• An Analysis of Virtual Team Characteristics: A Model for Virtual Project Managers

      Cormican, Kathryn; Morley, Sandra; Folan, Paul; College of Engineering & Informatics, National University of Ireland, Galway. Ireland. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, Devon UK United Kingdom. (Facultad de Economía y Negocios, Universidad Alberto Hurtado, 2015-04)
      An integrated model, created to guide project managers, is outlined for the implementation and management of virtual teams. This model is developed by means of an exploratory literature review and an empirical investigation of virtual team utilization in a multinational medical device manufacturer, which examines several factors critical to their success. A TOWS matrix is used to structure the results of the analysis and to identify future virtual team strategies for the organization. The study demonstrates that a structured approach is essential to ensure that the benefits resulting from virtual teamwork are maximized.
    • An Analytical and Numerical Study of Magnetic Spring Suspension with Energy Recovery Capabilities

      Jia, Yu; Li, Shasha; Shi, Yu; University of Chester; China National Intellectual Property Administration
      As the automotive paradigm shifts towards electric, limited range remains a key challenge. Increasing the battery size adds weight, which yields diminishing returns in range per kilowatt-hour. Therefore, energy recovery systems, such as regenerative braking and photovoltaic cells, are desirable to recharge the onboard batteries in between hub charge cycles. While some reports of regenerative suspension do exist, they all harvest energy in a parasitic manner, and the predicted power output is extremely low, since the majority of the energy is still dissipated to the environment by the suspension. This paper proposes a fundamental suspension redesign using a magnetically-levitated spring mechanism and aims to increase the recoverable energy significantly by directly coupling an electromagnetic transducer as the main damper. Furthermore, the highly nonlinear magnetic restoring force can also potentially enhance rider comfort. Analytical and numerical models have been constructed. Road roughness data from an Australian road were used to numerically simulate a representative environment response. Simulation suggests that 10’s of kW to >100 kW can theoretically be generated by a medium-sized car travelling on a typical paved road (about 2–3 orders of magnitude higher than literature reports on parasitic regenerative suspension schemes), while still maintaining well below the discomfort threshold for passengers (<0.315 m/s2 on average).
    • Cantilevers-on-membrane design for broadband MEMS piezoelectric vibration energy harvesting

      Jia, Yu; Du, Sijun; Seshia, Ashwin A.; University of Chester; University of Cambridge (IOP Publishing, 2015-12-01)
      Most MEMS piezoelectric vibration energy harvesters involve either cantilever-based topologies, doubly-clamped beams or membrane structures. While these traditional designs offer simplicity, their frequency response for broadband excitation are typically inadequate. This paper presents a new integrated cantilever-on-membrane design that attempts to both optimise the strain distribution on a piezoelectric membrane resonator and improve the power responsiveness of the harvester for broadband excitation. While a classic membrane-based resonator has the potential to theoretically offer wider operational frequency bandwidth than its cantilever counterpart, the addition of a centred proof mass neutralises its otherwise high strain energy regions. The proposed topology addresses this issue by relocating the proof mass onto subsidiary cantilevers and integrates the merits of both the membrane and the cantilever designs. When experimentally subjected to a band-limited white noise excitation, up to approximately two folds of power enhancement was observed for the new membrane harvester compared to a classic plain membrane device.
    • A Compensation Method for Active Phased Array Antennas : Using a Strain-Electromagnetic Coupling Model

      Shi, Yu; Wang, Congsi; Wang, Yan; Yuan, Shuai; Duan, Baoyan; Lian, Peiyuan; Xue, Song; Du, Biao; Gao, Wei; Wang, Zhihai; et al.
      Physical deformation due to service loads seriously degrades the electromagnetic performance of active phased array antennas. However, traditional displacement-based compensation methods are moderately difficult to use because displacement measurements generally require stable references, which are hard to realize for antennas in service. For deformed antennas, strain information is directly related to their displacement, and strain sensors can overcome carrier platform constraints to measure real-time strain without affecting the antenna radiation-field distribution. We thus present a compensation method based on strain information for in-service antennas. First, the minimum number of strain sensors is determined as the main modal-order-based modal effective mass fraction. According to the modal method and analysis of spatial phase-distribution errors related to strain, a coupled strain-electromagnetic model is established to evaluate antenna performance from the measured strain. The corresponding excitation phase from the measured strain is adjusted to compensate antenna performance. Finally, the method is experimentally validated using an X-band active phased array antenna under the influence of typical deformation conditions for both boresightand scanned beams. The results demonstrate that the presented method can effectively compensate for the performance of service antennas directly from the measured strain information.
    • Connection Configurations to Increase Operational Range and Output Power of Piezoelectric MEMS Vibration Energy Harvesters

      Du, Sijun; Chen, Shao-Tuan; Jia, Yu; Arroyo, Emmanuelle; Seshia, Ashwin A.; University of Cambridge; University of Chester (IOP Publishing, 2016-09-06)
      Among the various methods of extracting energy harvested by a piezoelectric vibration energy harvester, full-bridge rectifiers (FBR) are widely employed due to its simplicity and stability. However, its efficiency and operational range are limited due to a threshold voltage that the open-circuit voltage generated from the piezoelectric transducer (PT) must attain prior to any energy extraction. This voltage linearly depends on the output voltage of the FBR and the forward voltage drop of diodes and the nature of the interface can significantly limit the amount of extracted energy under low excitation levels. In this paper, a passive scheme is proposed to split the electrode of a micromachined PT into multiple (n) equal regions, which are electrically connected in series. The power output from such a series connected MEMS PT allows for the generated voltage to readily overcome the threshold set by the FBR. Theoretical calculations have been performed in this paper to assess the performance for different series stages (n values) and the theory has been experimentally validated. The results show that a PT with more series stages (high n values) improves the efficiency of energy extraction relative to the case with fewer series-connected stages under weak excitation levels.
    • Delamination Detection via Reconstructed Frequency Response Function of Composite Structures

      Shi, Yu; Alsaadi, Ahmed; Jia, Yu; University of Chester
      Online damage detection technologies could reduce the weight of structures by allowing the use of less conservative margins of safety. They are also associated with high economical benefits by implementing a condition-based maintenance system. This paper presented a damage detection and location technique based on the dynamic response of glass fibre composite laminate structures (frequency response function). Glass fibre composite laminate plates of 200×200×2.64 mm, which had a predefined delamination, were excited using stationary random vibration waves of 500 Hz band-limited noise input at ≈1.5 g. The response of the structure was captured via Micro-ElectroMechanical System (MEMS) accelerometer to detect damage. The frequency response function requires data from damaged structures only, assuming that healthy structures are homogeneous and smooth. The frequency response of the composite structure was then reconstructed and fitted using the least-squares rational function method. Delamination as small as 20 mm was detected using global changes in the natural frequencies of the structure, the delamination was also located with greater degree of accuracy due to local changes of frequency response of the structure. It was concluded that environmental vibration waves (stationary random vibration waves) can be utilised to monitor damage and health of composite structures effectively.
    • Development of laser peening ceramics

      Shukla, Pratik; Lawrence, Jonathan; Waugh, David G.; University of Chester (2015-03)
    • The diagnostic analysis of the fault coupling effects in planet bearing

      Xue, Song; Wang, Congsi; Howard, Ian; Lian, Peiyuan; Chen, Gaige; Wang, yan; Yan, Yuefei; Xu, Qian; Shi, Yu; Jia, Yu; et al.
      The purpose of this paper is to investigate the fault coupling effects in the planet bearing as well as the corresponding vibration signatures in the resultant vibration spectrum. In a planetary gear application, the planet bearing can not only spin around the planet gear axis, but also revolve about the sun gear axis and this rotating mechanism poses a big challenge for the diagnostic analysis of the planet bearing vibration spectrum. In addition, the frequency component interaction and overlap phenomenon in the vibration spectrum caused by the fault coupling effect can even worsen the diagnosis results. To further the understanding of the fault coupling effects in a planet bearing, a 34° of freedom planetary gear model with detailed planet bearing model was established to obtain the dynamic response in the presence of various bearing fault scenarios. The method of modelling the bearing distributed faults and localized faults has been introduced in this paper, which can be further incorporated into the planetary gear model to obtain the faulted vibration signal. The “benchmark” method has been adopted to enhance the planet bearing fault impulses in the vibration signals and in total, the amplitude demodulation results from 20 planet bearing fault scenarios have been investigated and analyzed. The coherence estimation over the vibration frequency domain has been proposed as a tool to quantify the fault impact contribution from different fault modes and the results suggested that the outer raceway fault contributes most to the resultant planet bearing vibration spectrum in all the investigated fault scenarios.
    • Effect of laser treatment on the attachment and viability of mesenchymal stem cell responses on shape memory NiTi alloy

      Chan, Chi-Wai; Hussain, Issam; Waugh, David G.; Lawrence, Jonathan; Man, Hau-Chung; Queen's University, Belfast ; University of Lincoln ; University of Chester ; University of Chester ; Hong Kong Polytechnic University (Elsevier, 2014-05-22)
      The objectives of this study were to investigate the effect of laser-induced surface features on the morphology, attachment and viability of mesenchymal stem cells (MSCs) at different periods of time, and to evaluate the biocompatibility of different zones: laser-melted zone (MZ), heat-affected zone (HAZ) and base metal (BM) in laser-treated NiTi alloy.
    • Effect of surface micro-pits on mode-II fracture toughness of Ti-6Al-4V/PEEK interface

      Pan, Lei; Pang, Xiaofei; Wang, Fei; Huang, Haiqiang; Shi, Yu; Tao, Jie; Nanjing University of Aeronautics and Astronautics; University of Chester
      Herein, the delamination issue of TiGr(TC4/PEEK/Cf) laminate is addressed by investigating the influence of TC4(Ti-6Al-4V) surface micro-pits on mode-II interfacial fracture toughness of TC4/PEEK interface through experimental and finite element modeling. The micro-pits unit cell, unit strip and the end notched flexure (ENF) models are established based on the finite element simulations and the effect of micro-pit size parameters is studied in detail. The results of micro-pits unit cell model reveal that the presence of micro-pits can effectively buffer the interfacial stress concentration under mode-II loading conditions. Furthermore, the micro-pits unit strip model, with different micro-pit sizes, is analyzed to obtain the interface parameters, which are converted and used in the ENF model. Both the unit strip and ENF models conclude that the presence of interfacial micro-pits effectively improves the mode-II fracture toughness. It is worth mentioning that the utilization of converted interface parameters in ENF model avoided the limitation of micro-pit size and reduced the workload. Finally, the experimental and computational ENF results exhibited excellent consistency and confirmed the reliability of the proposed finite element models. The current study provides useful guidelines for the design and manufacturing of high-performance TC4/PEEK interfaces for a wide range of applications.
    • An Efficient Inductor-less Dynamically Configured Interface Circuit for Piezoelectric Vibration Energy Harvesting

      Du, Sijun; Jia, Yu; Seshia, Ashwin A.; University of Cambridge; University of Chester (Institute of Electrical and Electronics Engineers, 2016-07-07)
      Vibration energy harvesting based on piezoelectric materials is of interest in several applications such as in powering remote distributed wireless sensor nodes for structural health monitoring. Synchronized Switch Harvesting on Inductor (SSHI) and Synchronous Electric Charge Extraction (SECE) circuits show good power efficiency among reported power management circuits; however, limitations exist due to inductors employed, adaption of response to varying excitation levels and the Synchronized Switch Damping (SSD) effect. In this paper, an inductor-less dynamically configured interface circuit is proposed, which is able to configure the connection of two piezoelectric materials in parallel or in series by periodically evaluating the ambient excitation level. The proposed circuit is designed and fabricated in a 0:35 μm HV CMOS process.The fabricated circuit is co-integrated with a piezoelectric bimorph energy harvester and the performance is experimentally validated. With a low power consumption (0:5 μW), the measured results show that the proposed rectifier can provide a 4.5 boost in harvested energy compared to the conventional full-bridge rectifier without employing an inductor. It also shows a high power efficiency over a wide range of excitation levels and is less susceptible to SSD.
    • An Efficient SSHI Interface With Increased Input Range for Piezoelectric Energy Harvesting Under Variable Conditions

      Du, Sijun; Jia, Yu; Do, Cuong D.; Seshia, Ashwin A.; University of Cambridge; University of Chester (IEEE, 2016-08-10)
      Piezoelectric vibration energy harvesters have been widely researched and are increasingly employed for powering wireless sensor nodes. The synchronized switch harvesting on inductor (SSHI) circuit is one of the most efficient interfaces for piezoelectric vibration energy harvesters. However, the traditional incarnation of this circuit suffers from a significant start-up issue that limits operation in low and variable amplitude vibration environments. This paper addresses this start-up issue for the SSHI rectifier by proposing a new architecture with SSHI startup circuitry. The startup circuitry monitors if the SSHI circuit is operating correctly and re-starts the SSHI interface if required. The proposed circuit is comprehensively analyzed and experimentally validated through tests conducted by integrating a commercial piezoelectric vibration energy harvester with the new interface circuit designed in a 0.35-μm HV CMOS process. Compared to conventional SSHI rectifiers, the proposed circuit significantly decreases the required minimum input excitation amplitude before energy can be harvested, making it possible to extract energy over an increased excitation range.
    • Eight parametric resonances in a multi-frequency wideband MEMS piezoelectric vibration energy harvester

      Jia, Yu; Du, Sijun; Seshia, Ashwin A.; University of Cambridge; University of Chester (IEEE, 2016-01-24)
      This paper presents a multi-order parametric resonant MEMS piezoelectric disk membrane, for the purpose of broadening the operational frequency bandwidth of a vibration energy harvester by employing the nonlinearity-induced bandwidth broadening associated with this phenomenon as well as the multi-frequency response associated with the higher orders. The fundamental mode -3dB bandwidth at 2.0 g recorded 55 Hz, while the first parametric resonant peak exhibited 365 Hz and the -3dB of the first 8 orders accumulated to 604 Hz. The membrane parametric resonator also experimentally demonstrated over 3-folds improvement in power density compared to a conventional direct resonator (cantilever), when subjected to band-limited white noise.
    • Energy Harvesting behaviour for Aircraft Composites Structures using Macro-Fibre Composite: Part I–Integration and Experiment

      Shi, Yu; Zhu, Meiling; Hallett, Stephen R; University of Chester; University of Exeter; University of Bristol
      This paper investigates new ways to integrate piezoelectric energy harvesting elements onto carbon-fibre composite structures, using a new bonding technique with a vacuum bag system and co-curing process, for fabrication onto airframe structures. Dynamic mechanical vibration tests were performed to characterise the energy harvested by the various integration methods across a range of different vibration frequencies and applied mechanical input loadings. An analytical model was also introduced to predict the power harvested under the mechanical vibrations as a benchmark to evaluate the proposed methods. The developed co-curing showed a high efficiency for energy harvesting at a range of low frequencies, where the co-curing method offered a maximum improvement of 14.3% compared to the mechanical bonding approach at a frequency of 10 Hz. Furthermore, co-curing exhibited potential at high frequency by performing the sweep test between frequencies of 1 and 100 Hz. Therefore, this research work offers potential integration technology for energy harvesting in complicated airframe structures in aerospace applications, to obtain the power required for environmental or structural health monitoring.
    • Enhancement in Interfacial Adhesion of Ti/Polyetheretherketone by Electrophoretic Deposition of Graphene Oxide

      Pan, Lei; Lv, Yunfei; Nipon, Roy; Wang, Yifan; Duan, Lixiang; Hu, Jingling; Ding, Wenye; Ma, Wenliang; Tao, Jie; Shi, Yu; et al.
      This article discusses about the significance of graphene oxide (GO) deposition on the surface of a titanium plate by electrophoretic deposition (EPD) method to improve the adhesive strength of Ti/polyetheretherketone (PEEK) interfacial adhesive. Firstly, the anodic EPD method was applied to a water dispersion solution of GO, and then the morphology and the properties of titanium plate surface were characterized by scanning electron microscopy and contact angle measurements before and after GO deposition. Furthermore, the changes in the properties of GO after heating at 390°C were characterized by Raman and Fourier transform infrared spectroscopies. According to the results of single lap tensile shear test, the adhesion strength of Ti/PEEK interface after the anodization and deposition of GO was 34.94 MPa, an increase of 29.2% compared with 27.04 MPa of sample with only anodization. Also, the adhesion strengths were 58.1 and 76.5% higher compared with the samples of only GO deposited (22.1 MPa) and pure titanium (19.8 MPa), respectively.
    • Enhancing interfacial strength between AA5083 and cryogenic adhesive via anodic oxidation and silanization

      Lei, Pan; Zhang, Aiai; Zheng, Zengmin; Duan, Lixiang; Zhang, Lei; Shi, Yu; Tao, Jie; Nanjing University of Aeronautics and Astronautics; University of Chester
      AA5083 aluminum alloy was treated in turn with phosphoric-sulfuric acid anodic oxidation and then with silanization using the silane coupling agent KH560. A chemical bond (Si-O-Al) was created between the aluminum alloy and silane film, and a dehydration condensation reaction occurred between the silane film and cryogenic adhesive to enhance the bonding strength between the aluminum alloy and the cryogenic adhesive. Scanning electron microscopy, Energy dispersive spectroscopy, and Fourier transform infrared spectroscopy were used to explore the interfacial characteristics of the aluminum alloy both with and without the applied treatment. Furthermore, single lap shear tests and durability tests were performed to assess the adhesive strength of the interface between the aluminum alloy and the cryogenic adhesive at low temperature. The most improved interfacial strength using the anodic oxidation and the silanization treatments reached 33.96 MPa at −60 °C. The interface strength with the same treatments after the durability test was 25.4 MPa.
    • Evaporation of liquid nitrogen droplets in superheated immiscible liquids

      Rebelo, Neville; Zhao, Huayong; Nadal, Francois; Garner, Colin; Williams, Andy; Loughborough University; University of Chester (Elsevier, 2019-08-22)
      Liquid nitrogen or other cryogenic liquids have the potential to replace or augment current energy sources in cooling and power applications. This can be done by the rapid evaporation and expansion processes that occur when liquid nitrogen is injected into hotter fluids in mechanical expander systems. In this study, the evaporation process of single liquid nitrogen droplets when submerged into n-propanol, methanol, n-hexane, and n-pentane maintained at 294 K has been investigated experimentally and numerically. The evaporation process is quantified by tracking the growth rate of the resulting nitrogen vapour bubble that has an interface with the bulk liquid. The experimental data suggest that the bubble volume growth is proportional to the time and the bubble growth rate is mainly determined by the initial droplet size. A comparison between the four different bulk liquids indicates that the evaporation rate in n-pentane is the highest, possibly due to its low surface tension. A scaling law based on the pure diffusion-controlled evaporation of droplet in open air environment has been successfully implemented to scale the experimental data. The deviation between the scaling law predictions and the experimental data for 2-propanol, methanol and n-hexane vary between 4% and 30% and the deviation for n-pentane was between 24% and 65%. The more detailed bubble growth rates have been modelled by a heuristic one-dimensional, spherically symmetric quasi-steady-state confined model, which can predict the growth trend well but consistently underestimate the growth rate. A fixed effective thermal conductivity is then introduced to account for the complex dynamics of the droplet inside the bubble and the subsequent convective processes in the surrounding vapour, which leads to a satisfactory quantitative prediction of the growth rate.
    • Evidence for the Perception of Time Distortion During Episodes of Alice in Wonderland Syndrome

      Jia, Yu; Miao. Ying; University of Chester; Aston University (Lippincott Williams & Wilkins, 2018-05-17)
      Alice in Wonderland syndrome (AIWS) is a rare perceptual disorder associated with sensation of one or several visual and/or auditory perceptual distortions including size of body parts, size of external objects, or passage of time (either speeding up or slowing down). Cause for AIWS is yet to be widely agreed, and the implications are widely varied. One of the research difficulties is the brevity of each episode, typically not exceeding few tens of minutes. This article presents a male adult in late 20s who has apparently experienced AIWS episodes since childhood, and infection has been ruled out. Reaction speed tests were conducted during and after AIWS episodes, across a span of 13 months. Statistically significant evidence is present for delayed response time during AIWS episodes when the patient claims to experience a sensation of time distortion: where events seem to move faster and people appear to speak quicker.
    • Experimental and theoretical study of a piezoelectric vibration energy harvester under high temperature

      Arroyo, Emmanuelle; Jia, Yu; Du, Sijun; Chen, Shao-Tuan; Seshia, Ashwin A.; University of Cambridge; University of Chester (IEEE, 2017-08-01)
      This paper focuses on studying the effect of increasing the ambient temperature up to 160 °C on the power harvested by an MEMS piezoelectric micro-cantilever manufactured using an aluminum nitride-on-silicon fabrication process. An experimental study shows that the peak output power decreases by 60% to 70% depending on the input acceleration. A theoretical study establishes the relationship of all important parameters with temperature and includes them into a temperature-dependent model. This model shows that around 50% of the power drop can be explained by a decreasing quality factor, and that thermal stresses account for around 30% of this decrease.
    • A finite element analysis of impact damage in composite laminates

      Shi, Yu; Soutis, Constantinos; University of Chester; University of Manchester (Cambridge University Press, 2012-12-01)
      In this work, stress-based and fracture mechanics criteria were developed to predict initiation and evolution, respectively, of intra- and inter-laminar cracking developed in composite laminates subjected to low velocity impact. The Soutis shear stress-strain semi-empirical model was used to describe the nonlinear shear behaviour of the composite. The damage model was implemented in the finite element (FE) code (Abaqus/Explicit) by a user-defined material subroutine (VUMAT). Delamination (or inter-laminar cracking) was modelled using interface cohesive elements and the splitting and transverse matrix cracks that appeared within individual plies were also simulated by inserting cohesive elements between neighbouring elements parallel to the fibre direction in each single layer. A good agreement was obtained when compared the numerically predicted results to experimentally obtained curves of impact force and absorbed energy versus time. A non-destructive technique (NDT), penetrant enhanced X-ray radiography, was used to observe the various damage mechanisms induced by impact. It has been shown that the proposed damage model can successfully capture the internal damage pattern and the extent to which it was developed in these carbon fibre/epoxy composite laminates.