Integrated inpection of sculptured surface products using machine vision and a coordinate measuring machine

In modem manufacturing technology with increasing automation of manufacturing processes and operations, the need for automated measurement has become much more apparent. Computer measuring machines are one of the essential instruments for quality control and measurement of complex products, performing measurements that were previously laborious and time consuming. Inspection of sculptured surfaces can be time consuming since, for exact specification, an almost infinite number of points would be required. Automated measurement with a significant reduction of inspected points can be attempted if prior knowledge of the part shape is available. The use of a vision system can help to identify product shape and features but, unfortunately, the accuracy required is often insufficient. In this work a vision system used with a Coordinate Measuring Machine (CMM), incorporating probing, has enabled fast and accurate measurements to be obtained. The part features have been enhanced by surface marking and a simple 2-D vision system has been utilised to identify part features. In order to accurately identify all parts of the product using the 2-D vision system, a multiple image superposition method has been developed which enables 100 per cent identification of surface features. A method has been developed to generate approximate 3-D surface position from prior knowledge of the product shape. A probing strategy has been developed which selects correct probe angle for optimum accuracy and access, together with methods and software for automated CMM code generation. This has enabled accurate measurement of product features with considerable reductions in inspection time. Several strategies for the determination and assessment of feature position errors have been investigated and a method using a 3-D least squares assessment has been found to be satisfactory. A graphical representation of the product model and errors has been developed using a 3-D solid modelling CAD system. The work has used golf balls and tooling as the product example

The selected laser melting production and subsequent post-processing of Ti-6Al-4V prosthetic acetabular

&nbsp;Processing and post processing of human prosthetic acetabular cup by using 3D printing. The results showed using 3D printers leads to fabrication customized implants with higher quality.<br /

Laser-induced forward transfer (LIFT) of water soluble polyvinyl alcohol (PVA) polymers for use as support material for 3D-printed structures

The additive microfabrication method of laser-induced forward transfer (LIFT) permits the creation of functional microstructures with feature sizes down to below a micrometre [1]. Compared to other additive manufacturing techniques, LIFT can be used to deposit a broad range of materials in a contactless fashion. LIFT features the possibility of building out of plane features, but is currently limited to 2D or 2½D structures [2–4]. That is because printing of 3D structures requires sophisticated printing strategies, such as mechanical support structures and post-processing, as the material to be printed is in the liquid phase. Therefore, we propose the use of water-soluble materials as a support (and sacrificial) material, which can be easily removed after printing, by submerging the printed structure in water, without exposing the sample to more aggressive solvents or sintering treatments. Here, we present studies on LIFT printing of polyvinyl alcohol (PVA) polymer thin films via a picosecond pulsed laser source. Glass carriers are coated with a solution of PVA (donor) and brought into proximity to a receiver substrate (glass, silicon) once dried. Focussing of a laser pulse with a beam radius of 2 µm at the interface of carrier and donor leads to the ejection of a small volume of PVA that is being deposited on a receiver substrate. The effect of laser pulse fluence , donor film thickness and receiver material on the morphology (shape and size) of the deposits are studied. Adhesion of the deposits on the receiver is verified via deposition on various receiver materials and via a tape test. The solubility of PVA after laser irradiation is confirmed via dissolution in de-ionised water. In our study, the feasibility of the concept of printing PVA with the help of LIFT is demonstrated. The transfer process maintains the ability of water solubility of the deposits allowing the use as support material in LIFT printing of complex 3D structures. Future studies will investigate the compatibility (i.e. adhesion) of PVA with relevant donor materials, such as metals and functional polymers. References: [1] A. Piqué and P. Serra (2018) Laser Printing of Functional Materials. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. [2] R. C. Y. Auyeung, H. Kim, A. J. Birnbaum, M. Zalalutdinov, S. A. Mathews, and A. Piqué (2009) Laser decal transfer of freestanding microcantilevers and microbridges, Appl. Phys. A, vol. 97, no. 3, pp. 513–519. [3] C. W. Visser, R. Pohl, C. Sun, G.-W. Römer, B. Huis in ‘t Veld, and D. Lohse (2015) Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer, Adv. Mater., vol. 27, no. 27, pp. 4087–4092. [4] J. Luo et al. (2017) Printing Functional 3D Microdevices by Laser-Induced Forward Transfer, Small, vol. 13, no. 9, p. 1602553

Laser surface texturing of biomaterials: from conceptualization to implementation

Laser surface modification and more specifically laser surface functionalization is widely being considered as a way to efficiently give the surfaces of innovative high value products added or enhanced surface properties. The technology offers a number of desired advantages over competing technologies, of which: selectivity, relatively high processing speeds and the absence of waste or harmful by-products. Nevertheless, the full range of potential applications and suitable target materials is not yet explored, and some feasibility and implementation challenges remain open-ended concerns. With the limited literature available on laser surface texturing of cobalt chrome alloys, a prevalent implant material, the research presented in this thesis aims to address the suitability of this technology in that context and compare it with the current state-of-the-art in the orthopaedics industry. Furthermore, the transferability of the laser surface texturing process from 2D planar test samples to actual 3D parts will be assessed and the effects of 3D laser processing disturbances on the surface functionality evaluated. Finally, a method for laser processing complex surfaces productively is presented and validated on additively manufactured spherical parts

Scientific Advances in STEM: From Professor to Students

This book collects the publications of the special Topic Scientific advances in STEM: from Professor to students. The aim is to contribute to the advancement of the Science and Engineering fields and their impact on the industrial sector, which requires a multidisciplinary approach. University generates and transmits knowledge to serve society. Social demands continuously evolve, mainly because of cultural, scientific, and technological development. Researchers must contextualize the subjects they investigate to their application to the local industry and community organizations, frequently using a multidisciplinary point of view, to enhance the progress in a wide variety of fields (aeronautics, automotive, biomedical, electrical and renewable energy, communications, environmental, electronic components, etc.). Most investigations in the fields of science and engineering require the work of multidisciplinary teams, representing a stockpile of research projects in different stages (final year projects, master’s or doctoral studies). In this context, this Topic offers a framework for integrating interdisciplinary research, drawing together experimental and theoretical contributions in a wide variety of fields

FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance

International technical experts in durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The symposium focused on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure, criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and advanced approaches to resist corrosion and environmentally assisted fatigue

Pneumatic Tire

For many years, tire engineers relied on the monograph, \u27Mechanics of Pneumatic Tires\u27, for detailed information about the principles of tire design and use. Published originally by the National Bureau of Standards, U.S. Department of Commerce, in 1971, and a later (1981) edition by the National Highway Traffic Safety Administration (NHTSA), U.S. Department of Transportation, it has long been out of print. No textbook or monograph of comparable range and depth has appeared since. While many chapters of the two editions contain authoritative reviews that are still relevant today, they were prepared in an era when bias ply and belted-bias tires were in widespread use in the United States and thus did not deal in a comprehensive way with more recent tire technology, notably the radial constructions now adopted nearly universally. In 2002, it was preposed that NHTSA should sponsor and publish electronically a new book on passenger tires, under editorship of the University of Akron, to meet the needs of a new generation of tire scientists, engineers, designers, and users. This text is the outcome. The chapter authors are recognized authorities in tire science and technology. They have prepared scholarly and up-to-date reviews of the various aspects of passenger car tire design, construction and use, and included test questions in many instances, so that the book can be used for self-study or as a teaching text by engineers and others entering the tire industry

Optimisation of Macroscale Functional Surfaces Through Numerical Investigation of Naturally Occurring Bedforms

This thesis presents a detailed investigation into the potential of optimising the geometric profiles of macroscale grooves, to improve their drag reducing performance in internal laminar flow and spatially developing turbulent flow. The investigation explored whether the asymmetric profiles of naturally occurring sand ripples constitute an optimisation over the simple, symmetrical geometric profiles which have formed the typical focus for past investigations of macroscale grooves. In order to enable this analysis, the thesis developed and validated methodologies within the open source code OpenFOAM, which can overcome the bottlenecks associated with both modelling complex geometries in large-scale parametric studies, and implementing surface geometries into spatially developing turbulent flows. The first stage of the investigation developed a methodology for resolving laminar-turbulent transition in OpenFOAM using large-eddy simulation. To the authors knowledge, this work represents the first systematic validation and verification of resolved laminar-turbulent transition in OpenFOAM to investigate the combined effect of large-eddy simulation and controlled tripping. The results identify that a purely laminar boundary layer can be destabilised through imposing a period of psuedo-random, time-dependant fluctuations in the wall-normal velocity field at the wall. If the magnitude of these fluctuations match the maximum wall-normal velocity fluctuations in an equivalent boundary layer of equal thickness, then the initially period of two-dimensional instabilities is bypassed, and transition can be induced almost instantaneously downstream of the trip. Under these tripping conditions, the results expand the typical design criteria for large-eddy simulation spatial resolution, and show that typical design recommendations can sufficiently converge the flow resistance and shape factor by the start of the fully turbulent regime. Increasing this resolution by a factor of 2 achieve this convergence early on in the laminar-turbulent transitional regime. The second stage of the investigation involved an extensive parametric study of highly detailed sand ripple profiles within a periodic laminar channel flow. In all cases, the presence of both ripples and sinusoidal grooves had a negative impact on the flow resistance, typically due to a reduction in viscous forces being balanced out by the creation of a larger pressure force. The higher order details of the geometric profiles did not have a significant impact on the flow resistance, even when such details had a significant impact on promoting or delaying flow separation. The details of the geometric profile only became significant for three-dimensional ripples, when applied with a sufficient depth and and Reynolds number to manipulate the bulk flow field towards the centre of the channel, and direct high velocity flow from the centre towards the crests of the ripple profiles. The final stage of the investigation applied simplified sand ripple profiles into a wall-resolved spatially developing turbulent boundary layer, through the novel incorporation of a split-hexahedral mesh, through OpenFOAM's snappyHexMesh utility. Whilst ripples with a depth of $5\%$ of their wavelength had a negligible impact on flow resistance, deeper ripples ($15\%$) produced an increase in flow resistance which was independent of the growing ratio between boundary layer thickness and ripple depth. The local distribution of turbulent velocity fluctuations was consistent with known drag reducing phenomenon, with amplified spanwise velocity fluctuations over the shear stress spike approaching the crest, and amplified streamwise velocity fluctuations accompanying the free-shear region of flow separation downstream of the crest. It was in this free-shear region, that the streamwise resolution had the greatest impact on the accuracy of the local wall shear stress. The present approach confirms the capabilities of split-hexahedral meshes to efficiently balance the varying requirements of spatial resolution in near-wall and free-stream regions, regardless of the geometric surface profile

The effects of microstructure and microtexture generated during solidification on deformation micromechanism in IN713C nickel-based superalloy

Nickel-based superalloy IN713C produced by investment casting method are used for turbine blade of turbocharger in modern vehicles. IN713C alloy possesses good strength, fatigue, creep and high temperature oxidation resistance that make the alloy suitable to be used in harsh service environment such as in the heating part of turbocharger. However, this material suffers from microstructure and microtexture heterogeneity produced during solidification. This microstructure heterogeneity across the component will inevitably give rise to local stress and strain accumulation which may facilitate crack initiation and affect crack propagation. Fatigue, both LCF (Low Cycle Fatigue) and HCF (High Cycle fatigue) are the common failure modes of turbine blade component in turbocharger. It is of industrial and academic interests to identify and classify the features of fracture surface of each failure mode. The necessity of optimisation of fatigue property for the newly developed turbocharger component parts is becoming critical and a fundamental research for understanding fatigue deformation micromechanism and the influence of microstructure (dendrite structure, carbides / oxidised carbides, grain size, etc.) and microtexture (individual crystallographic orientation, cluster of grains, etc.) is required. In the current investigation, LCF and HCF fatigue tests are conducted on real turbine blades as wel as on bars produced via investment casting. Various microstructure characterisation tools were used to identify the deformation micromechanics during LCF and HCF fatigue conditions. The results showed that in real turbine blades where there are much less casting defects than in the testing bar, the fatigue crack initiated from blade surface and crack propagation process was mainly dominated by oxidation-assistant process with oxidised carbides during LCF test. During the late stage of crack propagation, the interdendrite area was found to deform differently from the surrounding area to accommodate accumulated strain heterogeneity. Whilst for HCF, facet was initiated from slip planes with the highest Schmid factor and assisted by small porosity in most cases. As for the fatigue tests conducted on test bars produced via investment casting, the dendrite structure played a vital role in crack propagation mechanism. Based on the observations throughout this study, a concept of ‘crack propagation unit (CPU)’ was proposed. From this proposed micro deformation mechanism, a new perspective of Hall-Patch effect of small grain size in casting alloys (containing dendrite structure) was further elucidated duirng both LCF and HCF. Finally, solidification trials were performed to study the exact correlation between solidification cooling rate and microstructure evolution including grain size and structure, gamma prime, carbides and other phases