This thesis is concerned with the microstructures and wear characteristics of eight ceramic tool materials which have been, or are currently, commercially available as indexable inserts for lathe tools. Two of the materials are alumina-based and the other six are derived from silicon nitride. The opening chapters of the thesis outline the essential features of metal cutting, the properties required of a good tool material, the development of ceramic tools and possible wear behaviour as discussed in the literature. Subsequent chapters describe the experimental procedures adopted in this work and both present and discuss the results obtained. The eight ceramics have been microstructurally characterised by the use of X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. Machining tests have been performed using five common workpiece materials, spanning a range of nickel and iron contents: mild steel, stainless steel, two nickel-based superalloys and commercial purity nickel. The two alumina-based materials were found to wear in a different, less severe manner to the silicon nitride-based tools. The mechanical response to surface contacts was established using identation techniques to give hardness (as a function of contact size and temperature) and fracture toughness (as a function of temperature) to test the correlation between these properties and wear behaviour, but this proved to be unfruitful. Since other classes of tools can be subject to dissolution/diffusion wear and little is known about the compatability of these ceramics with molten metals, a second type of investigation was instigated. The involved immersing pieces of ceramic in samples of molten workpiece materials, followed by cooling, sectioning and examining in the scanning electron microscope. Vast differences in the behaviour of the materials were observed and results from these tests correlated well with machining data, indicating the importance of high temperature stability with respect to the hot workpiece. Drawing on the experimental observations made during the project, the thesis concludes with suggestions for improving and optimising ceramic tool materials for turning purposes.

Baigiamajame magistro darbe ištirta skystųjų kristalų (cholesterolio stearatas) priedų prie tepimo ir aušinimo skysčio (TAS) įtaka kietlydynio peilio nudilimui ir apdirbto paviršiaus šiurkštumui tekinimo operacijoje. Ištirtas sriegiklio pasipriešinimo momento kitimas sriegiant skyles rankiniais sriegikliais, kai sriegikliai tepami skystaisiais kristalais ir konsistentiniu tepalu. Paviršiaus šiurkštumo tyrimai buvo atlikti tekinant 45 plieninį strypą: pastūma – 0,1 mm/aps., pjovimo greitis buvo keičiamas nuo 85 iki 267 m/min, o cholesterolio stearato kristalų koncentracija emulsijoje – nuo 0,1 iki 0,5 %. Eksperimentas buvo atliekamas pagal dviejų veiksnių ortogonalinį eksperimento planą. Rezultatai pateikti kaip tekinto paviršiaus šiurkštumo parametro Ra priklausomybė nuo pjovimo greičio ir cholesterolio stearato koncentracijos TAS. Peilio užpakalinio paviršiaus nudilimas buvo nustatomas esant tokiems režimams: pjovimo greitis 160 m/min, pastūma 0,1 mm/sūk., aušinimas – mineralinė emulsija BLASOCUT ir ta pati emulsija su 0,1% cholesterolio stearato. Rezultatai pateikti kaip dilimo priklausomybės nuo įrankio kelio grafikai. Nustatyta, kad skystųjų kristalų priedai pagerina įrankio patvarumą ir sumažina įrankio dilimą. Taip pat nustatyta, kad sriegiklio pasipriešinimo momentas mažėja iki 1,1 karto, tepant jį skystaisiais kristalais, lyginant su tepimu konsistentiniu tepalu. Darbą sudaro keturios dalys: įvadas, literatūros analizė, eksperimentiniai tyrimai, išvados. Darbo... [toliau žr. visą tekstą] / The influence of the liquid crystals (cholesteryl stearate) additives on technological properties of the cutting fluid is investigated in the master‘s thesis. Influence of the presence of the liquid crystals in cutting fluid on wear of the carbide lathe tool and roughness of the turned surface is established. Also changes in the cutting torque of the hand tap in the tapping operation were obtained when tap were lubricated with grease and liquid crystals. Research of the surface roughness was done at the following conditions: tool feedrate – 0.1 mm/rev., cutting speed was varied from 85 to 267 m/min and concentration of the liquid crystals was varied from 0.1 to 0.5%. Experimental research was performed by means of two factors second order orthogonal design. The results presented as graphs of dependence of average roughness of turned surface on cutting speed and concentration of the liquid crystals in the coolant. The wear of carbide tool relief face was established under following conditions: cutting speed 160 m/min, feedrate – 0.1 mm/rev., cutting fluid – mineral coolant BLASOCUT with 0.1% and without liquid crystals additives. The results are presented as graphs of dependence of tool wear on the length of tool path. It is established that liquid crystals additive reduces tool wear and increase tool life. It is also established, that cutting torque of the hand tap reduces about 1.5 times when it is lubricated with liquid crystals, as compared with lubrication with... [to full text]

Lathes are frequently used in industrial production. It is an important parameter to calculate the force exerted by the cutter head on the raw material. Knowing the force acting on the cutting tool will aid in predicting the displacement of the cutting edge as well as predict displacement of the workpiece. The main purpose of this paper is to find a way to calculate the force exerted on the cutting tool tip. The magnitude of the tooltip force is estimated without the use of a force sensor. Instead, strain sensors are used to collect strain signals, and acceleration sensors are used to collect acceleration signals. Combine these two signals to calculate the magnitude of force. The force-strain frequency response function is calculated. The force-strain FRF acts as a bridge connecting force and strain signals. Calculate the input force signal on the cutting tool tip using the strain signal. In this way, is available to obtain the force time-image. Changes in force can be predicted by looking for force-time laws. In this thesis using MATLAB software for simulation and actual experimental measurements. Verify the reliability of the calculation method. The method and MATLAB code for calculating force-strain FRF are researched and written. Simulate the cutting tool input-output model in MATLAB. Combined with the actual experimental measurement results, the accuracy and limitations of this calculation method are analyzed. Discuss directions for future work.

Магистерская диссертация выполнена на тему: «Исследование износа и стойкости токарных резцов с алмазоподобным покрытием». Расчётно-пояснительная записка содержит 94 листа, 86 рисунков, 6 таблиц, 23 источника, 1 приложение. Объектом исследования данной работы являются токарные резцы с алмазоподобным покрытием. Цель работы – определить наиболее благоприятные условия работы токарных резцов с алмазоподобным покрытием. В результате выполнения работы были проведены исследования износа алмазоподобного покрытия на токарных резцах, построены и проанализированы графики зависимостей этих износов. Проведен анализ полученных результатов и выдвинута гипотеза об еще одной возможной причине разрушения покрытия, в то время как остальные известные причины устранены. Разработаны конструкции токарных резцов и проведено исследование предлагаемой гипотезы. По результатам исследования проведен расчет прочности и подтверждена предлагаемая гипотеза. / The master's dissertation is carried out on the topic: "Investigation of wear and resistance of cutting tools with a diamond-like coating". The settlement and explanatory note contains 94 sheets, 86 figures, 6 tables, 23 sources, 1 attachment. The object of research in this work is diamond-coated lathe tools. The purpose of the work is to determine the most favorable working conditions for lathe tools with a diamond-like coating. In the course of the work, the study of the wear of the diamond-like coating on lathe tools at various cutting modes was carried out, the graphs of the dependences of these wear in time were built and analyzed. The analysis of the results obtained is carried out and a hypothesis is put forward about another possible cause of the destruction of the coating, while the other known causes have been eliminated. To confirm the hypothesis, the designs of lathe tools were developed and a study was carried out. According to the results of the study, the strength calculation was carried out, the proposed hypothesis was confirmed.