scholarly journals Axial and Pressure Thrust Stiffness of Metal Bellows for Vibration Isolators

2018 ◽  
Vol 153 ◽  
pp. 06001 ◽  
Author(s):  
Macháček Ondřej ◽  
Kubík Michal ◽  
Strecker Zbyněk ◽  
Roupec Jakub ◽  
Novák Petr ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Dynamic Behaviour ◽  
Axial Stiffness ◽  
Axial Deformation ◽  
Fem Model ◽  
Vibration Isolators ◽  
Spring Element ◽  
Metal Bellows ◽  
Dimensional Parameters ◽  
Dimension Parameter

Metal bellows are used as a spring element and simultaneously as a container (shell) for a damping medium in vibration isolators, especially in applications where any leakage is inadmissible. Dynamic behaviour of these isolators is affected by axial stiffness of bellows and by a resistance against axial deformation of bellows filled with fluid, which is in this article called pressure thrust stiffness. A method of the pressure thrust stiffness determination is discussed in this study. The method uses FEM model, which has been verified by stiffness measurement of a chosen bellows. Consequently, the sensitivity analysis of bellows dimensions to axial and pressure thrust stiffness was performed to find a dimension parameter of bellows which allows to adjust the ratio between axial and pressure thrust stiffness. Sensitivity analysis shows that the stiffness ratio of metal bellows can be adjusted by two dimensional parameters - mean diameter of bellows and corrugation width.

The nonlinear dynamics of journal bearings

1990 ◽  
Vol 332 (1624) ◽  
pp. 107-119 ◽  
Keyword(s):  
Dynamic Behaviour ◽  
Journal Bearing ◽  
Hopf Bifurcations ◽  
Qualitative Behaviour ◽  
Conceptual Approach ◽  
Theoretical Understanding ◽  
Geometrical Features ◽  
Wide Range ◽  
Dimensional Parameters ◽  
Analytical Approaches

The journal bearing is ubiquitous in moving mechanical systems, and is a major potential target for study in the field of lubrication theory. Despite this, theoretical understanding of its dynamic behaviour is far from complete ; in particular the essentially nonlinear interplay of rotor dynamics and fluid dynamics of the lubricant has been studied only very recently. Our own investigations have been mainly numerical, and have revealed a wide range of qualitative behaviour. They have confirmed the great importance of cavitation of the lubricant, and the sensitivity to geometrical features of the bearing. Additionally they have enabled us to identify the crucial non-dimensional parameters and their critical values. Finally they have stimulated analytical approaches (e.g. searches for Hopf bifurcations). In this paper we exploit the conceptual approach of dynamical systems theory to present many of our results in a succinct form. Our aim is to make clear not only the extent of understanding of the problem, but also the present shortcomings of theory that require further study.

Frequency Response of Vibration Isolators With Saturating Spring Elements

2005 ◽  
Author(s):  
M. Mahinfalah ◽  
G. Nakhaie Jazar ◽  
M. Rastgaar Aagaah ◽  
N. Mahmoudian
Keyword(s):  
Sensitivity Analysis ◽  
Frequency Response ◽  
Linear Approximation ◽  
Averaging Method ◽  
Piecewise Linear ◽  
Nonlinear Approximation ◽  
Piecewise Linear Approximation ◽  
Hyperbolic Tangent ◽  
Vibration Isolators ◽  
Tangent Function

An investigation using averaging method is carried out to obtain the frequency response of a class of vibration isolators with saturation spring. The saturation characteristics are modeled using a hyperbolic-tangent function. The hyperbolic-tangent saturation function is compared with other popular saturation functions, using piecewise nonlinear approximation. A parameteric study indicates that piecewise linear approximation of saturating functions provide results that are close enough to the results of hyperbolic tangent approximation. A sensitivity analysis of frequency response of the system is also investigated based on the piecewise linear approximation.

scholarly journals ADJOINT APPROACH SENSITIVITY ANALYSIS OF THIN‐WALLED BEAMS AND FRAMES

2005 ◽  
Vol 11 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Ireneusz Kreja ◽  
Tomasz Mikulski ◽  
Czeslaw Szymczak
Keyword(s):  
Sensitivity Analysis ◽  
Cross Section ◽  
Fem Model ◽  
Static Loads ◽  
Shell Elements ◽  
Beam Elements ◽  
Thin Walled ◽  
The One ◽  
Adjoint Approach ◽  
Open Cross Section

Sensitivity analysis of beams and frames assembled of thin‐walled members is presented within the adjoint approach. Static loads and structures composed of thin‐walled members with the bisymmetrical open cross‐section are considered. The analysed structure is represented by the one‐dimensional model consisting of thin‐walled beam elements based on the classical assumptions of the theory of thin‐walled beams of non‐deformable cross‐section together with superelements applied in place of location of structure nodes, restraints and stiffeners. The results of sensitivity analysis, obtained for the structure model described above, are compared with the results of the detailed FEM model, where the whole structure is discretised with the use of QUAD4 shell elements of the system MSC/NASTRAN.

Nonlinear Design of a Passive Vibration Isolator: Influence of Multi-Axial Stiffness

2019 ◽  
Author(s):  
Sudhir Kaul
Keyword(s):  
Dynamic Response ◽  
Dynamic Stiffness ◽  
Harmonic Balance Method ◽  
Axial Stiffness ◽  
Vibration Isolators ◽  
Trade Offs ◽  
Nonlinear Design ◽  
Integration Test ◽  
Voigt Model ◽  
Isolation Systems

Abstract Passive vibration isolators are widely used in multiple engineering applications to reduce resonance peaks or to mitigate transmissibility in the presence of internal or external sources of dynamic excitation. The design of a linear passive isolator involves multiple trade-offs. In the literature, different design configurations with nonlinearities have been investigated to limit some of these trade-offs. These include designs with quasi-zero stiffness (QZS) or high-static-low-dynamic stiffness (HSLDS) characteristics. This study investigates three viscoelastic models that incorporate stiffness nonlinearity along the non-isolating axes in order to exhibit more control over the dynamic response of the isolated system and possibly mitigate some of the design trade-offs. The dynamic response of these three models is compared to an existing HSLDS model in the literature. The three models investigated in this study are as follows: Kelvin-Voigt (or Voigt), Zener, and Generalized Maxwell (or Maxwell Ladder). These three models have been commonly used in the literature for vibration analysis of passive isolators. Two methods have been used for analysis, namely the Harmonic Balance Method (HBM) and explicit numerical integration. Test results from a previous study have been used for model characterization of all the models. It is observed that the modified Kelvin-Voigt model is analogous to the HSLDS model from the literature. For the isolator parameters used in this study, it is observed that the Kelvin-Voigt model with stiffness nonlinearity is able to exhibit characteristics similar to the HSLDS design, this includes the jump phenomenon as well as the hardening behavior. In general, all three models demonstrate that stiffness nonlinearity results in a reduction in peak transmissibility as well as an enhancement of the isolation bandwidth. The findings of this study could be useful in the design of passive isolation systems for products with significantly different multi-axial requirements with various design constraints.

The Effect of Compressibility Factor on Turbine Performance

2021 ◽  
Author(s):  
David Baumgärtner ◽  
John J. Otter ◽  
Andrew P. S. Wheeler
Keyword(s):  
Boundary Layer ◽  
Dynamic Behaviour ◽  
Compressibility Factor ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Turbine Performance ◽  
Gas Dynamic ◽  
Dimensional Parameters ◽  
The Common ◽  
Common Perception

Abstract The compressibility factor Z is one of the most common properties that describes a fluid diversion from an ideal gas. Still, its effect on turbine performance is not well known. We determine a set of non-dimensional parameters that fix the gas dynamic behaviour, independent of Z, and thus isolate the effect that Z has on turbine performance. The results indicate that, contrary to the common perception, low values of Z and hence a strong diversion from an ideal gas lead to a reduction in loss for supersonic operating conditions, if all other non-dimensionals are accounted for. The aerodynamic mechanisms responsible are due to reductions in shock, boundary layer and trailing edge loss. The results from this paper are relevant for all future turbines operating with non-ideal working fluids.

Sensitivity analysis of shoulder joint muscles by using the FEM model

2016 ◽  
Vol 3 (2) ◽  
pp. 115-127
Author(s):  
Shriniwas.S. Metan ◽  
G.C. Mohankumar ◽  
Prasad Krishna
Keyword(s):  
Sensitivity Analysis ◽  
Shoulder Joint ◽  
Fem Model

scholarly journals A comparison between cylindrical and cross-shaped magnetic vibration isolators: ideal and practical

2015 ◽  
Vol 64 (4) ◽  
pp. 593-604 ◽  
Author(s):  
D.T.E.H. Van Casteren ◽  
J.J.H. Paulides ◽  
E.A. Lomonova
Keyword(s):  
Sensitivity Analysis ◽  
Resonance Frequency ◽  
Large Diameter ◽  
Volume Ratio ◽  
Cylindrical Structure ◽  
Vibration Isolators ◽  
Small Footprint ◽  
Manufacturing Tolerances ◽  
The Cross ◽  
Tall Structure

Abstract In this paper a cross-shaped isolator consisting of cuboidal magnets and a cylindrical isolator are compared by resonance frequency to volume ratio and shape. Both isolators are capable of obtaining a low resonance frequency, i.e. 0.15 Hz and 0.01 Hz for the cross and cylinder, respectively. The volume of both isolators is comparable, only the shape is different, resulting in a tall structure with a small footprint for the cross and a flat with a large diameter cylindrical structure. A sensitivity analysis shows that due to the large amount of magnets, the cross-shaped isolator is less sensitive to manufacturing tolerances

Stiffness Modeling and Sensitivity Analysis for Worm Geared Transmission

2014 ◽  
Vol 989-994 ◽  
pp. 3328-3330
Author(s):  
Lin Han ◽  
Hou Jun Qi
Keyword(s):  
Sensitivity Analysis ◽  
Machine Tools ◽  
Torsional Stiffness ◽  
Axial Stiffness ◽  
Static Stiffness ◽  
Meshing Stiffness ◽  
Stiffness Modeling ◽  
Transmission Chain ◽  
Stiffness Model ◽  
Simulation Results

The worm geared transmission chain is widely employed in rotary feeding table of machine tools. This article proposes a static stiffness model and conducts sensitivity analysis of the transmission chain. Firstly, a unified static stiffness model is established, considering meshing stiffness, torsional stiffness and pre-load related axial stiffness of worm shaft. Then sensitivity with respect to individual stiffness element is derived based on partially differentiating method. Simulation results show that the closer to the end gear pair or shaft is, the more sensitive meshing stiffness or torsional stiffness is.

Axial Deformation of the Planetary Differential Micro-Displacement Mechanism with Finite Element Analysis

2014 ◽  
Vol 684 ◽  
pp. 358-363
Author(s):  
Shu Tian Fan ◽  
Xian Peng Guo
Keyword(s):  
Finite Element ◽  
Contact Theory ◽  
Simplified Model ◽  
Axial Stiffness ◽  
Axial Deformation ◽  
Hertz Contact ◽  
Element Analysis ◽  
Displacement Mechanism ◽  
Roller Screw ◽  
Tool Compensation

Based on the study of planetary differential roller screw, a planetary differential micro-displacement mechanism is designed for tool compensation. Axial stiffness is an important factor of over-all properties of planetary roller screw. The structure of planetary differential roller screw is similar to planetary roller screw. The axial stiffness was analyzed with Hertz contact theory and confirmed with the ANSYS. Finally, the theoretical values and simulation values were compared to verify the simplified model, and the error was analyzed. The results show that the relative error between simulation values and theoretical values are less than 5%. Therefore, the simplified model of the finite element is reasonable.

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