糖心原创

Being composed of a soft/ductile phase (i.e. the matrix) and a hard/brittle phase (i.e. the reinforcement), machining of metal matrix composites MMCs can be quite difficult to machine. Thus, THERMACH aims to tackle this by exploring and understanding how thermally assisted machining can improve the cutting performance of this type of materials.

This involves Laser Assisted Machining (LAM), i.e. laser-heating the workpiece prior to machining, with a specific scanning speed and path to optimise the mechanical properties at a given depth of cut and with a specific set of machining parameters.

Employing materials characterisation, surface integrity analysis, tool wear and production capability analysis, this project aims to be a step forward on the machinability of the MMCs that are used in aeronautic, biomedical and capital goods industries.

Machining remains one of the most widely used processes for producing precision parts in the aerospace and automotive industries. The demand for high-performance, quality-assured components requires high accuracy, often at large scales, which increases manufacturing costs. It is generally accepted that precision machining requires stiff, highly accurate machines with large footprints, causing costs to rise as tolerances become tighter. As a result, manufacturers rely on expensive off-line verification and error compensation methods that often overlook the effects of tool and workpiece geometry, cutting forces, and time-varying errors.

The growth of additive manufacturing produces complex parts with thin walls and intricate geometries that require finish machining using long, slender tools. Cutting forces can deflect both the tool and workpiece, reducing accuracy and causing chatter, poor surface quality, and shortened tool life.

This project develops low-cost, nanoscale-resolution sensors, advanced signal processing, and intelligent control methods to detect and prevent machining anomalies in real time, ensuring precision, improving quality, and reducing scrap.

ProDesk-3D develops and demonstrates a novel multi-process, multi-axis, self-sufficient desktop machine (DeskMach) for the high-precision manufacture of 3D micro-components with integrated surface micro-features and minimal human intervention. The system incorporates several innovative approaches.

First, a reconfigurable “slot-in” facility transfers parts in situ between operations through an intelligent control system, reducing processing errors and unnecessary handling. Second, a hybrid parallel kinematic multi-axis (6+2) positioner serves as the central platform for the slot-in stations, providing a compact design with low positioning errors. Third, a built-in part and end-effector handling system, combining a smart robotic arm with an optimised station layout, reduces ancillary equipment and improves compactness. Finally, in-situ metrology, machine vision, and referencing systems monitor printed parts and end-effectors in real time, ensuring process compliance, improving accuracy, and reducing downtime.

The resulting multifunctional components support applications in the medical, aerospace, electronics, instrumentation, and automotive sectors.

STIMULANT develops and demonstrates surface integrity-conscious hybrid machining processes for safety-critical aeroengine components, delivering step changes in material removal rates (MRR) while reducing production costs. The project builds on knowledge and technologies at different maturity levels across the consortium and advances them through a Standard Features (StdFs) methodology towards demonstration on engine-like safety-critical parts.

The approach identifies and classifies common aeroengine features according to their technical, functional, and economic characteristics, enabling the selection of the most cost-effective hybrid machining solutions. STIMULANT develops and validates heat-controlled hybrid high-speed machining, erosion-controlled hybrid waterjet machining, and hybrid laser waterjet-guided machining to improve productivity, geometrical accuracy, and manufacturing efficiency while maintaining surface integrity and fatigue performance. The validated processes are then integrated into hybrid manufacturing routes and demonstrated on representative aeroengine components, providing a more reliable, productive, and cost-effective approach to machining complex safety-critical aerospace parts.

Aeroengine blades are critical safety components whose reliability and performance directly affect aircraft operation. During service, these components experience material degradation and damage that can compromise their integrity and reduce service life. Effective repair and restoration are therefore essential to maintain performance and prevent premature failure.

This research investigates the application of energy beam technologies, particularly waterjet-based processes, for the repair and enhancement of degraded aeroengine components. The study examines both material removal and surface modification processes, combining experimental investigations with process modelling to improve understanding of fundamental material removal mechanisms and minimise surface damage. In addition, post-repair surface enhancement techniques, including waterjet peening, are evaluated to improve surface integrity, fatigue resistance, and component reliability following laser-directed energy deposition repairs.

The work aims to restore damaged regions to their original functional condition and facilitate the transfer of advanced repair technologies from laboratory research to practical aerospace maintenance and repair applications.

This research investigates how laser scanning rotation and vector length influence microstructure evolution in LPBF-fabricated Alloy 718 and how these microstructural features affect post-machining deformation and chip formation.

Multi-vector-length scanning strategies ranging from 80 to 4000 µm are examined, revealing that short vectors generate deeper melt pools, finer grains, and higher hardness, whereas longer vectors produce coarser grains and reduced hardness. Machining studies combined with quasi-in-situ deformation tracking evaluate the response of textured LPBF microstructures during cutting, showing non-homogeneous slip behaviour and grain-scale anisotropy. Quick-stop tests further demonstrate that elongated LPBF grains influence shear-band development, increasing shear angle and reducing chip ratio compared with wrought equiaxed microstructures.

The work provides insight into the relationship between LPBF processing parameters, microstructure development, and machining behaviour in Alloy 718.

Thermal barrier coatings (TBCs) are widely used to protect high-temperature components from harsh operating environments and thermal degradation. However, conventional top-coat systems often lack sufficient thermal compliance and environmental resistance, which can lead to premature failure.

This work develops and evaluates novel shielded-compliant TBC architectures using laser-based surface modification techniques. Laser grooving is employed to reduce thermal mismatch stresses and impede crack propagation, while laser glazing enhances mechanical strength and corrosion resistance. Microstructural analysis of the glazed layer reveals large columnar grains and a relatively stress-free structure compared with the as-sprayed coating. In-situ digital image correlation heating tests demonstrate that vertical cracks formed during glazing act as effective stress-relief features, while controlled groove patterns provide the greatest thermal compliance. Finite element analysis supports these observations and explains the resulting strain distributions.

The study advances understanding of laser-engineered coatings and establishes a versatile approach for improving the durability, compliance, and environmental resistance of protective coating systems.

This work investigates Deep‑Eutectic Fluids (DEFs) as sustainable alternatives to conventional cutting fluids in grinding. A dual‑phase DEF, SolBar, is developed to melt in the grinding zone, enabling precise lubrication, cooling, and formation of tribo‑active layers.

When applied to nickel‑based superalloys, DEFs reduce severely deformed layers by up to 47%, achieving surface integrity comparable to water‑based fluids. The work also demonstrates electro‑actuation, where electric fields modulate DEF‑induced surface stress on metals, amplifying effects by up to 51%.

These findings show DEFs can enhance grinding performance, reduce environmental impact, and enable adaptive, responsive machining systems.

Fibre-reinforced metal matrix composites (MMCs) offer attractive combinations of low weight and high mechanical performance, but their heterogeneous structure makes them difficult to machine.

This work investigates the material removal mechanisms and surface integrity generated during machining of SiCf/Ti-6Al-4V and SiCf/Al6061 composites. Face-milling and orthogonal-cutting experiments are used to evaluate the influence of SiC fibres on chip formation, cutting forces, subsurface damage, and cutting-depth effects. Additional machining trials under cryogenic and elevated-temperature conditions assess the role of temperature on machining performance. The results show that cryogenic machining increases cutting forces and fibre-related damage, whereas elevated temperatures promote matrix softening and may benefit rough machining operations.

The findings provide guidance for improving machining efficiency and surface quality in high-performance MMC components.

The growing demand for high-power-density electrical machines drives the development of advanced manufacturing approaches that maximise performance while minimising material use. Significant improvements in machine efficiency are achieved through precise shaping and cutting of soft magnetic materials, yet the underlying micromagnetic mechanisms affected by manufacturing processes remain poorly understood.

This work investigates how sub-micron deformations applied at strain rates ranging from 10⁻² to 10¹ s⁻¹ influence the micromagnetic behaviour of non-oriented electrical steel. Diamond probe nano-indentation within individual grains introduces both quasi-static and dynamic mechanical loading conditions. Advanced characterisation techniques, including magnetic force microscopy, transmission Kikuchi diffraction, and scanning transmission electron microscopy, reveal that magnetic texture disturbances are strongly linked to time-dependent dislocation dynamics within the body-centred cubic iron microstructure. Complementary micro-pillar compression experiments further isolate bulk deformation effects.

The study provides fundamental insights into magneto-mechanical interactions, improving understanding of how manufacturing-induced deformation affects magnetic texture and supporting the development of next-generation electric machines with enhanced performance and reliability.

Improved grinding performance can be achieved through precise control of abrasive architecture.

This work investigates engineered abrasive pads for controlled planar grinding, addressing the limitations of conventional diamond grinding tools, where random grit size, shape, spacing, and protrusion can reduce control over surface texture generation, chip flow, grinding temperature, and force. Ordered CVD diamond abrasive pads are produced using laser processing to create controlled grit geometries and contact areas. Inverted grinding experiments compare conventional abrasive pads with engineered saw-tooth and square-frustum grit designs, while a geometrical model is developed to predict surface roughness.

The results show that laser-generated abrasive pads improve surface finish, reduce grinding-induced damage and tool wear, and can increase material removal rates through optimisation of planar contact area. The work demonstrates the potential of engineered abrasive architectures for enhancing the efficiency and predictability of grinding processes.

Improved drilling performance in SiC-based ceramic matrix composites requires a detailed understanding of the mechanisms governing material removal and damage formation.

This work investigates the machining-induced surface effects associated with drilling small holes in SiC-CMCs for aero-engine applications. The influence of the material's orthotropic, brittle, hard, and heterogeneous nature on chip formation, defect generation, and tool performance is examined. Commercial drills are assessed to determine their suitability for machining SiC-CMCs, and appropriate characterisation methods are established to quantify machining-induced damage.

The findings identify key material-related challenges, provide guidance for drilling strategy optimisation, and outline design requirements for next-generation drill bits capable of improving machining quality and productivity in ceramic matrix composites.

This work investigates the kinematic behaviour of polishing systems and identifies a previously unreported parasitic motion arising from the pseudo-constrained interaction between the workpiece and planetary carrier. A motion-capture system is used to track both the primary and parasitic motions between the sample and polishing pad, enabling the development and validation of a new kinematic model. The study quantifies the influence of parasitic motion on surface roughness and demonstrates that incorporating these effects significantly improves the prediction of workpiece surface morphology compared with conventional planetary models.

The findings highlight the importance of considering tool-workpiece compliance in polishing and provide a framework for improving process modelling and prediction in other manufacturing operations.

Laser cladding is widely used for component repair and surface enhancement, but accurate prediction of deposited geometry remains essential for process control and automation.

This work develops an analytical model of laser-clad track formation that predicts both the deposited material above the surface and the underlying melt pool. Based on capillary theory and interfacial tension calculations, the model evaluates the influence of process parameters, including laser power, scanning speed, and wire feed rate, on the final deposit geometry. Experimental validation is performed using dimensional measurements of deposited tracks and metallographic assessment of melt-pool cross-sections. The model demonstrates good agreement with experimental results and provides a time-dependent framework that can be readily implemented on machine tools and robotic systems.

The findings support improved control of clad geometry through process parameter optimisation, particularly laser scanning speed.

Aerospace coatings, including thermal barrier and abradable coatings, play a critical role in protecting engine components from harsh operating environments and elevated temperatures. However, coating degradation and spallation caused by thermal mismatch often require component refurbishment long before the end of the engine service life.

This work investigates plain waterjet (PWJ) milling as a controlled and damage-free coating removal process. Mathematical models are developed to predict jet footprints and material removal during milling of multi-layer coating systems using rotational multi-nozzle waterjet configurations. The models account for the mechanical properties of individual coating layers, jet energy distribution, nozzle trajectories, and process time, and are validated experimentally before being integrated into a user-friendly industrial software platform.

The work also examines the response of yttria-stabilised zirconia (YSZ) coatings to high strain-rate loading, revealing strain-rate-dependent failure mechanisms and phase transformations relevant to waterjet-induced erosion.

Laser processing offers a flexible, non-contact approach for the repair and modification of aero-engine components, particularly in areas that are difficult to access using conventional manufacturing methods.

This work investigates laser-based technologies for on-wing maintenance of thermal barrier coatings (TBCs). Laser surface modification is used to engineer coating microstructures by introducing columnar architectures and dense surface layers to enhance thermal cycling, erosion, and environmental resistance. The research also examines solidification phenomena in laser-melted TBCs, identifying mechanisms responsible for grain bending and grain surface sealing through coupled thermal and grain-growth modelling.

Finally, the feasibility of laser-based coating deposition in atmospheric conditions is explored as an alternative to conventional vapour deposition processes. The work advances understanding of laser-material interactions, coating microstructure development, and in-situ repair technologies for aerospace applications.

Understanding the thermal conditions generated during machining is essential for predicting surface integrity in advanced engineering materials.

This work investigates the relationship between subsurface thermal history and machining-induced metallurgical changes during cutting. By analysing thermal field evolution under varying thermo-mechanical conditions, two distinct thermal cycles are identified: Heating-Peaking-Cooling (H–P–C) and Heating-Quasi-isothermal Deformation-Cooling (HQC). Thermal balance analysis is used to quantify heat generation associated with plastic deformation during tool-workpiece interaction and to examine its influence on surface damage formation.

The results link intense near-surface heat generation to the formation of white layers, while less severe deformation at greater depths is associated with material drag layer development. By relating thermal history to resulting metallurgical integrity, the work provides new insight into the mechanisms governing machining-induced surface modification and damage formation.

Repairing thermal barrier coatings (TBCs) within gas-turbine combustors presents significant challenges due to restricted access and the need for controlled coating deposition in confined environments.

This work investigates in-situ TBC repair using Combustion Flame Spray (CFS). Coating formation is first examined at the single-splat scale, linking particle flattening and solidification behaviour to coating properties such as adhesion and residual stress. The influence of powder morphology, equivalence ratio, feed rate, carrier-gas flow rate, and standoff distance on coating quality is systematically evaluated to establish an optimal deposition window. A three-dimensional finite-difference deposit-growth model is then developed to predict coating geometry and temperature evolution with high spatial accuracy.

The findings improve understanding of thermal-spray deposition processes and support the development of controlled and automated TBC repair technologies for aerospace applications.

This work develops and validates pulsed‑laser machining for in‑situ repair of aero‑engine components where rigid grinding tools cannot access modern architectures such as the Trent XWB.

Using a nanosecond Yb:YAG laser, optimal parameters were identified to balance machining time and metallurgical quality, achieving full‑edge ablation. A predictive topography model showed high accuracy across materials and high‑cycle fatigue tests on real HPC blades confirmed that laser repairs meet Rolls‑Royce lifing requirements, with microstructural changes limited to acceptable recast.

The work further validates prototype tooling across representative repair geometries, supporting the implementation of laser-based repair technologies for next-generation aero-engines.

Precise depth control in abrasive micro-waterjet machining remains challenging because erosion behaviour depends strongly on process parameters and inherent random variation within the jet.

This work investigates the stochastic nature of abrasive micro-waterjet controlled-depth machining through the development of predictive modelling tools. A finite element framework is used to simulate multiple high-speed particle impacts, while a geometrical energy-beam model provides a computationally efficient alternative for surface prediction. To capture process variability, a stochastic partial differential equation is developed to predict trench-profile distributions under different feed conditions. Experiments on model materials are used to examine the role of microstructure in governing erosion mechanisms.

The work provides a foundation for improved process understanding, prediction, and control in abrasive waterjet machining.

Evaluating the surface integrity of nickel-based superalloys is critical for aerospace, nuclear, and marine applications, where machining-induced damage can significantly affect component performance and service life. Conventional machinability assessment methods are often time-consuming, material-intensive, and require extensive machining trials across multiple cutting conditions.

This work develops a novel Pendulum-Based Cutting Test (PBCT) methodology that enables rapid evaluation of surface integrity-related machinability using only a limited volume of material. The approach links machining-induced surface damage to cutting energy through a unified energy-partition model, allowing energy thresholds associated with acceptable surface integrity to be established independently of specific cutting parameters. The methodology also enables continuous assessment of cutting behaviour across a wide range of cutting speeds within a single test.

Combined with microstructural characterisation techniques, including EBSD, the work provides an efficient framework for studying machining mechanisms, surface damage evolution, and process optimisation in nickel-based superalloys such as Inconel 718.