Design Optimization of Beams With Multi-Layers of Corrugations

2015 ◽  
Author(s):  
W. N. Cheng ◽  
C. C. Cheng
Keyword(s):  
Dynamic Characteristic ◽  
Frequency Equation ◽  
Optimal Number ◽  
Modeling Technique ◽  
Original Design ◽  
Reduction System ◽  
Straight Beam ◽  
Impedance Modeling ◽  
Corrugated Beam ◽  
Force Equilibrium

Optimal designs of beams with multi-layers of corrugations are introduced in this paper. The dynamic characteristic of corrugated structures is investigated firstly using the impedance modeling technique. The dynamic response of a beam with layers of corrugations is formulated by dividing a corrugated beam into two kinds of structural segments: one, the corrugation modeled as a curved beam using finite element method and the other, the liner treated as a straight beam formulated analytically. Then the frequency equation is derived by assembling the impedance of each structure segment based on conditions of force equilibrium and velocity compatibility. The accuracy of the impedance modeling technique are compared to different existing methods, e.g. FEM, Guyan reduction, improved reduction system (IRS), improved reduction system (DIRS), and iterative improved reduction system (IIRS). Finally, examples of optimal design of corrugated beams are presented. Results further show that with an optimal number of corrugated layers and optimal thickness of liner and medium of each layer, the corrugated beam has a desirable dynamic characteristic, e.g. the first bending natural frequency may increase 40% as compared to that of the original design.

Dynamic Beam Modification Using Dimples

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
W. N. Cheng ◽  
C. C. Cheng ◽  
G. H. Koopmann
Keyword(s):  
Natural Frequencies ◽  
Design Method ◽  
Frequency Equation ◽  
Search Method ◽  
The Other ◽  
Impedance Method ◽  
Dimple Size ◽  
Straight Beam ◽  
Novel Method ◽  
Force Equilibrium

In this paper, a design method to modify the vibration characteristics of a beam by creating cylindrical dimples on its surface is investigated. In particular, the vibration response of a beam with several dimples is formulated using the impedance method. The dimpled beam is divided into two kinds of structural segments: one, a curved beam that is modeled as the dimple and the other, a straight beam. The frequency equation is derived by assembling the impedance of each structure segment based on conditions of force equilibrium and velocity compatibility. Then a novel method for shifting the natural frequencies of a beam to preassigned values by creating cylindrical dimples on this structure is introduced. The dimple size and its location on the structure can be determined analytically, so the time consuming process using the traditional optimal search method is thereby avoided. Several examples using this technique are demonstrated.

Natural Frequencies and Band Gaps of Periodically Corrugated Beams

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Rhamy Salim Bachour ◽  
Rodrigo Nicoletti
Keyword(s):  
Natural Frequencies ◽  
Periodic Structures ◽  
Dynamic Properties ◽  
Band Gaps ◽  
Transverse Waves ◽  
Large Bandwidth ◽  
Straight Beam ◽  
Propagating Waves ◽  
Corrugated Beam ◽  
Straight Segments

Abstract Structures with geometric periodicity can present interesting dynamic properties like stop and pass frequency bands. In this case, the geometric periodicity has the effect of filtering the propagating waves in the structure, in a similar way to that of phononic crystals and metamaterials (non-homogeneous materials). Hence, by adopting such structures, we can design systems that present dynamic characteristics of interest, e.g., with minimum dynamic response in a given frequency range with large bandwidth. In the present work, we show that corrugated beams also present the dynamic properties of periodic structures due to their periodic geometry only (no need of changing mass or material properties along the beam). Two types of corrugated beams are studied analytically: beams with curved bumps of constant radii and beams with bumps composed of straight segments. The results show that, as we change the proportions of the bump, the natural frequencies change and tend to form large band gaps in the frequency spectrum of the beam. Such shifting of the natural frequencies is related to the coupling between longitudinal and transverse waves in the curved beam. The results also show that it is possible to predict the position and the limits of the first band gap (at least) as a function of the fundamental frequency of the straight beam (without bumps), irrespective of the total length of the corrugated beam.

Advanced Supervision and Diagnostic System: The Tool for Improvement Reliability and Efficiency of Utility Boilers Burned Different Coals Type

2007 ◽  
Author(s):  
B. Chudnovsky ◽  
B. Kogan ◽  
A. Talanker ◽  
Y. Sella ◽  
J. Cohen
Keyword(s):  
Production Management ◽  
Flame Temperature ◽  
Optimal Number ◽  
Nox Emission ◽  
Plant Performance ◽  
Electricity Production ◽  
Maintenance Cost ◽  
Original Design ◽  
On Line ◽  
Coal Type

Due to the past years experience, we have seen an influence on the coal purchase policies. The main reason for using coal other tan the original design coal, apart from economic considerations, is to reduce SO2 emission by using a low sulfur content coal as well as decreasing coal index (fixed carbon to volatile matter ratio) in order to reduce NOx emission etc. Hence, the power generation plant was originally designed to operate on a particular coal, and due to high restriction in environmental requirements, emissions regulations, have led to modifications of the coal type and firing mode, while the boilers must burn a different coal type and its blends. It may lead to boiler reliability degradation and as a result reducing the power plant availability and increasing operating and maintenance cost. In order to prevent a different faults in boiler operation and as a result a reliability reduction, special monitoring and diagnostic techniques is required for engineering analysis and utility production management. In this sense an on-line supervision system have developed and implemented for 575, 550, 360 Mw coal fired units. The aim of the system is to achieve more effective and reliable operation with emission reduction. It is a valuable aid for: (1) operation staff and process engineers to survey the equipment and overall plant performance, (2) electricity production management in order to implement maintenance and operation strategies. The developed system provides an on-line information regards furnace performance, including fireball location, increase in furnace exit temperature indicates that it’s necessity to activate furnace sootblowers to control steam temperatures and prevent excessive accumulations of slag and heat surfaces tube overheating. The developed system indicates the superheater and reheater surfaces midwall metal temperature which provides timely information to assist engineering personnel to optimize mode of operation, in order to activate the optimal number of sootblowing of the corresponded surfaces, etc. The system includes also an online analysis of the erosion impact on the boiler backpass heat surfaces. By the using the developed system we found a correlation between furnace fouling and NOx emission due to the effect of flame temperature on the rate of NOx formation. As a result an optimal mode of furnace operation and sootblowing practice is used to reduce the high cost of controlling NOx emission. The developed system allows to fond the proper coal blends which provide a high boiler efficiency and reliability while minimizing NOx emissions.

A generic impedance modeling technique

2020 ◽  
Vol 123 ◽  
pp. 153301
Author(s):  
Abdulwadood Al-Ali ◽  
Ahmed Elwakil ◽  
Brent Maundy ◽  
David Westwick
Keyword(s):  
Modeling Technique ◽  
Impedance Modeling

Impedance Modeling Technique for a Fluid-Loaded Structure

AIAA Journal ◽  
2005 ◽  
Vol 43 (11) ◽  
pp. 2454-2465
Author(s):  
C. C. Cheng ◽  
P. W. Wang
Keyword(s):  
Modeling Technique ◽  
Impedance Modeling ◽  
Loaded Structure

Optimal Experimental Design With Nesting of Persons in Organizations

2013 ◽  
Vol 221 (3) ◽  
pp. 145-159 ◽  
Author(s):  
Gerard J. P. van Breukelen
Keyword(s):  
Repeated Measures ◽  
Optimal Number ◽  
Health Centers ◽  
Randomized Experiments ◽  
Optimal Sample ◽  
Treatment Conditions ◽  
Sampling Cost ◽  
Nested Designs ◽  
Simple Equations ◽  
Number Of Individuals

This paper introduces optimal design of randomized experiments where individuals are nested within organizations, such as schools, health centers, or companies. The focus is on nested designs with two levels (organization, individual) and two treatment conditions (treated, control), with treatment assignment to organizations, or to individuals within organizations. For each type of assignment, a multilevel model is first presented for the analysis of a quantitative dependent variable or outcome. Simple equations are then given for the optimal sample size per level (number of organizations, number of individuals) as a function of the sampling cost and outcome variance at each level, with realistic examples. Next, it is explained how the equations can be applied if the dependent variable is dichotomous, or if there are covariates in the model, or if the effects of two treatment factors are studied in a factorial nested design, or if the dependent variable is repeatedly measured. Designs with three levels of nesting and the optimal number of repeated measures are briefly discussed, and the paper ends with a short discussion of robust design.

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