CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of theEstonian Academy of Sciences.
Engineering
Volume 10 No. 1March 2004
Strengtheningof the surface layer microstructure with a laser beam;3–9
Regita Bendikienë, Sangaudas Chodoèinskas,and Edmundas Pupelis
Abstract. Wear resistance and durability of the products depend on thenature of the solid solution and microstructure. Minimal wear have materialswith optimum alloyed solid solution and fine particles, usually carbideinclusions. Such a structure is difficult to obtain using traditional methodsof manufacturing. Blanks of alloyed steels have coarse grains and carbideinclusions of undesirable shape, arranged discretely. To change such amicrostructure is impossible. Therefore the purpose of the present paper is tocreate a desirable microstructure using micrographical laser beam treatment andto evaluate the influence of treatment parameters and point drawing to wearresistance of the surface layer.
Key words: wear resistance, surface strengthening, laser treatment.
Meltingand modification by producing ductile iron castings;10–17
Stasys Boèkus and Aloyzas Dobrovolskis
Abstract. Theeffect of charge materials, melting conditions, section size, spheroidizing andinoculation methods on the chemical composition of melt and the matrixmicrostructure of ductile iron castings has been investigated. Results showthat the amount of pig iron in the charge and the section size have asignificant effect on the amount of ferrite in ductile iron castings. Theincrease of the temperature and holding duration of the melt in an inductionfurnace decreases the carbon content and increases the silicon content. Theintensity of spheroidizing affects the carbon and residual magnesium contentsin the ductile iron castings.
Key words: ductile iron, charge, spheroidizing, inoculation, metallicmatrix.
Adsorptiondistribution of the ion associates and ion-exchange at thewater/1,2-dichloroethane interface by extracting with cesium dicarbollyde;18–22
Tatyana Borisova
Abstract. The paper presentsevaluation of the distribution ratios of dicarbollylcobaltate (III) of alkalimetal salts and of the voluminous constant of exchange of sodium by magnesiumon a monolayer. A comparison of these values, calculated by different methods,has been made and the influence of counterions on the surface activity ofcesium dicarbollyde is investigated. Interfacial tension isotherms have beenused to study the adsorption at the water/1,2-dichloroethane interface and toevaluate the above-mentioned values.
Key words: dicarbollylcobaltate (III) anion,interface, interfacial tension, isotherm, drop-volume method.
Preparationof nanosized W- and WC-based powders and their processing;23–29
Janis Grabis, Ilmars Zalite, Dzidra Jankovica,and Dzintra Rasmane
Abstract. Nanosized particles of tungsten and WC1–x or W2Cwith the averageparticle size of 10–14 nm have been prepared by evaporation and reductionof oxide by hydrogen, ammonia, or hydrocarbones in the radio-frequencynitrogen plasma. The consolidation of carbides containing nanoparticles by hotpressing at 1800 °C provides formation of a singleWC-phase bulk material with the fine-grained microstructure.
Key words: nanosized materials, W-based powders, nitrogen plasma.
Laserablation for 3D nanometric imaging of solids; 30–38
Ilmar Kink, Vambola Kisand, Kristjan Saal,Tanel Tätte, Madis Lobjakas, and Ants Lõhmus
Abstract. A new method for subsurface nanometric imaging is proposedthat combines scanning probe microscopy and laser ablation techniques. Thefeasibility of the method was tested on mica samples by studying laserradiation interaction with the mica surface. The ablation of the samples wascharacterized as functions of deposited radiation energy and of the number oflaser pulses. Additional examples of applicability of the method are presentedusing more complex samples such as a TiC : Ni compound and a biological tooth.
Key words: SPM, laser ablation, three-dimensional imaging.
Testinghardened steel targets for dynamic hardness; 39–44
Ilmar Kleis and ToomasRemi
Abstract. In literature noinformation can be found about any recognized method of testing steels harderthan 350 HV for dynamic hardness, neither about its numerical values fordifferent steels, needed for the prediction of erosion resistance of steels.This paper represents a new method for the determination of dynamic hardnessproperties of hard materials and discusses the test data obtained on steelswith hardness range of 360–820 HV.
Key words: hardened steels,dynamic hardness, dynamic-to-static hardness relationship.
Adaptingthe energetic erosion theory to hardened steels; 45–52
Ilmar Kleis and ToomasRemi
Abstract. This paper presents the ways and means oftransformation of the existing energetic theory into a modified form,applicable for hardened steels by predictingtheir erosion rate in order to obtain a close correlation between thecalculated values and test data. Differently from the initial form of thetheory, employing static hardness for the estimation of particle penetrationdepth into the target surface, the modified theory utilizes dynamic hardness.More specified is the determination of the particle shape factor since besidesits geometry the effect of crushing strength and angle of incidence are takeninto account. In comparison with the values used before, for particles of extrahigh crushing strength as manufactured corundum impacting against hardenedsteel target, the shape factor may obtain values three times higher thannormally expected.
Key words: erosion, wear,hardened steel, dynamic hardness.
Correctionof the short-term forecast of high-voltage power consumption;53–62
Taivo Kangilaski and Vladimir Jaanimägi
Abstract. This paper describes andproves an algorithm for approximating the high-voltage power forecastedconsumption with a model function. The first and second derivatives are used todescribe the real consumption function. The algorithm is used in Eesti Energia AS for the analysis andtechnical management of large-scale transmission networks.
Key words: short-termforecast, high-voltage power consumption, function approximation.
CopyrightTransfer Agreement; 63
