Mechanical Engineering (Scholarly Articles)

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  • Publication
    Efficiency and accuracy of GPU-parallelized Fourier spectral methods for solving phase-field models
    (Elsevier, 2023-06-15) Boccardo, Adrian; Tong, Mingming; Leen, Sean B.; Tourret, Damien; Segurado, Javier; Science Foundation Ireland; Spanish Ministry of Science; Horizon 2020
    Phase-field models are widely employed to simulate microstructure evolution during processes such as solidification or heat treatment. The resulting partial differential equations, often strongly coupled together, may be solved by a broad range of numerical methods, but this often results in a high computational cost, which calls for advanced numerical methods to accelerate their resolution. Here, we quantitatively test the efficiency and accuracy of semi-implicit Fourier spectral-based methods, implemented in Python programming language and parallelized on a graphics processing unit (GPU), for solving a phase-field model coupling Cahn–Hilliard and Allen–Cahn equations. We compare computational performance and accuracy with a standard explicit finite difference (FD) implementation with similar GPU parallelization on the same hardware. For a similar spatial discretization, the semi-implicit Fourier spectral (FS) solvers outperform the FD resolution as soon as the time step can be taken 5 to 6 times higher than afforded for the stability of the FD scheme. The accuracy of the FS methods also remains excellent even for coarse grids, while that of FD deteriorates significantly. Therefore, for an equivalent level of accuracy, semi-implicit FS methods severely outperform explicit FD, by up to 4 orders of magnitude, as they allow much coarser spatial and temporal discretization.
  • Publication
    Experimental characterization and strengthening mechanism of process-structure-property of selective laser melted 316 L
    (Elsevier, 2023-03-02) Chen, Yefeng; Wang, Xiaowei; Li, Dong; Zhou, Dewen; Jiang, Yong; Yang, Xinyu; Liu, Chenglu; Leen, Sean B.; Gong, Jianming; Science Foundation Ireland
    Heat treatment is the most common method to relieve residual stress and to adjust tensile properties in additively manufactured material. However, the well-known strengthening factors (e.g., dislocation density, cellular sub-structure, low angle grain boundaries, nano-oxide particle) in selective laser melted 316 L (SLM 316 L) are strongly influenced by heat-treatment temperature. In this work, horizontal and vertical oriented SLM 316 L specimens are heat treated from 550 °C to 1150 °C, followed by tensile tests and microstructural characterization. With increasing temperature, strength (e.g., yield strength, ultimate tensile strength) is found to decrease and elongation is found to increase. The heat treatments of 550 °C, 650 °C and 750 °C lead to coarsening of cellular sub-structure. Furthermore, the cellular sub-structure and melt boundaries annihilate at 950 °C. When the temperature reaches 1150 °C, SLM 316 L has finished recrystallization with volume fraction of nano-oxide particles increasing greatly. Based on microstructural characterization, the proposed relationship, considering strengthening mechanisms of cellular sub-structure, nano-oxide particle and grain boundaries, give satisfactory accuracy to predict yield strength for horizontal orientation. The yield strength for vertical orientation can also be predicted by this relationship when modified by consideration of anisotropy of columnar grains and lack-of-fusion defects. The anisotropy and lack-of-fusion lead to 5.4% reduction in yield strength for the vertical orientation. This work establishes quantitative relationships for heat treatment-microstructure-property, in which the anisotropy of tensile properties is considered.
  • Publication
    Process-structure-property modeling for postbuild heat treatment of powder bed fusion Ti-6Al-4V
    (SAGE Publications, 2023-07-10) Liu, Jianxin; Yang, Xinyu; Chai, Xingzai; Boccardo, Adrian; Chen, Yefeng; Wang, Xiaowei; Leen, Sean B.; Gong, Jianming; Science Foundation Ireland
    Postbuild heat treatment is an important component in optimized manufacturing processing for laser beam powder bed fusion (PBF-LB) Ti-6Al-4V. The development of predictive modeling, based on the understanding of the relationships between process parameters, microstructure evolution, and mechanical properties, is a potentially key ingredient in this optimization process. In this paper, a process-structure-property (PSP) model is developed to predict the effect of postbuild heat treatment on yield strength, which is a key tensile property for PBF-LB Ti-6Al-4V. The process-structure part is developed with a focus on the prediction of solid-state phase transformation, especially dissolution of martensite during the heating phase. Subsequent tensile properties are quantified by a microstructure-sensitive yield strength model based on the predicted microstructure variables. The integrated PSP model is validated via experimentally measured phase fraction, α lath width and monotonic tensile tests on PBF-LB Ti-6Al-4V with different heat treatment temperatures, for identification of optimal process parameters.
  • Publication
    Three-dimensional finite element modelling for additive manufacturing of Ti-6Al-4V components: Effect of scanning strategies on temperature history and residual stress
    (Elsevier, 2022-03-22) Zhou, Jinbiao; Barrett, Richard A.; Leen, Sean B.; Science Foundation Ireland
    A key challenge for metal additive manufacturing is the requirement to adapt process-structure-property methods currently under development to realistic, complex geometries. Of specific concern in the present work is the requirement for accurate computation in such realistic geometries of (i) thermal histories, to facilitate microstructure prediction, and hence, mechanical properties, and (ii) residual stresses, as required for accurate assessment and design for structural integrity, such as fatigue cracking. This paper presents three-dimensional, finite element modelling for simulation of a realistic Ti-6Al-4V component using directed energy deposition. The predicted results are successfully validated against published experimental and numerical data. The effects of different scanning strategies on temperature histories and residual stresses are investigated as a basis for identification of optimal manufacturing protocols. Finally, fatigue life predictions of the Ti-6Al-4V component have been considered based on the Basquin-Goodman equation with the effect of residual stress taken into account.
  • Publication
    Finite element modelling for mitigation of residual stress and distortion in macro-scale powder bed fusion components
    (SAGE Publications, 2022-12-23) Zhou, Jinbiao; Barrett, Richard A.; Leen, Sean B.; Science Foundation Ireland
    Powder bed fusion (PBF) has attracted significant attention in many applications due to its capability of fabricating complex and customized metal parts. However, the potential for high inherent residual stresses that produce distortion in additive manufacturing (AM) components prevents more widespread application of the AM technique. Efficient and accurate prediction of residual stress and distortion at component-level (macro-scale) is a complex task. Although process-level (meso-scale) thermo-mechanical simulations have resulted in accurate predictions for small-scale parts, the computational times (typically weeks) and memory requirements for application of such methods to component-level are prohibitive. The main goal of the current study therefore is to present an efficient and accurate finite element (FE) simulation method with detailed validation for PBF manufacture of a complex 3D Inconel 625 benchmark bridge component (macro-scale). The simulation results are successfully validated against the published benchmark experimental measurements from neutron diffraction, X-ray diffraction (XRD), contour method and coordinate measurement machine (CMM) by the National Institute of Standards and Technology (NIST) laboratory. A key additional novelty of the present work is the investigation of the effects of substrate removal and preheating on mitigation of residual stresses and distortions using the validated model. Ultimately, these results will guide the selection of optimal manufacturing protocols and integration of the FE-based AM modelling for industrial application with complex geometries. The ultimate aim of the present work is to facilitate fatigue life prediction of complex geometry AM components including residual stress effects, for example, conformally-cooled injection moulding dies (for different material than Inconel 625).
  • Publication
    Strategies for mainstreaming education for sustainable development in education systems
    (Index Copernicus, 2022-06-30) Thakore, Renuka; Nkuba, Michael; Mitchell, Sinéad; Kelkar, Ashish
    A meaningful and relevant ¿Excellence in Education Spaces¿ is imperative so that future generations can address societal risks. This inevitably requires education to integrate strategies to transform the current approaches and build on sustainability strategies. Education for sustainable development (ESD), considered a pivotal vehicle, is, nevertheless, relegated to science and environmental-related courses at most schools and universities. ESD is treated as one off-topic for discussion, creating an information deficit, implying that a few future leaders get knowledge about sustainability. The practices and attitudes about sustainable development goals (SDGs) are not universal, failing to achieve equitable SDGs. A few purposive studies from engineering were analysed to confirm that the ESD must be mainstreamed in education, allowing future generation delegates to build knowledge capital at the individual and institutional levels, equip future practitioners and decision-makers with strategic capabilities to resolve unforeseeable problems, drive societal transformation, and impact climate change, honouring SDGs
  • Publication
    Portfolio management: The holistic data lifecycle
    (Drake Management Review, 2022-10) McAvoy, John; Murphy, Conor; Mushtaq, Laila; O’Donnell, James; Brennan, Attracta; Dempsey, Mary; Kiely, Gaye
    Machine learning provides many benefits to Portfolio Managers in analysing data and has the potential to provide much more. A concern with the approach to Machine Learning in Portfolio Management is that is caught between two domains: finance and information systems. In reality, to ensure its success, having these two separate and distinct domains are problematic. What is required is a holistic view, facilitating discussions, with data being the unifying concept and the one that is key to success. The data value map is a lens that allows all involved, in the use or adoption of Machine Learning in Portfolio Management, to form a shared understanding of the lifecycle of the data involved. Rather than being seen as a financial concept or a technical concept, this view of the data lifecycle provides a platform for all involved to determine what is required, and to identify and deal with any potential pitfalls along the way. A holistic view, and shared understanding, are required for the success of Machine Learning in Portfolio Management. Research on the intersection between Machine Learning and Portfolio Management is currently lacking. A focus on the different parts of the data lifecycle provides an opportunity for further research.
  • Publication
    On the corrosion cracking of austenitic stainless steel in molten solar salt: experiments and modelling
    (Elsevier, 2022-09-16) Li, Heng; Wang, Xiaowei; Feng, Xiucheng; Yang, Xinyu; Tang, Jianqun; Gong, Jianming; Leen, Sean B.; National Natural Science Foundation of China
    The mechanical behaviors of 304 and 316 L steels was investigated in air and in solar salt with different contents of chloride impurity under slow strain rate tensile (SSRT) tests using a novel experimental approach at 565 °C. Results show that the yield strength (YS) and ultimate tensile strength (UTS) are negligibly affected by the molten salt corrosion whereas the ductility decreases with increasing contents of chloride. Corrosion cracks initiate and propagate along the grain boundary due to its higher corrosion rate and incremental oxide rupture. Moreover, a damage model that captures the corrosion and chloride effects is proposed and validated.
  • Publication
    A review of the most significant challenges impacting conventional Project Management success
    (Institute of Electrical and Electronics Engineers, 2022-06-29) Dempsey, Mary; Brennan, Attracta; Holzberger, Astrid; McAvoy, John
    To remain competitive, it is important for organizations to be aware of the success factors for effective conventional project management. It is equally important for them to develop knowledge about project management challenges and how such challenges can be addressed. Organizations and their project management teams are influenced by the three categories of enablers, limitations and challenges. In this study, a review was carried out to highlight the challenges impacting the effectiveness of conventional project management. The review process comprised; identifying the research question; identifying relevant references; selecting studies; charting the data; and collating, summarizing, and reporting results. This process resulted in the inclusion of eight relevant references. Based on the frequency of challenge occurrence, the following five significant challenges have been identified; communication, control, competence, culture, and complexity. Complementarity and dependency links between these five challenges have been highlighted in this paper. In this review paper, some project management challenges may not be presented. Due to the selected databases, search terms, chosen publications, and the authors¿ assessment, the research may have some limitations. Furthermore, the challenges of conventional project management can partly be overcome by a mixture of other project management methods and identified recommendations.
  • Publication
    Defect evaluation of the honeycomb structures formed during the drilling process
    (SAGE Publications, 2019-07-02) Ghabezi, Pouyan; Farahani, M.; Shahmirzaloo, Ali; Ghorbani, H.; Harrison, Noel M.
    In this paper, a comprehensive experimental investigation was carried out to precisely characterize the delamination and uncut fiber in the drilling process. A digital imaging procedure was developed in order to calculate the damage resulted from the drilling process. A novel method is proposed in this article based on image intensity to verify the obtained results. A full factorial experimental design was performed to evaluate the importance of the drilling parameters. Among other process parameters, feed rate, cutting speed, and tool diameter are the principal factors responsible for the delamination damage size during the drilling. The drilling process was assessed based on two proposed incurred damage factors, specifically the delamination factor and uncut fiber factor. Experimental results demonstrated that the feed rate was the paramount parameter for both delamination and uncut fiber factors. It was observed that both factors increased with an increase in the feed rate. Additionally, by increasing the tool diameter, the delamination and uncut fiber factors significantly increase. The effects of the cutting speed on damage factors were not linear. The minimum delamination factor and uncut fiber factor were obtained at the cutting speed of 1500 and 2500â r/min, respectively.In this paper, a comprehensive experimental investigation was carried out to precisely characterize the delamination and uncut fiber in the drilling process. A digital imaging procedure was developed in order to calculate the damage resulted from the drilling process. A novel method is proposed in this article based on image intensity to verify the obtained results. A full factorial experimental design was performed to evaluate the importance of the drilling parameters. Among other process parameters, feed rate, cutting speed, and tool diameter are the principal factors responsible for the delamination damage size during the drilling. The drilling process was assessed based on two proposed incurred damage factors, specifically the delamination factor and uncut fiber factor. Experimental results demonstrated that the feed rate was the paramount parameter for both delamination and uncut fiber factors. It was observed that both factors increased with an increase in the feed rate. Additionally, by increasing the tool diameter, the delamination and uncut fiber factors significantly increase. The effects of the cutting speed on damage factors were not linear. The minimum delamination factor and uncut fiber factor were obtained at the cutting speed of 1500 and 2500â r/min, respectively.
  • Publication
    Indentation characterization of glass/epoxy and carbon/epoxy composite samples aged in artificial salt water at elevated temperature
    (Elsevier, 2022-04-21) Ghabezi, Pouyan; Harrison, Noel M.; Enterprise Ireland
    Micro-level composite properties are a key determinant of the long-term performance and life span of marine-based composite structures. In this paper, the effect of the aging process in salt water at room temperature and elevated temperature on the elastic modulus and hardness of composite specimens have been investigated through indentation testing. To do this, carbon/epoxy (CE) and glass/epoxy (GE) samples were immersed in artificial sea water with 3.5% salinity at room temperature and 60 °C for 90 days. Matrix only and fibre/matrix (fibre constraint) cells have been examined by two different approaches, namely standard indentation testing and continuous stiffness measurement (CSM) methods to measure elastic modulus and hardness in micro level. It was indicated that degradation at 60 °C had a higher effect on elastic modulus than the room temperature aging process. According to the experimental results from the standard method indentation in matrix cells, the average modulus in the aged GE in 60 °C was 3.47 ± 0.1 GPa (22.3% loss). The average modulus in the reference CE samples was 4.7 ± 0.1 GPa, while those values for aged samples at room temperature and 60 °C showed 38.8% and 51.3% losses, respectively. The hardness for the reference GE specimen was 0.189 ± 0.004 GPa, and after the aging process, it dropped by 2.1% (room temperature) and 27.51% (60 °C). Based on the continuous stiffness measurement for matrix cells, the mean value of modulus for the dry GE and CE matrix material cells was calculated as 4 GPa and 3.7 GPa, respectively. During the aging process, the hardness of CE samples decreased from 0.048 GPa to 0.038 GPa at room temperature and 60 °C, respectively, while aging of GE samples at both temperatures after 90 days caused a 31% loss in the hardness compared to the reference specimen. It was evident from the CSM experiments in the fibre constraint cells that the indentation modulus of the dry epoxy matrix constituent increased by 7.5% and 14% by the neighbouring stiff glass and carbon fibre regions respectively. The indentation characterization in GE samples thorough the standard method in the fibre constraint cells showed a 12.58% reduction in modulus at room temperature, and 25.8% at 60 °C compared to the reference specimen.Micro-level composite properties are a key determinant of the long-term performance and life span of marine-based composite structures. In this paper, the effect of the aging process in salt water at room temperature and elevated temperature on the elastic modulus and hardness of composite specimens have been investigated through indentation testing. To do this, carbon/epoxy (CE) and glass/epoxy (GE) samples were immersed in artificial sea water with 3.5% salinity at room temperature and 60 °C for 90 days. Matrix only and fibre/matrix (fibre constraint) cells have been examined by two different approaches, namely standard indentation testing and continuous stiffness measurement (CSM) methods to measure elastic modulus and hardness in micro level. It was indicated that degradation at 60 °C had a higher effect on elastic modulus than the room temperature aging process. According to the experimental results from the standard method indentation in matrix cells, the average modulus in the aged GE in 60 °C was 3.47 ± 0.1 GPa (22.3% loss). The average modulus in the reference CE samples was 4.7 ± 0.1 GPa, while those values for aged samples at room temperature and 60 °C showed 38.8% and 51.3% losses, respectively. The hardness for the reference GE specimen was 0.189 ± 0.004 GPa, and after the aging process, it dropped by 2.1% (room temperature) and 27.51% (60 °C). Based on the continuous stiffness measurement for matrix cells, the mean value of modulus for the dry GE and CE matrix material cells was calculated as 4 GPa and 3.7 GPa, respectively. During the aging process, the hardness of CE samples decreased from 0.048 GPa to 0.038 GPa at room temperature and 60 °C, respectively, while aging of GE samples at both temperatures after 90 days caused a 31% loss in the hardness compared to the reference specimen. It was evident from the CSM experiments in the fibre constraint cells that the indentation modulus of the dry epoxy matrix constituent increased by 7.5% and 14% by the neighbouring stiff glass and carbon fibre regions respectively. The indentation characterization in GE samples thorough the standard method in the fibre constraint cells showed a 12.58% reduction in modulus at room temperature, and 25.8% at 60 °C compared to the reference specimen.
  • Publication
    Short basalt fibre reinforced recycled polypropylene filaments for 3D printing
    (Elsevier, 2022-08-12) Ghabezi, Pouyan; Flanagan, Tomas; Harrison, Noel M.; Horizon 2020
    Additive Manufacturing (3D Printing, and specifically Material Extrusion) is a rapid and convenient manufacturing method using raw material in filament form and is a potential candidate process for the use of recycled plastics and fibres gathered from industrial waste and domestic recycling. In this research, off-cuts of basalt fibre and recycled mushroom trays made of Polypropylene (PP) have been collected, recycled and combined in an extruder to make short fibre reinforced filaments as material extrusion feedstock filament material. A Noztek Touch Dual PID filament maker was utilized to make reinforced PP with 0%, 2%, 5%, and 8% basalt fibre weight fractions. The extruding parameters including motor speed, heating temperatures, cooling fan status, extrusion tension have been optimized to produce a filament made from these waste materials with the desired surface quality, void content, and profile. Microscopic assessment has been carried out to verify the fibre dispersion and above mentioned quality measures in the upcycled filaments. Differential scanning calorimetry has been done to measure the melting and crystallization temperatures of collected polypropylene and recycled filaments, and the tensile strength and elastic modulus of the reinforced recycled polypropylene have been measured in presence of different percentages of short basalt fibres with 4.5 mm length. The produced filaments with 5% wt. of basalt are a good candidate for use as feedstock in manufacturing using 3D printing.Additive Manufacturing (3D Printing, and specifically Material Extrusion) is a rapid and convenient manufacturing method using raw material in filament form and is a potential candidate process for the use of recycled plastics and fibres gathered from industrial waste and domestic recycling. In this research, off-cuts of basalt fibre and recycled mushroom trays made of Polypropylene (PP) have been collected, recycled and combined in an extruder to make short fibre reinforced filaments as material extrusion feedstock filament material. A Noztek Touch Dual PID filament maker was utilized to make reinforced PP with 0%, 2%, 5%, and 8% basalt fibre weight fractions. The extruding parameters including motor speed, heating temperatures, cooling fan status, extrusion tension have been optimized to produce a filament made from these waste materials with the desired surface quality, void content, and profile. Microscopic assessment has been carried out to verify the fibre dispersion and above mentioned quality measures in the upcycled filaments. Differential scanning calorimetry has been done to measure the melting and crystallization temperatures of collected polypropylene and recycled filaments, and the tensile strength and elastic modulus of the reinforced recycled polypropylene have been measured in presence of different percentages of short basalt fibres with 4.5 mm length. The produced filaments with 5% wt. of basalt are a good candidate for use as feedstock in manufacturing using 3D printing.
  • Publication
    Hygrothermal deterioration in carbon/epoxy and glass/epoxy composite laminates aged in marine-based environment (degradation mechanism, mechanical and physicochemical properties)
    (Springer, 2022-01-27) Ghabezi, Pouyan; Harrison, Noel M.
    One of the major challenges in off-shore tidal and wave energy devices is the ageing of these structures in the hostile marine environment, which limits their operating life. In this research, mechanical properties of aged glass/epoxy and carbon/epoxy composite specimens including tensile strength, Youngâ s modulus, flexural strength, and shear strength, following immersion in a representative accelerated marine degradation environment (artificial seawater, with 3.5% salinity at room temperature and 60 °C) have been investigated. The microstructure and physicochemical characterization of the aged samples were assessed via microscopic imaging, micro-CT scanning and differential scanning calorimetry. The degradation phenomenon was apparent in the change of mechanical properties and microstructure of composite laminates (micro-cracks and debonding between matrix and fibre). Generally, the ageing process had a more severe effect on tensile and shear strengths of glass/epoxy samples than those of carbon/epoxy specimens. Reversely, the results of bending tests of carbon/epoxy composites showed more drop-in flexural properties than glass/epoxy samples. The results revealed that degradation mechanisms continue even after reaching the saturation point in composite materials. The achievements of this research present a good understanding of the effect of degradation of composite materials in salt water to deal with their application in real service environment.One of the major challenges in off-shore tidal and wave energy devices is the ageing of these structures in the hostile marine environment, which limits their operating life. In this research, mechanical properties of aged glass/epoxy and carbon/epoxy composite specimens including tensile strength, Youngâ s modulus, flexural strength, and shear strength, following immersion in a representative accelerated marine degradation environment (artificial seawater, with 3.5% salinity at room temperature and 60 °C) have been investigated. The microstructure and physicochemical characterization of the aged samples were assessed via microscopic imaging, micro-CT scanning and differential scanning calorimetry. The degradation phenomenon was apparent in the change of mechanical properties and microstructure of composite laminates (micro-cracks and debonding between matrix and fibre). Generally, the ageing process had a more severe effect on tensile and shear strengths of glass/epoxy samples than those of carbon/epoxy specimens. Reversely, the results of bending tests of carbon/epoxy composites showed more drop-in flexural properties than glass/epoxy samples. The results revealed that degradation mechanisms continue even after reaching the saturation point in composite materials. The achievements of this research present a good understanding of the effect of degradation of composite materials in salt water to deal with their application in real service environment.
  • Publication
    Evaluation and analysis of fracture modes in single composite basalt/epoxy fibres by photoelastic method and single fibre fragmentation test
    (Springer, 2022-04-11) Thornton, Eoghan; Ghabezi, Pouyan; Strain, Findhan; Harrison, Noel M.
    In this work, the suitability of basalt fibres for uni-directional composite material applications, and adhesion between the fibres and the matrix they are embedded in have been investigated. A single fibre fragmentation test was carried out on 13 µm diameter basalt fibres embedded in a dog-bone epoxy matrix. Photoelastic analysis was used to observe different fracture mechanisms in a single fibre composite sample and fibre breaks during testing. A theoretical model based on a Griffithâ s fracture mechanics approach was used to determine the fibre-matrix interfacial shear strength, which is a measurement of the level of adhesion between the fibre and the matrix. It was also used to predict the fibre fragment axial stress and the fragment interfacial shear stress, both as functions of axial position on the fibre. A finite element model was developed to simulate the fibre fracture process, and the redistribution of stresses in the fibre and the local region surrounding a fibre break. The developed experimental procedure was successful in that stress-induced birefringence was observed in the tested samples, as well as the characteristic shear stress light fringes that occur in the regions surrounding fibre fractures. Also, there were some similarities between the finite element model results and the theoretical predictions. The critical fibre length, lc was measured as 0.752 mm, whereas this value was calculated 0.6708 mm from finite element predicted interfacial shear stress distribution for fibre fragment. A combination of all three types of failure modes was recorded across the samples that were tested, while only a single failure mode was observed in the finite element model. According to the theoretical model, for a given set of parameters and constant stress with only the fibre length varying, the axial stress in the fibre reduces as the fibre gets smaller.In this work, the suitability of basalt fibres for uni-directional composite material applications, and adhesion between the fibres and the matrix they are embedded in have been investigated. A single fibre fragmentation test was carried out on 13 µm diameter basalt fibres embedded in a dog-bone epoxy matrix. Photoelastic analysis was used to observe different fracture mechanisms in a single fibre composite sample and fibre breaks during testing. A theoretical model based on a Griffithâ s fracture mechanics approach was used to determine the fibre-matrix interfacial shear strength, which is a measurement of the level of adhesion between the fibre and the matrix. It was also used to predict the fibre fragment axial stress and the fragment interfacial shear stress, both as functions of axial position on the fibre. A finite element model was developed to simulate the fibre fracture process, and the redistribution of stresses in the fibre and the local region surrounding a fibre break. The developed experimental procedure was successful in that stress-induced birefringence was observed in the tested samples, as well as the characteristic shear stress light fringes that occur in the regions surrounding fibre fractures. Also, there were some similarities between the finite element model results and the theoretical predictions. The critical fibre length, lc was measured as 0.752 mm, whereas this value was calculated 0.6708 mm from finite element predicted interfacial shear stress distribution for fibre fragment. A combination of all three types of failure modes was recorded across the samples that were tested, while only a single failure mode was observed in the finite element model. According to the theoretical model, for a given set of parameters and constant stress with only the fibre length varying, the axial stress in the fibre reduces as the fibre gets smaller.
  • Publication
    Mechanical behavior and long-term life prediction of carbon/epoxy and glass/epoxy composite laminates under artificial seawater environment
    (Elsevier, 2019-12-06) Ghabezi, Pouyan; Harrison, Noel M.
    This paper presents an investigation on the long-term performance of carbon/epoxy and glass/epoxy laminates in an artificial seawater environment with 3.5% salinity. Accelerated aging tests were conducted at 60 °C for 45 days to characterize the long-term effect of seawater on the mechanical response of fiber-reinforced composite laminates. Several mechanical tests including tensile and 3-point bending tests have been carried out on the reference/dry and aged standard samples at room temperature and 60 °C to evaluate tensile strength, youngâ s modulus, flexural strength, secant and chord modulus of elasticity in the composite samples. The long-term behavior of carbon/epoxy and glass/epoxy samples under the service construction condition in the coast of Ireland was also predicted using Arrhenius degradation theory.This paper presents an investigation on the long-term performance of carbon/epoxy and glass/epoxy laminates in an artificial seawater environment with 3.5% salinity. Accelerated aging tests were conducted at 60 °C for 45 days to characterize the long-term effect of seawater on the mechanical response of fiber-reinforced composite laminates. Several mechanical tests including tensile and 3-point bending tests have been carried out on the reference/dry and aged standard samples at room temperature and 60 °C to evaluate tensile strength, youngâ s modulus, flexural strength, secant and chord modulus of elasticity in the composite samples. The long-term behavior of carbon/epoxy and glass/epoxy samples under the service construction condition in the coast of Ireland was also predicted using Arrhenius degradation theory.
  • Publication
    Deformation mechanisms of selective laser melted 316L austenitic stainless steel in high temperature low cycle fatigue
    (Elsevier, 2022-04-22) Chen, Yefeng; Wang, Xiaowei; Shen, Jiawei; Peng, Yawei; Jiang, Yong; Yang, Xinyu; Leen, Sean B.; Gong, Jianming; University Natural Science Research in Jiangsu; Science Foundation Ireland
    To investigate the low cycle fatigue (LCF) properties of SLM (Selective laser melting) 316L at 550 °C high temperature, a series of LCF tests at different strain amplitudes is conducted on SLM 316L and traditional 316L. In contrast to the cyclic hardening behavior of traditional 316L, SLM 316L is shown to have a stable cyclic softening behavior and higher fatigue life due to its higher strength (yield strength is 1.9 times of traditional 316L). The coarsening of cellular sub-structure, evolution of geometrically necessary dislocations (GND) and texture direction contribute to the cyclic softening behavior of SLM 316L. Fractographic observations illustrate that strain amplitude has a significant influence on initiation and propagation of transgranular fatigue cracks, and lack-of-fusion defects near the surface are key initiation sites of fatigue cracks. Additionally, the life prediction method of the non-Masing model is suitable for SLM 316L.
  • Publication
    The role of community-engaged learning in engineering education for sustainable development
    (MDPI, 2022-07-05) Goggins, Jamie; Hajdukiewicz, Magdalena; Horizon 2020; Science Foundation Ireland
    This paper presents the positive experience of facilitating over 300 community-engaged engineering projects at an Irish higher-education institution. The projects are framed by a research orientation, a commitment to civic engagement, and building university¿community partnerships, city¿university partnerships, and partnerships with other official agencies, so that community users can provide real learning problems and contexts for students and researchers and benefit from the results. The paper highlights how well the outlined approach fits with the ideas of engaged scholarship and civic professionalism, and facilitates sustainable development. Students recognise the long-term value of engaging with community partners, understanding their future role in the community as engineers, reinforcing the idea that their work can respond directly to real needs in the community, while promoting the sustainability agenda at the same time. The approach presented in this study will not only enable the development of future models for embedding sustainability in engineering programs, but will also equip future engineers with transferable skills to ensure that sustainable development goes beyond university courses and is practiced every day.
  • Publication
    A physically-based method for predicting high temperature fatigue crack initiation in P91 welded steel
    (Elsevier, 2021-08-27) Zhou, Jinbiao; Barrett, Richard A.; Leen, Sean B.; Science Foundation Ireland
    A methodology is presented for physically-based prediction of high temperature fatigue crack initiation in 9Cr steels, with a focus on material inhomogeneity due to welding-induced metallurgical transformations. A modified form of the Tanaka-Mura model for slip band formation under cyclically-softening conditions is implemented in conjunction with a physically-based unified cyclic viscoplasticity constitutive model. The physically-based constitutive model accounts for the key strengthening mechanisms, including precipitate hardening and hierarchical grain boundary strengthening, successfully predicting cyclic softening in 9Cr steels. A five-material, finite element model of a P91 cross-weld test specimen, calibrated using the physically-based yield strength and constitutive models, successfully predicts the measured detrimental effect of welding on high temperature low-cycle fatigue crack initiation for P91 cross weld tests, via the modified Tanaka-Mura model. A key finding of the current work is the requirement to adopt an energy-based Tanaka-Mura method to account for cyclic softening in 9Cr steels, with packet size as the critical length-scale for slip band formation. The work demonstrates the significant effect of highly flexible operation on the service life of welded connections.
  • Publication
    Cosmic sounds: A game to support phonological awareness skills for children with dyslexia
    (2022) Brennan, Attracta; McDonagh, Tara; Dempsey, Mary; McAvoy, John;
    Studies show that reduced literacy skills can negatively influence a child¿s self-esteem and future career opportunities. Literacy is significantly affected when problems exist understanding the phonological component or sound structure of language i.e. phonological awareness. Children with dyslexia in particular, experience difficulties in spelling and reading accuracy due to a deficit in this phonological component of language. To support children with dyslexia and reduced literacy skills, intervention programmes which focus on phonological awareness elements are recommended. Studies show that game based learning (GBL) interventions can enhance learning for children with dyslexia. The purpose of this pilot study was to partner with children with dyslexia aged between 9 to 12 years, to develop a game toolkit called Cosmic Sounds, to support the teaching of phonological awareness skills. The content for the Cosmic Sounds games was informed by a pedagogical expert in dyslexia. This pilot study addressed the following; ¿Can a toolkit of games, co-designed by children with dyslexia improve the teaching of phonological awareness skills?¿ Our findings showed that by including children and their teacher as part of the design team, they were more invested in using the games for learning. Furthermore, when children with dyslexia played Cosmic Sounds, there was a positive impact on their phonological awareness skills progress whilst their engagement in learning also increased.
  • Publication
    Thought-piece on the effectiveness of contemporary project management and its top performing enablers
    (IEEE, 2021-06-10) Dempsey, Mary; Brennan, Attracta; Kaub, Viktoria; McAvoy, John
    One of the most important factors for project success is effective contemporary project management. The aim of this study is to provide project manager practitioners with access to the successful contemporary project management enablers using evidence-based research. A systematic scoping literature review using qualitative and quantitative design was performed on the ScienceDirect database using studies and articles, published in English between 2010 and 2019. This search included factors regarding successful contemporary project management and citation tracking. All studies and articles were peer reviewed. Charted data was narratively reported by clustering the results according to the identified success criteria. The review process resulted in one conceptual framework, one literature review, one survey, and one article about research on another topic which is related to project management success factors. This study shows that to enhance evidence-based practice, it is recommended that in a contemporary project approach, every project establishes a complementary team-related project with gates as checks to ensure transparency, clarity and comprehension. Its purpose would include the definition, development and implementation of clear communication strategy and a mentoring and training programme to support retention, build loyalty in organizations and enhance co-operation between the stakeholders and the project team. A limitation of this study includes the consideration of contemporary project management success factors only but not those success factors influencing contemporary project management success. A second limitation is the use of a single database and the exclusion of journal quality.