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Additively manufactured mechanical metamaterials are gaining prominence in lightweight energy-absorption applications due to their exceptional mass-specific properties. Herein, we examine the energy absorption characteristics of micro-architected truss-, shell- and plate-lattice structures, namely, Octet, Kelvin, Gyroid, SC, BCC and FCC over a range of relative densities under quasi-static compression via both experiments and finite element analysis (FEA). Employing different 3D printing methods, namely, Digital Light Processing, Selective Laser Sintering and Material Jetting, the lattices were fabricated using PlasGray™ (photo-resin based plastic), PA12 (Nylon) and VeroWhite (photo-resin based rigid plastic) respectively. Our results indicate that the SC lattice structure outperforms in terms of stiffness and strength, while the Gyroid lattice outperforms in terms of energy absorption efficiency (η). At lower relative densities (

Abstract Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks, provide safe and smooth rides, and reduce the maintenance frequency. In this paper, the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in Abaqus. It is then compared to the performance of a ballasted track. First, slab and ballasted track models are developed to replicate the full-scale testing of track sections. Once the models are calibrated with the experimental results, the novel slab model is developed and compared against the calibrated slab track results. The slab and ballasted track models are then extended to create linear dynamic models, considering the track geodynamics, and simulating train passages at various speeds, for which the Ledsgård documented case was used to validate the models. Trains travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil, considering the issues associated with critical speeds. Various train loading methods are discussed, and the most practical approach is retained and described. Moreover, correlations are made between the geotechnical parameters of modern high-speed rail and conventional standards. It is found that considering the same ground condition, the slab track deflections are considerably smaller than those of the ballasted track at high speeds, while they show similar behaviour at low speeds.

Abstract Lateral wander of autonomous truck can be further improved by optimizing the uniform wander. Increase in available lane width for the autonomous trucks can increase the performance efficiency of this mode. This research is based on finding the optimum, combination of lane width increment and asphalt layer thickness reduction among different scenarios. Therefore, In this research with assumed maximum lane width of 4.35 m, difference combination of lane width and asphalt layer thickness scenarios have been analyzed using finite element modelling in ABAQUS. Considering the base pavement width of 3.75 m, increment for each scenario is 15 cm and reduction in asphalt layer thickness is at 2 cm. Performance efficiency of each scenario is conducted while considering the initial construction costs and damage assessment for each scenario. Moreover, life cycle cost analysis (LCCA) is conducted for the base scenario and selected optimum scenario. Results show that increase in pavement width beyond 4.2 m, renders the scenarios uneconomical and thus, the scenario consisting of 4.2 m lane width and 16 cm asphalt layer thickness yield a maximum performance efficiency of 20% among all other alternatives. LCCA analysis shows that a difference in salvage value of 42 million Euros exists when compared with the base scenario. By selecting the optimum lane width of 4.2 m and asphalt layer thickness of 16 cm, Pavement lifetime can be further increased by 13 years with full depth reclamation used as maintenance intervention.

The use of periodical elliptically-based web (EBW) openings in high strength steel (HSS) beams has been increasingly popular in recent years mainly because of the high strength-to-weight ratio and the reduction in the floor height as a result of allowing different utility services to pass through the web openings. However, these sections are susceptible to web-post buckling (WPB) failure mode and therefore it is imperative that an accurate design tool is made available for prediction of the web-post buckling capacity. Therefore, the present paper aims to implement the power of various machine learning (ML) methods for prediction of the WPB capacity in HSS beams with (EBW) openings and to assess the performance of existing analytical design model. For this purpose, a numerical model is developed and validated with the aim of conducting a total of 10,764 web-post finite element models, considering S460, S690 and S960 steel grades. This data is employed to train and validate different ML algorithms including Artificial Neural Networks (ANN), Support Vector Machine Regression (SVR) and Gene Expression Programming (GEP). Finally, the paper proposes new design models for WPB resistance prediction. The results are discussed in detail, and they are compared with the numerical models and the existing analytical design method. The proposed design models based on the machine learning predictions are shown to be powerful, reliable and efficient design tools for capacity predictions of the WPB resistance of HSS beams with periodical (EBW) openings.

Nuclear power generation constitutes a significant component of the energy infrastructure within the United States. The dry cask storage system canister, used for storing highly radioactive spent fuel, demands vigilant structural health monitoring. This paper explores the feasibility of monitoring of stress corrosion cracking in large-scale dry cask storage system canisters using acoustic emission sensors. In this paper, a 304H stainless steel plate, reflecting a typical canister, was subjected to conditions inducing stress corrosion cracking by exposure to a potassium tetrathionate solution and tensile stresses. Analysis of the captured acoustic emission signals showed that the sensors were able to detect this corrosion even at considerable distances from the cracks. Moreover, a finite element model was designed to simulate the acoustic emission signals, thus providing a preliminary understanding of the signal profiles at different sensor locations and potentially providing guidance on the optimal placement of the sensors during field monitoring.

The demand for small-batch manufacturing processes has increased considerably in recent years due to the need for personalized and customized products. Single point incremental forming (SPIF) has emerged as a time-efficient approach that offers increased material formability when compared to conventional sheet metal forming techniques. However, the complexity of SPIF requires a complete understanding of the material deformation mechanism. In this study, a non-conventional contactless tool in the form of hot compressed air is employed to form a polycarbonate sheet. The influence of the contactless tool on the shaping process is modeled and analyzed with a finite element modelling (FEM). Two different models were developed and coupled to estimate the resulting shape of the sheet. A CFD model was created to obtain pressure and temperature values of the air impacting the sheet, while a transient structural model was employed to study the deformation of the sheet. The research provides a working model that is able to predict the performance of this contactless incremental forming process of polymers with high accuracy. The comprehensive FE model developed in this work is able to forecast the final part geometries and dimensions in addition to the normal strain progression. It also revealed that the primary modes of deformation in SPIF were stretching, thinning, and bending. The model was validated by experimental results, and the predicted sheet deformation was compared to the one generated experimentally, and the results obtained were in good agreement. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional (3D) finite element model (FEM) consisting of an asphalt concrete (AC) overlay on top of jointed plain Portland cement concrete (PCC) slabs was developed to investigate the mechanism of the crack initiation of traffic-induced reflective cracking. Strain values at the bottom of AC overlay were the primary response obtained from the simulation results to represent the damage induced in the AC layer. Different bonding situations between the two layers, traffic load locations, material properties and thicknesses of the AC layer were taken into consideration. The analysis results show that the dominating strain for damage is dependent on the bonding condition between the AC and PCC layers. When the AC layer is completely bonded with the PCC layer, the damage will initiate firstly at the top of the joint corner between the PCC slabs to deteriorate the bonding, then the AC bottom will be susceptible to bending strain. It was observed that the most critical load location for modeling the case of fully bonded overlays is related to the AC thickness while in the case of partially bonded overlays, the most critical load location is always located on the top of one side of the PCC joint. [ABSTRACT FROM AUTHOR]

Abstract\nUNSTRUCTURED ABSTRACTSagittal Craniosynostosis (SC) is a congenital craniofacial malformation, involving premature sagittal suture ossification; spring-assisted cranioplasty (SAC) – insertion of metallic distractors for skull reshaping – is an established method for treating SC. Surgical outcomes are predictable using numerical modelling, however published methods rely on computed tomography (CT) scans availability, which are not routinely performed. We investigated a simplified method, based on radiation-free 3D stereophotogrammetry scans.Eight SAC patients (age 5.1 ± 0.4 months) with preoperative CT and 3D stereophotogrammetry scans were included. Information on osteotomies, spring model and post-operative spring opening were recorded. For each patient, two preoperative models (PREOP) were created: i) CT model and ii) S model, created by processing patient specific 3D surface scans using population averaged skin and skull thickness and suture locations. Each model was imported into ANSYS Mechanical (Analysis System Inc., Canonsburg, PA) to simulate spring expansion. Spring expansion and cranial index (CI - skull width over length) at times equivalent to immediate postop (POSTOP) and follow up (FU) were extracted and compared with in-vivo measurements.Overall expansion patterns were very similar for the 2 models at both POSTOP and FU. Both models had comparable outcomes when predicting spring expansion. Spring induced CI increase was similar, with a difference of 1.2%±0.8% for POSTOP and 1.6%±0.6% for FU.This work shows that a simplified model created from the head surface shape yields acceptable results in terms of spring expansion prediction. Further modelling refinements will allow the use of this predictive tool during preoperative planning.Spring-assisted cranioplasty (SAC) –insertion of metallic distractors helping skull reshaping – is a method for treating sagittal craniosynostosis, caused by premature sagittal suture closure. We present a method for predicting SAC outcomes, relying on radiation-free 3D stereophotogrammetry scans. Eight patients with preoperative CT and 3D stereophotogrammetry scans were recruited; results of spring expansion simulation were compared between models created using CT versus 3D scan data. Expansion patterns and extent of reshaping were very similar. This work proves that SAC preoperative planning can be carried out using non-ionising imaging. Further modelling refinements will allow clinical adoption of this predictive tool. [ABSTRACT FROM AUTHOR]

Discontinuous-long-fibre (DLF) composites fabricated from pre-impregnated unidirectional (UD) fibre chips are susceptible to structural deficiency. The in-plane highly anisotropic mechanical properties of the chips combined with the random nature of fibre orientation causes local weaknesses within the material when fibres are perpendicular to the load. Recent experimental results have shown that using woven-fibre chips could improve the performance of DLF composites by increasing their average mechanical properties and reducing their variability. To better understand the underlying phenomenon giving an advantage to the woven chips, a finite element model was developed to predict the mechanical properties obtained from a standard tensile test. DLF chips were modelled based on a voxel method where random chip positions were generated by an algorithm developed in this work. ANSYS® software was utilized to model the non-linear response associated with progressive damage of the composite. The maximum stress and the Puck failure criteria were employed to define damage initiation for the woven and UD fibres, respectively. Tensile modulus predictions for both types of chips showed good results when compared to experimental data. Strength predictions for the UD fibres also showed good correlation with experimental results, but the model overestimated the strength of the woven-fibre DLF composite. It appeared that the failure of the UD-fibre composites was associated with matrix failure (transverse tension and in-plane shear). Woven-fibre composites, however, showed damage modes linked to both fibre failure (longitudinal tension) and matrix failure (transverse tension and in-plane shear). [ABSTRACT FROM AUTHOR]

The traction performance of the footwear deteriorates due to outsole wear which further increases the risk of slip and fall related accidents. To date, several studies have tested footwear tractions across several slippery conditions but only a few studies have attempted to assess their performance considering worn shoes. In this work, nine outsoles, with systematically modified tread geometries, were investigated, to study the effects of tread patterns in new and worn conditions on traction, across common slippery conditions. The outsoles were progressively worn in three wear cycles. Outsoles with increased worn regions generated lower friction and higher fluid pressures, indicating increased slipping risks. Also, diversion of fluid flow due to large worn regions produced high fluid accumulations at other locations over the outsoles. The methods and results are anticipated to help footwear manufacturers with the strategic design of tread patterns that can provide improved friction even when completely worn. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of ridged (micro-grooved) surface finish over the trunnion surface on the mechanics (stress, strain, and deformation) of the head–neck taper interface in hip implants. Using finite element modelling, the study focused on the geometric parameters of such micro-grooves to study how they would mechanically affect stress and deformation fields after the assembly procedure. As such, five different 2D models with varying micro-groove height and spacing were produced and assembled under an impaction assembly force of 4 kN in a 32 mm CoCrMo head engaged with a 12/14 Ti-6Al-4V neck. The results showed that lower von Mises stresses could be induced by either an increase or decrease in spacing against the base model (Model 1), which probably signifies that the relationship between the ridge spacing and stress may depend on the level of spacing. It was concluded that the geometrical parameters of the ridges (and their non-linear interactions) impact not only the stress and strain fields but also the assembly loading time at which the maximal stress and plastic deformation occur. [ABSTRACT FROM AUTHOR]

Tungsten carbide particles reinforced metal matrix composite (MMC) coatings can significantly improve surface wear resistance owing to their increased surface hardness. However, the presence of macro‐ and micro‐residual stresses in MMC coatings can have detrimental effects, such as reducing service life. In this study, neutron diffraction was used to determine the residual stresses in spherical fused tungsten carbide (sFTC) reinforced Cu matrix composite surface deposits after laser melt injection. We also developed a thermo‐mechanical coupled finite element model to predict residual stresses. Our findings reveal that sFTC/Cu composite deposits produced with a preheating temperature of 400°C have low residual stresses, with a maximum tensile residual stress of 98 MPa in the Cu matrix on the top surface. In contrast, the sFTC/bronze (CuAl10Ni5Fe4) composite deposit exhibits very high residual stresses, with a maximum tensile residual stress in the Cu matrix on the top surface reaching 651 MPa. These results provide a better understanding of the magnitudes and distributions of residual stresses in sFTC‐reinforced Cu matrix composite surface deposits manufactured via laser melt injection. [ABSTRACT FROM AUTHOR]

The voids beneath cement concrete slabs are a major invisible disease, resulting in a rapid decrease in service performance in the composite pavement. Accurate voids prediction is essential for the extensive application and long-term service of composite pavement. This research provides a FEM-ANN (Finite Element Modelling-Artificial Neural Network) method to predict the voids beneath concrete slabs. These ANN models include the original back propagation (BP), the particle swarm optimisation (PSO) BP model, the genetic algorithm (GA) BP model, and the whale optimisation algorithm (WOA) BP model. The voids FEM model is established and validated by the measured data in the field, and the relative error of measured and simulated results is within 4%. The cross-validation results show that the WOA-BP model has the best prediction performance, with the highest score of 8, which refers to the overall score of the mean value and variance of these evaluation indices. Therefore, this FEM-ANN framework is an efficient method for estimating the voids beneath concrete slabs. Furthermore, it is discovered that the base modulus with the highest contribution degree of 20.34% is the most dominant factor in predicting the voids output. A FEM-ANN method is utilised to predict the voids beneath concrete slabs The WOA-BP model exhibits the best comprehensive performance of the four ANN models. ${\rm W}_d$ W d and pavement mechanical responses have a positive effect on ${\rm A}_v$ A v opposite to ${\rm K}_d$ K d and pavement structure. The base modulus is the primary factor in predicting the voids output. [ABSTRACT FROM AUTHOR]

This paper aims to develop a general form of the time-temperature-ageing shift model for bituminous materials based on free volume theory and validate its application in the Finite Element (FE) modelling for predicting aged asphalt mixtures' mechanical responses. The frequency sweep, dynamic modulus, and Fourier Transform Infrared Spectroscopy (FTIR) tests were used to validate the proposed time-temperature-ageing shift model. A generalised Maxwell model incorporating the proposed shift model of asphalt mixtures was used to predict the mechanical responses of aged asphalt mixtures using FE modelling, verified via laboratory cyclic load tests. Results indicate that the time-temperature-ageing shift function can model the complex shear modulus and dynamic modulus master curves of bituminous materials, addressing the modulus dependency of temperature and ageing. Temperature dominates the modulus change of bituminous materials in the ageing process. The coefficients of the time-temperature-ageing shift model have clear physical meanings and can potentially quantify the effects of asphalt mixtures' air voids on their temperature and ageing susceptibilities. The time-temperature-ageing shift model can be incorporated into the constitutive relations of the FE model to effectively couple and efficiently predict the effects of temperature and ageing on the mechanical responses of aged asphalt mixtures. [ABSTRACT FROM AUTHOR]

Biodynamic modelling of seat-occupant systems can assist in seat comfort design. A finite element (FE) model of the seated human body, including detailed modelling of the lumbar spine, was established to reflect the human response to vibration and biodynamic response of the lumbar spine under whole-body vibration (WBV). The lumbar spine model was established and validated against the in-vitro results and calculated data. The posture of the lumbar spine was adjusted according to the radiological research results, and the adjusted model was combined to establish a FE model of the seated human body. The present seated human model with backrest inclination angles of 10, 20, and 30°, validated by comparing the measured apparent mass and seat-to-lumbar spine transmissibility, was used to calculate the biodynamic response of the lumbar spine with three inclined backrests under WBV. The results showed that the model could characterise the apparent mass, seat-to-lumbar spine transmissibility, and the biodynamic response of the lumbar spine. Practitioner summary: Biodynamic models can represent dynamic characteristics of the human body exposed to vibration and assist in seat comfort design. The three-dimensional FE model of the human body can be used to explore the human response to vibration and the biodynamic response of the lumbar spine under WBV. [ABSTRACT FROM AUTHOR]

This paper presents the historical development of the vertical extensions of unreinforced masonry buildings in the Eixample district of Barcelona and their impact on the seismic behaviour. Existing masonry buildings of Eixample present significant seismic risk because, despite the low to moderate seismic hazard of Barcelona, they show a marked vulnerability given their average height of six storeys and the substantial slenderness of the walls. Between the end of the 19th century and the beginning of the 20th century, the vertical extensions, known as remuntes in Catalan, were a common solution to the increasing demographic demand of the city. In their majority, these vertical extensions add a structural irregularity that represents a potential vulnerability factor not yet investigated. The present study focuses on Eixample's remuntes, including their historical development, the description of their structural features, and the identification of their most representative configurations in the existing building stock. A seismic analysis based on the Finite Element Method is presented on a reference model without extensions and three others with the most recurrent configurations of remuntes. The seismic response is investigated through pushover analysis. The results provide a better understanding of the negative impact of the vertical extensions on the seismic performance. [ABSTRACT FROM AUTHOR]

Temperature distribution in a forging process influences the lubricant behaviour and die-wear. Non-uniform temperature distribution at the die-work interface results in the breakdown of lubrication film, which increases the heat generation due to increased friction. This work investigates the temperature distribution in the forging of a workpiece with a single asperity using the finite element (FE) simulations. Effects of asperity height in relation to workpiece, friction at die-work interface, percentage reduction and die velocity are studied. During the forging process, the temperature developed at the asperity region rises very rapidly. The asperity attains the maximum temperature after attaining its full height deformation. For the same deformation of workpiece, the temperature at asperity increases with an increase in the asperity height. The temperature at the asperity reduces with an increase in the friction at the die-work interface. The temperature at asperity as well as on the whole workpiece increases with increasing reduction. As heat dissipation from the workpiece surface is more at a relatively lower speed, the maximum temperature developed at asperity is greater at a higher speed. Insight provided by these simulations will assist in understanding the tribology of metal forming. [ABSTRACT FROM AUTHOR]

This research work aims to perform a structural optimisation of a steel tower used to support a 2 MW wind turbine, considering the natural frequencies, stresses, buckling resistance, and displacement constraints, to reduce the volume of steel required for the structure. The investigated structure is modelled based on the use of a three-dimensional finite element model that includes the soil–structure interaction effect, the rotor loads and the wind nondeterministic effect acting on the steel tower. Due to the nature of the mathematical formulation presented for the dynamic effect of the wind, a statistical analysis of the dynamic response of the structure as well as the results of the nondeterministic optimisation is performed to obtain the results within a 95% confidence level. Based on the obtained results, it was shown that the optimisation process considering the dynamic nondeterministic effect of the wind leads to a project, the volume of which is 31.5% lower than the original volume and only 4.5% higher than the project obtained considering its static effect. However, it was concluded that taking to account the wind nondeterministic mathematical formulation, the optimised steel tower structural design presents greater robustness to uncertainties associated with the numerical modelling of the wind loadings. [ABSTRACT FROM AUTHOR]

The need for materials for high-temperature applications has always been a topic of research for various engineering applications. The need for materials for high-temperature applications is an important need specifically for defense and space applications where they are subjected to very high temperatures during reentry into the earth's atmosphere. Carbon/Carbon composites are promising materials for various fields of engineering. These materials are increasingly opted for due to their ability to withstand high temperatures above 3000 °C. Engineering designers have an important role in designing the components and sub-systems using these materials for high-temperature applications. Prediction of elastic constants for these materials is a significant step in the design of the components. The current work is aimed at the prediction of elastic constants. Elastic constants of unidirectional carbon/carbon composites are predicted in this work. Unit cell models of unidirectional carbon/carbon composites containing random positioning of fibers were created. Elastic constants were evaluated by applying periodic boundary conditions. The carbon/carbon test samples were fabricated to validate the predicted elastic constants. The PAN-based carbon fiber with carbon matrix was used for the fabrication of unidirectional carbon/carbon test samples. The uncertainty of measurement for the experiments was estimated using guide to the expression of uncertainty of measurement. The predicted values of elastic constants agree closely with the experimental results. [ABSTRACT FROM AUTHOR]

In the framework of the international benchmark "Vulcain tests on 3 Walls", three full scale ISO fire tests on a reinforced concrete wall, simultaneously subjected to a constant uniaxial compressive load, were conducted in CSTB in Paris, France. The duration of these tests exceeded 120 min. In order to assess the capability of available finite elements (FE) models to represent reinforced concrete structural behaviour under fire exposure, IRSN, within the scope of the Vulcain benchmark, set up a modelling with help of Mazars isotropic continuum damage mechanical model (Mazars Application de la mécanique de l'endommagement au comportement non linéaire et à la rupture du béton de structure. PhD Thesis, Univ. Paris 6, ENS Cachan, France, 1984) ran with the CAST3M software (Verpeaux et al. in Fouet, Ladevèze and Ohayon (eds), Calcul des Structures et Intelligence Artificielle, Pluralis, 1988), while a user-defined procedure was used to calculate the concrete properties taking into account load induced thermal strains (LITS). The effect of LITS according to the model of Anderberg and Thelandersson (Stress and deformation characteristics of concrete at high temperatures: 2 experimental investigation and material behavior model, Bulletin 54, Lund Institute of Technology, Lund, 1976) was considered by an explicit term in the strain decomposition. Also, the numerical simulation of three full scale ISO fire tests of Vulcain was carried out with the help of a FE model that takes into account the values of the concrete thermomechanical parameters identified. The numerical model is composed of two different parts, one for heat transfer analysis and the other one for structural analysis based on a three-dimensional FE model including concrete and reinforcing steel meshes. It is illustrated through this numerical investigation that the proposed model can predict the thermomechanical behaviour of reinforced concrete walls under fire exposure. [ABSTRACT FROM AUTHOR]

This research investigates the impact of reduced graphene oxide (rGO) on the temperature gradient and associated stresses of mass mortar blocks. When the thermal stresses induced by the temperature gradient between the core of mass mortar or concrete blocks and their surfaces exceed the tensile strength of the concrete, cracking can occur. The measurements of temperature evolution at several locations in two mortar blocks with dimensions of 0.48 m x 0.41 m x 0.68 m are obtained from the literature. The first block was cast with a reference mix (REF) which contains only ordinary Portland cement, whereas the cement was replaced by 1.2% rGO for the other block. A finite element simulation of the two blocks was carried out and the measured temperature evolution was captured with a reasonable precision. Subsequently, numerical simulation was used to investigate the influence of rGO on the temperature rise and the associated potential of cracking in the mass mortar blocks with dimensions of 1 m x 1 m x 1 m and 2 m x 2 m x 2 m. It is noted that the rGO has a significant effect on reducing the the cracking indices of mass mortar blocks. [ABSTRACT FROM AUTHOR]

The numerical response of one-storey reinforced concrete frames designed following design standards before the enactment of modern seismic provisions was investigated in this study using the nonlinear finite element method. An unbraced frame and two frames retrofitted with a buckling restrained brace (BRB) incorporating either a stainless steel or chrome molybdenum core bar were modelled. The nonlinear static reverse cyclic loading performance of the frames was assessed. Modifications to the BRB are proposed to mitigate deficiencies identified with the original BRB and steel core bars. The modified BRB incorporating a superelastic shape-memory alloy (SE-SMA) core bar was further modelled. The results illustrate the benefits of implementing SE-SMA as a retrofit strategy to control permanent displacements. The modified BRB with a SE-SMA core exhibited improved lateral strength and displacement capacities relative to the frames retrofitted with steel cores and the control bare frame. [ABSTRACT FROM AUTHOR]

• Threshold voltages for transcranial motor evoked potentials (tcMEPs) were least for linked quadripolar (LQP), higher for M3-M4, and highest for C1-C2 stimulation sites. • Finite element model simulations of resistance and current densities in the hand "knob" may explain these threshold requirements. • Local topography of current densities in motor cortex with tcMEP threshold stimulation was similar for LQP, M3-M4 and C1-C2. The aim of this study was to compare stimulation thresholds and current densities in the brain for transcranial motor evoked potentials (tcMEPs) from the hands and feet with linked quadripolar (LQP), M3-M4 and C1-C2 electrode montages. Twenty-five patients underwent cerebral vascular surgery with tcMEP monitoring. tcMEP voltage thresholds were compared between LQP (C1, M3, C2, M4), C1-C2, and M3-M4 montages. In a finite element model (FEM), hand, arm, and leg regions of interest (ROIs) on the cortical motor homunculus were segmented. Current densities in these ROIs at tcMEP thresholds were compared across tcMEP electrode montages. LQP tcMEP thresholds were 61.5 volts for hands and 95.2 volts for feet. Thresholds were higher for M3-M4 (hands, 89.4 V; feet, 141.3 V) and C1-C2 (hands: 137.3 V; feet: 194.7 V). Total current at threshold voltage was greater for LQP (hands, 210.9 mA; feet, 311.3 mA) compared to M3-M4 (hands, 166.8 mA; feet, 256.6 mA), but similar to C1-C2 (hands, 246.7 mA; feet, 341.1 mA). In FEM simulations, current density and local current density topography in the hand ROI at threshold were very similar for LQP, M3-M4 and C1-C2. TcMEP voltage thresholds were least for LQP, and lesser for M3-M4 compared to C1-C2. In FEM simulations, resistance to current to hand ROI was ordered the same (LQP < M3-M4 < C1-C2). The local distribution of current density in motor cortex with tcMEP was mainly determined by cortical geometry. Current densities and resistance to current simulated with FEM may explain threshold requirements for tcMEP electrode montages. [ABSTRACT FROM AUTHOR]

Understanding damage mechanisms and quantifying damage is important in order to optimise structures and to increase their reliability. To achieve this goal, experimental‐ and simulation‐based techniques are to be combined. Different methods exist for the analysis of damage phenomena such as fracture mechanics, phase field models, cohesive zone formulations and continuum damage modelling. Assuming a typical [1−d]$[1-d]$‐type damage formulation, the governing equations of continua that account for gradient‐enhanced ductile damage under mechanical and electrical loads are derived. The mechanical and electrical sub‐problems give rise to the local form of the balance equation of linear momentum, the micromorphic balance relation and the continuity equation for the electric charge, respectively. Experimental investigations indicate that changes in electrical conductivity arise due to the evolution of the underlying microstructure, for example, of cracks and dislocations. Therefore, motivated by deformation‐induced property changes, the effective electrical conductivity is assumed to be a function of the damage variable. This eventually allows the prediction of experimentally recorded changes in the electrical resistance due to mechanically‐induced damage processes. Interpreting the resistivity as a fingerprint of the material microstructure, the simulation approach proposed in the present work contributes to the development of non‐destructive electrical‐resistance‐based characterisation methods. To demonstrate the applicability of the proposed framework, different representative simulations are studied. [ABSTRACT FROM AUTHOR]

Three-dimensional numerical simulation for clarifying the seismic response characteristics of an underground structure considering the influences of dynamic interaction with the surrounding liquefied soil is still a huge challenge. Using the proposed generic loosely coupled nonlinear effective stress method for site response of liquefiable soil, the authors developed an effective stress seismic response analysis of the underground subway station structure. Based on the effective stress method, the responses of the model underground subway station with three floors and three spans in model liquefiable foundation in the shaking table test are simulated. The comparison between the measured and simulated results proves that the developed method can effectively capture the response characteristics of the liquefiable foundation，by which the generation of residual excess pore water pressure and the effect of cyclic stiffness softening and degradation can be taken into good consideration, and the measured responses of model underground structure can be well reproduced. The results also demonstrate the availability of the shaking table test simulating the dynamic interaction between the underground structure and the surrounding liquefied soil. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubes have become popular due to their desirable properties, including compressive strength, plasticity, and ease of construction. This study aimed to comprehensively analyze the axial response of short columns made of concrete-filled austenitic stainless steel tubes. The different parameters of these columns were carefully evaluated and compared to principal international design codes. This analysis gained a deeper understanding of the structural behavior of concrete-filled stainless-steel tubes under axial compression. Based on the data obtained from the parametric study, two supervised machine learning models were used to model the compression behavior of these elements, the artificial neural networks model and the random forest model. It was observed that the results obtained through machine learning algorithms provide a significantly more accurate response than the models available in design codes. Additionally, it was observed through the study that the best results were achieved with the artificial neural networks model, with a correlation coefficient of 0.99. The trained machine learning models were implemented into software, allowing the prediction of the behavior of these structures in the range of the data presented in the study. [ABSTRACT FROM AUTHOR]

The present paper aims to propose a reliable analysis of ball-on-three-balls and four-point bending experiments applied to advanced ceramics combining statistical analyses, numerical modelling and fractography. MgAl 2 O 4 transparent spinel ceramic was selected to facilitate the assessment of samples quality. Following the material processing procedure detailed in the literature, numerous spinel samples of two different geometries (20 and 60 mm in diameter) were produced. Knoop Hardness and Young's modulus values of 11.8 GPa and 290 GPa were measured, respectively. A three-modal grain size distribution was observed through the sample's thickness. Biaxial bending tests have been performed in conjunction with numerical simulations using Abaqus/Standard®. Thus, parallelism defects were taken into account and their effects on the maximal stress and effective volume were quantified. They were found to be very close to the only published data. In addition, four-point bending experiments were carried out and validated using an ultra-high-speed camera. The scattering of the bending strength was modelled using a two-parameter Weibull distribution and the maximum likelihood approach. 90% confidence intervals of the parameters and confidence bounds of the probability of failure were computed using the likelihood ratio test. This approach is more suitable than Monte Carlo simulations with regard to computational costs. According to the Weibull theory and biaxial bending strength distribution, the material strength, rescaled for different effective volumes was slightly overestimated, in comparison with four-point bending results. Fractographic analyses on uniaxial bending samples revealed that fractures originate from large grains. The corresponding study on biaxial bending samples revealed that carbon inclusions located near to the surface seem to be responsible for failure. Finally, this study brings additional arguments for a more intensive use of the ball-on-three-balls set-up especially when concerns about costs, sample geometry and test practicality are raised. [ABSTRACT FROM AUTHOR]

Stainless steels are modern high-performance construction materials exhibiting excellent corrosion resistance, recyclability, ductility, and durability which make them appealing to use in the construction industry. However, when used as structural sections, they are subjected to localised failure in the web. This study aims to examine the structural behaviour of cold-formed low-carbon content standard austenitic 304L and 316L stainless steel channels under localised interior bearing loads. The results of 21 tests on unlipped channels with different cross-section sizes and thicknesses are presented. A nonlinear quasi-static Finite Element (FE) model is then developed. The FE model is validated against experimental test results and demonstrated good agreement in terms of bearing strength and failure modes. In addition, the experimental and FE results are used to compare the results against the results predicted in accordance with the American specification SEI/ASCE 8:2002 and European Standard EN 1993-1-4:2006. It is found that the current design equations are unreliable and too unconservative to use for cold-formed austenitic stainless steel unlipped channels, especially when compared to SEI/ASCE 8:2002, as much as 41%. [ABSTRACT FROM AUTHOR]

The aim of this work is to answer the question: how to realize high energy and high‐power lithium‐ion batteries. Lithium‐metal and graphite anodes with nickel manganese cobalt (NMC) cathodes of varying thickness are investigated with finite element modelling. The overpotential analysis is performed to pinpoint the source of losses and the possible ways to decrease them. The electrolyte overpotential, resulting from the salt concentration gradient and leading to saturation and depletion of lithium in parts of the cell is identified as the main factor causing poor specific capacity at high discharge/charge currents. The influence of various parameters, including concentration and transference number of lithium salt in the electrolyte, NMC particle size, electrolyte conductivity and the exchange current density, on the galvanostatic response of modelled battery cells is discussed. The increase of the transference number would improve the performance as this would decrease the electrolyte salt concentration gradient. Lithium depletion effect can be also minimized by elevating the initial electrolyte salt concentration, as well as by increasing the porosity of the cathode, particularly at the cathode/separator boundary. [ABSTRACT FROM AUTHOR]

The Mg alloy vascular clip has biodegradability and good biocompatibility, which can improve the convenience and safety of clinical application. However, the Mg alloy vascular clip also has some disadvantages, such as an unreasonable structure design and a degradation rate which is too fast. In this study, the process of clamping blood vessels with a biodegradable Mg alloy (Mg-Zn-Nd-Zr and Mg-Zn-Nd) general V-type vascular clip was simulated by finite element simulation software (Abaqus). A new type of vascular clip, the P-type vascular clip, was analyzed and investigated through simulation. The differences between Mg alloy vascular clips of V-type and P-type were analyzed by finite element simulation. In addition, the effects of Zr element on the mechanical properties and corrosion resistance of P-type vascular clips were also investigated to improve the mechanical stability. The results show that during the V-type vascular clip closure of Mg-Zn-Nd-Zr alloy, this clip has some problems, such as uneven distribution of blood vessel stress, crevices in blood vessels and stress concentration. The improved P-type vascular clip has uniform closure, and there is no gap in the blood vessel, which can effectively avoid stress concentration. The improved P-type vascular clip is well closed and can effectively avoid stress concentration. The corrosion resistance of the Mg-Zn-Nd-Zr alloy P-type clip was better than that of the Mg-Zn-Nd alloy P-type clip (degradation rate of 2.02 mm/y and 2.61 mm/y on the 7th day, respectively). Mg-Zn-Nd-Zr alloy The P-type vascular clip remained closed even on the 7th day, which could meet the requirements of clinical application. [ABSTRACT FROM AUTHOR]

Abstract Selection of optimum platoon pattern based on types of trucks inside the platoon, the number of trucks in the platoon, headway distance, interplatoon distance as well as the use of different lateral wander modes for autonomous trucks has been analyzed. The objective of this research is to study the impacts of axle configurations, truck grouping, headway distance and lateral wander options on the performance of truck platoons. Four different headway distances from 2 to 5 m are compared. The first platoon PT-1 only consists of semi trailers, the second platoon PT-2 only consists of rigid body trucks and the third platoon PT-3 consists of equally distributed random traffic mix. Analysis has been conducted using the dload subroutine for projecting zero wander and uniform wander movements for each truck in the platoon on a three layered pavement crossection at vehicle speeds of 90 km/h for a total of 15 years of pavement lifetime consisting of 1.4 million equivalent single axle loads in finite element software ABAQUS. Results show that PT-3 platoon yields the minimum accumulation of damaging strains when compared against other platoon types. A headway distance of 5 m is suggested when using a zero wander mode and 3 m when using a uniform wander mode. In case of zero wander mode, fatigue life of the pavement decreases by 1.2 years and the use of uniform wander mode delays the rutting by 1.6 years, thereby increasing lifetime of the pavement.

Sand liquefaction under static and dynamic loading can cause failure of embankments, slopes, bridges and other important infrastructure. Sand liquefaction in the seabed can also cause submarine landslides and tsunamis. Fabric anisotropy related to the internal soil structure such as particle orientation, force network and void space is found to have profound influence on sand liquefaction. A constitutive model accounting for the effect of anisotropy on sand liquefaction is proposed. Evolution of fabric anisotropy during loading is considered according to the anisotropic critical state theory for sand. The model has been validated by extensive test results on Toyoura sand with different initial densities and stress states. The effect of sample preparation method on sand liquefaction is qualitatively analysed. The model has been used to investigate the response of a sand ground under earthquake loading. It is shown that sand with horizontal bedding plane has the highest resistance to liquefaction when the sand deposit is anisotropic, which is consistent with the centrifuge test results. The initial degree of fabric anisotropy has a more significant influence on the liquefaction resistance. Sand with more anisotropic fabric that can be caused by previous loading history or compaction methods has lower liquefaction resistance.

The murine tibia compression model, is the gold standard for studying bone adaptation due to mechanical loading in vivo. Currently, a key limitation of the experimental protocol and associated finite element (FE) models is that the exact load transfer, and consequently the loading conditions on the tibial plateau, is unknown. Often in FE models, load is applied to the tibial plateau based on inferences from micro-computed tomography (μCT). Experimental models often use a single strain gauge to assess the three-dimensional (3D) loading state. However, a single strain gauge is insufficient to validate such FE models. To address this challenge, we develop an experimentally calibrated method for identifying the load application region on the tibial plateau based upon measurements from three strain gauges. To achieve this, axial compression was conducted on mouse tibiae (n=3), with strains gauges on three surfaces. FE simulations were performed to compute the strains at the gauge locations as a function of a variable load location. By minimising the error between experimental and FE strains, the precise load location was identified; this was found to vary between tibia specimens. It was further shown that commonly used FE loading conditions, found in literature, did not replicate the experimental strain distribution, highlighting the importance of load calibration. This work provides critical insights into how load is transferred to the tibial plateau. Importantly, this work develops an experimentally informed technique for loading the tibial plateau in FE models.

Aseptic loosening is the most common failure mode for total hip arthroplasty, and the design of the implant plays a significant role in influencing the longevity and stability of the implant. Finite Element (FE) models have been demonstrated to be powerful numerical tools that allow for generating information supporting the device’s safety and/or efficacy during pre-clinical assessment. Different authors have proposed FE studies aiming to simulate the long-term stability of the femoral stem; however, multiple improvements are still necessary for translating computational methodologies into clinical practice. This paper provides a comprehensive overview of the modelling procedures for predicting aseptic loosening risk, focusing on cementless femoral stems. The main modelling assumptions, including bone and implant geometry, materials, boundary conditions, and bone–implant interface contact, were summarised and presented. The limitations of various modelling assumptions and their impact on the simulation results were also discussed. The analysis suggests that more rigorous clinical validation for osseointegration models and failure criteria used to determine loosening of the implant should be clearly defined, and efforts should be made to identify the appropriate limit of tolerable conditions.

Transverse joints are introduced in jointed plain concrete pavement systems to mitigate the risk of cracks that can develop due to shrinkage and temperature variations. However, the structural behaviour of jointed plain concrete pavement (JPCP) is significantly affected by the transverse joint, as it creates a discontinuity between adjacent slabs. The performance of JPCP at the transverse joints is enhanced by providing steel dowel bars in the traffic direction. The dowel bar provides reliable transfer of traffic loads from the loaded side of the joint to the unloaded side, known as load transfer efficiency (LTE) or joint efficiency (JE). Furthermore, dowel bars contribute to the slab’s alignment in the JPCP. Joints are the critical component of concrete pavements that can lead to various distresses, necessitating rehabilitation. The Swedish Transport Administration (Trafikverket) is concerned with the repair of concrete pavement. Precast concrete slabs are efficient for repairing concrete pavement, but their performance relies on well-functioning dowel bars. In this study, a three-dimensional finite element model (3D-FEM) was developed using the ABAQUS software to evaluate the structural response of JPCP and analyse the flexural stress concentration in the concrete slab by considering the dowel bar at three different locations (i.e., at the concrete slabs’ top, bottom, and mid-height). Furthermore, the structural response of JPCP was also investigated for several important parameters, such as the joint opening between adjacent slabs, mispositioning of dowel bars (horizontal, vertical, and longitudinal translations), size (diameter) of the dowel bar, and bond between the slab and the dowel bar. The study found that the maximum LTE occurred when the dowel bar was positioned at the mid-depth of the concrete slab. An increase in the dowel bar diameter yielded a 3% increase in LTE. Conversely, the increase in the joint opening between slabs led to a 2.1% decrease in LTE. Additionally, the mispositioning of dowel bars in the horizontal and longitudinal directions showed a 2.1% difference in the LTE. However, a 0.5% reduction in the LTE was observed for a vertical translation. Moreover, an approximately 0.5% increase in LTE was observed when there was improved bonding between the concrete slab and dowel bar. These findings can be valuable in designing and evaluating dowel-jointed plain concrete pavements.

This study aims to analyse, using a finite element analysis, the effects of Ti-base abutment height on the distribution and magnitude of transferred load and the resulting bone microstrain in the bone-implant system. A three-dimensional bone model of the mandibular premolar section was created with an implant placed in a juxta-osseous position. Three prosthetic models were designed: a 1 mm-high titanium-base (Ti-base) abutment with an 8 mm-high cemented monolithic zirconia crown was designed for model A, a 2 mm-high Ti-base abutment with a 7 mm-high crown for model B, and a 3 mm-high abutment with a 6 mm-high crown for model C. A static load of 150 N was applied to the central fossa at a six-degree angle with respect to the axial axis of the implant to evaluate the magnitude and distribution of load transfer and microstrain. The results showed a trend towards a direct linear association between the increase in the height of the Ti-base abutments and the increase in the transferred stress and the resulting microstrain to both the prosthetic elements and the bone/implant system. An increase in transferred stress and deformation of all elements of the system, within physiological ranges, was observed as the size of the Ti-base abutment increased.

Cryo-rolled aluminum alloys have a much higher strength-to-weight ratio than cold-rolled alloys, which makes them invaluable in the aerospace and automotive industries. However, this strength gain is frequently accompanied by a formability loss. When uniformly applied to the blank surface, hydroforming provides a solution by generating geometries with constant thickness, making it possible to produce complex structures with “near-net dimensions”, which are difficult to achieve with conventional approaches. This study delves into the cavity die sheet hydroforming (CDSHF) process for high-strength cryo-rolled AA5083 aluminum alloy, focusing on two primary research questions. Firstly, we explored the utilization of a nonlinear 3D finite-element (FE) model to understand its impact on the dimensional accuracy of hydroformed components within the CDSHF process. Specifically, we investigated how decreasing fluid pressure and increasing the holding time of peak fluid pressure can be quantitatively assessed. Secondly, we delved into the optimization of process parameters—fluid pressure (FP), blank holding force (BHF), coefficient of friction (CoF), and flange radius (FR)—to achieve dimensional accuracy in hydroformed square cups through the CDSHF process. Our findings reveal that our efforts, such as reducing peak fluid pressure to 22 MPa, implementing a 30 s holding period, and utilizing an unloading path, enhanced component quality. We demonstrated this with a 35 mm deep square cup exhibiting a 16.1 mm corner radius and reduced material thinning to 5.5%. Leveraging a sophisticated nonlinear 3D FE model coupled with response surface methodology (RSM) and multi-objective optimization techniques, we systematically identified the optimal process configurations, accounting for parameter interactions. Our results underscore the quantitative efficacy of these optimization strategies, as the optimized RSM model closely aligns with finite-element (FE) simulation results, predicting a thinning percentage of 5.27 and a corner radius of 18.64 mm. Overall, our study provides valuable insights into enhancing dimensional accuracy and process optimization in CDSHF, with far-reaching implications for advancing metal-forming technologies.

Abstract Slabs with cast-in-place steel formwork are composite structural elements composed of concrete and steel. The horizontal shear failure mode is the most common in composite slabs based on numerous experimental studies. This failure mode consists of loss of adherence and mechanical contact at the interface of the composite system and often occurs before the system reaches its full bending capacity. Thus, the design of this constructive system is determined by the value of the longitudinal shear strength, which can be computed by the semi-empirical so-called traditional m-k method based on the four-point bending test proposed by several standards. One of the most known factors to influence the longitudinal shear strength is the geometry of embossments present in the steel work. Calibrated computational simulation using the finite element method can be an alternative way to simulate this type of test. The present work modified and adapted a methodology explicitly including the geometry of embossments in the analysis in order to use materials and products with characteristics available to structural engineers in Brazil and used this methodology to derive m-k coefficients. This is being made with the objective of numerically simulating the effect of relevant parameters for determining the longitudinal shear strength at the concrete-steel interface of composite slabs. Force versus slip, force versus displacement graphs were obtained and the m-k coefficient values found were compared with those of other authors in the literature. The simulations presented values consistent with the literature and in relation to the rupture mode by longitudinal shear, the numerical simulations performed presented ultimate strengths with goodness-of-fit measured by the conventional coefficient of determination, reaching a good value for the semi-empirical relation using the results of the finite element data.

A novel type of tubular structure with negative Poisson's ratio based on gyroid-type triply periodic minimal surfaces (TPMSs) is proposed in this study. This work is an attempt to design auxetic tubular structures based on TPMS. A series of auxetic tubular structures were designed and then fabricated using laser power bed fusion. Compressive behaviours of the fabricated auxetic tubular structures were investigated using experimental and numerical methods. To obtain optimal designs of tubular structures with controllable auxetic properties, the influence of several parameters were investigated comprehensively. Subsequently, several graded auxetic tubular structures were designed based on the parametric analysis and studied numerically. The mechanical properties of the tubular structures could be controlled effectively using the proposed approach. The proposed method can be used for guiding the design and optimisation of auxetic tubular structures, showing excellent potential for various applications such as biomedical devices, vehicle crashworthiness, and protective engineering.

As drone technology grows in popularity, its application to automate aspects of society is increasing at a similar rate, where drones are now being trialled for delivering payloads over short distances. In order to progress the technology, 3D composite printing is being used to develop complicated parts for improved aerodynamic design that can be produced efficiently, where the resultant composite part has high specific strength and rigidity. This article reports 3D printing of high specific strength, high-temperature Polyamide 6 (Onyx), continuous glass-fibre reinforced Onyx, and carbon-fibre reinforced Onyx composites and characterising their mechanical and fracture behaviour. The Onyx + CF composites displayed up to 1243 % and 1344 % improvement in Young's modulus and tensile strength over neat Onyx samples. The flexural strength of Onyx + CF samples was up to 316.6 % higher than the flexural strength of the neat Onyx sample. SEM micrographs showed a strong bond between the hydration products and the carbon fibres, increasing their tensile and flexural strengths by preventing micro-crack propagation through fibre pull-out and breaking. The statistical analysis was conducted to ensure the validity of the results for the population and establish stress-strain relations, along with estimating errors. In addition, the carbon-fibre-reinforced Onyx composite was compared with commercially used alternatives for producing drone components. Finally, a finite element model was developed using a numerical homogenisation approach and validated to predict the tensile and flexural behaviour of Onyx and carbon-fibre reinforced Onyx samples. This study provides a direction for the next generation of drone manufacturers.

Solid waste management has become a significant environmental challenge globally. This study aims to examine the performance of sustainable concrete incorporating polyethylene terephthalate (PET) granules as partial (0%, 10%, 30%, and 50%) volumetric replacement of sand. The mechanical properties including compressive strength, tensile strength and elastic modulus were examined. The flexural and cracking performance of the reinforced concrete (RC) beams, as well as bond behaviour of concrete mixes with steel reinforcement were investigated. Incorporating 10% PET granules demonstrated positive impact on the mechanical properties, flexural strength and cracking behaviour of RC beam, as well as bond strength. A theoretical model was proposed for predicting bond strength of concrete containing PET granules and the results corresponded well with both experimental and previous research findings. The American and Australian standards conservatively predicted cracking and flexural moments of the RC beams. Finite element modelling was conducted on the RC beams and the results corresponded well with the experimental findings.

Purpose: To investigate the differences of patellofemoral joint pressure and contact area between the process of stair ascent and stair descent. Methods: The finite element models of 9 volunteers without disorders of knee (9 males) to estimate patellar cartilage pressure during the stair ascent and the stair descent. Simulations took into account cartilage morphology from magnetic resonance imaging, joint posture from weight-bearing magnetic resonance imaging, and ligament model. The three-dimension models of the patella, femur and tibia were developed with the medical image processing software, Mimics 11.1. The ligament was established by truss element of the non-linear FE solver. The equivalent gravity direction (-z direction) load was applied to the whole end of femur (femoral head) according to the body weight of the volunteers, and the force of patella was observed. A paired-samples t-test or Wilcoxon rank sum test to make comparisons between stair ascent and stair descent. Statistical analyses were performed using SPSS 22.0 using a P value of 0.05 to indicate significance. Results: During the stair descent (knee flexion at 30°), the contact pressure of the patella was 2.59 ± 0.06Mpa. The contact pressure of femoral trochlea cartilage was 2.57 ± 0.06Mpa. During the stair ascent (knee flexion at 60°), the contact pressure with patellar cartilage was 2.82 ± 0.08Mpa. The contact pressure of the femoral trochlea cartilage was 3.03 ± 0.11Mpa. The contact area between patellar cartilage and femoral trochlea cartilage was 249.27 ± 1.35mm2 during the stair descent, which was less than 434.32 ± 1.70mm2 during the stair ascent. The area of high pressure was located in the lateral area of patella during stair descent and the area of high pressure was scattered during stair ascent. Conclusion: There are small change in the cartilage contact pressure between stair ascent and stair descent, indicating that the joint adjusts the contact pressure by increasing the contact area. [ABSTRACT FROM AUTHOR]