Raskesti lõiketöödeldavate metallisulamite deformatsiooni kirjeldamine ja modelleerimine

Because of their excellent mechanical, physical and chemical properties even at elevated temperature, titanium and nickel-base alloys are the materials suitable for the production of several parts and components in the aerospace and power generation industry and for implants and tools in medical engineering. However, these materials are known as difficult-tomachine materials and in extreme cases up to 50% of the manufacturing costs are related to the machining. The current study is motivated by the idea of finding ways to improve the machinability of difficult-to-machine materials, as there have already been many projects aimed at advancing general material properties. Reduction of the production costs by the possible optimisation and higher efficiency of the cutting process should be of great interest for manufacturing companies. Chip formation is one of the key factors influencing the machinability of these materials. The aim of the research presented in this thesis was to investigate essential features of the mechanical behaviour of the materials under compression and relate them to the chip formation and cutting in general, as input for simulations. Titanium alloy Ti-15-3 was the primary target of the study, and the nickel-base Alloy 625 was also studied to an extent. List of the tasks to be solved to achieve the aim were: 1. Experimental verification of the chip formation process and chip morphology for Ti-15-3 alloy (I). 2. Experimental investigation of the mechanical behaviour in a wide range of strain rates and temperatures for Ti-15-3 alloy (II-V). Preliminary characterization of Alloy 625 in the region of high strain rates at room and elevated temperatures and low strain rates at room temperature. 3. Modelling mechanical behaviour in compression in a wide range of strain rates and temperatures. Modification and tuning of the model for reliable orthogonal cutting simulation results (II-V). 4. Experimental cutting force measurements and comparison with magnitudes seen with model implementations in the simulations (V). 58 Quick-stop experiments were performed to study the chip formation and morphology. For strain rate and temperature dependent dynamic plasticity characterization i.e. mechanical behaviour, the Split Hopkinson Pressure Bar technique was used together with industrial servohydraulic testing machines to perform compression tests. Ti-15-3 proved to have a considerable dependence on the strain rate and temperature. Johnson-Cook material model was chosen for modelling, as it is having a considerably clear format and reasonable number of parameters in the original format. In the vicinity of the chip formation in metal cutting, strains around 800% and temperatures of 900 °C are present. Meaningful extrapolative behaviour of the model is needed. Adiabatic heating was taken as a primary cause for chip segmentation and the original Johnson-Cook model was modified accordingly. In addition to chip morphology, cutting forces were compared in the experiment and simulation. Novel U-type specimen was tested with the SPHB technique. Results and conclusions: 1. Ti-15-3 proved to produce segmented chips in orthogonal cutting tests performed in the range of high cutting speed (>40 m/min). Development of adiabatic shear bands was also evident from the chips. 2. Ti-15-3 was characterised in a wide range of temperatures and strain rates under uni-axial compressive loading. Temperature and strain rate proved to have noticeable effect on the mechanical properties of Ti-15-3, with the effect of temperature being more significant than that of strain rate. Alloy 625 was characterized only in the high strain rate condition for different temperature. 3. No single unique set of original Johnson-Cook model parameters was found to be capable of describing the whole range of tested strain rates and temperatures. The empirical fitting model was used instead. 4. Adiabatic model modification proved to work for performing cutting simulations. A satisfactory match between physical results and simulations was achieved by comparing chip morphology and cutting forces.Masinaehituses, nagu näiteks energia- ja lennukitööstuses, kasutatakse masinaelemente ja detaile, mis peavad käitluses taluma suuri koormusi ning olema võimelised säilitama mehaanilist kandevõimet kõrgetel temperatuuridel või säilitama vastupidavuse keemiliselt agressiivses keskkonnas. Laastu tekkeprotsess ning laastu voolamine on lõiketöötlemise seisukohalt olulised tehnoloogilise protsessid. Põhilisteks probleemideks raskesti lõiketöödeldavate metallisulamite juures on pidev voolav laast ning lõikuri kiire kulumine. Esimene neist on takistuseks lõikeprotsessi automatiseerimisele, pidev voolav laast võib keerduda ning sattuda ebasobivalt lõikuri ja detaili vahele, kahjustades sellega lõikurit, mõjudes mittesoovitavalt töödeldava detaili geomeetrilistele kvaliteedile ning nõudes operaatorilt pidevat füüsilist sekkumist töötlemisel. Lõiketöödeldavuse parendamist võib kaaluda lähtudes erinevatelt alustelt, näiteks: – materjali omadusi muutes. Kirjandusest on tuntud rida tehnilisi ja tehnoloogilisi lahendusi, milles materjali struktuuris tekitatakse soovitult kunstlikke defekte. Selle eesmärgiks on muuta lokaalselt materjali omadusi nii, et suureneks tõenäosus laastu murdumiseks ning pidevalt voolav laast asenduks murdlaastuga. Viimane on soovitav tootmise optimeerimiseks; – muuta ja parendada lõikurite pinnakatete kulumiskindlust, misläbi suureneb vastupidavus kiirlõikerežiimi kasutamisel ning lõikuri kestvus; – arendada innovatiivseid lõiketehnoloogiaid. Klassikalisel lõikamisel on lõikur pidevas kontaktis toorikuga. Kirjandusest on tuntud ühe võimaliku arendusena ultraheli sagedusel võnkuv ja seega toorikuga vahelduvas kontaktis olev lõikur; – võimalikud parendused lõiketehnoloogias saavad tekkida lähtuvalt laastutekkeprotsessi põhjalikumast mõistmisest. Oluliseks teguriks on seejuures laastutüübi ning lõikejõudude kvantitatiivne hindamine. Otstarbekas on seejuures kasutada numbrilisi simulatsioone. Adekvaatsed ja füüsiliste tulemustega kokkulangevad simulatsioonid on head vahendid efektiivsema lõikeprotsessi leidmiseks. Antud doktoritöös käsitletakse lõiketöötlemise probleeme lähtuvalt viimases punktis esitatud ideedest. Konkreetselt võeti uurimise alla kaks teadaolevalt raskesti lõiketöödeldavat sulamit ning jõuti järelduste ja tulemusteni laastutekkeprotsessi simuleerimiste võimalikkusest ja kvaliteedist. 60 Selleks, et numbriline simulatsioon oleks korrektne ning lähtuks antud materjalile iseloomulikest parameetritest, peab sisendiks olema materjali mudel, mis sisaldab endas informatsiooni materjali mehaanikalistest omadustest seotuna uuritava protsessiga. Teadaolevalt on makrofüüsikalised tingimused vahetus laastutekkimise tsoonis ekstreemsed, suhteline deformatsioon suurusjärgus 800%, temperatuur kuni 900 °C ning deformatsiooni kiirused piirkonnas 105 s-1. Sellistel tingimustel laboratoorne katsetamine on praktiliselt komplitseeritud. See tähendab, et otseste katseandmete põhjal materjali füüsikalist käitumist kirjeldava matemaatilise mudelite koostamine on problemaatiline. Käesolevas doktoritöös püstitati eesmärgiks alustada materjali mudeli koostamisega võimalikult laia eksperimentaalsete andmete spektri põhjal. Katsete klassifitseerimise aluseks võeti suhtelise deformatsiooni kiirus ja katsekeha temperatuur. Suhtelise deformatsiooni osas viidi katsed läbi füüsikaliste piirideni, mille tingis olemasolev katsetehnika ja uuritav materjal. Kirjeldati uuritavate materjalide plastset deformatsiooni sõltuvalt suhtelise deformatsiooni kiirusest ja temperatuurist. Võrdluses mudeli põhjal simuleeritud laastu ja füüsikalise laastu vahel tuli koostada mudeli modifikatsioonid. Samuti seati eesmärgiks eksperimentaalselt uurida laastu morfoloogiat, lõikejõude ning nende vastavust mudeliga simuleeritule. Kirjeldatud metoodikat rakendati uurimistöös peamiselt titaani sulami Ti-15V3Cr3Al3Sn (Ti-15-3) puhul. Lisaks tehti eeluuringud niklisulamiga Alloy 625. Samaväärselt konkreetsete sulamite uurimisega oli eesmärgiks metoodika väljatöötamine ja selle parandamine. Töö eesmärgi saavutamiseks olid ettenähtud järgmised ülesanded: 1. Uurida eksperimentaalselt laastutekkeprotsessi Ti-15-3 materjalide puhul. Katsetused sooritada kiirlõikerežiimi piirkonnas < 40 m/min, teha kindlaks tekkiva laastu tüüp ning anda hinnang laastutüübi tundlikkusele lõikekiiruse suhtes (I). 2. Eksperimentaalselt uurida ja kirjeldada laias temperatuuride ja suhtelise deformatsiooni ettenähtud kiiruste vahemikus Ti-15-3 plastse deformatsiooni käitumist. Viia läbi eksperimentaalsed eeluuringud materjali Alloy 625 osas. Teha järeldused temperatuuri ja suhtelise deformatsiooni kiiruste mõjust (II-V). 3. Koostada matemaatiline mudel Ti-15-3 plastse deformatsiooni modelleerimiseks laias temperatuuride ja suhtelise deformatsiooni kiiruste 61 vahemikus. Arendada, modifitseerida mudelit saavutamaks kooskõla simulatsioonidega (II-V). 4. Eksperimentaalselt määrata lõikejõud uuritavatele materjalidele Hopkinsoni katseseadet kasutades (II-V). Laastutekkeprotsessi uurimine Ti-15-3 sulami osas viidi eksperimentaalselt läbi Braunschweigi Tehnikaülikooli materjalitehnikainstituudis Saksamaal. Katsetööd sooritati nn Quick Stop materjali ortogonaalse lõikamise katseseadmel. Nimetatud süsteemis kiirendatakse uuritavast materjalist katsekeha kuni see põrkub jäigalt kinnitatud lõikuri imitatsiooniga. Kokkupõrke tulemusena tekib laast. Seejärel uuriti laastu morfoloogiat valgus- ja elektronmikroskoopidega ning tehti järeldused saadud laastu tüübi kohta. Uuritavate materjalide plastset deformatsiooni uuriti eksperimentaalselt surveteimil. Madalatel kiirustel viidi katsetused läbi tööstuslikke servohüdraulilisi katsetussüsteeme kasutades. Kõrgemate suhteliste deformatsioonikiiruste uurimiseks rakendati Tampere Tehnikaülikooli materjaliteaduse osakonnas olevat Hopkinsoni katsetussüsteemi, mis võimaldab teostada katsetusi kiirustega kuni 105 s-1. Eksperimentaalselt uuriti protsessi kiiruste vahemikus 10-3 kuni 3·103 s-1 ja temperatuuride vahemikku toatemp kuni 1000 °C. Materjali mudeli koostamisel valiti aluseks Johnson-Cooki mudel. Kontrolliti selle sobivust kogu piirkonna modelleerimisel. Selgus, et vajalik on mudelit modifitseerida. Muudatuse aluseks võeti adiabaatilise soojenemise efekt ning sellest lähtuvalt pakuti simulatsioonidesse modifitseeritud mudel, kusjuures parameetrite määramiseks teisendati mõõdetud nö. adiabaatilised andmed arvutuslikult isotermilisteks. Katseliseks lõikejõudude hindamiseks viidi läbi U-kujuliste katsekehadega Hopkinsoni katsetussüsteemil

Soil sampling automation using mobile robotic platform

ArticleLand based drone technology has considerable potential for usage in different areas of agriculture. Here a novel robotic soil sampling device is being introduced. Unmanned mobile technology implementation for soil sampling automation is significantly increasing the efficiency of the process. This automated and remotely controlled technology is enabling more frequent sample collection than traditional human operated manual methods. In this publication universal mobile robotic platform is adapted and modified to collect and store soil s amples from fields and measure soil parameters simultaneously. The platform navigates and operates autonomously with dedicated software and remote server connection. Mechanical design of the soil sampling device and control software is introduced and discu ssed

DIG-MAN: Integration of digital tools into product development and manufacturing education

General objectives of PRODEM education. Teaching of product development requires various digital tools. Nowadays, the digital tools usually use computers, which have become a standard element of manufacturing and teaching environments. In this context, an integration of computer-based technologies in manufacturing environments plays the crucial and main role, allowing to enrich, accelerate and integrate different production phases such as product development, design, manufacturing and inspection. Moreover, the digital tools play important role in management of production. According to Wdowik and Ratnayake (2019 paper: Open Access Digital Tool’s Application Potential in Technological Process Planning: SMMEs Perspective, https://doi.org/10.1007/978-3-030-29996-5_36), the digital tools can be divided into several main groups such as: machine tools and technological equipment (MTE), devices (D), internet(intranet)-based tools (I), software (S). The groups are presented in Fig. 1.1. Machine tools and technological equipment group contains all existing machines and devices which are commonly used in manufacturing and inspection phase. The group is used in physical shaping of manufactured products, measurement tasks regarding tools and products, etc. The next group of devices (D) is proposed to separate the newest trends of using mobile and computer-based technologies such as smartphones or tablets and indicate the necessity of increased mobility within production sites. The similar need of separation is in the case of internet(intranet)-based tools which indicate the growing interest in network-based solutions. Hence, D and I groups are proposed in order to underline the significance of mobility and networking. These two groups of the digital tools should also be supported in the nearest future by the use of 5G networks. The last group of software (S) concerns computer software produced for the aims of manufacturing environments. There is also a possibility to assign the defined solutions (e.g. computer programs) to more than one group (e.g. program can be assigned to software and internet-based tools). The main role of tools allocated inside separate groups is to support employees, managers and customers of manufacturing firms focused on abovementioned production phases. The digital tools are being developed in order to increase efficiency of production, quality of manufactured products and accelerate innovation process as well as comfort of work. Nowadays, digital also means mobile. Universities (especially technical), which are focused on higher education and research, have been continuously developing their teaching programmes since the beginning of industry 3.0 era. They need to prepare their alumni for changing environments of manufacturing enterprises and new challenges such as Industry 4.0 era, digitalization, networking, remote work, etc. Most of the teaching environments nowadays, especially those in manufacturing engineering area, are equipped with many digital tools and meet various challenges regarding an adaptation, a maintenance and a final usage of the digital tools. The application of these tools in teaching needs a space, staff and supporting infrastructures. Universities adapt their equipment and infrastructures to local or national needs of enterprises and the teaching content is usually focused on currently used technologies. Furthermore, research activities support teaching process by newly developed innovations. Figure 1.2 presents how different digital tools are used in teaching environments. Teaching environments are divided into four groups: lecture rooms, computer laboratories, manufacturing laboratories and industrial environments. The three groups are characteristic in the case of universities’ infrastructure whilst the fourth one is used for the aims of internships of students or researchers. Nowadays lecture rooms are mainly used for lectures and presentations which require the direct communication and interaction between teachers and students. However, such teaching method could also be replaced by the use of remote teaching (e.g. by the use of e-learning platforms or internet communicators). Unfortunately, remote teaching leads to limited interaction between people. Nonverbal communication is hence limited. Computer laboratories (CLs) usually gather students who solve different problems by the use of software. Most of the CLs enable teachers to display instructions by using projectors. Physical gathering in one room enables verbal and nonverbal communication between teachers and students. Manufacturing laboratories are usually used as the demonstrators of real industrial environments. They are also perfect places for performing of experiments and building the proficiency in using of infrastructure. The role of manufacturing labs can be divided as: • places which demonstrate the real industrial environments, • research sites where new ideas can be developed, improved and tested. Industrial environment has a crucial role in teaching. It enables an enriched student experience by providing real industrial challenges and problems

Technology for the Production of Environment Friendly Tableware

From the point of view of environmental protection, it is reasonable to stop using disposable tableware that has been made from polluting plastics and to start using biodegradable and compostable products. Biodegradable and compostable tableware is significantly more environment and nature friendly than disposable plastic tableware and drinkware. The by-products (mostly bran) from the milling of wheat, corn and rice and palm leaves are used for the production of tableware. In the Baltic States, including Estonia, it is reasonable to use wheat bran, rye bran and buckwheat bran and the mixtures of these brans. The aim of this research was to provide the technical and technological know-how for the production of environment friendly disposable tableware and to verify the suitability of the new technological means. In order to achieve the aim, a punch and a die were modelled to produce disposable plates with desired parameters, materials and work modes for the material were chosen and, thereafter, the plates were produced from bran using a physical punch and die and using a suitable moulding mode or temperature and compression duration and using prescribed compressive forces. The mechanical properties like density and flexural strength of the moulded plates were determined