Energy-based Method Research Articles

Guided wave‐based cable damage detection using wave energy transmission and reflection

Health monitoring of cables in civil engineering structures is a great challenge, because their integrity directly affects the safety of the whole structure. A magnetostrictive (MS) transducer-based guided wave method for cable damage detection is presented in this study. A wave energy-based method is proposed for damage localization and severity assessment. The wave energy transmission coefficient at the damage location is presented as a measure for the damage condition. Firstly, the wave dispersion properties were analyzed on a steel strand with seven helical wires using a semi-analytical finite element (SAFE) method. Then, the selection of exciting frequency and design of the MS transducer were carried out based on the SAFE analysis results. Numerical and experimental studies were performed on multiple cases of wire breakage and corrosion using the pitch-catch method. Time-of-flight information on the wave packets reflected from the damages was used for damage localizations, while wavelet coefficients were used to accurately analyze wave energy transmission and reflection. It has been found that the damage locations and damage conditions can be determined accurately using the proposed method.

Energy-based liquefaction evaluation for induced strain and surface settlement ― evaluation steps and case studies ―

Energy-Based Method (EBM) for liquefaction potential evaluation was previously developed by the present author, wherein the total demand compared with the capacity at a site can be given by earthquake upward SH-wave energy. To make the most of the EBM with the energy demand given, evaluations are added here to calculate the liquefaction-induced strain and associated soil settlement by introducing a simple assumption that the wave energy is equally shared among layers firstly determined as liquefiable. By applying this to a uniform sand layer as well as case history sites, the additional liquefaction evaluation tends to calculate much higher shear strains than 7.5% corresponding to initial liquefaction in a smaller number of layers than in the first stage. Furthermore, soil subsidence calculated using volumetric strain versus shear strain correlations for intact soils is found agreeable with actual performance during earthquakes. Thus, the two-stage EBM of liquefaction evaluation can practically predict not only liquefaction potential but also induced strain and surface settlement without resorting to nonlinear numerical analyses.

A strain energy-based homogenization method for 2-D and 3-D cellular materials using the micropolar elasticity theory

A new strain energy-based method for homogenization of 2-D and 3-D cellular materials is developed using an extended version of Hill’s Lemma for the non-Cauchy continuum satisfying the micropolar elasticity theory. Both kinematic and mixed boundary conditions (BCs) that obey the Hill-Mandel condition are identified. The newly proposed method requires that the nodal equilibrium equations be explicitly satisfied at all boundary and interior nodes, unlike the existing approach which does not enforce the equilibrium conditions at interior nodes. For 2-D cellular materials, it is shown that purely kinematic BCs (with prescribed displacement and micro-rotation vectors) and mixed BCs (with prescribed couple stress traction and displacement vectors) can both be used for homogenization, and periodic constraints can be readily accommodated in the former. For 3-D cellular materials, it is demonstrated that mixed BCs (with prescribed couple stress traction and displacement vectors) enable the homogenization satisfying the Hill-Mandel condition. Two sample cases of homogenization of cellular materials are studied by applying the new method – one for a 2-D lattice structure and the other for a 3-D pentamode material. For the 2-D lattice material, the effective classical and micropolar stiffness tensors are obtained using purely kinematic BCs (with and without periodic constraints) and mixed BCs. The closed-form expressions of the effective stiffness tensor components derived here are compared to those given by the existing strain energy-based homogenization method and are seen to be more accurate. For the 3-D pentamode material, mixed BCs are employed in the homogenization, and the effective stiffness tensor components are obtained in closed-form expressions for the first time. The numerical results for the pentamode material given by these analytical formulas are found to agree well with those provided by a finite element model constructed using COMSOL.

A Multistage Damage Detection Approach Using Graph Theory and Water Strider Algorithm

Structures usually suffer from natural or artificial damages that might result in shortening their service life and even triggering their collapse. Therefore, vibrational damage detection methods, as cost-effective and nondestructive techniques, are widely investigated by researchers. In the present paper, the modal-strain energy-based two-stage method is enhanced, and a graph-theoretic hierarchical (GHM) method is proposed, which takes advantage of the modal strain energy-based index (MSEBI) and overcomes its potential drawbacks by identifying all damaged elements. This method assigns orders and allocates the computational resources to elements according to the MSEBI as well as the connections represented by a graph model. The water strider algorithm (WSA) is also utilized as an efficient new optimizer, and its results are compared with those of some other well-known algorithms. Several examples are used to substantiate the results and performance of the new GHM framework, showing that the new method outperforms the general classic method, especially when it is combined with the WSA optimizer.

Topology optimisation for isotropic mechanical metamaterials considering material uncertainties

Isotropic materials are widely used because they retain their properties regardless of the measurement directions. However, their mechanical properties tend to deteriorate owing to disturbances in the base material parameters. This study, for the first time, systematically investigates multiple isotropic materials by considering material uncertainties with respect to the elastic modulus and Poisson's ratio. A smooth bi-directional evolutionary topology optimisation method, is employed to identify optimal topological configurations for material microstructures, macroscopic equivalent properties of the microstructures are evaluated via the comprehensible energy-based homogenisation method. A non-intrusive polynomial chaos expansion model is employed to implicitly quantify uncertainties in the base material subject to Gaussian distributions. Additionally, both the expectations and standard variations in extreme properties are considered as the objective function, and a measurement index is defined to determine whether the designed microstructures are isotropic. Lastly, the deterministic and uncertain cases for numerical examples are compared to demonstrate the efficiency of the proposed method.

An Optimization Method for Thermal Convex Deformation of Machine Tool's Guideway Based on the Conservation of Energy

With the improvement of machining accuracy and efficiency, heat generation of guideway becomes the crucial problem which will cause thermal convex deformation. Thermal convex deformation of guideway which accounts for about 22.7% of the total errors is one of the main factors affecting the machining accuracy of machine tool. A conservation of energy-based optimization method is proposed to balance the temperature field and reduce the thermal convex deformation. The main strategy of this method is to transfer the heat from high temperature regions to the lower temperature regions through a heat transfer system. The structure and contact area of the heat transfer system are determined according to the output and input heat ratio of the guideway. The simulation and experimental results show that the temperature field of the guideway is more uniform after optimized, the thermal convex deformation is reduced about 50%, it is of great significance to reduce the thermal convex deformation of the guideway and improve the machining accuracy of machine tool.

A High Intensity Focused Ultrasound System for Veterinary Oncology Applications.

Background:Magnetic resonance-guided focused ultrasound surgery is an incisionless energy-based thermal method that is used for ablating tumors in the veterinary clinic.Aims and Objectives:In this article we describe a prototype of a veterinary system compatible with magnetic resonance imaging intended for small-to-medium-sized companion animals that was developed and tested in vivo in adult rabbits.Methods:Real-time monitoring of the ablation during the experiment was possible with MR thermometry. Experiments involved thermal monitoring of sonications applied in the thigh of the rabbits. A 38-mm diameter transducer operating at 2.6 MHz was used with a 60-mm-focal length. The robotic system employed 3 linear axes and one angular axis. For this study, only X and Y axis were enabled. Due to the target size limitations, motion in Z and Θ was not needed. The functionality of the positioning device was evaluated by means of MR thermometry, demonstrating sufficient heating and accurate motion in both axes of operation.Results:The postmortem findings confirm the ability of the system to induce thermal ablations in vivo in the absence of adverse effects.Conclusions:The device is a reliable and affordable solution for companion animal hospitals, offering and additional tool for the veterinary oncology society.

An effective design method for mechanical metamaterials with negative Poisson’s ratios

This paper proposes an effective method for the design of mechanical metamaterials by combining the parametric level set method (PLSM) with the energy-based homogenisation method (EBHM), where the ...

Nucleation of Twinning Dislocation Loop in Pt: A Computational Approach

Twinning plays a critical part in the plastic deformation of the materials and the strengthening mechanisms and is hence considered as one of the most prevalent deformation mechanisms in metals. Because to the high stacking fault energy of the fcc metals like Al, Pd, and Pt, the extended dislocations are believed to be energetically favored over isolated partials, thereby rendering deformation twinning unfeasible. Nevertheless, some recent experimental researches have confirmed a potential deformation twinning pathway in nanocrystalline platinum. This alternate-shear mechanism has a much lower energy barrier than the usual layer-by-layer twinning. We utilize computations involving atomistic calculations and continuum modeling in this study to examine the genesis of deformation twins in Pt. Atomistic simulations provides the generalized planer fault energy using an EAM (embedded-atom-model) potential. Moreover, a potential energy-based method, namely; a nudged-elastic band (chain of states) has been used to compute the activation energy barrier for the nucleation of the twinning dislocation loop in the alternate-shear model. The critical stress needed for the nucleation of the twinning dislocation loop in platinum is estimated using some of the parameters acquired from atomistic calculations and using them as fitting parameters in the continuum model. The minimum-energy path between the two end states can be identified using this methodology. Through the unusual alternate-shear approach, the results provide a rudimentary but essential dislocationbased perspective of the occurrence of deformation twins in fcc metals.

Connecting dynamic reweighting Algorithms: Derivation of the dynamic reweighting family tree.

Thermally driven processes of molecular systems include transitions of energy barriers on the microsecond timescales and higher. Sufficient sampling of such processes with molecular dynamics simulations is challenging and often requires accelerating slow transitions using external biasing potentials. Different dynamic reweighting algorithms have been proposed in the past few years to recover the unbiased kinetics from biased systems. However, it remains an open question if and how these dynamic reweighting approaches are connected. In this work, we establish the link between the two main reweighting types, i.e., path-based and energy-based reweighting. We derive a path-based correction factor for the energy-based dynamic histogram analysis method, thus connecting the previously separate reweighting types. We show that the correction factor can be used to combine the advantages of path-based and energy-based reweighting algorithms: it is integrator independent, more robust, and at the same time able to reweight time-dependent biases. We can furthermore demonstrate the relationship between two independently derived path-based reweighting algorithms. Our theoretical findings are verified on a one-dimensional four-well system. By connecting different dynamic reweighting algorithms, this work helps to clarify the strengths and limitations of the different methods and enables a more robust usage of the combined types.

A general multi-scale topology optimisation method for lightweight lattice structures obtained through additive manufacturing technology

A general framework for the multi-scale topology optimisation (TO) of lattice structures (LSs) is presented in this work. The proposed method involves: Non-Uniform Rational Basis Spline (NURBS) hyper-surfaces to represent the pseudo-density field describing the LS representative volume element (RVE) topology, the Solid Isotropic Material with Penalisation (SIMP) approach and the strain energy-based homogenisation method (SEHM) to perform the scale transition. The main contributions of this work are essentially three. Firstly, physical responses are defined at different scales and their gradient is evaluated by exploiting the NURBS local support property and the Dirichlet’s problem properties at the RVE scale. Secondly, the computational efficiency of the SEHM based on elements strain energy over that of the SEHM based on elements averaged stresses is rigorously proven. Finally, to show the effectiveness of the method, numerical analyses are conducted on 2D and 3D problems. A sensitivity analysis of the optimised topology to the integer parameters of the NURBS hyper-surface is carried out. Moreover, the influence of the initial guess and of the macroscopic loading condition on the RVE optimised topology is investigated. The minimum length-scale requirement is also integrated into the problem formulation as a manufacturing constraint.

Integrating genome sequence and structural data for statistical learning to predict transcription factor binding sites.

We report an approach to predict DNA specificity of the tetracycline repressor (TetR) family transcription regulators (TFRs). First, a genome sequence-based method was streamlined with quantitative P-values defined to filter out reliable predictions. Then, a framework was introduced to incorporate structural data and to train a statistical energy function to score the pairing between TFR and TFR binding site (TFBS) based on sequences. The predictions benchmarked against experiments, TFBSs for 29 out of 30 TFRs were correctly predicted by either the genome sequence-based or the statistical energy-based method. Using P-values or Z-scores as indicators, we estimate that 59.6% of TFRs are covered with relatively reliable predictions by at least one of the two methods, while only 28.7% are covered by the genome sequence-based method alone. Our approach predicts a large number of new TFBs which cannot be correctly retrieved from public databases such as FootprintDB. High-throughput experimental assays suggest that the statistical energy can model the TFBSs of a significant number of TFRs reliably. Thus the energy function may be applied to explore for new TFBSs in respective genomes. It is possible to extend our approach to other transcriptional factor families with sufficient structural information.

Field experiment using transient energy method to locate a single-phase to ground fault

Distribution networks in China and several other countries are predominantly neutral inefficiently grounding systems (NIGSs), and more than 80% of the faults in distribution networks are single-phase-to-ground (SPG) faults. Because of the weak fault current and imperfect monitoring equipment configurations, methods used to determine the faulty line sections with SPG faults in NIGSs are ineffective. The development and application of distribution-level phasor measurement units (PMUs) provide further comprehensive fault information for fault diagnosis in a distribution network. When an SPG fault occurs, the transient energy of the faulted line section tends to be higher than the sum of the transient energies of other line sections. In this regard, transient energy-based fault location algorithms appear to be a promising resolution. In this study, a field test plan was designed and implemented for a 10 kV distribution network. The test results demonstrate the effectiveness of the transient energy-based SPG location method in practical distribution networks.

Modeling of force and temperature in cutting of particle reinforced metal matrix composites considering particle effects

• An analytical force model for PRMMCs is established considering particle effects. • An analytical model of tool face temperature of PRMMCs is developed with particle effects. • Predictions considering particle effects accurately estimate experimental results. • Complex variations of force and temperature is strongly influenced by reinforced particles. Particle reinforced metal matrix composites (PRMMCs) machining is considerably difficult owing to the significant influence of hard particles on the force and temperature during cutting. To provide an insight for understanding the effect of particles on the force and temperature, this paper aimed at modeling of the force and temperature affected by reinforced particles in PRMMCs cutting. Firstly, an analytical force model of PRMMCs was established based on a dynamic constitutive model considering particle effects. The influences of hard particles on the shear strength in the shear zone were considered in the dynamic constitutive model, including particle strengthening effect and particle damage. The particle debonding and fracture near the cutting edge were additionally considered in the force model, based on an energy-based method. Then, an analytical model of tool face temperature with particle effects was developed by considering the characteristic of the heat generated in PRMMCs cutting. To predict force and temperature in PRMMCs cutting, a combined prediction method, which used an improved three-phase friction model, was proposed to integrate the force model with the temperature model. The predicted force and temperature in cutting of various PRMMCs under different cutting conditions were validated through a comparison with experimental results. The comparison results showed that the force and temperature predicted by the analytical models considering particle effects were found to be more accurate than the analytical models without considering particle effects. Finally, comprehensive investigation of the effect of reinforced particles on the cutting force and temperature was explored, based on the modeling of the force and temperature in PRMMCs cutting. The results indicated that the complex variation of forces with particle content and size mainly depended on the shear strength, which was strongly affected by particle damage. A decrease in tool face temperature with increasing particle content was caused by a reduction in the plastic shear energy of the metal matrix.

Energy-Based Novel Quantifiable Sustainability Value Assessment Method for Machining Processes

Sustainability assessments of cooling/lubrication-assisted advanced machining processes has been demanded by environment control agencies because it is an effective management tool for improving process sustainability. To achieve an effective and efficient sustainability evolution of machining processes, there is a need to develop a new method that can incorporate qualitative indicators to create a quantifiable value. In the present research work, a novel quantifiable sustainability value assessment method was proposed to provide performance quantification of the existing sustainability assessment methods. The proposed method consists of three steps: establishing sustainable guidelines and identifying new indicators, data acquisition, and developing an algorithm, which creates the Overall Performance Assessment Indicator (OPAI) from the sustainability assessment method. In the proposed algorithm, initially, both quantitative and qualitative sustainability indicators are normalized. After weight assignment and aggregation, the OPAI is obtained. The developed algorithm was validated from three literature case studies, and optimal cutting parameters were obtained. The present methodology provides effective guidelines for a machinist to enhance process performance and achieve process optimization. The study also offers a relationship between sustainable and machining metrics for the support of industrial sustainability.

Pulse Ranging Method Based on Active Virtual Time Reversal in Underwater Multi-Path Channel

Aiming at improving the accuracy of pulse ranging measurement in underwater multi-path environment, this paper proposes a novel pulse ranging algorithm based on active virtual time reversal (AVTR). By using the focusing characteristics of AVTR, the received signal can be focused at the receiving end, which eliminates the negative influence of multiple pseudo-peaks. In order to extract the received signal, we propose an energy-based adaptive windowed method which preserves the signal focus peak while truncates the side peak component. Numerical simulations are provided and outfield experiments are conducted. The results demonstrate the effectiveness of the proposed method comparing with correlation-based method.

Assessing the influence of a rapid water drawdown on the seismic response characteristics of a reservoir rock slope using time–frequency analysis

To investigate the influence of a rapid water drawdown (RWD) on the seismic response characteristics of reservoir rock slopes, numerical dynamic analyses and shaking table tests are conducted on a rock slope containing discontinuities under a RWD using time–frequency analysis from the perspective of spectral and energy propagation characteristics. The results show that a RWD has a magnification effect on the seismic response of a surface slope, which is mainly manifested as the RWD causing the seismic energy of the surface slope to increase significantly. The RWD has a magnification effect on the Fourier spectrum amplitude of the low-order natural frequency band. A time–frequency domain analysis shows that the RWD has an influence on the characteristics of the seismic Hilbert energy spectrum (HES) in the low-frequency band of the surface slope and magnifies the amplitude of the marginal spectrum (MS) in the high-frequency band. In addition, the applicability of the Fourier spectrum, HES and MS in analysing the relationship between the RWD and the slope dynamic response is discussed. An analysis of the seismic HES shows that the RWD has a major impact on the overall dynamic response of the surface slope, while the RWD has a significant impact on the local dynamic response of the surface slope based on the Fourier spectrum and the MS. The influence mechanism of the RWD on the HES and MS of the slope is also discussed. Moreover, the influence of a RWD on the development process of seismic damage to the slope is clarified using an energy-based method.

Damage identification in steel girder bridges using modal strain energy-based damage index method and artificial neural network

Health monitoring of infrastructures is of utmost significance, as they play a vital role in transportation. Identifying damages at the onset is essential to ensure the structure’s health state. The vibration-based damage identification methods use the vibration characteristics of structures to detect damages. Also, artificial neural networks (ANN) have been used to estimate damage magnitude with varied success. In this study, a two-stage damage identification technique was proposed to locate and estimate damages in steel girder bridges. The performance and feasibility of the proposed method were evaluated by applying several single and multiple damage scenarios to a validated finite element (FE) model of I-40 Bridge. Initially, the damage location was determined using the modal strain energy-based damage index method. For this purpose, the damage index was calculated separately for the first three bending modes of the bridge. The calculated damage vectors were combined along the length of girders. The peak value of the combined damage index showed the damage location along the length of steel plate girders. The results revealed that all the damage locations were detected with appropriate accuracy even if multiple damage scenarios existed in plate girders. In the second step, an ANN was used for estimation of damage severity. The damage index was used as input parameters to train the ANN. Then, the trained ANN could predict the severity of structural damages. The results indicated appropriate accuracy proposed by ANN for estimating the damage magnitude as well as proper performance of the proposed method.

Microstructural Topology Optimization of Constrained Layer Damping on Plates for Maximum Modal Loss Factor of Macrostructures

This paper presents microstructural topology optimization of viscoelastic materials for the plates with constrained layer damping (CLD) treatments. The design objective is to maximize modal loss factor of macrostructures, which is obtained by using the Modal Strain Energy (MSE) method. The microstructure of the viscoelastic damping layer is composed of 3D periodic unit cells. The effective elastic properties of the unit cell are obtained through the strain energy-based method. The density-based topology optimization is adopted to find optimal microstructures of viscoelastic materials. The design sensitivities of modal loss factor with respect to the design variables are analyzed and the design variables are updated by Method of Moving Asymptotes (MMA). Numerical examples are given to demonstrate the validity of the proposed optimization method. The effectiveness of the optimal design method is illustrated by comparing a solid and an optimized cellular viscoelastic material as applied to the plates with CLD treatments.

An approximate closed-form buckling solution for the local skin buckling of stiffened plates with omega stringers: The case of antisymmetric cross-ply and angle-ply laminations

Estimating the buckling resistance of stiffened plates with detailed numerical models can provide high fidelity results, but for the preliminary design phase of aircraft structures this is impractical, since numerous iterations or sensitivity analyses are required. Analytical solutions become preferable for this design phase. To this end, an approximate closed-form solution is developed to estimate the critical skin local buckling load of stiffened plates with omega stringers with antisymmetric cross-ply and angle-ply lamination. This is obtained using an innovative energy-based homogenization method that yields to an equivalent bending stiffness matrix. The research further examines the influence of two key parameters to the analytical estimation of the buckling load of the fore mentioned partially anisotropic skin. The first parameter concerns the selection of the appropriate boundary conditions that must be assumed for the skin-stringer junction. The mathematical model considers the part of the skin between two consecutive omega stringers. The rest of the stiffened plate is replaced by equivalent transverse and rotational springs, which act as elastic edge supports. The elastic restraints are determined with two distinctive approaches considering the bending and torsional stiffness of the omega stringers. As a second parameter two different deflection functions (trigonometric and polynomial) are considered for the Rayleigh-Ritz method. Aim is to determine the appropriate combination of elastic restrain stiffness and deflection function that yield to more accurate buckling results for the cases of antisymmetric cross-ply and angle-ply skin laminations. Finally, the obtained analytical results are evaluated by comparing them with the respective numerical. The comparison showed that a satisfactory correlation can be achieved, for a certain combination of boundary conditions and deflection functions. Discussion and conclusions regarding the accuracy, discrepancies and limitations of the derived buckling solution are highlighted.