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Potential of non-contact dynamic response measurements for predicting small size or hidden damages in highly damped structures
Get PDFVibration-based structural health monitoring (SHM) is essential for evaluating structural integrity. Traditional methods using contact vibration sensors like accelerometers have limitations in accessibility, coverage, and impact on structural dynamics. Recent digital advancements offer new solutions through high-speed camera-based measurements. This study explores how camera settings (speed and resolution) influence the accuracy of dynamic response measurements for detecting small cracks in damped cantilever beams. Different beam thicknesses affect damping, altering dynamic response parameters such as frequency and amplitude, which are crucial for damage quantification. Experiments were conducted on 3D-printed Acrylonitrile Butadiene Styrene (ABS) cantilever beams with varying crack depth ratios from 0% to 60% of the beam thickness. The study utilised the Canny edge detection technique and Fast Fourier Transform to analyse vibration behaviour captured by cameras at different settings. The results show an optimal set of camera resolutions and frame rates for accurately capturing dynamic responses. Empirical models based on four image resolutions were validated against experimental data, achieving over 98% accuracy for predicting the natural frequency and around 90% for resonance amplitude. The optimal frame rate for measuring natural frequency and amplitude was found to be 2.4 times the beam’s natural frequency. The findings provide a method for damage assessment by establishing a relationship between crack depth, beam thickness, and damping ratio.Sensor
The case for macroscale through-thickness reinforcement for hybridised multifunctional composites
No full textEmbedding fundamental functional properties like thermal and electrical conductivity in composites is key in deriving a range of additional industrially-useful functionalities. Through-thickness reinforcement (TTR) can achieve this via material hybridisation. These techniques are sometimes unattractive due to the need for specialised equipment and a shortage of available expertise to support TTR. A knowledge gap exists in understanding the interplay between reinforcement size and functional behaviour especially where reinforcements go beyond traditional geometrical constraints. Here we demonstrate that the addition of macroscale (≥1 mm) TTR can significantly improve electro-thermal energy transfer as well as provide effective tailoring functionality in composites.This work was supported by the Royal Academy of Engineering Research Fellowship - multifunctional z-direction hybridization of composites project which has received funding from the Royal Academy of Engineering (Grant agreement RF2223-22-208). (Royal Academy of Engineering|RF2223-22-208)SAMPE Europe Conference 202
Co₂ separations and the role of surface functionality
No full textManovic, Vasilije - Associate SupervisorTo curb irreversible environmental effects of climate change, urgent measures
must be taken to limit anthropogenic emissions and achieve net-zero carbon
goals by 2050. Carbon capture technology to meet these goals is wide ranging,
with novel methods directed at biogas upgrading or direct air capture. Biogas is
produced from the anaerobic digestion of biological waste and considered a
valuable renewable energy source; to produce biomethane for use
interchangeably with natural gas. However, widespread use of established
separation processes is limited, primarily due to low CO₂ selectivity or high
energy demands of cyclic operation. One method to tackle these issues is the
development of novel sorbents for use in pressure swing adsorption, targeting
maximum CO₂ capacity and selectivity, while minimising regeneration energy
penalties. Adsorbents incorporated with amines can meet one of these criteria,
selectively adsorbing CO₂, but require high regeneration energies. Herein, the
adsorption performance of a diverse range of amines grafted on mesoporous
silica at varying densities is studied, to understand developing adsorption
mechanisms, and identify the ideal degree of functionalisation for gas
separations. It was found that although high amine densities led to the highest
enhancement in CO₂ capacity and selectivity, moderate levels have comparable
selectivity and capacity in isothermal adsorption-desorption conditions, standing
out are di- and secondary amines. Diamine loadings achieved an adsorption
capacity of 1.12 mmol/g, a heat of adsorption of 35-50 kJ/mol, and an IAST
selectivity of 374 at CO₂ partial pressures of 40 kPa. Secondary amines had a
low capacity of 0.67 mmol/g, but a higher heat of adsorption comparatively. The
optimal binder formulation for pellet preparation of amine grafted silicas was also
studied, a necessary step in conducting laboratory scale fixed-bed adsorption
studies. When applying amines for ambient air adsorption, very high amine
loadings result in slow adsorption kinetics, rendering the advantage of their high
capacity debatable. Moderate loadings of primary and triamine under humid
conditions have higher adsorption rates >250 µg/g/min, making them more suited
for fast cycle processes.MSc by Research in Energy and Powe
Improved deposition modelling for heat exchangers in pulverised fuel combustors
Get PDFOakley, John E. - Associate SupervisorCo-firing biomass with coal is a promising and cost effective solution to reduce CO₂
emissions derived from the use of fossil fuels in existing power generation systems.
However, deposition on heat exchangers (i.e. fouling and slagging) represents a major
problem in power plants as it reduces boiler thermal efficiency, causes fireside
corrosion and compromises the life of components until forced shutdown. The high
complexity and multidisciplinary nature of this problem, which varies with boilers, fuel
composition and combustion conditions, has made its prediction a major challange.
In this thesis, Computational Fluid Dynamics (i.e. CFD) software, Ansys Fluent® , was
used and its features were enhanced with three User Defined Functions (i.e. UDFs)
which were modified to predict deposit accumulation, deposit shape and surface
temperature. The Eulerian-Lagrangian model was enabled to describe the gas flow field
around tubes and the solid ash particle trajectories respectively. Unsteady simulations
were run and the combined effect of deposit growth and surface temperature on the
deposition flux calculations was included.
Experiments of co-firing Daw Mill coal-12 wt.% Miscanthus were carried out in a 100
kWth pilot-scale pulverised fuel (PF) combustor at Cranfield. The flue gas temperature
and composition were recorded and fly ash samples were analysed to fit the Rosin
Rammler ash particle size distribution model. Moreover, deposits were collected on
cooled ceramic probes to measure the deposition flux and the chemical composition.
The CFD model was applied to predict deposition on the cooled ceramic probes and the
experimental results were used to set boundary conditions and to validate the model.
The main challenges met in this work have been highlighted and possible solutions
suggested. The model included several deposition mechanisms for ash particles and
vapours and took into account the stickiness of the surface and the ash particles.
Deposition has been studied for varying probe configurations and surface temperatures
and the comparison between the experimental and modelling results was promising.
Alkali vapour condensation enhanced the formation of deposit onto clean surfaces at
lower temperatures. However, inertial impaction was the main deposition mechanism
for bigger ash particles.PhD in Energy and Powe
Structural reliability assessment of complex offshore structures based on non-intrusive stochastic methods
Get PDFKolios, Athanasios - Associate SupervisorOffshore Wind Turbines (OWTs) are deployed in harsh environments often characterised
by stochastic loads and resistance properties. It becomes necessary to propose an
accurate and efficient approach for the assessment of uncertainties in material properties
and operating environments. Structural Reliability Assessment (SRA) as a form of
uncertainty analysis is a useful tool in the design of structures because it can directly
quantify how uncertainty about input parameters can affect structural performance. First,
this thesis developed a novel non-intrusive SRA method for an OWT jacket structure
which maps the response of the structure through a finite number of simulations to
develop a response surface and then employ First Order Reliability Methods (FORM) to
evaluate the reliability index. This method was validated against a commercial FEA
package (DesignXplorer© from ANSYS) which employs direct simulations to predict the
probability of failure. The method developed was used in performing stochastic sensitivity
analysis of the variables imposed on the OWT support structure. The results from this
study, reveals that the uncertainties in the design wind speed is a design driving factor
and the hydrodynamic load effects are secondary to this, for the ultimate (ULS), and
fatigue limit states (FLS), among others. Second, the SRA of the same structure
subjected to pitting corrosion-fatigue was assessed using a damage tolerance modelling
approach. The non-intrusive formulation in this study used an Artificial Neural Network
(ANN) response surface modelling technique instead of the Multivariate (Quadratic)
Polynomial Regression (MPR) method used previously apart from the FEA to represent
the crack propagation regimes. The results reveal that for the inherent stochastic
conditions, the structure becomes unsafe after the 18th year, before the attainment of the
design life of 20 years, among others. The benefit of this approach is that it allows for
high fidelity computational tools to be employed for the analysis, hence extending its
applicability to various specialist engineering problems through the advanced modelling
techniques.PhD in Energy and Powe
Inverse design of cellular structures with the geometry of triply periodic minimal surfaces using generative artificial intelligence algorithms
Get PDFTriply periodic minimal surfaces (TPMS) exhibit excellent mechanical and energy absorption properties due to their structural advantages. However, existing porous TPMS structural design methods are constrained to a forward process from structural parameters to mechanical properties. This study proposed an inverse design method that combines bidirectional generative adversarial networks (BiGAN) and mechanical performance targets, resulting in a combined TPMS structure of Primitive and IWP types with superior buffering and energy absorption capabilities. The results show that under a single load value target condition of the designed structure, the minimum deviation index (R2) between the load value corresponding to the displacement point and the target load value is only 0.987, and the maximum mean absolute percentage error (MAPE) is only 5.92 %. When considering the elastic modulus target, the approach successfully conducts two sets of combined structural designs meeting the requirements of both high and low elastic moduli. When targeting the specified load-displacement curve conditions, specifically when combining high elastic modulus with ascending plasticity, the designed structures exhibit an error of only 2.2 % compared to the target property. Moreover, the quasi-static uniaxial compression experiments conducted on additively manufactured designed structures confirm that the experimental curves match the target curves in terms of deformation trends and load value ranges. The success of this inverse design approach for cellular TPMS structures has the potential to expedite new structural material development processes.National Natural Science Foundation of ChinaThe authors wish to gratefully acknowledge the financial support from the National Natural Science Foundation of China (Grant No. 52105418), the Natural Science Foundation of Hunan Province (Grant No. 2023JJ20069 and 2022JJ40600), and the Key Scientific Research Project of Hunan Provincial Department of Education (Grant No. 23A0001).Engineering Structure
Synergetic and performance characteristics of a high-speed pre-cooled propulsion concept
Get PDFPre-cooled air-breathing cycles are promising candidates to power future high-speed flight as well as Single-Stage-To-Orbit vehicles, due to their increased efficiency over contemporary propulsion systems and launch vehicles. These concepts usually feature complex interactions in the synergy of their thermodynamic cycles. In this study, a performance model of such a cycle is developed for its air-breathing mode of operation. One-dimensional thermodynamic modeling is employed within a component-level approach, to evaluate the performance and operation of the cycle under investigation in the range of 1.35 = ≤ 8 = 5 and conditions of up to 26 kilometers altitude. The model is validated quantitatively and qualitatively for both design and off-design conditions. The specific impulse Isp and specific thrust, as predicted by the model, agree within less than 5% for both design and off-design point conditions, while it captures the trend of Isp for the range modeled. Moreover the maximum gross thrust point is predicted correctly at M∞ = 4. The fundamental operating principles and synergetic characteristics of the engine at design and off-design conditions are investigated and reported. A model which does not feature a bypass duct is created and compared for the same inflow conditions and mission profile. It is found that the engine without the bypass duct exhibits reduced specific impulse up to 32% lower at off-design conditions while the overall trend of engine efficiency cannot be properly captured without modeling of the bypass duct, especially at the region of M∞ < 3.5.Journal of Engineering for Gas Turbines and Powe
Phosphorus removal in surface flow treatment wetlands for domestic wastewater treatment: Global experiences, opportunities, and challenges
Get PDFTreatment Wetlands (TWs) are widely used for the treatment of domestic wastewater, with an increasing emphasis on provision of multiple co-benefits. However, concerns remain regarding achieving stringent phosphorus (P) discharge limits, system robustness and resilience, and associated guidance on system design and operation. Typically, where P removal is intended with a passive TW, surface flow (SF) systems are the chosen design type. This study analysed long-term monitoring datasets (2–30 years) from 85 full-scale SF TWs (25 m2 to 487 ha) treating domestic sewage with the influent load ranging from 2.17 to 54,779 m3/d, including secondary treatment, tertiary treatment, and combined sewer overflows treatment. The results showed median percentage removals of total P (TP) and orthophosphate (Ortho P) of 28% and 31%, respectively. Additionally, median areal mass removal rates were 5.13 and 2.87 gP/m2/yr, respectively. For tertiary SF TWs without targeted upstream P removal, 80% of the 44 systems achieved ≤3 mg/L annual average effluent total P. Tertiary SF TWs with targeted upstream P removal demonstrated high robustness, delivering stable effluent TP < 0.35 mg/L. Seasonality in removal achieved was absent from 85% of sites, with 95% of all systems demonstrating stable annual average effluent TP concentrations for up to a 30-year period. Only two out of 32 systems showed a significant increase in effluent TP concentration after the initial year and remained stable thereafter. The impact of different liner types on water infiltration, cost, and carbon footprint were analysed to quantify the impact of these commonly cited barriers to implementation of SF TW for P removal. The use of PVC enclosed between geotextile gave the lowest additional cost and carbon footprint associated with lining SF TWs. Whilst the P-k-C* model is considered the best practice for sizing SF TWs to achieve design pollutant reductions, it should be used with caution with further studies needed to more comprehensively understand the key design parameters and relationships that determine P removal performance in order to reliably predict effluent quality.Department for Environment, Food and Rural AffairsThe authors would like to kindly acknowledge the financial support from 10 UK water utilities (i.e. Anglian Water, Dwr Cymru Welsh Water, Northumbrian Water, Severn Trent, South West Water, Southern Water, Thames Water, United Utilities, Wessex Water, and Yorkshire Water), the Environment Agency, and Irish Water, for funding to conduct this project.Journal of Environmental Managemen
First evidence on the occurrence of multi-mycotoxins and dietary risk exposure to AFB1 along the cassava value chain in Uganda
Get PDFThis study investigated the occurrence and distribution of multiple mycotoxins (aflatoxin B1, B2, G1, G2, fumonisins B1, B2, ochratoxin A (OTA), deoxynivalenol (DON), zearalenone (ZEN), and citrinin (CIT)) in cassava products and as assessed the potential risk of aflatoxin B1 (AFB1) exposure among cassava consumers. A total of 192 samples of cassava products (96 flour and 96 chips, each with 48 samples from farmer and 48 from wholesaler) were analysed using LC/MS–MS. All positive samples irrespective of their origin (flour or chips) exhibited AFB1 levels exceeding the EU regulatory threshold of 5 µg/kg. The sum of fumonisins (FB1 + FB2), ZEN, and DON were significantly (P < 0.05) higher in cassava flour (14.3 µg/kg; 3.71 µg/kg; 25.1 µg/kg) compared to chips (6.54 µg/kg; 1.25 µg/kg; 0.25 µg/kg), respectively. Aflatoxins G2 was not detected in any of 192 samples. Cassava flour samples from farmers exhibited significantly (P < 0.05) higher mean concentrations of AFB1 (27.1 µg/kg), total aflatoxins (78.2 µg/kg), and ochratoxin A (79.6 µg/kg) in contrast to wholesalers, whose mean levels were notably lower at 8.91, 5.79 µg/kg, and 2.44 µg/kg, respectively, pointing the likely critical source of mycotoxin contamination. Cassava consumers in Northern Uganda are at a higher risk, with an estimated 2.06 cancer cases per 100,000 individuals per year compared to those in Eastern Uganda at 0.25. This study underscores the urgent need for interventions to manage aflatoxins in cassava flour, particularly at farm level in Northern Uganda. It accentuates a shift market to household-level sampling and the need for analytical methods targeting multiple mycotoxins.This research was funded by the Commonwealth Scholarship, United Kingdom.Mycotoxin Researc
Work-life balance
No full textThis chapter provides an overview of work-life balance (WLB), concerned with the relationship between an individual’s work and non-work lives. It first introduces and discusses the complexity of work-life balance as a concept and then examines how national, organisational, and temporal contexts may shape how it is understood and enacted. In addition, the chapter critically reviews formal and informal approaches to managing work-life balance for both employees and the organisation. While interest in work-life balance has been widespread and received much attention in academia, institutional and organisational agendas, and public discourse, to date, there has been limited attention given to its meaning and implementation in non-western contexts. This chapter addresses this gap by including a case study in the Chinese context. Using ‘Beyond Management Consulting Ltd’., as a case study, the opportunities for and challenges of managing work-life balance are discussed in the Chinese context. The chapter concludes by emphasising the complexity and dynamic nature of the notion of work-life balance and the necessity of considering inclusivity in how work-life balance is managed.Sociology, Work, and Organisations: A Global Contex