scholarly journals Fractal and Fractional Derivative Modelling of Material Phase Change

2020 ◽  
Vol 4 (3) ◽  
pp. 46
Author(s):  
Harry Esmonde
Keyword(s):  
Transfer Functions ◽  
Type Model ◽  
Material Structure ◽  
Iterative Approach ◽  
Response Functions ◽  
Physical Processes ◽  
Ethyl Vinyl ◽  
Solid Models ◽  
Liquid Type ◽  
Model Phase

An iterative approach is taken to develop a fractal topology that can describe the material structure of phase changing materials. Transfer functions and frequency response functions based on fractional calculus are used to describe this topology and then applied to model phase transformations in liquid/solid transitions in physical processes. Three types of transformation are tested experimentally, whipping of cream (rheopexy), solidification of gelatine and melting of ethyl vinyl acetate (EVA). A liquid-type model is used throughout the cream whipping process while liquid and solid models are required for gelatine and EVA to capture the yield characteristic of these materials.

Thickness Deformation of Constrained Layer Damping: An Experimental and Theoretical Evaluation

2000 ◽  
Vol 123 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Peter Y. H. Huang ◽  
Per G. Reinhall ◽  
I. Y. Shen ◽  
Jessica M. Yellin
Keyword(s):  
Mathematical Model ◽  
Transfer Functions ◽  
Viscoelastic Layer ◽  
Experimental Setup ◽  
Experimental Measurements ◽  
Constrained Layer Damping ◽  
Response Functions ◽  
Theoretical Evaluation ◽  
Calculated Frequency ◽  
Direct Measurements

This paper presents a study of thickness deformation of the viscoelastic material in constrained layer damping (CLD) treatments. The first goal of the study is to demonstrate the feasibility of using direct measurement to investigate thickness deformation in CLD treatments. The experimental setup consisted of a constrained layer beam cantilevered to a shaker, an accelerometer mounted at the cantilevered end, and two laser vibrometers that simultaneously measured the responses of the base beam and the constraining layer, respectively, at the free end. A spectrum analyzer calculated frequency response functions (FRFs) between the accelerometer inputs and the vibrometer outputs. Measured FRFs of the base beam and the constraining layer were compared to detect thickness deformation. Experimental results showed that direct measurements can detect thickness deformation as low as 0.5 percent. The second goal is to evaluate the accuracy of a mathematical model developed by Miles and Reinhall [7] that accounts for thickness deformation. FRFs were calculated by using the method of distributed transfer functions by Yang and Tan [13]. Comparison of the numerical results with the experimental measurements indicated that consideration of thickness deformation can improve the accuracy of existing constrained layer damping models when the viscoelastic layer is thick.

scholarly journals THE PROBLEM OF A LACK OF MATERIAL BEHAVIOUR DATA FOR RISK ASSESSMENT

2021 ◽  
pp. 43-56
Author(s):  
I. O. Bondarenko ◽  
L. О. Neduzha
Keyword(s):  
Risk Assessment ◽  
Original Method ◽  
Dynamic Loads ◽  
Railway Track ◽  
Material Structure ◽  
Material Behaviour ◽  
Physical Processes ◽  
Theoretical Support ◽  
Properties Of Materials ◽  
Over Time

Purpose. The main purpose of this work is to provide theoretical support for the need to expand data on changes in the material behaviour under dynamic loads when railway track risk assessment over time due to railway track elements deformability. Methodology. For the research, an original model of railway track design described using the original method based on the ability of elastic waves to propagate energy of power pulses in space and time, as well as a model describing materials as discrete substances were used. Findings. It has been established that the properties of the material affect the deformability of the elements and the design of the railway track; the main parameter in the study of deformability processes is time; material, as a substance, consists of atoms and molecules, and therefore is not continuous; internal physical processes determine changes in the behaviour of the material of an element. Originality. It has been proposed to develop classifications of changes in the physical properties of materials according to the probability of irreversible deformations and the impossibility of deformations, as well as classifications of changes in the mechanical properties of materials according to the probability of the defect appearance and changing the material structure. Practical value. The ability to simulate analytically any physical processes occurring inside elements due to the proposed method allows combining the influence of mechanical and physical effects into a single calculation. This enables to assess the probability of appearing defects in elements under certain dynamic loads when assessing the railway track risk over time due to railway track elements deformability.

A Flexible Rotor on Flexible Bearing Supports: Part I — Stability

1999 ◽  
Author(s):  
José A. Vázquez ◽  
Lloyd E. Barrett ◽  
Ronald D. Flack
Keyword(s):  
Frequency Response ◽  
Transfer Functions ◽  
Structure Stability ◽  
Response Functions ◽  
Support Structure ◽  
Frequency Response Functions ◽  
Vertical Stiffness ◽  
Fluid Film Bearings ◽  
Flexible Supports ◽  
Rigid Supports

Abstract An experimental study of the effects of bearing support flexibility on rotor stability is presented. A flexible roto supported by fluid film bearings on flexible supports was used with fifteen support configurations. The horizontal suppor stiffness was varied systematically while the vertical stiffness was kept constant. The support charactristics were determined experimentally by measuring the frequency response functions of the support structure at the bearing locations. These frequency response functions were used to calculate polynomial transfer functions that represented the support structure. Stability predictions were compared with measured stability thresholds. The predicted stability thresholds agree with the experimental data within a confidence bound for the logarithmic decrement of ±0.01. Predictions for the rotor on rigid supports are included for comparison.

Vehicle Vibration Analysis Using Frequency Domain Techniques

1969 ◽  
Vol 91 (4) ◽  
pp. 1075-1080 ◽  
Author(s):  
W. F. Lins
Keyword(s):  
Frequency Domain ◽  
Transfer Functions ◽  
Frequency Domain Analysis ◽  
Test Case ◽  
Response Functions ◽  
Vehicle Simulation ◽  
Absorbed Power ◽  
The Time Domain ◽  
Comparison Of The Results ◽  
Frequency Domain Techniques

This paper describes a method of determining and evaluating vehicle vibration through frequency-response functions. Human transfer functions and absorbed power are used to investigate the effects of vibration on the human being. The advantages and limitations of frequency domain analysis in contrast to vehicle simulation in the time domain are discussed. A test case showing a series of computer simulations using both techniques is presented, and a comparison of the results is made.

The Hysteretic Damping Model in Vibration Theory

1991 ◽  
Vol 205 (1) ◽  
pp. 23-28 ◽  
Author(s):  
S H Crandall
Keyword(s):  
Transfer Functions ◽  
Impulse Response Functions ◽  
Response Functions ◽  
Hysteretic Damping ◽  
Hysteretic Damper ◽  
Band Limited ◽  
The Time Domain ◽  
Damping Model ◽  
The Ideal

The characterization of damping elements by differential or integral equations relating physical variables by transfer functions in the frequency domain and by impulse response functions in the time domain is carried out for the ideal viscous damper, the ideal hysteretic damper and the band-limited hysteretic damper. It is shown that the latter two models are flawed because they do not satisfy the causality requirement.

scholarly journals Broad-scale climate influences on cod (Gadus morhua) recruitment on Georges Bank

2011 ◽  
Vol 68 (3) ◽  
pp. 592-602 ◽  
Author(s):  
Joachim P. Gröger ◽  
Michael J. Fogarty
Keyword(s):  
Gadus Morhua ◽  
Structural Model ◽  
Transfer Functions ◽  
Atlantic Multidecadal Oscillation ◽  
Information Criteria ◽  
Type Model ◽  
Georges Bank ◽  
Ex Post ◽  
Climate Influences ◽  
Broad Scale

AbstractGröger, J. P., and Fogarty, M. J. 2011. Broad-scale climate influences on cod (Gadus morhua) recruitment on Georges Bank. – ICES Journal of Marine Science, 68: . Climatic influences on Georges Bank cod recruitment were investigated using the North Atlantic Oscillation (NAO) as an index of atmospheric variability and the Atlantic Multidecadal Oscillation (AMO) as an index of sea surface temperature. A quantitative approach based on a simple Cushing-type stock–recruitment model was developed and extended to include climate influences using the technique of generalized transfer functions (ARIMAX modelling). This allowed the autoregressive nature of the interacting exogenous and endogenous processes to be taken into account. Based on two information criteria, the resulting best transfer function contains winter NAO with a lag of 3 years, annual AMO with a lag of 1 year (both as exogenous climate factors), loge(spawning-stock biomass) as a structural model component, plus two autoregressive parameters. The model is characterized by the smallest information criteria, 92% of explained recruitment variation (vs. 55% from the simple Cushing-type model), excellent forecasting behaviour, and all model assumptions being fulfilled. It is proposed that the model's recruitment hindcasts (ex post forecasts) and forecasts be incorporated into stock and risk assessments as well as management strategy evaluations, either as a climate-induced recruitment index for projections or as real forecasts to establish sustainable cod fisheries on Georges Bank conditioned by climate as a forcing factor.

Software Application of Material Structure Prediction

2017 ◽  
Vol 906 ◽  
pp. 88-94
Author(s):  
Y.E. Karyakin ◽  
I.Y. Karyakin ◽  
Svetlana V. Karyakina
Keyword(s):  
Structure Prediction ◽  
Computer Experiments ◽  
Recognition Algorithm ◽  
Material Structure ◽  
Kinematic Parameters ◽  
Tempering Temperature ◽  
Software Application ◽  
Thermokinetic Diagrams ◽  
Time Expenditures ◽  
Model Phase

The developed software application allows the user to model phase transformations under isothermal conditions for a specified steel grade at arbitrary tempering temperature. Architecture of the software application using scheme of the chart of distributed computation of simulation model kinematic parameters for reducing time expenditures during computer experiments. The recognition algorithm of raster images on the isothermal and thermokinetic diagrams has been proposed. The imaging algorithm of the material structure after heat treatment have been developed.

N-Wave Runup Statistics at Surf Zone Using Boussinesq-Type Model

2012 ◽  
Author(s):  
J. M. Chen ◽  
D. Liang ◽  
R. Rana
Keyword(s):  
Surf Zone ◽  
Extreme Event ◽  
Tsunami Wave ◽  
Type Model ◽  
Strongly Correlated ◽  
Wave Runup ◽  
Physical Processes ◽  
Large Wave ◽  
Wave Effects ◽  
N Wave

A TVD Lax-Wendroff scheme solves the Boussinesq-type equations is presented, extensively validated, and clearly demonstrated to be a robust and efficient engineering tool to simulate the physical processes involved in the tsunami wave runup and interaction of the propagating solitary waves with the idealized coastal beaches. To better understand the physical processes of the tsunami wave runup at surf zone, a parametric study concerning N-wave runup is carried out. For all cases investigated, the qualitative features of the propagating N-waves remain unaltered, even for the large wave events. The relative maximum runup height and wave steepness are found to be strongly correlated and appeared to be linearly asymptotic in form. Also, the severity of extreme wave attack is found to be a function of beach slope for a given extreme event. The numerical simulations reveal the significance of the nonlinear wave effects on the predicted maximum N-wave runup heights, which provide guidance in selecting the design height of coastal defence structures and specifying the clearance distance between the shoreline and infrastructure.

scholarly journals Recharge Response Functions

1997 ◽  
Vol 1 (1) ◽  
pp. 47-53 ◽  
Author(s):  
A. Calver
Keyword(s):  
Water Level ◽  
Unsaturated Zone ◽  
Transfer Functions ◽  
Unconfined Aquifer ◽  
Water Levels ◽  
Great Change ◽  
Response Functions ◽  
Saturated Zone ◽  
England And Wales ◽  
Practical Analysis

Abstract. This paper explores the establishment of transfer functions for describing the annual oscillation of unconfined aquifer water levels in response to effective precipitation. A simple saturated zone representation is developed to accompany the unsaturated zone mechanism. Practical examples are drawn from a sample of sites from the chalk and the Permo-Triassic sandstones of England and Wales. Modelled water levels are in many cases good. The technique is most appropriate within the usual range of fluctuation of aquifer water level, with no great change in influence of abstractions, and when it is acceptable to approximate the complexity of unsaturated zone processes in practical analysis.

Sign in / Sign up

Export Citation Format

Share Document