PhD, EngD, MPhil and MSc by research theses (CDS)

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Open Access
The Stability of NiTi shape memory alloys and actuator applications
(Cranfield University; College of Defence Technology; Department of Materials and Medical Sciences, 1999-10) Morgan, Neil; Friend, Clifford M.
Recent research and development in the area of shape memory alloys (SMA) continues to yield novel and unique results. Of the alloys that display the effect NiTi alloys have found the most commercial interest resulting in a number of niche applications, particularly in the medical device industry. An analysis of the market and strategic issues associated with diffusing NiTi SMA's into mainstream design use and commercial application is presented. It is concluded that for SMA's to become commercially viable, R&D must be carried out on design relevant properties and particular the cyclic stability. To address this need a systematic investigation into the durability and stability of martensitic transformations in commercial NiTi actuator alloys has been completed. A factorial design on experiments approach is employed to study: alloy type, thermal processing, heating/cooling rates, applied loads and prior cold work level. In addition, the structural integrity and internal stress effects of repeated actuation against applied external stress are considered and compared with previously published data. For the first time, this work analyses the main interactive effects and individual significance of processing and operating variables on transformation stability and actuator output. The results can therefore be used as a guide to optimizing the processing and operating conditions for long term actuator stability.
Open Access
Gun barrel design optimisation using finite element analysis
(2000) Hameed, Amer; Brown, R. D.; Hetherington, John G.
The strength of a gun barrel is a function of the residual circumferential stress at the bore. This stress is known to be affected by the properties of the gun barrel material, especially the Bauschinger effect. This thesis examines the influence of the constitutive relationship for various materials on the resultant stresses in the barrel. The work reported here consists of two major parts: experimental, and numerical analysis using the finite element method. The experimental work concerns the autofrettaging of selected test specimens and the gathering of data. Test specimens were heat-treated to give a range of strain hardening and initial yield stress characteristics. This was done in order to examine the influence of the Bauschinger effect on the resultant stress field for materials with various constitutive relationships. The numerical part of the work consists of the simulation of the tests using finite element methods. The results of the numerical simulation are compared with the experimental data. There is good agreement between the results, and they suggest that a. there is no significant effect on the reyield pressure of the test cylinders which have strain hardening; b. machining of the bore diameter increases the residual stress at the new bore diameter; c. machining of the outside diameter reduces the residual stress at the bore; d. most of the samples showed elastic relaxation due to the machining. However some localised plastic deformation was observed at the new surface in the case of machining at the inside diameter; e. machining does not cause the elastic-plastic interface to move; f. the influence of the Bauschinger effect increases with increase in tangent modulus (strain hardening); Further simulations were carried out to investigate the effect of boring gas evacuator holes or cross bores and results suggest that there is a severe localised loss of residual stress at the bore and the affected zone spreads to approximately 5 times the cross-bore diameter. The reyield pressure at the bore reduces by approximately 70%, suggesting that the benefit of autofrettaging is lost.
Open Access
Stab resistant body armour
(Cranfield University, 2000-03) Horsfall, Ian; Edwards, M. R.
There is now a widely accepted need for stab resistant body armour for the police in the UK. However, very little research has been done on knife resistant systems and the penetration mechanics of sharp projectiles are poorly understood. This thesis explores the general background to knife attack and defence with a particular emphasis on the penetration mechanics of edged weapons. The energy and velocity that can be achieved in stabbing actions has been determined for a number of sample populations. The energy dissipated against the target was shown to be primarily the combined kinetic energy of the knife and the arm of the attacker. The compliance between the hand and the knife was shown to significantly affect the pattern of energy delivery. Flexibility and the resulting compliance of the armour was shown to have a significant effect upon the absorption of this kinetic energy. The ability of a knife to penetrate a variety of targets was studied using an instrumented drop tower. It was found that the penetration process consisted of three stages, indentation, perforation and further penetration as the knife slides through the target. Analysis of the indentation process shows that for slimmer indenters, as represented by knives, frictional forces dominate, and indentation depth becomes dependent upon the coefficient of friction between indenter and sample. Analytical models are demonstrated to provide a reasonable estimate of energy absorption during and after penetration for a wide variety of knives and armour materials. The key armour parameters are shown to be the frictional interaction with the blade and the strength of the target material. The performance of knife blades is shown to increase with increasing sharpness, slimness, and surface finish. No single knife design performs best against all types of armour, and no single armour is best against all knife blades.
Open Access
Sensors, measurement fusion and missile trajectory optimisation
(Cranfield University; College of Defence Technology; Department of Aerospace, Power and Sensors, 2003-07) Moody, Leigh; White, Prof B A
When considering advances in “smart” weapons it is clear that air-launched systems have adopted an integrated approach to meet rigorous requirements, whereas air-defence systems have not. The demands on sensors, state observation, missile guidance, and simulation for air-defence is the subject of this research. Historical reviews for each topic, justification of favoured techniques and algorithms are provided, using a nomenclature developed to unify these disciplines. Sensors selected for their enduring impact on future systems are described and simulation models provided. Complex internal systems are reduced to simpler models capable of replicating dominant features, particularly those that adversely effect state observers. Of the state observer architectures considered, a distributed system comprising ground based target and own-missile tracking, data up-link, and on-board missile measurement and track fusion is the natural choice for air-defence. An IMM is used to process radar measurements, combining the estimates from filters with different target dynamics. The remote missile state observer combines up-linked target tracks and missile plots with IMU and seeker data to provide optimal guidance information. The performance of traditional PN and CLOS missile guidance is the basis against which on-line trajectory optimisation is judged. Enhanced guidance laws are presented that demand more from the state observers, stressing the importance of time-to-go and transport delays in strap-down systems employing staring array technology. Algorithms for solving the guidance twopoint boundary value problems created from the missile state observer output using gradient projection in function space are presented. A simulation integrating these aspects was developed whose infrastructure, capable of supporting any dynamical model, is described in the air-defence context. MBDA have extended this work creating the Aircraft and Missile Integration Simulation (AMIS) for integrating different launchers and missiles. The maturity of the AMIS makes it a tool for developing pre-launch algorithms for modern air-launched missiles from modern military aircraft.
Open Access
Interfacial and durability aspects of extrinsic Fabry-Perot interferometric sensors in carbon fibre composites
(Cranfield University, 2003-09) Etches, J A; Fernando, G F
This thesis is concerned with the interfacial and durability aspects of Extrinsic Fabry- Perot Interferometric (EFPI) sensors embedded in carbon fibre reinforced composites. Fibre optic sensors are being used in many long term applications and, as is the case for all sensor types, the ability of the EFPI sensors to monitor accurately the measurands of interest over the lifetime of the structure must be proved. Therefore, the aim of this work was to examine the interface between the EFPI sensors and the structures, and then to evaluate the durability of that interface and the sensors. The first stage was an examination of the EFPI sensors including the method of manufacture, interrogation option and inherent strength of the sensors. It was found that the sensors have a very low tensile load to failure (~0.5 N). This was improved by using a resin reinforcement, which was applied to the capillary ends. However, this had implications for the overall sensor size and that influenced their embedment suitability. The second stage was interfacial characterisation; this was achieved through the examination of the surface energy of the sensors, carried out by contact angle measurements; and the interfacial shear strength of the sensors to matrix, using a new variation on the single fibre pull-out technique that involved the use of optical fibres and composite prepreg. Overall, it was found that the silane treatment of the fibres increased the surface energy but for the interfacial shear results the data was less conclusive due to the scatter present within the results. The durability of the sensors was examined through their embedment into carbon fibre composite samples and exposure to tension/compression fatigue loading. From initial quasi-static work it was found that the embedment of the sensors had no significant effect on the composite samples. However, the sensors failed at a strain levels of 0.4% in tension and at 1.1% in compression; the compression strain level was at the point of composite failure. Under fatigue loading the sensors could survive a million cycles at R=-1 at a max stress level of 156 MPa and maintain their reliability. If the tensile loading was increased then the sensors would fail within a few thousand cycles. However, if the compressive stress was increased the sensors survived but the reliability was affected. Overall, it was felt that with some improvements to the sensor design they should be able to survive and provided useful data when exposed to axial tension/compression fatigue regimes.
Open Access
A Nonlinear, Unsteady, Aerodynamic Model for Insect-like Flapping Wings in the Hover with Micro Air Vehicle Applications
(Cranfield University, 2004) Ansari, Salman Ahmad; Knowles, Kevin
The essence of this PhD thesis is the analytical, aerodynamic modelling, as opposed to using grid-based methods such as CFD, of insect-like flapping wings in the hover for micro air vehicle applications. A key feature of such flapping-wing flows is their unsteadiness and the formation of a leading-edge vortex in addition to the conventional wake shed from the trailing edge. What ensues is a complex interaction between the shed wakes which, in part, determines the forces and moments on the wing. In an attempt to describe such a flow, two coupled, nonlinear, wake integral equations are derived and these form the foundation upon which the rest of the work stands. The model so developed is unsteady and inviscid in nature and essentially two-dimensional. It is converted to a 'quasi-three-dimensional' model using a blade-element-type analogy but with radial chords. The governing equations developed in the study are exact but do not have a closed form. Solutions are, therefore, found by numerical methods and implemented in FORTRAN. The model is validated against existing experimental data and remarkable agreement is found both in terms of flow field representation and force prediction. The importance of including the effect of the leading-edge vortex for such problems is also established. The model is then used for a parametric study to analyse the effects of various wing geometry and wing kinematics parameters. From these results, a preferred wing design for a flapping-wing MAV is proposed which is the ultimate aim of this work. The results from the unsteady, aerodynamic model are also compared with earlier work in the PhD using a simple quasi-steady model and good agreement is found in terms of the relative merits of the various wing parameters, thereby establishing the usefulness of using such simple models for initial design studies.
Open Access
The Armed Forces of Australia, Britain and Canada and the impact of culture on joint, combined and multi-national operations : a methodology for profiling national and organisational cultural values and assessing their influence in the international workplace
(Cranfield University, 2004-01) Stocker, Ashley; Taylor, Prof T.
This study identifies the influence of national and military organisational values on the cultures of the armed forces of Australia, Britain and Canada, in order to assess the impact of culture on Joint, Combined and Multinational operations. This is achieved by: · Defining culture, values and related concepts. · Outlining a viable methodology to examine and profile cultural values. · Demonstrating why values form the basis of this study. · Reviewing the body of cross-cultural academic literature on cultural values and the military. · Executing a measurement of values in a consistent and academically sound manner. · Examining national influences on the culture of the armed forces of Australia, Britain and Canada. · Examining intra- national organisational influences on the culture of the services of the armed forces of Australia, Britain and Canada. · Examining international organisational influences on the culture of the services of the armed forces of Australia, Britain and Canada. · Focusing on the values of the armed forces examined in this study in order to compare the findings with the results obtained from the Values Survey Module. · Discussing the implications of the findings of this study and demonstrate how the values of the nations and organisations that have been examined can be expected to affect future operations.
Open Access
The Microwave properties of tissue and other lossy dielectrics
(Cranfield University, 2004-03) Alabaster, Clive M.; Dahele, J S
This thesis describes work on the theoretical modelling and experimental measurement of the complex permittivity of dielectrics. The main focus of research has been into the characterisation of permittivity of planar and layered samples within the millimetre wave band. The measurement method is based on the free-space measurement of the transmission and reflection coefficients of samples. A novel analytical method of determining the transmission and reflection coefficients as functions of frequency arising from a generalised structure of planar dielectric layers is also described and validated. The analytical method is based on signal flow techniques. The measurement and analytical techniques have been applied in two main areas: firstly, the acquisition of new data on human skin in the band 57 to 100GHz and secondly, the detection and location of defects in composite materials for which a band of 90 to 100GHz was used. Measurements have been made on the complex permittivity of a single sample of excised human skin fixed in formaldehyde. The experimental results have been corrected to account for the fixing process in formaldehyde and are projected to body temperature. This data is, to the best of the author’s knowledge, the first of its kind to be published. Predicted skin permittivity based on various relaxation models varies widely and only partially fits the measured data. The experimental results have been used to determine the parameters of a Cole-Cole function which gives the best fit to the measured data. The measured skin data has also been used to calculate power deposition in skin exposed to millimetre wave radiation. This work concludes that a skin surface temperature rise of only 0.20C results from a thirty second exposure to signals of 100W/m2. Experimental work with fibreglass composite samples has shown that defects such as delaminations, voids, matrix cracks and improper cure result in resolvable differences in the dielectric properties of the samples at 90 – 100GHz. The measurement technique is particularly sensitive to the detection of cracks and its spatial resolution is 20mm or better. Whilst confirming the general conclusions of previously published work, the specific findings of this study are novel.
Open Access
A systems approach to the design of personal armour for explosive ordnance disposal
(Cranfield University, 2004-11) Couldrick, C A; Iremonger, M J; Gotts, P L; John, Philip
A qualitative description of the personal armour design system is elicited by comparing armour throughout the ages. Inputs that 'shape' designs are the materials technology, threat, wearer, task and environment. The emergent properties of protection, ergonomic effectiveness and financial cost form the basis of trade-offs to select final solutions. Work on the protection subsystem refines the key positive emergent property of personal armour. Existing quantifications of protection effectiveness are rejected in favour of a novel measure named the Usefulness Factor, UF. This is the first measure that accounts for the real benefit of armour. A five-stage model is proposed for the assessment of protection. Two feedback loops - due to making tasks as safe as possible and the ergonomic penalty of armour are evident. These must be considered in order to assess protection correctly. Casualty reduction analysis software (CASPER) is used to produce 'approach plots' and 'zones of usefulness' in order to make tasks safer and map the benefit of armour. This approach is demonstrated with the UK's Lightweight Combat EOD Suit against L2A2 and No. 36 Mills grenades, an HB876 area denial mine, a BL 755 sub-munition and a 105mm artillery shell. Assessment of secondary fragmentation from antipersonnel (AP) blast mines defines a threat input that is specific to Explosive Ordnance Disposal (EOD). Trials are carried out with explosive charges of 50g to 500g, buried under 5 or 10cm of stones and sand at a range of 1m. The threat is defined in terms of the probabilities of (a) being hit, (b) a hit perforating armour and (c) a hit incapacitating an unarmoured person. The chances of being hit close to the ground decrease to approximately 15% of the value when directly above the mine. Secondary fragmentation is not likely to perforate armour that protects against primary fragments. However, it is likely to incapacitate an unarmoured person. Protection is traded-off against proxies for ergonomic and financial cost effectiveness by using quantitative optimisation of personal armour. This introduces the concept of a 'protection optimisation envelope', which defines the bounds of possibility rather than a single solution. CASPER is adapted to produce weight and cost as well as incapacitation parameters. This provides a model that generates both benefits and constraints of armour. Hence, the foundations are laid for the world's first fully integrated personal armour design tools. The ergonomic effectiveness subsystem is the primary constraint of personal armour. Visor demisting for the UK's Mk 5 EOD Suit provides a simple example. Existing methods of assessment of the ergonomic penalty of armour are considered. A novel development of biomechanics computational models is proposed to predict both the mechanical and thermal burdens of armour.
Open Access
Non-invasively assessed skeletal bone status and its relationship to the biomechanical properties and condition of cancellous bone
(Cranfield University, 2005-12) Cook, R. B.; Zioupos, Peter
Cancellous bone constitutes much of the volume of bone which makes up axial skeletal sites such as the vertebrae of the spine and the femoral neck. However the increased vascularity of cancellous bone compared with cortical bone means that it is more prone to drug, endocrine and metabolic related effects and therefore these skeletal sites are more prone to the bone condition osteoporosis. With the bone condition osteoporosis increasing in prevalence it is becoming far more important not only for those at risk of having the condition to be diagnosed earlier, but also for the effects of the condition to be better understood. There is a need for the better clinical management of fractures and for therapies and medical practices that will best avoid the low trauma fractures that are seen as a consequence of the condition. This study is in two separate sections, the first constitutes an investigation into the diagnostic abilities of the CUBA Clinical and Sunlight Omnisense quantitative ultrasound systems; and on the other hand an examination of the osteoporotic risk factor questionnaires, Osteoporosis Risk Assessment Instrument (ORAI), Osteoporosis Index of Risk (OSIRIS), Osteoporosis Self-assessment Tool (OST), Patient Body Weight (pBW), Simple Calculated Osteoporosis Risk Estimation (SCORE) and the Study of Osteoporotic Fractures (SOFSURF). The skeletal status was assessed by DXA at the axial skeleton. The aim was to differentiate between the systems that could rationally be used to screen populations to identify those who needed DXA densitometry investigations, on the basis of ability. The second section of the study focused on the biomechanics of cancellous bone, with the initial studies examining the compressive properties of both osteoporotic and osteoarthritic cancellous bone and the effects that the conditions have on the compressive mechanics of the bone. The later section is the first ever study into the K, G and J-integral fracture mechanics of cancellous bone. It used osteoporotic and osteoarthritic cancellous bone from the femoral head of a cohort of ultrasound scanned patients and of some equine vertebral cancellous bone. The study focused on the identification of the dominant independent material variables which affected the compressive and fracture mechanics of cancellous bone, and the differences that were seen between the two different skeletal conditions. In addition to the independent variables, quantitative ultrasound (QUS) scans were performed on the donors of the femoral heads which enabled investigation into QUS’s ability to predict either the compressive or fracture mechanics of bone in-vivo. The study demonstrated that the investigation of the calcaneus using the CUBA clinical system provided the highest level of diagnostic accuracy (AUC: 0.755 - 0.95), followed by the questionnaires, of which the OSIRIS questionnaire was the best performer (AUC: 0.74 – 0.866), and lastly the Sunlight Omnisense results. The best option for the prediction of the lowest feasible DXA T-score was a combination of the CUBA Clinical results, the individual’s weight and the OSIRIS questionnaire (r2 = 45.5%), with potential minor, but significant, support also added by the OST and SOFSURF questionnaires (r2 = 46.8%). The compressive testing demonstrated that osteoporotic and osteoarthritic bone both performed differently with respect to the apparent density, with the osteoporotic bone adhering to the previously published power function relationships, but with the osteoarthritic bone having lower power functions. The stress intensity factor for plane strain testing (KQ or KC) and the critical strain energy release rate results were both influenced primarily by the apparent density with the K values obeying a power relationship to the power of 1.5 and G a relationship to the power 2. However, both the composition and integrity of the collagen network, (demonstrated by collagen cross-link analysis), played roles in the explanation of the fracture mechanics results. The J-integral results were distinctly different to those of the K and G results with regard to their dependence on composition and it is hypothesised that this is due to the structure of the bone having more dominant effects than the apparent density. In conclusion, the fracture mechanics of cancellous bone are contributed to by a complex combination of a number of variables, but with apparent density dominating the K and G fracture mechanics to a power function of between 1 and 2. Currently available QUS systems demonstrated an ability to relate to the Young’s modulus and strength but also, in this study, to the fracture mechanics variables of the cancellous bone from the hip. This relationship is a profound outcome which may help the clinical management of the condition and the fractures when they occur. The dependence on fracture mechanic variables points to a clear causal relationship between the bone fracture parameters and bone condition as underlying factors of osteoporotic fractures.
Open Access
Models for the Dynamic Simulation of Tank Track Components
(Cranfield University, 2006-01) Allen, P.; Hameed, Amer; Goyder, Hugh
This project has been sponsored by QinetiQ Limited (QinetiQ); whose aim it is to model the dynamics of a prototype high-speed military tracked vehicle. Specifically their objective is to describe the mechanism by which force inputs are transmitted from the ground to the vehicle’s hull. Many track running gear components are steel and can be modelled as simple lumped masses or as linear springs without internal damping. These present no difficulty to the modeller. However tracked vehicle running gear also has nonlinear components that require more detailed descriptions. Models for two rubber components, the road wheel tyre and track link bush, and a model for the suspensions rotary damper, are developed here. These three components all have highly nonlinear dynamic responses. Rubber component nonlinearities are caused by the materials nonlinear elastic and viscoelastic characteristics. Stiffness is amplitude dependent and the material exhibits a significant amount of internal damping, which is predominantly Coulombic in nature but also relaxes overtime. In this work, a novel method for measuring the elastic and viscoelastic response of Carbon Black Filled Natural Rubber components has been devised and a ‘general purpose’ mathematical model developed that describes the materials response and is suited to use in multibody dynamic analysis software. The vehicle’s suspension rotary damper model describes three viscous flow regimes (laminar, turbulent and pressure relief), as a continuous curved response that relates angular velocity to damping torque. Hysteresis due to the compression of entrapped gas, compliance of the dampers structure and compression of damper oil is described by a single non-parametric equation. Friction is considered negligible and is omitted from the model. All components are modelled using MSC.ADAMS TM multibody dynamic analysis software. The models are shown to be easily implemented and computationally robust. QinetiQ’s requirement for ‘practical’ track running gear component models has been met.
Open Access
Pre-stressed advanced fibre reinforced composites fabrication and mechanical performance
(Cranfield University, 2006-02) Krishnamurthy, S.; Badcock, R. A.; Hetherington, John G.
Advanced composite materials have high strength-to-weight ratios, corrosion resistance and durability and are extensively used in aerospace, energy and defence industries. This research concentrates on minimising the process-induced residual stresses, and improving the fibre alignment of composites by employing a fibre prestress methodology. A novel flat-bed fibre prestress methodology for autoclave processing of composites was developed. This research investigates the effect of fibre prestress on 1) residual stresses, 2) fibre alignment, 3) static tensile and compression properties and 4) fatigue behaviour of composites. Experimental results show that this prestress methodology, on a 16-ply unidirectional E-glass/ 913 epoxy composite, reduces the residual strain of the composite from –600 µε to approximately zero for a prestress of 108 MPa. The strains measured from optical fibre sensors were in close agreement with those obtained using strain gauge. The results from fibre alignment studies showed that fibre prestressing improved the fibre alignment from 20% of fibres aligned to 0 ° degree in non-prestressed composites to 75% of fibres aligned to 0 ° degree in 108 MPa prestressed composites. Findings have shown that prestressing is beneficial to the static compressive and tensile performance of composites. The results show that fibre prestressing improves the fatigue life and resistance to stiffness degradation in the low stress level fatigue region. Also a change in static and fatigue damage mechanism was observed. The improvement in the static and fatigue properties is due to the reduction in residual stresses and fibre waviness. Overall the fibre prestressing methodology enhances the performance of composites by increasing the resistance to static and fatigue loading. The thesis also suggests that there is an existence of prestress limits to retain optimal material performance.
Open Access
The vulnerability of laser warning systems against guided weapons based on low power lasers
(Cranfield University, 2006-04-28T14:30:20Z) Al-Jaberi, Mubarak; Richardson, Mark A.
Laser assisted weapons, such as laser guided bombs, laser guided missiles and laser beam-riding missiles pose a significant threat to military assets in the modern battlefield. Laser beam-riding missiles are particularly hard to detect because they use low power lasers. Most laser warning systems produced so far can not detect laser beam-riding missiles because of their weak emissions which have signals less than 1% of laser range finder power . They are even harder to defeat because current counter-measures are not designed to work against this threat. The aim of this project is to examine the vulnerability of laser warning systems against guided weapons, to build an evaluation tool for laser warning sensors (LWS) and seekers, and try to find suitable counter-measures for laser beam-riding missiles that use low power lasers in their guidance systems. The project comes about because of the unexpected results obtained from extensive field trials carried out on various LWRs in the United Arab Emirates desert, where severe weather conditions may be experienced. The objective was to help find a solution for these systems to do their job in protecting the tanks and armoured vehicles crews from such a threat. In order to approach the subject, a computer model has been developed to enable the assessment of all phases of a laser warning receiver and missile seeker. MATLAB & SIMULINK software have been used to build the model. During this process experimentation and field trials have been carried out to verify the reliability of the model. This project will enable both the evaluation and design of any generic laser warning receiver or missile seeker and specific systems if various parameters are known. Moreover, this model will be used as a guide to the development of reliable countermeasures for laser beam-riding missiles.
Open Access
Social Structures in the Regular Combat Arms Units of the British Army: A Model
(Cranfield University, 2006-05-04T15:38:52Z) Kirke, C. M. St G.; Bellamy, C D; Killworth, P R P
An original model is presented for describing, analysing, and predicting soldiers’ behaviour in current regular combat arms units in the British Army. It was derived, using social anthropological techniques, during participant observation by a serving British Army officer, and provides more coherent insights than other models of unit life. Its central principle, created for this study, is a plurality of >social structures’. These >social structures’ are separate bodies of ideas, rules and conventions of behaviour which inform groups of people or individuals how to organise and conduct themselves vis-à-vis each other. One >social structure’ operates at any single moment, according to context. Such an approach has not previously been applied to British Soldiers. The model’s top level (low resolution), comprises: the formal command structure, consisting in the unit organisation, the apparatus of rank and discipline, and the framework of official accountability; the informal structure, comprising the conventions of behaviour in the absence of formal constraints; the functional structure, concerning >soldierly’ activity, attitudes, and expectations; and the loyalty/identity structure, encompassing the conventions involved in embracing and expressing membership of the formal hierarchy of groups within and above the unit. Lower levels provide higher resolution, including a typology of informal relationships which encompasses different degrees of closeness and differences or equality in rank. The model’s rigour is established by testing its sensitivity at high resolution to the different conditions of life in historical British armies. The top level, however, and the typology of informal relationships, are found potentially to provide a unifying framework for historical analysis of unit life in the British Army throughout its history. The model’s ability to illuminate current issues in the Army is demonstrated by its application to leadership training for officer cadets and the integration of women into regular combat arms units.
Open Access
Overcoming the odds – integration of intelligence agencies in Columbia
(2006-08-11) Roldan, Vicente Echandia; Hughes-Wilson, John; Brudenell, Anna Maria
Colombia has been seriously affected by terrorism and criminal organizations operating in its territory. FARC, ELN, AUC, and drug trafficking organizations operating in the country have developed into a regional threat and seriously erode democracy and the rule of law for parts of the population. In August 7 2002, President Alvaro Uribe came into office backed by a clear mandate to strengthen the rule of law and the authority of the state throughout the nation. With a clear goal in mind, and recognizing the importance of intelligence in the war against terrorism, the Uribe administration has initiated a pushed for a transformation to increase the effectiveness of intelligence agencies, through, among others, their integration into an effective interagency community. It has proved no easy feat. Similarly to experiences lived by other countries, the intelligence agencies have different backgrounds, confusing tasks and little interest in working closer. Structural, cultural and political issues affect the integration process of the intelligence agencies. Lack of knowledge on the part of the intelligence consumers has also played a historic role in their evolution. Although major improvements have been achieved in the last ten years, through cooperation with countries like the United States of America and the United Kingdom, much remains to be done. While some of the elements required for an effective transformation have been set out, others remain awaiting. In the process of integration some successes have been accomplished, but setbacks have also happened. A continued effort towards further integration, a process that has already been started, will be the only way for the intelligence agencies to defeat an adversary, that in the case of narcoterrorism, threatens there very existence
Open Access
Numerical analysis of buried mine explosions with emphasis on effect of soil properties on loading
(Cranfield University, 2006-10-30T15:59:17Z) Fiserova, D.; Hameed, Amer
During armed conflicts or peace-support operations, most casualties are attributed to vehicle-landmine accidents and thus, mine protection fea-tures are a prerequisite for vehicles serving in these areas. Previously, mine protection research was predominantly experiment driven and focussed on structural deformation. Soil parameters were not observed and the influence of soil was not considered. Accurate soil modelling is necessary because experimental studies have shown that soil, in particular saturated soil, has a significant effect on the magni-tude of landmine blast loading on a vehicle. This research describes a numerical modelling approach for studying soil-blast interaction in landmine explosions. The numerical analysis is carried out using the non-linear dynamic analysis software, AUTODYN. The research progressed from (1) the explosion of hemispherical charge laid on a rigid surface, through (2) the study of the explosion of mine deployed in dry sand, to (3) the validation of the mine explosion in cohesive soil for different setups. A framework for deriving the model for soil with varying moisture contents was proposed. The subject of the study is prairie soil (cohesive soil). Standard soil laboratory data are used to determine soil properties that are then used to define a numerical soil model. Validity of the modelling procedure was ascertained by comparison with experimental results from the horizontal pendulum series that were conducted at Defence R&D Canada – Suffield. The applicability of the model was ascertained for (i) different soil types, (ii) varying moisture content, (iii) different mine deployment, and (iv) various high explosive. The numerical results are in reasonable agreement for all observed range of the moisture content. The model and the methodology is generic and extensible and it is argued that such models greatly complement mine experiments.
Open Access
Micro-machining Techniques for the Fabrication of Fibre Fabry-Perot Sensors
(Cranfield University, 2006-10-30T16:18:07Z) Machavaram, V. R.; Badcock, R. A.; Hetherington, John G.
Fabry-Perot optical fibre sensors have been used extensively for measuring a variety of parameters such as strain, temperature, pressure and vibration. Conventional extrinsic fibre Fabry-Perot sensors are associated with problems such as calibration of the gauge length of each individual sensor, their relatively large size compared to the diameter of optical fibre and a manual manufacturing method that leads to poor reproducibility. Therefore, new designs and fabrication techniques for producing fibre Fabry-Perot sensors are required to address the problems of extrinsic fibre Fabry-Perot sensors. This thesis investigates hydrofluoric acid etching and F2-laser micro-machining of optical fibres to produce intrinsic Fabry-Perot cavities. Chemical etching of single mode fused silica fibres produced cavities across the core of the fibres due to preferential etching of the doped-region. Scanning electron microscope, interferometric surface profiler and CCD spectrometer studies showed that the optical quality of the etched cavities was adequate to produce Fabry-Perot interference. Controlled fusion splicing of etched fibres produced intrinsic Fabry-Perot cavities. These sensors were surface-mounted on composite coupons and their response to applied strain was studied using low coherence interferometry. These sensors showed linear and repeatable response with the strain measured by the electrical resistance strain gauges. To carry out F2-laser micro-machining of fused silica and sapphire substrates, a micro-machining station was designed and constructed. This involved the design of illumination optics for 157 nm laser beam delivery, the design and construction of beam delivery chamber, target alignment and monitoring systems. Ablation of fused silica and sapphire disks was carried out to determine ablation parameters suitable for micro-machining high aspect ratio microstructures that have adequate optical quality to produce Fabry-Perot interference. Cavities were micro-machined through the diameter of SMF 28 and SM 800 fibres at different energy densities. CCD interrogation of these intrinsic fibre cavities ablated at an energy density of 25 x 10 4 Jm -2 produced Fabry-Perot interference fringes. The feasibility of micro-machining high aspect ratio cavities at the cleaved end-face of the fused silica fibres and through the diameter of sapphire fibres was demonstrated. A technique based on in-situ laser-induced fluorescence monitoring was developed to determine the alignment of optical fibres and ablation depth during ablation through the fibre diameter. Ablation of cavities through the diameter of fibre Bragg gratings showed that the heat-generated inside the cavity during ablation had no effect on the peak reflection and the integrity of core and cladding of the fibre. Finally, a pH-sensor, a chemical sensor based on multiple cavities ablated in multimode fibres and a feasible design for pressure sensor fabrication based on ablated cavity in a single mode fibre were demonstrated.
Open Access
Physical modelling of low-cost modifications to the Crump Weir in order to improve fish passage : evelopment of favourable swimming conditions and investigation of the hydrometric effect
(Cranfield University, 2006-12-12T16:44:59Z) Servais, S A; Rhodes, Prof D
More than 350 Crump-type weirs (which are triangular in profile) form part of the Environment Agency's hydrometric network in rivers across England and Wales. These weirs operate as effective measurement structures and are useful over a large flow range. However, they also act as barriers that impede the passage of many species of coarse fish within their natural habitat. The primary aim of this research project was to recommend modifcations to Crump weirs in order to improve fish passage, while still allowing the weirs to fulfll their hydrometric purpose in a reliable way. It was an additional requirement that any proposed solution(s) be both practical and achievable at low-cost. This is in contrast to conventional fish pass solutions, that tend to be expensive, are generally not hydrometrically rated, and most of which were not designed with coarse fish in mind. The method used was a model study conducted in the laboratory, which allowed for a great number of layouts to be trialled. Laboratory research combined with fish swimming data provides a basis for projecting successful fish ascents. Brimpton weir on the River Enborne was chosen as a suitable reference on which to base laboratory model tests. The preferred arrangement (termed a `rotated-V' layout) was found to be a series of baffles located on the downstream slope of the Crump weir. These baffles effectively act as weirs at low flows and roughness elements at high flows. Each baffle has a slot which helps to form a path of ascent for fish. The base closest to the crest was set at the same height as the crest, as this led to optimum low velocities in the slots on the downstream slope. Extensive testing revealed that the proposed solution results in a change in a weir's hydrometric characteristics. However, it was demonstrated that the deviation of the coefficient of discharge is predictable. Therefore, it allows for reliable flow measure- ment to be achieved (subject to a standardised calibration trial using volumetric flow measurement techniques). In addition, a detailed measurement and analysis of wa- ter velocities within the recommended solution strongly suggest that it substantially improves on the fish passage capability of a Crump weir.
Open Access
From capability to concept: Fusion of systems analysis techniques for derivation of future
(Cranfield University, 2007-03-27T09:11:22Z) Sparks, Emma S.; Couldrick, C. A.; Iremonger, M. J.; Allsop, Derek F.
The intent of this thesis is to define a set of processes for use within UK Government dismounted soldier systems research that will provide stakeholders with auditable and traceable information to understand gaps in military capability and justify future procurement decisions. The need for this approach is linked to organisational shifts within the UK Ministry of Defence, and more specifically Government research with the move towards procurement of capability rather than equipment. In conjunction with reducing defence budgets and increased scrutiny, there is a need to prioritise spending to those areas that will provide the most significant enhancement to operational effectiveness. The proposed process suite provides underpinning data to support Government decisions, from definition of military need through to concept design and prioritisation of future research activities. The approach is grounded in the field of systems thinking and systems engineering providing the logical and systematic constructs required for highly complex systems where the human is a central focus. A novel fusion of existing systems tools and techniques enables both subjective data from domain experts and objective data in the form of operational analysis and field trials to be utilised for analysis across the five NATO capability domains, with output defining the relative importance of survivability, sustainability, mobility, lethality and C4I in the context of operational and strategic level military goals as well as wider challenges represented by the doctrinal defence lines of development. Future developments should include alignment with developing pan-MoD initiatives in the form of MODAF, if required by the customer organisation. This would enable generic versions of the process suite to be applied to any defence domain and problem.
Open Access
Design of a Tube Launched Man Portable Unmanned Aerial Vehicle
(2007-03-29T12:49:08Z) Proctor, S; Knowles, Kevin; Bray, Derek
The aim of the MSc was to design a man portable tube launched Unmanned Aerial Vehicle (UAV). The resulting UAV has a vertically staggered wing layout and a V-tail. The UAV has folding wings and tail to allow the deployment from a tube and is small in size to allow it to be man portable. Several design variants were experimented with to verify the staggered wing configuration. The outcome is that a small UAV suitable for tube launching is possible, although the UAV has yet to be launched from a tube.

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