Pressure and thermally induced stages of wear in dry sliding of a steel ball against an aluminium-silicon alloy flat

Wear of etched near-eutectic aluminium silicon alloy slid against a steel ball under ambient is explored. The sliding velocity is kept low (0.01 m/s) and the nominal contact pressure is varied in a 15-40 MPa range. Four stages of wear are identified; ultra mild wear, mild wear, severe wear and post severe oxidative wear. The first transition is controlled by the protrusions of silicon particles, projecting out of the aluminium alloy matrix. Once these protrusions disappear under pressure and sliding, oxidation and bulk energy dissipation mechanisms take over to institute transitions to other stages of wear. The phenomenological characteristics of wear stages are explored using a variety of techniques including nanoindentation, focused ion beam milling, electron microscopy, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS) and optical interferometry. (c) 2010 Elsevier B.V. All rights reserved.

Tribology of steel/steel interaction in oil-in-water mulsion; a rationale for lubricity

Oil droplets are dispersed in water by an anionic urfactant to form an emulsion. The lubricity of this emulsion in steel/steel interaction is explored in a ball on flat nanotribometer. The droplet size and charge are measured using dynamic light scattering, while the substrate charge density is estimated using the pH titration method. These data are combined to calculate the DLVO forces for the droplets generated for a range of surfactant concentration and two oil to water volume ratios. The droplets have a clear bi-modal size distribution. The study shows that the smaller droplets which experience weak repulsion are situated (at the highest DLVO barrier) much closer to the substrate than thebigger droplets, which experience the same DLVO force, are. We suggest that the smaller droplets thus play a more important role in lubricity than what the bigger droplets do. The largest volume of such small droplets occurs in the 0.5 mM-1 mM range of surfactant concentration and 1% oil to water volume ratio, where the coefficient of friction is also observed to be the least. (C) 2010 Elsevier Inc. All rights reserved.

Supercapacitor studies of electrochemically deposited PEDOT on stainless steel substrate

There has been increasing interest on various properties and applications of electronically conducting polymers. Polyethylenedioxythiophene (PEDOT) is an interesting polymer of this type as it exhibits very high ionic conductivity. In the present study, PEDOT has been electrochemically deposited on stainless steel (SS) substrate for supercapacitor studies. PEDOT/SS electrodes prepared in 0.1M H2SO4 in presence of a surfactant, sodium dodecylsulphate (SDS), have been found to yield higher specific capacitance (SC) than the electrodes prepared from neutral aqueous electrolyte. The effects of concentration of H(2)SO4(,) concentration of SDS, potential of deposition, and nature of supporting electrolytes used for capacitor studies on SC of the PEDOT/SS electrodes have been studied. SC values as high as 250 F/g in 1M oxalic acid have been obtained during the initial stages of cycling. However, there is a rapid decrease in SC on repeated charge-discharge cycling. Spectroscopic data reflect structural changes in PEDOT on extended cycling. (C) 2007 Wiley Periodicals, Inc.

Molecular model for U centres in caesium iodide

A molecular model has been developed to study the vibrations of U centres in caesium iodide. Employing the rigid ion model with nearest-neighbour short-range forces, the dynamical matrix of order 27 × 27 was solved to obtain the frequencies of the localized modes and the perturbed lattice modes. The results are compared with those obtained from the Green function method.

Koko kansan koti vai kommunistien pesäke? Helsingin Kulttuuritalon rakentaminen ja paikan henki 1955-1959

Helsingin Kulttuuritalo rakennettiin vuosina 1955–1958 vastaamaan Suomen kommunistisen puolueen ja muiden kansandemokraattisten järjestöjen toimitilojen puutteeseen. Kulttuuritalo oli myös kommunistien vastaus Helsingissä jo 1900-luvun alusta lähtien käytyyn konserttisali keskusteluun. Kulttuuritalo rakennettiin SKP:n päämajaksi, mutta sinne asettui myös lukuisia muita kansandemokraattisia järjestöjä. Kulttuuritalon suunnitteli professori Alvar Aalto. Pro gradu -tutkielmassani olen tarkastellut Helsingin Kulttuuritalon rakentamista ja paikan hengen muodostumista vuosien 1955–1959 välillä. Aikarajaus kattaa Kulttuuritalon rakennusvuodet sekä sen ensimmäisen kokonaisen toimintavuoden. Tutkielman ensisijaiset tutkimuskysymykset ovat: Miksi Helsingin Kulttuuritalo rakennettiin, millainen rakennusprosessi oli ja millainen paikan henki Kulttuuritalolle muodostui vuosien 1955–1959 aikana? Teoreettisen viitekehyksen tutkielmalle muodostaa paikan hengen käsite. Primäärilähteinä tutkielmassa ovat Kansan Arkistosta löytyvät Kulttuuritalo Oy:n ja Kulttuurityö ry:n kokoelmat sekä sanomalehdet. Sanomalehtiä käytetään Kulttuuritalon paikan hengen ilmentämiseen. Kulttuuritalo rakennettiin pääasiassa talkoovoimin. Talkoisiin osallistui runsaasti ihmisiä niin pääkaupunkiseudulta kuin ulkopaikkakunnilta. Suurin osa Kulttuuritalon rakentamisen rahoituksesta tuli kommunistisilta poliittisilta järjestöiltä ja ammattijärjestöiltä. Pyynnöistä huolimatta Helsingin kaupungilta tai Suomen valtiolta ei tippunut tukea kommunistien hankkeelle. NKP osallistui Kulttuuritalon rakennuskustannuksiin sekä suorin tavaralahjoituksia että epäsuoraan Bukarestissa sijainneen kansainvälisen rahaston kautta, joka toimi SKP:n rahoittajana. Kulttuuritalon paikan hengen luominen liittyi tiiviisti Kulttuuritalon rakentamiseen, sillä paikan henki alkoi muodostua jo talon rakennusvaiheessa. Kulttuuritalon paikan hengen rakentamiseen osallistuivat niin kommunistit ja kansandemokraatit kuin kommunismin vastustajat. Kommunismin vastustajilla tarkoitan tutkielmassa oikeistoa ja sosiaalidemokraatteja. Kommunismin vastustajat vastustivat tavallisesti myös Kulttuuritaloa, mikä kytkee 1950-luvun suomalaisen antikommunismin Kulttuuritalon paikan hengen muodostamiseen. Kun kommunistit rakensivat Kulttuuritalon paikan hengen positiivista puolta, sosiaalidemokraatit ja oikeistolaiset lehdet osallistuivat sen negatiivisen puolen muodostamiseen. Kulttuuritalon paikan hengestä muodostui vuosien 1955–1959 aikana voimakkaan punainen. Kulttuuritalon punaisuus sai kuitenkin kaksi merkitystä: Kommunisteille ja kansandemokraateille se merkitsi työväenliikkeen solidaarisuutta, tasa-arvoa ja voimaa. Kulttuuritalo oli heille osoitus työväen voimasta, ja he toivoivat sen auttavan kommunisteja saavuttamaan laajemman kannatuksen ja hyväksytyn aseman yhteiskunnassa. Kommunismin vastustajille Kulttuuritalo puolestaan merkitsi perinteistä yhteiskuntaa uhkaavaa tekijää. Kulttuuritalon oli heidän mielestään vaarallinen paikka, jonka avulla kommunistit pyrkivät vahvistamaan asemiaan yhteiskunnassa. Kulttuuritalon paikan henki heijasti näin suomalaisen yhteiskunnan kahtiajakautuneisuutta. Kulttuuritalon paikan henki vaikutti myös talon käyttöön. Kulttuuritalon ottivat innolla omakseen kommunistit ja kansandemokraatit, mutta sosiaalidemokraatit ja oikeistolaiset eivät halunneet sitä käyttää, vaikka Kulttuuritalon juhlasali olikin Helsingissä ainoa, joka täytti kansainvälisestikin tasokkaan akustiikan vaatimukset.

Effect of directionality of unidirectional grinding marks on friction and transfer layer formation of Mg on steel using inclined scratch test

Surface topography has been known to play an important role in the friction and transfer layer formation during sliding. In the present investigation, EN8 steel flats were ground to attain different surface roughness with unidirectional grinding marks. Pure Mg pins were scratched on these surfaces using an Inclined Scratch Tester to study the influence of directionality of surface grinding marks on coefficient of friction and transfer layer formation. Grinding angle (i.e., the angle between direction of scratch and grinding marks) was varied between 0 degrees and 90 degrees during the tests. Experiments were conducted under both dry and lubricated conditions. Scanning electron micrographs of the contact surfaces of pins and flats were used to reveal the surface features that included the morphology of the transfer layer. It was observed that the average coefficient of friction and transfer layer formation depend primarily on the directionality of the grinding marks but were independent of surface roughness on the harder mating surface. In addition, a stick-slip phenomenon was observed, the amplitude of which depended both on the directionality of grinding marks and the surface roughness of the harder mating surface. The grinding angle effect on the coefficient of friction, which consists of adhesion and plowing components, was attributed to the variation of plowing component of friction. (c) 2006 Elsevier B.V. All rights reserved.

A Comparison of Managers’ Perception of Short-Termism in Finland, Sweden and the U.S

Increased media exposure to layoffs and corporate quarterly financial reporting have created arguable a common perception – especially favored by the media itself – that the companies have been forced to improve their financial performance from quarter to quarter. Academically the relevant question is whether companies themselves feel that they are exposed to short-term pressure to perform even if it means that they have to compromise company’s long-term future. This paper studies this issue using results from a survey conducted among the 500 largest companies in Finland. The results show that companies in general feel moderate short-term pressure, with reasonable dispersion across firms. There seems to be a link between the degree of pressure felt, and the firm’s ownership structure, i.e. we find support for the existence of short-term versus long-term owners. We also find significant ownership related differences, in line with expectations, in how such short-term pressure is reflected in actual decision variables such as the investment criteria used.

Fatigue crack propagation in rocker and roller–rocker bearings of railway steel bridges

In this work, a method is proposed for rolling contact fatigue crack propagation analysis using contact and fracture theories in conjunction with fatigue laws. The proposed method is used in the fatigue analysis of rocker and roller–rocker bearings of a railway open web girder bridge which is instrumented with strain gages. Using a contact algorithm based on the minimum energy principle for bodies in rolling contact with dry friction, the normal and tangential pressure distribution are computed. It is seen that the most critical location of a crack in bearings is at a point very close to the contact region, as expected.

Fatigue crack propagation in rocker and roller-rocker bearings of railway steel bridges

In this work, a method is proposed for rolling contact fatigue crack propagation analysis using contact and fracture theories in conjunction with fatigue laws. The proposed method is used in the fatigue analysis of rocker and roller-rocker bearings of a railway open web girder bridge which is instrumented with strain gages. Using a contact algorithm based on the minimum energy principle for bodies in rolling contact with dry friction, the normal and tangential pressure distribution are computed. It is seen that the most critical location of a crack in bearings is at a point very close to the contact region, as expected. (C) 2010 Elsevier Ltd. All rights reserved.

Viscous flow computations using a meshless solver, LSFD-U

The Upwind-Least Squares Finite Difference (LSFD-U) scheme has been successfully applied for inviscid flow computations. In the present work, we extend the procedure for computing viscous flows. Different ways of discretizing the viscous fluxes are analysed for the positivity, which determines the robustness of the solution procedure. The scheme which is found to be more positive is employed for viscous flux computation. The numerical results for validating the procedure are presented.

Changes to near-surface region of PTFE during dry sliding against steel

PTFE specimens were slid against an EN24 disc. The unworn and worn surfaces as well as the wear debris were examined by X-ray diffraction. Sliding was found to introduce (i) shrinkage of the unit cell, (ii) enlargement of crystallites and (iii) residual stresses in the slid PTFE surface. No conformational changes in the 157 helix could be observed due to sliding. The wear debris was found to be 1 mgrm thick warped laminates.