Technological and design aspects of the processing of composites and nanocomposites. Volume III

Processing of composites and nanocomposites materials constitutes nowadays an important area of research given the growing interest by these types of materials due to its singular properties, namely in what concerns technological and design aspects. This monography presents the developments taking place in the framework of the NEWEX project during the fourth year of its duration, which is a sequence of other two previous monographies. The main objective of the NEWEX project entitled “Investigation and development of a new generation of machines for the processing of composite and nanocomposites materials” is the exchange of researchers from the institutions participating in the project. Another important objective consists in develop permanent international and inter-sector collaboration between academic research centres (Lublin University of Technology, Technical University of Kosice, University of Minho) and industrial organizations (Zamak-Mercator LLC and SEZ-Krompachy a.s., Dirmeta UAB). The contents of this book reflects the work done within the NEWEX project. It starts by presenting the results obtained concerning new concepts for the extruder parts studied and the manufacturing of those extruder parts. Then, some approaches for modelling and optimizing and to study experimentally the process are described, which includes mixing analysis and monitoring. Finally, a practical and state-of-theart application of the extrusion is identified, namely 3D printing. It is expected that the nine chapters of this monography be useful to the industry of plastics processing and for scientific organisations dealing with technologies and processing of polymer composites and nanocomposites

Investigations into AFM-tip based vibration-assisted nanomachining

The recent global shortage of microchips highlighted the exponential increase in demand in the past three decades. It also showcased the fragile supply chain and its vulnerability to bottlenecking. Hence, it became evident that there is a need to explore additional manufacturing methods for miniature device manufacturing. The use of the atomic force microscope (AFM) has gained traction due to it being more environmentally friendly and its lower cost of operation when compared to other nanofabrication methods. The use of the AFM tip as a cutting tool is well established, especially when silicon workpieces are machined. In addition, the introduction of vibrations to the nanomachining process was found to provide improvements. However, the majority of research looks into silicon, with copper being investigated to a much lesser degree. Hence, this thesis investigates AFM tip-based vibration-assisted nanomachining of single crystal copper theoretically and experimentally. Following the introduction, a literature review of nanomachining is done, followed by a review regarding Atomic Force Microscopy. After that, conventional and ultraprecision machining are reviewed. Stagnation zones that play an important role at micro and nanoscales are examined. Additionally, vibration-assisted nanomachining and its various methods are explained. Also, the advantages of vibration-assisted nanomachining over conventional nanomachining are discussed. Finally, the analysis necessary for the determination of the one-direction vibration-assisted nanomachining parameter is done. Equations that govern the vibrations are explained in detail, including values extraction necessary for selecting the various frequencies and amplitudes used during experimentation. Chapter 3, in turn, studies the material deformation mechanisms at different scales and how they differ. Since the motion of dislocations is common among all size scales, it is analysed in addition to slip and the resolved shear stress. Four categories are agreed upon in the research community and are studied: (i) atomic scale, (ii) nanoscale, (iii) microscale (iv) macroscale. A brief discussion of the atomic scale is done with the inverse Hall-Petch effect on the grain size being mentioned. The nanoscale is studied in most detail due to its close relation to the experimental work of this thesis, with emphasis on nucleation of dislocations and the variations between metals and macroscopically brittle materials like silicon. After that, the microscale is discussed with its most prominent plastic deformation theory, referred to as the strain gradient plasticity (SGP). Also examined is the applicability of SGP at the nanoscale. In addition, the macroscale plastic deformation is studied, including classical theories, which in turn is followed by hardness analysis. Fatigue and specifically low-cycle fatigue are analysed then, with the impact of the size scale on the latter also reviewed. Finally, an analytical study of an experiment similar to one done in this thesis wherein proof is provided regarding the prominence of dislocation nucleation in the nanomachining of copper. As for Chapter 4, characterisation of the AFM tip shape and condition is performed. Following an introduction to tip characterisation, a review on how the shape of the tip impacts AFM operations, including nanomachining, is carried out. Methods including in-situ and ex-situ used to characterise the tip are then showcased. Later, images using the SEM are taken of the tip and later processed for tip shape extraction. Consequently, a power-law function is used to characterise the tip shape using a non-integer bluntness value. Bluntness values were extracted for both vertical and 12° tilt angle orientation, where the latter is observed in practice. Afterward, a force-displacement experiment of the same tip is done to validate the results obtained from the SEM images, using the Borodich rescaling formula. The bluntness impact of the work of adhesion and pull-off force is analysed using values extracted during experimentation, in addition to other arbitrary but practical non-integer values. In the end, an analytical study is done to investigate the factors affecting the effective rake angle. Such angle plays a vital role in the nanomachining process, including forces exerted and surface quality. However, the tip bluntness, depth of penetration, and tilt angle all impact this angle to varying degrees. Chapters 5 and 6 cover the vibration-assisted nanomachining experimental work and consequent results. Chapter 5 discusses the test setup and all the necessary equipment to complete the experiment. The cutting conditions and parameters of the tests are discussed, such as the three different amplitudes and frequencies of the vibrations resulting in nine combinations plus a conventional test used as reference. Parameters also include the cutting velocity and direction in each test and the data acquisition software settings. The chapter then briefly explains the imaging and scanning techniques used to investigate the resultant grooves. Chapter 6 discusses the outcomes and results of the experiment. The chapter starts by presenting the first test's results with no vibrations induced. Following that, the nine tests with vibrations induced are presented with specific parameters compared to the first test. These include groove depths, pile-up heights, surface roughness, chip formation, and live signal acquired from AFM nanomachining experiment. The results are then discussed, highlighting the cases where the induced vibrations did provide improvements, where they did not, and where no significant changes are noticed. Later, trends observed during testing are presented. Finally, evaluation and comparisons between the results and what is available in the research community, including theoretical and analytical studies with consequent conclusions, are presented. Finally, Chapter 7 concludes with the knowledge gaps addressed in this thesis, in both the characterisation of AFM tips as well as the optimisation of AFM tip-based vibration-assisted nanomachining and followed by a summary of the work done in this thesis and conclusions encompassing work done across the thesis. Then, suggestions regarding the additional future work that can be done to expand and improve upon what was done throughout this thesis

Active thermography for the investigation of corrosion in steel surfaces

The present work aims at developing an experimental methodology for the analysis of corrosion phenomena of steel surfaces by means of Active Thermography (AT), in reflexion configuration (RC). The peculiarity of this AT approach consists in exciting by means of a laser source the sound surface of the specimens and acquiring the thermal signal on the same surface, instead of the corroded one: the thermal signal is then composed by the reflection of the thermal wave reflected by the corroded surface. This procedure aims at investigating internal corroded surfaces like in vessels, piping, carters etc. Thermal tests were performed in Step Heating and Lock-In conditions, by varying excitation parameters (power, time, number of pulse, ….) to improve the experimental set up. Surface thermal profiles were acquired by an IR thermocamera and means of salt spray testing; at set time intervals the specimens were investigated by means of AT. Each duration corresponded to a surface damage entity and to a variation in the thermal response. Thermal responses of corroded specimens were related to the corresponding corrosion level, referring to a reference specimen without corrosion. The entity of corrosion was also verified by a metallographic optical microscope to measure the thickness variation of the specimens

Laser powder bed fusion of cemented tungsten carbide cutting tools

Thesis (PhD)--Stellenbosch University, 2022.ENGLISH ABSTRACT: Cemented carbides are extremely hard, wear resistant materials, and one of the most widely used tool materials in numerous manufacturing industries. Metal cutting tools are commonly manufactured from cemented carbides using standard powder metallurgy processes such as the press and sinter process. The tooling market is highly competitive and the companies with the best research and development departments have the competitive advantage when it comes to cutting edge technology. However, historically, the development process for a new cutting tool or production technology is a lengthy and costly venture. The use of laser powder bed fusion (L-PBF) for research, development, and small-batch production of cemented tungsten carbide cutting tools has not been extensively reported, and commercialisation does not seem apparent as yet. While the usage of L-PBF to produce cutting tools may be beneficial to advancing cutting tool technology, the process has many inherent drawbacks that affect part quality. However, there are many changes to the current L-PBF process that can be investigated to improve the final quality of L-PBF-produced tools before post-processing. The successful application of L PBF technology could help develop and manufacture cutting tools at an improved rate. The aim of this study was to determine and manage the influences of certain factors encountered during L-PBF of tungsten carbide cobalt (WC-Co) and their effects on specific cutting tool properties and cutting performance to produce L-PBF cutting tools that could be comparable to a conventionally produced tool. To accomplish this, three powders were analysed and investigated for their use in the L-PBF process. Then, characterisation of an existing cutting tool was performed to be used as a quality benchmark for L-PBF cutting tools. After a reasonable understanding of powders and conventional cutting tools was obtained, single track scans were performed on a tool steel base plate to understand adhesion and the feasibility of using a conventional base plate. The next stage of the study involved understanding the effects of different laser parameters and scanning strategies on the track morphology, density, hardness, and cobalt content of L-PBF produced WC-12wt%Co samples. Various parameter optimisation methods and strategies were tested and L-PBF-produced cutting tools were utilised in preliminary cutting tests to determine their cutting ability and to deduce which factors had the greatest effects on cutting contact time. The L-PBF scanning strategy was observed to be the most significant factor for successful cutting operations. A diagonal raster strategy with an 80-degree alternating rotation produced the best cutting inserts for the specific insert geometry and grade. Verification WC-12wt%Co inserts were produced with L-PBF for final cutting tests. These inserts were comparable to conventionally produced tungsten carbide inserts with respect to cutting performance indicators such as contact time and workpiece surface roughness. On average, after roughly 16M30S contact time, the L-PBF cutting tools exhibited 0.7 mm maximum flank wear versus 0.4 mm for similar conventional inserts. These results suggest that L-PBF could, one day, be a viable solution for research, developments, and small-batch production of WC-Co cutting tools.AFRIKAANSE OPSOMMING: Sinterkarbiede is uiters hard, slytasiebestand en een van die gereedskapsmateriale wat die algemeenste in talle vervaardigingsbedrywe gebruik word. Metaalsnygereedskap word gewoonlik met behulp van standaard poeiermetallurgieprosesse, soos die pers- en sinterproses, uit sinterkarbiede vervaardig. Die werktuigmark is baie mededingend en ondernemings met die beste navorsingen ontwikkelingsdepartemente, het die mededingende voordeel as dit by die nuutste tegnologie kom. Histories is die ontwikkelingsproses vir ʼn nuwe snybeitel of produksietegnologie egter ʼn lang en duur proses. Die gebruik van laser- poeierbedsamesmelting (L-PBF) vir navorsing, ontwikkeling en kleinskaalproduksie van gesementeerde-wolframkarbiedsnygereedskap is nog nie wyd gerapporteer of gekommersialiseer nie. Hoewel die gebruik van L-PBF voordelig vir die bevordering van snygereedskaptegnologie kan wees, het die proses baie inherente nadele wat die gehalte van die onderdele beïnvloed. Daar is egter baie veranderinge aan die huidige L-PBF-proses wat ondersoek kan word om die finale gehalte van L-PBF-vervaardigde gereedskap voor ná-vervaardiging te verbeter. Die suksesvolle toepassing van L-PBF-tegnologie kan help om snygereedskap vinniger te ontwikkel en te vervaardig. Die doel van hierdie studie was om die invloed van sekere faktore tydens die L-PBF van wolframkarbied-kobalt (WC-Co), en die uitwerking daarvan op spesifieke snygereedskapseienskappe en -snyprestasie te bepaal en te bestuur, om uiteindelik L-PBF-snygereedskap te vervaardig wat met ʼn konvensioneel vervaardigde werktuig vergelykbaar is. Om dit te bewerkstellig, is drie poeiers vir gebruik in die L-PBF-proses ontleed en ondersoek. Vervolgens is karakterisering van ʼn bestaande snybeitel uitgevoer om as ʼn gehaltenorm vir L-PBF-snygereedskap te dien. Nadat ʼn redelike begrip van poeiers en konvensionele snygereedskap verkry is, is enkelbaanskanderings op ʼn basisplaat van gereedskapstaal uitgevoer om die aanklewing en dus die haalbaarheid van die gebruik van ʼn konvensionele staalbasisplaat te ondersoek. Die volgende fase van die werk het die bestudering van die effekte van verskillende laserparameters en skanderingstrategieë op die baanmorfologie, digtheid, hardheid en kobaltinhoud van L-PBF geproduseerde WC-12wt%Co-monsters behels. Verskeie parameter-optimaliseringsmetodes en - strategieë is getoets en L-PBF-vervaardigde snygereedskap is in voorlopige snytoetse gebruik om hulle snyvermoë te bepaal en af te lei watter faktore die grootste effek op die snykontaktyd het. Waarneming het aangedui dat die L-PBF-skanderingstrategie die belangrikste faktor vir suksesvolle snywerk is. ʼn Diagonale rasterstrategie met ʼn wisselrotasie van 80 grade het die beste snyinvoegstukke opgelewer vir die spesifieke invoegstukgeometrie en -graad wat bestudeer is. Verdere WC-12wt%Co-snyinvoegstukke is ter bevestiging vir finale snytoetse met behulp van L PBF vervaardig. Hierdie invoegstukke was met betrekking tot snyprestasie, soos kontaktyd en oppervlakruheid van die werkstuk, met konvensioneel vervaardigde wolframkarbied-invoegstukke vergelykbaar. Na ongeveer 16M30S se kontaktyd vertoon die L-PBF-snybeitel ʼn gemiddelde flankslytasie van 0.7 mm teenoor 0.4 mm vir soortgelyke konvensionele invoegstukke. Hierdie resultate dui daarop dat L-PBF in die toekoms wel ʼn lewensvatbare oplossing vir die navorsing, ontwikkeling en kleinskaalproduksie van WC-Co-snygereedskap kan wees.Doctora

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Tribological Behavior of Functional Surface: Models and Methods

Material loss due to wear and corrosion and high resistance to motion generate high costs. Therefore, minimizing friction and wear is a problem of great importance. This book is focused on the tribological behavior of functional surfaces. It contains information regarding the improvement of tribological properties of sliding elements via changes in surface topography. Tribological impacts of surface texturing depending on the creation of dimples on co-acting surfaces are also discussed. The effects of various coatings on the minimization of friction and wear and corrosion resistance are also studied. Friction can be also reduced by introducing a new oil

Advances on Mechanics, Design Engineering and Manufacturing III

This open access book gathers contributions presented at the International Joint Conference on Mechanics, Design Engineering and Advanced Manufacturing (JCM 2020), held as a web conference on June 2–4, 2020. It reports on cutting-edge topics in product design and manufacturing, such as industrial methods for integrated product and process design; innovative design; and computer-aided design. Further topics covered include virtual simulation and reverse engineering; additive manufacturing; product manufacturing; engineering methods in medicine and education; representation techniques; and nautical, aeronautics and aerospace design and modeling. The book is organized into four main parts, reflecting the focus and primary themes of the conference. The contributions presented here not only provide researchers, engineers and experts in a range of industrial engineering subfields with extensive information to support their daily work; they are also intended to stimulate new research directions, advanced applications of the methods discussed and future interdisciplinary collaborations

Numerical analysis of fatigue crack growth in welded joints with multiple defects

In the case of welded steel structures (such as pressure equipment), welded joints are often critical location for stress concentrations, due to different mechanical properties and chemical composition compared to the parent material, and due to changes in geometry. In addition, the presence of imperfections (defects) in welded joints can contribute to the increase in local stress, resulting in crack initiation. Recently, standards that are related to acceptable dimensions of various types of defects in welded joints started taking fatigue loading into account as well. For the purpose of this research, a 3D numerical model was made, of a welded joint with different types of defects (linear misalignment and a crack in the weld metal), based on the previous work, which involved static loading of the same specimen. In this case, fatigue was taken into account, and the simulation was performed using ABAQUS software, as well as Morfeo, an add-on used for determining the fatigue behaviour of structures via XFEM (extended finite element method). The welded joint was made using steel P460NL1 as the parent material, and EPP2NiMo2 wire was used for the weld metal. An additional model was made, whose defects included a crack and an overhang. Fatigue crack growth analysis was performed for this model as well, and the results for stress intensity factors and stress/strain distribution were compared in order to obtain information about how different defects can affect the integrity of a welded joint

Using the fracture mechanics parameters in assessment of integrity of rotary equipment

In this paper is presented the principle of application of fracture mechanics parameters in determining the integrity of rotary equipment. The behavior of rotary equipment depends on presence of cracks and basically determines the integrity and life of such equipment. The locations of stress concentration (i.e. radius changes) represent a particular problem in rotary equipment, and they are the most suitable places for the occurrence of microcracks i.e. cracks due to fatigue load. This problem is most common in the shaft of relatively large dimensions, for example, turbine shafts in hydropower plants made of high-strength carbon steel with relatively low fracture toughness, and relatively low resistance to crack formation and growth. Having in mind that rotary equipment represents the great risk in the exploitation, whose occasional failures often had severe consequences, it is necessary detail study of their integrity. For this purpose, it is necessary application of parameters of linear-elastic fracture mechanics, such as stress intensity factor, which range defines the rate of crack growth (Parisian law), and its critical value (fracture toughness) determines the critical crack length. The procedures for determining the critical crack length will be described using the fracture mechanics parameters