Recent Submissions

  • Machinability of INCONEL718 alloy with a porous microstructure produced by laser melting powder bed fusion at higher energy densities

    Wood, Paul; Díaz-Álvarez, Antonio; Díaz-Álvarez, José; Miguélez, María Henar; Rusinek, Alexis; Williams, Gavin; Bahi, Slim; Sienkiewicz, Judyta; Płatek, Paweł; Gunputh, Urvashi Fowdar; et al. (MDPI, 2020-12-15)
    Products produced by additive manufacturing (AM) seek to exploit net shape manufacturing by eliminating or minimizing post-process stages such as machining. However, many applications which include turbo machinery components with tight dimensional tolerances and a smooth surface finish will require at least a light machine finishing stage. This paper investigates the machinability of the additively fabricated INCONEL718 (IN718) alloy produced by laser melting powder bed fusion (LM-PBF) with different levels of spherical porosity in the microstructure. The literature suggests that the band width for laser energy density, which combines the various scan process parameters to obtain a low spherical type porosity in the LM-PBF IN718 alloy (~1%), has wide breadth. With the increasing laser energy density and above a threshold, there is a rapid increase in the spherical pore size. In this paper, three tube samples each with different levels of spherical porosity were fabricated by varying the laser energy density for LM-PBF of the IN718 alloy within the stable and higher energy density range and the porosity measured. A low laser energy density was avoided due to balling up, which promotes highly irregular lack of fusion defects and poor consolidation within the alloy microstructure. An orthogonal turning test instrumented, with a three-component dynamometer to measure the cutting forces, was performed on AM produced IN718 tube samples under light cut conditions to simulate a finish machining process. The orthogonal turning tests were also performed on a tube sample obtained from the wrought extruded stock. The machining process parameters, which were studied include varying the cutting speed at three levels, at a fixed feed and under dry cut conditions for a short duration to avoid the tool wear. The results obtained were discussed and a notable finding was the higher rate of built-up-edge formation on the tool tip from the AM samples with a higher porosity and especially at a higher cutting speed. The paper also discusses the mechanisms that underpin the findings.
  • The challenges of teaching design in the 21st century, the age of the fourth industrial revolution

    Sole, Martin; Barber, Patrick; Harmanto, Dani; University of Derby (The Design Society - Institution of Engineering Designers, 2020-09-12)
    There is an ever-growing demand from industry for qualified design engineers. Many of these design engineers are trained at universities and colleges. This paper will explore how to keep this training as up to date and relevant as possible. It will look at the modern techniques and methods used by world-leading industries during the 21st century. This century, known also as the Fourth Industrial Revolution, or the Information Technology Revolution. It will show how these techniques and methods can be applied in academia. A challenge is also highlighted, how to get students to design to industry standards but at the same time make it possible to assess their work to satisfy the needs of academia and awarding bodies. These modern techniques and methods will be applied to actual university students and an assessment made of the results. Use of group working will be explored and an algorithm developed to grade the completed group work. What do students need now to equip them to become competent designers, and what will they need soon?
  • Permeability characterization of braided fabrics made of hemp fibers

    Rubino, Felice; Corbin, Anne-Clémence; Ferreira, Manuela; Labbanieh, Ahmad Rashed; Sanguigno, Luigi; Soulat, Damien; Maligno, Angelo; University of Derby; University of Lille, Ensait, Gemtex, F-59000, Roubaix, France (AIP Publishing, 2019-07-02)
    Reinforcement permeability represents crucial parameters in the manufacturing of fiber reinforced composites by liquid composite molding processes (LCM) [1]. Evaluation of fabric permeability is usually challenging and it requires several flow experiments. Indeed, permeability usually presents different values due to the anisotropic nature of textiles and different values have to be evaluated to calculate the permeability tensor. In addition, different flow conditions could establish during the impregnation: macroscopic and microscopic flow through the inter- and intra-tow leading to unevenly wetted regions of the fabric. Finally, differently from synthetic fibers, natural fibers can absorb fluid, acting as a sink, drawing fluid from the main flow and causing swelling of the natural fibers. In this work unsaturated permeability of braided hemp fabrics are studied for different architectures. Two type of braided fabric were investigated: triaxial and biaxial braids. Three distinct values of braiding angle, namely 45°, 50° and 60° were adopted for the biaxial braid to assess the impact of the braiding angle on the reinforcement permeability. The relation between permeability, porosity and fabric architecture was obtained in the case of the Vacuum Assisted Resin Infusion process.
  • Computational study of flow around 2D and 3D tandem bluff bodies

    Charles, Terrance; Yang, Zhiyin; Lu, Yiling; University of Derby (Shahid Chamran University of Ahvaz, 2020-11-21)
    Numerical simulations have been carried out to advance our current understanding of flow around two dimensional (2D) and three dimensional (3D) square shaped tandem bluff bodies at a Reynolds number of 22,000, especially to shed light on the sudden change of the downstream body’s drag coefficient. The Reynolds-Averaged Navier-Stokes (RANS) approach has been employed in the present study and the predicted drag coefficients compare reasonably well with available experimental data. Better understanding of flow fields has been achieved by analyzing streamlines, velocity vectors for both 2D and 3D cases in a horizontal plane and a vertical symmetric plane. The sudden jump in drag coefficient for the 2D case is well captured numerically, which is due to the flow over the upstream body impinging onto the front face of the downstream body at a critical gap size between those two bodies. For the 3D case the drag coefficient is predicted to increase gradually, consistent with the previous experimental finding. This is due to the fact that the vortical structures formed in the 3D case are very different, resulting in a reasonably smooth change of the flow field around the upstream body and hence leading to gradual, not sudden, increase in the drag coefficient of the downstream body.
  • Effective solder for improved thermo-mechanical reliability of solder joints in ball grid array (BGA) soldered on printed circuit board (PCB)

    Depiver, Joshua; Sabuj, Mallik; Amalu, Emeka H; University of Derby; Teeside University (Springer, 2020-11-05)
    Ball grid array (BGA) packages have increasing applications in mobile phones, disk drives, LC displays and automotive engine controllers. However, the thermo-mechanical reliability of the BGA solder joints challenges the device functionality amidst component and system miniaturisation as well as wider adoption of lead-free solders. This investigation determines the effective BGA solders for improved thermo-mechanical reliability of the devices. It utilised a conducted study on creep response of a lead-based eutectic Sn63Pb37 and four lead-free Tin-Silver-Copper (SnAgCu) [SAC305, SAC387, SAC396 and SAC405] solders subjected to thermal cycling loadings and isothermal ageing. The solders form the joints between the BGAs and printed circuit boards (PCBs). ANSYS R19.0 package is used to simulate isothermal ageing of some of the assemblies at -40℃, 25℃, 75℃ and 150℃ temperatures for 45 days and model the thermal cycling history of the other assemblies from 22℃ ambient temperature for six cycles. The response of the solders is simulated using Garofalo-Arrhenius creep model. Under thermal ageing, SAC396 solder joints demonstrate possession of least strain energy density, deformation and von-Mises stress in comparison to the other solders. Under thermal cycle loading conditions, SAC405 acquired the lowest amount of the damage parameters in comparison. Lead-free SAC405 and SAC387 joints accumulated the lowest and highest energy dissipation per cycle, respectively. It is concluded that SAC405 and SAC396 are the most effective solders for BGA in devices experiencing isothermal ageing and temperature cycling during operation, respectively. They are proposed as the suitable replacement of eutectic Sn63Pb37 solder for the various conditions.
  • Comparing and benchmarking fatigue behaviours of various sac solders under thermo-mechanical loading

    Depiver, Joshua Adeniyi; Mallik, Sabuj; Amalu, Emeka H; University of Derby (IEEE, 2020-10-23)
    While the fatigue behaviours (including fatigue life predictions) of lead-free solder joints have been extensively researched in the last 15 years, these are not adequately compared and benchmarked for different lead-free solders that are being used. As more and more fatigue properties of lead-free solders are becoming available, it is also critical to know how fatigue behaviours differ under different mathematical models. This paper addresses the challenges and presents a comparative study of fatigue behaviours of various mainstream lead-free Sn-Ag-Cu (SAC) solders and benchmarked those with lead-based eutectic solder. Creep-induced fatigue and fatigue life of lead-based eutectic Sn63Pb37 and four lead-free SAC solder alloys: SAC305, SAC387, SAC396 and SAC405 are analysed through simulation studies. The Anand model is used to simulate the inelastic deformation behaviour of the solder joints under accelerated thermal cycling (ATC). It unifies the creep and rate-independent plastic behaviour and it is used to predict the complex stress-strain relationship of solders under different temperatures and strain rates, which are required in the prediction of fatigue life using the fatigue life models such as Engelmaier, Coffin-Mason and Solomon as the basis of our comparison. The ATC was carried out using temperature range from −40°C to 150°C. The fatigue damage propagation is determined with finite element (FE) simulation, which allows virtual prototyping in the design process of electronics devices. The simulation was carried out on a BGA (36 balls, 6 × 6 matrix) mounted onto Cu padded substrate. Results are analysed for plastic strain, Von mises stress, strain energy density, and stress-strain hysteresis loop. The simulation results show that the fatigue behaviours of lead-based eutectic Sn63Pb37 solder is comparable to those of lead-free SAC solders. Among the four SAC solders, SAC387 consistently produced higher plastic strain, strain energy and stress than the other solders. The fatigue life’s estimation of the solder joint was investigated using Engelmaier, Coffin-Manson, and Solomon models. Results obtained show that SAC405 has the highest fatigue life (25.7, 21.1 and 19.2 years) followed by SAC396 (18.7, 20.3 and 17.9 years) and SAC305 (15.2, 13.6 and 16.2 years) solder alloys respectively. Predicting the fatigue life of these solder joints averts problems in electronics design for reliability and quality, which if not taken care of, may result in lost revenue. Predictive fatigue analysis can also considerably reduce premature failure, and modern analysis technique such as one used in this research is progressively helping to provide comprehensive product life expectancy data.
  • Nature connectedness, human behaviours, and blue infrastructure: the water effect to people in historical and contemporary masterplanning

    Al-Wali, Wafaa; Tracada, Eleni; University of Derby (Water Efficiency Network, University of Bath, 2020-09)
    Most urban designers and planners have produced anthropocentric masterplans since early twentieth century. Today green infrastructure in cities, including blue infrastructure, primarily expresses people’s relationship to the environment in terms of resource management. Often the natural world is converted into urban green arrangement or a replica of nature mainly for the economic and cultural benefit of humans. Water and related ecosystems were only part of industry as necessity until late twentieth century. Nowadays, water is valued as a very important element of life. Most experts believe that by offering people the opportunity to participate in running and preserving certain ecosystems could have a very positive impact to human health and wellbeing. Environmental psychology suggests that we can provoke heightened experiences in people’s minds by designing dynamic flowing water patterns in urban context. Natural or artificial landscapes, such as green parks should intertwine with the built environment, displaying human creativity and inventiveness. The authors of this paper discuss the importance of water changing culture and behaviours in regenerated green parks in vulnerable urban areas, such as the case study of Arboretum Derby. This particular case study was reviewed by both authors (tutor and PhD student) who shared research with undergraduate students in Urban Design module in this academic year. The student projects reveal the importance of nature connectedness to people seeking happiness and mental balance to counterbalance lockdown hardship, employment loss and social deprivation.
  • Identification of an effective nondestructive technique for bond defect determination in laminate composites—A technical review

    Asif, Muhammad; Khan, Muhammad A; Khan, Sohaib Z; Khan, Kamran A; Choudhry, Rizwan Saeed; National University of Sciences and Technology, Pakistan; Cranfield University; Islamic University of Madinah, Saudi Arabia; University of Derby; Khalifa University of Science and Technology, UAE (SAGE Publications, 2018-03-29)
    Laminate composites are commonly used for the production of critical mechanical structures and components such as wind turbine blades, helicopter rotors, unmanned aerial vehicle wings and honeycomb structures for aircraft wings. During the manufacturing process of these composite structures, zones or areas with weak bond strength are always issues, which may affect the strength and performance of components. The identification and quantification of these zones are always challenging and necessary for the mass production. Non-destructive testing methods available, including ultrasonic A, B, and C-Scan, laser shearography, X-ray tomography, and thermography can be useful for the mentioned purposes. A comparison of these techniques concerning their capacity of identification and quantification of bond defects; however, still needs a comprehensive review. In this paper, a detailed comparison of several non-destructive testing techniques is provided. Emphasis is placed to institute a guideline to select the most suitable technique for the identification of zones with bond defects in laminated composites. Experimental tests on different composite based machined components are also discussed in detail. The discussion provides practical evidence about the effectiveness of different non-destructive testing techniques.
  • Characterization of Sobradinho landslide in fluvial valley using MASW and ERT methods

    Hussain, Yawar; Hamza, Omar; Cárdenas-Soto, Martín; Borges, Welitom Rodrigues; Dou, Jie; Rebolledo, Juan Félix Rodriguez; Prado, Renato Luiz; Clemson University, South Carolina, USA; University of Derby; Universidad Nacional Autónoma de México; et al. (FapUNIFESP (SciELO), 2020-09-30)
    Landslides can substantially impact the fluvial systems, which is why the continuous mapping of their extent, evolution and stability assessment is crucial. However, in such environments, material identification (e.g. colluvium) and subsurface characterization by the methods used for geologic mapping and geotechnical investigation is often a challenging task. Thus, these classical invasive methods may benefit from geophysical techniques to enable and enhance our understanding of the subsurface in these areas. To examine such integrated approach, Multi-Channel Analysis of Surface Waves (MASW) combined with Electrical Resistivity Tomography (ERT) were applied on a geomorphologically active fluvial valley in Sobradinho (the Federal District of Brazil). The subsurface materials showed a specific range of resistivity values as dry soil, saprolite, and landslide slip surface. The 1D shear wave velocity (Vs) model showed an increasing trend of Vs with depth at a location away from the landslide mass, while the longitudinal profile (over the landslide) showed an anomalous change in Vs (~ 250 to 400 m/sec). Based on the existing information about the landslide, the ERT appeared to be an effective method over MASW. This study shows how the integration of geophysical data with the geological and geotechnical investigation helps to obtain a more realistic or unambiguous model of the subsurface.
  • Large eddy simulation of the flow past a circular cylinder at super-critical Reynolds numbers

    Ahmadi, Mohammad; Yang, Zhiyin; University of Derby (ASME, 2020-09)
    Turbulent flow past a circular cylinder at super-critical Reynolds numbers is simulated using large eddy simulation in this study. A novel combination of O- and H-grid structures is used to reduce mesh cells and, in turn, the computational cost. To investigate the influence of sub-grid scale (SGS) models on the accuracy of simulations, four different SGS models are applied to simulate the flow. In this study, the effect of mesh resolution near the wall on the accuracy of results is also evaluated by applying different y+ values at the wall. The results show that due to the complexity of the flow around the cylinder particularly at high Reynolds numbers, using very high resolution mesh near the cylinder wall, can not guarantee the accuracy of results and other parameters such as mesh resolutions at the top and bottom shear layers and the wake shortly behind the cylinder should be considered appropriately.
  • Assessment of drag reduction devices mounted on a simplified tractor-trailer truck model

    Charles, Terrance; Yang, Zhiyin; Lu, Yiling; Coventry University; University of Derby (Shahid Chamran University of Ahvaz, 2020-09-14)
    Aerodynamic drag reduction of tractor-trailer combination trucks is critically important to improve their fuel consumption which consequently results in lower emissions. One practical method to reduce aerodynamic drag of a truck is by mounting drag reduction devices on the truck. This paper presents a numerical study of turbulent flow over a simplified tractortrailer truck with different drag reduction devices mounted on the truck using the Reynolds Averaged Navier-Stokes (RANS) approach to assess the effectiveness of those devices in drag reduction around the tractor-trailer gap region. Three cases with different drag reduction devices have been studied and significant drag reduction (above 30%) has been achieved for all three cases. Detailed analysis of the flow field has been carried out to understand drag reduction mechanisms, and it shows that no matter what drag reduction devices are deployed the drag reduction is mainly due to the reduced pressure on the front face of the trailer, and a small proportion of the drag reduction is due to the reduced turbulent kinetic energy in the gap region.
  • Optimal design of cold roll formed steel channel sections under bending considering both geometry and cold work effects

    Qadir, Sangar; Nguyen, Van Bac; Hajirasouliha, Iman; Cartwright, Brian; English, Martin; University of Derby; University of Sheffield; Hadley Industries plc (Elsevier, 2020-09-17)
    Optimal design of a structural member is a design process of selecting alternative forms to obtain its maximum strength while maintaining the same weight, leading to the most economical and efficient structure. Amongst steel structures, cold rolled steel ones can effectively gain this requirement as they are thin-walled structures that offer the high ratio of strength over weight. However, the design is very challenging as these members are prone to buckling and failure at low loads. In this paper, the buckling and ultimate strength of cold rolled channel sections was studied using numerical modelling. In order to improve the section strength, the development of various alternative cold rolled formed sections included additional bends such as intermediate stiffeners. The section strength was optimised through a practical approach which altered the stiffener’s position and shape and searched for maximum buckling and ultimate strength under bending. In this approach, a nonlinear Finite Element model was first developed for an industrial channel beam subjected to four-point bending tests and this model was validated against experimental test data. The verified model was then used to conduct a parametric study in which the effects of a stiffener’s properties on the section strength including its position, shape, size and material properties by the cold work at bends were investigated in detail. Several different cold rolled channel sections having intermediate stiffeners at web and flanges with and without the cold work effect on material properties at the stiffener’s bends were considered for this investigation. In addition, a design method, the Direct Strength Method (DSM), was utilised to take into account the effects of a stiffener’s properties on the section strength and results were compared with the Finite Element modelling results. It was found that some significant improvements were obtained for the section strength of the optimised sections in comparison to the original sections. An optimal shape for the channel section with maximum ultimate strength in distortional buckling could be obtained with both the stiffeners’ position, shape, size and quantity, and the cold work effect. The cold work effect was found most significant in the cases of changing the width of the web stiffeners and the position of the flange stiffeners. It also revealed that, the currently available DSM beam design curve for distortional buckling provided good agreement in predicting buckling load and ultimate strength capacity for most of the considered sections with and without the cold work effect included; however, the DSM provided overestimate results compared to the Finite Element model results in the sections with web intermediate stiffeners, in particular, when the tip of web intermediate stiffener moved away from the web-flange junction in the horizontal direction.
  • Comprehensive review of the recent advances in PV/T system with loop-pipe configuration and nanofluid

    Cui, Yuanlong; Zhu, Jie; Zoras, Stamatis; Zhang, Jizhe; University of Derby; University of Nottingham; Shandong University (Elsevier, 2020-08-24)
    Solar photovoltaic/thermal technology has been widely utilized in building service area as it generates thermal and electrical energy simultaneously. In order to improve the photovoltaic/thermal system performance, nanofluids are employed as the thermal fluid owing to its high thermal conductivity. This paper summarizes the state-of-the-art of the photovoltaic/thermal systems with different loop-pipe configurations (including heat pipe, vacuum tube, roll-bond, heat exchanger, micro-channel, U-tube, triangular tube and heat mat) and nanoparticles (including Copper-oxide, Aluminium-oxide, Silicon carbide, Tribute, Magnesium-oxide, Cerium-oxide, Tungsten-oxide, Titanium-oxide, Zirconia-oxide, Graphene and Carbon). The influences of the critical parameters like nanoparticle optical and thermal properties, volume fraction, mass flux and mass flow rates, on the photovoltaic/thermal system performance are for the optimum energy efficiency. Furthermore, the structure and manufacturing of solar cells, micro-thermometry analysis of solar cells and recycling process of photovoltaic panels are explored. At the end, the standpoints, recommendations and potential future development on the solar photovoltaic/thermal system with various configurations and nanofluids are deliberated to overcome the barriers and challenges for the practical application. This study demonstrates that the advanced photovoltaic/thermal configuration could improve the system energy efficiency approximately 15%–30% in comparison with the conventional type whereas the nanofluid is able to boost the efficiency around 10%–20% compared to that with traditional working fluid.
  • Computational analysis of turbulent flow over a bluff body with drag reduction devices

    Abikan, Adam; Yang, Zhiyin; Lu, Yiling; University of Derby (University of Ahvaz, 2020-08-23)
    Reducing aerodynamic drag of heavy trucks is crucially important for the reduction of fuel consumption and hence results in less air pollution. One way to reduce the aerodynamic drag is the deployment of drag reduction devices at the rear of trucks and this paper describes a numerical study of flow over a bluff body with rear drag devices using the Reynolds-Averaged-Navier-Stokes (RANS) approach to investigate the drag reduction mechanisms and also to assess accuracy of the RANS approach for this kind of flow. Four cases, a baseline case without any drag reduction devices and three cases with different drag reduction devices, have been studied and the predicted mean and turbulent quantities agree well with the experimental data. Drag reduction varies hugely from a few percent in one case to more than 40% in another case and detailed analysis of flow fields has been carried out to understand such a difference and to elucidate the drag reduction mechanism, which ultimately can lead to better design of future drag reduction devices.
  • Variation in Rayleigh wave ellipticity as a possible indicator of earthflow mobility: a case study of Sobradinho landslide compared with pile load testing

    Hussain, Yawar; Cardenas-Soto, Martin; Moreira, César; Rodriguez-Rebolledo, Juan; Hamza, Omar; Prado, Renato; Martinez-Carvajal, Hernan; Dou, Jie; Clemson University (USA); Universidad Nacional Autónoma de México; et al. (Universidad Nacional de Colombia, 2020-04-01)
    Rainfall-induced landslides pose a significant risk to communities and infrastructures. To improve the prediction of such events, it is imperative to adequately investigate the rainfall-dependent dynamics (leading to fluidization) and any associated internal sliding along shear planes within clayey slopes. Therefore, the present study adopted ambient noise analysis based on the Horizontal to Vertical Spectral Ratio (HVSR) method, to measure the seasonal variation of Rayleigh wave ellipticity as an indicator for the internal deformation and transition in the material state. The methodology was applied to an existing landslide, where variations in soil stiffness and internal sliding were expected to occur in response to rainfall. To improve the interpretation of the HVSR results (and hence the prediction of landslide’ reactivation by rainfall), HVSR measurements were also conducted on a field-scale pile load test. The pile test allowed a comparison of the seismic data generated by the soil movement along shear planes. The HVSR curves of this field test showed two frequency peaks with no changes in the resonance. In comparison with the data obtained from the landslide, the resultant HVSR curves showed three frequency patterns: ubiquitous (2Hz), landslide (4-8Hz), and flat (no peak). However, the HVSR curves did not show any response to the expected seasonally induced variations in the landslide mass because of the relatively short data acquisition. Nevertheless, time-lapse HVSR is a promising technique that can complement other geophysical methods for improving landslide monitoring.
  • Progress in utilisation of waste cooking oil for sustainable biodiesel and biojet fuel production

    Goh, Brandon Han Hoe; Chong, Cheng Tung; Ge, Yu Qi; Ong, Hwai Chyuan; Ng, Jo-Han; Bo, Tian; Ashokkumar, Veeramuthu; Lim, Steven; Seljak, Tine; Józsa, Viktor; et al. (Elsevier, 2020-08-13)
    The increase in human consumption of plant and animal oils has led to the rise in waste cooking oil (WCO) production. Instead of disposing the used cooking oil as waste, recent technological advance has enabled the use of WCO as a sustainable feedstock for biofuels production, thereby maximising the value of biowastes via energy recovery while concomitantly solving the disposal issue. The current regulatory frameworks for WCO collection and recycling practices imposed by major WCO producing countries are reviewed, followed by the overview of the progress in biodiesel conversion techniques, along with novel methods to improve the feasibility for upscaling. The factors which influence the efficiency of the reactions such as properties of feedstock, heterogenous catalytic processes, cost effectiveness and selectivity of reaction product are discussed. Ultrasonic-assisted transesterification is found to be the least energy intensive method for producing biodiesel. The production of bio-jet fuels from WCO, while scarce, provide diversity in waste utilisation if problems such as carbon chain length, requirements of bio-jet fuel properties, extreme reaction conditions and effectiveness of selected catalyst-support system can be solved. Technoeconomic studies revealed that WCO biofuels is financially viable with benefit of mitigating carbon emissions, provided that the price gap between the produced fuel and commercial fuels, sufficient supply of WCO and variation in the oil properties are addressed. This review shows that WCO is a biowaste with high potential for advanced transportation fuel production for ground and aviation industries. The advancement in fuel production technology and relevant policies would accelerate the application of sustainable WCO biofuels.
  • The potential use of geophysical methods to identify cavities, sinkholes and pathways for water infiltration

    Hussain, Yawar; Uagoda, Rogerio; Borges, Welitom; Nunes, José; Hamza, Omar; Condori, Cristobal; Aslam, Khurram; Dou, Jie; Cárdenas-Soto, Martín; Clemson University (USA); et al. (MDPI AG, 2020-08-14)
    The use of geophysical characterization of karst systems can provide an economical and non-invasive alternative for extracting information about cavities, sinkholes, pathways for water infiltration as well as the degree of karstification of underlying carbonate rocks. In the present study, three geophysical techniques, namely, Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Very Low Frequency Electromagnetic (VLFEM) methods were applied at three different locations in relation to fluvial karst, which is listed as an environmentally sensitive area in Rio Vermelho, Mambaí, Goiás, Brazil. In the data acquisition phase, the GPR, direct-current (DC) resistivity and VLFEM profiles were obtained at the three locations in the area. Data were analyzed using commonly adopted processing workflows. The GPR results showed a well-defined lithology of the site based on the amplitude of the signal and radar typologies. On the other hand, the inverted resistivity cross-sections showed a three-layered stratigraphy, pathways of water infiltration and the weathered structures in carbonate (Bambui group). The interpretation of VLFEM as contours of current density resulted from Fraser and Karous–Hjelt filters, indicated the presence of conductive structures (high apparent current density) that might be linked to the weathered carbonate and other conductive and resistive anomalies associated with the water-filled and dry cavities (cave), respectively. The results encourage the integrated application of geophysical techniques such as the reconnaissance for further detailed characterization of the karst areas.
  • A review of in-situ grown nanocomposite coatings for titanium alloy implants

    Gunputh, Urvashi Fowdar; Le, Huirong; Pawlik, Marzena; University of Derby (MDPI AG, 2020-04-21)
    Composite coatings are commonly applied to medical metal implants in order to improve biocompatibility and/or bioactivity. In this context, two types of titanium-based composite coatings have been reviewed as biocompatible and anti-bacterial coatings. The different composites can be synthesised on the surface of titanium using various methods, which have their own advantages and disadvantages. Moving with the smart and nanotechnology, multifunctional nanocomposite coatings have been introduced on implants and scaffolds for tissue engineering with the aim of providing more than one properties when required. In this context, titanium dioxide (TiO2) nanotubes have been shown to enhance the properties of titanium-based implants as part of nanocomposite coatings.
  • Performance comparison of resin-infused thermoplastic and thermoset 3D fabric composites under impact loading

    Choudhry, Rizwan Saeed; Shah, S. Z. H.; Megat-Yusoff, P.S.M.; Karuppanan, S.; Ahmad, F.; Sajid, Z.; Gerard, P.; Sharp, K.; Universiti Teknologi PETRONAS, Malaysia; University of Derby (Elsevier, 2020-07-29)
    In this paper, the impact performance of a novel resin-infused acrylic thermoplastic matrix-based 3D glass fabric composite (3D-FRC) has been evaluated and compared with thermoset based 3D-FRC under single as well as recurring strike low velocity impact (LVI) events. The single impact tests revealed that the thermoplastic-based 3D-FRC exhibits up to 45% reduced damage area and can have up to 20% higher impact load-bearing capacity (peak force). The damage mode characterization showed that damage transition energy required for micro to macro damage transition is 27% higher, and back face damage extension is up to 3 times less for thermoplastic-based 3D-FRC. Meanwhile, the recurring strike impact test highlights that the thermoplastic-based 3D-FRC experiences a 50% less damaged area, better structural integrity, and survived more strikes. The comparison of single and repeated LVI tests have also allowed us to present a design criterion for estimating the safe number of repeated LVI events for a given impact energy. The superior impact resistance of thermoplastic-based 3D-FRC is attributed to their higher interlaminar fracture toughness, a tougher fiber-matrix interface, matrix ductility, and unique failure mechanism of yarn straining, which is not present in thermoset composites.
  • Rutting resistance of asphalt pavement mixes by Finite Element modelling and optimisation

    Phuong Ngo, Chau; Nguyen, Van Bac; Nguyen, Thanh Phong; Bay Pham, Ngoc; Le, Van Phuc; Hung Nguyen, Van; University of Transport and Communications, Campus in Ho Chi Minh City, Vietnam; University of Derby (Bilingual Publishing Co., 2020-01-14)
    Asphalt pavement rutting is a major safety concern and is one of the main distress modes of asphalt pavement. Research into asphalt pavement mixes that provide strong resistance for rutting is considered of great significance as it can help provide extended pavement life and significant cost savings in pavement maintenance and rehabilitation. The objectives of this study are to develop numerical models to investigate the rutting of asphalt concrete pavements and to find optimal design of asphalt pavement mix for rutting resistance. Three-dimensional Finite Element models were first developed to simulate both the axial compression and wheel track testing in which a visco-elastic-plastic material model was used to predict the rutting of the asphalt concrete pavements. A strain hardening creep model with the material parameters developed from experimental testing was employed to model the time-dependent characteristics of the asphalt concrete pavements. The results were validated against the previous experimental wheel track test results of different pavement mixes. Finally, optimisation techniques using the Design Of Experiments method were applied to the simulation rutting results by varying creep parameters to identify their effects on rutting resistance in order to obtain an optimal asphalt pavements mixes. The results of this paper clearly demonstrate an efficient and effective experimental-numerical method and tool set towards optimal design for asphalt concrete pavements for rutting resistance.

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