There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Additive manufacturing of metallic components – Process, structure and properties

Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...

Laser additive manufacturing of metallic components: materials, processes and mechanisms

The IRC has carried out a major research programme over the last ten or so years aimed at developing the processing and optimisation of TiAl-based alloys. This work has covered melting, the production of shaped castings, powder processing and a range of thermomechanical processing routes in parallel with alloy development. In this paper the work aimed at understanding the factors that influence the properties of thermo-mechanically processed and cast samples of TiAl-based alloys will be reviewed. It is shown that the use of boron to control the grain size of castings leads to limited ductility in the stronger and more highly alloyed TiAl alloys because ribbon-like borides up to 200µm in length can be formed. It is also shown that although a fully lamellar microstructure offers a good balance of properties their plastic anisotropy leads to pre-yield fracture and to reduced fatigue life. It is clear that grain size control is essential if an acceptable balance of properties is to be obtained but that if casting is to be used grain refinement via boron addition is not totally satisfactory. A simple heat treatment can be used to refine the microstructure of cast boron-free alloys, which leads to ductility comparable with that in wrought samples and the associated convoluted microstructure should also eliminate pre-yield cracking.

Processing and Alloy Development to Optimise the Properties and Cost-Effectiveness of Components Manufactured from TiAl-Based Alloys

Cracking of TiAl-based alloys and the effect of cracking on fatigue life

Background Repair of peri-prosthetic proximal tibia fractures is very challenging in patients with a total knee replacement or arthroplasty. The tibial component of the knee implant severely restricts the fixation points of the tibial implant to repair peri-prosthetic fractures. A novel implant has been designed with an extended flange over the anterior of tibial condyle to provide additional points of fixation, overcoming limitations of existing generic locking plates used for proximal tibia fractures. Furthermore, the screws fixed through the extended flange provide additional support to prevent the problem of subsidence of tibial component of knee implant. Methods The design methodology involved extraction of bone data from CT scans into a flexible CAD format, implant design and structural evaluation and optimisation using FEM as well as prototype development and manufacture by selective laser melting 3D printing technology with Ti6Al4 V powder. Results A prototype tibia implant was developed based on a patient-specific bone structure, which was regenerated from the CT images of patient’s tibia. The design is described in detail and being applied to fit up to 80% of patients, for both left and right sides based on the average dimensions and shape of the bone structure from a wide range of CT images. Conclusion A novel tibial implant has been developed to repair peri-prosthetic proximal tibia fractures which overcomes significant constraints from the tibial component of existing knee implant.

Novel implant for peri-prosthetic proximal tibia fractures.

A component can be formed by a hot isostatic pressing (HIP) process but it is necessary to reinforce intricate internal structures against collapse and deformation by the hot isostatic pressing process. The present method utilizes a low melting point salt or alloy reinforcement within the structure which can be released when molten through a drain from the internal structure. The reinforcement may be molten as a result of the hot isostatic process or through achieving a temperature with the component which causes the reinforcement to become molten but without damaging the component itself. The remaining parts of the reinforcement may be removed by use of a solvent or simple washing with a corrosive agent to remove any reinforcement debris.

Component forming method

Samples of Ti–6 wt% Al–4 wt% V and Timet 550 (Ti–4 wt% Al–4 wt% Mo–2 wt% Sn–0.5 wt% Si wt%), which have been deformed at a strain rate of 5 s−1, were annealed after thinning so that the visibility of dislocations in transmission electron microscopy could be compared before and after annealing. It has been found that imaging with g = 0002 produces clear images of dislocations before and after annealing, but that imaging with other diffracting vectors gives reasonable dislocation images only after annealing to at least 700°C. The sharpness of Kikuchi lines in diffraction patterns obtained from fully annealed samples, deformed at 10−1 and 5 s−1, has been examined. The lines are sharp for all planes in the fully annealed samples, but become more diffuse in samples deformed at 10−1 s−1. However, in samples deformed at 5 s−1 the Kikuchi lines from (0002) planes are sharp but the lines from all other planes are diffuse. These observations are interpreted in terms of the presence of a high density of defects, whi...

Xinhua Wu

Papers

Processing and Alloy Development to Optimise the Properties and Cost-Effectiveness of Components Manufactured from TiAl-Based Alloys

Cracking of TiAl-based alloys and the effect of cracking on fatigue life

Novel implant for peri-prosthetic proximal tibia fractures.

Component forming method

The thermal stability of and nature of damage in Ti alloys subject to high-strain-rate deformation