Research on Stiffness and Damping Characteristics of Fixed Oily Porous Materials Joint Interface

2011 ◽  
Vol 422 ◽  
pp. 575-579
Author(s):  
Chong Nian Qu ◽  
Liang Sheng Wu ◽  
Jian Feng Ma ◽  
Yi Chuan Xiao
Keyword(s):  
Porous Material ◽  
Porous Materials ◽  
Parallel Plate ◽  
Joint Interface ◽  
Force Model ◽  
Equivalent Stiffness ◽  
Contact State ◽  
Damping Characteristics ◽  
Stiffness And Damping ◽  
Damping Model

In this document, using the anti-squeezed force model in the narrow parallel plate when fluid is squeezed, the equivalent stiffness and damping model is derived. It is further verified that it can increase the stiffness and damping while there are oil between the joint interfaces theoretically. Because the contact state of oily porous material can divide into liquid and solid parts, the document supposes that it is correct and effective to think the stiffness and damping of the two parts as shunt connection.

Dynamic Characteristics Optimization of Joint Interface of Machine Tool Based on Porous Oily Materials

2014 ◽  
Vol 709 ◽  
pp. 63-67
Author(s):  
Jian Feng Ma ◽  
Qiang Li ◽  
Ji Kun Feng ◽  
Liang Sheng Wu
Keyword(s):  
Porous Material ◽  
Machine Tool ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Unit Area ◽  
Test System ◽  
Joint Interface ◽  
Characteristic Parameters ◽  
Damping Characteristics ◽  
Stiffness And Damping

The joint interface plays a significant role in machine tools and other machineries. A novel type of joint which consists of oily porous material was proposed in the paper. A test system for identifying the unit area dynamic characteristic parameters of Fe-based joint interfaces were represented. The stiffness and damping parameters were compare to the conversional structures. The result showed that the joint which contains an oil film interlayer formed by porous and steel was superior to the joint with non-media formed by steel in stiffness and damping characteristics. In the case of the same preload, the former’s stiffness is increased by about 50 %, and the damping is increased about five to six times.

Prediction of Resonant Response of Shrouded Blades With 3D Shroud Constraint

1998 ◽  
Author(s):  
B. D. Yang ◽  
J. J. Chen ◽  
C. H. Menq
Keyword(s):  
Relative Motion ◽  
Normal Load ◽  
Three Dimensional ◽  
Force Model ◽  
Resonant Response ◽  
Equivalent Stiffness ◽  
Stick Slip ◽  
Contact Plane ◽  
Blade System ◽  
Stiffness And Damping

In this paper, the 3D shroud contact kinematics of a shrouded blade system is studied. The assumed blade motion has three components, namely axial, tangential, and radial components, which result in a three dimensional relative motion across the shroud interface. The resulting relative motion can be decomposed into two components. The first one is on the contact plane and can induce stick-slip friction. The other component is perpendicular to the contact plane and can cause variation of the contact normal load and, in extreme circumstances, separation of the two contacting surfaces. In order to estimate the equivalent stiffness and damping of the shroud contact an approach is proposed. In this approach, the in-plane slip motion is assumed to be elliptical and is decomposed into two linear motions along the principal major and minor axes of the ellipse. A variable normal load friction force model (Yang and Menq, 1996) is then applied separately to each individual linear motion, and the equivalent stiffness and damping of the shroud contact can be approximately estimated. With the estimated stiffness and damping, the developed shroud contact model is applied to the prediction of the resonant response of a shrouded blade system. The effects of two different shroud constraint conditions, namely 2D constraint and 3D constraint, on the resonant response of a shrouded blade system are compared and the results are discussed.

Modelling of Rigid-Frame Porous Materials: A Simple Approach

2000 ◽  
Author(s):  
M. J. Brennan ◽  
W. M. To
Keyword(s):  
Porous Material ◽  
Porous Materials ◽  
Characteristic Impedance ◽  
Simple Approach ◽  
Middle Ground ◽  
Acoustic Behaviour ◽  
Rigid Frame ◽  
Flow Resistivity ◽  
Stiffness And Damping ◽  
Optimum Flow

Abstract This paper is concerned with the modelling of rigid-frame porous materials. Currently there are very simple models which describe the acoustic behaviour of such materials, and there are also very complicated models. The aim of this paper is to present a model which occupies the “middle ground”, but is simple enough to be used by practising noise control engineers. Using concepts of acoustic mass, stiffness and damping, non-dimensional expressions for the acoustic wavenumber and the characteristic impedance of a rigid-frame porous material are derived. These expressions are used to give a “rule of thumb” for the optimum flow resistivity for a given thickness of material.

Prediction of Resonant Response of Shrouded Blades With Three-Dimensional Shroud Constraint

1999 ◽  
Vol 121 (3) ◽  
pp. 523-529 ◽  
Author(s):  
B. D. Yang ◽  
J. J. Chen ◽  
C. H. Menq
Keyword(s):  
Relative Motion ◽  
Normal Load ◽  
Three Dimensional ◽  
Force Model ◽  
Resonant Response ◽  
Equivalent Stiffness ◽  
Stick Slip ◽  
Contact Plane ◽  
Blade System ◽  
Stiffness And Damping

In this paper, the three-dimensional shroud contact kinematics of a shrouded blade system is studied. The assumed blade motion has three components, namely axial, tangential, and radial components, which result in a three dimensional relative motion across the shroud interface. The resulting relative motion can be decomposed into two components. The first one is on the contact plane and can induce stick-slip friction. The other component is perpendicular to the contact plane and can cause variation of the contact normal load and, in extreme circumstances, separation of the two contacting surfaces. In order to estimate the equivalent stiffness and damping of the shroud contact an approach is proposed. In this approach, the in-plane slip motion is assumed to be elliptical and is decomposed into two linear motions along the principal major and minor axes of the ellipse. A variable normal load friction force model (Yang and Menq, 1996) is then applied separately to each individual linear motion, and the equivalent stiffness and damping of the shroud contact can be approximately estimated. With the estimated stiffness and damping, the developed shroud contact model is applied to the prediction of the resonant response of a shrouded blade system. The effects of two different shroud constraint conditions, namely two-dimensional constraint and three-dimensional constraint, on the resonant response of a shrouded blade system are compared and the results are discussed.

Vibration Isolation Research on the Metal Rubber Damping Rod of Payload Attach Fitting

2011 ◽  
Vol 391-392 ◽  
pp. 467-473 ◽  
Author(s):  
Zhan Ji Wei ◽  
Dong Xu Li ◽  
Rui Xu
Keyword(s):  
High Frequency ◽  
Vibration Isolation ◽  
Resonant Peak ◽  
Vibration Load ◽  
Equivalent Damping ◽  
Damping Characteristics ◽  
Metal Rubber ◽  
Vibration Parameters ◽  
Stiffness And Damping ◽  
Damping Model

In order to reduce the vibration load transmitted from the launch vehicle to the spacecraft during the launching stage, a whole-spacecraft vibration isolating method is advanced by modifying ordinary payload attach fitting (PAF). The core component of the PAF is a kind of damping rod produced by composite material encapsulating metal rubber (MR). In this paper, nonlinear equivalent damping model of the damping rod is built up. By using the model, the stiffness, damping and the transmissibility of the damping rod is studied attentively. Simulation results demonstrate that there exist nonlinear relationships between vibration parameters and the stiffness and damping characteristics of the damping rod. The damping rod can isolate high-frequency vibration as well as restrain the resonant peak effectively.

Research on the Static and Dynamic Characteristics of the Sliding Rail Joint Surfaces of the Fe-Based Porous Oily Material

2014 ◽  
Vol 607 ◽  
pp. 422-426
Author(s):  
Jian Feng Ma ◽  
Qiang Li ◽  
Liang Sheng Wu ◽  
Chong Nian Qu
Keyword(s):  
Dynamic Characteristics ◽  
Unit Area ◽  
Test System ◽  
Joint Interface ◽  
Equivalent Stiffness ◽  
Characteristic Parameters ◽  
Single Degree Of Freedom ◽  
Joint Surfaces ◽  
Machine Tool Structures ◽  
Stiffness And Damping

The dynamic characteristics of joint interfaces have significant effect on both static and dynamic behaviors of the whole machine tool structures. A test system for identifying the unit area dynamic characteristic parameters of Fe-based joint interfaces in still and motion states were represented based on Equivalent Single Degree Of Freedom (ESDOF) system theory. Compared with the stiffness and damping parameters in stationary state, the stiffness is reduced and the damping is increased in motion. When the velocity increased, the equivalent stiffness and damping parameters of joint interface are both increased.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions

2006 ◽  
Vol 129 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Luis San Andrés ◽  
Dario Rubio ◽  
Tae Ho Kim
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Load Capacity ◽  
Test System ◽  
Foil Bearings ◽  
Rotor Imbalance ◽  
Synchronous Motion ◽  
Damping Characteristics ◽  
Rotor Surface ◽  
Stiffness And Damping

Gas foil bearings (GFBs) satisfy the requirements for oil-free turbomachinery, i.e., simple construction and ensuring low drag friction and reliable high speed operation. However, GFBs have a limited load capacity and minimal damping, as well as frequency and amplitude dependent stiffness and damping characteristics. This paper provides experimental results of the rotordynamic performance of a small rotor supported on two bump-type GFBs of length and diameter equal to 38.10mm. Coast down rotor responses from 25krpm to rest are recorded for various imbalance conditions and increasing air feed pressures. The peak amplitudes of rotor synchronous motion at the system critical speed are not proportional to the imbalance introduced. Furthermore, for the largest imbalance, the test system shows subsynchronous motions from 20.5krpm to 15krpm with a whirl frequency at ∼50% of shaft speed. Rotor imbalance exacerbates the severity of subsynchronous motions, thus denoting a forced nonlinearity in the GFBs. The rotor dynamic analysis with calculated GFB force coefficients predicts a critical speed at 8.5krpm, as in the experiments; and importantly enough, unstable operation in the same speed range as the test results for the largest imbalance. Predicted imbalance responses do not agree with the rotor measurements while crossing the critical speed, except for the lowest imbalance case. Gas pressurization through the bearings’ side ameliorates rotor subsynchronous motions and reduces the peak amplitudes at the critical speed. Posttest inspection reveal wear spots on the top foils and rotor surface.

Sign in / Sign up

Export Citation Format

Share Document