scholarly journals Towards a Better Understanding of Relationship between Preisach Densities and Polarization Reversals on Hysteresis Characteristic

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Teerawat Monnor ◽  
Yongyut Laosiritaworn ◽  
Rattikorn Yimnirun
Keyword(s):  
Distribution Function ◽  
External Field ◽  
Domain Switching ◽  
Three Dimensional ◽  
Hysteresis Loops ◽  
Mathematical Function ◽  
Hysteresis Characteristic ◽  
Hysteresis Behavior ◽  
Gaussian Distribution Function ◽  
Fundamental Understanding

This work performed Preisach modeling on hysteresis loops, where the contributions of Preisach density characteristics on hysteresis reversals were investigated. Specifically, the three-dimensional Gaussian-distribution function was used to construct the Preisach densities for extracting the associated hysteresis loops. In particular, the influences of three key Gaussian Preisach density characteristics (i.e., density sharpness, density center, and splitting densities) on hysteresis behavior were examined. It was found that sharper density induces more harmonized domain switching, so polarization derivative is enhanced at the coercivity, while the density center indicates the range of external field at which most switching occurs. Moreover, the splitting of the density was found to represent pinching in hysteresis loops, where material tends to actively respond in two different ranges of external field. Consequently, based on these results, significant hysteresis behavior can be revealed using minimal parameters via appropriate mathematical function; that is, another step enhances the fundamental understanding in the hysteresis topic using the Preisach framework.

scholarly journals Macroporous chitosan/methoxypoly(ethylene glycol) based cryosponges with unique morphology for tissue engineering applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pradeep Kumar ◽  
Viness Pillay ◽  
Yahya E. Choonara
Keyword(s):  
Tissue Engineering ◽  
Polymer Network ◽  
Three Dimensional ◽  
Hysteresis Loops ◽  
Interpenetrating Polymer Network ◽  
Morphological Data ◽  
Porous Scaffolds ◽  
Morphological Variations ◽  
Molecular Stability ◽  
The Matrix

AbstractThree-dimensional porous scaffolds are widely employed in tissue engineering and regenerative medicine for their ability to carry bioactives and cells; and for their platform properties to allow for bridging-the-gap within an injured tissue. This study describes the effect of various methoxypolyethylene glycol (mPEG) derivatives (mPEG (-OCH3 functionality), mPEG-aldehyde (mPEG-CHO) and mPEG-acetic acid (mPEG-COOH)) on the morphology and physical properties of chemically crosslinked, semi-interpenetrating polymer network (IPN), chitosan (CHT)/mPEG blend cryosponges. Physicochemical and molecular characterization revealed that the –CHO and –COOH functional groups in mPEG derivatives interacted with the –NH2 functionality of the chitosan chain. The distinguishing feature of the cryosponges was their unique morphological features such as fringe thread-, pebble-, curved quartz crystal-, crystal flower-; and canyon-like structures. The morphological data was well corroborated by the image processing data and physisorption curves corresponding to Type II isotherm with open hysteresis loops. Functionalization of mPEG had no evident influence on the macro-mechanical properties of the cryosponges but increased the matrix strength as determined by the rheomechanical analyses. The cryosponges were able to deliver bioactives (dexamethasone and curcumin) over 10 days, showed varied matrix degradation profiles, and supported neuronal cells on the matrix surface. In addition, in silico simulations confirmed the compatibility and molecular stability of the CHT/mPEG blend compositions. In conclusion, the study confirmed that significant morphological variations may be induced by minimal functionalization and crosslinking of biomaterials.

Kinematical evolution of Globular Clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 524-527
Author(s):  
Maria A. Tiongco ◽  
Enrico Vesperini ◽  
Anna Lisa Varri
Keyword(s):  
Angular Momentum ◽  
Structural Properties ◽  
Globular Clusters ◽  
Velocity Dispersion ◽  
Three Dimensional ◽  
Stellar Populations ◽  
Velocity Space ◽  
Fundamental Understanding

AbstractWe present several results of the study of the evolution of globular clusters’ internal kinematics, as driven by two-body relaxation and the interplay between internal angular momentum and the external Galactic tidal field. Via a large suite of N-body simulations, we explored the three-dimensional velocity space of tidally perturbed clusters, by characterizing their degree of velocity dispersion anisotropy and their rotational properties. These studies have shown that a cluster’s kinematical properties contain distinct imprints of the cluster’s initial structural properties, dynamical history, and tidal environment. Building on this fundamental understanding, we then studied the dynamics of multiple stellar populations in globular clusters, with attention to the largely unexplored role of angular momentum.

Numerical exploration on snap buckling of a pre-stressed hemispherical gridshell

2021 ◽  
pp. 1-11
Author(s):  
Weicheng Huang ◽  
Longhui Qin ◽  
Qiang Chen
Keyword(s):  
Three Dimensional ◽  
Energy Functional ◽  
Elastic Rods ◽  
Geometrically Nonlinear ◽  
Local Response ◽  
Micro Electro Mechanical Systems ◽  
One Dimensional ◽  
Numerical Exploration ◽  
Planar Grid ◽  
Fundamental Understanding

Abstract Motivated by the observations of snap-through phenomena in pre-stressed strips and curved shells, we numerically investigate the snapping of a pre-buckled hemispherical gridshell under apex load indentation. Our experimentally validated numerical framework on elastic gridshell simulation combines two components: (i) Discrete Elastic Rods method, for the geometrically nonlinear description of one dimensional rods; and (ii) a naive penalty-based energy functional, to perform the non-deviation condition between two rods at joint. An initially planar grid of slender rods can be actuated into a three dimensional hemispherical shape by loading its extremities through a prescribed path, known as buckling induced assembly; next, this pre-buckled structure can suddenly change its bending direction at some threshold points when compressing its apex to the other side. We find that the hemispherical gridshell can undergo snap-through buckling through two different paths based on two different apex loading conditions. The first critical snap-through point slightly increases as the number of rods in gridshell structure becomes denser, which emphasizes the mechanically nonlocal property in hollow grids, in contrast to the local response of continuum shells. The findings may bridge the gap among rods, grids, knits, and shells, for a fundamental understanding of a group of thin elastic structures, and inspire the design of novel micro-electro-mechanical systems and functional metamaterials.

Experimental and numerical studies of bolted joints subjected to torsional excitation

2018 ◽  
Vol 32 (34n36) ◽  
pp. 1840083 ◽  
Author(s):  
Xuetong Liu ◽  
Jianhua Liu ◽  
Huajiang Ouyang ◽  
Zhenbing Cai ◽  
Jinfang Peng ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Hysteresis Loops ◽  
Element Model ◽  
Bolted Joints ◽  
Torsional Angle ◽  
Numerical Studies ◽  
Dimensional Finite Element ◽  
Torsional Excitation ◽  
Three Dimensional Finite Element ◽  
Angular Amplitude

The dynamic response of bolted joints subjected to torsional excitation is investigated experimentally and numerically. First, the effects of the initial preload and the angular amplitude on axial force loss of the bolt were studied. Second, the change of hysteresis loops with the increasing number of loading cycles was found under a larger torsional angle. At last, a fine-meshed three-dimensional finite element model was built to simulate the bolted joint under torsional excitation, from which the hysteresis loops were obtained under varying angular amplitudes. The results of numerical analysis are in good agreement with those of experiments.

scholarly journals FEM using projection of physical properties suitable for movement modeling and optimization processes

2020 ◽  
Vol 39 (5) ◽  
pp. 1185-1199
Author(s):  
Baptiste Ristagno ◽  
Dominique Giraud ◽  
Julien Fontchastagner ◽  
Denis Netter ◽  
Noureddine Takorabet ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Transient State ◽  
Mathematical Function ◽  
Processing Unit ◽  
Time Saving ◽  
Content Type ◽  
Central Processing ◽  
Cpu Time ◽  
Simple Geometry ◽  
Evaluation Time

Purpose Optimization processes and movement modeling usually require a high number of simulations. The purpose of this paper is to reduce global central processing unit (CPU) time by decreasing each evaluation time. Design Methodology Approach Remeshing the geometry at each iteration is avoided in the proposed method. The idea consists in using a fixed mesh on which functions are projected to represent geometry and supply. Findings Results are very promising. CPU time is reduced for three dimensional problems by almost a factor two, keeping a low relative deviation from usual methods. CPU time saving is performed by avoiding meshing step and also by a better initialization of iterative resolution. Optimization, movement modeling and transient-state simulation are very efficient and give same results as usual finite element method. Research Limitations Implications The method is restricted to simple geometry owing to the difficulty of finding spatial mathematical function describing the geometry. Moreover, a compromise between imprecision, caused by the boundary evaluation, and time saving must be found. Originality Value The method can be applied to optimize rotating machines design. Moreover, movement modeling is performed by shifting functions corresponding to moving parts.

scholarly journals Experimental Investigation of Rate-Dependent Inner Hysteresis Loops in PZT

2005 ◽  
Vol 881 ◽  
Author(s):  
Alexander York ◽  
Stefan Seelecke
Keyword(s):  
Experimental Investigation ◽  
Systematic Study ◽  
Domain Switching ◽  
Piezoelectric Materials ◽  
Relaxation Times ◽  
Hysteresis Loops ◽  
Loading Rates ◽  
Rate Dependent ◽  
Realistic Modeling ◽  
Kinetics Of

AbstractThe rate-dependence of piezoelectric materials resulting from the kinetics of domain switching is an important factor that needs to be included in realistic modeling attempts. This paper provides a systematic study of the rate-dependent hysteresis behavior of a commercially available PZT stack actuator. Experiments covering full as well as minor loops are conducted at different loading rates with polarization and strain recorded. In addition, the creep behavior at different constant levels of the electric field is observed. This provides evidence of kinetics being characterized by strongly varying relaxation times that can be associated with different switching mechanisms.

Texture Evolution Induced by Electric Field in Piezoelectric Ceramics

2000 ◽  
Author(s):  
Shan Wan ◽  
Keith J. Bowman
Keyword(s):  
Lead Zirconate Titanate ◽  
Piezoelectric Ceramic ◽  
Domain Switching ◽  
Texture Evolution ◽  
Three Dimensional ◽  
Piezoelectric Ceramics ◽  
Orientation Distribution ◽  
Lead Zirconate ◽  
Domain Orientation ◽  
Poling Direction

Abstract Piezoelectricity is strongly dependent on the preferred domain orientation. A fiber-like texture of a Navy VI Lead Zirconate Titanate (PZT) piezoelectric ceramic can be induced by electric poling. This texture can be further changed and strengthened by cross-poling, that is, applying a strong electrical field perpendicular to the original poling direction. In this paper we show preferred domain orientation changes and anisotropy transitions associated with poling and cross-poling in PZT piezoelectric ceramic. The poling and cross-poling induced textures can be explained by three-dimensional orientation dependent domain switching. Based on this discussion, we demonstrate that it is possible to tailor the preferred domain orientation distribution and improve anisotropic properties of piezoelectric ceramics by directional control of the 90° domain switching using cross-poling.

On approach to determine the internal potential and gravitational energy of ellipsoid

2021 ◽  
Vol 8 (3) ◽  
pp. 359-367
Author(s):  
М. M. Fys ◽  
◽  
А. M. Brydun ◽  
М. I. Yurkiv ◽  
◽  
...  
Keyword(s):  
Distribution Function ◽  
Mass Distribution ◽  
Special Form ◽  
Iterative Process ◽  
Three Dimensional ◽  
Gravitational Energy ◽  
One Dimensional ◽  
Piecewise Continuous ◽  
The Masses ◽  
Internal Potential

Formulas are derived for the calculation of the potential of bodies, which surface is a sphere or an ellipsoid, and the distribution function has a special form: a piecewise continuous one-dimensional function and a three-dimensional mass distribution. For each of these cases, formulas to calculate both external and internal potentials are derived. With their help, further the expressions are given for calculation of the potential (gravitational) energy of the masses of such bodies and their corresponding distributions. For spherical bodies, the exact and approximate relations for determining the energy are provided, which makes it possible to compare the iterative process and the possibility of its application to an ellipsoid. The described technique has been tested by a specific numerical example.

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