Bus bar aeolian vibration field tests

Large amplitude bus bar aeolian vibration may lead to post insulator damage. Different damping applications are used to decrease the risk of large amplitude aeolian vibration. In this paper the post insulator load caused by the bus bar aeolian vibration and the effect of damping methods are evaluated. The effects of three types of bus bar connectors and three types of primary structures are studied. Two actual damping devices, damping cable and their combinations are studied. The post insulator loads are studied with strain gage based custom made force sensors installed on the both ends of the post insulator and with the displacement sensor installed on the midpoint of the bus bar. The post insulator loads are calculated from the strain values and the damping properties are determined from the displacement history. The bus bar is deflected with a hanging weight. The weight is released and the bus bar is left to free damped vibration. Both actual bus bar vibration dampers RIBE and SBI were very effective against the aeolian vibration. Combining vibration damper with damping cable will increase the damping ratio but it may be unnecessary considering the extra effort. Bus bar connector type or primary structure have no effect on the vertical load. The bending moment at the post insulator with double sided bus bar connector is significantly higher than at the post insulator with single sided bus bar connector. No reliable conclusions about bus bar connector type effect can be done, but the roller bearing type or central bearing type connector may reduce the bending moment. The RHS steel frame as primary structure may increase the bending moment peak values since it is the least rigid primary structure type and it may start to vibrate as a response to the awakening force of the vibrating bus bar.

Critical aspects on the behavior of material from the mechanical tool-workpiece interaction in single point diamond turning

Some material aspects such as grain size, purity and anisotropy exert an important influence on surface quality, especially in single point diamond turning. The aim of this paper is to present and discuss some critical factors that can limit the accuracy of ultraprecision machining of non-ferrous metals and to identify the effects of them on the cutting mechanism with single point diamond tools. This will be carried out through observations of machined surfaces and chips produced using optical and scanning electron microscopy. Solutions to reduce the influence of some of these limiting factors related with the mechanism of generation of mirror-like surfaces will be discussed.

Non-linear analysis of laminated metal matrix composites by an integrated micro/macro-mechanical model

The present paper describes an integrated micro/macro mechanical study of the elastic-viscoplastic behavior of unidirectional metal matrix composites (MMC). The micromechanical analysis of the elastic moduli is based on the Composites Cylinder Assemblage model (CCA) with comparisons also draw with a Representative Unit Cell (RUC) technique. These "homogenization" techniques are later incorporated into the Vanishing Fiber Diameter (VFD) model and a new formulation is proposed. The concept of a smeared element procedure is employed in conjunction with two different versions of the Bodner and Partom elastic-viscoplastic constitutive model for the associated macroscopic analysis. The formulations developed are also compared against experimental and analytical results available in the literature.

Modelling of mechanical properties of CRFC composites under flexure loading

Carbon Fibre Reinforced Carbon (CFRC) Composites are increasing their applications due to their high strength and Young��s Modulus at high temperatures in inert atmosphere. Although much work has been done on processing and structure and properties relationship, few studies have addressed the modelling of mechanical properties. This work is divided in two parts. In the first part, a modelling of mechanical properties was carried out for two bi-directional composites using a model based on the Bernoulli-Euler theory for symmetric laminated beams. In the second part, acoustic emission (AE) was used as an auxiliary technique for monitoring the failure process of the composites. Differences in fracture behaviour are reflected in patterns of AE.

Arc fusion of self-fluxed nickel alloys

Self-fluxed nickel alloys are usually flame fused after thermal spraying. However, due to the practical aspects of high temperatures reached during flame fusing, large structures such as the hydraulic turbines for power generation, can not be efficiently coated. An alternative is to fuse the sprayed coating with a gas tungsten electric arc. In this case, heating is much more intensive and substrate temperature during and after the fusing operation is much lower, thus reducing the possibility that any problem will occur. In this work, coatings of self-fluxed nickel alloy fused by flame and gas tungsten arc were evaluated as protection of hydraulic turbines against cavitational damage. Several tests were performed, including the ASTM ultrasonically vibration-induced cavitation, optical and scanning electronic microscopic metallography, and hardness tests. The results showed that the arc-fused coating presented better cavitation damage resistance, probably due to its finer microstructure. A field application of this new technique is also described. A self-fluxed Ni alloy was flame sprayed in critical regions of Francis-type hydraulic turbine blades and fused by a gas tungsten arc after spraying. The blades will be inspected during the next two years.

Is there correlation between the turbulent eddies size and mechanical hemolysis ?

Hemolytic profile of an artificial device chronically implanted in the cardiovascular system may represent the difference between the success and failure in its long-term performance. Last decades have witnessed efforts on the development of methods capable of predicting red blood cell damage in artificial organs. However, all of them have had limited success to predict hemolysis. The primary cause of this problem is that such models do not take into consideration structures of turbulent flow. The present paper demonstrates that microscopic measurable occurrences of the turbulent flow may be linked to red blood cell trauma. This study suggests that if the smallest turbulent eddies dimension is under 10 m m hemolysis is not dependent on the exposure time and the red blood cells damage depends only on the dissipation of the turbulent energy in the erythrocyte membrane. The analysis reported here opens the possibility of mapping the flow field in artificial assist devices based on the smallest eddy length scales. This is a promising new trend and should be considered in the designing requirements of the next generations of artificial organs.

Effect of particle morphology on the mechanical and thermo-mechanical behavior of polymer composites

Fiber reinforced polymer composites have been used in many applications, such as in automobile, aerospace and naval industries, due basically to their high strength-to-weight and modulus-to-weight, among other properties. Even though particles are usually not able to lead to the level of reinforcement of fibers, particle reinforced polymer composites have been proposed for many new applications due to their low cost, easy fabrication and isotropic properties. In this work, polymer composites were prepared by incorporating glass particles of different morphologies on poly(aryl sulfones) matrices. Particles with aspect ratios equal to 1, 2.5 and 10 were used. The prepared composites were characterized using electron microscopy and thermal analysis. Mechanical properties of the composites were evaluated using a four-point bending test. The thermo-mechanical behavior of the obtained composites was also investigated. The results showed that the morphology of the particles alter significantly the mechanical properties of composites. Particles with larger values of aspect ratio led to large elastic modulus but low levels of strain at failure. This result was explained by modeling the thermo-mechanical behavior of the composites using a viscoelastic model. Parameters of the model, obtained from a Cole-Cole type of plot, demonstrated that interactions at the polymer-reinforcing agent interface were higher for composites with large aspect ratio particles. Higher levels of interactions at interfaces can lead to higher degrees of stress transfer and, consequently, to composites with large elastic modulus, as experimentally observed.

Escape in a nonideal electro-mechanical system

In this work a particular system is investigated consisting of a pendulum whose point of support is vibrated along a horizontal guide by a two bar linkage driven from a DC motor, considered as a limited power source. This system is nonideal since the oscillatory motion of the pendulum influences the speed of the motor and vice-versa, reflecting in a more complicated dynamical process. This work comprises the investigation of the phenomena that appear when the frequency of the pendulum draws near a secondary resonance region, due to the existing nonlinear interactions in the system. Also in this domain due to the power limitation of the motor, the frequency of the pendulum can be captured at resonance modifying completely the final response of the system. This behavior is known as Sommerfeld effect and it will be studied here for a nonlinear system.

Magnesium hydroxide-based peroxide bleaching of high-brightness mechanical pulps

A high final brightness is desired in most paper and board products. This requires bleaching processes that are able to produce high-brightness pulps. Mechanical pulps are widely bleached for high brightness using alkaline hydrogen peroxide with traditional sodium hydroxide and sodium silicate as additives. With high doses however, peroxide bleaching causes high organic loads in the mill effluent and anionic trash carry-over to papermaking. To alleviate the problems that arise from the use of sodium-based additives in peroxide bleaching, interest in the use of alternative magnesium-based chemicals has increased. In this study, a new, technical high-purity magnesium hydroxide-based bleaching additive was evaluated on laboratory-scale, pilot-scale and mill-scale experiments and trials for its ability to produce a high brightness in peroxide bleaching without the known problems of sodium-based chemicals. The key findings of this study include: a high brightening potential of peroxide bleaching using the Mg(OH)2-based additive, significant reductions (40-70%) in all categories of environmental load, and cationic demand lowered by 60-70% in bleached pulp with no loss in strength properties or in sheet bulk. When used in TMP refiner bleaching, the Mg(OH)2-based additive resulted in savings in specific energy consumption and provided a good bleaching response.

Michelson interferometer with porch swing bearing for portable FTIR spectrometer

The interferometer for low resolution portable Fourier Transform middle infrared spectrometer was developed and studied experimentally. The final aim was a concept for a commercial prototype. Because of the portability, the interferometer should be compact sized and insensitive to the external temperature variations and mechanical vibrations. To minimise the size and manufacturing costs, Michelson interferometer based on plane mirrors and porch swing bearing was selected and no dynamic alignment system was applied. The driving motor was a linear voice coil actuator to avoid mechanical contact of the moving parts. The driving capability for low mirror driving velocities required by the photoacoustic detectors was studied. In total, four versions of such an interferometer were built and experimentally studied. The thermal stability during the external temperature variations and the alignment stability over the mirror travel were measured using the modulation depth of the wide diameter laser beam. Method for estimating the mirror tilt angle from the modulation depth was developed to take account the effect from the non-uniform intensity distribution of the laser beam. The spectrometer stability was finally studied also using the infrared radiation. The latest interferometer was assembled for the middle infrared spectrometer with spectral range from 750 cm���1 to 4500 cm���1. The interferometer size was (197 �� 95 �� 79) mm3 with the beam diameter of 25 mm. The alignment stability as the change of the tilt angle over the mirror travel of 3 mm was 5 ��rad, which decreases the modulation depth only about 0.7 percent in infrared at 3000 cm���1. During the temperature raise, the modulation depth at 3000 cm���1 changed about 1 . . . 2 percentage units per Celsius over short term and even less than 0.2 percentage units per Celsius over the total temperature raise of 30 ��C. The unapodised spectral resolution was 4 cm���1 limited by the aperture size. The best achieved signal to noise ratio was about 38 000:1 with commercially available DLaTGS detector. Although the vibration sensitivity requires still improving, the interferometer performed, as a whole, very well and could be further developed to conform all the requirements of the portable and stable spectrometer.

Action of laccase on mechanical softwood pulps

Tr��fibrernas naturliga egenskaper begr��nsar deras anv��ndning i m��nga till��mpningar. Tr��fibrernas egenskaper kan modifieras genom att binda nya komponenter med ��nskade egenskaper till fiberns yta. DI Stina Gr��nqvist bevisade i sin avhandling att nya funktionella grupper kan bindas till ligninhaltiga tr��fibrer genom att aktivera ytligninet med lackasenzym. Resultaten kan utnyttjas till att f��rb��ttra de traditionella tr��fibrernas och fiberprodukternas egenskaper samt att hitta nya till��mpningar f��r tr��fibrerna. ���Om tr��fibrerna t.ex. modifieras s�� att de blir vattenavst��tande kan de modifierade tr��fibrerna anv��ndas ist��llet f��r plast i f��rpackningar��� ber��ttar Stina Gr��nqvist. Syftet med denna avhandling var att unders��ka effekterna av lackasenzym p�� TMP (termomekanisk massa) och dess fraktioner. I Finland tillverkas TMP av gran och massan inneh��ller rikligt med lignin. N��r ytligninet p�� tr��fibrernas yta modifieras med hj��lp av oxiderande enzymer, s��som lackas, bildas reaktiva radikaler i ligninen p�� fibrernas ytor. De bildade radikalerna kan utnyttjas till att binda komponenter med nya egenskaper till fiberytan. F��r att kunna utnyttja den fulla potentialen av den lackasbaserade modifieringsmetoden beh��vs mera information om s�� v��l de faktorer som p��verkar bildningen av radikaler som om mekanismerna hur de nya komponenterna binds till fibrerna ___________________________________ Puukuitujen luontaiset ominaisuudet rajoittavat niiden hy��dynt��mist�� joissakin sovelluksissa. Ominaisuuksia voidaan kuitenkin muuttaa liitt��m��ll�� kuidun pintaan uusia yhdisteit��. DI Stina Gr��nqvist osoitti v��it��sty��ss����n, ett�� uusia kuitujen ominaisuuksia muuttavia funktionaalisia yhdisteit�� voidaan sitoa ligniinipitoisiin puukuituihin aktivoimalla kuitujen pinnan ligniini�� lakkaasi-entsyymill��. Tutkimuksen tuloksia voidaan hy��dynt���� ligniinipitoisten puukuitujen ominaisuuksien parantamiseen ja jopa t��ysin uusien ominaisuuksien kehitt��miseen. ���Jos kuituja muutetaan vett�� hylkiv��ksi sitomalla kuituihin vett�� hylkivi�� yhdisteit�� entsyymien avulla, voidaan puukuituja k��ytt���� korvaamaan muovia pakkauksissa���, kertoo Stina Gr��nqvist. V��it��sty��n kohteena oli TMP-massan eli kuumahiert��m��ll�� valmistetun mekaanisen puumassojen ja niiden fraktioiden muokkaaminen lakkaasi-entsyymill�� (TMP, Thermomechanical pulp). Suomalainen TMP-massa valmistetaan kuusesta ja siin�� on runsaasti muokkaamatonta ligniini��. Kun puukuidun pinnan ligniini�� muokataan hapettavilla entsyymeill��, muodostuu kuidun pintaan reaktiivisia radikaaleja. Syntyneiden radikaalien avulla kuituihin voidaan liitt���� yhdisteit��, jotka antavat kuidulle uusia ominaisuuksia. Menetelm��n tarjoamien mahdollisuuksien hy��dynt��miseksi tarvitaan tietoa kuidun radikalisointiin ja yhdisteiden liitt��miseen vaikuttavista tekij��ist��.

Comparison study of two competing models of an all mechanical power transmission system

A comparison between two competing models of an all mechanical power transmission system is studied by using Dymola ���software as the simulation tool. This tool is compared with Matlab/ Simulink ���software by using functionality, user-friendliness and price as comparison criteria. In this research we assume that the torque is balanceable and transmission ratios are calculated. Using kinematic connection sketches of the two transmission models, simulation models are built into the Dymola simulation environment. Models of transmission systems are modified according to simulation results to achieve a continuous variable transmission ratio. Simulation results are compared between the two transmission systems. The main features of Dymola and MATLAB/ Simulink are compared. Advantages and disadvantages of the two softwares are analyzed and compared.

Mechanical design and analysis of modular active magnetic bearing test rig

T��ss�� ty��ss�� on tutkittu modulaarisen aktiivimagneettilaakeroidun koelaitteen mekaanista suunnittelua ja analysointia. Suurnopeusroottorin suunnittelun teoria on esitelty. Lis��ksi monia analyyttisi�� mallinnusmenetelmi�� mekaanisten kuormitusten mallintamiseksi on esitelty. Koska kyseess�� on suurnopeuss��hk��kone, roottoridynamiikka ja sen soveltuvuus suunnittelussa on esitelty. Magneettilaakerien rakenteeseen ja toimintaan on tutustuttu osana t��t�� ty��t��. Kirjallisuuskatsaus nykyisist�� koelaitteista esimerkiksi komponenttien ominaisuuksien tunnistamiseen ja roottoridynamiikan tutkimuksiin on esitelty. Ty��n rajauksena on konseptisuunnittelu muunneltavalle magneettilaakeroidulle (AMB) koelaitteelle ja suunnitteluprosessin dokumentointi. Muunneltavuuteen p����dyttiin, koska se mahdollistaa erilaisten komponenttiasetteluiden testaamisen erilaisille magneettilaakerikokoonpanoille ja roottoreille. P����paino t��ss�� ty��ss�� on suurnopeus induktiokoneen roottorin suunnittelussa ja mallintamisessa. Modulaaristen toimilaitteiden kuten magneettilaakerien ja induktios��hk��moottorin rakenne on esitelty ja modulaarisen rakenteen k��ytett��vyyden hy��dyist�� koelaitek��yt��ss�� on dokumentoitu. Analyyttisi�� ja elementtimenetelm����n perustuvia tutkimusmenetelmi�� on k��ytetty tutkittaessa suunniteltua suurnopeusroottoria. Suunnittelun ja analysoinnin tulokset on esitelty ja verrattu kesken����n eri mallinnusmenetelmien v��lill��. Lis��ksi johtop����t��kset s��hk��magneettisten osien liitt��misen monimutkaisuudesta ja vaatimuksista roottoriin ja toimilaitteisiin sek�� mekaanisten ett�� s��hk��magneettisten ominaisuuksien optimoimiseksi on dokumentoitu.

Microscopic variability in mechanical defence and herbivory response in microphyllous leaves of tropical herb species from Serra do Cip��, Brazil

Tropical high altitude grasslands present several species with both microphyllous and highly sclerophyllous leaves, and co-occur in specific soil patches, thus exposed to identical environments. In this article we describe herbivory among co-occurring microphyllous species in a tropical high altitude grassland ecosystem of Serra do Cip��, Minas Gerais state, and we tested the effect of variable anatomic traits on leaf herbivory patterns. Leaf anatomical traits were investigated for Baccharis imbricata Heering , Lavoisiera imbricata DC. and L. subulata Triana (focal species). Herbivory was measured from branches and leaves of individual plants and compared among co-occurring species within one multispecific shrub patch and among L. subulata individuals from this patch and an adjacent monospecific patch. For all present plant species and individuals we estimated the proportion of leaves with different levels of area lost. For the focal species, six leaves were sorted and taken for histological sectioning, in order to allow precise measures of defensive structures. Relative mean leaf area lost differed significantly among the six species found in the multispecific patch. Lavoisiera subulata individuals were more attacked in the multispecific than in the monospecific patch. Leaf margin protection traits in both B. imbricata and L. imbricata showed significant effect against herbivory. Data suggest that some anatomic traits have direct effect against herbivory but their effect are not clearly perceptible among branches within individual plants or among plants within the same species.