Inelasticity Parameter Research Articles

Inelastic acceleration ratios for nonstructural components

Non-Structural Components (NSCs) include all the elements that are part of structures but are not typically designed to resist the loads acting on the structures. In recent major earthquakes, the seismic design of NSCs has proved to be a key feature to assure suitable performance of structures. The accelerations experienced on the floors of structures are much higher than those at ground level, and therefore, NSCs located at these levels are highly susceptible to experiencing inelastic responses. However, relatively few studies have investigated the inelastic response of NSCs. Specifically, the inelastic absolute acceleration ratio (IAR) of NSCs is an important inelastic design parameter that has been the subject of little investigation. Therefore, this research aims to investigate the inelastic response of NSCs through its IARs by using seven elastic buildings of three different structural systems and three different sets of far-field seismic ground records. The inelastic response of the NSC is characterized by the yield strength reduction coefficient (R). The results of the study were used to develop an equation for estimating the characteristic period of ground IARs. In general, the characteristic period is equal to the fundamental period of the structure for the floor IARs and floor Inelastic Displacement Ratios (IDRs). In addition, the results helped to identify that the convergence values of the IARs mainly depend on the R factor and the damping ratio of the NSC and show consistency in both the ground IARs and the floor IARs. Furthermore, the trends of the floor IDRs are more unstable and less predictable than those of the IARs. An improved equation for predicting both ground and floor IARs is also proposed.

Numerical analysis of hydromagnetic particulate Reiner-Rivlin fluid flow in an asymmetric non-uniform channel with a heat source

The main objective of the present article is to investigate the hydromagnetic particle Reiner-Rivlin fluid flow in an asymmetric (divergent) channel. The non-dimensionalized equations solved by the shooting method. The graphs are intended to examine how different developing parameters affect the thermal and velocity fields. The effects of various parameters on skin friction and the rate of heat transmission along channel walls are investigated using tabular data. The current results are in admirable agreement with the published data. The fluid velocity delineates in the first portion of the channel and rockets up in the second when the inelastic parameter increases. An increase in cross-flow Reynolds number is accompanied by an increasing tendency in particle temperature. Several areas, like metal steam resistors, fiber suspension in paper manufacture, etc., are significantly impacted by the magnetic field’s action on Reiner-Rivlin fluid through asymmetric channels.

Seismic response of slender MDOF structures with self‐centering base shear and moment mechanisms

AbstractAs the amplification of seismic force demands due to higher‐mode effects on tall buildings is increasingly recognized as a design challenge, a number of high‐performance systems have been proposed to limit such effects through combined base shear‐limiting and moment‐limiting dual mechanisms. To better understand the influence of these dual base systems on the overall seismic behavior of tall buildings, this paper presents a study on the seismic response of Multi‐Degree‐of‐Freedom (MDOF) systems incorporating combined base shear‐limiting and moment‐limiting mechanisms. For an MDOF system with a given initial period and base strength level, the base shear‐limiting mechanism is defined by a shear strength factor, an inelastic stiffness parameter, and an energy‐dissipation parameter, while the base moment‐limiting mechanism is defined by a moment strength factor. To determine the influence of these parameters on the overall seismic responses of MDOF structures, a comprehensive parametric study was conducted, and the results were presented and discussed in terms of base displacement and rotation demands, seismic force demand amplification at the base and along the height, peak floor acceleration, peak roof drift, and absorbed energy. The numerical modeling methodology used in the parametric study was validated against 200 small‐scale shaking table tests of a scaled MDOF specimen with a base shear and moment dual‐mechanism system and was used to model MDOF structures that are representative of tall buildings with initial periods ranging from 1.0 to 10 s and having various base‐mechanism properties. The parametric study was then conducted using an ensemble of 20 Ground Motions (GM) scaled to three code‐specified seismic hazard levels for Los Angeles, California. The results of this study can be used to facilitate the design of base shear and moment dual‐mechanism systems for mitigating higher‐mode effects and enhancing the seismic resilience of tall buildings.

Low-mass inelastic dark matter direct detection via the Migdal effect

We consider searches for the inelastic scattering of low-mass dark matter at direct detection experiments, using the Migdal effect. We find that there are degeneracies between the dark matter mass and the mass splitting that are difficult to break. Using XENON1T data we set bounds on a previously unexplored region of the inelastic dark matter parameter space. For the case of exothermic scattering, we find that the Migdal effect allows xenon-based detectors to have sensitivity to dark matter with ${\cal O}(\mathrm{MeV})$ mass, far beyond what can be obtained with nuclear recoils alone.

An improved unified viscoplastic model for modelling low cycle fatigue and creep fatigue interaction loadings of 9–12%Cr steel

An accurate constitutive model is one of the basic aspects to ensure a precise simulation. This study presents an improved unified viscoplastic model to simulate the various behavior of P92 steel under low cycle fatigue (LCF) and creep fatigue interaction (CFI) loadings. In the proposed model, an accumulated inelastic strain dependent parameter is introduced into the nonlinear kinematic hardening rule to represent the evolutionary behavior of strain-stress hysteresis loops and the varied relaxation behavior during CFI loadings. The traditional isotropic hardening rule is modified as well to capture the accelerated cyclic softening phenomena observed in the prolonged hold time of CFI tests. To validate the accuracy and the predictive capability of the proposed model, LCF tests at various strain amplitudes and CFI tests at different hold time are conducted at elevated temperature of 650 °C. Good agreement between the experimental and simulated results verifies the robustness of the proposed model. In addition, the proposed model is distinguished from published models by few determined material parameters.

Frequency dependent inelastic response of collagen architecture of pig dermis under cyclic tensile loading: An experimental study

The evaluation of collagen architecture of the dermis in response to mechanical stimulation is important as it affects the macroscopic mechanical properties of the dermis. A detailed understanding of the processes involved in the alteration of the collagen structure is required to correlate the mechanical stimulation with tissue remodeling. This study investigated the effect of cyclic frequencies i.e. low (0.1 Hz), medium (2.0 Hz), and high (5.0 Hz) (physiological range) in the alteration of pig dermis collagen structure and its correlation with the macroscopic mechanical response of the dermis. The assessment of the collagen structure of virgin and mechanical tested specimens at tropocollagen, collagen fibril, and fiber level was performed using Fourier-transform infrared-attenuated total reflection (FTIR-ATR), atomic force microscopy (AFM), and scanning electron microscopy (SEM) respectively. After 103 cycles, a significantly higher alteration in collagen structure with discrete plastic-type damage was found for low frequency. This frequency dependent alteration of the collagen structure was found in correlation with the dermis macroscopic response. The value of inelastic strain, stress softening, damage parameter (reduction in elastic modulus), and reduction in energy dissipation were observed significantly large for slow frequency. A power-law based empirical relations, as a function of frequency and number of cycles, were proposed to predict the value of inelastic strain and damage parameter. This study also suggests that hierarchical structural response against the mechanical stimulation is time-dependent rather than cycle-dependent, may affect the tissue remodeling.

Precision Test of the Limits to Universality in Few-Body Physics.

We perform precise studies of two- and three-body interactions near an intermediate-strength Feshbach resonance in ^{39}K at 33.5820(14)G. Precise measurement of dimer binding energies, spanning three orders of magnitude, enables the construction of a complete two-body coupled-channel model for determination of the scattering lengths with an unprecedented low uncertainty. Utilizing an accurate scattering length map, we measure the precise location of the Efimov ground state to test van der Waals universality. Precise control of the sample's temperature and density ensures that systematic effects on the Efimov trimer state are well understood. We measure the ground Efimov resonance location to be at -14.05(17) times the van der Waals length r_{vdW}, significantly deviating from the value of -9.7r_{vdW} predicted by van der Waals universality. We find that a refined multichannel three-body model, built on our measurement of two-body physics, can account for this difference and even successfully predict the Efimov inelasticity parameter η.

Influence of viscous damping and elastic waves on energy dissipation during impacts

For impacts on plane surfaces (plates), the coefficient of restitution or more precisely, the energy dissipation due to elastic waves (Rayleigh, longitudinal, transverse and flexural waves) on the one hand and due to viscoelastic properties on the other hand is calculated, analysed and experimentally investigated. Models concerning elastic waves (Zener, Hunter) and their modifications introduced by us within our latest publications (Boettcher et al., 2016, 2017a, 2017b), which (like the majority of the models in literature) are related to spheres and parabolically impinging bodies, are briefly summarized and extended for the impact of cones to achieve a more realistic description of impact processes and a better understanding of the physical relations.The bending model of Zener is described on the basis of rheological models (contact model) and a simple, general viscoelastic model for a sphere is introduced. Furthermore, two different variants of a combined model are derived with which the coefficient of restitution based on flexural waves (inelasticity parameter λ) and viscoelastic properties (viscoelastic inelasticity parameter ξ) can be calculated. Likewise, analytically approximate solutions are derived. In chemical and process engineering, the proposed approach enables for instance a better description of the impact process between (elastic-plastic) granules or particles with viscous properties (e.g., γ-Al2O3 or synthetic granules) and thin apparatus walls at which flexural waves as well as viscous damping can depict a (decisive) role (fluidized bed, pneumatic conveying).First experimental evaluations show the extent to which viscoelasticity depends on the individual materials and the influence of viscoelasticity within the range of the (developing) flexural wave. The combined model shows a qualitative good agreement to the experimental measurements, but also an increasing deviation from the experimental values with increasing viscous damping.

Marchant - Rankine’s - Murzewski approach for modelling of the buckling resistance of welded I-section columns

This paper discusses different aspects of analytical and numerical modelling of the buckling resistance of welded I-section columns subjected to axial compression. The section considered is of class 1 that implies no local buckling affecting the column performance. The proposed analytical formulation of the buckling resistance is based on the so-called Marchant-Rankine's-Murzewski approach (M-R-M approach). The model proposed is of a 2D type and is a simplification of the 3D one that has recently been presented by the authors. The parameters of equivalent stress-strain model of the postwelding steel are calibrated in two stages of the best fit approximation procedure and with use of numerical results of the finite element simulation of the buckling resistance. In the first stage, the postyielding inelastic tangent stiffness parameter ξE,eff is evaluated with fixed value of the first yield parameter ψeff= ψcom. A target of the second stage is to assign the best fit value of the first yield parameter ψeff and the imperfection factor n that allows for accounting the effect of geometric imperfections.

Analysis Methodology of Inelastic Constitutive Parameter Using State Space Method and Neural Network

Background/Objectives: In this paper, we present a method for describing a set of variables of an inelastic constitutive equation based on state space method (SSM) and neural network (NN). The advantage of this method is that it can identify the appropriate parameters.Methods/Statistical analysis: Two NNs based on SSM are proposed. One outputs the ratio of inelastic strain for the internal parameters of the material, and the other is the following state of the inelastic strain ratio and material internal variable. Both NNs were trained and successfully collected using input and output data generated by Chaboche 's model.Findings: As a result, previous NNs have demonstrated their validity as a powerful material model. However, the training data for the proposed NN can’t be easily obtained from actual experimental data. Previous neural networks can reproduce the original stress-strain curves. The NNs also produced untrained curves to demonstrate interpolation capabilities. It was also found that the NNs can be estimated to be close to training data. The author defines the implicit constitutive model and proposes the implicit viscous constitutive model using NNs. In modeling, inelastic behavior is generalized in state space representation, and the state space form is constructed by NNs using an input-output data sets. The proposed model was first created from the pseudo-experimental data generated by one of the commonly used configuration models and has been found to be a good replacement for the model. The actual experimental data was then tested, and the proposed model showed the accuracy of its superiority over all existing specified models because the amount of model errors was negligible.Improvements/Applications: The comparison between the NN constitutive laws with the Chaboche’s model indicates that the NN constitutive law generated curves with less model errors than the experimental data, thereby indicating the superiority of the neural constitutive law to explicit constitutive laws as a material model.

Neutron–19C scattering: Towards including realistic interactions

Low-energy neutron–C19 scattering is studied in the three-body n+n+C18 model using a realistic nn potential and a number of shallow and deep n–C18 potentials, the latter supporting deeply-bound Pauli-forbidden states that are projected out. Exact Faddeev-type three-body scattering equations for transition operators including two- and three-body forces are solved in the momentum-space partial-wave framework. Phase shift, inelasticity parameter, and cross sections are calculated. For the elastic n–C19 scattering in the JΠ=0+ partial wave the signatures of the Efimov physics, i.e., the pole in the effective-range expansion and the elastic cross section minimum, are confirmed for both shallow and deep models, but with clear quantitative differences between them, indicating the importance of a proper treatment of deeply-bound Pauli-forbidden states. In contrast, the inelasticity parameter is mostly correlated with the asymptotic normalization coefficient of the C19 bound state. Finally, in the regime of very weak C19 binding and near-threshold (bound or virtual) excited C20 state the standard Efimovian behaviour of the n–C19 scattering length and cross section was confirmed, resolving the discrepancies between earlier studies by other authors (Mazumdar et al., 2006 [20], Yamashita et al., 2007 [23]).

Damage‐based seismic planar pounding analysis of adjacent symmetric buildings considering inelastic structure–soil–structure interaction

SummaryIn cities and urban areas, building structures located at close proximities inevitably interact under dynamic loading by direct pounding and indirectly through the underlying soil. Majority of the previous adjacent building pounding studies that have taken the structure–soil–structure interaction (SSSI) problem into account have used simple lumped mass–spring–dashpot models under plane strain conditions. In this research, the problem of SSSI‐included pounding problem of two adjacent symmetric in plan buildings resting on a soft soil profile excited by uniaxial earthquake loadings is investigated. To this end, a series of SSSI models considering one‐directional nonlinear impact elements between adjacent co‐planar stories and using a method for direct finite element modeling of 3D inelastic underlying soil volume has been developed to accurately study the problem. An advanced inelastic structural behavior parameter, the seismic damage index, has been considered in this study as the key nonlinear structural response of adjacent buildings. Based on the results of SSSI and fixed base case analyses presented herein, two main problems are investigated, namely, the minimum building separation distance for pounding prevention and seismic pounding effects on structural damage in adjacent buildings. The final results show that at least three times, the International Building Code 2009 minimum distance for building separation recommended value is required as a clear distance for adjacent symmetric buildings to prevent the occurrence of seismic pounding. At the International Building Code‐recommended distance, adjacent buildings experienced severe seismic pounding and therefore significant variations in storey shear forces and damage indices. Copyright © 2016 John Wiley & Sons, Ltd.

Universal Loss Dynamics in a Unitary Bose Gas

The low temperature unitary Bose gas is a fundamental paradigm in few-body and many-body physics, attracting wide theoretical and experimental interest. Here we first present a theoretical model that describes the dynamic competition between two-body evaporation and three-body re-combination in a harmonically trapped unitary atomic gas above the condensation temperature. We identify a universal magic trap depth where, within some parameter range, evaporative cooling is balanced by recombination heating and the gas temperature stays constant. Our model is developed for the usual three-dimensional evaporation regime as well as the 2D evaporation case. Experiments performed with unitary 133 Cs and 7 Li atoms fully support our predictions and enable quantitative measurements of the 3-body recombination rate in the low temperature domain. In particular, we measure for the first time the Efimov inelasticity parameter $\eta$ * = 0.098(7) for the 47.8-G d-wave Feshbach resonance in 133 Cs. Combined 133 Cs and 7 Li experimental data allow investigations of loss dynamics over two orders of magnitude in temperature and four orders of magnitude in three-body loss. We confirm the 1/T 2 temperature universality law up to the constant $\eta$ *.

Combined viscoelastic and elastic wave dissipation mechanism at low velocity impact

The understanding of effects occurring during low velocity normal particle impact on a hard elastic plate is important for the description of different processes occurring during pneumatic conveying, in jet mills, mixers, or fluidized bed apparatuses. In this study, a suitable semi-empiric method is proposed to calculate the coefficient of restitution. This coefficient of restitution is modelled by means of combination of two different approaches. The first approach is based on dissipation of impact energy due to bending wave excitation in the plate described only by one inelasticity parameter. The second approach is based on viscoelastic mechanism of energy dissipation, represented by an additional viscoelastic damping coefficient. Thus, these two coefficients are responsible for bending and viscoelastic energy dissipation and are calculated independently from each other. The summarized energy dissipation is used to determine both material parameters and coefficients. A good agreement between calculated and measured coefficient of restitution was observed. In this way, the interaction between steel spheres impacting on glass plates with a thickness comparable to the diameter of the sphere was calculated as an example.

Universal three-body recombination and Efimov resonances in an ultracold Li-Cs mixture

We study Efimov resonances via three-body loss in an ultracold two-component gas of fermionic $^6$Li and bosonic $^{133}$Cs atoms close to a Feshbach resonance at 843~G, extending results reported previously [Pires \textit{et al.}, Phys. Rev. Lett. 112, 250404 (2014)] to temperatures around 120~nK. The experimental scheme for reaching lower temperatures is based upon compensating the gravity-induced spatial separation of the mass-imbalanced gases with bichromatic optical dipole traps. We observe the first and second excited Li-Cs-Cs Efimov resonance in the magnetic field dependence of the three-body event rate constant, in good agreement with the universal zero-range theory at finite temperature [Petrov and Werner, Phys. Rev. A 92, 022704 (2015)]. Deviations are found for the Efimov ground state, and the inelasticity parameter $\eta$ is found to be significantly larger than those for single-species systems.

A novel approach to evaluate the elastic impact of spheres on thin plates

A novel analytical approach to solve the otherwise mathematically strenuous Zener model for elastic sphere impacts on large, thin plates, has been presented to find a comfortable solution for the coefficient of restitution (CoR). The proposed analytical approach provides accurate results for the range of coefficients of restitution larger than 0.2 and gives a very good approximation of the Zener model. Furthermore, the Zener model has been numerical solved with high accuracy and has been used to evaluate the inelasticity parameter as well as the coefficient of restitution for different material combinations and ratios of sphere diameter to plate thickness. Both approaches have been used to evaluate the coefficient of restitution of elastic glass beads at impact with glass plates of different thicknesses using experimental free fall test measurements. A significant dependence of the coefficient of restitution of elastic spheres on the ratio of sphere diameter to plate thickness as well as on the impact velocity and on the inelasticity parameter has been observed respectively, which can be well described by the Zener model and the proposed analytical approach.

Quenching to unitarity: Quantum dynamics in a three-dimensional Bose gas

We study the dynamics of a zero-temperature Bose condensate following a sudden quench of the scattering length from noninteracting to unitarity (infinite scattering length). We apply three complementary approaches to understand the momentum distribution and loss rate. First, using a time-dependent variational ansatz for the many-body state, we calculate the dynamics of the momentum distribution. Second, we demonstrate that, at short times and large momenta compared to those set by the density, the physics can be understood within a simple, analytic two-body model. We make a quantitative prediction for the evolution of Tan's contact and find features in the momentum distribution that are absent in equilibrium. Third, we study three-body loss at finite density under the same dynamic scenario. We find lifetimes that are long compared to the saturation times of large-momentum modes, and we relate this result to the three-body inelasticity parameter.

Effects of inelastic collisions on Alfvén waves in partially ionized plasmas

Based on a three-component description of partially ionized plasmas (i.e., electrons, ions, and neutral atoms), effects of inelastic collisions between ions (neutrals) and electrons on Alfv,n waves (AWs) in a partially ionized plasma are studied. It is shown that for a fixed ionizability () or a fixed inelastic collision parameter (chi, i.e., the ratio of the inelastic to elastic collision frequency), the damping rate of AWs has a peak value round k (z) v (A)/nu (in) 1, where k (z) is the parallel wavenumber of AWs, v (A) is the Alfv,n velocity, and nu (in) is the elastic collision frequency between ions and neutrals. On the other hand, the damping rate of AWs decreases monotonously with the ionizability for a fixed inelastic collision parameter, but has a peak value when the inelastic collision parameter varies for sufficiently small ionizability (). For sufficiently large ionizability (), it is found that the damping rate decreases with the inelastic collision parameter. The results may help us to understand the physics of AWs in partially ionized plasmas.

Angular distribution of reflected ions at oblique incidence on a target

The angular distribution of ions reflected from a solid surface has been obtained as a result of solving the Boltzmann equation, written in the diffusion approximation by the method of moments. The angular distribution is dependent on the energy and angle of ion incidence, the ratio of the ion and target atomic masses, and the inelastic energy loss parameter. Good agreement has been shown between the theory and the experimental and computer simulation data.

Comparison between surface excitation parameter obtained from QUEELS and SESINIPAC

Surface excitations significantly influence the measured peak intensities in elastic peak electron spectroscopy. They are characterised by the surface excitation parameter (SEP) defined as the change in excitation probability of an electron caused by the presence of the surface in comparison with an electron moving in an infinite medium. It is thus important to have a large database of SEP values or to have the possibility to determine it with a user‐friendly software. Recently, Novák developed the programme Software for Electron Solid Inelastic Interaction Parameter Calculations (SESINIPAC) within the model of Tung, Chen, Kwei and Chou, which allows to determine inelastic mean free path, differential inelastic mean free path, SEP and differential SEP for various energy loss function models and dispersion relations with as only input the energy loss function of the material. Using SESINIPAC, we calculate SEP for 27 different types of materials (metals, semiconductors and insulators) and for various angles and energies. We compare these results with those obtained previously with the software Quantitative Analysis of Electron Energy Losses at Surfaces (QUEELS), which uses the Yubero‐Tougaard model. We show that the dependence on angle of emission and energy is quite similar for the two models. However, the absolute values calculated with SESINIPAC are generally larger than those calculated with QUEELS, and the mean relative difference is 20% for metals and semiconductors but exceeds 50% for insulators. Copyright © 2012 John Wiley & Sons, Ltd.