Alistair Speidel

Alistair Speidel
University of Nottingham | Notts · Department of Mechanical, Materials and Manufacturing Engineering

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36
Publications
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482
Citations

Publications

Publications (36)
Article
Deep-eutectic fluids (DEFs) are a novel class of materials that, to date, have been generally used in a single-phase (liquid) for a growing number of applications (e.g., extraction, catalysis, synthesis, etc). In contrast, we present a novel approach to utilise the advantages associated with dual-phase control of DEFs. In this study, we exploit the...
Article
Electrical discharge machining (EDM) is a widely used manufacturing process for machining hard or high melting point metals. A characteristic feature of this process is a brittle, porous and rough recast layer on machined surfaces, which undermines integrity and limits its applications. Previous attempts to remove the recast have increased process...
Article
Electrochemical jet processing encompasses a group of non-contact and ‘tool-less’ technologies, relying on localised electrolyte jets to affect changes to the workpiece in a site-specific manner. This is achieved without thermally or mechanically modifying the underlying material giving rise to a unique class of manufacturing methods. Jet technique...
Article
In laser powder bed fusion, unconsolidated metal powder on the build plate tends to comprise a proportion of oxidised powder after repeated use. This is generally caused by the generation of oxidised spatter particles during processing which can contaminate the powder bed, and be incorporated into future builds, ultimately undermining part integrit...
Article
Measurement of surface geometry is an essential activity in engineering, which is commonly performed by tracing the surface of interest with a mechanical or an optical probe. This is generally performed ex-situ in laboratories designed for metrology. However, inline measurement represents an opportunity to unlock significant efficiency gains throug...
Article
In laser powder bed fusion (LPBF), recovered unfused powder from the powder bed often degrades upon sequential processing through mechanisms like thermal oxidation and particle satelliting from ejected weld spatters and particle-laser interactions. Given the sensitivity of LPBF performance and build quality to powder properties, spent powder is gen...
Article
Cooling hole blockages in gas turbine blades can occur during operation, detrimentally reducing performance and resulting in premature removal from service. Here, electrical discharge machining (EDM) is used to unblock fine holes, which have been obstructed with a mixture of both conductive and non-conductive contaminants representative of post-ser...
Article
Directed energy deposition (DED) is an additive manufacturing process capable of creating parts or coatings from powder or wire feedstocks, and may be adapted to use machining chips. Re-use of steel chips as opposed to landfilling or even recycling, has implications for CO2 emission savings. This is particularly the case of like-for-like replacemen...
Article
The high optical reflectance of Cu at near-infrared wavelengths narrows the process window to fabricate Cu parts by laser powder bed fusion (LPBF). Coating powders with optically absorptive materials has been investigated to improve processability and enhance part properties. However, given the intense heat localization and thin coating layers rela...
Article
Full-text available
Material removal operations play a pivotal role in the manufacture of key components, required for engineering systems to operate safely and efficiently under ever more advanced functional requirements and over extended life cycles. To further step up the loading capability of machined parts, fundamental understanding of how of machining-induced fe...
Article
Additive manufacturing is an increasingly important counterpart to subtractive and constant volume manufacturing methods, however metal powder bed fusion methods often suffer from poor surface quality dominated by adhered unfused powder at the near-surface. Finishing steps are often required before part use in many applications, for example in aero...
Article
Full-text available
The surface integrity of machined metal components is critical to their in-service functionality, longevity and overall performance. Surface defects induced by machining operations vary from the nano to macro scale, which cause microstructural, mechanical and chemical effects. Hence, they require advanced evaluation and post processing techniques....
Article
Full-text available
Surface preparation for advanced materials inspection methods like electron backscatter diffraction (EBSD) generally involve laborious and destructive material sectioning and sequential polishing steps, as EBSD is sensitive to both sample topography and microstrain within the near-surface. While new methodologies, like focussed ion beam and femtose...
Article
Full-text available
Curved toolpaths challenge accurate electrochemical jet processing due to resulting distortion of the cut profile. A more elaborate path planning approach is required to mitigate these negative effects. A 3-dimensional process model is presented here, to predict the resulting surface geometry. This is applied to simulate machining of curved channel...
Article
Full-text available
In this study, we describe a new methodology to create complex coatings with functionally graded compositions, using electrochemical jet processing (EJP). Cu/Zn alloy coatings were electrodeposited, in a layer-by-layer manner, onto steel substrates through resin masks created with a desktop 3D printer. By adapting the electrolyte composition throug...
Article
Micro-structures on metal surface can be realized with high precision and good surface quality by air-shielding electrochemical micromachining (AS-EMM). However, fundamental understanding of the process and particularly interaction between the electrolyte jet and the surrounding gas flow is limited. In order to obtain the material dissolution proce...
Article
When appraising the performance of titanium alloys for corrosion resistance in halide environments researchers have well understood pitting and growth mechanisms through electrochemical corrosion. This knowledge is yet to be exploited for the purpose of electrochemical jet processing, a versatile and selective machining technique that is ideal for...
Article
This work demonstrates for the first time an augmentation to electrolyte jet processing which allows plasma electrolytic oxidation to be undertaken. Using a sequential process it is possible to produce micro features (≈500 μm width)with a resolution limited only by nozzle geometry but with significant enhancement to substrate surface properties. He...
Article
A new powder spheroidisation process has been demonstrated using a large-area, pulsed electron beam technique. This was used to dramatically improve the surface morphology of Stellite 6 metal powder. Powder surface asperities up to 20 μm size can be eliminated by melting and incorporation into the near-surface of the particle. Surface finish is sig...
Article
Recent innovations in electrochemical jet processing have caused step changes in process flexibility and precision. However, utilisation of these innovations requires the development of new machine tool technology. Presented here is a new methodology enabling the exploitation of highly customisable energy density profiles regardless of toolpath vec...
Article
Electrochemical jet processing (EJP) is an applied electrochemical technique capable of exercising highly localised control of material removal independent of mechanical properties. This makes the process suitable for both micromachining and surface texturing operations in high-value engineering materials, without altering the near-surface in a the...
Conference Paper
Full-text available
Large-area, non-deterministic micro-structuring of biomedical implant surfaces has been shown to elicit favourable cell responses. Chemical etching and laser ablation have both been demonstrated as credible process routes to generate these surfaces. However, both techniques have traits viewed as detrimental in processing and application. Electroche...
Article
Full-text available
Orientation affects application-defining properties of crystalline materials. Hence, information in this regard is highly-prized. We show that electrochemical jet processing (EJP), when coupled with accurate metrological appraisal, can characterise crystallographic texture. Implementation of this technique allows localised dissolution to be anisotr...
Article
Electrochemical jet processing (EJP) is an athermal technique facilitating precision micromachining and surface preparation, without recast layer generation. The role of the microstructure in determining machining characteristics has been largely overlooked. In this study, we show that in order to optimise EJP for a given material, fundamental mate...
Article
Full-text available
Electrochemical jet processing techniques have traditionally been considered to be limited to planar interactions with the electrolyte jet being maintained normal to the workpiece surface. In this study, the viability and resultant effects of articulating the nozzle relative to the work were investigated for the first time. Two machining convention...
Article
Through electro-physical modification of the electrode gap in electrochemical jet techniques, precision has been shown to be greatly increased. Repeatable kerf widths approaching the diameter of the nozzle are demonstrated and the individual contributing effects are quantified across energy density and length scales. This allows the feature resolut...
Article
Full-text available
Electrolyte design for electrochemical jet processing (EJP) techniques can directly affect form and finish of machined structures. A newly developed, industrially focused, EJP machining centre was designed to incorporate complete control of all relevant machining parameters. A computer numerically controlled, electrolyte multiplexing system, was de...
Article
Full-text available
Electrochemical jet processing techniques provide an efficient method for large area surface structuring and micro-milling, where the metallurgy of the near-surface is assured and not adversely affected by thermal loading. Here, doped electrolytes are specifically developed for jet techniques to exploit the Gaussian energy distribution as found in...
Article
Full-text available
Component surface optimisation through the application of surface structuring is understood to be beneficial to performance and longevity of a component in service. However, the multi-functional requirements of a surface defined at the design stage can be difficult to realise. Utilisation of electrochemical jet processing (EJP) methods in surface p...
Article
Full-text available
Electrochemical jet machining (EJM) is a non-conventional machining process whereby material is removed by jet-based anodic dissolution phenomena. As a machining process, EJM is capable of selectively texturing conductive materials, however there are aspects of the technique that have been subject to only limited study. The effect of material preco...
Article
The addition of particles (<1 μm) to electrolyte feedstocks results in marked changes to the morphology of deposits when electrolyte jet processing (EJP) compared to electrolyte only feedstocks. Through the use of a ‘carrier’ electrolyte in additive mode these particulates may become embedded within a deposited matrix. These also serve as nucleatio...
Article
Full-text available
The increasing demand for optimised component surfaces with enhanced chemical and geometric complexity is a key driver in the manufacturing technology required for advanced surface production. Current methodologies cannot create complex surfaces in an efficient and scalable manner in robust engineering materials. Hence, there is a need for advanced...
Article
Full-text available
Electrolyte Jet Machining (EJM) is a non-contact machining process whereby material is removed through highly localised electrochemical dissolution. Throughout the development of this technique, difficulties have been reported in the processing of titanium alloys due to the formation of an electrochemically inert non-conductive passivating layer. I...
Article
Full-text available
Traditional methods for achieving hierarchical surface structures include highly specified, deterministic approaches to create features to meet design intention. In this study microstructural alteration was undertaken using laser apparatus and secondary texturing was achieved via succeeding electrochemical processes. Electrochemical jet machining (...

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Project (1)
Project
Electrochemical Jet Processing (EJP) is a mask-less, tool-less, high precision jetting technology being a variant of Electrochemical Machining (ECM) and Electrochemical Deposition (ECD). The drive within industry is to maximise a components performance at a minimum cost, through the use of advanced materials and highly optimised design. This presents a problem to satisfy the needs of complex component design, at the same time as maintaining a streamlined process. Electrochemical Jet Processing represents a possibility of satisfying this need within a high value precision environment. EJP demonstrates the ability to manipulate metallics at an atomic level. Allowing removal and addition of material within the same framework, in successive operations, without the need for re-fixturing. Therefore, improving process fidelity and streamlining the process chain of high value components. Current research is focussed on exploring and characterising the surface processing of high value alloys through hardware and software design, intrinsic processing parameters, hybrid systems and development of novel processing mediums