scholarly journals Model Updating and Global Eigenvalue Analysis of a Tie-Bolt Rotor Using Zero-Length Contact Elements under Different Preloads

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Pu Li ◽  
Qi Yuan
Keyword(s):  
Model Updating ◽  
Contact Stiffness ◽  
Great Influence ◽  
Modal Testing ◽  
Linear Spring ◽  
Modal Behavior ◽  
Stiffness And Damping ◽  
The Impact ◽  
Contact Parameters ◽  
Rotor Model

Tie-bolt rotors are composed of several disks fastened by tie bolts where contact properties have a great influence on the modal behavior. In this work, a linear spring-damper element is used to consider the contact stiffness and damping in a tie-bolt rotor. A tie-bolt rotor model is developed using the beam element and the zero-length contact element. Experimental modal testing is performed under different preloads of tie bolts. Model updating is carried out to tune the contact parameters using the Particle Swarm Optimization algorithm. Furthermore, a global eigenvalue evaluation is carried out to demonstrate the impact of the lumped spring-damper element on the modal results. Results show that a larger pretension reduces the influence of contact damping on modal parameters. Compared to antisymmetric modes, symmetric modes are more sensitive to the change of contact damping.

scholarly journals Impact of Cross-Tie Properties on the Modal Behavior of Cable Networks on Cable-Stayed Bridges

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Javaid Ahmad ◽  
Shaohong Cheng ◽  
Faouzi Ghrib
Keyword(s):  
Analytical Model ◽  
Design Parameters ◽  
Reference Base ◽  
Cable Network ◽  
Cable Networks ◽  
Modal Behavior ◽  
Stiffness And Damping ◽  
Main Cables ◽  
The Impact ◽  
Selection Of

Dynamic behaviour of cable networks is highly dependent on the installation location, stiffness, and damping of cross-ties. Thus, these are the important design parameters for a cable network. While the effects of the former two on the network response have been investigated to some extent in the past, the impact of cross-tie damping has rarely been addressed. To comprehend our knowledge of mechanics associated with cable networks, in the current study, an analytical model of a cable network will be proposed by taking into account both cross-tie stiffness and damping. In addition, the damping property of main cables in the network will also be considered in the formulation. This would allow exploring not only the effectiveness of a cross-tie design on enhancing the in-plane stiffness of a constituted cable network, but also its energy dissipation capacity. The proposed analytical model will be applied to networks with different configurations. The influence of cross-tie stiffness and damping on the modal response of various types of networks will be investigated by using the corresponding undamped rigid cross-tie network as a reference base. Results will provide valuable information on the selection of cross-tie properties to achieve more effective cable vibration control.

Modal Modeling of Micro-Machining Center

2012 ◽  
Author(s):  
Marcin Chodźko ◽  
Krzysztof Marchelek
Keyword(s):  
Machine Tool ◽  
Model Updating ◽  
Dynamic Properties ◽  
Modal Testing ◽  
Mode Shapes ◽  
Experimental Investigations ◽  
Micro Machining ◽  
Machining Center ◽  
Modal Model ◽  
The Impact

Modeling of dynamic properties of machine tools has a significant influence on improvement of its construction. This process is extremely important when a new construction of machine tool is under development. Experimental modal analysis provides information about frequency bandwidths with significant amplitudes of resonances, damping values and mode shapes. This information can be used in FEM model updating, stability prediction or finding weak elements of the machine tool structure as well. In the paper the modal model of prototype of the micro machining center is presented. Polymax algorithm was used to estimate the poles (frequency, damping) of modal model and modal shapes. Modal model was built on the basis of the impact test results. Methodology of conducted experimental test is presented. Tested machine tool was made of different materials (steel, aluminum, stone and others) which causes difficulties during experimental investigations. In the construction different types of guideways were implemented — rolling, slide and pneumatic ones. Maximum rotational speed of the tool is about 100 000 rev/min, so the frequency range where poles of modal model are estimated is wide (high frequencies of excitation during machining). Weight of sensors used during testing is an important issue due to a low mass of the structure. Also the excitation of the structure is troublesome because of vulnerability of precise guideways and forces sensors used in machine tool construction. Validation of the modal model is also presented in the paper and practical problems of modal testing are discussed.

scholarly journals Influence of the Main Contact Parameters in Finite Element Analysis of Elastic Bodies in Contact

2016 ◽  
Vol 681 ◽  
pp. 214-227 ◽  
Author(s):  
Gabriel Hattori ◽  
Alberto Luiz Serpa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Contact Stiffness ◽  
Great Influence ◽  
Contact Problems ◽  
Correct Choice ◽  
Element Analysis ◽  
Contact Algorithm ◽  
Key Issues ◽  
Contact Parameters

One of the key issues in solving contact problems is the correct choice of the contact parameters. The contact stiffness, the penetration limit and the contact algorithm are some of the parameters that have to be adjusted. There are no methodologies available in the literature for choosing the contact parameters, relying only on the user experience for this important task. In this work we investigate how the contact parameters behave in a commercial finite element analysis software. We will show that while the contact stiffness has great influence on the finite element analysis, other parameters will not affect it significantly. Some contact examples are shown to illustrate the performance of the contact parameters during the solution of a contact problem.

scholarly journals Determination of Contact Stiffness and Damping of a Tie-Bolt Rotor with Interference Fits Using Model Updating with Thin-Layer Elements

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Pu Li ◽  
Qi Yuan
Keyword(s):  
Thin Layer ◽  
Gas Turbines ◽  
Model Updating ◽  
Contact Stiffness ◽  
Fe Model ◽  
Press Fit ◽  
Response Surface Optimization ◽  
Modal Damping ◽  
Step Model ◽  
Stiffness And Damping

Tie-bolt rotors are commonly applied in aeroengines and gas turbines, and interference fits ensure accurate positioning for disk assembling. This paper presents experimental and numerical studies on the stiffness and damping properties of a tie-bolt rotor with interference fits under different preloads. An FE model incorporating thin-layer elements is used to carry out model updating to predict the contact stiffness and damping characteristics. A two-step model updating approach of the tie-bolt rotor using the response surface optimization is implemented. Finally, a quasistatic FE simulation concerning the interference fits and sensitivity analysis is performed to validate the experimental results. Press fit induces a bilinear contact stiffness. Also, modal damping demonstrates a more sensitive and nonmonotonic behavior versus preload.

scholarly journals Effect of End-Effector Compliance on Collisions in Robotic Teleoperation

2020 ◽  
Vol 10 (24) ◽  
pp. 9077
Author(s):  
Domenico Tommasino ◽  
Giulio Cipriani ◽  
Alberto Doria ◽  
Giulio Rosati
Keyword(s):  
Mathematical Model ◽  
Elastic System ◽  
Contact Stiffness ◽  
End Effector ◽  
Stable Mechanism ◽  
Stiffness And Damping ◽  
And Control ◽  
The Impact ◽  
Robotic Teleoperation ◽  
Mechanical Decoupling

In robotic teleoperation, hard impacts between a tool and the manipulated object may impair the success of a task. In order to develop a robotic system that is able to minimize the final velocity of an object after impact, a comprehensive approach is adopted in this work, and the effect on the impact of the parameters of the tool and of the robot is studied. Mass, contact stiffness and damping, robot compliance and control and tool compliance are taken into account. A mathematical model including the tool and the robot moving along the approach direction shows that, in most conditions, robot compliance is not enough to mitigate the impact. A mechanical decoupling between the inertia of the tool and the inertia of the robot is needed. An elastic system based on a bi-stable mechanism is developed and its validity is shown by means of numerical simulations.

Role of Brand experience in Fashion brands

2019 ◽  
Vol 118 (1) ◽  
pp. 57-64
Author(s):  
G. Aiswarya ◽  
Dr. Jayasree Krishnan
Keyword(s):  
Factor Analysis ◽  
Purchase Intention ◽  
Great Influence ◽  
Brand Experience ◽  
Brand Preference ◽  
Mediating Role ◽  
Confirmatory Factor ◽  
Selling Strategies ◽  
The Impact

Traditionally the products were pushed into the hands of customers by production and selling strategies; then the marketing strategy evolved which gained momentum by understanding the customer needs and developing products satisfying those needs. This strategy is most prevalent and what should be done to stand up in this most competitive scenario? The answer to this key question is to create an experience. The customers now also seek good experiences than other benefits. Brand experience has gained more attention, especially fashion brands. Previous studies demonstrate the role of the brand experience in brand equity and other consumer behavior constructs. But very little is known about the impact of brand experiences on fashion brands. The aim of this study is to develop a model which makes our understanding better about the role of Brand preference and Brand experience and its influence on purchase intention of the brand. An initial exploratory study is conducted using a focus group to generate items for the study. The items, thus generated are prepared in the form of a questionnaire and samples were collected.  Exploratory factor analysis is conducted and the reliability of the constructs is determined. These constructs are loaded onto AMOS to perform Confirmatory factor analysis. The results confirmed the scales used. We also noticed that Brand preference has a great influence on the Brand experience. Thereby the finding supports the role of the brand experience which tends to have a mediating role in influencing the purchase intention.

scholarly journals Contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions

Friction ◽  
2021 ◽  
Author(s):  
Zongzheng Wang ◽  
Wei Pu ◽  
Xin Pei ◽  
Wei Cao
Keyword(s):  
Contact Stiffness ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Spiral Bevel Gears ◽  
Bevel Gears ◽  
Dry Contact ◽  
Spiral Bevel ◽  
Stiffness And Damping ◽  
Lubrication Conditions ◽  
Film Lubrication

AbstractExisting studies primarily focus on stiffness and damping under full-film lubrication or dry contact conditions. However, most lubricated transmission components operate in the mixed lubrication region, indicating that both the asperity contact and film lubrication exist on the rubbing surfaces. Herein, a novel method is proposed to evaluate the time-varying contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions. This method is sufficiently robust for addressing any mixed lubrication state regardless of the severity of the asperity contact. Based on this method, the transient mixed contact stiffness and damping of spiral bevel gears are investigated systematically. The results show a significant difference between the transient mixed contact stiffness and damping and the results from Hertz (dry) contact. In addition, the roughness significantly changes the contact stiffness and damping, indicating the importance of film lubrication and asperity contact. The transient mixed contact stiffness and damping change significantly along the meshing path from an engaging-in to an engaging-out point, and both of them are affected by the applied torque and rotational speed. In addition, the middle contact path is recommended because of its comprehensive high stiffness and damping, which maintained the stability of spiral bevel gear transmission.

Identification of Dynamical Contact Parameters for Spindle-Tool Holder Interface Based on the Receptance Coupling Substructure Approach

2011 ◽  
Vol 287-290 ◽  
pp. 2185-2190
Author(s):  
Yong Sheng Zhao ◽  
Ri Qing Dong ◽  
Zhi Feng Liu ◽  
Tie Neng Guo
Keyword(s):  
Contact Dynamics ◽  
Chatter Stability ◽  
Simple Manner ◽  
Accurate Identification ◽  
Tool Holder ◽  
Receptance Coupling ◽  
Dynamical Parameters ◽  
Substructure Approach ◽  
Stiffness And Damping ◽  
Contact Parameters

It is very crucial to accurately identify the parameters of contact dynamics in predicting the chatter stability of spindle–tool holder assemblies in machining centers. Fast and accurate identification of contact dynamics in spindle–tool holder assembly has become an important issue in the recent years. In this paper, the receptance coupling substructure approach is employed for identification the stiffness and damping of the interface in a simple manner, in which the frequency response function of the tool holder is derived from the Timoshenko beam finite elements model. A BT 50 type tool holder is adopted as an application example of the method. Although this study focuses on the contact dynamics at the spindle–tool holder interfaces of the assembly, the approach might be used for identifying the dynamical parameters of other critical interface.

The Science of Goal Setting

2012 ◽  
Vol 19 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Daniel Hayden ◽  
Fangzhou Deng
Keyword(s):  
Goal Setting ◽  
Diffusion Of Innovation ◽  
Social Marketing ◽  
Collective Behavior ◽  
Great Influence ◽  
Environmental Conservation ◽  
Marketing Campaign ◽  
Social Marketing Campaign ◽  
Social Marketing Campaigns ◽  
The Impact

Goal setting within social marketing campaigns is art and science. An analysis of Rare Pride conservation campaigns shows the quantitative, replicable relationship among the impact of these conservation campaigns with diffusion of innovation theory, and collective behavior theory that can guide marketers to set better goals. Rare is an environmental conservation organization that focuses on reducing community-based threats to biodiversity through a social marketing campaign called Pride. Pride campaigns work by removing barriers to change (whether they are technical, social, and political or something else) and inspiring people to make change happen. Based on the analysis of historical Pride campaign survey data, we found that the starting percentage of engagement has a great influence on the percentage change at the end of the campaign: The higher the initial adoption level of knowledge, attitude, and behavior change, the easier these measures are to improve. The result also suggests a difference in the potential of change with different audience segments: It is easiest to change influencer, then general public, and finally resource user who are the target of the social marketing campaign. In this article, we will analyze how to use diffusion of innovation and collective behavior theories to explain the impact of campaigns, as well as how to set more attainable goals. This article is consistent with similar research in the field of public health, which should help marketers set goals more tightly, allocate resources more effectively, and better manage donor expectations.

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