI and tantalum. • Ti6Al4V ELI structures are about two times stronger under a static compressive load. • CP Ti structures deform continuously without fracture while loaded statically. • CP Ti structures have a higher fatigue life compared to Ti6Al4V ELI structures.

Are daily and weekly load and spot price dynamics in Australia's National Electricity Market governed by episodic nonlinearity?

International Nuclear Information System (INIS)

Wild, Phillip; Hinich, Melvin J.; Foster, John

2010-01-01

In this article, we use half hourly spot electricity prices and load data for the National Electricity Market (NEM) of Australia for the period from December 1998 to June 2009 to test for episodic nonlinearity in the dynamics governing daily and weekly cycles in load and spot price time series data. We apply the portmanteau correlation, bicorrelation and tricorrelation tests introduced in Hinich (1996) to the time series of half hourly spot prices and load demand from 7/12/1998 to 30/06/2009 using a FORTRAN 95 program. We find the presence of significant third and fourth-order (nonlinear) serial dependence in the weekly load and spot price data in particular, but to a much more marginal extent, in the daily data. (author)

The effect of external dynamic loads on the lifetime of rolling element bearings: accurate measurement of the bearing behaviour

International Nuclear Information System (INIS)

Jacobs, W; Boonen, R; Sas, P; Moens, D

2012-01-01

Accurate prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. Recent research emphasizes an important influence of external dynamic loads on the lifetime of bearings. However, most lifetime calculations of bearings are based on the classical ISO 281 standard, neglecting this influence. For bearings subjected to highly varying loads, this leads to inaccurate estimations of the lifetime, and therefore excessive safety factors during the design and unexpected failures during operation. This paper presents a novel test rig, developed to analyse the behaviour of rolling element bearings subjected to highly varying loads. Since bearings are very precise machine components, their motion can only be measured in an accurately controlled environment. Otherwise, noise from other components and external influences such as temperature variations will dominate the measurements. The test rig is optimised to perform accurate measurements of the bearing behaviour. Also, the test bearing is fitted in a modular structure, which guarantees precise mounting and allows testing different types and sizes of bearings. Finally, a fully controlled multi-axial static and dynamic load is imposed on the bearing, while its behaviour is monitored with capacitive proximity probes.

Numerical investigations of rib fracture failure models in different dynamic loading conditions.

Science.gov (United States)

Wang, Fang; Yang, Jikuang; Miller, Karol; Li, Guibing; Joldes, Grand R; Doyle, Barry; Wittek, Adam

2016-01-01

Rib fracture is one of the most common thoracic injuries in vehicle traffic accidents that can result in fatalities associated with seriously injured internal organs. A failure model is critical when modelling rib fracture to predict such injuries. Different rib failure models have been proposed in prediction of thorax injuries. However, the biofidelity of the fracture failure models when varying the loading conditions and the effects of a rib fracture failure model on prediction of thoracic injuries have been studied only to a limited extent. Therefore, this study aimed to investigate the effects of three rib failure models on prediction of thoracic injuries using a previously validated finite element model of the human thorax. The performance and biofidelity of each rib failure model were first evaluated by modelling rib responses to different loading conditions in two experimental configurations: (1) the three-point bending on the specimen taken from rib and (2) the anterior-posterior dynamic loading to an entire bony part of the rib. Furthermore, the simulation of the rib failure behaviour in the frontal impact to an entire thorax was conducted at varying velocities and the effects of the failure models were analysed with respect to the severity of rib cage damages. Simulation results demonstrated that the responses of the thorax model are similar to the general trends of the rib fracture responses reported in the experimental literature. However, they also indicated that the accuracy of the rib fracture prediction using a given failure model varies for different loading conditions.

Dynamic backcalculation with different load-time histories

DEFF Research Database (Denmark)

Madsen, Stine Skov; Levenberg, Eyal

2017-01-01

This paper focused attention to the falling weight deflectometer (FWD) load-time history. For a commonly used device, it studied the pulse generation mechanism and the influence of different load histories on backcalculation results. In this connection, a semi-analytic impact theory was first...... for an experimental dataset that resulted from operating an FWD with different loading configurations. It was found that backcalculated parameters are sensitive to the FWD pulse features. Consequently, it is recommended that, whenever advanced pavement characterisation is sought, experimental attention should...

Dynamic load testing on the bearing capacity of prestressed tubular concrete piles in soft ground

Science.gov (United States)

Yu, Chuang; Liu, Songyu

2008-11-01

Dynamic load testing (DLT) is a high strain test method for assessing pile performance. The shaft capacity of a driven PTC (prestressed tubular concrete) pile in marine soft ground will vary with time after installation. The DLT method has been successfully transferred to the testing of prestressed pipe piles in marine soft clay of Lianyungang area in China. DLT is investigated to determine the ultimate bearing capacity of single pile at different period after pile installation. The ultimate bearing capacity of single pile was founded to increase more than 70% during the inventing 3 months, which demonstrate the time effect of rigid pile bearing capacity in marine soft ground. Furthermore, the skin friction and axial force along the pile shaft are presented as well, which present the load transfer mechanism of pipe pile in soft clay. It shows the economy and efficiency of DLT method compared to static load testing method.

Analytical and experimental investigation of the elastic and plastic behavior of plates on foundations subjected to dynamic punch loading

International Nuclear Information System (INIS)

Duffey, T.A.; Sutherland, S.H.; Cheresh, M.

1980-01-01

Analytical solutions and experimental results are presented for the response of foundation-backed plates to static and dynamic punch loading. Tests were performed on polyurethane foam-backed and unbacked plates; plates were centrally loaded over a range-in plastic deformations up to complete failure. This is part of an attempt to understand the puncture resistance of the sidewalls of containers used to ship hazardous wastes

Aeroelastic Ground Wind Loads Analysis Tool for Launch Vehicles

Science.gov (United States)

Ivanco, Thomas G.

2016-01-01

Launch vehicles are exposed to ground winds during rollout and on the launch pad that can induce static and dynamic loads. Of particular concern are the dynamic loads caused by vortex shedding from nearly-cylindrical structures. When the frequency of vortex shedding nears that of a lowly-damped structural mode, the dynamic loads can be more than an order of magnitude greater than mean drag loads. Accurately predicting vehicle response to vortex shedding during the design and analysis cycles is difficult and typically exceeds the practical capabilities of modern computational fluid dynamics codes. Therefore, mitigating the ground wind loads risk typically requires wind-tunnel tests of dynamically-scaled models that are time consuming and expensive to conduct. In recent years, NASA has developed a ground wind loads analysis tool for launch vehicles to fill this analytical capability gap in order to provide predictions for prelaunch static and dynamic loads. This paper includes a background of the ground wind loads problem and the current state-of-the-art. It then discusses the history and significance of the analysis tool and the methodology used to develop it. Finally, results of the analysis tool are compared to wind-tunnel and full-scale data of various geometries and Reynolds numbers.

Dynamic adjustments in prefrontal, hippocampal, and inferior temporal interactions with increasing visual working memory load.

Science.gov (United States)

Rissman, Jesse; Gazzaley, Adam; D'Esposito, Mark

2008-07-01

The maintenance of visual stimuli across a delay interval in working memory tasks is thought to involve reverberant neural communication between the prefrontal cortex and posterior visual association areas. Recent studies suggest that the hippocampus might also contribute to this retention process, presumably via reciprocal interactions with visual regions. To characterize the nature of these interactions, we performed functional connectivity analysis on an event-related functional magnetic resonance imaging data set in which participants performed a delayed face recognition task. As the number of faces that participants were required to remember was parametrically increased, the right inferior frontal gyrus (IFG) showed a linearly decreasing degree of functional connectivity with the fusiform face area (FFA) during the delay period. In contrast, the hippocampus linearly increased its delay period connectivity with both the FFA and the IFG as the mnemonic load increased. Moreover, the degree to which participants' FFA showed a load-dependent increase in its connectivity with the hippocampus predicted the degree to which its connectivity with the IFG decreased with load. Thus, these neural circuits may dynamically trade off to accommodate the particular mnemonic demands of the task, with IFG-FFA interactions mediating maintenance at lower loads and hippocampal interactions supporting retention at higher loads.

Instability predictions for circumferentially cracked Type-304 stainless-steel pipes under dynamic loading. Final report. [BWR

Energy Technology Data Exchange (ETDEWEB)

Zahoor, A.; Wilkowski, G.; Abou-Sayed, I.; Marschall, C.; Broek, D.; Sampath, S.; Rhee, H.; Ahmad, J.

1982-04-01

This report provides methods to predict margins of safety for circumferentially cracked Type 304 stainless steel pipes subjected to applied bending loads. An integrated combination of experimentation and analysis research was pursued. Two types of experiments were performed: (1) laboratory-scale tests on center-cracked panels and bend specimens to establish the basic mechanical and fracture properties of Type 304 stainless steel, and (2) full-scale pipe fracture tests under quasi-static and dynamic loadings to assess the analysis procedures. Analyses were based upon the simple plastic collapse criterion, a J-estimation procedure, and elastic-plastic large-deformation finite element models.

DECREASING OF MECHANISMS DYNAMIC LOADING AT THE TRANSIENT STATE

Directory of Open Access Journals (Sweden)

V. S. Loveikin

2015-11-01

Full Text Available Purpose. It is necessary to select modes of motion to reduce the dynamic loads in the mechanisms. This choice should be made on optimization basis. The purpose of research is to study methods of synthesis regimes of mechanisms and machines motion that provide optimal modes of movement for terminal and integral criteria. Methodology. For research the one-mass dynamic model of the mechanism has been used. As optimization criteria the terminal and comprehensive integral criteria were used. The stated optimization problem has been solved using dynamic programming and variational calculation. The direct variation method, which allowed finding only approximate solution of the original problem of optimal control, has been used as well. Findings. The ways of ensuring the absolute minimum of terminal criterion have been set for each method of problem solving. The stated characteristics show softness changes of kinematic functions during braking of mechanism. They point to the absolute minimum of adopted terminal criterion in the calculation. Originality. It is necessary to introduce new variables in the system equations during the solving of optimal control problems using dynamic programming to achieve an absolute minimum of terminal criteria. In general, to achieve a minimum of n-order terminal criterion an optimization problem should find relatively (n+1-th order function. When optimization problems is solving by variational calculation in order to ensure a minimization of n-th order terminal criterion by selecting the appropriate boundary conditions, it is necessary to solve the Euler-Poisson 2(n+1-th order equation (subject to symmetric setting boundary conditions. It is a necessary condition for an extremum of the functional with the (n+1-th order integrant. Practical value. Minimizing of adopted terminal criterion in the calculation allows eliminate the brunt in kinematic gearing of mechanisms, which increases their operational life. In addition

Experimental Investigation into Corrosion Effect on Mechanical Properties of High Strength Steel Bars under Dynamic Loadings

Directory of Open Access Journals (Sweden)

Hui Chen

2018-01-01

Full Text Available The tensile behaviors of corroded steel bars are important in the capacity evaluation of corroded reinforced concrete structures. The present paper studies the mechanical behavior of the corroded high strength reinforcing steel bars under static and dynamic loading. High strength reinforcing steel bars were corroded by using accelerated corrosion methods and the tensile tests were carried out under different strain rates. The results showed that the mechanical properties of corroded high strength steel bars were strain rate dependent, and the strain rate effect decreased with the increase of corrosion degree. The decreased nominal yield and ultimate strengths were mainly caused by the reduction of cross-sectional areas, and the decreased ultimate deformation and the shortened yield plateau resulted from the intensified stress concentration at the nonuniform reduction. Based on the test results, reduction factors were proposed to relate the tensile behaviors with the corrosion degree and strain rate for corroded bars. A modified Johnson-Cook strength model of corroded high strength steel bars under dynamic loading was proposed by taking into account the influence of corrosion degree. Comparison between the model and test results showed that proposed model properly describes the dynamic response of the corroded high strength rebars.

Pesticide load dynamics during stormwater flow events in Mediterranean coastal streams: Alexander stream case study.

Science.gov (United States)

Topaz, Tom; Egozi, Roey; Eshel, Gil; Chefetz, Benny

2018-06-01

Cultivated land is a major source of pesticides, which are transported with the runoff water and eroded soil during rainfall events and pollute riverine and estuarine environments. Common ecotoxicological assessments of riverine systems are mainly based on water sampling and analysis of only the dissolved phase, and address a single pesticide's toxicological impact under laboratory conditions. A clear overview of mixtures of pesticides in the adsorbed and dissolved phases is missing, and therefore the full ecotoxicological impact is not fully addressed. The aim of this study was to characterize and quantify pesticide concentrations in both suspended sediment and dissolved phases, to provide a better understanding of pesticide-load dynamics during storm events in coastal streams in a Mediterranean climate. High-resolution sampling campaigns of seven flood events were conducted during two rainy seasons in Alexander stream, Israel. Samples of suspended sediments were separated from the solution and both media were analyzed separately for 250 pesticides. A total of 63 pesticides were detected; 18 and 16 pesticides were found solely in the suspended sediments and solution, respectively. Significant differences were observed among the pesticide groups: only 7% of herbicide, 20% of fungicide and 42% of insecticide load was transported with the suspended sediments. However, in both dissolved and adsorbed phases, a mix of pesticides was found which were graded from "mobile" to "non-mobile" with varied distribution coefficients. Diuron, and tebuconazole were frequently found in large quantities in both phases. Whereas insecticide and fungicide transport is likely governed by application time and method, the governing factor for herbicide load was the magnitude of the stream discharge. The results show a complex dynamic of pesticide load affected by excessive use of pesticides, which should be taken into consideration when designing projects to monitor riverine and estuarine

Dynamic Responses of Continuous Girder Bridges with Uniform Cross-Section under Moving Vehicular Loads

Directory of Open Access Journals (Sweden)

Qingfei Gao

2015-01-01

Full Text Available To address the drawback of traditional method of investigating dynamic responses of the continuous girder bridge with uniform cross-section under moving vehicular loads, the orthogonal experimental design method is proposed in this paper. Firstly, some empirical formulas of natural frequencies are obtained by theoretical derivation and numerical simulation. The effects of different parameters on dynamic responses of the vehicle-bridge coupled vibration system are discussed using our own program. Finally, the orthogonal experimental design method is proposed for the dynamic responses analysis. The results show that the effects of factors on dynamic responses are dependent on both the selected position and the type of the responses. In addition, the interaction effects between different factors cannot be ignored. To efficiently reduce experimental runs, the conventional orthogonal design is divided into two phases. It has been proved that the proposed method of the orthogonal experimental design greatly reduces calculation cost, and it is efficient and rational enough to study multifactor problems. Furthermore, it provides a good way to obtain more rational empirical formulas of the DLA and other dynamic responses, which may be adopted in the codes of design and evaluation.

Planar dynamics of large-deformation rods under moving loads

Science.gov (United States)

Zhao, X. W.; van der Heijden, G. H. M.

2018-01-01

We formulate the problem of a slender structure (a rod) undergoing large deformation under the action of a moving mass or load motivated by inspection robots crawling along bridge cables or high-voltage power lines. The rod is described by means of geometrically exact Cosserat theory which allows for arbitrary planar flexural, extensional and shear deformations. The equations of motion are discretised using the generalised-α method. The formulation is shown to handle the discontinuities of the problem well. Application of the method to a cable and an arch problem reveals interesting nonlinear phenomena. For the cable problem we find that large deformations have a resonance detuning effect on cable dynamics. The problem also offers a compelling illustration of the Timoshenko paradox. For the arch problem we find a stabilising (delay) effect on the in-plane collapse of the arch, with failure suppressed entirely at sufficiently high speed.

Cooperation of axisymmetric connection elements under dynamic load

Directory of Open Access Journals (Sweden)

Kołodziej Andrzej

2018-01-01

Full Text Available The article presents a method for determining the parameters that define the cooperation of the elements in the axisymmetic connection. The connection, which constitutes a shaft cooperating with a sleeve, has been tested for reaction forces in the connection during shaft rotation in the static sleeve. The shaft was characterized by deliberately modelled roundness deviations in the form of ovality, triangularity and quadrangularity. In addition, the research programme has taken into account the determination of the impact of tolerance of the outside diameter of the shaft. Determination of reaction forces has been carried out using the FEM software. The shaft has been modelled as a rigid element that rotates with a given rotational speed in the deformable sleeve. The conclusions present the impact of roundness deviation types and the tolerance value on reaction forces in the connection restraint. The method presented in the article can be used to predict the behaviour of the elements of axisymmetic connections under dynamic load, which can contribute to forecasting the durability of the connection.

Dynamic strength behavior of a Zr-based bulk metallic glass under shock loading

International Nuclear Information System (INIS)

Yu Yu-Ying; Xi Feng; Dai Cheng-Da; Cai Ling-Cang; Tan Ye; Li Xue-Mei; Wu Qiang; Tan Hua

2015-01-01

Dynamic strength behavior of Zr 51 Ti 5 Ni 10 Cu 25 Al 9 bulk metallic glass (BMG) up to 66 GPa was investigated in a series of plate impact shock-release and shock-reload experiments. Particle velocity profiles measured at the sample/LiF window interface were used to estimate the shear stress, shear modulus, and yield stress in shocked BMG. Beyond confirming the previously reported strain-softening of shear stress during the shock loading process for BMGs, it is also shown that the softened Zr-BMG still has a high shear modulus and can support large yield stress when released or reloaded from the shocked state, and both the shear modulus and the yield stress appear as strain-hardening behaviors. The work provides a much clearer picture of the strength behavior of BMGs under shock loading, which is useful to comprehensively understand the plastic deformation mechanisms of BMGs. (paper)

Dynamics of HPV viral loads reflect the treatment effect of photodynamic therapy in genital warts.

Science.gov (United States)

Hu, Zhili; Liu, Lishi; Zhang, Wenjing; Liu, Hui; Li, Junpeng; Jiang, Lifen; Zeng, Kang

2018-03-01

Photodynamic therapy (PDT) has demonstrated good clinical cure rates and low recurrence rates in the treatment of genital warts. Human papillomavirus (HPV) genotypes and viral load assays can reflect the status of persistent or latent infection and serve as a predictor of infection clearance. Specimens from 41 patients with HPV infection were obtained, and the HPV genotypes and viral load were analyzed using real-time polymerase chain reaction (PCR) assays. Traditional treatment, such as radiofrequency, microwave, or surgical therapy, was used to remove the visible lesions, and then PDT treatment was performed every week. HPV DNA testing was performed at every patient visit and the frequency of PDT treatment was determined by changes in HPV viral loads. HPV viral loads decreased significantly after PDT treatment. There were significant differences in HPV viral loads between pretherapy and three or six rounds of PDT treatment. Significant differences were also observed between single and multiple type HPV infection after six rounds of PDT treatment. Patients with single type HPV infection had significantly higher rates of negative HPV DNA test results, as compared with patients with multiple infections after six rounds of PDT treatment; however, there was no difference in recurrence rates between the two groups. Dynamic monitoring of HPV genotypes and viral loads can be used to guide PDT treatment and indicate PDT treatment efficacy in eliminating HPV. Copyright © 2017 Elsevier B.V. All rights reserved.

Rib fractures under anterior-posterior dynamic loads: experimental and finite-element study.

Science.gov (United States)

Li, Zuoping; Kindig, Matthew W; Kerrigan, Jason R; Untaroiu, Costin D; Subit, Damien; Crandall, Jeff R; Kent, Richard W

2010-01-19

The purpose of this study was to investigate whether using a finite-element (FE) mesh composed entirely of hexahedral elements to model cortical and trabecular bone (all-hex model) would provide more accurate simulations than those with variable thickness shell elements for cortical bone and hexahedral elements for trabecular bone (hex-shell model) in the modeling human ribs. First, quasi-static non-injurious and dynamic injurious experiments were performed using the second, fourth, and tenth human thoracic ribs to record the structural behavior and fracture tolerance of individual ribs under anterior-posterior bending loads. Then, all-hex and hex-shell FE models for the three ribs were developed using an octree-based and multi-block hex meshing approach, respectively. Material properties of cortical bone were optimized using dynamic experimental data and the hex-shell model of the fourth rib and trabecular bone properties were taken from the literature. Overall, the reaction force-displacement relationship predicted by both all-hex and hex-shell models with nodes in the offset middle-cortical surfaces compared well with those measured experimentally for all the three ribs. With the exception of fracture locations, the predictions from all-hex and offset hex-shell models of the second and fourth ribs agreed better with experimental data than those from the tenth rib models in terms of reaction force at fracture (difference rib responses and bone fractures for the loading conditions considered, but coarse hex-shell models with constant or variable shell thickness were more computationally efficient and therefore preferred. Copyright 2009 Elsevier Ltd. All rights reserved.

Dynamic analysis of isotropic nanoplates subjected to moving load using state-space method based on nonlocal second order plate theory

Energy Technology Data Exchange (ETDEWEB)

Nami, Mohammad Rahim [Shiraz University, Shiraz, Iran (Iran, Islamic Republic of); Janghorban, Maziar [Islamic Azad University, Marvdash (Iran, Islamic Republic of)

2015-06-15

In this work, dynamic analysis of rectangular nanoplates subjected to moving load is presented. In order to derive the governing equations of motion, second order plate theory is used. To capture the small scale effects, the nonlocal elasticity theory is adopted. It is assumed that the nanoplate is subjected to a moving concentrated load with the constant velocity V in the x direction. To solve the governing equations, state-space method is used to find the deflections of rectangular nanoplate under moving load. The results obtained here reveal that the nonlocality has significant effect on the deflection of rectangular nanoplate subjected to moving load.

Reduction mechanism of dynamic loads on down wind rotor; Furyoku hatsuden system down wind rotor no doteki kaju no keigen kiko ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Seki, K; Shimizu, Y; Yasui, T [Tokai University, Tokyo (Japan)

1997-11-25

Dynamic force on blades in a large wind mill changes with rotational speed for various reasons, such as wind shear that causes vertical distribution of wind velocity or titling angle. Therefore, a 2-blade system on a teetered hub is a practical selection for the coned, down-wind type. Use of teetered axis greatly reduces bending moment in the flap direction and that at the axis of rotation. An attempt was made to understand dynamic loads by inertial force resulting from oscillation of the blade rotating on the teetered axis, and thereby to avoid them. The in-plane load can be diminished to zero when the teetered axis is coincided with the center of gravity, but generally cannot be avoided when the blade is strained significantly, except it is operated at the rated condition. The in-plane load and bending moment can be avoided, when rotational freedom is given around the y axis. Dynamic load on a down-wind rotor can be avoided by use of universal joint. 3 refs., 6 figs.

Event-based scenario manager for multibody dynamics simulation of heavy load lifting operations in shipyards

Directory of Open Access Journals (Sweden)

Sol Ha

2016-01-01

Full Text Available This paper suggests an event-based scenario manager capable of creating and editing a scenario for shipbuilding process simulation based on multibody dynamics. To configure various situation in shipyards and easily connect with multibody dynamics, the proposed method has two main concepts: an Actor and an Action List. The Actor represents the anatomic unit of action in the multibody dynamics and can be connected to a specific component of the dynamics kernel such as the body and joint. The user can make a scenario up by combining the actors. The Action List contains information for arranging and executing the actors. Since the shipbuilding process is a kind of event-based sequence, all simulation models were configured using Discrete EVent System Specification (DEVS formalism. The proposed method was applied to simulations of various operations in shipyards such as lifting and erection of a block and heavy load lifting operation using multiple cranes.

Static and Dynamic Stability Analysis of Distributed Energy Resources Components with Storage Devices and Loads for Smart Grids

DEFF Research Database (Denmark)

Mihet-Popa, Lucian; Groza, V.

2011-01-01

of the Smart Grids (SGs). A SG can operate interconnected to the main distribution grid or in islanded mode. This paper presents experimental tests for static and dynamic stability analysis carried out in a dedicated laboratory for research in distributed control and smart grid with a high share of renewable......The distributed energy resources (DER) contains several technologies, such as diesel engines, small wind turbines, photovoltaic inverters, etc. The control of DER components with storage devices and (controllable) loads, such as batteries, capacitors, dump loads, are central to the concept...... energy production. Moreover to point out, on a laboratory scale, the coupling between DR and storage and to effectively compensate wind fluctuations a number of tests have been done. In order to find out the parameters of various types of DER components for dynamic simulation models a number of tests...

The Effect of Small Additions of Carbon Nanotubes on the Mechanical Properties of Epoxy Polymers under Static and Dynamic Loads

Science.gov (United States)

Tarasov, A. E.; Badamshina, E. R.; Anokhin, D. V.; Razorenov, S. V.; Vakorina, G. S.

2018-01-01

The results of measurements of the mechanical characteristics of cured epoxy composites containing small and ultrasmall additions of single-walled carbon nanotubes in the concentration range from 0 to 0.133 wt % under static and dynamic loads are presented. Static measurements of strength characteristics have been carried out under standard test conditions. Measurements of the Hugoniot elastic limit and spall strength were performed under a shock wave loading of the samples at a deformation rate of (0.8-1.5) ß 105 s-1 before the fracture using explosive devices by recording and subsequent analyzing the evolution of the full wave profiles. It has been shown that agglomerates of nanotubes present in the structure of the composites after curing cause a significant scatter of the measured strength parameters, both in the static and in the dynamic test modes. However, the effects of carbon nanotube additions in the studied concentration interval on the physical and mechanical characteristics of the parameters were not revealed for both types of loading.

Earthquakes - dynamic loads on the foundation piles of a nuclear reactor

International Nuclear Information System (INIS)

Henning, F.; Dufour, C.; Fuzier, J.P.; Cheyrezy, M.

1976-01-01

The purpose of this paper is to analyse the behaviour of a piled foundation of a nuclear power plant submitted to earthquake loadings. The actual horizontal stiffness of the compound 'soil + structure' is calculated from the stiffness of the piles and the dynamic characteristics of the different layers of soil. The maximum amplitude of the horizontal displacement of the raft foundation is obtained by an iterative calculation from the displacement spectrum applied to the surrounding earth. At this stage, the moment diagrams for the different types of piles and their required reinforcement are calculated. The response of the nuclear plant components is determined from the displacement spectrum previously obtained for the raft. (author)

Effect of fuel assembly mechanical design changes on dynamic response of reactor pressure vessel system under extreme loadings

International Nuclear Information System (INIS)

Bhandari, D.R.; Hankinson, M.F.

1993-01-01

This paper presents the results of a study to assess the effect of fuel assembly mechanical design changes on the dynamic response of a pressurized water reactor vessel and reactor internals under Loss-Of-Coolant Accident (LOCA) conditions. The results of this study show that the dynamic response of the reactor vessel internals and the core under extreme loadings, such as LOCA, is very sensitive to fuel assembly mechanical design changes. (author)

STUDIES OF ACOUSTIC EMISSION SIGNATURES FOR QUALITY ASSURANCE OF SS 316L WELDED SAMPLES UNDER DYNAMIC LOAD CONDITIONS

Directory of Open Access Journals (Sweden)

S. V. RANGANAYAKULU

2016-10-01

Full Text Available Acoustic Emission (AE signatures of various weld defects of stainless steel 316L nuclear grade weld material are investigated. The samples are fabricated by Tungsten Inert Gas (TIG Welding Method have final dimension of 140 mm x 15 mm x 10 mm. AE signals from weld defects such as Pinhole, Porosity, Lack of Penetration, Lack of Side Fusion and Slag are recorded under dynamic load conditions by specially designed mechanical jig. AE features of the weld defects were attained using Linear Location Technique (LLT. The results from this study concluded that, stress release and structure deformation between the sections in welding area are load conditions major part of Acoustic Emission activity during loading.

Nonlinear response of a post-tensioned concrete structure to static and dynamic internal-pressure loads

International Nuclear Information System (INIS)

Butler, T.A.; Bennett, J.G.

1981-01-01

A nonlinear finite element model of a nuclear power plant containment building was developed to determine its ultimate pressure capability under quasistatic and impulsive dynamic loads. The ADINA finite element computer code was used to develop the model because of its capability to handle concrete cracking and crushing. Results indicate that, even though excessive concrete cracking occurs, failure is ultimately caused by rupture of post-tensioning tendons

Finite element analysis of high modal dynamic responses of a composite floor subjected to human motion under passive live load

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Arash Behnia

Full Text Available Light weight and long span composite floors are common place in modern construction. A critical consequence of this application is undesired vibration which may cause excessive discomfort to occupants. This work investigates the composite floor vibration behavior of an existing building based on a comprehensive study of high modal dynamic responses, the range of which has been absent in previous studies and major analytical templates, of different panels under the influence of loads induced by human motion. The resulting fundamental natural frequency and vibration modes are first validated with respect to experimental and numerical evidences from literature. Departing from close correlation established in comparison, this study explores in detail the effects of intensity of passive live load as additional stationary mass due to crowd jumping as well as considering human structure interaction. From observation, a new approach in the simulation of passive live load through the consideration of human structure interaction and human body characteristics is proposed. It is concluded that higher vibration modes are essential to determine the minimum required modes and mass participation ratio in the case of vertical vibration. The results indicate the need to consider 30 modes of vibration to obtain all possible important excitations and thereby making third harmonic of load frequency available to excite the critical modes. In addition, presence of different intensities of passive live load on the composite floor showed completely different behavior in each particular panel associated with load location of panel and passive live load intensity. Furthermore, implementing human body characteristics in simulation causes an obvious increase in modal damping and hence better practicality and economical presentation can be achieved in structural dynamic behavior.

Dynamic analysis of electric equipment for nuclear power stations under seismic loads

International Nuclear Information System (INIS)

Buck, K.E.; Bodisco, U. von; Winkler, K.

1977-01-01

The response spectrum method, generally accepted as the most practical method for linear seismic analysis of power station components, is here applied in conjunction with the finite element method to electric components. The fully dynamic analysis based on the superposition of the natural modes as carried out for an electronics cabinet and for transmitter supports is outlined and selected results are presented. Several different methods are in use for the superposition of the contributions of the different modes. Here addition of absolute values, the square-root of the sum of squares, and a mixed method taking account of closely spaced modes is applied. For different structures, the degree of conservativity is thus demonstrated, the largest difference in the stresses computed by the different methods being approximately 30%. For structures whose natural frequencies are in the spectrum range with zero period response, a simplified response analysis using static loads is often carried out. This is demonstrated for the electronics cabinet and transmitter mountings, and the results are compared with the fully dynamic analyses. It is seen that this 'pseudo-dynamic' analysis yields useful approximations for the distributions of stresses. Practical details of the structural models as well as results are presented for several switchgear and electronics cabinets

Load event: Aircraft crash

International Nuclear Information System (INIS)

Fritsch, H.

1985-01-01

The bibliography includes 48 quotations, up to the year 1983, on the following issues: Experiments and computational methods. Design load for the dimensioning of reinforced concrete buildings and components with respect to the dynamic load in the event of an aircraft crash. (orig./HP) [de

Prediction of dynamic blade loading of the Francis-99 turbine

International Nuclear Information System (INIS)

Nicolle, J; Cupillard, S

2015-01-01

CFD simulations focusing on capturing dynamic fluctuations of the flow for three operating points were performed for a scale model of a high head Francis turbine. A mesh sensitivity study showed an influence of the near wall resolution, consequently a low Reynolds mesh with a SST turbulence model was used. Rotor/stator fluctuations are well reproduced with the full turbine simulation at all operating points. Velocity contours and average velocity profiles from LDV measurements in the draft tube confirm that the flow physics is generally well reproduced. Simplified approaches such as profile transform and Fourier transform underestimated the measured fluctuations. As full turbine simulations were time-consuming, a simulation with only the draft tube was performed at part load to predict the fluctuations in the draft tube cone. The SAS-SST turbulence model was able to capture the vortex rope behavior

Variable load failure mechanism for high-speed load sensing electro-hydrostatic actuator pump of aircraft

Directory of Open Access Journals (Sweden)

Cun SHI

2018-05-01

Full Text Available This paper presents a novel transient lubrication model for the analysis of the variable load failure mechanism of high-speed pump used in Load Sensing Electro-Hydrostatic Actuator (LS-EHA. Focusing on the slipper/swashplate pair partial abrasion, which is considered as the dominant failure mode in the high-speed condition, slipper dynamic models are established. A forth sliding motion of the slipper on the swashplate surface is presented under the fact that the slipper center of mass will rotate around the center of piston ball when the swashplate angle is dynamically adjusted. Besides, extra inertial tilting moments will be produced for the slipper based on the theorem on translation of force, which will increase rapidly when LS-EHA pump operates under high-speed condition. Then, a dynamic lubricating model coupling with fluid film thickness field, temperature field and pressure field is proposed. The deformation effects caused by thermal deflection and hydrostatic pressure are considered. A numerical simulation model is established to validate the effectiveness and accuracy of the proposed model. Finally, based on the load spectrum of aircraft flight profile, the variable load conditions and the oil film characteristics are analyzed, and series of variable load rules of oil film thickness with variable speed/variable pressure/variable displacement are concluded. Keywords: Coupling lubrication model, Electro-Hydrostatic Actuator (EHA, High-speed pump, Partial abrasion, Slipper pair, Variable load

Material properties for reactor pressure vessels and containment shells under dynamic loading

International Nuclear Information System (INIS)

Albertini, C.

1997-01-01

The effects of high strain rate, dynamic biaxial loading and deformation mode (tension, shear) on the mechanical properties of AISI 316 austenitic stainless steel in as-received and pre-damaged (creep, LCF) conditions are reported. This research was conducted to assess the performances of the containment shell of fast breeder reactors. The results of this research have been utilized to prepare similar investigations for SA 537 Class 1 ferritic steel used for the containment shell of LWR. The first results of these investigations are reported. A programme to study the mechanical properties of plain concrete with real size aggregate at high strain rate is described. (orig.)

Extrapolation of dynamic load behaviour on hydroelectric turbine blades with cyclostationary modelling

Science.gov (United States)

Poirier, Marc; Gagnon, Martin; Tahan, Antoine; Coutu, André; Chamberland-lauzon, Joël

2017-01-01

In this paper, we present the application of cyclostationary modelling for the extrapolation of short stationary load strain samples measured in situ on hydraulic turbine blades. Long periods of measurements allow for a wide range of fluctuations representative of long-term reality to be considered. However, sampling over short periods limits the dynamic strain fluctuations available for analysis. The purpose of the technique presented here is therefore to generate a representative signal containing proper long term characteristics and expected spectrum starting with a much shorter signal period. The final objective is to obtain a strain history that can be used to estimate long-term fatigue behaviour of hydroelectric turbine runners.

Probabilistic Sensitivity Analysis for Launch Vehicles with Varying Payloads and Adapters for Structural Dynamics and Loads

Science.gov (United States)

McGhee, David S.; Peck, Jeff A.; McDonald, Emmett J.

2012-01-01

This paper examines Probabilistic Sensitivity Analysis (PSA) methods and tools in an effort to understand their utility in vehicle loads and dynamic analysis. Specifically, this study addresses how these methods may be used to establish limits on payload mass and cg location and requirements on adaptor stiffnesses while maintaining vehicle loads and frequencies within established bounds. To this end, PSA methods and tools are applied to a realistic, but manageable, integrated launch vehicle analysis where payload and payload adaptor parameters are modeled as random variables. This analysis is used to study both Regional Response PSA (RRPSA) and Global Response PSA (GRPSA) methods, with a primary focus on sampling based techniques. For contrast, some MPP based approaches are also examined.

Transient dynamic finite element analysis of hydrogen distribution test chamber structure for hydrogen combustion loads

International Nuclear Information System (INIS)

Singh, R.K.; Redlinger, R.; Breitung, W.

2005-09-01

Design and analysis of blast resistant structures is an important area of safety research in nuclear, aerospace, chemical process and vehicle industries. Institute for Nuclear and Energy Technologies (IKET) of Research Centre- Karlsruhe (Forschungszentrum Karlsruhe or FZK) in Germany is pursuing active research on the entire spectrum of safety evaluation for efficient hydrogen management in case of the postulated design basis and beyond the design basis severe accidents for nuclear and non-nuclear applications. This report concentrates on the consequence analysis of hydrogen combustion accidents with emphasis on the structural safety assessment. The transient finite element simulation results obtained for 2gm, 4gm, 8gm and 16gm hydrogen combustion experiments concluded recently on the test-cell structure are described. The frequencies and damping of the test-cell observed during the hammer tests and the combustion experiments are used for the present three dimensional finite element model qualification. For the numerical transient dynamic evaluation of the test-cell structure, the pressure time history data computed with CFD code COM-3D is used for the four combustion experiments. Detail comparisons of the present numerical results for the four combustion experiments with the observed time signals are carried out to evaluate the structural connection behavior. For all the combustion experiments excellent agreement is noted for the computed accelerations and displacements at the standard transducer locations, where the measurements were made during the different combustion tests. In addition inelastic analysis is also presented for the test-cell structure to evaluate the limiting impulsive and quasi-static pressure loads. These results are used to evaluate the response of the test cell structure for the postulated over pressurization of the test-cell due to the blast load generated in case of 64 gm hydrogen ignition for which additional sets of computations were

Dynamic response analysis of block foundations with nonlinear dry friction mounting system to impact loads

International Nuclear Information System (INIS)

Zheng, Enlai; Zhu, Sihong; Zhou, Xinlong

2014-01-01

It is essential to establish a dynamic model to predict and evaluate the dynamic performance of a nonlinear dry friction mounting system during design procedure, when it is impossible to carry out the test of prototype. Unlike the conventional ideal dry friction model where the direction of dry friction force is always considered to be opposite to that of relative velocity, a new equivalent resistance model of dry friction force is proposed based on the bilinear hysteretic model by introducing a parameter g in this work. The equivalent resistance contains spring force and damping force, whose direction is not opposite to that of relative velocity. Then, a dynamic model of the block foundation with nonlinear dry friction mounting system is established. When the equivalent resistance is applied to the dynamic model, its dynamic responses are obtained under common practical forms of press loads: rectangular pulse, half-sine pulse, and triangular pulse. Compared to experimental results, the dynamic responses based on the equivalent resistance model are more consistent with the simulation results based on the ideal dry friction model and the validity of the equivalent resistance model for the bilinear hysteretic model in this work is verified. Furthermore, the effect of the pulse shape and pulse duration on the dynamic responses of the block foundation with nonlinear dry friction mounting system is investigated.

Non-linear Dynamic Analysis of Steel Hollow I-core Sandwich Panel under Air Blast Loading

Directory of Open Access Journals (Sweden)

Asghar Vatani Oskouei

2015-12-01

Full Text Available In this paper, the non-linear dynamic response of novel steel sandwich panel with hollow I-core subjected to blast loading was studied. Special emphasis is placed on the evaluation of midpoint displacements and energy dissipation of the models. Several parameters such as boundary conditions, strain rate, mesh dependency and asymmetrical loading are considered in this study. The material and geometric non-linearities are also considered in the numerical simulation. The results obtained are compared with available experimental data to verify the developed FE model. Modeling techniques are described in detail. According to the results, sandwich panels with hollow I-core allowed more plastic deformation and energy dissipation and less midpoint displacement than conventional I-core sandwich panels and also equivalent solid plate with the same weight and material.

Dynamic response of a clamped/free hollow circular cylinder under travelling torsional impact loads

International Nuclear Information System (INIS)

Jonker, J.B.

1982-01-01

Impact-induced vibrations in the casing of a gas centriguge due to a sudden failure of the spinning rotor (crash) can cause structural disintegrity of the casing. In order to study the influence of the rotor failure bahaviour and the impact load histories on the dynamic response of the casing, a simple crash model is proposed in this paper to analyse the transient torsional response due to tangential components of the impact loads. The casing is modeled as a linear-elastic hollow circular cylinder, clamped at the lower end and free at the upper end. The rotor is thought to breakup in identical sections in a sequence determined by its fracture behaviour. Each section is assumed to cause an axi-symmetric load distribution at the inner surface of the casing. Therefore the problem is essentially reduced to the analysis of a clamped/free cylinder under travelling torsional impact loads. The problem is solved by representing the impact loads as local pulses acting over the length of the sections. A perturbation method is used to show that the general two-dimensional theory of axi-symmetric torsional wave propagation in circular cylinders, for the problem under consideration, may be approximated by the elementary one-dimensional theory. Solutions are obtained according to the usual modal expansion approach. Measurements of transient torsional responses are shown to be in good agreement with the calculated responses by choosing a suitable shape of the pulses. The effects of travelling velocity and pulse shape are investigated. Finally the transfer of kinetic energy in the rotor to vibrational energy of torsion in the casing is studied. (orig.)

Rigid-Plastic Approximations for Predicting Plastic Deformation of Cylindrical Shells Subject to Dynamic Loading

Directory of Open Access Journals (Sweden)

Michelle S. Hoo Fatt

1996-01-01

Full Text Available A theoretical approach was developed for predicting the plastic deformation of a cylindrical shell subject to asymmetric dynamic loads. The plastic deformation of the leading generator of the shell is found by solving for the transverse deflections of a rigid-plastic beam/string-on-foundation. The axial bending moment and tensile force in the beam/string are equivalent to the longitudinal bending moments and membrane forces of the shell, while the plastic foundation force is equivalent to the shell circumferential bending moment and membrane resistances. Closed-form solutions for the transient and final deformation profile of an impulsive loaded shell when it is in a “string” state were derived using the eigenfunction expansion method. These results were compared to DYNA 3D predictions. The analytical predictions of the transient shell and final centerline deflections were within 25% of the DYNA 3D results.

Experimental studies of the effects of buffered particle dampers attached to a multi-degree-of-freedom system under dynamic loads

Science.gov (United States)

Lu, Zheng; Lu, Xilin; Lu, Wensheng; Masri, Sami F.

2012-04-01

This paper presents a systematic experimental investigation of the effects of buffered particle dampers attached to a multi-degree-of-freedom (mdof) system under different dynamic loads (free vibration, random excitation as well as real onsite earthquake excitations), and analytical/computational study of such a system. A series of shaking table tests of a three-storey steel frame with the buffered particle damper system are carried out to evaluate the performance and to verify the analysis method. It is shown that buffered particle dampers have good performance in reducing the response of structures under dynamic loads, especially under random excitation case. It can effectively control the fundamental mode of the mdof primary system; however, the control effect for higher modes is variable. It is also shown that, for a specific container geometry, a certain mass ratio leads to more efficient momentum transfer from the primary system to the particles with a better vibration attenuation effect, and that buffered particle dampers have better control effect than the conventional rigid ones. An analytical solution based on the discrete element method is also presented. Comparison between the experimental and computational results shows that reasonably accurate estimates of the response of a primary system can be obtained. Properly designed buffered particle dampers can effectively reduce the response of lightly damped mdof primary system with a small weight penalty, under different dynamic loads.

Comparison of the load-sharing characteristics between pedicle-based dynamic and rigid rod devices

International Nuclear Information System (INIS)

Ahn, Yoon-Ho; Chen, W-M; Lee, Kwon-Yong; Park, Kyung-Woo; Lee, Sung-Jae

2008-01-01

Recently, numerous types of posterior dynamic stabilization (PDS) devices have been introduced as an alternative to the fusion devices for the surgical treatment of degenerative lumbar spine. It is hypothesized that the use of 'compliant' materials such as Nitinol (Ni-Ti alloy, elastic modulus = 75 GPa) or polyether-etherketone (PEEK, elastic modulus = 3.2 GPa) in PDS can restore stability of the lumbar spine without adverse stress-shielding effects that have often been found with 'rigid' fusion devices made of 'rigid' Ti alloys (elastic modulus = 114 GPa). Previous studies have shown that suitably designed PDS devices made of more compliant material may be able to help retain kinematic behavior of the normal spine with optimal load sharing between the anterior and posterior spinal elements. However, only a few studies on their biomechanical efficacies are available. In this study, we conducted a finite-element (FE) study to investigate changes in load-sharing characteristics of PDS devices. The implanted models were constructed after modifying the previously validated intact model of L3-4 spine. Posterior lumbar fusion with three different types of pedicle screw systems was simulated: a conventional rigid fixation system (Ti6Al4V, Φ = 6.0 mm) and two kinds of PDS devices (one with Nitinol rod with a three-coiled turn manner, Φ = 4.0 mm; the other with PEEK rod with a uniform cylindrical shape, Φ = 6.0 mm). To simulate the load on the lumbar spine in a neutral posture, an axial compressive load (400 N) was applied. Subsequently, the changes in load-sharing characteristics and stresses were investigated. When the compressive load was applied on the implanted models (Nitinol rod, PEEK rod, Ti-alloy rod), the predicted axial compressive loads transmitted through the devices were 141.8 N, 109.8 N and 266.8 N, respectively. Axial forces across the PDS devices (Nitinol rod, PEEK rod) and rigid system (Ti-alloy rod) with facet joints were predicted to take over 41%, 33

Bearing Capacity of Foundations subjected to Impact Loads

DEFF Research Database (Denmark)

Ibsen, Lars Bo; Jakobsen, Kim Parsberg

1996-01-01

In the design process for foundations, the bearing capacity calculations are normally restricted to monotonic loads. Even in cases where the impact load is of significance the dynamic aspects are neglected by use of a traditional deterministic ultimate limit state analysis. Nevertheless it is com......In the design process for foundations, the bearing capacity calculations are normally restricted to monotonic loads. Even in cases where the impact load is of significance the dynamic aspects are neglected by use of a traditional deterministic ultimate limit state analysis. Nevertheless...

Characteristics and modeling of spruce wood under dynamic compression load

International Nuclear Information System (INIS)

Eisenacher, Germar

2014-01-01

Spruce wood is frequently used as an energy absorbing material in impact limiters of packages for the transportation of radioactive material. A 9m drop test onto an unyielding target is mandatory for the packages. The impact results in a dynamic compression load of the spruce wood inside the impact limiter. The lateral dilation of the wood is restrained thereby due to encasing steel sheets. This work's objective was to provide a material model for spruce wood based on experimental investigations to enable the calculation of such loading conditions. About 600 crush tests with cubical spruce wood specimens were performed to characterize the material. The compression was up to 70% and the material was assumed to be transversely isotropic. Particularly the lateral constraint showed to have an important effect: the material develops a high lateral dilation without lateral constraint. The force-displacement characteristics show a comparably low force level and no or only slight hardening. Distinctive softening occurs after the linear-elastic region when loaded parallel to the fiber. On the other hand, using a lateral constraint results in significantly higher general force levels, distinctive hardening and lateral forces. The softening effect when loaded parallel to the fiber is less distinctive. Strain rate and temperature raise or lower the strength level, which was quantified for the applicable ranges of impact limiters. The hypothesis of an uncoupled evolution of the yield surface was proposed based on the experimental findings. It postulates an independent strength evolution with deviatoric and volumetric deformation. The hypothesis could be established using the first modeling approach, the modified LS-DYNA material model MAT075. A transversely isotropic material model was developed based thereupon and implemented in LS-DYNA. The material characteristics of spruce wood were considered using a multi-surface yield criterion and a non-associated flow rule. The yield

Load Estimation by Frequency Domain Decomposition

DEFF Research Database (Denmark)

Pedersen, Ivar Chr. Bjerg; Hansen, Søren Mosegaard; Brincker, Rune

2007-01-01

When performing operational modal analysis the dynamic loading is unknown, however, once the modal properties of the structure have been estimated, the transfer matrix can be obtained, and the loading can be estimated by inverse filtering. In this paper loads in frequency domain are estimated by ...

The relationship between pain and dynamic knee joint loading in knee osteoarthritis varies with radiographic disease severity. A cross sectional study.

Science.gov (United States)

Henriksen, Marius; Aaboe, Jens; Bliddal, Henning

2012-08-01

In a cross sectional study, we investigated the relationships between knee pain and mechanical loading across the knee, as indicated by the external knee adduction moment (KAM) during walking in patients with symptomatic knee OA who were distinguished by different radiographic disease severities. Data from 137 symptomatic medial knee OA patients were used. Based on Kellgren/Lawrence (K/L) grading, the patients were divided into radiographically less severe (K/L ≤ 2, n=68) or severe (K/L>2, n=69) medial knee OA. Overall knee pain was rated on a 10 cm visual analog scale, and peak KAM and KAM impulses were obtained from gait analyses. Mixed linear regression analyses were performed with KAM variables as the outcome, and pain and disease severity as independent variables, adjusting for age, gender, and walking speed. In adjusted analyses, less severe patients demonstrated negative relationships between pain intensities and dynamic loading. The severe patient group showed no relationship between pain intensity and peak KAM, and a positive relationship between pain intensity and KAM impulse. In radiographically less severe knee OA, the negative relationships between pain intensity and dynamic knee joint loading indicate a natural reaction to pain, which will limit the stress on the joint. In contrast, either absent or positive relationships between pain and dynamic loading in severe OA may lead to overuse and accelerated disease progression. These findings may have a large potential interest for strategies of treatment in knee OA. Copyright © 2011 Elsevier B.V. All rights reserved.

Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

Energy Technology Data Exchange (ETDEWEB)

Lambert, P. K.; Hustedt, C. J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C. [Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Vecchio, K. S. [Department of NanoEngineering, University of California San Diego, La Jolla, California 92093 (United States); Huskins, E. L. [Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37830 (United States); US Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland 21005 (United States); Casem, D. T. [US Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland 21005 (United States); Gruner, S. M. [Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853 (United States); Tate, M. W.; Philipp, H. T.; Purohit, P.; Weiss, J. T. [Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Woll, A. R. [Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853 (United States); Kannan, V.; Ramesh, K. T. [Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Kenesei, P.; Okasinski, J. S.; Almer, J. [X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2014-09-15

We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼10{sup 3}–10{sup 4} s{sup −1} in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

Effects of dynamic loading of motor-operated valve actuators

International Nuclear Information System (INIS)

Damerell, P.S.; Daubresse, S.; Wolfe, K.J.; Dogan, T.; Gleeson, J.

1994-01-01

Experience has shown that valves with rising, nonrotating stems that are operated using electro-motor driven actuators can be susceptible to changes in output thrust at a constant torque switch setting as a result of changes in stem load time history. This effect is a concern because tests on these types of valves to verify thrust achieved at torque switch trip are often performed in situ under load conditions different from the required performance conditions. As part of a motor-operated valve research program being carried out by the Electric Power Research Institute, tests of typical electric motor actuators used with nuclear services valves have been performed. The test results show that changes in output thrust with load time history occur o varying degrees on different stem and stem nut combinations. When the effect exists, there is generally an increase in thrust at torque switch trip when load is developed rapidly from low initial loads, compared to when load is developed slowly. The effect is mainly a result of changes in the coefficient of friction at the stem-stem nut interface. The coefficient of friction is temporarily reduced under rapid loading conditions from low initial load, leading to increased thrust. The root cause is hypothesized to be a open-quotes squeeze-filmclose quotes effect, whereby mixed-mode lubrication (hydrodynamic plus boundary) temporarily replaces boundary lubrication. This paper describes the results of tests performed to better understand the phenomenon

Instability predictions for circumferentially cracked Type-304 stainless steel pipes under dynamic loading. Volume 2. Appendixes. Final report

International Nuclear Information System (INIS)

Zahoor, A.; Wilkowski, G.; Abou-Sayed, I.; Marschall, C.; Broek, D.; Sampath, S.; Rhee, H.; Ahmad, J.

1982-04-01

This report provides methods to predict margins of safety for circumferentially cracked Type 304 stainless steel pipes subjected to applied bending loads. An integrated combination of experimentation and analysis research was pursued. Two types of experiments were performed: (1) laboratory-scale tests on center-cracked panels and bend specimens to establish the basic mechanical and fracture properties of Type 304 stainless steel, and (2) full-scale pipe fracture tests under quasi-static and dynamic loadings to assess the analysis procedures. Analyses were based upon the simple plastic collapse criterion, a J-estimation procedure, and elastic-plastic large-deformation finite element models

Dynamic buckling and nonlinear response of FBR main vessels under earthquake loading

International Nuclear Information System (INIS)

Hagiwara, Yutaka; Kawamoto, Yoji; Nakagawa, Masaki; Akiyama, Hiroshi.

1991-01-01

Pseudo-dynamic tests of cylindrical shells under high temperature were performed in order to study elasto-plastic shear-bending buckling and the nonlinear response of FBR main vessels under earthquake loading. The test results showed a response reduction effect due to pre-buckling plasticity, and a large seismic margin due to post-buckling energy absorption of the cylinders. A simple expression of the response reduction effect was proposed, as a contribution to the safe and effective seismic design of FBRs. Two methods for seismic margin evaluation were also proposed, and it was shown that appropriate seismic margins can be ensured, when the response reduction effect is incorporated into the seismic design. (author)

Load Balancing of Parallel Monte Carlo Transport Calculations

International Nuclear Information System (INIS)

Procassini, R J; O'Brien, M J; Taylor, J M

2005-01-01

The performance of parallel Monte Carlo transport calculations which use both spatial and particle parallelism is increased by dynamically assigning processors to the most worked domains. Since he particle work load varies over the course of the simulation, this algorithm determines each cycle if dynamic load balancing would speed up the calculation. If load balancing is required, a small number of particle communications are initiated in order to achieve load balance. This method has decreased the parallel run time by more than a factor of three for certain criticality calculations

A dynamic switching strategy for air-conditioning systems operated in light-thermal-load conditions

International Nuclear Information System (INIS)

Lin, Jin-Long; Yeh, T.-J.; Hwang, Wei-Yang

2009-01-01

Recently, modern air-conditioners have begun to incorporate variable-speed compressors and variable-opening expansion valves, together with feedback control to improve the performance and energy efficiency. However, for the compressor there usually exists a low-speed limit below which its speed can not be continuously modulated unless it is completely turned off. When the air-conditioning system is operated in light-thermal-load conditions, the low-speed limit causes the compressor to run in an on-off manner which can significantly degrade the performance and efficiency. In this paper, a dynamic switching strategy is proposed for such scenarios. The strategy is basically an integration of a cascading control structure, an intuitive switching strategy, and a dynamic compensator. While the control structure provides the nominal performance, the intuitive switching strategy and the dynamic compensator together can account for the compressor's low-speed limitation. Theoretical analysis reveals that when the output matrix of the dynamic compensator is chosen properly, the proposed strategy can effectively reduce the output error caused by the on-off operation of the compressor. Experiments also demonstrate that the proposed strategy can simultaneously provide better regulation for the indoor temperature and improve the energy efficiency at steady state.

Dynamic axle and wheel loads identification: laboratory studies

Science.gov (United States)

Zhu, X. Q.; Law, S. S.

2003-12-01

Two methods have been reported by Zhu and Law to identify moving loads on the top of a bridge deck. One is based on the exact solution (ESM) and the other is based on the finite element formulation (FEM). Simulation studies on the effect of different influencing factors have been reported previously. This paper comparatively studies the performances of these two methods with experimental measurements obtained from a bridge/vehicle system in the laboratory. The strains of the bridge deck are measured when a model car moves across the bridge deck along different paths. The moving loads on the bridge deck are identified from the measured strains using these two methods, and the responses are reconstructed from the identified loads for comparison with the measured responses to verify the performances of these methods. Studies on the identification accuracy due to the effect of the number of vibration mode used, the number of measuring points and eccentricities of travelling paths are performed. Results show that the ESM could identify the moving loads individually or as axle loads when they are travelling at an eccentricity with the sensors located close to the travelling path of the forces. And the accuracy of the FEM is dependent on the amount of measured information used in the identification.

Seasonal dynamics in wheel load-carrying capacity of a loam soil in the Swiss Plateau

DEFF Research Database (Denmark)

Gut, S.; Chervet, A.; Stettler, Matthias

2015-01-01

on in situ measurements of h, measurements of precompression stress at various h and simulations of soil stress. In this work, we concentrated on prevention of subsoil compaction. Calculations were made for different tyres (standard and low-pressure top tyres) and for soil under different tillage......Subsoil compaction is a major problem in modern agriculture caused by the intensification of agricultural production and the increase in weight of agricultural machinery. Compaction in the subsoil is highly persistent and leads to deterioration of soil functions. Wheel load-carrying capacity (WLCC......) is defined as the maximum wheel load for a specific tyre and inflation pressure that does not result in soil stress in excess of soil strength. The soil strength and hence WLCC is strongly influenced by soil matric potential (h). The aim of this study was to estimate the seasonal dynamics in WLCC based...

Concrete structures under impact loading: general aspects

Directory of Open Access Journals (Sweden)

Cornelia Baeră

2016-09-01

Full Text Available Dynamic loading conditions distress the structural integrity of a structure differently than the static ones. Such actions transfer high rate strains and instant energy waves to the structure, inducing the possibility of imminent collapse and casualties as a direct consequence. In the latest years, considering the dramatic increase of terrorist threats and global warming, the structural safety criteria imply more than ever the need to withstand this kind of loading (e.g., missiles and blast, projectiles, strong winds, tornados and earthquakes in addition to the static ones. The aim of this paper is to provide a general overview with regard to impact loading in terms of defining the phenomenon from physical and mechanical perspective, its complex local or global effect on the targeted structure, relevant material characteristics, main research approaches, namely theoretical studies and experimental procedures developed for improving the predictability of the dynamic loads and their effects. New directions in developing superior cementitious composites, with better characteristics in terms of dynamic loading performance are also emphasized.

Internal cycling, not external loading, decides the nutrient limitation in eutrophic lake: A dynamic model with temporal Bayesian hierarchical inference.

Science.gov (United States)

Wu, Zhen; Liu, Yong; Liang, Zhongyao; Wu, Sifeng; Guo, Huaicheng

2017-06-01

Lake eutrophication is associated with excessive anthropogenic nutrients (mainly nitrogen (N) and phosphorus (P)) and unobserved internal nutrient cycling. Despite the advances in understanding the role of external loadings, the contribution of internal nutrient cycling is still an open question. A dynamic mass-balance model was developed to simulate and measure the contributions of internal cycling and external loading. It was based on the temporal Bayesian Hierarchical Framework (BHM), where we explored the seasonal patterns in the dynamics of nutrient cycling processes and the limitation of N and P on phytoplankton growth in hyper-eutrophic Lake Dianchi, China. The dynamic patterns of the five state variables (Chla, TP, ammonia, nitrate and organic N) were simulated based on the model. Five parameters (algae growth rate, sediment exchange rate of N and P, nitrification rate and denitrification rate) were estimated based on BHM. The model provided a good fit to observations. Our model results highlighted the role of internal cycling of N and P in Lake Dianchi. The internal cycling processes contributed more than external loading to the N and P changes in the water column. Further insights into the nutrient limitation analysis indicated that the sediment exchange of P determined the P limitation. Allowing for the contribution of denitrification to N removal, N was the more limiting nutrient in most of the time, however, P was the more important nutrient for eutrophication management. For Lake Dianchi, it would not be possible to recover solely by reducing the external watershed nutrient load; the mechanisms of internal cycling should also be considered as an approach to inhibit the release of sediments and to enhance denitrification. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dynamic-ETL: a hybrid approach for health data extraction, transformation and loading.

Science.gov (United States)

Ong, Toan C; Kahn, Michael G; Kwan, Bethany M; Yamashita, Traci; Brandt, Elias; Hosokawa, Patrick; Uhrich, Chris; Schilling, Lisa M

2017-09-13

Electronic health records (EHRs) contain detailed clinical data stored in proprietary formats with non-standard codes and structures. Participating in multi-site clinical research networks requires EHR data to be restructured and transformed into a common format and standard terminologies, and optimally linked to other data sources. The expertise and scalable solutions needed to transform data to conform to network requirements are beyond the scope of many health care organizations and there is a need for practical tools that lower the barriers of data contribution to clinical research networks. We designed and implemented a health data transformation and loading approach, which we refer to as Dynamic ETL (Extraction, Transformation and Loading) (D-ETL), that automates part of the process through use of scalable, reusable and customizable code, while retaining manual aspects of the process that requires knowledge of complex coding syntax. This approach provides the flexibility required for the ETL of heterogeneous data, variations in semantic expertise, and transparency of transformation logic that are essential to implement ETL conventions across clinical research sharing networks. Processing workflows are directed by the ETL specifications guideline, developed by ETL designers with extensive knowledge of the structure and semantics of health data (i.e., "health data domain experts") and target common data model. D-ETL was implemented to perform ETL operations that load data from various sources with different database schema structures into the Observational Medical Outcome Partnership (OMOP) common data model. The results showed that ETL rule composition methods and the D-ETL engine offer a scalable solution for health data transformation via automatic query generation to harmonize source datasets. D-ETL supports a flexible and transparent process to transform and load health data into a target data model. This approach offers a solution that lowers technical

Dynamic Stability of Columns Subjected to Follower Loads: a Survey

Science.gov (United States)

LANGTHJEM, M. A.; SUGIYAMA, Y.

2000-12-01

This paper offers a survey of simple, flexible structural elements subjected to non-conservative follower loads, such as those caused by the thrust of rocket- and jet engines, and by dry friction in automotive disk- and drum-brake systems. Emphasis is on the “canonical problems”, Beck's, Reut's, Leipholz's, and Hauger's columns. Beck's and Reut's columns have been realized experimentally, and very good agreement between theory and experiments has been found. Leipholz's column is basically realized in an automobile brake system, where noise due to dynamic or parametric instability (brake squeal) is a well-known environmental problem. It is attempted to give a broad overview, with emphasis on experimental works and the associated theoretical problems. Structural optimization is also included in the review, as many studies in that area have served an important purpose in the development of optimization techniques for practical, large-scale optimization problems with non-conservative forces, such as in aeroelasticity.

Failure behavior / characteristics of fabric reinforced polymer matrix composite and aluminum6061 on dynamic tensile loading

Energy Technology Data Exchange (ETDEWEB)

Bang, Hyejin; Cho, Chongdu [Inha University, Incheon (Korea, Republic of)

2017-08-15

Composite materials are composed of multiple types of materials as reinforcement and matrix. Among them, CFRP (Carbon fiber reinforced polymer) is widely used materials in automotive and defense industry. Carbon fibers are used as a reinforcement, of which Young's modulus is in a prepreg form. In automotive industry, especially, high strain rate test is needed to measure dynamic properties, used in dynamic analysis like high inertia included simulation as a car crash. In this paper, a SHTB (Split Hopkinson tensile bar) machine is employed for estimating stress-strain curve under dynamic load condition on aluminum 6061 and CFRP. The strain rate range is about from 100 /s to 1000 /s and the number of prepreg layers of composite specimen is total eight plies which are stacked symmetrically to structure CFRP. As a result, stress / strain point data are obtained and used for simulation into stacked composites.

Failure behavior / characteristics of fabric reinforced polymer matrix composite and aluminum6061 on dynamic tensile loading

International Nuclear Information System (INIS)

Bang, Hyejin; Cho, Chongdu

2017-01-01

Composite materials are composed of multiple types of materials as reinforcement and matrix. Among them, CFRP (Carbon fiber reinforced polymer) is widely used materials in automotive and defense industry. Carbon fibers are used as a reinforcement, of which Young's modulus is in a prepreg form. In automotive industry, especially, high strain rate test is needed to measure dynamic properties, used in dynamic analysis like high inertia included simulation as a car crash. In this paper, a SHTB (Split Hopkinson tensile bar) machine is employed for estimating stress-strain curve under dynamic load condition on aluminum 6061 and CFRP. The strain rate range is about from 100 /s to 1000 /s and the number of prepreg layers of composite specimen is total eight plies which are stacked symmetrically to structure CFRP. As a result, stress / strain point data are obtained and used for simulation into stacked composites.

Three-dimensional dynamic analysis of knee joint during gait in medial knee osteoarthritis using loading axis of knee.

Science.gov (United States)

Nishino, Katsutoshi; Omori, Go; Koga, Yoshio; Kobayashi, Koichi; Sakamoto, Makoto; Tanabe, Yuji; Tanaka, Masaei; Arakawa, Masaaki

2015-07-01

We recently developed a new method for three-dimensional evaluation of mechanical factors affecting knee joint in order to help identify factors that contribute to the progression of knee osteoarthritis (KOA). This study aimed to verify the clinical validity of our method by evaluating knee joint dynamics during gait. Subjects were 41 individuals (14 normal knees; 8 mild KOAs; 19 severe KOAs). The positions of skin markers attached to the body were captured during gait, and bi-planar X-ray images of the lower extremities were obtained in standing position. The positional relationship between the markers and femorotibial bones was determined from the X-ray images. Combining this relationship with gait capture allowed for the estimation of relative movement between femorotibial bones. We also calculated the point of intersection of loading axis of knee on the tibial proximal surface (LAK point) to analyze knee joint dynamics. Knee flexion range in subjects with severe KOA during gait was significantly smaller than that in those with normal knees (p=0.011), and knee adduction in those with severe KOA was significantly larger than in those with mild KOA (p<0.000). LAK point was locally loaded on the medial compartment of the tibial surface as KOA progressed, with LAK point of subjects with severe KOA rapidly shifting medially during loading response. Local loading and medial shear force were applied to the tibial surface during stance phase as medial KOA progressed. Our findings suggest that our method is useful for the quantitative evaluation of mechanical factors that affect KOA progression. Copyright © 2015 Elsevier B.V. All rights reserved.

Dynamic analysis of scraper conveyor operation with external loads

Directory of Open Access Journals (Sweden)

Świder Jerzy

2017-01-01

Full Text Available A load to an armoured face conveyor (AFC during coal mining is changeable and very difficult or even impossible to be predicted. Changes of the load to the upper scraper chain affect the load of the driving motor and generate changes in a scraper chain tension. Impact of increasing the external load to the upper scraper chain on the operation of electric motors and on the scraper chain tension is presented. The developed numerical model of the Rybnik 850 conveyor enabled identifying the places of the scraper chain high tension or places of its loosening. An impact of changing frequency of driving motor voltage on AFC’s operational conditions was tested and analysed using the AFC’s numerical model. During tests, tension of the scraper chain on the discharge end and the return end was recorded. High tension of the scraper chain and its loosening during the changeable load were also recorded on upward and downward transportation of run-of-mine material.

A dynamic capacity degradation model and its applications considering varying load for a large format Li-ion battery

International Nuclear Information System (INIS)

Ouyang, Minggao; Feng, Xuning; Han, Xuebing; Lu, Languang; Li, Zhe; He, Xiangming

2016-01-01

Highlights: • A dynamic capacity degradation model for large format Li-ion battery is proposed. • The change of the model parameters directly link with the degradation mechanisms. • The model can simulate the fading behavior of Li-ion battery under varying loads. • The model can help evaluate the longevity of a battery system under specific load. • The model can help predict the evolution of cell variations within a battery pack. - Abstract: The capacity degradation of the lithium ion battery should be well predicted during battery system design. Therefore, high-fidelity capacity degradation models that are suitable for the task of capacity prediction are required. This paper proposes a novel capacity degradation model that can simulate the degradation dynamics under varying working conditions for large-format lithium ion batteries. The degradation model is built based on a mechanistic and prognostic model (MPM) whose parameters are closely linked with the degradation mechanisms of lithium ion batteries. Chemical kinetics was set to drive the parameters of the MPM to change as capacity degradation continues. With the dynamic parameters of the MPM, the capacity predicted by the degradation model decreases as the cycle continues. Accelerated aging tests were conducted on three types of commercial lithium ion batteries to calibrate the capacity degradation model. The good fit with the experimental data indicates that the model can capture the degradation mechanisms well for different types of commercial lithium ion batteries. Furthermore, the calibrated model can be used to (1) evaluate the longevity of a battery system under a specific working load and (2) predict the evolution of cell variations within a battery pack when different cell works at different conditions. Correlated applications are discussed using the calibrated degradation model.

Molecular dynamics simulation of shock-wave loading of copper and titanium

Science.gov (United States)

Bolesta, A. V.; Fomin, V. M.

2017-10-01

At extreme pressures and temperatures common materials form new dense phases with compacted atomic arrangements. By classical molecular dynamics simulation we observe that FCC copper undergo phase transformation to BCC structure. The transition occurs under shock wave loading at the pressures above 80 GPa and corresponding temperatures above 2000 K. We calculate phase diagram, show that at these pressures and low temperature FCC phase of copper is still stable and discuss the thermodynamic reason for phase transformation at high temperature shock wave regime. Titanium forms new hexagonal phase at high pressure as well. We calculate the structure of shock wave in titanium and observe that shock front splits in three parts: elastic, plastic and phase transformation. The possibility of using a phase transition behind a shock wave with further unloading for designing nanocrystalline materials with a reduced grain size is also shown.

Wind loads on flat plate photovoltaic array fields (nonsteady winds)

Science.gov (United States)

Miller, R. D.; Zimmerman, D. K.

1981-01-01

Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.

Does aquatic exercise reduce hip and knee joint loading? In vivo load measurements with instrumented implants.

Directory of Open Access Journals (Sweden)

Ines Kutzner

Full Text Available Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW. Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36-55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated

Functional adaptation to mechanical loading in both cortical and cancellous bone is controlled locally and is confined to the loaded bones.

Science.gov (United States)

Sugiyama, Toshihiro; Price, Joanna S; Lanyon, Lance E

2010-02-01

In order to validate whether bones' functional adaptation to mechanical loading is a local phenomenon, we randomly assigned 21 female C57BL/6 mice at 19 weeks of age to one of three equal numbered groups. All groups were treated with isoflurane anesthesia three times a week for 2 weeks (approximately 7 min/day). During each anaesthetic period, the right tibiae/fibulae in the DYNAMIC+STATIC group were subjected to a peak dynamic load of 11.5 N (40 cycles with 10-s intervals between cycles) superimposed upon a static "pre-load" of 2.0 N. This total load of 13.5 N engendered peak longitudinal strains of approximately 1400 microstrain on the medial surface of the tibia at a middle/proximal site. The right tibiae/fibulae in the STATIC group received the static "pre-load" alone while the NOLOAD group received no artificial loading. After 2 weeks, the animals were sacrificed and both tibiae, fibulae, femora, ulnae and radii analyzed by three-dimensional high-resolution (5 mum) micro-computed tomography (microCT). In the DYNAMIC+STATIC group, the proximal trabecular percent bone volume and cortical bone volume at the proximal and middle levels of the right tibiae as well as the cortical bone volume at the middle level of the right fibulae were markedly greater than the left. In contrast, the left bones in the DYNAMIC+STATIC group showed no differences compared to the left or right bones in the NOLOAD or STATIC group. These microCT data were confirmed by two-dimensional examination of fluorochrome labels in bone sections which showed the predominantly woven nature of the new bone formed in the loaded bones. We conclude that the adaptive response in both cortical and trabecular regions of bones subjected to short periods of dynamic loading, even when this response is sufficiently vigorous to stimulate woven bone formation, is confined to the loaded bones and does not involve changes in other bones that are adjacent, contra-lateral or remote to them. (c) 2009 Elsevier Inc

Predicting Ultimate Loads for Wind Turbine Design

International Nuclear Information System (INIS)

Madsen, P. H.; Pierce, K.; Buhl, M.

1998-01-01

This paper addresses the statistical uncertainty of loads prediction using structural dynamics simulation codes and the requirements for the number and duration of simulations for obtaining robust load estimates

Instability predictions for circumferentially cracked Type-304 stainless steel pipes under dynamic loading. Volume 2. Appendixes. Final report. [BWR

Energy Technology Data Exchange (ETDEWEB)

Zahoor, A.; Wilkowski, G.; Abou-Sayed, I.; Marschall, C.; Broek, D.; Sampath, S.; Rhee, H.; Ahmad, J.

1982-04-01

This report provides methods to predict margins of safety for circumferentially cracked Type 304 stainless steel pipes subjected to applied bending loads. An integrated combination of experimentation and analysis research was pursued. Two types of experiments were performed: (1) laboratory-scale tests on center-cracked panels and bend specimens to establish the basic mechanical and fracture properties of Type 304 stainless steel, and (2) full-scale pipe fracture tests under quasi-static and dynamic loadings to assess the analysis procedures. Analyses were based upon the simple plastic collapse criterion, a J-estimation procedure, and elastic-plastic large-deformation finite element models.

Strength resistance of reinforced concrete elements of high-rise buildings under dynamic loads

Directory of Open Access Journals (Sweden)

Berlinov Mikhail

2018-01-01

Full Text Available A new method for calculating reinforced concrete constructions of high-rise buildings under dynamic loads from wind, seismic, transport and equipment based on the initial assumptions of the modern phenomenological theory of a nonlinearly deformable elastic-creeping body is proposed. In the article examined the influence of reinforcement on the work of concrete in the conditions of triaxial stress-strain state, based on the compatibility of the deformation of concrete and reinforcement. Mathematical phenomenological equations have been obtained that make it possible to calculate the reinforced concrete elements working without and with cracks. A method for linearizing of these equations based on integral estimates is proposed, which provides the fixation of the vibro-creep processes in the considered period of time. Application of such a technique using the finite-difference method, step method and successive approximations will allow to find a numerical solution of the problem. Such an approach in the design of reinforced concrete constructions will allow not only more fully to take into account the real conditions of their work, revealing additional reserves of load capacity, but also to open additional opportunities for analysis and forecasting their functioning at various stages of operation.

Intracellular localization and dynamics of Hypericin loaded PLLA nanocarriers by image correlation spectroscopy.

Science.gov (United States)

Penjweini, Rozhin; Deville, Sarah; D'Olieslaeger, Lien; Berden, Mandy; Ameloot, Marcel; Ethirajan, Anitha

2015-11-28

The study of cell-nanoparticle interactions is an important aspect for understanding drug delivery using nanocarriers. In this regard, advances in fluorescence based microscopy are useful for the investigation of temporal and spatial behavior of nanoparticles (NPs) within the intracellular environment. In this work, we focus on the delivery of the naturally-occurring hydrophobic photosensitizer Hypericin in human lung carcinoma A549 cells by using biodegradable poly L-lactic acid NPs. For the first time, Hypericin containing NPs are prepared by combining the miniemulsion technique with the solvent evaporation method. This approach yields an efficient loading of the NPs with Hypericin and allows for additional cargo molecules. To monitor the release of Hypercin from the NPs, an additional fluorescent lipophilic dye Coumarin-6 is incorporated in the NPs. Temporal and spatiotemporal image correlation spectroscopy is used to determine the fate of the NPs carrying the potential cargo. Both directed and non-directed motions are detected. By using image cross-correlation spectroscopy and specific fluorescent labeling of endosomes, lysosomes and mitochondria, the dynamics of the cargo loaded NPs in association with the organelles is studied. Copyright © 2015 Elsevier B.V. All rights reserved.

Strength resistance of reinforced concrete elements of high-rise buildings under dynamic loads

Science.gov (United States)

Berlinov, Mikhail

2018-03-01

A new method for calculating reinforced concrete constructions of high-rise buildings under dynamic loads from wind, seismic, transport and equipment based on the initial assumptions of the modern phenomenological theory of a nonlinearly deformable elastic-creeping body is proposed. In the article examined the influence of reinforcement on the work of concrete in the conditions of triaxial stress-strain state, based on the compatibility of the deformation of concrete and reinforcement. Mathematical phenomenological equations have been obtained that make it possible to calculate the reinforced concrete elements working without and with cracks. A method for linearizing of these equations based on integral estimates is proposed, which provides the fixation of the vibro-creep processes in the considered period of time. Application of such a technique using the finite-difference method, step method and successive approximations will allow to find a numerical solution of the problem. Such an approach in the design of reinforced concrete constructions will allow not only more fully to take into account the real conditions of their work, revealing additional reserves of load capacity, but also to open additional opportunities for analysis and forecasting their functioning at various stages of operation.

Report of the US Nuclear Regulatory Commission Piping Review Committee. Volume 4. Evaluation of other loads and load combinations

International Nuclear Information System (INIS)

1984-12-01

Six topical areas were covered by the Task Group on Other Dynamic Loads and Load Combinations as described below: Event Combinations - dealing with the potential simultaneous occurrence of earthquakes, pipe ruptures, and water hammer events in the piping design basis; Response Combinations - dealing with multiply supported piping with independent inputs, the sequence of combinations between spacial and modal components of response, and the treatment of high frequency modes in combination with low frequency modal responses; Stress Limits/Dynamic Allowables - dealing with inelastic allowables for piping and strain rate effects; Water Hammer Loadings - dealing with code and design specifications for these loadings and procedures for identifying potential water hammer that could affect safety; Relief Valve Opening and Closing Loads - dealing with the adequacy of analytical tools for predicting the effects of these events and, in addition, with estimating effective cycles for fatigue evaluations; and Piping Vibration Loads - dealing with evaluation procedures for estimating other than seismic vibratory loads, the need to consider reciprocating and rotary equipment vibratory loads, and high frequency vibratory loads. NRC staff recommendations or regulatory changes and additional study appear in this report

Experimental and numerical analysis concerning the behaviour of OL50 steel grade specimens coated with polyurea layer under dynamics loadings

Directory of Open Access Journals (Sweden)

Bucur Florina

2015-01-01

Full Text Available This study refers to an experimental and numerical evaluation of a polyurea coating layer influence on the dynamic behaviour of OL50 specimens. Mechanical quasi-static and dynamic tensile tests were performed in axial loading conditions, for 2 mm steel plate specimens. Several metallic specimens have been previously coated with 1.5 mm and 3 mm respectively thickness polyurea layer and tested in traction. The findings results indicate that the presence of polyurea changes the loading pattern of metallic material in the necking area. In terms of polyurea coated metal specimens fracture, there was clearly observed a change of fracture limit. One possible explanation of this phenomenon is the modification of triaxiality state in the necking zone, fact proven by the numerical simulations. Test results indicate that the presence of polyurea layer delays the necking onset phenomenon which precedes the OL50 metallic specimen fracture.

15N NMR relaxation studies of calcium-loaded parvalbumin show tight dynamics compared to those of other EF-hand proteins

DEFF Research Database (Denmark)

Baldellon, C; Alattia, J R; Strub, M P

1998-01-01

Dynamics of the rat alpha-parvalbumin calcium-loaded form have been determined by measurement of 15N nuclear relaxation using proton-detected heteronuclear NMR spectroscopy. The relaxation data were analyzed using spectral density functions and the Lipari-Szabo formalism. The major dynamic features...... for the rat alpha-parvalbumin calcium-loaded form are (1) the extreme rigidity of the helix-loop-helix EF-hand motifs and the linker segment connecting them, (2) the N and C termini of the protein being restricted in their mobility, (3) a conformational exchange occurring at the kink of helix D, and (4...... properties which are conserved in the EF-hand domains from different members of this superfamily: (1) a tendency toward higher mobility of NH vectors at relative position 2 in the Ca2+-binding loop, (2) a restricted mobility for the other residues in the binding loop, and (3) an overall rigidity...

Response of borehole extensometers to explosively generated dynamic loads

International Nuclear Information System (INIS)

Patrick, W.C.; Brough, W.G.

1980-01-01

Commercially available, hydraulically anchored, multiple-point borehole extensometers (MPBX) were evaluated with respect to response to dynamic loads produced by explosions. This study is part of the DOE-funded Spent Fuel Test-Climax (SFT-C), currently being conducted in the Climax granitic stock at the Nevada Test Site. The SFT-C is an investigation of the feasibility of short-term storage and retrieval of spent nuclear reactor fuel assemblies at a plausible repository depth in granitic rock. Eleven spent fuel assemblies are stored at a depth of 420 m for three to five years, and will then be retrieved. MPBX units are used in the SFT-C to measure both excavation-induced and thermally induced rock displacements. Long-term reliability of extensometers in this hostile environment is essential in order to obtain valid data during the course of this test. Research to date shows conclusively that extensometers of this type continue to function reliably even though subjected to accelerations of 1.8 g; research also implies that they function well though subjected to accelerations in excess of 100 g. MPBX survivability during the first four months of testing at ambient temperatures was about 90 percent

On interrelation of crack resistance characteristics of metal materials under static and dynamic loading conditions

International Nuclear Information System (INIS)

Abramyan, K.G.; Goloveshkin, Yu.V.; Tuzlukova, N.I.

1984-01-01

Home and foreign data on crack resistance characteristics of metal structural materials are generalized and analyzed. Dependence between various parameters of material strength and toughness on the one hand and racck resistance on the other hand is established on the basis of the energy concept of the failure mechanics. Effect of the strain rate on σsub(0.2) and Ksub(Ic) values is evaluated. Quanlitative and quantitative relations obtained permit conducting a complex estimation of materials behaviour during static and dynamic loading operations

The effect of loading rate on pile bearing capacity of saturated sand

NARCIS (Netherlands)

Archeewa, E.

2005-01-01

Pile load tests are commonly used by engineers to determine its bearing capacity. At present, there are three methods of pile load tests: the static, the dynamic and the quasi-static test. The static pile load test is done by applying an axial load on the pile with a long duration. The dynamic and

Dynamics of the aortic arch submitted to a shock loading: Parametric study with fluid-structure models.

Science.gov (United States)

El Baroudi, A; Razafimahery, F; Rakotomanana, L

2012-01-01

This work aims to present some fluid-structure models for analyzing the dynamics of the aorta during a brusque loading. Indeed, various lesions may appear at the aortic arch during car crash or other accident such as brusque falling. Aortic stresses evolution are simulated during the shock at the cross section and along the aorta. One hot question was that if a brusque deceleration can generate tissue tearing, or a shock is necessary to provoke such a damage. Different constitutive laws of blood are then tested whereas the aorta is assumed linear and elastic. The overall shock model is inspired from an experimental jig. We show that the viscosity has strong influence on the stress and parietal moments and forces. The nonlinear viscosity has no significant additional effects for healthy aorta, but modifies the stress and parietal loadings for the stenotic aorta.

Dynamic analysis of double-row self-aligning ball bearings due to applied loads, internal clearance, surface waviness and number of balls

Science.gov (United States)

Zhuo, Yaobin; Zhou, Xiaojun; Yang, Chenlong

2014-11-01

In this paper, a three degrees of freedom (dof) model was established for a double-row self-aligning ball bearing (SABB) system, and was applied to study the dynamic behavior of the system during starting process and constant speed rotating process. A mathematical model was developed concerning stiffness and damping characteristics of the bearing, as well as three-dimensional applied load, rotor centrifugal force, etc. Balls and races were all considered as nonlinear springs, and the contact force between ball and race was calculated based on classic Hertzian elastic contact deformation theory and deformation compatibility theory. The changes of each ball's contact force and loaded angle of each row were taken into account. In order to solve the nonlinear dynamical equilibrium equations of the system, these equations were rewritten as differential equations and the fourth order Runge-Kutta method was used to solve the equations iteratively. In order to verify accuracy of the dynamical model and correctness of the numerical solution method, a kind of SABB-BRF30 was chosen for case studies. The effects of several important governing parameters, such as radial and axial applied loads, normal internal, inner and outer races waviness, and number of balls were investigated. These parametric studies led to a complete characterization of the shaft-bearing system vibration transmission. The research provided a theoretical reference for new type bearing design, shaft-bearing system kinetic analysis, optimal design, etc.

Load responsive hydrodynamic bearing

Science.gov (United States)

Kalsi, Manmohan S.; Somogyi, Dezso; Dietle, Lannie L.

2002-01-01

A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

Load Loss Performance of an Autonomous Self-Excited Induction ...

African Journals Online (AJOL)

This paper presents a dynamic analysis of an autonomous Self-Excited Induction Generator (SEIG) showing dynamic loss of load performance. In stand-alone operation of the SEIG, especially when supplying a low power utility, an interesting performance of the SEIG observed for various power factor loads can be ...

Strain rate dependent deformation and failure behavior of laser welded DP780 steel joint under dynamic tensile loading

International Nuclear Information System (INIS)

Liu, Yang; Dong, Danyang; Wang, Lei; Chu, Xi; Wang, Pengfei; Jin, Mengmeng

2015-01-01

Laser welded DP steel joints are used widely in the automotive industry for weight reduction. Understanding the deformation and fracture behavior of the base metal (BM) and its welded joint (WJ), especially at high strain rates, is critical for the design of vehicle structures. This paper is concerned with the effects of strain rate on the tensile properties, deformation and fracture behavior of the laser welded DP780 steel joint. Quasi-static and dynamic tensile tests were performed on the WJ and BM of the DP780 steel using an electromechanical universal testing machine and a high-speed tensile testing machine over a wide range of strain rate (0.0001–1142 s −1 ). The microstructure change and microhardness distribution of the DP780 steel after laser welding were examined. Digital image correlation (DIC) and high-speed photography were employed for the strain measurement of the DP780 WJ during dynamic tensile tests. The DP780 WJ is a heterogeneous structure with hardening in fusion zone (FZ) and inner heat-affected zone (HAZ), and softening in outer HAZ. The DP780 BM and WJ exhibit positive strain rate dependence on the YS and UTS, which is smaller at lower strain rates and becomes larger with increasing strain rate, while ductility in terms of total elongation (TE) tends to increase under dynamic loading. Laser welding leads to an overall reduction in the ductility of the DP780 steel. However, the WJ exhibits a similar changing trend of the ductility to that of the BM with respect to the strain rate over the whole strain rate range. As for the DP780 WJ, the distance of tensile failure location from the weld centerline decreases with increasing strain rate. The typical ductile failure characteristics of the DP780 BM and WJ do not change with increasing strain rate. DIC measurements reveal that the strain localization starts even before the maximum load is attained in the DP780 WJ and gradual transition from uniform strains to severely localized strains occurs

Strain rate dependent deformation and failure behavior of laser welded DP780 steel joint under dynamic tensile loading

Energy Technology Data Exchange (ETDEWEB)

Liu, Yang, E-mail: liuyang@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Dong, Danyang, E-mail: dongdanyang@mail.neu.edu.cn [College of Science, Northeastern University, Shenyang 110819 (China); Wang, Lei, E-mail: wanglei@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Chu, Xi, E-mail: chuxi.ok@163.com [College of Science, Northeastern University, Shenyang 110819 (China); Wang, Pengfei, E-mail: wpf1963871400@163.com [College of Science, Northeastern University, Shenyang 110819 (China); Jin, Mengmeng, E-mail: 24401878@163.com [College of Science, Northeastern University, Shenyang 110819 (China)

2015-03-11

Laser welded DP steel joints are used widely in the automotive industry for weight reduction. Understanding the deformation and fracture behavior of the base metal (BM) and its welded joint (WJ), especially at high strain rates, is critical for the design of vehicle structures. This paper is concerned with the effects of strain rate on the tensile properties, deformation and fracture behavior of the laser welded DP780 steel joint. Quasi-static and dynamic tensile tests were performed on the WJ and BM of the DP780 steel using an electromechanical universal testing machine and a high-speed tensile testing machine over a wide range of strain rate (0.0001–1142 s{sup −1}). The microstructure change and microhardness distribution of the DP780 steel after laser welding were examined. Digital image correlation (DIC) and high-speed photography were employed for the strain measurement of the DP780 WJ during dynamic tensile tests. The DP780 WJ is a heterogeneous structure with hardening in fusion zone (FZ) and inner heat-affected zone (HAZ), and softening in outer HAZ. The DP780 BM and WJ exhibit positive strain rate dependence on the YS and UTS, which is smaller at lower strain rates and becomes larger with increasing strain rate, while ductility in terms of total elongation (TE) tends to increase under dynamic loading. Laser welding leads to an overall reduction in the ductility of the DP780 steel. However, the WJ exhibits a similar changing trend of the ductility to that of the BM with respect to the strain rate over the whole strain rate range. As for the DP780 WJ, the distance of tensile failure location from the weld centerline decreases with increasing strain rate. The typical ductile failure characteristics of the DP780 BM and WJ do not change with increasing strain rate. DIC measurements reveal that the strain localization starts even before the maximum load is attained in the DP780 WJ and gradual transition from uniform strains to severely localized strains

Identification of Dynamic Loads Based on Second-Order Taylor-Series Expansion Method

Directory of Open Access Journals (Sweden)

Xiaowang Li

2016-01-01

Full Text Available A new method based on the second-order Taylor-series expansion is presented to identify the structural dynamic loads in the time domain. This algorithm expresses the response vectors as Taylor-series approximation and then a series of formulas are deduced. As a result, an explicit discrete equation which associates system response, system characteristic, and input excitation together is set up. In a multi-input-multi-output (MIMO numerical simulation study, sinusoidal excitation and white noise excitation are applied on a cantilever beam, respectively, to illustrate the effectiveness of this algorithm. One also makes a comparison between the new method and conventional state space method. The results show that the proposed method can obtain a more accurate identified force time history whether the responses are polluted by noise or not.

Structural Dynamic Behavior of Wind Turbines

Science.gov (United States)

Thresher, Robert W.; Mirandy, Louis P.; Carne, Thomas G.; Lobitz, Donald W.; James, George H. III

2009-01-01

The structural dynamicist s areas of responsibility require interaction with most other members of the wind turbine project team. These responsibilities are to predict structural loads and deflections that will occur over the lifetime of the machine, ensure favorable dynamic responses through appropriate design and operational procedures, evaluate potential design improvements for their impact on dynamic loads and stability, and correlate load and control test data with design predictions. Load prediction has been a major concern in wind turbine designs to date, and it is perhaps the single most important task faced by the structural dynamics engineer. However, even if we were able to predict all loads perfectly, this in itself would not lead to an economic system. Reduction of dynamic loads, not merely a "design to loads" policy, is required to achieve a cost-effective design. The two processes of load prediction and structural design are highly interactive: loads and deflections must be known before designers and stress analysts can perform structural sizing, which in turn influences the loads through changes in stiffness and mass. Structural design identifies "hot spots" (local areas of high stress) that would benefit most from dynamic load alleviation. Convergence of this cycle leads to a turbine structure that is neither under-designed (which may result in structural failure), nor over-designed (which will lead to excessive weight and cost).

Hard-on-hard lubrication in the artificial hip under dynamic loading conditions.

Directory of Open Access Journals (Sweden)

Robert Sonntag

Full Text Available The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.

Microstructure and Deformation Response of TRIP-Steel Syntactic Foams to Quasi-Static and Dynamic Compressive Loads

Science.gov (United States)

Ehinger, David; Weise, Jörg; Baumeister, Joachim; Funk, Alexander; Krüger, Lutz; Martin, Ulrich

2018-01-01

The implementation of hollow S60HS glass microspheres and Fillite 106 cenospheres in a martensitically transformable AISI 304L stainless steel matrix was realized by means of metal injection molding of feedstock with varying fractions of the filler material. The so-called TRIP-steel syntactic foams were studied with respect to their behavior under quasi-static compression and dynamic impact loading. The interplay between matrix material behavior and foam structure was discussed in relation to the findings of micro-structural investigations, electron back scatter diffraction EBSD phase analyses and magnetic measurements. During processing, the cenospheres remained relatively stable retaining their shape while the glass microspheres underwent disintegration associated with the formation of pre-cracked irregular inclusions. Consequently, the AISI 304L/Fillite 106 syntactic foams exhibited a higher compression stress level and energy absorption capability as compared to the S60HS-containing variants. The α′ -martensite kinetic of the steel matrix was significantly influenced by material composition, strain rate and arising deformation temperature. The highest ferromagnetic α′-martensite phase fraction was detected for the AISI 304L/S60HS batches and the lowest for the TRIP-steel bulk material. Quasi-adiabatic sample heating, a gradual decrease in strain rate and an enhanced degree of damage controlled the mechanical deformation response of the studied syntactic foams under dynamic impact loading. PMID:29695107

Coupled Fluid-Solid Interaction Under Shock Wave Loading: Part II - Dynamic Interfaces

Energy Technology Data Exchange (ETDEWEB)

Tipton, David Gregory [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Christon, Mark Allen [CTO Offce, Dassault Systµemes SIMULIA, Providence, RI (United States); Ingber, Marc Stuart [Univ. of New Mexico, Albuquerque, NM (United States). Department of Mechanical Engineering

2009-07-01

This article is the second of two that consider the treatment of fluid-solid interaction problems where the solid experiences wave loading and large bulk Lagrangian displacements. In part-I, we presented the formulation for the edge-based unstructured-grid Euler solver in the context of a discontinuous- Galerkin framework with the extensions used to treat internal fluid-solid interfaces. A super-sampled L² projection was used to construct level-set data from the Lagrangian interface, and a narrow-band approach was used to identify and construct appropriate ghost data and boundary conditions at the fluid-solid interface. A series of benchmark problems were used to verify the treatment of the fluid-solid interface conditions with a static interface position. In this paper, we consider the treatment of dynamic interfaces and the associated large bulk Lagrangian displacements of the solid.We present the coupled dynamic fluid-solid system, and develop an explicit, monolithic treatment of the fully-coupled system. The conditions associated with moving interfaces and their implementation are discussed. A comparison of moving vs. fixed reference frames is used to verify the dynamic interface treatment. Lastly, a series of two and and three-dimensional projectile and shock-body interaction calculations are presented. Ultimately, the use of the Lagrangian interface position and a super-sampled projection for fast level-set construction, the narrow-band extraction of ghost data, and monolithic explicit solution algorithm has proved to be a computationally efficient means for treating shock induced fluid-solid interaction problems.

Analytical Study on Dynamic Response of Deep Foundation Pit Support Structure under the Action of Subway Train Vibration Load: A Case Study of Deep Foundation Pit of the New Museum Near Metro Line 2 in Chengdu, China

Directory of Open Access Journals (Sweden)

Zhu Dapeng

2015-01-01

Full Text Available Presently, foundation pit support structures are generally regarded as the temporary structures and the impact of vibration loads is often overlooked. As opposed to static and seismic loads, the vibration loads of subway trains are a type of cyclic load with a relatively long duration of action and a definite cycle; it is of great importance for the design of foundation pit support structures to correctly evaluate the impact of subway train vibrations on deep foundation pit and support works. In this paper, a dynamic three-dimensional numerical model is built that considers the vibration load of subway trains on the basis of the static numerical model for deep foundation pit support structures and simplified train loads to study the impact of train vibrations on deep foundation pit and permanent support structures. Studies have shown that the dynamic response of surface displacement mainly occurs in the early period of dynamic load, the vibration load of subway trains has little impact on ground subsidence, the support pile structure is in an elastic state during dynamic response under the action of subway train vibrations, and the action of train vibration loads is inimical to the safety of foundation pit support structures and should be closely studied.

Experiment and simulation study on unidirectional carbon fiber composite component under dynamic 3 point bending loading

Energy Technology Data Exchange (ETDEWEB)

Zhou, Guowei; Sun, Qingping; Zeng, Danielle; Li, Dayong; Su, Xuming

2018-04-10

In current work, unidirectional (UD) carbon fiber composite hatsection component with two different layups are studied under dynamic 3 point bending loading. The experiments are performed at various impact velocities, and the effects of impactor velocity and layup on acceleration histories are compared. A macro model is established with LS-Dyna for more detailed study. The simulation results show that the delamination plays an important role during dynamic 3 point bending test. Based on the analysis with high speed camera, the sidewall of hatsection shows significant buckling rather than failure. Without considering the delamination, current material model cannot capture the post failure phenomenon correctly. The sidewall delamination is modeled by assumption of larger failure strain together with slim parameters, and the simulation results of different impact velocities and layups match the experimental results reasonable well.

The dynamic response of the containment of the Qinshan nuclear power plant to the aircraft impact loading

International Nuclear Information System (INIS)

Zuo Jiahong; Han Liangbi; Xia Zufeng

1991-08-01

The structural response of the containment of the Qinshan Nuclear Power Plant under the standard-load-function to aircraft impact has been analyzed by using the ADINA code considering an axisymmetric continuum model, which is assumed a mixed-model for the steel-concrete mixture. It consists of 179 four-node isoparametric concrete elements and 118 steel elements. In order to obtain optimum results, the nonlinear behavior of materials and structures, dynamic modes of failure and damage have been considered in the numerical solution. The coordinate system is based on the total Lagrangian formulation. The F.E. system has been solved using an incremental interactions (BFGS method) with 600 steps totally. A discussion of the overall behavior of the containment for the aircraft impact loading, especially the nonlinear behavior of the local impacted area is presented

Dynamic load balance scheme for the DSMC algorithm

International Nuclear Information System (INIS)

Li, Jin; Geng, Xiangren; Jiang, Dingwu; Chen, Jianqiang

2014-01-01

The direct simulation Monte Carlo (DSMC) algorithm, devised by Bird, has been used over a wide range of various rarified flow problems in the past 40 years. While the DSMC is suitable for the parallel implementation on powerful multi-processor architecture, it also introduces a large load imbalance across the processor array, even for small examples. The load imposed on a processor by a DSMC calculation is determined to a large extent by the total of simulator particles upon it. Since most flows are impulsively started with initial distribution of particles which is surely quite different from the steady state, the total of simulator particles will change dramatically. The load balance based upon an initial distribution of particles will break down as the steady state of flow is reached. The load imbalance and huge computational cost of DSMC has limited its application to rarefied or simple transitional flows. In this paper, by taking advantage of METIS, a software for partitioning unstructured graphs, and taking the total of simulator particles in each cell as a weight information, the repartitioning based upon the principle that each processor handles approximately the equal total of simulator particles has been achieved. The computation must pause several times to renew the total of simulator particles in each processor and repartition the whole domain again. Thus the load balance across the processors array holds in the duration of computation. The parallel efficiency can be improved effectively. The benchmark solution of a cylinder submerged in hypersonic flow has been simulated numerically. Besides, hypersonic flow past around a complex wing-body configuration has also been simulated. The results have displayed that, for both of cases, the computational time can be reduced by about 50%

Research Based on AMESim of Electro-hydraulic Servo Loading System

Science.gov (United States)

Li, Jinlong; Hu, Zhiyong

2017-09-01

Electro-hydraulic servo loading system is a subject studied by many scholars in the field of simulation and control at home and abroad. The electro-hydraulic servo loading system is a loading device simulation of stress objects by aerodynamic moment and other force in the process of movement, its function is all kinds of gas in the lab condition to analyze stress under dynamic load of objects. The purpose of this paper is the design of AMESim electro-hydraulic servo system, PID control technology is used to configure the parameters of the control system, complete the loading process under different conditions, the optimal design parameters, optimization of dynamic performance of the loading system.

LOADING OF MECHANICAL TRANSMISSION OF TROLLEYBUS TRACTION DRIVING GEAR

Directory of Open Access Journals (Sweden)

A. I. Safonov

2009-01-01

Full Text Available The paper analyzes factors that determine dynamic loads of mechanical transmission of trolleybus traction driving gear. The paper proposes a methodology for determination of calculative moments of loading transmission elements. Results of the research are analyzed and recommendations on  dynamic reduction of trolleybus transmission are given in the paper. 

Validation of the dynamic wake meander model for loads and power production in the Egmond aan Zee wind farm

DEFF Research Database (Denmark)

Larsen, Torben J.; Aagaard Madsen, Helge; Larsen, Gunner Chr.

2013-01-01

This paper investigates wake effects on load and power production by using the dynamic wake meander (DWM) model implemented in the aeroelastic code HAWC2. The instationary wind farm flow characteristics are modeled by treating the wind turbine wakes as passive tracers transported downstream using...... a meandering process driven by the low frequent cross-wind turbulence components. The model complex is validated by comparing simulated and measured loads for the Dutch Egmond aan Zee wind farm consisting of 36 Vestas V90 turbine located outside the coast of the Netherlands. Loads and production are compared...... for two distinct wind directions—a free wind situation from the dominating southwest and a full wake situation from northwest, where the observed turbine is operating in wake from five turbines in a row with 7D spacing. The measurements have a very high quality, allowing for detailed comparison of both...

Dynamic deformation and failure characteristic of rock foundation by means of effect of cyclic shear loading

International Nuclear Information System (INIS)

Fujiwara, Yoshikazu; Hibino, Satoshi; Kanagawa, Tadashi; Komada, Hiroya; Nakagawa, Kameichiro

1984-01-01

The main structures of nuclear power plants are built on hard and soft rocks. The rock-dynamic properties used for investigating the stability of the structures have been determined so far by laboratory tests for soft rocks. In hard rocks, however, joints and cracks exist, and the test including these effects is not able to be performed in laboratories at present. Therefore, a dynamic repeating shearing test equipment to be used under the condition including the joints and cracks of actual ground has been made for a base rock of tuff breccia. In this paper, the test results are reported as follows. The geological features of the testing site and the arrangement of tested rocks, the preparation for tests, test equipment, loading method, measuring method, analysis, and the result and the examination. The results of dynamic deformation and failure characteristics were as follows: (1) the dynamic shear-elasticity-modulus Gd of the base rock showed greater values as the normal stress increased, while Gd decreased and showed the strain dependence as the dynamic shear strain amplitude γ increased; (2) the relationship between Gd and γ was well represented with the equation proposed by Hardin-Drnevich; (3) damping ratio increased as γ increased, and decreased as normal stress increased; (4) When a specimen was about to break, γ suddenly increased, and the dynamic shear strain amplitude at yield point was in the range of approximately (3.4 to 4.1) x 10 -3 . (Wakatsuki, Y.)

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

Science.gov (United States)

Yang, Shu; Han, Shou-Hong; Lu, Zhen-Hua

2014-01-01

It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances. PMID:25126606

Dynamic response and optimal design of curved metallic sandwich panels under blast loading.

Science.gov (United States)

Qi, Chang; Yang, Shu; Yang, Li-Jun; Han, Shou-Hong; Lu, Zhen-Hua

2014-01-01

It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a "soft" outer face and a "hard" inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

Directory of Open Access Journals (Sweden)

Chang Qi

2014-01-01

Full Text Available It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

Creatine Loading, Resistance Exercise Performance, and Muscle Mechanics.

Science.gov (United States)

Stevenson, Scott W.; Dudley, Gary A.

2001-01-01

Examined whether creatine (CR) monohydrate loading would alter resistance exercise performance, isometric strength, or in vivo contractile properties of the quadriceps femoris muscle compared with placebo loading in resistance-trained athletes. Overall, CR loading did not provide an ergogenic benefit for the unilateral dynamic knee extension…

Considering dynamic friction and proper structural response in hydraulic load cases for realistic piping design

International Nuclear Information System (INIS)

Diesselhorst, T.; Diatschuk, P.; Schnellhammer, W.

2005-01-01

Concerning the design for hydraulic load cases there is always a sequence of fluid- and structural dynamic calculations, where the structural vibrations are induced by the time depending fluid forces. Therefore, in order to prevent excessive structural reactions, it is most important to avoid conservative fluid dynamic results. That refers to the maximum value of the pressure surge as well as to the damping of pressure oscillations. This is especially relevant in case of fluid-structure resonance. To meet these requirements the effect of dynamic wall friction was implemented in our fluid dynamic code. Thus, a more realistic damping behavior of the fluid forces was achieved. In the structural analysis code the damping of the pipe structure could be more accurate adapted to the real conditions. Additionally the local damping by viscous damper was included in the model. At supports now non-linear behavior like clearances can be simulated. The possibility of coupled calculation was installed to consider the effect of fluid structure interaction. The programmed effects are validated against measurement results from power plant systems. The favorable effects of the program improvements are demonstrated by typical examples. These included the realistic damping of pressure oscillations as well as a case of fluid-structure resonance. Additionally the effectiveness of the improved models of piping supports is demonstrated. (authors)

Delay-active damage versus non-local enhancement for anisotropic damage dynamics computations with alternated loading

International Nuclear Information System (INIS)

Desmorat, R.; Chambart, M.; Gatuingt, F.; Guilbaud, D.

2010-01-01

Anisotropic damage thermodynamics framework allows to model the concrete-like materials behavior and in particular their dissymmetric tension/compression response. To deal with dynamics applications such as impact, it is furthermore necessary to take into account the strain rate effect observed experimentally. This is done in the present work by means of anisotropic visco-damage, by introducing a material strain rate effect in the cases of positive hydrostatic stresses only. The proposed delay-damage law assumes no viscous effect in compression as the consideration of inertia effects proves sufficient to model the apparent material strength increase. High-rate dynamics applications imply to deal with wave propagation and reflection which can generate alternated loading in the impacted structure. In order to do so, the key concept of active damage is defined and introduced within both the damage criterion and the delay-damage evolution law. At the structural level, strain localization often leads to spurious mesh dependency. Three-dimensional Finite Element computations of dynamic tensile tests by spalling are presented, with visco-damage and either without or with non-local enhancement. Delay-damage, as introduced, regularizes the solution in fast dynamics. The location of the macro-crack initiated is found influenced by non-local regularization. The strain rate range in which each enhancement, delay-damage or non-local enhancement, has a regularizing effect is studied. (authors)

Dynamic Stresses in the LHC TCDS Diluter from 7 TeV Beam Loading

CERN Document Server

Goddard, B; Presland, A; Weterings, W

2006-01-01

In the event of an unsynchronised beam abort, the MSD extraction septum of the LHC beam dumping system is protected from damage by the TCDS diluter. The simultaneous constraints of obtaining sufficient beam dilution while ensuring the survival of the TCDS make the design difficult, with high thermally induced dynamic stresses occurring in the material needed to attenuate the particle showers induced by the primary beam impact. In this paper, full 3D simulations are described where the worst-case beam loading has been used to generate the local temperature rise and to follow the resulting time evolution of the mechanical stresses. The results and the accompanying design changes for the TCDS, to provide an adequate performance margin, are detailed.

Working-memory load and temporal myopia in dynamic decision making.

Science.gov (United States)

Worthy, Darrell A; Otto, A Ross; Maddox, W Todd

2012-11-01

We examined the role of working memory (WM) in dynamic decision making by having participants perform decision-making tasks under single-task or dual-task conditions. In 2 experiments participants performed dynamic decision-making tasks in which they chose 1 of 2 options on each trial. The decreasing option always gave a larger immediate reward but caused future rewards for both options to decrease. The increasing option always gave a smaller immediate reward but caused future rewards for both options to increase. In each experiment we manipulated the reward structure such that the decreasing option was the optimal choice in 1 condition and the increasing option was the optimal choice in the other condition. Behavioral results indicated that dual-task participants selected the immediately rewarding decreasing option more often, and single-task participants selected the increasing option more often, regardless of which option was optimal. Thus, dual-task participants performed worse on 1 type of task but better on the other type. Modeling results showed that single-task participants' data were most often best fit by a win-stay, lose-shift (WSLS) rule-based model that tracked differences across trials, and dual-task participants' data were most often best fit by a Softmax reinforcement learning model that tracked recency-weighted average rewards for each option. This suggests that manipulating WM load affects the degree to which participants focus on the immediate versus delayed consequences of their actions and whether they employ a rule-based WSLS strategy, but it does not necessarily affect how well people weigh the immediate versus delayed benefits when determining the long-term utility of each option.

The Statistical Properties of Host Load

Directory of Open Access Journals (Sweden)

Peter A. Dinda

1999-01-01

Full Text Available Understanding how host load changes over time is instrumental in predicting the execution time of tasks or jobs, such as in dynamic load balancing and distributed soft real‐time systems. To improve this understanding, we collected week‐long, 1 Hz resolution traces of the Digital Unix 5 second exponential load average on over 35 different machines including production and research cluster machines, compute servers, and desktop workstations. Separate sets of traces were collected at two different times of the year. The traces capture all of the dynamic load information available to user‐level programs on these machines. We present a detailed statistical analysis of these traces here, including summary statistics, distributions, and time series analysis results. Two significant new results are that load is self‐similar and that it displays epochal behavior. All of the traces exhibit a high degree of self‐similarity with Hurst parameters ranging from 0.73 to 0.99, strongly biased toward the top of that range. The traces also display epochal behavior in that the local frequency content of the load signal remains quite stable for long periods of time (150–450 s mean and changes abruptly at epoch boundaries. Despite these complex behaviors, we have found that relatively simple linear models are sufficient for short‐range host load prediction.

Effects of Cascaded Voltage Collapse and Protection of Many Induction Machine Loads upon Load Characteristics Viewed from Bulk Transmission System

Science.gov (United States)

Kumano, Teruhisa

As known well, two of the fundamental processes which give rise to voltage collapse in power systems are the on load tap changers of transformers and dynamic characteristics of loads such as induction machines. It has been well established that, comparing among these two, the former makes slower collapse while the latter makes faster. However, in realistic situations, the load level of each induction machine is not uniform and it is well expected that only a part of loads collapses first, followed by collapse process of each load which did not go into instability during the preceding collapses. In such situations the over all equivalent collapse behavior viewed from bulk transmission level becomes somewhat different from the simple collapse driven by one aggregated induction machine. This paper studies the process of cascaded voltage collapse among many induction machines by time simulation, where load distribution on a feeder line is modeled by several hundreds of induction machines and static impedance loads. It is shown that in some cases voltage collapse really cascades among induction machines, where the macroscopic load dynamics viewed from upper voltage level makes slower collapse than expected by the aggregated load model. Also shown is the effects of machine protection of induction machines, which also makes slower collapse.

Gender dimorphic ACL strain in response to combined dynamic 3D knee joint loading: implications for ACL injury risk.

Science.gov (United States)

Mizuno, Kiyonori; Andrish, Jack T; van den Bogert, Antonie J; McLean, Scott G

2009-12-01

While gender-based differences in knee joint anatomies/laxities are well documented, the potential for them to precipitate gender-dimorphic ACL loading and resultant injury risk has not been considered. To this end, we generated gender-specific models of ACL strain as a function of any six degrees of freedom (6DOF) knee joint load state via a combined cadaveric and analytical approach. Continuously varying joint forces and torques were applied to five male and five female cadaveric specimens and recorded along with synchronous knee flexion and ACL strain data. All data (approximately 10,000 samples) were submitted to specimen-specific regression analyses, affording ACL strain predictions as a function of the combined 6 DOF knee loads. Following individual model verifications, generalized gender-specific models were generated and subjected to 6 DOF external load scenarios consistent with both a clinical examination and a dynamic sports maneuver. The ensuing model-based strain predictions were subsequently examined for gender-based discrepancies. Male and female specimen-specific models predicted ACL strain within 0.51%+/-0.10% and 0.52%+/-0.07% of the measured data respectively, and explained more than 75% of the associated variance in each case. Predicted female ACL strains were also significantly larger than respective male values for both simulated 6 DOF load scenarios. Outcomes suggest that the female ACL will rupture in response to comparatively smaller external load applications. Future work must address the underlying anatomical/laxity contributions to knee joint mechanical and resultant ACL loading, ultimately affording prevention strategies that may cater to individual joint vulnerabilities.

Assessment of Susceptibility to Liquefaction of Saturated Road Embankment Subjected to Dynamic Loads

Science.gov (United States)

Borowiec, Anna; Maciejewski, Krzysztof

2014-03-01

Liquefaction has always been intensely studied in parts of the world where earthquakes occur. However, the seismic activity is not the only possible cause of this phenomenon. It may in fact be triggered by some human activities, such as constructing and mining or by rail and road transport. In the paper a road embankment built across a shallow water reservoir is analyzed in terms of susceptibility to liquefaction. Two types of dynamic loadings are considered: first corresponding to an operation of a vibratory roller and second to an earthquake. In order to evaluate a susceptibility of soil to liquefaction, a factor of safety against triggering of liquefaction is used (FSTriggering). It is defined as a ratio of vertical effective stresses to the shear stresses both varying with time. For the structure considered both stresses are obtained using finite element method program, here Plaxis 2D. The plastic behavior of the cohesionless soils is modeled by means of Hardening Soil (HS) constitutive relationship, implemented in Plaxis software. As the stress tensor varies with time during dynamic excitation, the FSTriggering has to be calculated for some particular moment of time when liquefaction is most likely to occur. For the purposes of this paper it is named a critical time and established for reference point at which the pore pressures were traced in time. As a result a factor of safety distribution throughout embankment is generated. For the modeled structure, cyclic point loads (i.e., vibrating roller) present higher risk than earthquake of magnitude 5.4. Explanation why considered structure is less susceptible to earthquake than typical dam could lay in stabilizing and damping influence of water, acting here on both sides of the slope. Analogical procedure is applied to assess liquefaction susceptibility of the road embankment considered but under earthquake excitation. Only the higher water table is considered as it is the most unfavorable. Additionally the

Short-Term Load Forecasting-Based Automatic Distribution Network Reconfiguration

Energy Technology Data Exchange (ETDEWEB)

Jiang, Huaiguang [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Ding, Fei [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhang, Yingchen [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-08-23

In a traditional dynamic network reconfiguration study, the optimal topology is determined at every scheduled time point by using the real load data measured at that time. The development of the load forecasting technique can provide an accurate prediction of the load power that will happen in a future time and provide more information about load changes. With the inclusion of load forecasting, the optimal topology can be determined based on the predicted load conditions during a longer time period instead of using a snapshot of the load at the time when the reconfiguration happens; thus, the distribution system operator can use this information to better operate the system reconfiguration and achieve optimal solutions. This paper proposes a short-term load forecasting approach to automatically reconfigure distribution systems in a dynamic and pre-event manner. Specifically, a short-term and high-resolution distribution system load forecasting approach is proposed with a forecaster based on support vector regression and parallel parameters optimization. The network reconfiguration problem is solved by using the forecasted load continuously to determine the optimal network topology with the minimum amount of loss at the future time. The simulation results validate and evaluate the proposed approach.

Recent research and applications of numerical simulation for dynamic response of long-span bridges subjected to multiple loads.

Science.gov (United States)

Chen, Zhiwei; Chen, Bo

2014-01-01

Many long-span bridges have been built throughout the world in recent years but they are often subject to multiple types of dynamic loads, especially those located in wind-prone regions and carrying both trains and road vehicles. To ensure the safety and functionality of these bridges, dynamic responses of long-span bridges are often required for bridge assessment. Given that there are several limitations for the assessment based on field measurement of dynamic responses, a promising approach is based on numerical simulation technologies. This paper provides a detailed review of key issues involved in dynamic response analysis of long-span multiload bridges based on numerical simulation technologies, including dynamic interactions between running trains and bridge, between running road vehicles and bridge, and between wind and bridge, and in the wind-vehicle-bridge coupled system. Then a comprehensive review is conducted for engineering applications of newly developed numerical simulation technologies to safety assessment of long-span bridges, such as assessment of fatigue damage and assessment under extreme events. Finally, the existing problems and promising research efforts for the numerical simulation technologies and their applications to assessment of long-span multiload bridges are explored.

Regulation of the Dynamic Live Load Factor for Calculation of Bridge Structures on High-Speed Railway Mainlines

Science.gov (United States)

Dyachenko, Leonid K.; Benin, Andrey V.

2017-06-01

When the high-speed railway traffic is being organized, it becomes necessary to elaborate bridge design standards for high-speed railways (HSR). Methodology of studying the issues of HSR bridge design is based on the comprehensive analysis of domestic research as well as international experience in design, construction and operation of high-speed railways. Serious requirements are imposed on the HSR artificial structures, which raise a number of scientific tasks associated mainly with the issues of the dynamic interaction of the rolling stock and the bridge elements. To ensure safety of traffic and reliability of bridges during the whole period of operation one needs to resolve the dynamic problems of various types of high-speed trains moving along the structures. The article analyses dependences of the magnitude of inertial response on the external stress parameters and proposes a simplified method of determination of the dynamic live load factor caused by the passage of high-speed trains. The usefulness of the given research arises from the reduction of complexity of the complicated dynamic calculations needed to describe a high-speed train travelling along the artificial structures.

Regulation of the Dynamic Live Load Factor for Calculation of Bridge Structures on High-Speed Railway Mainlines

Directory of Open Access Journals (Sweden)

Dyachenko Leonid K.

2017-06-01

Full Text Available When the high-speed railway traffic is being organized, it becomes necessary to elaborate bridge design standards for high-speed railways (HSR. Methodology of studying the issues of HSR bridge design is based on the comprehensive analysis of domestic research as well as international experience in design, construction and operation of high-speed railways. Serious requirements are imposed on the HSR artificial structures, which raise a number of scientific tasks associated mainly with the issues of the dynamic interaction of the rolling stock and the bridge elements. To ensure safety of traffic and reliability of bridges during the whole period of operation one needs to resolve the dynamic problems of various types of high-speed trains moving along the structures. The article analyses dependences of the magnitude of inertial response on the external stress parameters and proposes a simplified method of determination of the dynamic live load factor caused by the passage of high-speed trains. The usefulness of the given research arises from the reduction of complexity of the complicated dynamic calculations needed to describe a high-speed train travelling along the artificial structures.

A novel grooming algorithm with the adaptive weight and load balancing for dynamic holding-time-aware traffic in optical networks

Science.gov (United States)

Xu, Zhanqi; Huang, Jiangjiang; Zhou, Zhiqiang; Ding, Zhe; Ma, Tao; Wang, Junping

2013-10-01

To maximize the resource utilization of optical networks, the dynamic traffic grooming, which could efficiently multiplex many low-speed services arriving dynamically onto high-capacity optical channels, has been studied extensively and used widely. However, the link weights in the existing research works can be improved since they do not adapt to the network status and load well. By exploiting the information on the holding times of the preexisting and new lightpaths, and the requested bandwidth of a user service, this paper proposes a grooming algorithm using Adaptively Weighted Links for Holding-Time-Aware (HTA) (abbreviated as AWL-HTA) traffic, especially in the setup process of new lightpath(s). Therefore, the proposed algorithm can not only establish a lightpath that uses network resource efficiently, but also achieve load balancing. In this paper, the key issues on the link weight assignment and procedure within the AWL-HTA are addressed in detail. Comprehensive simulation and experimental results show that the proposed algorithm has a much lower blocking ratio and latency than other existing algorithms.

Research on the Transient Characteristics of Microgrid with Pulsed Load

Directory of Open Access Journals (Sweden)

Jianke Li

2015-01-01

Full Text Available Unlike traditional load, pulsed load typically features small average power and large peak power. In this paper, the mathematic models of microgrid consisting of synchronous generator and pulsed load are established. Average Magnitude Difference Compensate Function (AMDCF is proposed to calculate the frequency of synchronous generator, and, based on AMDCF, relative deviation rate (RDR which characterizes the impact of pulsed load on the AC side of grid is firstly defined and this paper describes calculation process in detail. Insulated Gate Bipolar Transistor (IGBT is used as DC switch to control the on/off state of resistive load for simulating pulsed load, the period and duty-cycle of the pulsed load are simulated by setting the gate signal of IGBT, and the peak power of the pulsed load is simulated by setting the resistance. The system dynamic characteristics under pulsed load are analyzed in detail, and the influence of duty-cycle, period, peak power, and filter capacitance of the pulsed load on system dynamic indicators is studied and validated experimentally.

NUMERICAL SIMULATION OF YIELDING SUPPORTS IN THE SHAPE OF ANNULAR TUBES UNDER STATIC AND SHORT-TERM DYNAMIC LOADING

Directory of Open Access Journals (Sweden)

Oleg G. Kumpyak

2017-12-01

Full Text Available Occurrence of extreme man-made impacts on buildings and structures has become frequent lately as a consequence of condensed explosives or explosive combustion of gas- vapor or air-fuel mixtures. Such accidents involve large human and economic losses, and their prevention methods are not always effective and reasonable. The given research aims at studying the way of enhancing explosion safety of building structures by means of yielding supports. The paper presents results of numerical studies (finite element, 3D nonlinear of strength and deformability of yielding supports in the shape of annular tubes under static and short-term dynamic loading. The degree of influence of yielding supports was assessed taking into account three peculiar stages of deformation: elastic; elasto-plastic; elasto-plastic with hardening. The methodology for numerical studies performance was described. It was established that rigidity of yielding supports influences significantly their stress-strain state. The research determined that with increase of deformable elements rigidity dependency between load and deformation of yielding supports in elastic and plastic stages have linear character. Significant reduction of dynamic response and increase of deformation time of yielding supports was observed by increasing the plastic component. Therefore it allows assuming on possibility of their application as supporting units in reinforced concrete constructions

Lower head integrity under steam explosion loads

Energy Technology Data Exchange (ETDEWEB)

Theofanous, T.G.; Yuen, W.W.; Angelini, S.; Freeman, K.; Chen, X.; Salmassi, T. [Center for Risk Studies and Safety, Univ. of California, Santa Barbara, CA (United States); Sienicki, J.J.

1998-01-01

Lower head integrity under steam explosion loads in an AP600-like reactor design is considered. The assessment is the second part of an evaluation of the in-vessel retention idea as a severe accident management concept, the first part (DOE/ID-10460) dealing with thermal loads. The assessment is conducted in terms of the Risk Oriented Accident Analysis Methodology (ROAAM), and includes the comprehensive evaluation of all relevant severe accident scenarios, melt conditions and timing of release from the core region, fully 3D mixing and explosion wave dynamics, and lower head fragility under local, dynamic loading. All of these factors and brought together in a ROAAM Probabilistic Framework to evaluate failure likelihood. The conclusion is that failure is `physically unreasonable`. (author)

Dynamic changes in glucose metabolism of living rat brain slices induced by hypoxia and neurotoxic chemical-loading revealed by positron autoradiography

International Nuclear Information System (INIS)

Omata, N.; Fujibayashi, Y.; Waki, A.; Sadato, N.; Yano, R.; Yoshimoto, M.; Yonekura, Y.; Murata, T.; Yoshida, S.

1999-01-01

Fresh rat brain slices were incubated with 2-deoxy-2-[ 18 F]-fluoro-D-glucose ([ 18 F]FDG) in oxygenated Krebs-Ringer solution at 36 degree C, and serial two-dimensional time-resolved images of [ 18 F]FDG uptake were obtained from these specimens on imaging plates. The fractional rate constant (= k3*) of [ 18 F]FDG proportional to the cerebral glucose metabolic rate (CMRglc) was evaluated by applying the Gjedde-Patlak graphical method to the image data. With hypoxia loading (oxygen deprivation) or glucose metabolism inhibitors acting on oxidative phosphorylation, the k3* value increased dramatically suggesting enhanced glycolysis. After relieving hypoxia ≤10-min, the k3* value returned to the pre-loading level. In contrast, with ≥20-min hypoxia only partial or no recovery was observed, indicating that irreversible neuronal damage had been induced. However, after loading with tetrodotoxin (TTX), the k3* value also decreased but returned to the pre-loading level even after 70-min TTX-loading, reflecting a transient inhibition of neuronal activity. This technique provides a new means of quantifying dynamic changes in the regional CMRglc in living brain slices in response to various interventions such as hypoxia and neurotoxic chemical-loading as well as determining the viability and prognosis of brain tissues. (author)

Testing for time-varying loadings in dynamic factor models

DEFF Research Database (Denmark)

Mikkelsen, Jakob Guldbæk

Abstract: In this paper we develop a test for time-varying factor loadings in factor models. The test is simple to compute and is constructed from estimated factors and residuals using the principal components estimator. The hypothesis is tested by regressing the squared residuals on the squared...... there is evidence of time-varying loadings on the risk factors underlying portfolio returns for around 80% of the portfolios....

Dynamic Response to Pedestrian Loads with Statistical Frequency Distribution

DEFF Research Database (Denmark)

Krenk, Steen

2012-01-01

on the magnitude of the resulting response. A frequency representation of vertical pedestrian load is developed, and a compact explicit formula is developed for the magnitude of the resulting response, in terms of the damping ratio of the structure, the bandwidth of the pedestrian load, and the mean footfall...... frequency. The accuracy of the formula is verified by a statistical moment analysis using the Lyapunov equations....

Dynamic load in suppression pool during BWR main steam safety relief valve actuation

International Nuclear Information System (INIS)

Tsukada, Hiroshi; Yamaguchi, Hirokatsu; Morita, Terumichi

1979-01-01

BWRs are so designed that the exhaust steam from main steam safety relief valves is led to pressure suppression pools, and the steam is condensed in pool water, but at this time, dynamic load seems to arise in the pool water. In Tokai No. 2 Power Station, a Mark-2 containment vessel was adopted to improve the reliability as much as possible and to obtain the design with margin. In this report, the result of actual machine test in Tokai No. 2 Power Station and the method of reducing the load are described. When a relief valve works, the discharge of water in exhaust pipes into a suppression pool, the exhaust of air in exhaust pipes and repeated expansion and contraction of bubbles in pool water, and the exhaust of steam and condensation occur. As for the construction of the suppression pool in Tokai No. 2 Power Station, cross-shaped quencher and the structure with jet deflector were installed. The test plan and the test result with an actual machine are reported. The soundness of the Mark-2 containment vessel and the structures in the pool was proved. The differential pressure acting on the structures was negligibly small. The measured pulsating pressure was in the range from 0.84 to -0.39 kg/cm 2 . (Kako, I.)

Comparison of particle swarm optimization and dynamic programming for large scale hydro unit load dispatch

International Nuclear Information System (INIS)

Cheng Chuntian; Liao Shengli; Tang Zitian; Zhao Mingyan

2009-01-01

Dynamic programming (DP) is one of classic and sophisticated optimization methods that have successfully been applied to solve the problem of hydro unit load dispatch (HULD). However, DP will be faced with the curse of dimensionality with the increase of unit number and installed generating capacity of hydropower station. With the appearance of the huge hydropower station similar to the Three George with 26 generators of 700 MW, it is hard to apply the DP to large scale HULD problem. It is crucial to seek for other optimization techniques in order to improve the operation quality and efficiency. Different with the most of literature about power generation scheduling that focused on the comparisons of novel PSO algorithms with other techniques, the paper will pay emphasis on comparison study of PSO with DP based on a case hydropower station. The objective of study is to seek for an effective and feasible method for the large scale of hydropower station of the current and future in China. This paper first compares the performance of PSO and DP using a sample load curve of the Wujiangdu hydropower plant located in the upper stream of the Yangtze River in China and contained five units with the installed capacity of 1250 MW. Next, the effect of different load interval and unit number on the optimal results and efficiency of two methods has also been implemented. The comparison results show that the PSO is feasible for HULD. Furthermore, we simulated the effect of the magnitude of unit number and load capacity on the optimal results and cost time. The simulation comparisons show that PSO has a great advantage over DP in the efficiency and will be one of effective methods for HULD problem of huge hydropower stations.

Comparison of particle swarm optimization and dynamic programming for large scale hydro unit load dispatch

Energy Technology Data Exchange (ETDEWEB)

Cheng Chuntian, E-mail: ctcheng@dlut.edu.c [Department of Civil and Hydraulic Engineering, Dalian University of Technology, 116024 Dalian (China); Liao Shengli; Tang Zitian [Department of Civil and Hydraulic Engineering, Dalian University of Technology, 116024 Dalian (China); Zhao Mingyan [Department of Environmental Science and Engineering, Tsinghua University, 100084 Beijing (China)

2009-12-15

Dynamic programming (DP) is one of classic and sophisticated optimization methods that have successfully been applied to solve the problem of hydro unit load dispatch (HULD). However, DP will be faced with the curse of dimensionality with the increase of unit number and installed generating capacity of hydropower station. With the appearance of the huge hydropower station similar to the Three George with 26 generators of 700 MW, it is hard to apply the DP to large scale HULD problem. It is crucial to seek for other optimization techniques in order to improve the operation quality and efficiency. Different with the most of literature about power generation scheduling that focused on the comparisons of novel PSO algorithms with other techniques, the paper will pay emphasis on comparison study of PSO with DP based on a case hydropower station. The objective of study is to seek for an effective and feasible method for the large scale of hydropower station of the current and future in China. This paper first compares the performance of PSO and DP using a sample load curve of the Wujiangdu hydropower plant located in the upper stream of the Yangtze River in China and contained five units with the installed capacity of 1250 MW. Next, the effect of different load interval and unit number on the optimal results and efficiency of two methods has also been implemented. The comparison results show that the PSO is feasible for HULD. Furthermore, we simulated the effect of the magnitude of unit number and load capacity on the optimal results and cost time. The simulation comparisons show that PSO has a great advantage over DP in the efficiency and will be one of effective methods for HULD problem of huge hydropower stations.

Comparison of particle swarm optimization and dynamic programming for large scale hydro unit load dispatch

Energy Technology Data Exchange (ETDEWEB)

Chun-tian Cheng; Sheng-li Liao; Zi-Tian Tang [Dept. of Civil and Hydraulic Engineering, Dalian Univ. of Technology, 116024 Dalian (China); Ming-yan Zhao [Dept. of Environmental Science and Engineering, Tsinghua Univ., 100084 Beijing (China)

2009-12-15

Dynamic programming (DP) is one of classic and sophisticated optimization methods that have successfully been applied to solve the problem of hydro unit load dispatch (HULD). However, DP will be faced with the curse of dimensionality with the increase of unit number and installed generating capacity of hydropower station. With the appearance of the huge hydropower station similar to the Three George with 26 generators of 700 MW, it is hard to apply the DP to large scale HULD problem. It is crucial to seek for other optimization techniques in order to improve the operation quality and efficiency. Different with the most of literature about power generation scheduling that focused on the comparisons of novel PSO algorithms with other techniques, the paper will pay emphasis on comparison study of PSO with DP based on a case hydropower station. The objective of study is to seek for an effective and feasible method for the large scale of hydropower station of the current and future in China. This paper first compares the performance of PSO and DP using a sample load curve of the Wujiangdu hydropower plant located in the upper stream of the Yangtze River in China and contained five units with the installed capacity of 1250 MW. Next, the effect of different load interval and unit number on the optimal results and efficiency of two methods has also been implemented. The comparison results show that the PSO is feasible for HULD. Furthermore, we simulated the effect of the magnitude of unit number and load capacity on the optimal results and cost time. The simulation comparisons show that PSO has a great advantage over DP in the efficiency and will be one of effective methods for HULD problem of huge hydropower stations. (author)

Characteristic study of high-Tc superconducting maglev under side-loading

International Nuclear Information System (INIS)

Wang Wei; Wang Jiasu; Liu Wei; Zheng Jun; Lin Qunxu; Pan Siting; Deng Zigang; Ma Guangtong; Wang Suyu

2009-01-01

In practical application of High-T c Superconducting (HTS) maglev, slant is an observable defect. It was caused by constantly one side on and off the vehicle by passengers. So far, this phenomenon has not been reported yet. In order to understand its influence on the stability of the HTS maglev, we experimentally studied the dynamic characteristic and slant effect of HTS maglev under center-load and side-load. It was found that load destabilizes the vehicle, and the side-load can obviously slant the vehicle body. In the end, the pre-load method was proposed to enhance the dynamic stability and suppress the slant, which proved to be considerably effective. These results are critical in practical running of HTS maglev

Dynamic queuing transmission model for dynamic network loading

DEFF Research Database (Denmark)

Raovic, Nevena; Nielsen, Otto Anker; Prato, Carlo Giacomo

2017-01-01

and allowing for the representation of multiple vehicle classes, queue spillbacks and shock waves. The model assumes that a link is split into a moving part plus a queuing part, and p that traffic dynamics are given by a triangular fundamental diagram. A case-study is investigated and the DQTM is compared...

Evaluation of Dynamic Load Factors for a High-Speed Railway Truss Arch Bridge

Directory of Open Access Journals (Sweden)

Ding Youliang

2016-01-01

Full Text Available Studies on dynamic impact of high-speed trains on long-span bridges are important for the design and evaluation of high-speed railway bridges. The use of the dynamic load factor (DLF to account for the impact effect has been widely accepted in bridge engineering. Although the field monitoring studies are the most dependable way to study the actual DLF of the bridge, according to previous studies there are few field monitoring data on high-speed railway truss arch bridges. This paper presents an evaluation of DLF based on field monitoring and finite element simulation of Nanjing DaShengGuan Bridge, which is a high-speed railway truss arch bridge with the longest span throughout the world. The DLFs in different members of steel truss arch are measured using monitoring data and simulated using finite element model, respectively. The effects of lane position, number of train carriages, and speed of trains on DLF are further investigated. By using the accumulative probability function of the Generalized Extreme Value Distribution, the probability distribution model of DLF is proposed, based on which the standard value of DLF within 50-year return period is evaluated and compared with different bridge design codes.

Dynamic Analysis of Load Operations of Two-Stage SOFC Stacks Power Generation System

Directory of Open Access Journals (Sweden)

Paulina Pianko-Oprych

2017-12-01

Full Text Available The main purpose of this paper was to develop a complete dynamic model of a power generation system based on two serially connected solid oxide fuel cell stacks. The uniqueness of this study lies in a different number of fuel cells in the stacks. The model consists of the electrochemical model, mass and energy balance equations implemented in MATLAB Simulink environment. Particular attention has been paid to the analysis of the transient response of the reformers, fuel cells and the burner. The dynamic behavior of the system during transient conditions was investigated by load step changing. The model evaluates electrical and thermal responses of the system at variable drawn current. It was found that a decrease of 40% in the 1st stage and 2nd solid oxide fuel cell (SOFC stacks drawn current caused both stacks temperature to drop by 2%. An increase of the cell voltage for the 1st and 2nd SOFC stacks led to very fast steam reformer response combined with a slight decrease in reformer temperature, while a considerable burner temperature increase of 70 K can be observed. Predictions of the model provide the basic insight into the operation of the power generation-based SOFC system during various transients and support its further design modifications.

Scheduling of radio-controlled heating load

International Nuclear Information System (INIS)

Fox, B.; McCartney, A.I.; McCann, B.M.

1998-01-01

An economic loading program has been adapted to enable it to obtain an optimum heat-load profile to meet the forecast heat requirement. The heat load is represented by a 'generator' whose load is constrained to be negative. The incremental cost of this unit is a heat energy price. This is adjusted to obtain a heat profile containing the requisite energy. The profile is then used by a dynamic programming algorithm to derive a commitment pattern for each block. A case study is presented which shows that the procedure can minimise heat energy cost. It is also shown that use of the proposed method results in less generator load cycling. This reduced regulation duty should improve reliability. (author)

Dependence of loading time on control parameters in a standard vapour—loaded magneto—optical trap

International Nuclear Information System (INIS)

Zhang Yi-Chi; Wu Ji-Zhou; Li Yu-Qing; Ma Jie; Wang Li-Rong; Zhao Yan-Ting; Xiao Lian-Tuan; Jia Suo-Tang

2011-01-01

Loading time is one of the most important dynamic characteristics of a magneto—optical trap. In this paper, we primarily report on a detailed experimental study of the effects of some magneto—optical trap control parameters on loading time, including the background vacuum pressure, the magnetic field gradient, and the intensities of trapping and repumping lasers. We compare the results with previous theoretical and experimental results, and give qualitative analysis. These experimental investigations offer some useful guidelines to control the loading time of magneto—optical traps. The controllable loading time achieved is helpful to enhance the signal-to-noise ratio of photoassociation spectroscopy, which is remarkably improved from 7 to 28.6. (atomic and molecular physics)

Load Sharing Multiobjective Optimization Design of a Split Torque Helicopter Transmission

Directory of Open Access Journals (Sweden)

Chenxi Fu

2015-01-01

Full Text Available Split torque designs can offer significant advantages over the traditional planetary designs for helicopter transmissions. However, it has two unique properties, gap and phase differences, which result in the risk of unequal load sharing. Various methods have been proposed to eliminate the effect of gap and promote load sharing to a certain extent. In this paper, system design parameters will be optimized to change the phase difference, thereby further improving load sharing. A nonlinear dynamic model is established to measure the load sharing with dynamic mesh forces quantitatively. Afterwards, a multiobjective optimization of a reference split torque design is conducted with the promoting of load sharing property, lightweight, and safety considered as the objectives. The load sharing property, which is measured by load sharing coefficient, is evaluated under multiple operating conditions with dynamic analysis method. To solve the multiobjective model with NSGA-II, an improvement is done to overcome the problem of time consuming. Finally, a satisfied optimal solution is picked up as the final design from the Pareto optimal front, which achieves improvements in all the three objectives compared with the reference design.

Calculation of relative tube/tube support plate displacements in steam generators under accident condition loads using non-linear dynamic analysis methodologies

International Nuclear Information System (INIS)

Smith, R.E.; Waisman, R.; Hu, M.H.; Frick, T.M.

1995-01-01

A non-linear analysis has been performed to determine relative motions between tubes and tube support plates (TSP) during a steam line break (SLB) event for steam generators. The SLB event results in blowdown of steam and water out of the steam generator. The fluid blowdown generates pressure drops across the TSPS, resulting in out-of-plane motion. The SLB induced pressure loads are calculated with a computer program that uses a drift-flux modeling of the two-phase flow. In order to determine the relative tube/TSP motions, a nonlinear dynamic time-history analysis is performed using a structural model that considers all of the significant component members relative to the tube support system. The dynamic response of the structure to the pressure loads is calculated using a special purpose computer program. This program links the various substructures at common degrees of freedom into a combined mass and stiffness matrix. The program accounts for structural non-linearities, including potential tube and TSP interaction at any given tube position. The program also accounts for structural damping as part of the dynamic response. Incorporating all of the above effects, the equations of motion are solved to give TSP displacements at the reduced set of DOF. Using the displacement results from the dynamic analysis, plate stresses are then calculated using the detailed component models. Displacements form the dynamic analysis are imposed as boundary conditions at the DOF locations, and the finite element program then solves for the overall distorted geometry. Calculations are also performed to assure that assumptions regarding elastic response of the various structural members and support points are valid

A nonlocal strain gradient model for dynamic deformation of orthotropic viscoelastic graphene sheets under time harmonic thermal load

Science.gov (United States)

Radwan, Ahmed F.; Sobhy, Mohammed

2018-06-01

This work presents a nonlocal strain gradient theory for the dynamic deformation response of a single-layered graphene sheet (SLGS) on a viscoelastic foundation and subjected to a time harmonic thermal load for various boundary conditions. Material of graphene sheets is presumed to be orthotropic and viscoelastic. The viscoelastic foundation is modeled as Kelvin-Voigt's pattern. Based on the two-unknown plate theory, the motion equations are obtained from the dynamic version of the virtual work principle. The nonlocal strain gradient theory is established from Eringen nonlocal and strain gradient theories, therefore, it contains two material scale parameters, which are nonlocal parameter and gradient coefficient. These scale parameters have two different effects on the graphene sheets. The obtained deflection is compared with that predicted in the literature. Additional numerical examples are introduced to illustrate the influences of the two length scale coefficients and other parameters on the dynamic deformation of the viscoelastic graphene sheets.

Stress distribution in dental prosthesis under an occlusal combined dynamic loading

International Nuclear Information System (INIS)

Merdji, A.; Bachir Bouiadjra, B.; Ould Chikh, B.; Mootanah, R.; Aminallah, L.; Serier, B.; Muslih, I.M.

2012-01-01

Highlights: ► The mechanical stress reaches the highest in areas of cortical bones. ► The mechanical stress in the cancellous bone reaches greatest in the bottom of the dental implant. ► Implant with low-volume bone might cause increased stress concentration in the cortical bone. -- Abstract: The biomechanical behavior of osseointegrated dental prostheses systems plays an important role in its functional longevity inside the bone. Simulation of these systems requires an accurate modeling of the prosthesis components, the jaw bone, the implant–bone interface, and the response of the system to different types of applied forces. The purpose of this study was to develop a new three-dimensional model of an osseointegrated molar dental prosthesis and to carry out finite element analysis to evaluate stress distributions in the bone and the dental prosthesis compounds under an occlusal combined dynamic load was applied to the top of the occlusale face of the prosthesis crown. The jaw bone model containing cortical bone and cancellous bone was constructed by using computer tomography scan pictures and Computer Aided Design tools. The dental prosthesis compounds were constructed, simulating the commercially available cylindrical implant of 4.8 mm diameter and 10 mm length. Both finite element models were created in Abaqus finite element software. All materials used in the models were considered to be isotropic, homogeneous and linearly elastic. The elastic properties, loads and constraints used in the model were taken from published data. Results of our finite element analyses, indicated that the maximum stresses were located around the mesial neck of the implant, in the marginal bone. Thus, this area should be preserved clinically in order to maintain the bone–implant interface structurally and functionally.

Methodology for combining dynamic responses

International Nuclear Information System (INIS)

Cudlin, R.; Hosford, S.; Mattu, R.; Wichman, K.

1978-09-01

The NRC has historically required that the structural/mechanical responses due to various accident loads and loads caused by natural phenomena, (such as earthquakes) be combined when analyzing structures, systems, and components important to safety. Several approaches to account for the potential interaction of loads resulting from accidents and natural phenomena have been used. One approach, the so-called absolute or linear summation (ABS) method, linearly adds the peak structural responses due to the individual dynamic loads. In general, the ABS method has also reflected the staff's conservative preference for the combination of dynamic load responses. A second approach, referred to as SRSS, yields a combined response equal to the square root of the sum of the squares of the peak responses due to the individual dynamic loads. The lack of a physical relationship between some of the loads has raised questions as to the proper methodology to be used in the design of nuclear power plants. An NRR Working Group was constituted to examine load combination methodologies and to develop a recommendation concerning criteria or conditions for their application. Evaluations of and recommendations on the use of the ABS and SRSS methods are provided in the report

Short-Term Load Forecasting Based Automatic Distribution Network Reconfiguration: Preprint

Energy Technology Data Exchange (ETDEWEB)

Jiang, Huaiguang [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Ding, Fei [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhang, Yingchen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jiang, Huaiguang [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Ding, Fei [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhang, Yingchen [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-07-26

In the traditional dynamic network reconfiguration study, the optimal topology is determined at every scheduled time point by using the real load data measured at that time. The development of load forecasting technique can provide accurate prediction of load power that will happen in future time and provide more information about load changes. With the inclusion of load forecasting, the optimal topology can be determined based on the predicted load conditions during the longer time period instead of using the snapshot of load at the time when the reconfiguration happens, and thus it can provide information to the distribution system operator (DSO) to better operate the system reconfiguration to achieve optimal solutions. Thus, this paper proposes a short-term load forecasting based approach for automatically reconfiguring distribution systems in a dynamic and pre-event manner. Specifically, a short-term and high-resolution distribution system load forecasting approach is proposed with support vector regression (SVR) based forecaster and parallel parameters optimization. And the network reconfiguration problem is solved by using the forecasted load continuously to determine the optimal network topology with the minimum loss at the future time. The simulation results validate and evaluate the proposed approach.

On the way to reliable aeroelastic load simulation on VAWT's

DEFF Research Database (Denmark)

Larsen, Torben J.; Aagaard Madsen, Helge

2013-01-01

In this paper a method for an implementation of a 2D actuator cylinder flow model of an Vertical Axis Wind Turbine (VAWT) is presented. The model is implemented in a full aeroelastic code including consideration of structural dynamics, dynamic inflow, tower shadow and dynamic stall, which is needed...... for a full load analysis relating to eg. certification of a VAWT turbine. Further on, principal load cases according to the IEC61400-1 are simulated for a fictitious 5MW VAWT turbine in it’s simplest 2 bladed Darrieus configuration. The IEC61400-1 load cases, originally developed for Horizontal Axis Wind...... Turbines (HAWT’s), are discussed regarding the application to VAWT’s. Further on a small section regarding aerodynamic flow in curved motion is included....

Dynamics three-tier hydraulic crane-manipulators

OpenAIRE

Lagerev I.A.; Lagerev A.V.

2018-01-01

The methods and generalized recommendations for modeling dynamic loading of load-bearing elements of steel structures of three-tier hydraulic cranes-manipulators are considered. Mathematical models have been developed to study the dynamics of moving elements of the crane-manipulator, the movement of the load-lifting machine on a stochastic uneven surface with a suspended load. The presented approaches can be used to calculate other types of jib cranes equipped with hydraulic drive.

Thermal buckling behavior of defective CNTs under pre-load: A molecular dynamics study.

Science.gov (United States)

Mehralian, Fahimeh; Tadi Beni, Yaghoub; Kiani, Yaser

2017-05-01

Current study is concentrated on the extraordinary properties of defective carbon nanotubes (CNTs). The role of vacancy defects in thermal buckling response of precompressed CNTs is explored via molecular dynamics (MD) simulations. Defective CNTs are initially compressed at a certain ratio of their critical buckling strain and then undergo a uniform temperature rise. Comprehensive study is implemented on both armchair and zigzag CNTs with different vacancy defects including monovacancy, symmetric bivacancy and asymmetric bivacancy. The results reveal that defects have a pronounced impact on the buckling behavior of CNTs; interestingly, defective CNTs under compressive pre-load show higher resistance to thermal buckling than pristine ones. In the following, the buckling response of defective CNTs is shown to be dependent on the vacancy defects, location of defects and chirality. Copyright © 2017 Elsevier Inc. All rights reserved.

Dynamic behaviour of prestressed concrete bridges

International Nuclear Information System (INIS)

Javor, T.

1982-01-01

The paper presents the results of experimental research of dynamic effects on prestressed concrete bridges in dynamic load tests using testing vehicles. The bridges were passed over in both directions at various speeds also running over an artificial unevenness to produce impact loads. From investigated bridges are shown the dynamic quantities such as dynamic coefficients, natural frequency, logarithmical decrement of damping, etc. (orig.) [de

Optimal design of high-speed loading spindle based on ABAQUS

Science.gov (United States)

Yang, Xudong; Dong, Yu; Ge, Qingkuan; Yang, Hai

2017-12-01

The three-dimensional model of high-speed loading spindle is established by using ABAQUS’s modeling module. A finite element analysis model of high-speed loading spindle was established by using spring element to simulate bearing boundary condition. The static and dynamic performance of the spindle structure with different specifications of the rectangular spline and the different diameter neck of axle are studied in depth, and the influence of different spindle span on the static and dynamic performance of the high-speed loading spindle is studied. Finally, the optimal structure of the high-speed loading spindle is obtained. The results provide a theoretical basis for improving the overall performance of the test-bed

Investigation of Unsteady Pressure-Sensitive Paint (uPSP) and a Dynamic Loads Balance to Predict Launch Vehicle Buffet Environments

Science.gov (United States)

Schuster, David M.; Panda, Jayanta; Ross, James C.; Roozeboom, Nettie H.; Burnside, Nathan J.; Ngo, Christina L.; Kumagai, Hiro; Sellers, Marvin; Powell, Jessica M.; Sekula, Martin K.;

Dynamic processes of domain switching in lead zirconate titanate under cyclic mechanical loading by in situ neutron diffraction

International Nuclear Information System (INIS)

Pojprapai, Soodkhet; Luo, Zhenhua; Clausen, Bjorn; Vogel, Sven C.; Brown, Donald W.; Russel, Jennifer; Hoffman, Mark

2010-01-01

The performance of ferroelectric ceramics is governed by the ability of domains to switch. A decrease in the switching ability can lead to degradation of the materials and failure of ferroelectric devices. In this work the dynamic properties of domain reorientation are studied. In situ time-of-flight neutron diffraction is used to probe the evolution of ferroelastic domain texture under mechanical cyclic loading in bulk lead zirconate titanate ceramics. The high sensitivity of neutron diffraction to lattice strain is exploited to precisely analyze the change of domain texture and strain through a full-pattern Rietveld method. These results are then used to construct a viscoelastic model, which explains the correlation between macroscopic phenomena (i.e. creep and recovered deformation) and microscopic dynamic behavior (i.e. ferroelastic switching, lattice strain).

Working memory load improves early stages of independent visual processing

OpenAIRE

Cocchi, Luca; Toepel, Ulrike; De Lucia, Marzia; Martuzzi, Roberto; Wood, Stephen J.; Carter, Olivia; Murray, Micah M.

2010-01-01

Increasing evidence suggests that working memory and perceptual processes are dynamically interrelated due to modulating activity in overlapping brain networks. However, the direct influence of working memory on the spatio-temporal brain dynamics of behaviorally relevant intervening information remains unclear. To investigate this issue, subjects performed a visual proximity grid perception task under three different visual-spatial working memory (VSWM) load conditions. VSWM load was manipula...

Evaluation of self-assembled HCPT-loaded PEG-b-PLA nanoparticles by comparing with HCPT-loaded PLA nanoparticles.

Science.gov (United States)

Yang, Xiangrui; Wu, Shichao; Wang, Yange; Li, Yang; Chang, Di; Luo, Yin; Ye, Shefang; Hou, Zhenqing

2014-12-01

We present a dialysis technique to prepare the 10-hydroxycamptothecin (HCPT)-loaded nanoparticles (NPs) using methoxypolyethylene glycol-poly(D,L-lactide) (PEG-b-PLA) and PLA, respectively. Both HCPT-loaded PEG-b-PLA NPs and HCPT-loaded PLA NPs were characterized by differential scanning calorimetry (DSC), dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results showed that the HCPT-loaded PEG-b-PLA NPs and HCPT-loaded PLA NPs presented a hydrodynamic particle size of 120.1 and 226.8 nm, with a polydispersity index of 0.057 and 0.207, a zeta potential of -31.2 and -45.7 mV, drug encapsulation efficiency of 44.52% and 44.94%, and drug-loaded content of 7.42% and 7.49%, respectively. The HCPT-loaded PEG-b-PLA NPs presented faster drug release rate compared to the HCPT-loaded PLA NPs. The HCPT-loaded PEG-b-PLA NPs presented higher cytotoxicity than the HCPT-loaded PLA NPs. These results suggested that the HCPT-loaded PEG-b-PLA NPs presented better characteristics for drug delivery compared to HCPT-loaded PLA NPs.

Optimal Design and Real Time Implementation of Autonomous Microgrid Including Active Load

OpenAIRE

Mohamed A. Hassan; Muhammed Y. Worku; Mohamed A. Abido

2018-01-01

Controller gains and power-sharing parameters are the main parameters affect the dynamic performance of the microgrid. Considering an active load to the autonomous microgrid, the stability problem will be more involved. In this paper, the active load effect on microgrid dynamic stability is explored. An autonomous microgrid including three inverter-based distributed generations (DGs) with an active load is modeled and the associated controllers are designed. Controller gains of the inverters ...