Macro-scale Approach Research Articles

Quantitative Advantages of Corrosion Sensing Using Fluorescence, Microscopy, and Single-Molecule Detection.

The corrosion of metals and alloys is a fundamental issue in modern society. Understanding the mechanisms that cause and prevent corrosion is integral to saving millions of dollars each year and to ensure the safe use of infrastructure subject to the hazardous degrading effects of corrosion. Despite this, corrosion detection techniques have lacked precise, quantitative information, with industries taking a top-down, macroscale approach to analyzing corrosion with tests that span months to years and yield qualitative information. Fluorescence, a well-established optical method, can fill the niche of early-stage, quantitative corrosion detection and can be employed for both bulk and localized testing over time. The latter, fluorescence microscopy, can be pushed to greater levels of detail with single-molecule microscopy, achieving nanometer spatial and subsecond temporal resolutions of corrosion that allow for the extraction of dynamic information and kinetics. This review will present how fluorescence microscopy can provide researchers with a molecular view into the chemical mechanisms of corrosion at interfaces and allow for faster, quantitative studies of how to detect and prevent corrosion.

Structural Optimization of a Large-Scale 3D-Printed High-Altitude Propeller Blade with Experimental Validation

This paper presents a structural optimization of a 3D-printed thermoplastic-core propeller blade for high-altitude unmanned aerial vehicles using a genetic algorithm. It aims to minimize the weight of the blade by creating longitudinal holes and spars and to minimize the blade tip deflection during operation at an altitude of 16 km. The objective is to check the validity of a 3D-printed material modeling approach for large-scale and more complex 3D-printed parts, such as hollow twisted blades. The approach is based on attentively selecting the printing parameters that reduce the anisotropy of the 3D-printed parts. The linear isotropic behavior of 3D-printed Polylactic Acid and Acrylonitrile Butadiene Styrene M30 tensile samples, which have been tested at ambient and low temperatures (−60°C), is utilized to numerically predict the experimental deformation and natural frequencies of 3D-printed substitute and twisted full blades with good accuracy. The validated linear isotropic model of each material is then used to evaluate the objectives and the constraints of the two-objective optimization process using one-way fluid–structure interaction. Four optimized blades have been selected from the Pareto fronts as candidates, printed, and tested in bending and vibration. The numerical and experimental results of the candidate blades in terms of deformation and natural frequencies are in good agreement, proving the validity of the present macroscale approach for large-scale hollow twisted blades.

Effect of Post-Cured through Thickness Reinforcement on Disbonding Behavior in Skin-Stringer Configuration.

An experimental investigation of interlaminar toughness for post-cured through-thickness reinforcement (PTTR) skin-stringer sub-element is presented. The improvement in the crack resistance capability of skin-stringer samples was shown through experimental testing and finite element analysis (FEA) modeling. The performance of PTTR was evaluated on a pristine and initial-disbond of the skin-stringer specimen. A macro-scale pin-spring modeling approach was employed in FEA using a non-linear spring to capture the pin failure under the mixed-mode load. The experimental results showed a 15.5% and 20.9% increase in strength for the pristine-PTTR and initial-disbond PTTR specimens, respectively. The modeling approach accurately represents the overall structural response of PTTR laminate, including stiffness, adhesive strength, crack extension scenarios and progressive pin failure modes. This modeling approach can be beneficial for designing damage-tolerant structures by exploring various PTTR arrangements for achieving improved structural responses.

ASSESSMENT OF CO2 EMISSION DUE TO SPEED BUMPS ON SELECTED HIGHWAYS IN BAUCHI STATE

One industry that will emit carbon dioxide (CO2) that is dependent on the production of fossil fuels is transportation. Even though cars emit carbon dioxide (CO2), which contributes to air pollution, fossil fuel-powered vehicles nevertheless require widespread use. Traffic-calming devices act as tools to reduce the rapidity of automobiles. They make a major contribution to road protection; however, air contamination is more likely to arise due to the fact that motor vehicles use brakes and accelerate more regularly. This study examines the impact of speed bumps brought on by elevated carbon dioxide (CO2) levels on selected commercial vehicles, including Vectra, Volkswagon, Peugeot, Ford Galaxy, and Toyota Hiace buses, traveling on highways from Bauchi to Jos, Bauchi to Azare, Bauchi to Gombe, and Bauchi to Kano. To estimate the CO2 emissions of each kind of specified commercial vehicle, the fuel consumption of the vehicles before and after the installation of bumps was gathered using a questionnaire model and examined using a mathematical model using a macro-scale approach. The result shows that there is an increase of 21% in CO2 emissions on the Bauchi to Jos Highway, 15% in CO2 emissions on Bauchi to Azare, 24% in CO2 emissions on Bauchi to Gombe, and 40% in CO2 emissions on Bauchi to Kano. The study concludes that transport-related pollution on Bauchi Highway has indeed significantly increased with the installation of calming traffic devices, which is dangerous to human health and vegetation near these highways.

Relationship between Surface States of Carbon Support and Electrode Reaction Activity in Cathode Catalyst Layer Toward High Power Output of Polymer Electrolyte Fuel Cells by Large-Scale Reactive Molecular Dynamics Simulations

Higher output of polymer electrolyte fuel cells (PEFC) is required for use in many industrial fields such as the transport industry. PEFCs consist of a gas diffusion layer, a catalyst layer (CL), and a polymer electrolyte membrane. The output of PEFCs depends on the electrode reaction activity of the CL consisting of the carbon support, ionomer, water, and Pt nanoparticles (NPs). For high electrode reaction activity, the optimization of the CL structures such as Pt alloy, pore structures of the carbon support, and I/C (Ionomer carbon ratio), are key factors. To optimize the CL structures, computational simulation, which can propose theoretical design principles, is a promising method. Thus, many researchers have investigated the CL structures with high electrode reaction activity by computational simulation to propose design principles. For example, first-principles calculation can optimize highly active Pt catalysts by considering activation barriers, molecular adsorption structures and surface electronic states, which involves the behavior of atoms and molecules. However, this method cannot consider the effects of carbon support, ionomer, and water because of the limitation in computational costs. On the other hand, macro-scale approach using differential equations can discuss the highly active CL structures since this method can consider multiple structures such as carbon support, ionomer distribution, water content, and Pt loading. However, this approach cannot consider the behavior of atoms and molecules. Therefore, large-scale molecular simulations which, can simultaneously consider the behavior of atoms and molecules, and the CL structures are required. Here, reactive molecular dynamics (RMD) simulation is a practical approach to deal with the behavior of atoms and the chemical reactions in the CL. By using RMD method, we successfully constructed large-scale CL structures and established the CL design methodology both including atomic and molecular effects and clarifying the effect of the pore size of carbon support on the electrode reaction activity [1]. In order to design the higher-performance CL structures, we focused on the distribution of water which mediates proton transfer process. Improving the wettability of carbon support by termination of hydroxyl groups to the carbon support surface can alter the water distribution. Therefore, by large-scale RMD simulations, we investigated the effect of the ratio of the hydroxyl groups on the carbon support surface on water distribution to propose design principles for higher-performance cathode CL structures.A CL structures model consisting of 1 million atoms was constructed by modeling carbon support, Pt NPs, ionomer, and water. We selected the carbon support, where there were six meso pores on an amorphous carbon sphere. The ratios of hydroxyl groups to the carbon surface atoms were set to 10 and 32% to control the water distribution on the carbon surface. In addition, Pt NPs were put on the carbon support outer surface and interior of the pores. The water film whose thickness is 0.7 nm and ionomer are coated on Pt-supported carbon. Hereafter, we call this structure catalyst particle (CP) model (Fig. 1).To clarify the effect of the ratio of hydroxyl groups on the carbons support surface, the morphology of the water film was compared in the CP models with different hydroxyl ratios. At the exterior of the pores, the water film was peeled off from the carbon support surface regardless of the ratio of hydroxyl groups. At the interior of the pores, when the ratio of hydroxyl groups was 10%, the water film was peeling from the carbon support surface（Fig. 2(a), (b)). On the other hand, when the ratio of hydroxyl groups was 32%, the water film did not peel off from the carbon support surface, and the structure of the water film was maintained (Fig. 2(c), (d)). Next, to clarify the effect of the water film morphology on the proton conduction to the Pt NPs, the water clusters as proton conduction paths were analyzed. Water clusters were defined as a group of water molecules whose inter-molecular distance is less than 3.5Å. The amount of proton conduction paths to the Pt NPs at the exterior of the pores did not change regardless of the ratio of hydroxyl groups. On the other hand, the amount of proton conduction path to the Pt NPs at the interior of the pores was increased by increasing the ratio of hydroxyl groups (Fig. 3). These results indicate that the increasing the ratio of hydroxyl groups on the carbon support surface to improve the proton conduction path is an effective approach for the design of the higher-performance cathode CL.[1] T. NAKAMURA, M. KUBO et al. J. Comput. Chem. Jpn., 20,150-154, (2021). Figure 1

Comparing acoustic prediction methods for additively manufactured porous structures

While macroscale methods for predicting the acoustic properties of porous structures have been popular in the past, they often require time-consuming manufacturing and testing workflows. Meanwhile, microscale approaches allow the prediction of transport parameters based exclusively on a periodic structure's unit cell geometry. Here, we compare these methods to predict the characteristic impedance of additively manufactured porous structures. We use the microscale approach to estimate the geometry's transport parameters, then predict the characteristic properties using the Johnson-Champoux-Allard (JCA) model. We measure the acoustic properties of the printed structures using a normal incidence impedance tube and estimate the transport parameters using an inverse characterization approach. We use the twothickness method as a macroscale approach to predict the characteristic properties from the measured surface impedances of two sample thicknesses. Finally, we compare these characteristic prediction methods. Our results show that the inverse characterization and twothickness methods offer the closest match to the measured values at low frequencies.

Numerical analysis of large masonry structures: bridging meso and macro scales via artificial neural networks

This paper presents a methodology for analysis of large-scale masonry structures. The approach involves development of a series of artificial neural networks which enable the identification of main variables employed in the macroscopic formulation that incorporates an inelastic constitutive law with embedded discontinuity. The data required for training of neural networks is generated using ‘virtual experiments’, whereby the ‘equivalent’ anisotropic response of masonry is obtained through a mesoscale finite element analysis of masonry wallets. The paper outlines the procedure for identification of approximation coefficients describing the orientation-dependency of strength, and other relevant parameters. A numerical example is provided involving analysis of a large masonry wall with multiple openings. The results of macroscale approach are compared with those based on a detailed mesoscale model for the same geometry and boundary conditions.

Structural Design of a Large-Scale 3D-Printed High-Altitude Propeller: Methodology and Experimental Validation

This paper presents an original approach to the structural design and analysis of a 3D-printed thermoplastic-core propeller blade for high-altitude UAVs. A macroscale linear isotropic numerical model for the behavior of 3D-printed parts (in Tough PLA, as well as ABS) is fed with values from tensile and bending testing on standard specimens (ISO 527-2/1A and ASTM D5023) before validation by experiments on a representative scaled substitute blade and blade root. The influence of printing parameters, such as material, layer thickness, and raster orientation, is also addressed, as well as variability between prints. To conclude on the validity of the present methodology for complex shapes, a validation of the numerical results with experiments was performed on a scaled 3D-printed twisted blade. The presented macroscale approach to 3D-printed materials was able to predict tensile and bending deformation with good accuracy compared to previously published micro- or meso-scale approaches since it is built from systematic tensile and bending testing on standard specimens to representative blade assemblies. It provides a reliable digital twin for the early design stages of 3D-printed propeller blades. As a proof-of-concept, the validated methodology was then used to design and numerically analyze a large-scale blade using steady one-way Fluid-Structure Interaction in take-off and cruise conditions. The computed stress levels in the blade structure were within safe margins, thereby proving the feasibility of the 3D printing of full-scale propeller blades for high-altitude platforms.

Multiscale analysis of the effect of interfacial thermal conductance between fillers and epoxy resin on the effective thermal conductivity of their composites

The heat dissipation performance of the epoxy molding compound(EMC) is very important for high power application. In this paper, the thermal transport properties of thermoset epoxy(EP) based EMC containing silica particles(SiO2Ps) and diamond particles(CPs) were calculated using two different scale approaches. Firstly, the representative volume element(RVE) of EMC was modeled using molecular dynamics(MD) to calculate the effective thermal conductivity(ETC). The crosslinking of EP between Diglycidyl Ether of Bisphenol A(DGEBA) resin and JEFFAMINE® D-230 hardener was modeled. The results indicate that the CPs can increase the ETC of composite by 71.4 % than that of SiO2Ps. The interfacial thermal conductance(ITC) of Silica/EP interface was 1.33 times higher than that of Diamond/EP interface. The discontinuous temperature gradients on interface was observed in the RVE filled with dispersed fillers. In addition, a macroscale approach was used to determine the ETC of the EMC using finite element method(FEM) and the Maxwell theoretical model. The effects of fillers' shape and the ITC of fillers/EP interface on the ETC of EMC were analyzed. With the increase of the ITC, the ETC of the composite increases gradually. When the ITC exceeded a critical value, the ETC did not change. The chain fillers were more conducive to heat transport. The results of the two multiscale modeling techniques were well consistent.

Modeling the oxidation of a polymer-derived ceramic with chemo-mechanical coupling and large deformations

To get a better insight into the coating behavior of a polymer-derived ceramic material, we model and simulate the diffusion, oxidation and reaction-induced volume expansion of a specimen without outer mechanical loads. In this macroscale approach, we use an oxidation state variable which determines the composition of the starting material and the oxide material. The model contains a reaction rate which is based on the change of the free energy due to a change of the concentrations of the starting material, the oxide material and a diffusing gaseous material. Using this, we model a growing oxide layer in a perhydropolysilazane (PHPS)-based polymer-derived ceramic (PDC), containing silicon filler particles. Within the mechanical part of the modeling, we use the Neo-Hookean material law which allows for the consideration of volume expansion and the diffusion kinematics in terms of finite deformations. We derive this continuum formulation in 3D and reduce it later to 1D, as we show that a 1D formulation is sufficient for thin oxide layers in our consideration. In such a case, the reaction-induced volume expansion is mostly limited to strains orthogonal to the oxide layer, as the bulk material hinders transversal deformation. Both formulations, i.e., 1D and 3D, are implemented in the finite element software FEAP. We perform a parameter study and fit the results with experimental data. We investigate the diffusion kinematics in the presence of volume expansion. Additionally, we discuss the influence of the elastic energy on the reaction rate.

Hardness Penetration Depth Prediction in the Grind-Hardening Process through a Combined FEM model

The grind-hardening process aims to increase the surface hardness of the material through the dual action of the mechanical and thermal load. A novel approach to model the process and predict the hardness penetration depth was developed based exclusively on the prediction of austenite-martensite transformation. A combined micro and macro scale approach was implemented to forecast the temperature reached in the surface starting from the action of a single grain and using its specific cutting power to design a moving heat source representing the interaction between the grinding wheel and the material. The martensitic transformation temperature considered in this paper takes into consideration the fast heat cycle typical of this process. In order to validate the model, tangential surface grinding tests were performed on 42CrMo4 and microstructural analysis with micro-hardness measurements were performed. This research presents a first step in developing a grinding process simulation that includes multi-grain grinding, real grain geometries, binder effect, and real workpiece-grinding wheel kinematics.

Litho-climatic characteristics and its control over mangrove soil geochemistry: A macro-scale approach

Brazil hosts an extensive coastal area, marked by a great diversity of geoenvironments. The present study evaluated the role of geoclimatic factors in the geochemistry of mangrove soils by using wet extractions and several physical and chemical parameters. Soil samples were collected in 11 mangrove forests from NE (n = 94) and SE Brazil (n = 230). Our results show an important effect of the surrounding geology and climate on the geochemistry of the mangrove soils. NE mangroves are dominated by suboxic soils (mean: Eh of +150 ± 174 mV and pH 7.1 ± 0.5, respectively) while anoxic conditions prevail in the SE mangrove soils (mean: Eh −46 ± 251 mV and pH 6.5 ± 0.5). In the NE region, a period of several months without rainfall and high temperatures leads to soil suboxic conditions. Conversely, at the SE coast, the surrounding mountain range contributes to well-distributed rain favoring anoxic conditions. The contrasting geochemical environment caused differences in the geochemistry of elements such as C, Fe, and S. Significantly higher Fe (193 ± 24 μmol g−1) and organic carbon contents (6.9 ± 7.1%) were recorded in the SE coast. The higher organic carbon contents are possibly related to Fe organo-mineral associations. These differences are ultimately associated with the contrasting geological surroundings (crystalline massifs at the SE and the iron poor sedimentary formations at the NE). The higher contents of reactive Fe and organic carbon also triggered more intense pyritization in the SE mangroves (pyritic Fe: 93 ± 63 μmol g−1). Our results demonstrate that climate and geological surroundings create identifiable patterns at a regional level and, thus, studies should take these factors into account on future global modelling approaches.

Extra-Low Dosage Graphene Oxide Cementitious Nanocomposites: A Nano- to Macroscale Approach.

The impact of extra-low dosage (0.01% by weight of cement) Graphene Oxide (GO) on the properties of fresh and hardened nanocomposites was assessed. The use of a minimum amount of 2-D nanofiller would minimize costs and sustainability issues, therefore encouraging the market uptake of nanoengineered cement-based materials. GO was characterized by X-ray Photoelectron Spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), and Raman spectroscopy. GO consisted of stacked sheets up to 600 nm × 800 nm wide and 2 nm thick, oxygen content 31 at%. The impact of GO on the fresh admixtures was evaluated by rheology, flowability, and workability measurements. GO-modified samples were characterized by density measurements, Scanning Electron Microscopy (SEM) analysis, and compression and bending tests. Permeability was investigated using the boiling-water saturation technique, salt ponding test, and Initial Surface Absorption Test (ISAT). At 28 days, GO-nanocomposite exhibited increased density (+14%), improved compressive and flexural strength (+29% and +13%, respectively), and decreased permeability compared to the control sample. The strengthening effect dominated over the adverse effects associated with the worsening of the fresh properties; reduced permeability was mainly attributed to the refining of the pore network induced by the presence of GO.

A computational framework for meso and macroscale analysis of structural masonry

In this study a computational framework is outlined for modeling the mechanical response of structural masonry at both meso and macroscale. The mesoscale approach accounts for the presence of distinct constituents (i.e., bricks and mortar joints) and their geometric arrangement. A constitutive law with embedded discontinuity, combined with the level-set approach, is used to model the onset and discrete propagation of localized damage in these constituents. The approach is verified against a range of experimental data published in the literature. It is shown that the proposed framework can adequately predict the load-deformation response, as well as the fracture pattern under combined loading conditions. The macroscale approach incorporates the notion of anisotropy parameter whose value depends on the orientation of the principal stress axes in relation to the axes of material symmetry. The material parameters/function appearing in this approach are identified from the ‘virtual data’ generated by a mesoscale analysis of masonry panels subjected to biaxial tension–compression at different orientations of the bed joint. Thus, the mesoscale considerations serve as a bridge for upscaling to the macrolevel.

Investigating geoarchaeological deposits from Naihehe cave in the Sigatoka River valley of Viti Levu, Fiji

This report summarizes the results of a series of original investigations of Naihehe Cave on Viti Levu, Fiji, which include excavations and laboratory analyses. The goal of this research was to investigate evidence of human occupation of Naihehe cave in prehistory via analyses of sediments, sedimentary processes, and identification of parent materials and anthropogenic deposits. Analyses of sediments were conducted at “macro” and “micro”-scales: the macro-scale approach analyzed aggregates of sediment grains using Fourier Transform Infrared spectroscopy (FTIR) and Laser-ablated Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The micro-scale approach focused on individual grains of sediment using Scanning Electron Microscopy with Energy Dispersion Spectroscopy (SEM-EDS). Identified charcoal and radiocarbon dating were used to determine the age of deposits. The results of these analyses identified different classes of sediment based upon their textural and mineralogical qualities and determined major and minor elemental components of individual grains and aggregates. These in turn provide unique insights into the origin and depositional environment of the cave’s sediments. Analyses also identified anthropogenic deposits via the detection of elemental and mineralogical signatures and intrusive microfossils. Combustion features in the cave’s deposits, two of which produced calibrated radiocarbon dates of 886-1013 CE (2σ) and 260-529 CE (2σ), identify human activity in the cave in the two millennia following human colonization of Fiji. This report discusses these primary findings and argues that instrument-based studies of sediment are insightful for the identification of natural and anthropogenic deposits.

Multi-scale modelling for adhesive wear in tribo-pairs of nano-hydroxyapatite reinforced UHMWPE bio-composite and Co-Cr alloy

The ultra-high molecular weight polyethylene (UHMWPE) is a popular biomaterial. Pre-clinical evaluation of UHMWPE in terms of wear resistance is extremely important to avoid the effect of implant loosening after implantation. This work proposed an efficient and accurate computational modelling approach to predict elasto-plastic properties at meso-scale, and further integrated at macro-scale to predict adhesive wear in dry tribo-pairs condition. The representative volume element (RVE) based finite element technique was used to predict elastoplastic behaviour of nano-hydroxyapatite (nHA) reinforced UHMWPE composite. The predicted values were validated experimentally and applied as a material property of pin during a numerical investigation of adhesive wear by a macro-scale modelling approach. The CoCr alloy was taken as the counter disc material. The integration of Archard's wear model and user-subroutine was done for numerical prediction of wear. The numerically obtained wear rate and friction coefficient results were validated experimentally by a pin on the disc wear setup under dry conditions. The fabrication of the specimen for validation was done by microwave-assisted compression moulding (MACM). The microstructural investigation of worn surfaces was done by scanning electron microscopy (SEM) to understand the mechanism of adhesive wear. The surface mapping of worn surfaces was done using an optical profilometer to observe the surface roughness after adhesive wear. Biocompatibility of the composite material was confirmed by In-vitro direct contact cytotoxicity test

Seasonal Dynamics of Surface Dissolved Organic Matter in the South China Sea and the Straits of Malacca: Implications for Biogeochemical Province Delineation of Marginal Seas

AbstractBiogeochemical provinces are an important aid to identify homogeneous biogeochemical characteristics and underlying ecosystem dynamics in the open ocean. This macroscale approach, however, does not appear to be applicable to marginal seas for disregarding various small scale changes. Here, we adopted two observation schemes throughout the typical marginal seas, the South China Sea (SCS) and Straits of Malacca (MS), with continuous surface‐water sampling during March and May 2018. Spatial and seasonal heterogeneity of hydrological and dissolved organic matter (DOM) properties was investigated. With a novel combination of chromophoric DOM index and classical biogeochemical parameters (temperature, salinity, chlorophyll‐a, and bathymetry), we delineated five biogeochemical provinces in each season to integrate DOM pools and investigate region‐specific and season‐dependent biogeochemical processes. The results showed that the SCS basin was seasonally modulated by biological activities and photodegradation, resulting in the biologically active DOM pools. The western SCS seasonally received terrestrial DOM, subjected to the western boundary current under monsoon regulation. The MS was found to serve as an efficient carbon source of terrestrial substances, which exported to the northern Indian Ocean during the Northeast Monsoon. The delineation favored the simplification of complex biogeochemistry and allowed us to predict future trends in this dynamic system. Chromophoric DOM index was proven applicable to the delineation of marginal seas, that shed the light on the potential applications in biogeochemical provinces in dynamic systems.

Coordinated energy-environmental-economic optimisation of building retrofits for optimal energy performance on a macro-scale: A life-cycle cost-based evaluation

Given that energy-efficiency policies focus on meso- or macro-scale interventions, it is imperative to establish a macro-scale evaluation approach for building retrofits to support policymaking in building energy conservation, management and sustainability. This study applies the generic idea of optimising the energy, economic and environmental outputs to propose a facile framework for evaluating the prospects of building retrofits on a macro-scale. Here, an extensive optimisation approach integratinglife cycle cost evaluation and an environmental assessment is formulated, involving coordinated on-site survey, modelling and data analytics. The model framework is corroborated by a case study analysis focused on identifying the optimal retrofit solution for low-rise office buildings in Shanghai. Simulation results show that modifications in occupancy regime, improvements in natural ventilation, heating and cooling systems, cool roofs insulation and installation of renewable energy systems (such as geothermal and solar/photovoltaics) are the basic retrofit measures for a macro-scale intervention to attain maximum life-cycle benefits. Individually, an estimated investment cost for each retrofit project varied within RMB 1 – 5 million with a payback period < 13 years, depending on the building characteristics. Overall, an investment estimated at RMB 1.7 billion (with a payback period of 6 years) is required to achieve ~ 80% energy reduction with a carbon dioxide savings of ~ 243 Gg-CO2/yr. In summary, this study provides a guidance framework for stakeholders to evaluate investments on retrofit projects, including existing and prospective ones.

Consolidation-driven wrinkling in carbon/epoxy woven fabric prepregs: An experimental and numerical study

An efficient macro-scale finite element approach is introduced to predict defects that arise from the consolidation of carbon fibre woven fabric prepregs. The model incorporates the through-thickness compaction and inter-ply shear behaviour of the plies in the form of a compliant penalty contact in an explicit finite element simulation. For describing the compressibility of uncured prepregs, a one-dimensional compaction model is implemented via a user-subroutine. The model parameters were identified from an experimental programme and validated against compaction and inter-ply shear experiments on a Carbon/Epoxy prepreg. Moreover, the in-plane and out-of-plane behaviour of the woven fabric is captured through a hybrid hypo-elastic membrane and shell modelling approach. The applicability of the model is further demonstrated through a number of industrially relevant case studies. The method is simple, efficient, and it can be applied to assess various scenarios for modelling textile forming and consolidation behaviour.

Measurement and Mitigation of Residual Stress in Wire-Arc Additive Manufacturing: A Review of Macro-Scale Continuum Modelling Approach

Wire-arc additive manufacturing (WAAM) has recently attracted researchers to produce metal components with a high-deposition rate. Many researchers are trying to establish the WAAM process as a high-deposition metal additive manufacturing (AM) process. A computationally efficient mathematical model used for the metal-AM process yields a framework for component qualification as per international standards. Since heat transaction in the AM process can control the thermal-field generated through continuous heat deposition. Therefore, the present study focuses on the critical review of multi-physics continuum modelling of WAAM at a macro-scale level. Thermo-mechanical model for WAAM has been discussed extensively, i.e., heat-source models, materials models, meshing strategy, and boundary conditions. Further, a review of the simulation results discussed as thermal fields, residual stress and distortion, and experimental validation to provide a critique of real-life experiments. Also, various residual stress/distortion mitigation techniques used in the WAAM have been compiled to provide a framework for future directions.