Browsing by Author "Hameed, Amer"
Now showing 1 - 20 of 32
Results Per Page
Sort Options
Item Open Access Application of shell jetting analysis to determine the location of the virtual origin in shaped charges(Elsevier, 2018-07-25) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.Shaped charges are designed to produce high-velocity jets for penetration. During jet formation, the liner collapses and converges at a point source, also known as the virtual origin (VO), along the distance–time plane. The location of the VO must be known to allow the development of penetration analytical models. Here we determined the location of the VO using the ANSYS® Autodyn 2D shaped charge jetting technique. Jetting analysis was conducted for two shaped charges of 18 and 32 mm diameter. The explosive and casing were represented by Eulerian two-dimensional finite difference grids, whereas the liner was modelled using a shell formulation. The summary/history of the jetting analysis was used to determine the VO position in the shaped charges. Interpolating the point of intersection on the liner between the jet velocity (U-Jet) and the cumulative jet mass revealed the location of the VO at a distance equivalent to approximately two-thirds of the inner cone diameter of the shaped charges, in agreement with earlier studies based on different methods. Validation of this technique using the DiPersio, Simon and Merendino (DSM) model based on the Allison-Vitalli equation also showed good agreement with the numerical results.Item Open Access Armoured vehicle manufacturing in the Gulf States challenges and future vision: a systems engineering perspective(Cranfield University, 2019) Aljeeran, Isa Khalifa Abdulla; Hameed, Amer; McCormack, John; Adcock, RickThe armoured vehicles manufacturers (AVMs) in the Gulf States encounter many difficulties related to their current performance, their customers' circumstances and the interactions between them. The AVMs are Small and Medium Enterprises (SME), owned by entrepreneurs who manage their organisations intuitively, leading to likely performance degradation which affects their outputs and thus customer satisfaction. On the other side, the customers lack essential elements of the acquisition process such as the non-existence of published defence strategies documents, customer needs not being precisely clarified to the developers, demand fluctuation, customer individuals’ knowledge being insufficient to contribute toward developing the intended values, etc. Third, the interactions between AVMs and their stakeholders, the customer in particulars, do not rise to the level of product importance. These environments form the dynamic environment that AVMs in the Gulf states currently face besides other circumstances, such as the fierce competition worldwide, considerably changes regarding the threats and needs, constant technology advancements, and political challenges, which combined may hinder AVMs from attaining their instant (customer satisfaction) and future (market sustainability) goals. Therefore, this thesis pursues aims to enable the owners/managers (entrepreneurs) of AVMs in the Arabian Gulf States to employ their resources efficiently to deliver innovative values that satisfy the needs of all of their stakeholders, customers in particular, within the dynamic environment. Dealing with the dynamic environment requires intensive planning and the execution of known managerial disciplines, such as strategy, supply chain and business to business (B2B) interactions along with utilising essential tools provided by the System Engineering (SE) discipline. The latter subject has adequate means to optimise the strategy and supply chain technical tools by integrating them with the related managerial tools to enhance the development efforts. Moreover, organised interactions among various related entities that share a well-designed network enforce the desirable integration and enhance the relationship in the B2B context which ensures customer satisfaction, confirms the AVM market’s sustainment, strengthens the defence industry and attains arms independence. These efforts must be monitored and controlled by higher national authorities’ substantial strategies to ensure that the national goals are achieved. Therefore, the author suggests a conceptual model to guide all interested parties, the AVM’s management, to enhance their performance by considering all essential managerial and technical aspects. The model also emphasises the importance of interactions in enforcing the applications of the strategic, design, production and test and evaluation process to enable AVMs to enhance their product development in order to capture customer satisfaction and succeed in business. The success of the national AVMs will lead to the attainment of one of the most important national objectives, i.e. arms independence.Item Open Access The bactericidal effect of shock waves(Institute of Physics, 2014-05-07) Leighs, J. A.; Appleby-Thomas, Gareth J.; Wood, David C.; Goff, Michael J.; Hameed, Amer; Hazell, P. J.There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary bodies. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shockwaves has produced conflicting conclusions. The work presented here used an established and published technique in combination with a single stage gas gun, to shock and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling. Survival data against peak sample pressure for recovered samples is presented alongside control tests. SEM micrographs of shocked samples are presented alongside control sets to highlight key differences between cells in each case.Item Open Access Blast analysis of composite V-shaped hulls : an experimental and numerical approach(2012-06-28) Follett, S.; Hameed, AmerDuring armed conflicts many casualties can be attributed to incidents involving vehicles and landmines. As a result mine protective features are now a pre-requisite on all armoured vehicles. Recent and current conflicts in Iraq and Afghanistan have shown that there is a requirement for vehicles that not only provide suitable protection against explosive devices but are also lightweight so that they may travel off-road and avoid the major routes where these devices are usually planted. This project aims to address the following two topics in relation to mine protected vehicles. 1. Could composite materials be used to replace conventional steels for the blast deflector plates located on the belly of the vehicle, and 2. How effective and realistic is numerical analysis in predicting the material response of these blast deflectors. It also looks into the acquisition and support of new equipment into the armed services, where the equipment itself is but one small element of the system involved. The first topic has been addressed by conducting a number of experimental tests using third scale V-shaped hulls manufactured from steel and two types of composite, S2 glass and E glass. These experiments found that, on a weight-for-weight equivalency, the S2 glass was by far the superior material, with very little damage to the outside shape of the hull. The steel was significantly deformed after testing and the E glass, although also did not deform as such, did experience a severe amount of matrix cracking leading to significant loss of structural integrity in that the hull could be easily flexed by hand after the tests. One S2 glass hull was also subjected to a further two explosive tests and although the amount of delamination was severe at the base of the hull there was very little geometry lost to the outside of the shape. The numerical modelling work consisted of the modelling of the mine blast phenomenon in autodyn and comparisons with published experimental and numerical work, with the results in reasonably good agreement. The second part consisted of comparing flat S2 glass plates subjected to varying charge sizes both experimentally and numerically in order to validate the material model, with good agreement. The final stage involved using the validated material model and re-creating the tests done on the V-shaped hulls. The results here at first were not in agreement, but with development of the model and the limitations from the experimental data collection methods applied a model that, when viewed with the experimental results, gave a reasonable representation of the experimental work was created. The management section of the thesis considers previous equipment purchases and what went wrong during their implementation. The Through Life Capability Management model is assessed in relation to an all composite vehicle and identifies some key questions and areas of concern, such as how the management of the DLOD trade-off process should be conducted.Item Open Access Closed vessel burning behavior and ballistic properties of artificially-degraded spherical double-base propellants stabilized with diphenylamine(Elsevier, 2019-07-24) Tırak, Ergun; Moniruzzaman, Mohammed; Degirmenci, Ercan; Hameed, AmerThe purpose of solid propellants is to generate gas, which expands to accelerate (and spin, in the case of rifled barrels) a gun projectile so that it achieves the desired launch velocity at the muzzle. Some of the important properties of a propellant are the burning rate and vivacity, both of which strongly influence gun performance and projectile range. However, nitrate ester propellants undergo physical and chemical degradation during storage and this can change the burning rate and/or vivacity, either reducing the propulsive efficiency or increasing the safety risk to the operator during transportation and handling. Here we report the effect of aging on the burning rate and vivacity of spherical double-base propellants containing diphenylamine (DPA) as the main stabilizer. We tested three sets of propellants that were artificially aged at 80 °C for 5.3, 10.6 and 21.6 days, equivalent to 5, 10 or 20 years of aging at 25 °C according to STANAG 4582. It was found that DPA was progressively lost from the propellants during aging, with the greatest loss observed in propellants aged for the longest time. The DPA was able to fulfil its stabilisation role of propellant when NG was up to 14%, however, failed to stabilize when the nitroglycerin content was nearer to 20%. Aging caused changes in the burning rate and vivacity compared to the unaged propellant batch. The burning rate of propellant containing ˜20% nitroglycerin exceeds the burning rates of samples containing 12–14% nitroglycerin. The limited role of DPA as a stabilizer for double-base propellants is discussed. The DPA stabilized double base propellant may undergo significant changes during storage, making them unsuitable for their designated use.Item Open Access A comparison of the ballistic behaviour of conventionally sintered and additively manufactured alumina(Elsevier, 2019-06-20) Appleby-Thomas, Gareth J.; Jaansalu, Kevin; Hameed, Amer; Painter, Jonathan; Shackel, JamesProduction of ceramic armour solutions on-demand/in-theatre would have significant logistical and military advantages. However, even assuming that such technologies could be successfully deployed in the field, such near net-shape manufacturing technology is relatively immature compared to conventional sintering of ceramics. In this study, the ballistic performance of a series of additively manufactured (AM)/rapidly-prototyped (RP) alumina tiles of 97.2% of the density of Sintox FA™ were investigated using both forward- and reverse-ballistic experiments. These experiments, undertaken with compressed gas-guns, employed the depth-of-penetration technique and flash X-ray as primary diagnostics to interrogate both efficiency of penetration and projectile-target interaction, respectively. The RP alumina was found to exhibit useful ballistic properties, successfully defeating steel-cored (AP) 7.62 × 39 mm BXN rounds at velocities of up-to c.a. 850 m/s, while exhibiting comparable failure modes to conventionally sintered armour-grade Sintox FA™. However, where a <1% by vol. Cu dopant was introduced into the RP material failure modes changed dramatically with performance dropping below that of conventionally sintered alumina. Overall, the results from both sets of experiments were complimentary and clearly indicated the potential of such RP materials to play an active role in provision of real-world body armour solutions provided quality control of the RP material can be maintained.Item Open Access Comparison of the microstructure of machined and laser sintered shaped charge liner in the hydrodynamic regime(Springer, 2019-07-30) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.To gain further insight into the mechanisms underlying jet formation and elongation of laser sintered shaped charge liners under high strain rate deformation, Cu–Cr–Zr alloy liners fabricated by selective laser sintering process were deformed by explosive detonation. Their as-manufactured (liner) and resultant (slug) microstructure have been investigated in comparison with those of traditional machined liners employing both optical and scanning electron microscopy. The resultant slug microstructure of both machined and laser sintered liners revealed a smaller refined equiaxed grain size consistent with traditionally fabricated liners, characteristic of dynamic recrystallization. The disappearance of the (originally present) pores in the post-shot/recovered material microstructure was observed for laser-sintered liners. Comparison of the forward and rear region of the slug revealed variations in liner deformation, a result attributed to temperature variation across the slug. In contrast with the machined liner, a unique feature of precipitation, observed in the ending (slug) microstructure of the laser sintered liner is indicative of the associated extreme high strain and strain rate liner deformation which occurred during slug formation. The precipitates are likely compounds of Chromium and Zirconium which are constituents of the laser sintered copper alloy—the first time this observation is reported. This study provides a link between post charge evolution microstructure and liner manufacturing processes, potentially providing a new route to help optimise jet formation and effectiveness.Item Open Access Compensation of low performance steering system using torque vectoring(2014-11-07) Awan, M. A.; Hameed, Amer; Purdy, David J.In this work torque vectoring methods are used to compensate for a low performance steer-by-wire system. Currently a number of vehicle manufacturers are considering introducing steer-by-wire into their range of vehicles. Some of the key concerns for the manufacturers are safety and cost. The safety can be subdivided in the integrity of the steering system and the effect on handling. The focus of this study is the use of low cost steering actuators on a vehicle and identify its effects on the vehicle's handling response. The test vehicle is dune buggy modified to accommodate the low performance steer-by-wire system without a direct mechanical link between the steering wheel and the wheels and equipped with various sensors to data recording. In order to investigate the influence of torque vectoring system on the steer-by-wire, an eight degrees of freedom vehicle model in Matlab/Simulink has been developed. The eight degrees of freedom are longitudinal and lateral translations, yaw and roll motion and rotation of each wheel. The Matlab/Simulink model also includes the dynamics of the actuators, which is validated against the experimental data. The actuator was shown to have a bandwidth of less than 0.3 Hz. The eight degrees of freedom model's response was validated against experimental data for both steady state and transient response up to 0.5 g. The tyre forces and moments are implemented by using the Dugoff tyre model, which has been validated against experimentally measured data. The torque vectoring system uses the cascade approach based on a reference model, which uses a two degrees of freedom (bicycle model) to generate the reference signal for control purposes. The upper level yaw controller is based on the optimal control theory and uses the LQR (Linear-quadratic regulator) approach. The lower level wheel slip controller is based on a slidingmode structure and prevents tyre force saturation. The simulation results show that the vehicle augmented with the torque vectoring system outperforms the low performance steer-by-wire vehicle and also the vehicle with conventional steering arrangement.Item Open Access Conceptualizing, defining, and modelling supply chain management : an objective oriented approach.(2022-08) Alkebaisi, Hussain K; Allen, Robert; Hameed, AmerAlthough it has been more than three decades since the term Supply Chain Management (SCM) was first introduced, there are still divergent views and different interpretations amongst scholars and practitioners about its meaning. The literature lacks consensus on a precise definition of SCM and presents a plethora of different perspectives. A unified conceptual or theoretical model has not yet been acknowledged, and the existing frameworks lack the call for a holistic model that encompasses the essence of the concept. With this disagreement on what SCM is, there are repeated calls to achieve consensus on a unified definition, a unified understanding, a unified conceptual model, and a unified framework of SCM. The argument in the literature is that achieving consensus among scholars and practitioners will improve research and practice and the SCM discipline. The literature revealed that the prevalent and the most recommended approach of conceptualising SCM is the process orientation. However, there is no evidence in the literature that an objective-oriented approach was investigated in resolving those theoretical issues, and neither has a Grounded Theory research method been applied to that end.Through an objective-orientated approach and applying the grounded theory method, it is found that the majority of the theory behind SCM is about managing business activities and achieving business goals through the communication, cooperation, collaboration, and integration within and across firms in a supply chain or network. The proposed name of the identified theory is ‘Business Relations Management Theory.’ The theory states that individuals, organisations, societies and nations achieve better performance and outcomes through communication, cooperation, collaboration, and integration. A literature-based thematic analysis showed that SCM is being used as a synonym for Supply Management, Business Relations Management (BRM), or a combination of both. Also, an assessment survey that included more than 200 managers and employees from different countries showed unclear or limited understanding of the identified theory and perspective of BRM. Accordingly, this research presents the theory and perspective of BRM and asserts that the term Supply Chain Management (SCM) should be replaced with Business Relations Management (BRM). SCM, as a term, limits the benefits of communication, cooperation, collaboration, and integration to a chain or network of firms and enterprises within the production sector. In contrast, the Business Relations Management (BRM) concept generalises the benefits to all sectors and all stakeholders, including the final customers, consumers, and services recipients. In addition, universities or business schools are advised to replace SCM with ‘Supply Management’ or another name that combines supply and demand management fields. A Feedback survey included a group of managers and employees from different sectors in Bahrain showed a high level of satisfaction and acceptance of the outcomes of this research, the researcher’s argument, and recommendations. The feedback survey outcomes led to the conclusion that the objective orientation was an effective approach to conceptualise SCM, and there is a probability of higher acceptance of the outcomes of this research and, consequently, achieving consensus among academics and practitioners.Item Open Access Determination of Residual Stress Distributions in Autofrettaged Thick Cylinders(Cranfield University, 2008-10-07T12:21:57Z) Gibson, Michael C.; Hameed, AmerHigh pressure vessels such as gun barrels are autofrettaged in order to increase their operating pressure and fatigue life. Autofrettage causes plastic expansion of the inner section of the cylinder – setting up residual compressive stresses at the bore after relaxation. Subsequent application of pressure has to overcome these compressive stresses before tensile stresses can be developed, thereby increasing its fatigue lifetime and safe working pressure. A series of Finite Element (FE) models of hydraulic autofrettage were created, to establish the correct boundary conditions required and means of developing accurate but computationally efficient models. Close agreement was observed between the solutions obtained from the developed models and those from existing analytical and numerical models. These initial models used a simplistic bi- linear stress-strain material representation; this deficiency was then addressed through the development of two means of creating radial position dependent non-linear material behaviour within FE, crucial for accurate prediction of residual stresses. The first utilised a method of altering the elastic properties of the material to achieve nonlinear stress-strain response. This provided accurate results that compared well with existing methods, but was unable to be used in simulation of swage autofrettage due to its elastic nature. The second method achieved non- linear behaviour through direct manipulation of the stress and plastic strain states of the FE model at a fundamental level. This was hence suitable for arbitrary loading procedures, including swage autofrettage. A swage-like model that applied deformation via a band of pressure was developed, to investigate the influence of localised loading and shear stresses that result on the residual stress field. A full model of swage autofrettage was then developed, which was optimised on the basis of accuracy and solution effort. It was then used to investigate the effects of various mandrel and contact parameters on the creation of residual stresses. The model is suitable for use in future optimisation studies of the swage autofrettage procedure.Item Open Access Dynamic qualitative bolt force measurements for investigating influence factors on the pushout effect of small calibre ammunition(AIP Publishing, 2019-06-25) Muster, Michael; Hameed, Amer; Wood, DavidA small calibre weapon system consists of the weapon and the ammunition. In the case of bolt action rifles during the process of firing, the breech is a rigid bearing which prevents the casing from being pushed out. However, not the whole pushout force is taken by the bolt. Due to friction forces at the casing boundary, the chamber of the weapon can absorb a significant part of the pushout force. The duration of the pushout force is in the order of milliseconds. Piezoelectric strain gauges are capable of recording such short time events qualitatively. To increase the measurability of force obtained from raw signal, is filtered using a bandpass filter and applying a signal envelope. The results from the strain gauges are verified by a piezoelectric force washer. In this paper, two different lubrication states and two different casing materials are analysed to evaluate their influences on the force absorbed by the bolt. The analysis indicated that lubricated casings lead to bolt forces which are more than three times higher when compared unlubricated casings. The unlubricated steel casing also showed a significant lower bolt force when compared with the regular brass casing. However, this effect is reversed, if the casing is lubricated. This work demonstrates how to measure highly dynamic events. The acquired results can be directly applied to 5.56x45 bolt action rifles. These measurements may also have a significant influence on self-loading rifles, since the process of reloading is also dependent on the pushout force. The general application area is target competitive shooting and military purposes.Item Open Access The dynamic response of dense 3 dimensionally printed polylactic acid(Springer, 2019-05-22) Agu, Henry; Hameed, Amer; Appleby-Thomas, Gareth J.; Wood, DavidPolylactic acid (PLA) is commonly used as a feedstock material for commercial 3D printing. As components manufactured from such material become more commonplace, it is inevitable that some of the resultant systems will be exposed to high strain-rate/impact events during their design-life (for example, components being dropped or even involved in a high-speed crash). To this end, understanding the shock properties of polylactic acid, in its role as a major raw material for 3D printed components, is of particular importance. In this work, printed samples of PLA were deformed by one-dimensional shock waves generated via the plate impact technique, allowing determination of both the Hugoniot Equation of State (EOS) and shear strength of the material. Both linear and non-linear EOS forms were considered in the US-Up plane, with the best-fit found to take the general form US=1.28+3.06−1.09Up2" role="presentation" style="display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border-width: 0px; border-style: initial; position: relative;">US=1.28+3.06−1.09U2pUS=1.28+3.06−1.09Up2 in the Us−Up" role="presentation" style="display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border-width: 0px; border-style: initial; position: relative;">Us−UpUs−Up plane, consistent with other polymers. Use of lateral Manganin gauges embedded in the material flow allowed consideration of lateral stress evolution at impact pressures ranging from 0.3 to 4.0 GPa. Shear strength was observed to increase with impact stress, however, with minimal strengthening behind the shock front. Deviation of the measured stress from the predicted elastic measurement (corresponding to the PLA’s Hugoniot Elastic Limit) was observed at longitudinal stress of 0.90 ± 0.05 GPa, within range of polymeric materials of similar characteristics—the first time this important parameter has been measured for PLA. As a result, this material characterisation will allow numerical modellers to accurately predict the structural response of PLA-based components/structures against high strain rates such as impacts or drops.Item 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.Item Open Access An investigation into the effect of the gilding jacket on 12.7 mm armour-piercing projectile penetration of armour materials(Cranfield University, 2018) Lesmana, D.; Hameed, Amer; Appleby-Thomas, Gareth J.The influence of both the bullet jacket and projectile core hardness for 12.7-mm armour piercing (AP) rounds has been investigated using a variety of different experiments with the aim of optimising projectile performance. The research was designed to elucidate the role of these two elements in the penetration process, building on work elsewhere in the literature. A combination of forwards and reverse (target impacting stationary projectile) investigations provided insight into both penetration efficiency and resultant target failure modes. The results of these experiments, backed by a pressure-gauge based impact technique, were validated via numerical modelling. It was observed that the jacket appears to serve three inter-linked functions: pre-damage of the target; cushioning of the AP core and confinement of the core. Modifying the core hardness showed that penetration efficiency was maximised when this hardness was greater than / overmatched that of the target (Armox Advance) plate. This behaviour was more pronounced when a thicker (9 rather than 5-mm thick) target plate was employed, suggesting that projectile / target interaction time was of particular importance (a potential confinement effect). However, for the 9-mm target plates where overmatch did not occur, reduced penetration / a ‘ceramic-like’ response was observed. In a similar manner, the presence of a jacket had the greatest effect for thicker plates. However, this confinement effect was complemented by pressure gauge results which suggested that the presence of the jacket enhanced energy coupling into the target (and, in corollary, that the jacket prevented premature and excessive loading of the core). In turn, numerical simulations provided further evidence that the jacket appeared to be protecting (cushioning) the core on impact. However, these also highlighted the extent of pre-damage caused by the jacket.Item Open Access Investigation of the high-strain rate (shock and ballistic) response of the elastomeric tissue simulant Perma-Gel®(Elsevier, 2016-04-01) Appleby-Thomas, Gareth J.; Wood, D. C.; Hameed, Amer; Painter, Jonathan; Le-Seelleur, V.; Fitzmaurice, Brianna C.For both ethical and practical reasons accurate tissue simulant materials are essential for ballistic testing applications. A wide variety of different materials have been previously adopted for such roles, ranging from gelatin to ballistics soap. However, while often well characterised quasi-statically, there is typically a paucity of information on the high strain-rate response of such materials in the literature. Here, building on previous studies by the authors on other tissue analogues, equation-of-state data for the elastomeric epithelial/muscular simulant material Perma-Gel® is presented, along with results from a series of ballistic tests designed to illustrate its impact-related behaviour. Comparison of both hydrodynamic and ballistic behaviour to that of comparable epithelial tissues/analogues (Sylgard® and porcine muscle tissue) has provided an insight into the applicability of both Perma-Gel® and, more generally, monolithic simulants for ballistic testing purposes. Of particular note was an apparent link between the high strain-rate compressibility (evidenced in the Hugoniot relationship in the Us-up plane) and subsequent ballistic response of these materials. Overall, work conducted in this study highlighted the importance of fully characterising tissue analogues – with particular emphasis on the requirement to understand the behaviour of such analogues under impact as part of a system as well as individually.Item Open Access Lethality analysis based on a fragmentation model for naturally fragmenting shells(2011-12-31T00:00:00Z) Zagorecki, A.; Hameed, Amer; Shukla, A.Item Open Access Modelling and design of a dual channel magnetorheological damper(2013-10-08) Bhatnagar, R.; Hameed, Amer; Purdy, David J.A limitation with the current analytical models for predicting the performance of a magnetorheological (MR) damper is that they fail to capture the hysteretic variation of force versus velocity variation correctly. This can significantly underestimate the damper force and overestimate the dynamic range of the device. In this work a transient analytical fluid dynamics model is developed by using a combination of Laplace and Weber transform and Duhamel’s superposition of velocity boundary condition, to overcome these limitations. The solution of the system of nonlinear simultaneous equations, obtained by applying mass flow balance, velocity compatibility conditions and force equilibrium of Bingham plastic plug flow, gives the damper force. This method is shown to generate direct and inverse model of an MR device. The proposed model has been validated against a commercially available MR damper at low speed, to a range of test signals. The mean error using the above model has been shown to be 5% for all the test signals. This compares well with three conventional models which give; transient constant velocity model 35%, quasi static model 35% and phenomenological model 35%. The phenomenological model gives 10% mean error for a sinusoidal input signal. The application of the proposed analytical model has been demonstrated by the design of a novel dual channel damper. The design of the electromechanical components has been shown to be np-hard problem and the optimisation using genetic algorithm has been applied to minimise the volume and electrical time constant. The performance of the dual channel damper has been simulated for various combinations of values of shear yield stress for two channels. Compared to the conventional single channel damper the novel design is shown to give 30% higher damper force, 50% improved dynamic range and limits the effect of transients to within 10% of the damper force. The dual channel damper is an effective solution to resist the onset of turbulent flow in the channels up to 20m/s piston velocity.Item Open Access Models for the Dynamic Simulation of Tank Track Components(Cranfield University, 2006-01) Allen, P.; Hameed, Amer; Goyder, HughThis 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.Item Open Access Novel approaches to breech force and bullet ricochet measurement for small arms fire(2020-04) Mister, Michael; Hameed, Amer; Wasmer, KilianDanger zones are defined as an area on shooting ranges in which there is a high risk of harm. Risk driving factor for the size of the danger zone is the ammunition used, properties and ricochet behaviour of the specific ammunition design. The danger zone is of interest because a wrong estimation may lead to unwanted damage to the shooter’s far environment. The distant environment is less affected when it comes to weapon breech damage. However, the internal ballistic breech investigation during the process of firing is of high relevance for the safety considerations of the shooter. The purpose of this study is to show the influence of novel ballistic measurement devices on recent safety considerations. It is an experimental research study that looks at internal and terminal ballistic effects. The pushout force was investigated with a separately developed weapon breech, capable of measuring loads in a dynamic manner. The other investigated parameter was the ricochet danger which was also investigated with a device developed during the project. Both parameters lead to new safety considerations. During this thesis it became evident that the most relevant parameter for an accurate ricochet quantification is the momentum of the fragment. This measurement is possible thanks to a novel type of accelerometer equipped sensor plates developed in this work. The other main finding of this thesis is the fact that lubricated ammunition casings, irrespective of whether with water or oil lubrication, leads to a significant rise in pushout force. This pushout force is taken up by the breech and leads to safety-relevant rises of internal forces on the breech. Both measurement approaches need to be taken into account when it comes to future safety considerations of small arms fire.Item Open Access A novel dual-spin actuation mechanism for small calibre, spin stabilised, guided projectiles(2021) Norris, James J.; Hameed, Amer; Economou, John T.Small calibre projectiles are spin-stabilised to increase ballistic stability, often at high frequencies. Due to hardware limitations, conventional actuators and meth ods are unable to provide satisfactory control at such high frequencies. With the reduced volume for control hardware and increased financial cost, incorporating traditional guid ance methods into small-calibre projectiles is inherently difficult. This work presents a novel method of projectile control which addresses these issues and conducts a systems level analysis of the underlying actuation mechanism. The design is shown to be a viable alternative to traditional control methods, Firstly, a 7 Degree-of-Freedom (DoF) dynamic model is created for dual-spin pro jectiles, including aerodynamic coefficients. The stability of dual-spin projectiles, gov erned by the gyroscopic and dynamic stability factors is given, discussed and unified across available literature. The model is implemented in a Matlab/Simulink simulation environ ment, which is in turn validated against a range of academic literature and experimental test data. The novel design and fundamental operating principle are presented. The actuation mechanism (AM) is then mathematically formulated from both a velocity change (∆V ) and a lateral acceleration (a˜) perspective. A set of axioms are declared and verified using the 7-DoF model, showing that the inherently discrete system behaviour can be controlled continuously via these control variables, ∆V or a˜. Control state switching is simplified to be instantaneous, then expanded to be generically characterised by an arbitrarily complex mathematical function. A detailed investigation, parametric analysis and sensitivity study is undertaken to understand the system behaviour. A Monte Carlo procedure is described, which is used to compare the correction cap abilities of different guidance laws (GLs). A bespoke Zero-Effort-Miss (ZEM) based GLis synthesised from the mathematical formulation of the AM, with innately more know ledge of the system behaviour, which allows superior error correction. This bespoke GL is discussed in detail, a parametric study is undertaken, and both the GL parameters and PID controller gains are optimised using a genetic algorithm. Artificial Intelligence (AI) Reinforcement learning methods are used to emulate a GL, as well as controlling the AM and operating as a GL, simultaneously. The novel GLs are compared against a traditional proportional navigation GL in a nominal system and all GLs were able to control the AMs, reducing the miss distance to a satisfactory margin. The ZEM-based GL provided superior correction to the AI GL, which in turn provided superior correction over proportional navigation. Example CAD models are shown, and the stability analysis is conducted on the geometry. The CAD model is then used in CFD simulations to determine aerodynamic coefficients for use in the 7-DoF dynamic model. The novel control method was able to reduce the 95% dispersion diameter of a traditional ballistic 7.62mm projectile from 70mm to 33mm. Statistical data analysis showed there was no significant correlation or bias present in either the nominal or 7-DoF dispersion patterns. This project is co-sponsored by BAE Systems and ESPRC (ref. 1700064). The con tents of this thesis are covered by patent applications GB2011850.1, GB 2106035.5 and EP 20275128.5. Two papers are currently published (DOI: 10.1016/j.dt.2019.06.003, the second DOI is pending) and one is undergoing peer review..