Search

The paper considers an important problem of assessing the stability and strength of various elements of underground structures. The work complements the general scientific and methodological base of such concepts as “stability and strength of elements of underground structures” and forms the principles of selection the criteria of “stability and strength of elements of underground structures”. The proposed approaches and technologies are demonstrated on the examples of solving applied problems of geomechanics. The first of the problems considered is the problem of the strength of a multilayer rock massif during mining operations. The strength of the massif is evaluated based on various criteria. Some recommendations on the choice of strength criteria for this type of problem are given. The second problem is the problem of assessing the long-term stability of the underground structures of a large cross-section. The long-term stability of an underground structure of non-standard geometry is considered taking into account the rheological effects occurring in the rock massif.

The increase in slenderness of building projects has been crucial for reducing the natural frequency values, causing excessive vibration problems. Two other important aspects, generally disregarded in the current design practice are related to the effects of the masonry infills and the soil-structure interaction. This research work aims to develop an analysis methodology to evaluate the human comfort of buildings subjected to the wind nondeterministic dynamic actions. This way, the dynamic behavior of a 16-storey reinforced concrete building, 48 m high and dimensions of 15.0 m by 14.2 m is investigated. Numerical models with different characteristics were developed to obtain a more realistic representation of the system, based on the Finite Element Method (FEM), through the use of the ANSYS program. The results have indicated relevant quantitative differences when the dynamic structural response of the building was analysed, such as the significant reduction on the horizontal translational displacements and peak acceleration values, when the effects of the masonry infills and the soil-structure interaction were considered.

Abstract The evaluation and design of concrete bridges in large part depend on the transverse distribution characteristics of the live load carried and the service level. The live load distribution for continuous concrete multicell box-girder bridges varies according to bridge configuration, so when designing such bridges, it is important to determine the maximum negative stress at the piers, the midspan positive (tensile) stress and the deflection of the bridge when subjected to live loads. This paper reports an extensive parametric study to determine the maximum stress, deflection, and moment distribution factors for two span multicell box-girder bridges based on a finite element analysis of 120 representative numerical model bridges. Bridge parameters were selected to extend the parameters and ranges of current live load distribution factors defined by AASHTO LRFD specifications. The results indicate that the span length, number of boxes, and the number of lanes all significantly affect the positive (tensile) and the negative (compression) stress distribution factors. A set of equations proposed to describe the behavior of such bridges under AASHTO LRFD live loads yielded results that agreed closely with the numerically derived results for the stress and deflection distribution factors.

The present research work intends to perform a wide set of structural analyses upon corrugated composite laminated panels and based on these analyses, to assess their mechanical response in correspondence to the constructive solutions, which may range from the composite materials selection to the geometrical features and other modelling parameters. To improve the mechanical performance of those panels one may consider enhancing their geometrical characteristics, their corrugation shape configuration and the materials used to build them. In this latter case, when considering materials selection, laminated composites may also constitute an important alternative. In any case it is considered necessary to assess the impact that each of these parameters may have in the static and in the free vibration behaviour of the structures, in a comprehensive and detailed way. To achieve the main objective of this research work, a comprehensive and diversified set of case studies is considered in order to characterize the influence that each of the modelling, material and geometrical parameters and characteristics may have in the mechanical response of a corrugated panel. This study allowed concluding that for the wide set of design parameters considered, the fibre orientation and corrugation parameters are the ones responsible for the majority of the significantly improved performances.

The article describes a developed technique of a numerical simulation of the stress-strain state of complex-reinforced elements, which allows you to create models of double-span continuous. The performed experimental and theoretical studies allowed us to carry out the testing of the developed design model and to justify the reliability of the proposed numerical simulation methodology. The results of the experimental studies were compared with those of the theoretical studies. The theoretical calculus algorithm was developed by using the finite element method. Theoretical calculations were performed by using the mathematical-graphical environment software system LIRA-SOFT and the mathematical and computer program MATLAB. On the basis of the experimental research, the iso-fields of displacements and stresses in the materials of an eccentrically compressed beam with a small bend of the slab were constructed, which collapse behind the inclined narrow strip of concrete and displacements and stresses in the materials of the eccentrically stretched beam, which is destroyed due to the yield of the upper mounting armature.

Continuous-wave pulse generator plays an important role in generating high-quality pulse signals in measurement while drilling systems. However, the generator affects the quality of pressure wave signals due to erosion on the continuous wave generator rotary valve caused by drilling fluid during operation. In this paper, the computational fluid dynamics (CFD) model of a rotary valve was established by ANSYS finite element method, and a series of three dimensional flow field simulation experiments were conducted to analyze the influence of factors, such as drilling fluid density, viscosity, inclusion particle diameter, and particle mass flow on the erosion of the rotary valve. Experiments show that the rotor erosion increases with increasing drilling fluid density, viscosity, diameter, and mass flow of particles in the drilling fluid. Moreover, the rotor erosion exponentially increases with increasing viscosity of the drilling fluid. The results provide necessary data for drilling fluid system improvement, rotor material selection, and surface structure treatment.

Water leakage and debris accumulation caused by the expansion joints in a bridge superstructure reduce the service life of the bridge and increase the maintenance costs. A link slab is an effective means to eliminate the expansion joints, providing a continuous deck system. However, the load-caused concrete cracking of the link slab also leads to problems associated with water leakage and rebar corrosion. In order to solve these problems, a new type of steel–concrete composite link slab (SCC-LS) was designed to continuously subject the bridge deck to a positive bending moment and surface concrete compression, which reduced the cracking damage in the link slab. This paper presents the mechanical performance results of the SCC-LS obtained using full-scale model tests. Furthermore, theoretical calculations and finite element (FE) models of the jointless bridge validated the performance based on the experimental results. The results of this study show that the SCC-LS can effectively solve the problem of concrete cracking on the surface of the bridge deck, which has theoretical reference significance and engineering application value for the structural design, maintenance and transformation of continuous simply supported bridge decks and the promotion of seamless bridges.

Despite much research and applications, glass material and its use in buildings is still challenging for engineers due to its inherent brittleness and characteristic features such as sensitivity to stress concentrations, reduction in strength over time and from temperature, and breakage due to the stresses that may build up because of thermal gradients. This paper presents the results of an original test series carried out on monolithic glass panes with the dimensions of 500 × 500 mm2 and different thicknesses, under the exposure to radiant heating. The research study also includes a one-dimensional (1D) heat transfer model and a numerical, three-dimensional (3D) thermo-mechanical model that are used to investigate in greater detail the phenomena observed during the experiments. As shown, the behaviour of glass under radiant heating is rather complex and confirms the high vulnerability of this material for building applications. The usability and potential of thermo-mechanical numerical models is discussed towards experimental feedback.

A multiscale modelling approach has been applied to the simulation of the electrical properties of oral tissue, for the purpose of informing an electrical impedance-based method of oral potential malignant disorder (OPMD) diagnosis. Finite element models of individual cell types, with geometry informed by histological analysis of human oral tissue (normal, hyperplastic and dysplastic), were generated and simulated to obtain electrical parameters. These were then used in a histology-informed tissue scale model, including the electrode geometry of the ZedScan tetrapolar impedance-measurement device. The simulations offer insight into the feasibility of distinguishing moderate dysplasia from severe dysplasia or healthy tissue. For some oral sites, simulated spectra agreed with real measurements previously collected using ZedScan. However, similarities between simulated spectra for dysplastic, keratinised and non-dysplastic but hyperkeratinised tissue suggest that significant keratinisation could cause some OPMD tissues to exhibit larger than expected impedance values. This could lead to misidentification of OPMD spectra as healthy. Sources of uncertainty within the models were identified and potential remedies proposed.

It has recently been shown that the mechanical properties of thin, rectangular wooden plates can be tuned by carving them with specific patterns of perforations, effectively realising a 2D wooden mechanical metamaterial. Such a material is of great interest for the construction of musical instruments, as it could allow a new degree of creative control for makers. Furthermore, issues with the shrinking supplies of tone-woods could be alleviated as wood samples that don not meet the desired requirements could simply be altered, instead of being discarded. In this work, we study the effect of the use of these metamaterials in the soundboards of classical guitars. By way of simulations, we evaluate their impact on the modal behaviour and on the sound pressure level of the instrument, as well as on its ability to sustain the load exerted by the strings. Our results show that the metamaterials can tune the instrument’s response without compromising its structural integrity. We thus conclude that the use of wooden mechanical metamaterials in the soundboards of classical guitars is feasible and, in many ways, beneficial, not the least since it opens the door to using non-traditional woods with bespoke density and stiffness.

Large attachments can dramatically affect the dynamic response of an assembled structure. In various industrial sectors, e.g., the automotive, aircraft, and shipbuilding industries, it is often necessary to predict the dynamic response of assembled structures and large attachments in early-stage engineering design. To deal with this, it is often the finite element method (FEM) that is used in the vibrational analysis. Despite the advent of large-scale computer availability, it is still commonplace, and often necessary, to reduce the model-size with large attachments to acceptable levels for computer time-scale or memory-size limitations. This article discusses the simple methodology of replacing large and sometimes complicated attachments by using a simplified boundary condition. This methodology is well-known in certain sectors of computer-aided design, but here we are able to present a comprehensive discussion from laboratory measurements, finite element analysis and a simplified perspective. Given the availability of experimental data, the errors produced by these methodologies may then be determined by a structure that has a strictly defined geometry and known material properties within a certain tolerance. To demonstrate these effects, an experimental modal analysis is performed on a structure consisting of a beam and a large mass attachment, which is then validated by each of the finite element models that include the relevant approximate ideal boundary conditions. Various approximating boundary conditions are investigated, and quantifiable results are discussed. One of the conclusions confirms the recommendation that rotary inertia terms should be included as a boundary condition wherever possible when large attachments are approximated by an offset mass defined at a point. [ABSTRACT FROM AUTHOR]

Bracing is the most common treatment to stop the progression of adolescent idiopathic scoliosis. Finite element modeling could help improve brace design, but model validation is still a challenge. In this work, the clinical relevance of a predictive and subject-specific model for bracing was evaluated in forty-six AIS patients. The model reproduces brace action and the patient's spinopelvic adjustments to keep balance. The model simulated 70% or more patients with geometrical parameters within a preselected tolerance level. Although the model simulation of the sagittal plane could be improved, the approach is promising for a realistic and predictive simulation of brace action. [ABSTRACT FROM AUTHOR]

Bone tissue exhibits piezoelectric properties and thus is capable of transforming mechanical stress into electrical potential. Piezoelectricity has been shown to play a vital role in bone adaptation and remodelling processes. Therefore, to better understand the interplay between mechanical and electrical stimulation during these processes, strain-adaptive bone remodelling models without and with considering the piezoelectric effect were simulated using the Python-based open-source software framework. To discretise numerical attributes, the finite element method (FEM) was used for the spatial variables and an explicit Euler scheme for the temporal derivatives. The predicted bone apparent density distributions were qualitatively and quantitatively evaluated against the radiographic scan of a human proximal femur and the bone apparent density calculated using a bone mineral density (BMD) calibration phantom, respectively. Additionally, the effect of the initial bone density on the resulting predicted density distribution was investigated globally and locally. The simulation results showed that the electrically stimulated bone surface enhanced bone deposition and these are in good agreement with previous findings from the literature. Moreover, mechanical stimuli due to daily physical activities could be supported by therapeutic electrical stimulation to reduce bone loss in case of physical impairment or osteoporosis. The bone remodelling algorithm implemented using an open-source software framework facilitates easy accessibility and reproducibility of finite element analysis made. [ABSTRACT FROM AUTHOR]

Hydrodynamic cavitation treatment was used for the functional inactivation of quorum-sensing lactone molecules of Pseudomonas aeruginosa. Hydroxyl radicals formed as well as the shear effects during the cavitation process induced the inactivation of the signal molecules through hydrolysis reaction coupled with bacterial destruction. Concentration of two different types of homoserine lactones (HSL) molecules was tested after the treatment at various rotational speeds. It was found that the strongest effects can be achieved at speeds > 2000 rpm. This value is considered as an onset speed of dominant cavitation, and it is in agreement with literature data. The experimental trends were in agreement with the calculations based on the finite element modelling, which show a significant increase in average shear stress at higher rotational speeds. Overall, the work has demonstrated the possible effects of hydrodynamic cavitation on the quorum-sensing molecules of Pseudomonas aeruginosa for the first time. [ABSTRACT FROM AUTHOR]

Grain refinement by severe plastic deformation (SPD) techniques, as a mechanism to control microstructure (recrystallization, grain size changes,...) and mechanical properties (yield strength, ultimate tensile strength, strain, hardness variation...) of pure aluminium conductor wires, is a topic of great interest for both academic and industrial research activities. This paper presents an innovative finite element (FE) model able to describe the microstructural evolution and the continuous dynamic recrystallization (CDRX) that occur during equal channel angular drawing (ECAD) of commercial 1370 pure aluminium (99.7% Al). A user subroutine has been developed based on the continuum mechanical model and the Hall-Petch (H-P) equations to predict grain size variation and hardness change. The model is validated by comparison with the experimental results and a predictive analysis is conducted varying the channel die angles. The study provides an accurate prediction of both the thermo-mechanical and the microstructural phenomena that occur during the process characterized by large plastic deformation. [ABSTRACT FROM AUTHOR]

One of the critical factors that govern the technology of concrete self-healing evaluation at laboratory scale is the crack induction pattern within the concrete sample. Within the various techniques of inducing artificial cracks, such as the flexural testing or splitting testing methods, there are limitations of inducing the microcracks homogenously throughout the entire volume of the concrete sample. In this study, an innovative technique is utilised to induce the microcracks at a controlled damage level to further study the self-healing phenomena in concrete at the laboratory scale. By placing a concrete sample into an ad-hoc fabricated steel mould and applying fractional compressive strength, the axial-circumferential pressure induces microcracks in the concrete sample, homogenously. A Finite Element Model was also built to investigate the hypothesis on the cracking pattern at various damage levels; jointly, experimental work was conducted with X-ray µCT images to reconstruct the three-dimensional sections at the various damage levels. Qualitative analyses in relation to the two test methods were conducted. Furthermore, quantitative analyses on the individual—artificially generated—cracks were conducted in terms of the crack size crack geometry variation and the orientation of the newly formed cracks. Results revealed that the proposed crack-inducing methodology is highly efficient to induce uniform cracks in the sample, assisting for the evaluation of concrete self-healing process. The novel method can be adapted to identify the optimised strategies for enhancing the structural performance of concrete, thus facilitating the safe operation of concrete infrastructure. [ABSTRACT FROM AUTHOR]

This study presents a series results of plate loading tests on a clay with various construction and demolition (CD) materials conducted in a large-scale model box and a numerical verification on the use of these material mixtures. The tests have been applied to the clay with three different types of CD materials (concrete, asphalt, and brick) prepared in a reinforced concrete circular box with a diameter of 2.0 m and a depth of 1.5 m. The CD materials were added to the clay with a mix ratio of 10% by dry weight and then compacted at optimum water content (wopt) and corresponding maximum dry density (γdrymax). The testing results have indicated that the CD materials increased the ultimate bearing capacity of the clay with a range of 50–75%. Furthermore, a remarkable correlation between the results of plate loading tests and numerical simulations made by a commercial finite element software (Plaxis 2D) was observed for all mixtures tested. [ABSTRACT FROM AUTHOR]

Deep cement mixed (DCM) column-supported embankments are widely used to support embankments over soft ground. The main challenge faced by engineers when designing these embankments is to predict the deformations realistically. Although three-dimensional models are realistic, it is not efficient to carry out a large number of three-dimensional finite element analyses at the design stage to investigate the efficiency of different embankment configurations. Therefore, in practice, engineers opt for simplified modelling approaches to predict the embankment deformations. The research presented in this paper examines four different simplified models commonly used by design engineers in practice: (i) two-dimensional plane-strain with equivalent areas (EA), (ii) two-dimensional plane-strain with equivalent properties, (iii) axisymmetric unit cell and (iv) three-dimensional unit cell. Results confirm that out of the four simplified models considered, only the plane-strain EA model has the ability to capture the deformations realistically when there is a likelihood of column failure. [ABSTRACT FROM AUTHOR]

The dactyl club of stomatopods is a biological hammer used to strike on hard-shell preys. To serve its function, the club must be imparted with a high tolerance against both contact stresses and fracture. While the contact mechanics of the club has been established, fracture toughness characterization has so far remained more elusive and semi-quantitative using nanoindentation fracture methods. Here, we used microcantilever fracture specimens with a chevron-notched crack geometry to quantitatively evaluate the fracture response of the impact region of dactyl clubs. The chevron-notched geometry was selected as it minimizes surface-related artefacts due to ion milling, and further allows to carry out fracture tests on samples free of pre-cracks with stable crack propagation even for brittle materials. Both linear elastic as well as elastic-plastic fracture mechanics methods, together with finite element modelling, were employed to analyse the fracture data. We find that crack-tip plastic dissipation is the main mechanism contributing to the fracture properties of the dactyl club material. Our study also suggests that the chevron-notched crack geometry is a suitable method to quantitatively assess the fracture toughness of hard biological materials. Characterizing the fracture resistance of biomineralized structures is essential to draw their structure-properties relationships. Yet measuring the fracture properties of such materials is often hampered by their small size and irregular shape. Indentation fracture is used to circumvent these issues but does not discriminate between the elastic and elastic-plastic contributions to the fracture resistance. The dactyl club "hammer" of mantis shrimps is a biological material whose fracture properties are central to its function. A microfracture study was conducted using microcantilever specimens with chevron-notched crack geometry to assess the fracture toughness. Adopting linear elastic and elastic-plastic fracture mechanics protocols, we find that plastic dissipation is the major contribution to the fracture response of the hypermineralized impact region of the dactyl club. [Display omitted] [ABSTRACT FROM AUTHOR]

Diamond heat-spreaders for gallium nitride (GaN) devices currently depend upon a robust wafer bonding process. Bonding-free membrane methods demonstrate potential, however, chemical vapour deposition (CVD) of diamond directly onto a III-nitride (III–N) heterostructure membrane induces significant thermal stresses. In this work, these thermal stresses are investigated using an analytical approach, a numerical model and experimental validation. The thermal stresses are caused by the mismatch in the coefficient of thermal expansion (CTE) between the GaN/III-N stack, silicon (Si) and the diamond from room temperature to CVD growth temperatures. Simplified analytical wafer bow models underestimate the membrane bow for small sizes while numerical models replicate the stresses and bows with increased accuracy using temperature gradients. The largest tensile stress measured using Raman spectroscopy at room temperature was approximately 1.0 ± 0.2 GPa while surface profilometry shows membrane bows as large as 58 μm. This large bow is caused by additional stresses from the Si frame in the initial heating phase which are held in place by the diamond and highlights challenges for any device fabrication using contact lithography. However, the bow can be reduced if the membrane is pre-stressed to become flat at CVD temperatures. In this way, a sufficient platform to grow diamond on GaN/III-N structures without wafer bonding can be realised. Image 1 [ABSTRACT FROM AUTHOR]

The Cerebrospinal Fluid (CSF) can undergo shear deformations under head motions. Finite Element (FE) models, which are commonly used to simulate biomechanics of the brain, including traumatic brain injury, employ solid elements to represent the CSF. However, the limited number of elements paired with shear deformations in CSF can decrease the accuracy of their predictions. Large deformation problems can be accurately modelled using the mesh‐free Smoothed Particle Hydrodynamics (SPH) method, but there is limited previous work on using this method for modelling the CSF. Here we explored the stability and accuracy of key modelling parameters of an SPH model of the CSF when predicting relative brain/skull displacements in a simulation of an in vivo mild head impact in human. The Moving Least Squares (MLS) SPH formulation and Ogden rubber material model were found to be the most accurate and stable. The strain and strain rate in the brain differed across the SPH and FE models of CSF. The FE mesh anchored the gyri, preventing them from experiencing the level of strains seen in the in vivo brain experiments and predicted by the SPH model. Additionally, SPH showed higher levels of strains in the sulci compared to the FE model. However, tensile instability was found to be a key challenge of the SPH method, which needs to be addressed in future. Our study provides a detailed investigation of the use of SPH and shows its potential for improving the accuracy of computational models of brain biomechanics. [ABSTRACT FROM AUTHOR]

The global thermal spray coatings market was valued at USD 10.1 billion in 2019 and is expected to grow at a compound annual growth rate of 3.9% from 2020 to 2027. Carbide coatings form an essential segment of this market and provide cost-effective and environmental friendly tribological solutions for applications in aerospace, industrial gas turbine, automotive, printing, oil and gas, steel, and pulp and paper industries. Almost 23% of the world's total energy consumption originates from tribological contacts. Thermal spray WC-Co coatings provide excellent wear resistance for industrial applications in sliding and rolling contacts. Some of these applications in abrasive, sliding and erosive conditions include sink rolls in zinc pots, conveyor screws, pump housings, impeller shafts, aircraft flap tracks, cam followers and expansion joints. These coatings are considered as a replacement of the hazardous chrome plating for tribological applications. The microstructure of thermal spray coatings is however complex, and the wear mechanisms and wear rates vary significantly when compared to cemented WC-Co carbides or vapour deposition WC coatings. This paper provides an expert review of the tribological considerations that dictate the sliding wear performance of thermal spray WC-Co coatings. Structure–property relationships and failure modes are discussed to grasp the design aspects of WC-Co coatings for tribological applications. Recent developments of suspension sprayed nanocomposite coatings are compared with conventional coatings in terms of performance and failure mechanisms. The dependency of coating microstructure, binder material, carbide size, fracture toughness, post-treatment and hardness on sliding wear performance and test methodology is discussed. Semiempirical mathematical models of wear rate related to the influence of tribological test conditions and coating characteristics are analysed for sliding contacts. Finally, advances for numerical modelling of sliding wear rate are discussed. [ABSTRACT FROM AUTHOR]

This work explores the tube-to-tube joining of copper (outer) and stainless steel (inner) using electromagnetic crimping. Stand-off distance is kept constant during all the experiments. ls-dyna™ electromagnetic module, which utilizes finite element method combined with the boundary element method, is used to perform numerical simulations and the model is validated with experimentally observed thinning and radial deformation of the outer tube during electromagnetic crimping. Effect of slit of the field shaper on Lorentz force distribution is studied. It is observed that the slit of the field shaper leads to uneven radial deformation. Furthermore, a novel finite element model has been developed to predict the pull-out and compressive strength of the joint. Results are validated with the experimentally observed data. [ABSTRACT FROM AUTHOR]

Understanding bone fragility in young adult females with type 1 diabetes mellitus (T1DM) is of great clinical importance since the high fracture risk in this population remains unexplained. This study aimed to investigate bone health in young adult T1DM females by comparing relevant variables determined by dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT) at the tibia and pQCT-based finite element analysis (pQCT-FEA) between T1DM subjects (n = 21) and age-, height- and weight-matched controls (n = 63). Tibial trabecular density (lower by 7.1%; 228.8 ± 33.6 vs 246.4 ± 31.8 mg/cm3, p = 0.02) and cortical thickness (lower by 7.3%; 3.8 ± 0.5 vs 4.1 ± 0.5 cm, p = 0.03) by pQCT were significantly lower in T1DM subjects than in controls. Tibial shear stiffness by pQCT-FEA was also lower in T1DM subjects than in controls at both the 4% site (by 17.1%; 337.4 ± 75.5 vs 407.1 ± 75.4 kN/mm, p < 0.01) and 66% site (by 7.9%; 1113.0 ± 158.6 vs 1208.8 ± 161.8 kN/mm, p = 0.03). These differences remained statistically significant after adjustment for confounding factors. No difference between groups was observed in DXA-determined variables (all p ≥ 0.08), although there was a trend towards lower aBMD at the lumbar spine in T1DM subjects than in controls after adjustment for confounders (p = 0.053). These novel findings elicited using pQCT and pQCT-FEA suggest a clinically significant impact of T1DM on bone strength in young adult females with T1DM. Peripheral QCT and pQCT-FEA may provide more information than DXA alone on bone fragility in this population. Further longitudinal studies with a larger sample size are warranted to understand the evolution and causes of bone fragility in young T1DM females. [ABSTRACT FROM AUTHOR]

The current work presents a material characterization for bio composites used for automotive industrial applications. The mechanical properties are utilized in the design of components of an electric micro-car for the green innovation of automotive industry. The composite material is homogenized as equivalent orthotropic medium and its mechanical properties verified through laboratory testing. Finally a finite element model of some composite parts are analyzed by considering classical materials and innovative bio-composites. The comparison shows the valuable structural performances of the natural-based composites with respect to classical ones both in terms of cost, economical impact and mechanical performances.

The clinical effect of electroconvulsive therapy (ECT) is mediated by eliciting a generalized seizure, which is achieved by applying electrical current to the head via scalp electrodes. The anatomy of the head influences the distribution of current flow in each brain region. Here, we investigated whether individual differences in simulated local electrical field strength are associated with ECT efficacy. We modeled the electric field of 67 depressed patients receiving ECT. Patient’s T1 magnetic resonance images were segmented, conductivities were assigned to each tissue and the finite element method was used to solve for the electric field induced by the electrodes. We investigated the correlation between modelled electric field and ECT outcome using voxel-wise general linear models. The difference between bilateral (BL) and right unilateral (RUL) electrode placement was striking. Even within electrode configuration, there was substantial variability between patients. For the modeled BL placement, stronger electric field strengths appeared in the left hemisphere and part of the right temporal lobe. Importantly, a stronger electric field in the temporal lobes was associated with less optimal ECT response in patients treated with BL-ECT. No significant differences in electric field distributions were found between responders and non-responders to RUL-ECT. These results suggest that overstimulation of the temporal lobes during BL stimulation has negative consequences on treatment outcome. If replicated, individualized pre-ECT computer-modelled electric field distributions may inform the development of patient-specific ECT protocols.

This article presents a case study on the thermal assessment of a reinforced concrete (RC) foundation exposed to low temperatures. The foundation supports a 19,500 m3-capacity tank with low-temperature (−89 °C) ethane. Icing and bubbling were observed on the tank’s surface soon after it started operations. Condensation was also observed at the bottom of the 0.8-m-depth RC slab, which raised concerns about the structural condition of the concrete. This study provides details of the field and analytical investigations conducted to assess the structural condition of the foundation. Heat transfer finite element (FE) analyses were performed to examine the concrete sections subjected to low temperatures. It was found that the ethane leakage produced a low temperature on the top side of the concrete foundation of +9.7 °C. Overall, the temperatures calculated by the FE analyses were in good agreement with actual field measurements, within a ±5% accuracy. The simplified heat transfer equation for porous media used in this study was sufficiently accurate to model the effects of the ethane leakage in the concrete foundation, provided that the ambient temperature at the site is taken into account in the analysis. The results also confirm that reinforcing bars can be neglected in the thermal analysis of massive concrete slabs. The results from the field measurements and FE analyses confirmed that the structural integrity of the RC foundation was never compromised. The approaches, methods and techniques discussed in this article are deemed suitable to solve the practical and scientific challenges involved in the thermal assessment and repairs of large special structures. Accordingly, they can serve as useful reference and guidance for engineers and practitioners working in the field of forensic engineering.

The activities within a European network to develop accurate experimental and numerical methods to assess residual stresses in structural weldments are reported. The NeT Task Group 6 or NeT-TG6 project examined an Alloy 600 plate containing a three-pass slot weld made with Alloy 82 consumables. A number of identical specimens were fabricated and detailed records of the manufacturing history were kept. Parallel measurement and simulation round robins were performed. Residual stresses were measured using neutron diffraction via five different instruments. The acquired database is large enough to generate reliable mean profiles, to identify clear outliers, and to establish the systematic uncertainty associated with this non-destructive technique. NeT-TG6 gives a valuable insight into the real-world variability of diffraction-based residual stress measurements, and forms a reliable foundation against which to benchmark other measurement methods. The mean measured profiles were used to validate the accuracy achieved by the network in the prediction of residual stresses.

Sleeper spacing has been a taboo subject throughout the railway’s history. Safety concerns related to the structural integrity have been the main causes of not addressing this matter. There are no specific and clear recommendations or guidelines in relation to this matter and the distances do not go more than 0.8 m. In order to go beyond this current situation, the following research paper analyses the influence of the spacing between sleepers on the behaviour of ballasted tracks by performing a dynamic simulation with finite elements in two dimensions for different track configurations, different elements, geometries, and separations within the frame of the ODSTRACK project. The variables studied are the vertical displacements, the forces and stresses on the most important elements of the superstructure, as well as the vertical accelerations in the sleepers and the train. The values obtained from the numerical simulations were compared with the maximum permitted values according to the guidelines. To limit this distance to the most restrictive variable among those analysed, it is necessary to make important assumptions, such as the permissible values and effective support contact areas between the sleepers and the ballast. The preliminary analyses carried out shed light on a possible increment of the spacing between sleepers’ axes up to more than 0.8 m. This suggests that important savings in railways construction costs can be achieved, and they will help to develop the next stage of the ODSTRACK project.

In this work, the tensile responses of 3D woven quartz fiber silica matrix composites were experimentally and numerically investigated. The ceramic composites reinforced by 3D layer-to-layer angle interlock woven preforms were manufactured and tested under warp direction tension. A numerical method is proposed to model the mechanical response of the ceramic composites under tension. The method is based on a mesoscopic single layer unit cell for the composites, using a progressive damage analysis approach to account for damage evolution. The predicted results are compared with experimental data, and good agreement in the stress–strain response up to the ultimate tensile strength of the composites is obtained. It has been demonstrated that the proposed numerical model based on a simple single layer unit cell is both efficient and effective in characterization of the mechanical behavior of the 3D layer-to-layer woven ceramic composites.

In this work, a finite-element model was elaborated to simulate the thermomechanical behavior of 6061 aluminum alloy during friction-stir welding (FSW). It was shown that FSW-induced deformation is a two-stage process. In addition to the stirring action exerted by the rotating tool probe, the material in the near-surface area of the stir zone also experienced a secondary deformation by the shoulder edge after passage of the welding tool. Both deformation steps were found to be comparable in terms of temperature and strain, but the secondary deformation was primarily concentrated in the near-surface layer. The effects of tool rotation and translation rates on FSW temperature and strain were also systematically examined. Depending on particular welding conditions, the peak welding temperature was predicted to vary from 360 to 500 °C, while the cumulative effective strain was from 12 to 45.

The structural safety and serviceability during extreme weather, such as floods and storms, is critical. Due to global warming in the last decades, the increase in the intensity of natural disasters, i.e., flood loading and the durability of the road structures and infrastructures, is becoming critical. Bridges and structures lose their capacity because of ageing over time. On the other hand, the load intensity is another reason for the structural damage. Debris loading due to the flooding on bridges is one of the reasons for the increase in flood loading and eventually structural damage. Measuring the level of structural damage under extreme events is vital in determining the vulnerability and resilience of structures during a disaster. A damage index (DI) can be defined as a measurement tool for the levels of structural damage. Oftentimes, damage indices are developed to measure the deterioration of the system under earthquake loading. Little work has been published on damage indices (DIs) under flood loading, where a uniform pressure is applied to a structure. This paper presents a comprehensive review of DIs published in the literature and compares two approaches to assess the system’s damage utilising finite element methodologies. The structure model developed in the ABAQUS software package is used to predict the failure of a concrete component under applied lateral loading. The model is validated using published experimental work. The model is verified, and then it is used to compute the damage indicators using two primary techniques, including a deflection-based method and an energy loss-based approach. Using the two offered DIs, the change in damage levels is displayed underwater flow uniform loading. A comparison of the two methods is conducted. In this paper, differences between the two concepts are analysed and presented.