264 research outputs found
Data for the paper "Surface Defects incorporated Diamond Machining of Silicon"
No full textData for the paper titled "Surface Defects incorporated Diamond Machining of Silicon" co-authored by Neha Khatri *1, Borad M Barkachary 2, B Muneeswaran 3, Rajab Al-Sayegh 4, Xichun Luo 5 and Saurav Goel +6,7,8EPSRC Centre for Doctoral Training in Ultra Precisio
Physicochemical and nanomechanical behaviour of 3d printed pegda hydrogel structures for tissue engineering applications
No full textAria, Adrianus Indrat - Associate Supervisor
Goel, Saurav - Associate SupervisorPoly(ethylene glycol) diacrylate (PEGDA) hydrogels are well established in tissue
engineering and organ-on-chip applications as scaffolds for 3D templates in
aqueous environments due to their high water content, biocompatibility and low
toxicity. The versatility of PEGDA hydrogels as a platform for cell encapsulation
and tissue engineering is attributed to their ability to be modified in various ways,
including concentration, molecular weight, and polymerisation technique. Since
properties of the PEGDA host material will affect the functionality of the cells and
tissues, and vice versa, a key missing feature of the currently developed
screening solutions is the lack of proper understanding of the behaviour of the 3D
printed PEGDA soft support structures holding living tissues in a dynamic human like tissue microenvironment. Thus, the aim of this research is to demonstrate
repeatability and reliability in the measurement of physicochemical and
nanomechanical properties of multilayer 3D printed UV crosslinked PEGDA
hydrogels for use in organ-on-chip devices. The research offers insights into long
term stability of hydrogels through studying how changes in both environmental
and printing parameters can be extrapolated to other biomaterials for benefit of
other tissue engineering applications.
Recent advancements in the use of PEGDA hydrogels for tissue engineering are
reviewed, with a focus on bulk cross-linking and 3D printing synthesis methods.
Characterisation methods for 3D printed PEGDA hydrogels are also discussed.
The current state of development of biomedical applications, particularly in organ on-chip devices, is highlighted. The thermal response of multilayer PEGDA
hydrogels made using in-house projection lithography was compared to
monolithic hydrogels created through bulk photo-cross-linking. The results
indicated that the volume of multilayer PEGDA hydrogels changes in response to
the temperature with dimensional change between +10% and -11.5%, and also
displaying an anisotropic characteristic where the axial dimensional change was
higher than the lateral dimension. The results also confirmed the swelling
behaviour to be reversible between 8 and 45 °C. The nanomechanical properties
of monolithic and multilayer PEGDA hydrogels fabricated through bulk cross linking and layer-by-layer projection lithography were studied. The findings
showed that an increase in the number of layers results variation in axial elastic
modulus between 1.69 and 0.67 MPa. Additionally, the research examines the
structural heterogeneity of 3D printed hydrogels which is linked to the degree of
cross-linking of the printed layers and showed variations in lateral elastic modulus
between 2.8 and 11.9 kPa. The results suggest that by controlling the cross linking throughout the 3D printed structure, the surface nanomechanical
properties of the hydrogels can be manipulated to direct cell attachment and
adhesion in specific regions within the structure, offering potential for future
improvement in the reproducibility and reliability of 3D printed hydrogels for tissue
engineering and organ-on-chip applications.Engineering and Physical Sciences Research Council (EPSRC)PhD in Manufacturin
An investigation on the colossal success of Larsen and Toubro Limited: human resource management perspective
No full textDesign of ultra-precision piston/cylinders for directly calibrated hydraulic amplification
No full textForce calibrations in the Mega Newton range are not currently providing the accuracy
required by industry. This work addresses a hydraulic force standards, which perform
such calibrations, which work b amplifying the force produced on a small piston/cylinder
assembly (PCA) by connecting it hydraulically to a larger PCA. The force standards are
currently calibrated using a transducer to the more accurate deadweight machines, but not
without a resulting uncertainty of 0.01 % - 0.02 % imparted by the transducer performing
the calibration. Because of this, the potential for evaluating uncertainties within the
machine from first principles and using it as a primary machine, with traceability
maintained to the weights is evaluated. First of all the potential for the resulting reduction
in uncertainties is evaluated analytically, then FEA/CFD work is carried out to produce
analytical formulae which allow for the design of a directly calibrated system. The
analysis is carried out for both the rotational and non-rotational variants of PCA. Finally,
the design of a primary hydraulic standard is carried out using FEA/CFD.PhD in Manufacturin
Understanding nanoscale material behaviour for improved precision machining of shape memory alloys; testbed study on elliptical vibration assisted cutting of CuZr SMA.
No full textThe field of ultra-precision machining has gained significant importance in the manufacture of components for the electronic, optical and medical industry. Two crucial factors that play a key role in the machinability of materials are the machining parameters and the material’s physical properties. Certain materials such as hardened steel or nickel-based superalloys are difficult-to-machine but innovations in the field of precision machining have developed a technique known as elliptical vibration assisted machining, which enables to improve the machinability of these materials. CuZr high-temperature shape memory alloy is categorized as a difficult-to-cut material and although EVAM has been applied to
a wide range of metals it hasn’t yet been studied in CuZr HTSMA. In this context, the purpose of this thesis is twofold: On the one hand, to characterise the mechanical properties of CuZr SMA using Molecular Dynamics and, on the other hand, to explore the nanoscale mechanism of material removal of CuZr shape memory alloy (SMA) during elliptical vibration assisted machining (EVAM). The conclusions of this thesis can be summarized as follows.
To characterise the mechanical properties of Cu₅₀Zr₅₀, Cu₂Zr and Cu₅Zr, a tensile and shear test were carried out using MD. Tensile test was done with crystal orientation and direction of tensile pulling as . The results showed that Cu₅₀Zr₅₀ and Cu₂Zr exhibited a phase transformation (pseudoelasticity) during loading. However, Cu₅Zr showed dislocation nucleation as the main plastic deformation mechanism followed by fracture.
Shear tests were done in the same phases with crystal orientation and direction of shear pulling as . Interestingly, the shear test results showed no phase transformation for Cu₅₀Zr₅₀ and Cu₂Zr but the Cu₅Zr composition did show phase transformation during loading. It is important to highlight that all three phases of CuZr binary alloy that we have tested showed a different plastic response during the tensile test and the shear test.
As far as machining is concerned, we observed indications that EVAM shows improved machinability compared with conventional machining. Although cutting forces were lower in EVAM, the stresses on the workpiece were slightly higher and both techniques showed the same mechanism of plasticity during machining. Neither dislocation nucleation or martensitic transformation was exhibited in either of the two machining techniques and instead, amorphisation was observed as the main plastic deformation mechanism in both cases. Interestingly, amorphisation has been previously observed by Saitoh and Kubota (2010) during loading NiTi SMA [1]; however, it didn’t show up in every crystal orientation confirming that NiTi shows significant changes in response to loading in different lattice directions.
One of the main outcomes from this thesis is that CuZr SMA exhibits different modes of plastic deformation; namely amorphisation, dislocation nucleation and martensitic transformation during loading. The governing mechanism that arises during loading highly depends in the lattice direction in which the load is being applied. These findings can potentially enable reliable predictions and provide guidelines of the microstructural design of CuZr SMA systemsPhD in Manufacturin
Areal artefact manufacturing using SPDT
No full textWith the increasing importance of the surface engineering, surface topography measuring instrument has been used in wider range of applications, which requires trustworthy calibration process to deliver traceability so that the instrument is able to give comparable and reliable measurement. The calibration standard / artefact is designed to transfer traceability easily and reliably. In current market, the feature of the artefact used for evaluation the surface topography measuring process are not sufficiently accurate. This insufficiency may be solved by using certain types of calibration standard specified in ISO standard however they are not commercially produced. In this project, one of the desired types called ‘radial sinusoidal shape’ was produce by SPDT (single point diamond turning) manufacturing method. The feature parameters of the artefact are designed to meet the instrument measurement requirement and the machining path is generated with consideration of the tooling geometry. To assess the repeatability in z direction of the turning machine, a step height experiment was designed and conducted. The measurement result indicates that the repeatability of the machine is unsatisfactory when the feed distance smaller than 100 nm. The wavelength and the amplitude of machined radial sinusoidal shape was measured by stylus profiler, followed by the measurement uncertainty analysis. The measurement result was compared with the design to evaluate quality of the manufacturing process. To estimate the systematic error of the profiler, CCI was used to measure the machined radial sinusoidal shape. The measurement result was also compared with the design.PhD in Manufacturin
Ultra precision air bearing development for low cost manufacturing.
No full textAir bearings today are extensively used in the industry, the manufacturing processes involved in fabricating these bearings are complicated and have major drawbacks. The current research investigates the failure of aerostatic bearings based upon which a manufacturing process is developed which removes the correlation between the bearing surface and the effective gap between these surfaces. This results in low manufacturing errors due to the omission of repeated machining of the bearing surface.
The second factor that is novelty towards this research is the application of aluminium coated with hard nickel as suitable alternative to bearing base material instead to the current material for aerostatic bearings. This proposed material solution has low density, good wear resistance and good corrosion resistance. This allows the application of diamond turning instead of precision grinding as the bearing machining process. Reducing on majority of the manufacturing while achieving the form accuracy of the bearing surface.
The third novelty factor is the application of bi-conic configuration which would allow self-aligning capability and has a smaller packaging size as compared to any other fluid film mechanical configuration.MSc by Research in Manufacturin
Fabrication of micro-scale features on titanium alloys through micromilling.
No full textStructured surfaces are of high interest in the manufacturing world, allowing for functionality to be applied to materials through nothing more than a change in the surface topography or an application of a surface coating. Applications for these surfaces range greatly, including, optical surfaces for antireflective surfaces, thermal structures to assist in heat dispersion and anti-fouling surfaces to reduce organisms from adhering to components. Hydrophobic structures, such as the one that have been examined on the lotus leaf under SEM, generate high droplet contact angles and roll off. The manipulation of surface wettability is of particular interest in areas such as the medical sector for self-cleaning applications or controlling cell adhesion on the surface of an implant.
This work investigates the generation of micron level hydrophobic features on two
Titanium alloys, Ti-6Al-4V alpha-beta alloy and Ti-30Nb beta alloy, with the aim of identifying how accurately surface structures can be produced through micromilling as well as experimentally testing how successfully these surfaces function after being fabricated. On each alloy, nine different 5mm x 5mm test pillars are machined using micromilling, half of each pillar is machined with 200μm wide and 30μm deep channels, generating a hydrophobic groove structure, and the other half being flat machined. Across these nine pillars the feedrate, spindle speed, axial depth of cut and tool step over were varied to optimise these parameters in terms of structure generation, channel bottom surface roughness and tool to workpiece interaction in an attempt to determine how effective micromilling is as at structuring the surface of beta Titanium alloys. Tool condition was assessed qualitatively using SEM imaging and an independent assessment was carried out to determine the mechanical properties of the beta Titanium alloy being machined.MSc by Research in Manufacturin
Selected area hot machining with a multi-tipped diamond tooling system.
No full textAn investigation of a novel ultra-precision tool is presented, the hot-milling multi-turret diamond tool. The tool implements micro-Laser Assisted Machining (μ-LAM) upon a multiple diamond fly cutter. Details of its design, both mechanical and optical, are presented- along with proposed modifications to Cranfield University’s Tetraform C machine to allow for its implementation. Relevant experimentation is presented- the modal analysis of the Tetraform C machine and the testing of laser heating on a silicon substrate. FE analyses are carried out and calculations presented to justify design choices. Analytical investigations predicted increased depths of cut by using laser, and indicated that at lower wavelengths of laser light and with lower feed rates that the depth of cut may be significantly increased. A novel method of selecting laser
wavelength based upon change in material absorptivity with temperature is investigated which may offer substantial increases in μ-LAM performanceMSc in Manufacturin
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