Large Elements Research Articles

Failure criteria in crashworthiness analysis of ship collision and grounding using FEA: Milestone and development

This study presents reviews of the failure criteria to capture the resulting response due to the catastrophe of ship collision and grounding using the finite element. Researchers have introduced several failure criteria, for instance, the DNV RP-C204 criterion, Germanischer Lloyd criterion, Peschmann, RiceTracey and Cockcroft-Latham (RTCL), Bressan-Williams-Hill (BWH) instability criterion, and Liu criterion. As in the mathematical formula, each criterion has a difference. The choice of failure criteria will depend on the simulation's specific requirements and the analysis's goals. Liu's criterion can be used to evaluate the failure of materials in ship collision simulations, for example, when large element sizes (i.e., 20 mm) are considered in the simulation.

A Study on Customer Satisfaction towards Mahindra Scorpio

This looks at goals to discover the factors that affect patron buying selections for the Mahindra Scorpio SUV. A survey became carried out amongst a sample of potential shoppers and current owners of the Scorpio, and records were analyzed using descriptive and inferential records. The effects indicate that the most essential elements that impact buying choices are product capabilities, logo photo, price, and social effect. additionally, the observer located that the perceived greatness and reliability of the Scorpio are the largest elements that make contributions to brand loyalty among current proprietors. The findings of this examination have real implications for Mahindra & Mahindra, as they can use this data to higher apprehend the needs and possibilities of their target audience and tailor their advertising strategies for this reason.

Dynamic installation of torpedo anchors in slightly overconsolidated clay-overlaying-sand deposit

Torpedo anchor installation involves uncertain design and construction parameters, especially in layered soil deposits. Large deformation finite element and coupled Eulerian–Lagrangian (LDFE/CEL) analyses are performed in this study to elucidate the dynamic installation of torpedo anchors in an over consolidated clay-overlaying-sand deposit. The parametric analysis is conducted after model verification to explore the effect of upper clay layer thickness, anchor impact velocity, anchor submerged weight, soil properties and anchor geometric dimensions. The soil failure patterns and dynamic installation behaviour in the clay-overlaying-sand soil deposit are found to differ substantially from those in single-layer clay and sand deposits, which exhibit a squeezing flow pattern at the clay-sand soil layer interface. As the demarcation of the two velocity phases during the anchor penetration process (acceleration and deceleration phases) falls below the interface of two soil layers, the contribution of the internal friction angle of sand to the anchor final penetration depth exceeds that of the clay undrained shear strength. Based on intensive modelling data, an empirical method for predicting the anchor penetration depth in single and layered soil deposits is derived for engineering applications.

Coefficient of consolidation measured by cone penetration tests in overconsolidated cohesive soils

In offshore investigations, the dissipation test following penetration of a piezocone is extensively used in cohesive soils to obtain the consolidation behavior. Compared with that in normally consolidated soil, the dissipation response in overconsolidated silty clay or silt is more complicated, since the distribution of initial excess pore pressures and the subsequent dissipation depend on the overconsolidation ratio and partially drained conditions simultaneously. Large deformation finite element analyses within the formula of effective stress are carried out, where the large-amplitude displacement of piezocone under different drainage conditions and the dissipation are simulated. The large deformation approach is validated against centrifuge tests and cavity expansion solutions. A unique curve is established to estimate the nominal initial pore pressure at the shoulder of piezocone in overconsolidated soil, against a new normalized penetration rate. The curve is applicable to piezocone penetrations under different drainage conditions. The previous definition of operative coefficient of consolidation can be used to interpret the dissipation curves in overconsolidated soils as well. A unique backbone curve is proposed for overconsolidated soils to quantify the relationship between the operative and conventional coefficients of consolidation. A procedure is thus developed to determine in-situ conventional coefficient of consolidation of overconsolidated silty soils.

Transcranial 3D ultrasound localization microscopy using a large element matrix array with a multi-lens diffracting layer: an in vitro study

Objective. Early diagnosis and acute knowledge of cerebral disease require to map the microflows of the whole brain. Recently, ultrasound localization microscopy (ULM) was applied to map and quantify blood microflows in 2D in the brain of adult patients down to the micron scale. Whole brain 3D clinical ULM remains challenging due to the transcranial energy loss which reduces significantly the imaging sensitivity. Approach. Large aperture probes with a large surface can increase both the field of view and sensitivity. However, a large active surface implies thousands of acoustic elements, which limits clinical translation. In a previous simulation study, we developed a new probe concept combining a limited number of elements and a large aperture. It is based on large elements, to increase sensitivity, and a multi-lens diffracting layer to improve the focusing quality. In this study, a 16 elements prototype, driven at 1 MHz frequency, was made and in vitro experiments were performed to validate the imaging capabilities of this new probe concept. Main results. First, pressure fields emitted from a large single transducer element without and with diverging lens were compared. Low directivity was measured for the large element with the diverging lens while maintaining high transmit pressure. The focusing quality of 4 × 3cm matrix arrays of 16 elements without/with lenses were compared. In vitro experiments in a water tank and through a human skull were achieved to localize and track microbubbles in tubes. Significance. ULM was achieved demonstrating the strong potential of multi-lens diffracting layer to enable microcirculation assessment over a large field of view through the bones.

The Combined Bearing Capacities of Anchor Chain Segment by Considering Its Actual Geometry and Roughness

The soil resistances along the embedded ground chain affect the pull-out capacity of anchor as they determine the magnitude and direction of tension at the padeye. To facilitate analyses, the chain was usually simplified as a cylindrical line. The chain segment with actual geometry, buried deeply in clayey soil, is studied using a large deformation finite element approach to overcome severe distortion of soil elements around the chain. The uniaxial resistances obtained by the large deformation analyses are verified by comparison with the existing model tests and simplified solutions, followed by presentation of the yield envelope against combined loading. Both the probe test and swipe test are used to form the yield envelopes, and their results have good consistency. The influence of roughness of chain–soil interface on the soil resistances is quantified as well. It is found that the envelope of the chain segment with actual geometry is smaller than that against the simplified cylindrical shape; therefore, the most convenient design may not be the safest option.

Bayesian structural parameter identification from ambient vibration in cultural heritage buildings: The case of the San Jerónimo monastery in Granada, Spain

The deterioration of Cultural Heritage assets caused by the natural hazards is a pressing issue in many countries. Therefore, reliable models based on the large-scale structural response of the assets is key to assess their resilience. However, reliable models such as large and detailed Finite Element (FE) models, require a large number of data and input parameters. This paper proposes a Bayesian learning approach to identify the main parameters of a FE model with quantified uncertainty based on ambient vibration data. As a novelty when compared with other Bayesian structural parameter identification methods from ambient vibration data, here the likelihood function is formulated in a principled way considering information from both frequencies and modes using a probabilistic version of the Modal Assurance Criterion for the modes. This method is embedded into a parameterised computational model to automate the simulation process, and a real case study for a sixteenth century heritage building in Granada (Spain) is presented. The results show the suitability and effectiveness of the proposed Bayesian approach in identifying the most plausible values of the uncertain model parameters in a rigorous probabilistic way, but also in obtaining the modelled frequencies and the modal assurance criterion values with quantified uncertainty.

Spatial and temporal averaging in the homogenisation of the elastodynamic response of periodic laminates

This paper suggests a methodology to obtain homogenised material properties from a transient dynamic numerical model. The standard Hill–Mandel Principle, based on spatial averages, is extended with time averaging. Thus, in addition to a sufficiently large Representative Volume Element (RVE) to carry out the averaging in space, a sufficiently large time window is required to carry out the time averaging. The space–time averaging procedure is validated for a periodic laminate bar subjected to a variety of boundary conditions, impedance contrasts and loading conditions. The homogenised results converge to the analytical solutions and confirm that having a higher impedance contrast between laminate components requires not only larger RVE sizes but also longer time averaging windows. The most efficient macroscopic approximation is obtained by a balanced increase in RVE size and time averaging window.

Enhanced photovoltaic properties of halide perovskites due to multi-centered X–B–X bonding and p–p orbital coupling

Halide perovskites ABX3 are valuable photovoltaic and light-emitting materials due to their favorable optical properties of a direct bandgap and strong optical absorption just above the bandgap. Here, we show that these properties arise mainly from multi-centered X-B-X bonding and B-p X-p coupling. A bonding analysis finds that B–X bonds have shared electrons intermediate between that of ionic and covalent bonding. The B cation site p orbital interacts with left and right lobes of X-p orbitals, forming a special three-centered, two-electron X–B–X bond. This bonding mechanism is shown to give rise to unusually large optical matrix elements, especially in the visible spectrum, with the normalized matrix elements twice that of typical two-center bonds and transition probabilities four times larger. These cause a very sharp increase in optical absorption just above the gap. Experimental values of Urbach energies are found to be small, even if perovskites have disordered structures. The broad valence and conduction bands of the linearly aligned p orbitals cause dispersive band extrema, with small effective masses of both carriers at the R point, indicating a high carrier mobility.

Preliminary assessment of potential pile tip damage and extrusion buckling

Pile tip damage has become of particular concern for the offshore wind industry due to the extensive use of large-diameter, thin-walled piles for monopiles and jacket structures. The potential for damage has increased in recent developments due to the occurrence of embedded boulders within the seabed sediments (e.g. glacial tills) or partially weathered soft rocks (e.g. limestones, chalk). To assess the risk of pile tip damage, this paper presents a simple schematic approach to estimate: i) whether pile tip damage might occur following impact with embedded boulders; and ii) what soil strength (e.g. as reflected in the cone tip resistance qc) might initiate progressive distortion of an initial minor dent (extrusion buckling). The methodology was developed based on results of centrifuge model tests and large displacement finite element analysis, encompassing: i) undamaged thin-walled piles installed through embedded layers of different sized boulders; and ii) initially ‘pre-dented’ piles driven through homogeneous sand triggering progressive distortion. Numerical analysis was used to develop predictive guidelines for conditions that might cause significant pile tip damage. The guidelines were validated by comparison with results from model tests and also through well documented field cases where extrusion buckling occurred. The paper provides guidance for choosing the critical parameters involved in the calculation processes to enable direct application in design, allowing assessment of whether more detailed investigation and analysis should be undertaken.

Reduced Order Modeling of Nonlinear Vibrating Multiphysics Microstructures with Deep Learning-Based Approaches

Micro-electro-mechanical-systems are complex structures, often involving nonlinearites of geometric and multiphysics nature, that are used as sensors and actuators in countless applications. Starting from full-order representations, we apply deep learning techniques to generate accurate, efficient, and real-time reduced order models to be used for the simulation and optimization of higher-level complex systems. We extensively test the reliability of the proposed procedures on micromirrors, arches, and gyroscopes, as well as displaying intricate dynamical evolutions such as internal resonances. In particular, we discuss the accuracy of the deep learning technique and its ability to replicate and converge to the invariant manifolds predicted using the recently developed direct parametrization approach that allows the extraction of the nonlinear normal modes of large finite element models. Finally, by addressing an electromechanical gyroscope, we show that the non-intrusive deep learning approach generalizes easily to complex multiphysics problems.

Growth of REBa2Cu3O x single-crystal whiskers utilizing the concept of high-entropy alloys

Single-crystal whiskers of REBa2Cu3O x (RE-123, RE: rare Earth element) cuprate superconductors were successfully grown using Te-doped precursors utilizing the concept of high-entropy-alloys at the RE site. The obtained whiskers were 0.5–1.0 mm in length with approximately 10 μm thickness. The width of the flat surface, which corresponds to the ab-plane, was 10–50 μm. The RE site of the grown whiskers could be easily substituted by large ionic radius RE elements (Gd, Dy and Ho). Substitution with small ionic radius RE elements (Tm, Yb and Lu) resulted in the opposite trend. The superconducting transition temperature and superconducting anisotropy of the grown RE-123 whiskers were 89–93 K and 6–10, respectively. The mixed entropy at the RE site in the RE-123 whiskers did not affect the superconducting transition temperature and superconducting anisotropy.

Evaluating numerical techniques with HPC systems in predicting vibratory responses of large finite element models

Finite element (FE) analyses have been widely used to support design optimizations in various disciplines to improve performance and possibly save material, cost, and schedule. As computational resources (i.e., CPU, memory, storage, and accelerator) are getting more powerful and cost effective, the complexity and model sizes of numerical models are greatly increasing to capture geometry details and features of the design. Correspondingly, the computational time for complex and large FE models are significantly growing. Traditional brute-force approach is not quickly enough to support design iterations. In this presentation, various numerical techniques are investigated and exercised in the DoD High Performance Computing systems to identify their advantages and limitations in conducting large FE analyses. Those techniques include utilization of GPGPU, direct versus iterative solvers, approximation of frequency sweep, etc. As a benchmark case, frequency response functions of a flat plate with viscoelastic material is exercised at the DoD HPC systems to examine the numerical techniques' impacts.

Geological Significance of Neoproterozoic Intrusive Rocks in the South Section of the Ailaoshan Orogenic Belt, SW China: Insights from Petrology, Geochemistry, and Geochronology

The Ailaoshan orogenic belt is one of the most significant orogenic belts in the southeastern margin of the Qinghai–Tibet Plateau. The widely developed magmatic rocks in this belt preserve the multi-stage tectonic evolution records of the South China Plate. As an important response to the Rodinia breakup tectonic event, the study of Neoproterozoic magmatic rocks in the area is of great significance for reconstructing the Neoproterozoic tectonic process of the Ailaoshan orogenic belt and the tectonic evolution of the South China Plate. Petrology, geochemistry, zircon U-Pb, and Lu-Hf isotopes of the Daping pluton in the Ailaoshan orogenic belt are studied in this paper. The Daping pluton is mainly divided into gabbros and granites. Gabbros and granites belong to the sub-alkaline series, which are relatively enriched in large ion lithophilic elements and depleted in high-field strength elements. The ΣREE contents of the gabbro are low with enrichment in LREEs and depletion in HREEs, and the degree of differentiation of light and heavy rare earth is low, with positive δEu and weak negative δCe anomalies. The ΣREE contents of the granite are low with enrichment in LREEs and depletion in HREEs, and the degree of light and heavy rare earth differentiation is high, with medium–weak negative δEu and weak positive δCe anomalies, suggesting an A2-type granite with A1-A2 transition characteristics. The weighted average age of the gabbro is 816.1 ± 4.1 Ma (MSWD = 0.11), with zircon εHf(t) values of −7.5–5.5. The magma source is a mixture of an ancient crust source and a new mantle source; the weighted average age of the syenogranite is 783.7 ± 8.1 Ma (MSWD = 1.4), with zircon εHf(t) values of −4.3–0.4. The magma source is mainly ancient crustal material (Ailaoshan Group), mixed with a small amount of mantle-derived material; the weighted average age of the monzogranite is 754.8 ± 6.1 Ma (MSWD = 3.0), with positive zircon εHf(t) values of 1.65–10.36. The magma source is a mixture of a large number of mantle-derived materials and a small number of crust-derived materials (Ailaoshan Group). The Daping pluton was formed in the transitional tectonic environment from post-collision to intraplate continental margin rift, corresponding to the Rodinia breakup process in the western margin of the South China Plate.

Shape Optimization Algorithms for Fluid Dynamics Applications

AbstractIn this work we present a comparison between shape optimization algorithms in different vector spaces. The main goal is to optimize the surface of an object with respect to a physical quantity. The main focus is on applications that require large element deformations as part of the optimization process, as for instance the removal and creation of geometric singularities such as edges and corners. The algorithms take into account the prevention of element degeneracy and overlapping, for instance by enforcing inequality constraints. For this purpose, an approach in the Hilbert space is compared to another in Banach spaces. The former is based on a nonlinear extension equation, whereas the p‐Laplace operator is used in the latter. Computational results are presented in the context of fluid dynamics applications, where the contour of an object is optimized with respect to the energy dissipation.

The behavior of ball penetrometer in soft-over-stiff soil deposits

Proper understanding of the ball penetration behavior under centrifuge condition is important for accurate soil property determination. In this study, large deformation finite element (LDFE) analyses are conducted to investigate the scale effect of ball penetrometer on its behavior in clay-over-sand deposit in centrifuge tests. The finite element model of this study is validated against previous theoretical solutions and available centrifuge test data with good agreement. Parametric studies are then carried out to explore the effects of potential factors, including the layer thickness ratio, the shaft-ball area ratio, the undrained shear strength of clay, and the relative density of sand. The results indicate that the soil failure mechanisms can be divided into three stages: i) shallow embedment stage, ii) cavity evolution stage, and iii) full-flow stage. The penetration resistance profiles in centrifuge tests can be better quantified, which can provide more accurate shear strength interpretation for the top clay.

Improving the Energy Efficiency of Equipment for the Impregnation of Roof Trusses—Modeling and Practical Implementation

The impregnation of elements made of wood is one of the most important stages of their maintenance and the modification of their parameters. Incorrectly prepared material is sensitive to moisture, fungi, algae or weather conditions. In the case of large wooden elements or ready-made installations, impregnation is often performed not indoors, but outdoors. Despite the obvious advantages, this solution also has a number of disadvantages. One of them is the long duration of the impregnation process, as well as the variability in the process parameters along with changing weather conditions. In addition, the final material properties may differ not only from batch to batch, but also within the batch. In order to eliminate these problems, the equipment for wood impregnation was modernized. As part of the work, models of installation elements were made, a computer simulation was performed, and the necessary design calculations were carried out. The work will be crowned with the practical implementation of the proposed solutions in test equipment and the verification of design assumptions. The effect of the modernization of the system was a significant shortening of the impregnation process, as well the ability to obtain a final product of higher quality.

DMD maskless digital lithography based on stepwise rotary stitching

Diffractive optical elements (DOEs) with rotationally symmetric phase distribution are mainly produced by laser direct writing technique in a polar coordinate system, which has slow processing speed and limited fabrication area. In this paper, we propose a digital micro-mirror device maskless digital lithography technique based on stepwise rotary stitching. DOEs with rotationally symmetric phase distribution are fabricated by exposure of stitching units and rotation of rotary tables. Then, different stitching units are designed to compensate for the errors caused by the accuracy of the rotary table. Finally, the high quality DOEs are produced by the double-exposure method. When increasing the fabrication area, significantly improves the saw-tooth of the lithography pattern edge while reducing misalignment and overlap of stitching caused by residual errors. The diameter of the fabricated Fresnel zone plate was increased from 5.25 mm to 11.40 mm, and the fabrication area was 4.72 times larger than conventional lithography. The stitching error of 18.95 μm has been eliminated after optimization, and the pixelization has been smoothed. The diffraction results show that the method not only can produce large area and high-quality diffraction elements but also greatly reduce the processing cost.

The design of multi-wavelength confocal diffractive optical element based on set operation

A method suitable for the design of large aperture multi-wavelength confocal diffractive optical element (DOE) was proposed. The method is based on set operation for microstructures. As examples, different multi-wavelength confocal DOEs with aperture of 20 mm were designed. The results of the numerical simulations show that the confocal DOEs achieved diffraction-limited focusing performance at all design wavelengths, but the diffraction efficiencies were lower than the ideal DOEs. For experimental verification, one three-wavelength confocal DOE with focal length of 200 mm was fabricated and tested. The optimum full width at half maximum (FWHM) is preferably 1.067 times of the diffraction limit and the highest optical imaging solution reaches 94.6% of the diffraction limit. Both the simulation results and the experimental results verify the validity of this method for designing multi-wavelength confocal DOE. The presented work may find applications in large-aperture multi-wavelength laser communication, wide-spectrum diffractive telescopes, and high-precision multi-wavelength Computer generated holography (CGH).

Improving the estimation of soil spatial variability by considering transformation uncertainty based on LDRFE analysis

Transformation uncertainty is an imperative consideration in the process of transforming measurement data to desired design parameters in geotechnical engineering. In the reliability-based design framework, an improved understanding of transformation uncertainty is expected to produce more appropriate design of geotechnical structures. This paper quantifies the site-specific and aleatory transformation uncertainty and investigates how to consider it in estimation of random field parameters through numerically simulated cone penetration tests in spatially variable clay by means of large deformation random finite element analysis. The transformation uncertainty of a transformation model is modelled as a random field. Random field parameters of transformation uncertainty, including the standard deviation, scale of fluctuation and sample path smoothness, are estimated using maximum likelihood estimation along with Whittle-Matérn autocorrelation function model. Random field parameters of predicted shear strength with and without considering transformation uncertainty are thereafter compared with those random field parameters of actual shear strength. Results show that the consideration of transformation uncertainty in the transformation model can considerably improve the prediction accuracy of random field parameters. It is important to consider the spatial correlation structure of transformation uncertainty. This study offers a simple-to-use framework to estimate random field parameters considering the site-specific and aleatory transformation uncertainty.