Energetic Approach Research Articles

Fatigue assessment of welded joints by means of the Strain Energy Density method: Numerical predictions and comparison with Eurocode 3

The main aim of the present work is to investigate the effects of different parameters on the fatigue strength of four different welded details through an energetic approach based on the Strain Energy Density failurecriteria.The results of the finite element analyses have been compared with the fatigue strength predicted by the design guidance EN 1993-1-9:2005, also known as Eurocode 3, which establishes the rules for the fatigue design of steel welded joints.The results obtained in this work highlight an overestimation of the fatigue strength by the Eurocode 3 with regard to the details considered.

Boundary Integral Formulation of Frictionless Contact Problems Based on an Energetic Approach and Its Numerical Implementation by the Collocation BEM

A unified methodology to solve problems of frictionless unilateral contact as well as adhesive contact between linear elastic solids is presented. This methodology is based on energetic principles and is casted to a minimization problem of the total potential energy. Appropriate boundary integral forms of the energy are defined and the quadratic problem form of the contact problem is proposed. The problem is solved by the collocation boundary element method (BEM). To solve the quadratic problem two algorithms are developed, both being variants of the well-known conjugate gradient algorithm. The difference between them is given by an explicit construction or not of the quadratic-problem matrix. This matrix has the same physical meaning as the stiffness matrix commonly used in the context of the finite element method (FEM). Both symmetric and non-symmetric formulations of this matrix are presented and discussed, showing that the non-symmetric one provides more accurate results. The present procedure, in addition to its interest by itself, can also be extended to problems where dissipative phenomena take place such as friction, damage and plasticity. Elements of the numerical implementation are briefly presented and the numerical solution of some standard problems of frictionless contact are given and compared to those obtained by other well-known BEM and FEM procedures for contact problems.

Fluxweb: An R package to easily estimate energy fluxes in food webs

Understanding how changes in biodiversity will impact the stability and functioning of ecosystems is a central challenge in ecology. Food‐web approaches have been advocated to link community composition with ecosystem functioning by describing the fluxes of energy among species or trophic groups. However, estimating such fluxes remains problematic because current methods become unmanageable as network complexity increases. We developed a generalisation of previous indirect estimation methods assuming a steady state system [1, 2, 3]: the model estimates energy fluxes in a top‐down manner assuming system equilibrium; each node's losses (consumption and physiological) balances its consumptive gains. Jointly, we provide theoretical and practical guidelines to use the fluxweb R package (available on CRAN at https://cran.r-project.org/web/packages/fluxweb/index.html We also present how the framework can merge with the allometric theory of ecology [4] to calculate fluxes based on easily obtainable organism‐level data (i.e. body masses and species groups ‐eg, plants animals), opening its use to food webs of all complexities. Physiological losses (metabolic losses or losses due to death other than from predation within the food web) may be directly measured or estimated using allometric relationships based on the metabolic theory of ecology, and losses and gains due to predation are a function of ecological efficiencies that describe the proportion of energy that is used for biomass production. The primary output is a matrix of fluxes among the nodes of the food web. These fluxes can be used to describe the role of a species, a function of interest (e.g. predation; total fluxes to predators), multiple functions, or total energy flux (system throughow or multitrophic functioning). Additionally, the package includes functions to calculate network stability based on the Jacobian matrix, providing insight into how resilient the network is to small perturbations at steady state. Overall, fluxweb provides a flexible set of functions that greatly increase the feasibility of implementing food‐web energetic approaches to more complex systems. As such, the package facilitates novel opportunities for mechanistically linking quantitative food webs and ecosystem functioning in real and dynamic natural landscapes.

Energetic variational approaches for non-Newtonian fluid systems

We consider the dominant equations for the motion of the non-Newtonian fluid in a domain from an energetic point of view. We apply our energetic variational approaches and the first law of thermodynamics to derive the generalized compressible non-Newtonian fluid system. We also derive the generalized incompressible non-Newtonian fluid system by using our energetic variational approaches.

Non-linear method of determining vehicle pre-crash speed based on tensor B-spline products with probabilistic weights — Intermediate Car Class

In the following study we consider the Intermediate Car Class. We apply a novel non-linear method, where the work W of car deformation is defined as an algebraic function of deformation ratio Cs.We use the data from the NHTSA (National Highway Traffic Safety Administration) database comprising numerous frontal crash tests. On the basis of this database, we determine the mathematical model parameters. In the so-called energetic approach, collisions are treated as non-elastic.The velocity threshold that defines the elastic collision was set to be 11km/h. Such an approach, which greatly simplifies our considerations, determines the linear dependence of energy lost during deformation on deformation coefficient Cs.The coefficient Cs is calculated as a weighted mean value of deformation points C1–C6. In this paper, the authors suggest a more precise non-linear method in order to determine the work of deformation.

Modeling dynamic systems: contribution to the unsteady behavior of a condenser based on the pseudo-bond graph approach

ABSTRACTThis article is devoted to the dynamic study of the brazed plate condenser (BPC). The proposed model is based on the bond graph theory. The proposed model is based on the bond graph theory because of its energetic approach and multi-physics character of the studied system. The model is discretized into five control volumes. The resolution of mass and energy equations is done by Runge-Kutta method embedded in 20sim software. Analyses of simulation results show that the model has a good ability to transcribe the time evolution of the temperature and pressure in both regimes, transitional and permanent. Also, the model is experimentally validated without any fitting of the set of thermal exchange coefficients.

Insight into the specificity and severity of pathogenic mechanisms associated with missense mutations through experimental and structural perturbation analyses.

Most pathogenic missense mutations cause specific molecular phenotypes through protein destabilization. However, how protein destabilization is manifested as a given molecular phenotype is not well understood. We develop here a structural and energetic approach to describe mutational effects on specific traits such as function, regulation, stability, subcellular targeting or aggregation propensity. This approach is tested using large-scale experimental and structural perturbation analyses in over thirty mutations in three different proteins (cancer-associated NQO1, transthyretin related with amyloidosis and AGT linked to primary hyperoxaluria type I) and comprising five very common pathogenic mechanisms (loss-of-function and gain-of-toxic function aggregation, enzyme inactivation, protein mistargeting and accelerated degradation). Our results revealed that the magnitude of destabilizing effects and, particularly, their propagation through the structure to promote disease-associated conformational states largely determine the severity and molecular mechanisms of disease-associated missense mutations. Modulation of the structural perturbation at a mutated site is also shown to cause switches between different molecular phenotypes. When very common disease-associated missense mutations were investigated, we also found that they were not among the most deleterious possible missense mutations at those sites, and required additional contributions from codon bias and effects of CpG sites to explain their high frequency in patients. Our work sheds light on the molecular basis of pathogenic mechanisms and genotype-phenotype relationships, with implications for discriminating between pathogenic and neutral changes within human genome variability from whole genome sequencing studies.

Energy-based approach for fracture assessment of several rocks containing U-shaped notches through the application of the SED criterion

This work presents an energetic continuum approach for the fracture assessment of rocks containing U-shaped notches and subjected to Mode I loading conditions. Three different methodologies are proposed, all based on the premise that brittle failure will occur when the average strain energy density over a certain control area reaches a critical value that only depends on the material, as stated by the Strain Energy Density (SED) criterion.The first method proposed (A) deals with the application of the SED criterion through an expression with a series of already tabulated parameters, which are particularised for the analysed rocks by rational extrapolation. By contrast, the second method (B) aims to obtain numerically the previously extrapolated parameters, and the third method (C) directly relates the strain energy density with the applied load, without the use of those parameters.The research is based on the results obtained from an exhaustive experimental programme comprising 300 fracture specimens tested in four-point bending conditions. These tests combine parallelepiped samples made of six different types of rocks (two marbles, two limestones, a sandstone and a granite) and containing eight different notch radii (varying from 0.15 mm up to 15 mm).Thus, this work aims to show the potential, capacity and limitations of the SED criterion in rock fracture analyses, by comparing the experimentally obtained fracture loads to those predicted by the three proposed methodologies.

Impact of energy dissipation on interface shapes and on rates for dewetting from liquid substrates

We revisit the fundamental problem of liquid-liquid dewetting and perform a detailed comparison of theoretical predictions based on thin-film models with experimental measurements obtained by atomic force microscopy. Specifically, we consider the dewetting of a liquid polystyrene layer from a liquid polymethyl methacrylate layer, where the thicknesses and the viscosities of both layers are similar. Using experimentally determined system parameters like viscosity and surface tension, an excellent agreement of experimentally and theoretically obtained rim profile shapes are obtained including the liquid-liquid interface and even dewetting rates. Our new energetic approach additionally allows to assess the physical importance of different contributions to the energy-dissipation mechanism, for which we analyze the local flow fields and the local dissipation rates. Using this approach, we explain why dewetting rates for liquid-liquid systems follow no universal power law, despite the fact that experimental velocities are almost constant. This is in contrast to dewetting scenarios on solid substrates and in contrast to previous results for liquid-liquid substrates using heuristic approaches.

Theoretical Model to Adhesion Failure in Granular Materials

Two disjoint particles joined by adhesion materials are here considered when dead load operating over it. We will to perform a theoretical characterization of this micro-system through a behavior specific approach. This last is located within the hypo-elasticity framework since granular material behavior can be in according whit it. Again we expand the framework joining some further aspects which the deformation field. Over this, we focus peculiar response of the extreme elastic deformation through energetic approach. The model will be able to simulate asphalt mixture behavior in the damage evolution for bond adhesion break.

Revisiting statistical size effects on compressive failure of heterogeneous materials, with a special focus on concrete

Size effects on mechanical strength, i.e. the fact that larger structures fail under lower stresses than smaller ones, already highlighted by Leonardo da Vinci and Edmée Mariotte centuries ago, remain nowadays a crucial problem to establish structural design rules and safety regulations from an upscaling of laboratory data. These size effects are generally explained either from a deterministic energetic approach that predicts a non-vanishing asymptotic strength but, by construction, does not account for fluctuations around the mean strength and their size dependence, or from a statistical approach based on the weakest-link theory that implies a vanishing strength towards large scales. We recently proposed an alternative framework based on an interpretation of compressive failure of heterogeneous materials as a critical transition from an intact to a failed state, which releases the underlying hypotheses of the weakest-link theory, pure brittleness and the independence of damage events, while predicting a non-vanishing asymptotic mean strength but vanishing intrinsic fluctuations at large scales. Here, from an extensive series of uniaxial compression experiments (527 tests) on concrete samples with four different sizes and three different microstructures, we demonstrate (i) the failure of the weakest-link theory in this case, and instead (ii) the pertinence of our critical framework to account for size effects on compressive strength of an emblematic quasibrittle material, concrete, in terms of average strength, associated fluctuations, and probability of failure. From a detailed analysis of the microstructural disorder of our materials, we show that the pore structure, rather than the concrete mix, plays a significant role on size effects on strength. In this framework, the asymptotic strength σ∞ becomes the most relevant, material-dependent parameter for the dimensioning of large-scale structures from an upscaling of small-scale laboratory mechanical tests. An additional parameter, homogeneous to a length scale, controls the size dependence of the relative fluctuations of the strength. These new results call for a re-evaluation of classical design rules and the establishment of safety regulations from laboratory data for the compressive loading of quasi-brittle materials like concrete.

Methods for optimized design and management of CHP systems for district heating networks (DHN)

The paper analyzes some of the problems connected with the design, construction and management of cogeneration plants for district heating networks (CHP-DHN). Although the advantages of cogeneration systems compared with conventional ones for separate energy production, one of the unresolved problems is that of the variability of operating conditions, can often render the application of these solutions ineffective. In particular, the aim of this study is to propose a multi-objective optimization methodology that tries to take into account both energy and economic aspects.After an analysis of the current scenario, the application and use of CHP plants in the international context and the main technological features, followed by the identification of incentive systems that have allowed or limited the spread, attempts are made to define a design methodology based on a multi-level optimum design based approach for increasing the operation share of CHP. The methodology starts from a general system vision, up to detailed aspects such as the management of a CHP-DHN system, taking into account the multiplicity of variables and constraints involved. This methodology has been applied to two case studies representative of the different applications, to verify its robustness and analyze the possible results obtainable.In particular, a general case was taken into consideration, in which a first level design was performed by analyzing various possible system configurations and evaluating their goodness through the tools provided by the aforementioned multi-objective methodology. Then the methodology has been applied to an intermediate level, taking into consideration an existing CHP-DHN plant and going to evaluate the performance considering possible modification of the operation.The results obtained confirm that a combined energetic and economic approach to design allows to obtain an economically feasible system, but at the same time avoids incurring over-sizing, under-sizing or functioning phenomena far from the concept of energy efficiency, difference of what happens for many plants today in operation. Furthermore, through a simple variation of the modularity of the plant, significant benefits can be obtained.

Budgets of Disturbances Energy for Nozzle Flows at Subsonic and Choked Regimes

The noise generated by the passage of acoustic and entropy perturbations through subsonic and choked nozzle flows is investigated numerically using an energetic approach. Low-order models are used to reproduce the experimental results of the hot acoustic test rig (HAT) of Deutsches Zentrum für Luft- und Raumfahrt (DLR), and energy budgets are performed to characterize the reflection, transmission, and dissipation of the fluctuations. Because acoustic and entropy perturbations are present in the flow in the general case, classical acoustic energy budgets cannot be used and the disturbances energy budgets proposed by Myers (1991, “Transport of Energy by Disturbances in Arbitrary Steady Flows,” J. Fluid Mech., 226, pp. 383–400.) are used instead. Numerical results are in very good agreement with the experiments in terms of acoustic transmission and reflection coefficients. The normal shock present in the diffuser for choked regimes is shown to attenuate the scattered acoustic fluctuations, either by pure dissipation effect or by converting a part of the acoustic energy into entropy fluctuations.

PROSODIC EXPRESSION OF EMOTIONAL-AND-PRAGMATIC POTENTIAL OF A SPOKEN ENGLISH PROVERB

The paper is a study of the prosodic features involved in the oral actualisation of English proverbs as influenced by structural, emotional and pragmatic factors, which are defined within the framework of a new energetic approach to the research of phonetic phenomena. On the basis of auditory and acoustic analyses of English proverbs, the authors describe the energetic specificity of their prosodic organisation. This description introduces energy-grams formed with the use of a quantitative K -criterion of the texts’ emotional and pragmatic potentials, as well as their typical intonation patterns. Using the traditional method of linguistic interpretation of the results obtained, the authors substantiate invariant and variant intonation patterns of English proverbs, whose parameters are described both within the text’s structural elements and at their junctures. The authors come to the conclusion that an energetic approach to the study of a complex interaction of emotional, pragmatic, semantic and structural factors makes it possible to present a comprehensive description of invariant and variant prosodic patterns for any type of texts on the basis of such fundamental linguistic categories as emotion, pragmatics, structure, and meaning.

Fatigue life assessment for a welded detail: advantages of a local energetic approach and experimental validation

In modern civil buildings, as well as in mechanical and naval constructions, welding is a widely diffused technological process. The fatigue assessment, as design or verification procedure, of a welded joint to evaluate his endurance with respect to a load spectrum is a challenging but of paramount importance procedure. Several techniques have been proposed in the literature, constantly researching efficient, cost effective and reliable methods to predict the behavior of a complex welded structures. Some of them are part of norms and standards which any design engineer must respect. The aim of the present work is to compare the results provided by some of the principal fatigue life assessment procedures for welded joints, focusing the attention on the stress intensity factor evaluation by the use of numerical methods. Finally the proposed numerical method has been experimentally validated.

Experimental investigation of damage detection in plate-like structure using combined energetic approaches

In this paper, an experimental investigation of damage detection in plate-like structure using energetics approaches is presented. Two energetics approaches are developed to localize the damage in structure at low-, medium-, and high-frequency range. The first one is the inverse simplified energy method, which is used for the identification of the excitation source and the detection of damage in medium and high frequencies. The second one is the curvature method, which is used for the damage detection in the low and medium frequencies. The main novelty of this paper is to combine these energetics approaches in order to localize the damage in all frequency bands. Experimental examples with different characteristics of plate were performed for the validation purpose. Results show that the presented methods can detect precisely the defects location in plate-like structures.

Polarizability of isomeric and related interstellar compounds in the aspect of their abundance

Currently, about 100 carbon-containing molecules have been detected in interstellar and circumstellar environments, and this list includes isomeric substances. In most cases, the minimum energy principle is able to explain the ratio of abundances of the isomeric compounds but in some cases is not. Trying to rationalize the questions unsolved within the energetic approach, we have theoretically studied the polarizability of isomeric and related compounds detected or proposed in interstellar conditions. As we found, in general both energy and polarizability provide the consistent estimates for the ratio of the isomers (e.g., for the isomers having generic formulae CHO, CHN, C3H, C3H2, CHNO, C2H3N, C2H6O, etc.). In the case of the C4H3N isomers, the most abundant isomer (cyanoallene) is not the most stable but the least polarizable that is in a good agreement with relevant experimental study. We assume that the efficiency of the use of polarizability is due to its relevance to the molecules’ response to the external electric fields, i.e., more polarizable molecules are more responsive, more reactive, and, hence, less abundant. Further, we have analyzed the polarizabilities of polycyclic aromatic hydrocarbons, fullerene hydrides (fulleranes), polyynes, and their derivatives with respect to their possible detection under interstellar conditions.

Mechanical characterization of new micro-composites composed by natural clay matrix and PEG 6000 fillers

The aim of this paper is to characterize mechanically the new micro-composites that have been developed in our laboratories. The composites are composed by natural clay (as a matrix) with variant percentages of Polyethylene Glycol 6000 (PEG 6000) as micro-fillers. We used the compression test for the measurement of the static parameters such as elasticity modulus in elastic region and the hardening coefficient which permits to describe the plasticity behaviour of the materials. An additional energetic approach is proposed in order to quantify the evolution of the plasticity of the reinforced materials, caused by the PEG 6000, for different percentages of this polymer.

Work of non-elastic deformation against the deformation ratio of the Subcompact Car Class using the variable correlation method

The presented study considers a Subcompact Car Class in a new non-linear method utilising the work W of car deformation defined as an algebraic function of deformation ratio Cs.In order to develop the experimental data, the method of variable correlation is utilised. Data from the NHTSA (National Highway Traffic Safety Administration) database comprising numerous frontal crash tests are used for the determination of mathematical model parameters. In the non-linear method used up until now, the so-called energetic approach, collisions are treated as non-elastic.The velocity threshold that defines the elastic collision was set to be 11km/h. Such an approach, which is very simplified, determines the linear dependence of energy lost during deformation on deformation coefficient Cs.This coefficient is calculated as a mean value, taking into account the weights of deformation points C1–C6. In this paper, the authors propose a more precise non-linear method in order to determine the work of deformation, and have used the more complex form of deformation coefficient.

Modelling Movement Energetics Using Global Positioning System Devices in Contact Team Sports: Limitations and Solutions.

Quantifying the training and competition loads of players in contact team sports can be performed in a variety of ways, including kinematic, perceptual, heart rate or biochemical monitoring methods. Whilst these approaches provide data relevant for team sports practitioners and athletes, their application to a contact team sport setting can sometimes be challenging or illogical. Furthermore, these methods can generate large fragmented datasets, do not provide a single global measure of training load and cannot adequately quantify all key elements of performance in contact team sports. A previous attempt to address these limitations via the estimation of metabolic energy demand (global energy measurement) has been criticised for its inability to fully quantify the energetic costs of team sports, particularly during collisions. This is despite the seemingly unintentional misapplication of the model's principles to settings outside of its intended use. There are other hindrances to the application of such models, which are discussed herein, such as the data-handling procedures of Global Position System manufacturers and the unrealistic expectations of end users. Nevertheless, we propose an alternative energetic approach, based on Global Positioning System-derived data, to improve the assessment of mechanical load in contact team sports. We present a framework for the estimation of mechanical work performed during locomotor and contact events with the capacity to globally quantify the work done during training and matches.