Experimental Investigation of a System With Multiple Nearly Identical Centrifugal Pendulum Vibration Absorbers

2003 ◽  
Author(s):  
Tyler M. Nester ◽  
Alan G. Haddow ◽  
Steven W. Shaw
Keyword(s):  
Experimental Investigation ◽  
Theoretical Background ◽  
Experimental Results ◽  
Circular Path ◽  
Vibration Absorbers ◽  
Test Apparatus ◽  
Controlled Experiments ◽  
Theoretical Predictions ◽  
Centrifugal Pendulum Vibration Absorbers ◽  
First Time

This paper presents experimental results from tests completed on a rotor system fitted with nearly-identical circular path centrifugal pendulum vibration absorbers. A brief review of theoretical background for the absorbers is given along with an overview of the test apparatus. The experimental results for one absorber and for four absorbers are presented and compared with theoretical predictions and expectations. To the best knowledge of the authors, this is the first time that systematic, controlled experiments that monitored both the response of the absorbers and the rotor have been undertaken.

An Experimental Study of Torsional Vibration Absorbers

2001 ◽  
Author(s):  
Alan G. Haddow ◽  
Steven W. Shaw
Keyword(s):  
Experimental Study ◽  
Dynamic Behavior ◽  
Systematic Study ◽  
Torsional Vibration ◽  
Theoretical Background ◽  
Controlled Environment ◽  
Vibration Absorbers ◽  
Test Apparatus ◽  
First Time ◽  
Theoretical Results

Abstract This paper presents results from tests completed on a rotor system fitted with pendulum-type torsional vibration absorbers. A review of the associated theoretical background is also given and the experimental and theoretical results are compared and contrasted. An overview of the test apparatus is provided and its unique features are discussed. To the best knowledge of the authors, this is the first time that a systematic study of the dynamic behavior of torsional vibration absorbers has been undertaken in a controlled environment.

Nonlinear Transient Dynamics of Pendulum Torsional Vibration Absorbers—Part II: Experimental Results

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Ryan J. Monroe ◽  
Steven W. Shaw
Keyword(s):  
Torsional Vibration ◽  
Companion Paper ◽  
Experimental Results ◽  
Circular Path ◽  
Vibration Absorbers ◽  
Automotive Engine ◽  
Engine Order ◽  
Applied Torque ◽  
Centrifugal Pendulum Vibration Absorbers ◽  
Nonlinear Transient

This paper presents results from an experimental investigation of the transient response of centrifugal pendulum vibration absorbers, including a comparison with the analytical results derived in the companion paper, Part I. The focus of the study is the overshoot experienced by pendulum-type torsional vibration absorbers when a rotor running at a constant speed is suddenly subjected to an applied fluctuating torque. The experiments are carried out using a fully instrumented spin rig controlled by a servo motor that can provide user-specified engine order disturbances, including those that simulate automotive engine environments. The absorber overshoot depends on the absorber tuning relative to the excitation order, the absorber damping, the amplitude of the applied torque, and on the system nonlinearity, which is set by the absorber path and/or kinematic coupling between the rotor and the absorber. Two types of absorbers are used in the study, a simple circular path pendulum, for which the path nonlinearity is dominant, and a nearly tautochronic path pendulum with a bifilar support, for which the path and coupling nonlinearities are both small. It is found that the experimental results agree very well with the analytical predictions from the companion paper. In addition, it is confirmed that the general path pseudoenergy prediction (which depends on a single parameter) provides a useful, conservative upper bound for most practical absorber designs, provided the absorber damping is small.

scholarly journals Integrated Cross Sections of the Photo-Neutron Reactions Induced on \(^{197}\)Au with 60 \(\text{MeV}\) Bremsstrahlung

2020 ◽  
Vol 30 (1) ◽  
pp. 49
Author(s):  
Nguyen Van Do ◽  
Nguyen Thanh Luan ◽  
Nguyen Thi Xuan ◽  
Pham Duc Khue ◽  
Kim Tien Thanh ◽  
...  
Keyword(s):  
Cross Sections ◽  
Gamma Ray ◽  
Computer Code ◽  
Experimental Results ◽  
Point Energy ◽  
Spectrometric Technique ◽  
End Point ◽  
Theoretical Predictions ◽  
Neutron Reactions ◽  
First Time

Abstract. Seven photo-neutron reactions 197Au(γ,xn)197-xAu (with x=1-7) produced by the bremsstrahlung end-point energy of 60 MeV were identified. In this work, we focus on the measurement of integrated sections. Experiments were carried out based on the activation method in combination with off-line gamma-ray spectrometric technique. The integrated cross sections of the investigated reactions were determined relative to that of the monitoring reaction 197Au(γ,n)196Au. To validate the experimental results, theoretical predictions were also made using the computer code TALYS 1.9. The current integrated cross-sections of the 197Au(γ,xn)197-xAu reactions with 60 MeV bremsstrahlung end point energy are measured for the first time.

scholarly journals Rotor Instability Induced by Radial Clearance in Ball Bearing Supports

1993 ◽  
Author(s):  
Yao-Qun Lin
Keyword(s):  
Experimental Investigation ◽  
Internal Friction ◽  
Natural Frequency ◽  
Computer Simulations ◽  
Ball Bearing ◽  
Rotor Dynamics ◽  
Experimental Results ◽  
Radial Clearance ◽  
Speed Range ◽  
Theoretical Predictions

In rotor dynamics, the rotor nonsynchronous natural frequency vibration, or rotor instability, has been mainly ascribed to two mechanisms, i.e., internal friction effects and fluid actions. It is shown, however, in this paper that the radial clearance in ball bearing supports can also induce rotor instability through an internal-impacts mechanism. The behavior of the rotor with radial clearance in its ball bearing supports is simulated numerically. The computer simulations show that there is a speed range in which the rotor will vibrate at both the synchronous frequency and the natural frequency. Below or above this speed range, the rotor has only the synchronous response and its harmonics. An experimental investigation was conducted to verify this analysis. The experimental results agree well with the theoretical predictions.

scholarly journals The pp → W(→ lν) + γ process at next-to-next-to-leading order

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
John M. Campbell ◽  
Giuseppe De Laurentis ◽  
R. Keith Ellis ◽  
Satyajit Seth
Keyword(s):  
Numerical Results ◽  
Experimental Results ◽  
Tree Level ◽  
Leading Order ◽  
Statistical Errors ◽  
Theoretical Predictions ◽  
Experimental Errors ◽  
Slicing Method ◽  
The One ◽  
First Time

Abstract We present details of the calculation of the pp → W(→ lν)γ process at next-to-next-to-leading order in QCD, calculated using the jettiness slicing method. The calculation is based entirely on analytic amplitudes. Because of the radiation zero, the NLO QCD contribution from the gq channel is as important as the contribution from the Born $$ q\overline{q} $$ q q ¯ process, disrupting the normal counting of leading and sub-leading contributions. We also assess the importance of electroweak (EW) corrections, including the EW corrections to both the six-parton channel 0 →$$ \overline{u} d\nu {e}^{+}\gamma g $$ u ¯ dν e + γg and the five-parton channel 0 →$$ \overline{u} d\nu {e}^{+}\gamma $$ u ¯ dν e + γ . Previous experimental results have been shown to agree with theoretical predictions, taking into account the large experimental errors. With the advent of run II data from the LHC, the statistical errors on the data will decrease, and will be competitive with the error on theoretical predictions for the first time. We present numerical results for $$ \sqrt{s} $$ s = 7 and 13 TeV. Analytic results for the one-loop six-parton QCD amplitude and the tree-level seven-parton QCD amplitude are presented in appendices.

A Theoretical and Experimental Investigation of a Gas Operated Bearing Damper for Turbomachinery: Part II — Experimental Results and Comparison With Theory

1993 ◽  
Author(s):  
Padmanabhan Sundararajan ◽  
John M. Vance
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Vibration Damper ◽  
Theoretical Predictions ◽  
Present Design ◽  
Gas Damper

Abstract This is the second of two papers describing results of a research project directed at developing a gas operated vibration damper for high temperature turbomachinery applications. This part presents the experimental measurements made on three variations of the gas damper hardware and compares them with the theoretical predictions presented in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 13.2 Ib-s/in was measured for a single actuator at a natural frequency of 100 hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.

Accounting for Roller Dynamics in the Design of Bifilar Torsional Vibration Absorbers

2009 ◽  
Author(s):  
Ryan J. Monroe ◽  
Steven W. Shaw ◽  
Alan H. Haddow ◽  
Bruce K. Geist
Keyword(s):  
Equations Of Motion ◽  
Tuning Parameter ◽  
System Response ◽  
Vibration Absorbers ◽  
State Response ◽  
Centrifugal Pendulum Vibration Absorbers ◽  
The Common ◽  
Roller System ◽  
First Time ◽  
Selection Of

Centrifugal pendulum vibration absorbers are used for reducing torsional vibrations in rotating machines. The most common configuration of these devices utilizes a bifilar suspension in which the absorber mass rides on a pair of rollers, whose mass is small compared to that of the absorber. These rollers are typically solid steel cylinders that allow the CPVAs to move along a prescribed path relative to the rotor, determined by the shape of machined cutouts on the rotor and the absorber mass. Previous studies have considered how to account for the roller dynamics in selecting the linear tuning characteristics of the absorber system, but have not quantified the errors induced by the common approximations that either ignores their effects completely, or does not account for the nonlinear aspects of their dynamics. In this paper we systematically investigate these effects. Specifically, we first show that there exists an absorber path for which the absorber/roller system maintains the same frequency of free oscillation over all physically possible amplitudes. This tautochronic path has been well known for the case with zero roller inertia, and herein, for the first time, the corresponding path with rollers is shown to exist and is constructed. In addition, we carry out an analysis of the steady-state response of the rotor/absorber/roller system in order to quantify the effects of various approximations commonly used in regards to the roller dynamics. This analysis is based on the equations of motion, scaled in such a manner so that they are amenable to a perturbation analysis, which includes the effects of rollers in the perturbation terms. It is shown that if one accounts for the linear tuning aspects of the rollers, the system response is essentially insensitive to the selection of the nonlinear tuning parameter, so long as it is close to the tautochronic value. This implies that the approximation commonly used for selecting absorber paths with rollers is adequate.

Nonlinear Transient Dynamics of Pendulum Torsional Vibration Absorbers

2011 ◽  
Author(s):  
Ryan J. Monroe ◽  
Steven W. Shaw
Keyword(s):  
Equations Of Motion ◽  
Torque Converter ◽  
Transient Dynamics ◽  
Circular Path ◽  
Vibration Absorbers ◽  
Approximate Analytical Expression ◽  
Centrifugal Pendulum Vibration Absorbers ◽  
Nonlinear Transient ◽  
System Equations ◽  
Minimal Mass

This paper describes an analytical and experimental investigation of the transient dynamics of centrifugal pendulum vibration absorbers, which are used for reducing torsional vibrations in rotating machines. Recently these absorbers have been proposed for use in automotive engines, to aid with fuel saving technologies such as cylinder deactivation and torque converter lockup. In order for them to operate effectively with minimal mass, they must be designed to allow for large amplitude, nonlinear responses. In this paper we consider the transient dynamics of these absorbers, focusing on the response during startup. During these transient events the absorbers experience a beating type motion, resulting in overshoot of the absorber response before reaching steady state conditions. Using a perturbation analysis of the system equations of motion, an approximate analytical expression for nonlinear overshoot is derived, relating the overshoot to the system and excitation parameters. These predictive results are derived for a general class of absorbers, and are verified by simulations of the full equations of motion and by experiments using a fully instrumented spin rig. It is found that the overshoot for absorbers with softening nonlinearity, such as circular path absorbers, can be well over the 100% upper limit for a linear absorber, and can be as high as 173%. For absorbers with tautochronic paths, the overshoot remains quite close to that of the linearized system, even for large amplitudes. These results provide a useful tool for the design of absorbers to meet transient response specifications.

The Influence of Oil Supply Pressure on the Behavior of a Rigid Symmetrical Balanced Rotor in Journal Bearings With Circumferential Feeding

1992 ◽  
Vol 114 (4) ◽  
pp. 812-817 ◽  
Author(s):  
G. Capone ◽  
M. Russo ◽  
R. Russo
Keyword(s):  
Experimental Investigation ◽  
Journal Bearings ◽  
Experimental Results ◽  
Specific Load ◽  
Static Characteristics ◽  
Supply Pressure ◽  
Film Instability ◽  
Low Load ◽  
Theoretical Predictions ◽  
Load Conditions

A theoretical-experimental investigation was carried out on the behavior of a rigid symmetrical balanced rotor in short, cylindrical, circumferentially fed journal bearings under low load conditions. The influence of supply pressure on bearing static characteristics and oil film instability threshold was evaluated for the above system. The experimental results are shown along with the theoretical predictions of the static characteristics and limit stability curves for different values of the ratio between supply pressure and specific load.

Guided Waves Measurement Techniques in Pitch-Catch Configuration

2020 ◽  
Author(s):  
Francesco Cordella ◽  
Francesco Bertoncini ◽  
Mauro Cappelli
Keyword(s):  
Experimental Investigation ◽  
Theoretical Analysis ◽  
Experimental Method ◽  
Long Range ◽  
Guided Waves ◽  
Measurement Techniques ◽  
Theoretical Background ◽  
Experimental Results ◽  
Discharge Pipe ◽  
Different Types

Abstract Guided waves testing allows a long-range screening in pipes of different types and represents an effective and powerful non-destructing technique for defect detections using a limited number of points of measures. After the characterization through a general theoretical analysis, the focus is set to a real steam discharge pipe with a high mechanical complexity used for many years in a research plant now dismissed. The experimental method applied here is the pitch-catch configuration of two magnetostrictive sensors. The objective of this paper is to establish a strong theoretical background to pave the way for a robust experimental investigation. Preliminary experimental results are consistent with the theoretical analysis.

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