Kapteeni Artturi Vuorimaa 1/4 1958

Kirje 1.4.1958

A novel approachfor assessing the fatigue strength of ultrasonic impact treated welded structures.

It is commonly observed that complex fabricated structures subject tofatigue loading fail at the welded joints. Some problems can be corrected by proper detail design but fatigue performance can also be improved using post-weld improvement methods. In general, improvement methods can be divided into two main groups: weld geometry modification methods and residual stress modification methods. The former remove weld toe defects and/or reduce the stress concentrationwhile the latter introduce compressive stress fields in the area where fatigue cracks are likely to initiate. Ultrasonic impact treatment (UIT) is a novel post-weld treatment method that influences both the residual stress distribution andimproves the local geometry of the weld. The structural fatigue strength of non-load carrying attachments in the as-welded condition has been experimentally compared to the structural fatigue strength of ultrasonic impact treated welds. Longitudinal attachment specimens made of two thicknesses of steel S355 J0 have been tested for determining the efficiency of ultrasonic impacttreatment. Treated welds were found to have about 50% greater structural fatigue strength, when the slope of the S-N-curve is three. High mean stress fatigue testing based on the Ohta-method decreased the degree of weld improvement only 19%. This indicated that the method could be also applied for large fabricated structures operating under high reactive residual stresses equilibrated within the volume of the structure. The thickness of specimens has no significant effect tothe structural fatigue strength. The fatigue class difference between 5 mm and 8 mm specimen was only 8%. It was hypothesized that the UIT method added a significant crack initiation period to the total fatigue life of the welded joints. Crack initiation life was estimated by a local strain approach. Material parameters were defined using a modified Uniform Material Law developed in Germany. Finite element analysis and X-ray diffraction were used to define, respectively, the stress concentration and mean stress. The theoretical fatigue life was found to have good accuracy comparing to experimental fatigue tests.The predictive behaviour of the local strain approach combined with the uniformmaterial law was excellent for the joint types and conditions studied in this work.

Salient Pole Synchronous Machine Modelling in an Industrial Direct Torque Controlled Drive Application

Synchronous motors are used mainly in large drives, for example in ship propulsion systems and in steel factories' rolling mills because of their high efficiency, high overload capacity and good performance in the field weakening range. This, however, requires an extremely good torque control system. A fast torque response and a torque accuracy are basic requirements for such a drive. For large power, high dynamic performance drives the commonly known principle of field oriented vector control has been used solely hitherto, but nowadays it is not the only way to implement such a drive. A new control method Direct Torque Control (DTC) has also emerged. The performance of such a high quality torque control as DTC in dynamically demanding industrial applications is mainly based on the accurate estimate of the various flux linkages' space vectors. Nowadays industrial motor control systems are real time applications with restricted calculation capacity. At the same time the control system requires a simple, fast calculable and reasonably accurate motor model. In this work a method to handle these problems in a Direct Torque Controlled (DTC) salient pole synchronous motor drive is proposed. A motor model which combines the induction law based "voltage model" and motor inductance parameters based "current model" is presented. The voltage model operates as a main model and is calculated at a very fast sampling rate (for example 40 kHz). The stator flux linkage calculated via integration from the stator voltages is corrected using the stator flux linkage computed from the current model. The current model acts as a supervisor that prevents only the motor stator flux linkage from drifting erroneous during longer time intervals. At very low speeds the role of the current model is emphasised but, nevertheless, the voltage model always stays the main model. At higher speeds the function of the current model correction is to act as a stabiliser of the control system. The current model contains a set of inductance parameters which must be known. The validation of the current model in steady state is not self evident. It depends on the accuracy of the saturated value of the inductances. Parameter measurement of the motor model where the supply inverter is used as a measurement signal generator is presented. This so called identification run can be performed prior to delivery or during drive commissioning. A derivation method for the inductance models used for the representation of the saturation effects is proposed. The performance of the electrically excited synchronous motor supplied with the DTC inverter is proven with experimental results. It is shown that it is possible to obtain a good static accuracy of the DTC's torque controller for an electrically excited synchronous motor. The dynamic response is fast and a new operation point is achieved without oscillation. The operation is stable throughout the speed range. The modelling of the magnetising inductance saturation is essential and cross saturation has to be considered as well. The effect of cross saturation is very significant. A DTC inverter can be used as a measuring equipment and the parameters needed for the motor model can be defined by the inverter itself. The main advantage is that the parameters defined are measured in similar magnetic operation conditions and no disagreement between the parameters will exist. The inductance models generated are adequate to meet the requirements of dynamically demanding drives.

O Herre

Soitinnus: lauluääni.

De jurejurando suppletorio

Invocatio: D.D.

Saha- ja leikkurikarsinnan vaikutukset rauduskoivun puuaineen värivikoihin, oksien kyljestymiseen ja läpimitan kasvuun

Seloste artikkelista: Influence of saw and secateur pruning on stem discolouration, wound cicatrisation and diameter growth of Betula pendula. Silva Fennica 42 (2008) : 2, s. 295-305.

Charta öfver Åland

1 kartta : käsinvär. ; 41,5 x 71,5 cm, lehti 46 x 74,7 cm.

Romanssien ja runouden aikakausi. Thomas Warton keskiaikaa määrittelemässä 1750–1790

Tutkimukseni käsittelee keskiajan nousua historian tärkeäksi periodiksi 1700-luvun Englannissa näkökulmanaan Thomas Wartonin (1726–1790) kirjoitukset. Warton oli Oxfordin yliopistossa toiminut oppinut antikvaari. Wartonin pääteos History of English Poetry (1774–1781) ei nimestään huolimatta ollut moderni kirjallisuushistoria vaan 1000–1500-luvun kirjoitettua kulttuuria laajasti käsitellyt vernakulaariin kirjallisuuteen pohjautunut esitys. Warton ja hänen lähipiiriinsä kuuluneet tutkijat tarjoavat erityisen mahdollisuuden tarkastella, miten käsitys keskiajasta omana aikakautenaanmuodostui 1700-luvun lopulla. Tutkin Wartonin ja hänen aikalaistensa toisen vuosituhannen alusta kirjoittamia arvioita Michel de Certeaun historiografisen operaation käsitteen avulla. Se koostuu kolmesta vaiheesta: Alue määrittelee sosiaaliset riippuvuussuhteet ja vaikuttimet, jotka ohjaavat tutkimusta. Käytäntö viittaa siihen, miten historioitsija valitsee materiaalinsa ja muokkaa siitä historiankirjoituksena hahmottuvan kokonaisuuden. Lopuksi kirjoitus konkreettisena ja fyysisenä ilmiönä luo illuusion lopullisuudesta ja huonosti sopivien osien yhteenkuuluvuudesta. de Certeaun teoria soveltuu paremmin vanhemman historiankirjoituksen ja oppineisuuden tarkasteluun kuin historiantutkimuksen narratiiveja analysoivat teokset, koska se kontekstualisoi laajemmin historiankirjoitukseen vaikuttavat ilmiöt. Thomas Warton ja muut 1700-luvun puolivälin oppineet määrittelivät keskiajan fiktiivisten tekstien avulla. Warton tutustui tarkasti romansseihin ja kronikoihin. Erityisen suuri merkitys keskiajan hahmottamisen kannalta oli Geoffrey Monmouthilaisen kronikalla Historia regum britanniae, joka esitteli Englannin myyttisen varhaisen historian yhdistämällä Rooman ja oman kansallisen perinteen. Geoffreyn kronikan avulla Warton huomasi keskiaikaisten tarinoiden laajan vaikutuksen; hän kirjoitti erityisesti kuningas Arthuriin liittyneiden kertomusten merkityksestä, joka jatkui aina 1500-luvulle asti. Näin Warton löysi antiikin perinteelle haastajan keskiaikaisesta kulttuurista. Wartonin tapa esitellä keskiaikaa perustui osittain valistusajan sulavasti kirjoitetuille universaalihistorioille, osittain oppineelle luettelomaiselle esitystavalle. Käytännössä Wartonin pitkät johdantotutkielmat kuitenkin johdattavat lukijaa keskeisiin teemoihin. Niitä ovat mielikuvituksen väheneminen uusimmassa kirjallisuudessa ja toisaalta hienostuneisuuden ja tiedon kasvu. Warton ei missään vaiheessa kerro, liittyvätkö nämä teemat yhteen, mutta tulkintani mukaan ne liittyivät. Warton ajatteli kirjallisuuden menettäneen olennaisen mielikuvituksen samaan aikaan, kun yhteiskunta oli kehittynyt. Tämä auttaa hahmottamaan koko kirjallisuuden historiaa: Warton etsi alkuperäistä mielikuvitusta niin antiikin Kreikasta, Orientista kuin muinaisesta Skandinaviasta. History of English Poetry ei pohtinut vain kirjallisuuden ja yhteiskunnan suhdetta, sillä Warton ajatteli voivansa tutkia keskiajan yhteiskuntaa kronikoiden ja romanssien avulla. Hänen käsityksensä feodalismista, hovien elämästä ja keskiaikaisista tavoista perustuivat niihin. Warton ei huomannut, että hänen käyttämänsä lähteet olivat tietoisia kirjallisia konstruktioita vaan hän piti niitä totuudenmukaisina kuvauksina. Toisaalta Wartonin tulkintaan heijastuivat myös 1700-luvun käsitykset yhteiskunnasta. Keskiajan lähteiden kuvaukset ja 1700-luvun ideaalit vaikuttivat lopulta siihen, millaiseksi populaari kuva keskiajasta kehittyi.

Christina Rossetti's "Goblin market" : Milton revised or revived?

The present study examines Christina Rossetti's (1830-94) best-known poem "Goblin Market" (1859) as a response to John Milton's (1608-74) Paradise Lost (1667) and Paradise Regained (1674). Rossetti's poem relates to Milton's twin epics with a surprising degree of complexity, something that the thesis demonstrates through a large number of hitherto unexplored textual parallels. In its recontextualisation of Rossetti's poetry, this study balances interpretative strategies evolved by feminism with more historicist readings. SinceGilbert and Gubar's landmark feminist work of 1979, it has become something of a critical commonplace that Milton was a figure of patriarchal oppression whom women writers have challenged through revision. As a consequence, intertextual Rossetti studies have tended to emphasise such a revisionist element in her achievement. But if we place "Goblin Market" within the larger context of Rossetti's thoughts on religion and poetry throughout her writing, and if we de-emphasise the dichotomy between Rossetti and her male precursor, alternative patterns of reading begin to emerge. This thesis argues that Rossetti's aim was not only to revise Milton but also to revive him. It develops this point in several ways: first, by introducing the subject and theoretically arguing that literary allusiveness is not necessarily a matter of oedipal or feminist envy only (Chapter One); second, by determining the nature and extent of Rossetti's Miltonic allusions in terms of theme, imagery and language (Chapter Two);and third, by examining their function in terms of argument (Chapters Three andFour). I n an age of increasing religious doubt, Rossetti's poetry provided a subtle challenge not so much to Milton as to the emerging scepticism and aestheticism in Victorian society and its art-world, and not least to the secular tendencies of the second generation of Pre-Raphaelites, including Dante Gabriel Rossetti. Christina Rossetti was ahead of her time (and perhaps ours) in seeing the feminist potential in both John Milton and the Christian message. In the soul's relation to Christ, gender does not matter. What matters is the individual's quest for salvation, a quest in which poetry is a sacramental act, with a transformative, unifying function. Rossetti's poems both depict and constitute such a quest for union with God, on the assumption that God's word offers a pathway that is open to men as well as women.