scholarly journals Friction-induced vibrations in the framework of dynamic substructuring

2020 ◽  
Author(s):  
Jacopo Brunetti ◽  
Walter D’Ambrogio ◽  
Annalisa Fregolent
Keyword(s):  
A Priori ◽  
Element Model ◽  
Friction Forces ◽  
Coupling Conditions ◽  
Contact Points ◽  
Dynamic Substructuring ◽  
Reliable Model ◽  
Time Invariant ◽  
Substructuring Techniques ◽  
Vibrating Systems

AbstractIn complex vibrating systems, contact and friction forces can produce a dynamic response of the system (friction-induced vibrations). They can arise when different parts of the system move one with respect to the other generating friction force at the contact interface. Component mode synthesis and more in general substructuring techniques represent a useful and widespread tool to investigate the dynamic behavior of complex systems, but classical techniques require that the component subsystems and the coupling conditions (compatibility of displacements and equilibrium of forces) are time invariant. In this paper, a substructuring method is proposed that, besides accounting for the macroscopic sliding between substructures, is able to consider also the local vibrations of the contact points and the geometric nonlinearity due to the elastic deformation, by updating the coupling conditions accordingly. This allows to obtain a more reliable model of the contact interaction and to analyze friction-induced vibrations. Therefore, the models of the component substructures are time invariant, while the coupling conditions become time dependent and a priori unknown. The method is applied to the study of a finite element model of two bodies in frictional contact, and the analysis is aimed to the validation of the proposed method for the study of dynamic instabilities due to mode coupling.

The Feasibility of Statistical Energy Analysis in the Modeling of Stringed Musical Instruments

2010 ◽  
Author(s):  
Hossein Mansour
Keyword(s):  
Finite Element ◽  
Structural Modification ◽  
Energy Analysis ◽  
Element Model ◽  
Musical Instruments ◽  
Statistical Energy Analysis ◽  
Reliable Model ◽  
Challenging Tasks ◽  
High Degree ◽  
Vibrating Systems

Stringed musical instruments are complex vibrating systems both from structural and fluid-structure coupling perspectives; hence, their modeling is one of the most challenging tasks in the area of vibration and acoustics. Making a reliable model not only broadens our knowledge of the physics of these instruments, but also it simplifies the procedure of structural modification and optimization on them. In this regard, a Finite Element Model has been previously made from Setar and is verified with the experimental results. Although that model could precisely simulate the instrument in lower frequencies (i.e. below 2.5 KHz), its results showed a weak correlation with reality in higher frequencies. In fact, unreliable results and high computational demand are common drawbacks of finite element method in higher frequencies. To avoid these problems, in this study Setar is modeled with Statistical Energy Analysis (SEA) approach. This method is more efficient in dealing with high degree of uncertainty in the system. SEA does this by averaging the response over the frequency and location to gain a more general and reliable result. Application of SEA in higher frequencies is, in fact, compatible with the nature of musical instruments where in higher frequencies we are mostly interested in the trend of the response rather than the location of each individual peak.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

scholarly journals Modeling a Helical Fluid Inerter System with Time-Invariant Mem-Models

2020 ◽  
Author(s):  
David Wagg ◽  
Jin-Song Pei
Keyword(s):  
Element Model ◽  
Feedforward Neural Network ◽  
Dynamic Responses ◽  
Experimental Measurements ◽  
The Novel ◽  
State Variables ◽  
Model Concept ◽  
Multilayer Feedforward Neural Network ◽  
Time Invariant ◽  
Model Family

In this paper, experimental data from tests of a helical fluid inerter are used to model the observed hysteretic behaviour. The novel idea is to test the feasibility of employing mem-models, which are time-invariant herein, to capture the observed phenomena by using physically meaningful state variables. Firstly we use a Masing model concept, identified with a multilayer feedforward neural network to capture the physical characteristics of the hysteresis functions. Following this, a more refined approach based on the concept of a multi-element model including a mem-inerter is developed. This is compared with previous definitions in the literature and shown to be a more general model. Through-out this paper, numerical simulations are used to demonstrate the type of dynamic responses anticipated using the proposed time- invariant mem-models. Corresponding experimental measurements are processed to demonstrate and validate the new mem-modeling concepts. The results show that it is possible to have a unified model constructed using both the damper and inerter from the mem-model family. This model captures many of the more subtle features of the underlying physics, not captured by other forms of existing model.

Simulation Research on Cross-Sectional Stability of Expanded Diameter Conductors Based on ANSYS

2012 ◽  
Vol 256-259 ◽  
pp. 2838-2843
Author(s):  
Jia Jun Si ◽  
Jian Cheng Wan ◽  
Bin Liu ◽  
Yao Ding
Keyword(s):  
Power Transmission ◽  
Element Model ◽  
Aluminum Wire ◽  
Key Factors ◽  
Cross Sectional ◽  
Simulation Research ◽  
Contact Points ◽  
Electricity Power ◽  
The Wire ◽  
Significant Factors

The expanded diameter conductors are widely used for high voltage electricity power transmission due to its superior ability to prevent electronic corona phenomenon. However an undesired stability problem of wire distribution configuration within the cross-section of the conductor often occurs during the power line stringing processes, especially for the not-well-designed conductor structures. This phenomenon is typically characterized by the appearance of outer wire/wires jumping out of the layer; therefore it is also referred as wire jump-out problem. Finite element model which can predict the wire jump-out phenomenon has been successfully developed in this research project. Series of stimulations have been carried out to investigate the key factors to cause the wire jump-out problem. The reduction of radial distances between the adjacent aluminum wire layers due to the obvious indentation deformation at the trellis contact points were identified to be one of the most significant factors to lead to the wire jump-out problem. Numerical results show that keeping sufficient initial gap between the adjacent outer layer wires in the initial design can be a simple effective way to relieve/avoid the wire jump-out problem.

On a Perturbation Method for the Analysis of Unsteady Belt-Drive Operation

2004 ◽  
Vol 72 (4) ◽  
pp. 570-580 ◽  
Author(s):  
Michael J. Leamy
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Perturbation Method ◽  
Element Model ◽  
Contact Forces ◽  
Steady Solution ◽  
Belt Drive ◽  
Friction Forces ◽  
Direct Contrast ◽  
Validity Criteria

A perturbation method is presented for use in analyzing unsteady belt-drive operation. The method relies on the important assumption that for operating states close to steady operation, the friction state (i.e., whether the belt is creeping or sticking at any location on the pulley) is similar to that of the well-known steady solution in which a lone stick arc precedes a lone slip arc (Johnson, K. L., 1985, Contact Mechanics, Cambridge U.P., London, Chap. 8; Smith, D. P., 1999, Tribol. Int., 31(8), pp. 465–477). This assumption, however, is not used to determine the friction force distribution, and, in fact, the friction forces in the stick zone are found to be nonzero, in direct contrast to the steady solution. The perturbation analysis is used to derive expressions for the span tensions, the pulley tension distributions, the contact forces between the belt and the pulleys, and the angular velocity of the driven pulleys. Validity criteria are developed which determine bounds on the operation state for which the assumed friction state is upheld. Verification of response quantities from the perturbation solution is accomplished through comparison to quantities predicted by an in-house dynamic finite element model and excellent agreement is found. Additionally, the finite element model is used to verify the key assumption that a lone slip arc precedes a lone stick arc.

Finite element modeling of guyed back spars in cable logging

2004 ◽  
Vol 34 (4) ◽  
pp. 817-828 ◽  
Author(s):  
Albert Saravi ◽  
C Kevin Lyons
Keyword(s):  
Finite Element ◽  
Normal Stress ◽  
Cross Section ◽  
A Priori ◽  
Element Model ◽  
Transverse Cross Section ◽  
Stress Fields ◽  
Stress Concentrations ◽  
Maximum Normal Stress ◽  
Tree Method

In this study a finite element model of a back spar system was developed with three guylines opposing the skyline strap tension. In this paper the allowable skyline strap tension is the tension in the skyline strap that results in the maximum normal stress on a transverse cross section of the tree being equal to an assumed allowable stress. An iterative routine was developed to find the allowable skyline strap tension, and this routine was found to converge rapidly from initial values that were below and above the allowable skyline strap tension. Two algorithms were developed for finding the maximum normal stress on a transverse cross section of a tree, method 1 and method 2. If the plane that the tree displaced in was known a priori, then method 2 could be used, and it was found to be less sensitive to mesh coarseness. If the plane that the tree displaced in was not known a priori, then method 1 had to be used with a less coarse mesh. It was found that the stress concentrations due to simplified cable connections were not significant for rigging configurations that allowed a larger rigging point displacement. The rigging configurations that allowed larger rigging point displacements have stress fields that are dominated by bending, while for rigging configurations that allow only small rigging point displacements, the stress fields are dominated by axial compression.

Optimal configuration of shakers for phase resonance testing using modal parameters

2019 ◽  
Vol 233 (16) ◽  
pp. 5676-5690 ◽  
Author(s):  
Wei Chen ◽  
Mengshi Jin ◽  
Hanwen Song
Keyword(s):  
Amplitude Ratio ◽  
A Priori ◽  
Ground Vibration ◽  
Element Model ◽  
Optimal Configuration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Target Mode ◽  
Modal Force ◽  
Phase Resonance

The phase resonance testing is widely used in the ground vibration test for aircraft due to the advantages of distinguishing closely spaced modes and directly comparing normal mode shapes with those from finite element model. However, the process to configure the shakers is time-consuming. A method to configure the shakers, which calculates the appropriate force vector and estimates the optimal combination of excitation locations for phase resonance testing, is proposed in this paper. Compared with other configuration methods, where the frequency response function matrix is known a priori, the proposed method only requires a priori information of rough modal parameters. Therefore, less information is used in this method, which leads to the advantage of calculating the optimal configuration more efficiently. In this method, the modal force amplitude ratio of the target mode to all the modes, called the modal ratio indicator, is set up as the criterion to select the optimal configuration. Simulations of a discrete plate are performed to show the process of the method. An experiment of a steel beam is conducted to validate the effectiveness and reliability of this method.

scholarly journals Force Magnitude Reconstruction Using the Force Transmissibility Concept

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Y. E. Lage ◽  
N. M. M. Maia ◽  
M. M. Neves
Keyword(s):  
Experimental Data ◽  
A Priori ◽  
Element Model ◽  
Direct And Inverse Problems ◽  
Force Magnitude ◽  
Mdof Systems ◽  
Applied Forces ◽  
Force Transmissibility ◽  
The Common ◽  
Hybrid Methodology

This paper proposes the reconstruction of forces, based on the direct and inverse problems of transmissibility in multiple degree of freedom (MDOF) systems. The objective and novelty are to use the force transmissibility to calculate reactions given the applied loads (and vice versa). This method, relating two sets of forces, proves to be an alternative to the common inverse problem based on the measurement of FRFs and operational accelerations to determine operational forces, as it can be advantageous in some cases. This implies thea prioriknowledge of the transmissibility of the structure, either experimentally or numerically. In this study a finite element model is built, describing with enough accuracy the dynamic behavior of the structure. The numerical model will play a key role in the construction of the transmissibility matrix; this will be used to evaluate either the reaction or the applied forces, using experimental data. This constitutes a hybrid methodology, which is validated experimentally. The authors present several comparisons between reconstructed and experimentally measured sets of forces. It is shown that the proposed method is able to produce good results in the reconstruction of the forces, underlining its potential for other structures and possible applications.

Elastodynamic and finite element vibration analysis of a drillstring with a downhole vibration generator tool and a shock sub

2014 ◽  
Vol 229 (8) ◽  
pp. 1361-1384 ◽  
Author(s):  
Ahmad Ghasemloonia ◽  
D Geoff Rideout ◽  
Stephen D Butt ◽  
Ali Hajnayeb
Keyword(s):  
Finite Element ◽  
Axial Force ◽  
Vibration Suppression ◽  
Fem Simulation ◽  
Element Model ◽  
Hertzian Contact ◽  
Contact Points ◽  
Fast Running ◽  
Lateral Displacements ◽  
Dynamic Amplification

Applying high-frequency axial oscillation into an oilwell drillstring in the “bottom-hole assembly” (BHA) has the potential to enhance drilling efficiency in extended reach wells. Downhole vibration generator tools such as agitators reduce the drillstring–wellbore friction and enhance the rate of penetration. However, introducing controlled vibrations into the drillstring can result in undesired vibration waves propagating along the drillstring, leading to inefficient drilling and catastrophic fatigue failure of the BHA components, “measurement-while-drilling” tools, and mud motors. A dynamic model of the entire drillstring, including vibration generators and shock subs, is required to study the effect of vibration generators on the complex nonlinear coupled axial-lateral dynamics of a drillstring inside a wellbore, to study the effect of vibration tools on the developed cutting force at the bit, and to facilitate simulation-based design of shock subs. A dynamic finite element model (FEM) and an analytical elastodynamic model, both including the vibration generator tool and a shock sub, have been developed. The “Bypassing PDEs” method was implemented on the Lagrangian of the system to develop the analytical equations. A multi-mode expanded Galerkin’s approximation, in conjunction with a multi-span BHA and Hertzian contact assumption, allowed analysis of multiple BHA contact points and, thus, more realistic estimates of drilling rotary speeds that can cause excessive vibration. The models also include torque, mud damping, spatially varying axial force, geometric nonlinearity, and axial stiffening. While the analytical model has fast running time and symbolic solution, the FEM model enables easy reconfiguration and future extensions of model geometry, interactions, and modified BHA configurations. There is agreement between the analytical and FEM simulation results for the vibration suppression ability of the shock sub, dynamic amplification of the vibrating tool force, critical rotary speeds, axial force along the drillstring, axial and lateral displacements, and the contact locations and severity.

scholarly journals Nonlinear Vibration of Gears With Tooth Surface Modifications

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Tugan Eritenel ◽  
Robert G. Parker
Keyword(s):  
Nonlinear Vibration ◽  
Multiple Scales ◽  
Gear Tooth ◽  
A Priori ◽  
Surface Modifications ◽  
Element Model ◽  
Transmission Error ◽  
Tooth Profile ◽  
Tooth Surface ◽  
Partial Contact

This work provides an analytical solution for the nonlinear vibration of gear pairs that exhibit partial and total contact loss. Partial contact loss is where parts of contact lines lose contact although other parts remain in contact. The gear tooth surface modifications admit an arbitrary combination of profile and lead modifications. Modifications are a source of partial contact loss. The analysis also applies for total contact loss. Unlike models in the literature that are excited by static transmission error or time-varying mesh stiffness, the excitation and the nonlinearity are not a priori specified. Instead, the force-deflection function of the gear pair is provided by an independent source, such as a finite element model or Hertz contact formula. The manipulation of the single-degree-of-freedom oscillator equation of motion yields the excitation and the nonlinearity that arise from Fourier and Taylor series expansions of the force-deflection function. These expansions capture the essential contact behavior that includes tooth profile and lead modifications as well as the bending and shear flexibility of the gear teeth and gear blanks. The method of multiple scales gives the steady-state dynamic response in terms of a frequency-amplitude relation. Comparisons with gear vibration experiments and simulations from the literature that include spur and helical gears with tooth profile and lead modifications verify the method.

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