scholarly journals Parametric Study and Uncertainty Quantification of the Nonlinear Modal Properties of Frictional Dampers

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Yekai Sun ◽  
Jie Yuan ◽  
Luca Pesaresi ◽  
Enora Denimal ◽  
Loïc Salles
Keyword(s):  
Contact Angle ◽  
Damping Ratio ◽  
Energy Levels ◽  
Design Stage ◽  
Design Parameters ◽  
Vertical Position ◽  
Beam Model ◽  
Friction Damper ◽  
Resonant Amplitude ◽  
Two Parameters

Abstract A numerical methodology is described to study the influence of the contact location and contact condition of friction damper in aircraft engines. A simplified beam model is used to represent the blade for the preliminary design stage. The frictional damper is numerically analyzed based on two parameters, contact angle and vertical position of the platform. The nonlinear modal analysis is used to investigate the nonlinear dynamic behavior and damping performances of the system. The harmonic balanced method with the continuation technique is used to compute the nonlinear modes for a large range of energy levels. By using such a modeling strategy, the modal damping ratio, resonant amplitude, and resonant frequency are directly and efficiently computed for a range of design parameters. Monte Carlo simulations together with Latin hypercube sampling is then used to assess the robustness of the frictional damper, whose contact parameters involve much uncertainties due to manufacturing tolerance and also wear effects. The influences of those two parameters are obtained, and the best performances of the frictional damper can be achieved when the contact angle is around 25 deg–30 deg. The vertical position of the platform is highly mode dependent, and other design considerations need to be accounted. The results have proved that the uncertainties that involved contact surfaces do not have significant effects on the performance of frictional damper.

Response Comparisons of a Large Floating Structure by Grillage and Shell FE Models

2008 ◽  
Author(s):  
Kazuhiro Iijima ◽  
Junghyun Kim ◽  
Tetsuya Yao
Keyword(s):  
Stress Responses ◽  
Three Dimensional ◽  
Design Stage ◽  
Design Parameters ◽  
Beam Model ◽  
Floating Structure ◽  
Response Level ◽  
Design Work ◽  
Early Design ◽  
Early Design Stage

At the early design stage of a large floating structure, it is firstly important to know the hydroelastic response characteristics in waves. For this purpose, the structure is modeled by three-dimensional grillage, and hydroelastic analysis is performed in order to estimate the overall behaviour. At this stage, main design parameters are: floater shapes, their arrangement and rigidity distributions. They are optimized by referencing to the hydroelastic responses estimated by the analysis. As the design work develops, more detailed modelling is possible. At the final design stage, the design must be confirmed by checking the response against criteria. The structure is re-modeled by shell FE elements for skin structures and beam elements for stiffeners. It is considered that the more correct estimations are performed by employing the refined model. However, there might be significant differences in the modelling and also in the resultant estimations between the first and final stages even when the subject structure is identical. Then, it is necessary to evaluate the differences between the results estimated by using these two models in order to assure the actual response level estimated by using the beam model at the early design stage. In this paper, three-dimensional grillage and shell FE structural models of a large floating structure are prepared. Hydroelastic analyses are performed on the two models. The results are compared in terms of motion, member force and stress responses.

scholarly journals Theoretical Investigation on the Impact of Two HDR Dampers on First Modal Damping Ratio of Stay Cable

2021 ◽  
Vol 11 (22) ◽  
pp. 10985
Author(s):  
Duy Thao Nguyen ◽  
Duy Hung Vo ◽  
Md. Naimul Haque
Keyword(s):  
Large Amplitude ◽  
Damping Ratio ◽  
Magnetorheological Damper ◽  
Design Parameters ◽  
Friction Damper ◽  
Stay Cable ◽  
Modal Damping Ratio ◽  
Stay Cables ◽  
High Damping Rubber ◽  
The Impact

Stay cables are one of the vital components of a cable-stayed bridge. Due to their flexible nature, stay cables are vulnerable to external excitation and often vibrate with large amplitude under wind action which leads to the fatigue failure of the cables. To suppress such kind of large amplitude vibration by improving the damping ratio of the cable various dampers such as magnetorheological damper, friction damper; oil damper; or high damping rubber (HDR) damper are utilized and gained popularity over time. This paper focuses on improving the damping ratio of stay cables using a combination of two HDR dampers. First, the theoretical model is formulated considering cable bending stiffness to evaluate the damping effect of cable-HDR dampers system. Then, the impact of various design parameters of HDR dampers on cable damping considering the cable stiffness is performed. The comparative analysis of results shows that the considered parameters such as loss factor, spring factor, and installation location of dampers have much effect on the stay cables damping ratio. Finally, the optimal parameters of the two HDR dampers are proposed for damper design.

Design Tools to the Best Coupling of Dry-Friction Solid Underplatform Dampers to Turbine Blades

2019 ◽  
Author(s):  
Chiara Gastaldi ◽  
Muzio M. Gola
Keyword(s):  
Dry Friction ◽  
Turbine Blades ◽  
Contact Forces ◽  
Design Stage ◽  
Design Parameters ◽  
Design Tools ◽  
Friction Damper ◽  
Early Design Stage ◽  
Coupled Dynamic Analysis ◽  
Neck Thickness

Abstract This work completes the recent authors efforts in the frame of solid dampers optimization, whose goal are to develop systematic design tools to identify the best choice of an underplatform damper (shape, size) matching with a blade (size, modal features) in a turbomachine. Step 1 was to filter out all those geometries that would lead to undesirable kinematics and contact forces. Step 2 was to identify those ranges of parameters that are better in terms of added stiffness and damping. The purpose of this third and final step is to complete the picture by exploring how the basic geometrical design parameters of blades interact with the damper parameters and where (i.e., for which parameters combination) a designer may find the best match in view of the vibratory response under resonant excitation. The main focus is on the blades HCF safety. While steps 1 and 2 are based on simple geometrical considerations, this step 3 requires a non-linear coupled dynamic analysis of the system. It is demonstrated how the variation of crucial parameters (e.g. neck thickness, damper geometry, centrifugal force) affects the performance of a real damper coupled to a realistic blade. The method, based on reasonable simplifications, is illustrated and proposed as a tool to make the analysis attractive to designers in the early design stage by guiding their initial choice of an optimal dry friction damper.

A Vibration Damping Analysis Method of Turbine Blade Shroud Dampers Based on a Given Eigen-Mode

2018 ◽  
Author(s):  
Zhao Jiazhe ◽  
Wang Yanrong ◽  
Luo Yanbin ◽  
Zhang Xiaojie
Keyword(s):  
Turbine Blade ◽  
Damping Ratio ◽  
Twist Angle ◽  
Vibration Damping ◽  
Design Parameters ◽  
Slip Model ◽  
Analysis Method ◽  
Friction Damper ◽  
Analysis And Design ◽  
Eigen Mode

High cycle fatigue damage caused by resonance and forced vibration can significantly affect the life and reliability of turbine rotor blades in aero-engines. The friction damper has been widely used to reduce the resonant stress of blades, on which the turbine blade shroud dampers are highly used. In order to solve the problems of vibration damping analysis and design of shrouded blades dampers, an analytical method without complex and time-consuming nonlinear vibration response has been proposed based on a given eigen-mode in this paper. For the serrated shrouded damper, two typical friction models, namely macro-slip model, and micro-slip model, have been introduced. Additionally, a complete set of damping analysis method has been introduced by the energy method, based on the vibration dynamics principle and eigen-mode analyzed by finite element method. Combined with the analysis of the natural vibration characteristics of the shrouded turbine blade, the law of the damping ratio with the relevant design parameters, such as the vibration stress, the pre-twist angle, the friction coefficient and the nodal diameter, was obtained through a calculation example. The method can also provide an important reference for the parameterized design of dampers.

Landfarming of Oily Wastes: Design and Operation

1987 ◽  
Vol 19 (8) ◽  
pp. 75-86 ◽  
Author(s):  
S. P. Amaral
Keyword(s):  
Surface Runoff ◽  
Groundwater Protection ◽  
Quality Monitoring ◽  
Design Stage ◽  
Design Parameters ◽  
Runoff Water ◽  
Oily Waste ◽  
Waste Degradation ◽  
Ground Characterization ◽  
Area Of Application

The technology of treatment through landfarming for oily wastes has been more and more often utilized in Brazil, always successfully. The definition, the processes which occur, as well as the factors which affect its performance are herein presented. Design parameters, such as location, ground characterization, dimensioning of the area of application, groundwater protection, drainage, treatment of surface runoff water and percolated liquid, among others, are presented. Operational procedures and quality monitoring of effluents and environment are also described. PETROBRÁS is already operating two landfarming systems and has several others in the design stage. We present data from these projects and report that oily waste degradation has been achieved in around six months. Finally, we expect to be contributing to the affirmation and development of this technology in our Country.

Optimal Design of Vibration Absorber Systems Supported by Elastic Base

1991 ◽  
Author(s):  
Hashem Ashrafiuon
Keyword(s):  
Dynamic Models ◽  
Damping Ratio ◽  
Equations Of Motion ◽  
Elastic Base ◽  
Design Parameters ◽  
Primary System ◽  
Vibration Absorbers ◽  
Equivalent Damping ◽  
System Equations ◽  
Different Levels

Abstract This paper presents the effect of foundation flexibility on the optimum design of vibration absorbers. Flexibility of the base is incorporated into the absorber system equations of motion through an equivalent damping ratio and stiffness value in the direction of motion at the connection point. The optimum values of the uncoupled natural frequency and damping ratio of the absorber are determined over a range of excitation frequencies and the primary system damping ratio. The design parameters are computed and compared for the rigid, static, and dynamic models of the base as well as different levels of base flexibility.

An Approximate Method for Intact Stability of Fishing Vessels

1999 ◽  
Vol 36 (03) ◽  
pp. 171-174
Author(s):  
Hüseyin Yilmaz ◽  
Abdi Kükner
Keyword(s):  
Design Stage ◽  
Design Parameters ◽  
Preliminary Design ◽  
Ship Stability ◽  
Fishing Vessels ◽  
Initial Stability ◽  
Intact Stability ◽  
Preliminary Design Stage ◽  
Reduce Risk ◽  
Vessel Stability

It is well known that stability is the most important safety requirement for ships. One should have some information on ship stability at the preliminary design stage in order to reduce risk. Initial stability of ships is an important criterion and can be closely evaluated in terms of form parameters and vertical center of gravity. In this study, using some sample ship data, approximate formulations are derived by means of regression analysis for the calculations expressed in terms of ship preliminary design parameters that can easily provide approximate GM calculations. Thus designers can be provided with ship stability at the preliminary design stage, and also a set of appropriate design parameters for improving vessel stability can easily be determined.

scholarly journals An Approximate Method for Calculation of Mean Statistical Value of Ship Service Speed on a Given Shipping Line , Useful in Preliminary Design Stage

2015 ◽  
Vol 22 (1) ◽  
pp. 28-35
Author(s):  
Katarzyna Żelazny
Keyword(s):  
Wind Waves ◽  
Parametric Method ◽  
Weather Conditions ◽  
Economic Effects ◽  
Design Stage ◽  
Design Parameters ◽  
Preliminary Design ◽  
Screw Propeller ◽  
Calm Water ◽  
Preliminary Design Stage

Abstract During ship design, its service speed is one of the crucial parameters which decide on future economic effects. As sufficiently exact calculation methods applicable to preliminary design stage are lacking the so called contract speed which a ship reaches in calm water is usually applied. In the paper [11] a parametric method for calculation of total ship resistance in actual weather conditions (wind, waves, sea current), was presented. This paper presents a parametric model of ship propulsion system (screw propeller - propulsion engine) as well as a calculation method, based on both models, of mean statistical value of ship service speed in seasonal weather conditions occurring on shipping lines. The method makes use of only basic design parameters and may be applied in preliminary design stage.

Closed-Form Synthesis of Force-Generating Planar Four-Bar Linkages

1995 ◽  
Author(s):  
R. Randall Soper ◽  
Michael Scardina ◽  
Paul Tidwell ◽  
Charles Reinholtz ◽  
Michael A. Lo Presti
Keyword(s):  
Closed Form ◽  
The Other ◽  
Design Parameters ◽  
Synthesis Methods ◽  
Function Generator ◽  
Mechanical Advantage ◽  
Nonlinear Mechanical ◽  
Two Parameters ◽  
Selection Of ◽  
Weight Force

Abstract This paper presents a technique for synthesizing four-bar linkages to produce a specified resisting force or torque. The resisting energy is provided by a weight acting on the other grounded link. The linkage serves as a nonlinear mechanical advantage function generator. Force and velocity synthesis methods have been extensively discussed in the literature. The general approach, however, has been to assume that the specified force or velocity occurs at a prescribed position. This results in the loss of design parameters that are being used unnecessarily to control position. In this application, force input to the linkage is specified as a function of only the input link position and the magnitude and direction of the weight force. Mechanical advantage synthesis can be achieved at as many as seven precision points. The method presented in this paper allows free selection of two parameters and viewing one infinity of solutions.

An Approximate Method for Cross Curves of Cargo Vessels

2001 ◽  
Vol 38 (02) ◽  
pp. 92-94
Author(s):  
Huseyin Yilmaz ◽  
Mesut Giiner
Keyword(s):  
Prediction Method ◽  
Design Stage ◽  
Series Data ◽  
Design Parameters ◽  
Preliminary Design ◽  
Hull Form ◽  
Beam Depth ◽  
Preliminary Design Stage ◽  
The Mathematical Model ◽  
Load Conditions

In this study, a formula is presented to estimate cross curves of cargo vessels and to predict statical stability at the preliminary design stage of the vessel. The predictive technique is obtained by regression analysis of systematically varied cargo vessel series data. In order to achieve this procedure, some cargo vessel forms are generated using Series-60. The mathematical model in this predictive technique is constructed as a function of design parameters such as length, beam, depth, draft, and block coefficient. The prediction method developed in this work can also be used to determine the effect of specific hull form parameters and the load conditions on stability of cargo vessels. The present method is applied to a cargo vessel and then the results of the actual ship are compared with those of regression values.

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