Efficient Steady-State Computation for Wear of Multimaterial Composites

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Florian Feppon ◽  
Mark A. Sidebottom ◽  
Georgios Michailidis ◽  
Brandon A. Krick ◽  
Natasha Vermaak
Keyword(s):  
Steady State ◽  
Optimization Design ◽  
Iterative Scheme ◽  
Parabolic Partial Differential Equation ◽  
Iterative Schemes ◽  
Foundation Model ◽  
Final Steady State ◽  
Inverse Rule ◽  
And Control ◽  
Two Parameter

Traditionally, iterative schemes have been used to predict evolving material profiles under abrasive wear. In this work, more efficient continuous formulations are presented for predicting the wear of tribological systems. Following previous work, the formulation is based on a two parameter elastic Pasternak foundation model. It is considered as a simplified framework to analyze the wear of multimaterial surfaces. It is shown that the evolving wear profile is also the solution of a parabolic partial differential equation (PDE). The wearing profile is proven to converge to a steady-state that propagates with constant wear rate. A relationship between this velocity and the inverse rule of mixtures or harmonic mean for composites is derived. For cases where only the final steady-state profile is of interest, it is shown that the steady-state profile can be accurately and directly determined by solving a simple elliptic differential system—thus avoiding iterative schemes altogether. Stability analysis is performed to identify conditions under which an iterative scheme can provide accurate predictions and several comparisons between iterative and the proposed formulation are made. Prospects of the new continuous wear formulation and steady-state characterization are discussed for advanced optimization, design, manufacturing, and control applications.

Reduced substrate oxidation in postischemic myocardium: 13C and 31P NMR analyses

1990 ◽  
Vol 258 (5) ◽  
pp. H1357-H1365 ◽  
Author(s):  
E. D. Lewandowski ◽  
D. L. Johnston
Keyword(s):  
Steady State ◽  
31P Nmr ◽  
Tca Cycle ◽  
High Energy ◽  
Substrate Oxidation ◽  
High Energy Phosphates ◽  
Atp Content ◽  
And Control ◽  
13C And 31P Nmr ◽  
Postischemic Myocardium

13C and 31P nuclear magnetic resonance (NMR) spectra were used to assess substrate oxidation and high-energy phosphates in postischemic (PI) isolated rabbit hearts. Phosphocreatine (PCr) increased in nonischemic controls on switching from glucose perfusion to either 2.5 mM [3-13C]pyruvate (120%, n = 7) or [2-13C]acetate (114%, n = 8, P less than 0.05). ATP content, oxygen consumption (MVO2), and hemodynamics (dP/dt) were not affected by substrate availability in control or PI hearts. dP/dt was 40-60% lower in PI hearts during reperfusion after 10 min ischemia. Hearts reperfused with either pyruvate (n = 11) or acetate (n = 8) regained preischemic PCr levels within 45 s. Steady-state ATP levels were 55-70% of preischemia with pyruvate and 52-60% with acetate. Percent maximum [4-13C]glutamate signal showed reduced conversion of pyruvate to glutamate via the tricarboxylic acid (TCA) cycle at 4-min reperfusion (PI = 24 +/- 4%, means +/- SE; Control = 48 +/- 4%). The increase in 13C signal from the C-4 position of glutamate was similar to control hearts within 10.5 min. The increase in [4-13C]glutamate signal from acetate was not different between PI and control hearts. The ratio of [2-13C]Glu:[4-13C]Glu, reflecting TCA cycle activity, was reduced in PI hearts with acetate for at least 10 min (Control = 0.76 +/- 0.03; PI = 0.51 +/- 0.09) until steady state was reached. Despite rapid recovery of oxidative phosphorylation, contractility remained impaired and substrate oxidation was significantly slowed in postischemic hearts.

scholarly journals A SIMPLE FIVE-STEP METHODOLOGY TO DETERMINE CONTROLLABILITY OF HEAT EXCHANGER NETWORKS USING STEADY-STATE INFORMATION

2011 ◽  
Author(s):  
Rodolfo Tellez ◽  
William Y. Svrcek ◽  
Brent R. Young
Keyword(s):  
Steady State ◽  
Heat Exchanger ◽  
Process Integration ◽  
Plant Design ◽  
State Information ◽  
Step Procedure ◽  
Heat Exchanger Networks ◽  
Propose Control Strategy ◽  
Optimum Heat ◽  
And Control

Process integration design methodologies have been developed and introduced to synthesise an optimum heat exchanger network (HEN) arrangement. However, controllability issues are often overlooked during the early stages of a plant design. In this paper we present a five-step procedure that involves the use of multivariable disturbance and control analyses based solely on steady-state information and with the purpose to assess process design developments and to propose control strategy alternatives appropriate and suitable for a HEN.

scholarly journals Off-Design Behavior Analysis and Operating Curve Design of Marine Intercooled Gas Turbine

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Nian-kun Ji ◽  
Shu-ying Li ◽  
Zhi-tao Wang ◽  
Ning-bo Zhao
Keyword(s):  
Steady State ◽  
Gas Turbine ◽  
Optimization Design ◽  
Three Dimensional ◽  
Operational Flexibility ◽  
Modeling And Analysis ◽  
Additional Degree ◽  
Performance Space ◽  
Mechanical Constraints ◽  
Steady State Model

The intercooled gas turbine obtained by adopting an indirect heat exchanger into an existing gas turbine is one of the candidates for developing high-power marine power units. To simplify such a strong coupled nonlinear system reasonably, the feasibility and availability of qualifying equivalent effectiveness as the only parameter to evaluate the intercooler behavior are investigated. Regarding equivalent effectiveness as an additional degree of freedom, the steady state model of a marine intercooled gas turbine is developed and its off-design performance is analyzed. With comprehensive considerations given to various phase missions of ships, operational flexibility, mechanical constraints, and thermal constraints, the operating curve of the intercooled gas turbine is optimized based on graphical method in three-dimensional performance space. The resulting operating curve revealed that the control strategy at the steady state conditions for the intercooled gas turbine should be variable cycle control. The necessity of integration optimization design for gas turbine and intercooler is indicated and the modeling and analysis method developed in this paper should be beneficial to it.

scholarly journals A frequency quantum interpretation of the surface renewal model of mass transfer

2017 ◽  
Vol 4 (7) ◽  
pp. 170103 ◽  
Author(s):  
Chanchal Mondal ◽  
Siddharth G. Chatterjee
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Frequency Distribution ◽  
Age Distribution ◽  
Gas Absorption ◽  
Bulk Liquid ◽  
Gas Transfer ◽  
Transfer Resistance ◽  
Surface Renewal ◽  
Two Parameter

The surface of a turbulent liquid is visualized as consisting of a large number of chaotic eddies or liquid elements. Assuming that surface elements of a particular age have renewal frequencies that are integral multiples of a fundamental frequency quantum, and further assuming that the renewal frequency distribution is of the Boltzmann type, performing a population balance for these elements leads to the Danckwerts surface age distribution. The basic quantum is what has been traditionally called the rate of surface renewal. The Higbie surface age distribution follows if the renewal frequency distribution of such elements is assumed to be continuous. Four age distributions, which reflect different start-up conditions of the absorption process, are then used to analyse transient physical gas absorption into a large volume of liquid, assuming negligible gas-side mass-transfer resistance. The first two are different versions of the Danckwerts model, the third one is based on the uniform and Higbie distributions, while the fourth one is a mixed distribution. For the four cases, theoretical expressions are derived for the rates of gas absorption and dissolved-gas transfer to the bulk liquid. Under transient conditions, these two rates are not equal and have an inverse relationship. However, with the progress of absorption towards steady state, they approach one another. Assuming steady-state conditions, the conventional one-parameter Danckwerts age distribution is generalized to a two-parameter age distribution. Like the two-parameter logarithmic normal distribution, this distribution can also capture the bell-shaped nature of the distribution of the ages of surface elements observed experimentally in air–sea gas and heat exchange. Estimates of the liquid-side mass-transfer coefficient made using these two distributions for the absorption of hydrogen and oxygen in water are very close to one another and are comparable to experimental values reported in the literature.

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

1998 ◽  
Vol 120 (2) ◽  
pp. 405-409 ◽  
Author(s):  
P. Monmousseau ◽  
M. Fillon ◽  
J. Freˆne
Keyword(s):  
Steady State ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Tilting Pad ◽  
Transient Period ◽  
Final Steady State ◽  
Tilting Pad Journal Bearings

Nowadays, tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady state to a final steady state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions, and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD, and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws < 1, Fdyn/Ws = 1 and Fdyn//Ws > 1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature, and the shaft orbit is presented. The final steady state is obtained a long time after the appearance of a dynamic load.

On Nonlinear Dynamics and Control of a Particular Portal Frame Foundation Model, Excited by a Non-Ideal Motor

2003 ◽  
Vol 440-441 ◽  
pp. 371-380 ◽  
Author(s):  
José Manoel Balthazar ◽  
Jorge Luis Palacios Felix ◽  
Reyolando Manoel Lopes Rabelo da Fonseca Brasil
Keyword(s):  
Nonlinear Dynamics ◽  
Portal Frame ◽  
Foundation Model ◽  
Dynamics And Control ◽  
And Control ◽  
Nonlinear Dynamics And Control

scholarly journals Convergence of Infinite Family of Multivalued Quasi-Nonexpansive Mappings Using Multistep Iterative Processes

2014 ◽  
Vol 2014 ◽  
pp. 1-11
Author(s):  
Renu Chugh ◽  
Sanjay Kumar
Keyword(s):  
Real Banach Space ◽  
Iterative Scheme ◽  
Nonexpansive Mappings ◽  
Infinite Family ◽  
Finite Family ◽  
Countable Family ◽  
Uniformly Convex ◽  
Iterative Schemes ◽  
Strong And Weak Convergence ◽  
Convergence Results

We prove strong and weak convergence results using multistep iterative sequences for countable family of multivalued quasi-nonexpansive mappings by using some conditions in uniformly convex real Banach space. The results presented extended and improved the corresponding result of Zhang et al. (2013), Bunyawat and Suantai (2012), and some others from finite family, one countable family, and two countable families tok-number of countable families of multivalued quasi-nonexpansive mappings. Also we used a numerical example in C++ computational programs to prove that the iterative scheme we used has better rate of convergence than other existing iterative schemes.

Experimental Evaluation of a Steady-State Model for the Wear of Particle-Filled Polymer Composite Materials

1997 ◽  
Vol 119 (4) ◽  
pp. 694-699 ◽  
Author(s):  
Sung Won Han ◽  
Thierry A. Blanchet
Keyword(s):  
Steady State ◽  
Composite Materials ◽  
Wear Rate ◽  
Polymer Composite ◽  
Wear Behavior ◽  
Polymer Composite Materials ◽  
Volume Fractions ◽  
Rule Of Mixtures ◽  
Filler Particles ◽  
Inverse Rule

A model for the steady-state wear behavior of polymer composite materials, including the effects of preferential load support by and surface accumulation of wear-resistant filler particles, is further developed. It is shown that the resultant inverse rule-of-mixtures description of steady-state composite wear rate behavior is independent of the assumed form of filler contact pressure, though preferential load support does affect the degree of surface accumulation of filler particles that occurs. The validity of these descriptions of steady-state wear behavior and surface accumulation as functions of bulk filler volume fraction are investigated by experiments with copper particle-filled PTFE composites for bulk filler volume fractions from 0 to 40 percent. The applicability of the description of surface accumulation for this composite system was limited to bulk filler volume fractions less than 20 percent, a hypothesized result of transition in load-sharing between filler and matrix. The inverse rule-of-mixtures description of steady-state wear rate, however, was maintained over the full range of volume fractions investigated.

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