A Drill Rod Coulomb Friction Damper

2012 ◽  
Author(s):  
Henry A. Scarton ◽  
Anne R. Guthrie ◽  
Kyle R. Wilt
Keyword(s):  
Noise Reduction ◽  
Decay Time ◽  
Coulomb Friction ◽  
Reduction Potential ◽  
Friction Damper ◽  
Peak Acceleration ◽  
Transverse Bending ◽  
Modes Of Vibration ◽  
Reverse Taper ◽  
Bending Modes

A Coulomb friction damper, consisting of a case-hardened roll-threaded collar resting against a reverse taper segment of drill rod, is studied for its noise-reduction potential. Axial impact causes the drill rod to be excited in many transverse bending modes of vibration, along with longitudinal and torsional resonances. Due to the inertia of the collar, simultaneous axial and rotational self-tightening motion occurs on the rolled thread. The collar consequently presses on the case-hardened tapered surface of the drill rod, inducing interfacial frictional rubbing, resulting in 5–45 dB of attenuation in peak acceleration of the modes of vibration, and reduction in decay time on the order of 10 seconds.

scholarly journals Optimization of Friction Damper Weight, Simulation and Experiments

1997 ◽  
Author(s):  
Gabor Csaba ◽  
Magnus Andersson
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Friction Damper ◽  
High Pressure Turbine ◽  
Coupled Modes ◽  
Modes Of Vibration ◽  
Damper Design ◽  
The Right

A new friction damper has been designed by Volvo Aero Corporation. It is used in the high pressure turbine stage of a turbojet engine. The objective of this paper was to find the optimal weight of the new damper that minimizes the blade response amplitude for six and nine engine order excitation and to compare the new damper design with that currently used. Another objective was to compare how well simulation results agree with experimental results from spin pit tests. Simulations were made with a damper model that incorporates the possibility of both micro- and macro-slip in the blade-damper contact interface. Turbine blades were modeled using finite element beam elements. Experimental data were provided from spin pit tests with a completely bladed high pressure turbine rotor. Results show that the simulation model can be used to give qualitative results but has to be further developed to incorporate mistuning effects and coupled modes of vibration for the blade. The spin pit test shows that the new damper design is more efficient in reducing resonance stresses than the old design. It was not possible to see if simulations predict the right optimal damper weight by comparing with experimental data because the rotor could not be excited up to the design point.

Dynamic Analysis of a Valve Spring With a Coulomb-Friction Damper

1990 ◽  
Vol 112 (4) ◽  
pp. 509-513 ◽  
Author(s):  
R. S. Paranjpe
Keyword(s):  
Finite Difference ◽  
Difference Scheme ◽  
Finite Difference Scheme ◽  
Coulomb Friction ◽  
Distributed Parameter ◽  
Friction Damper ◽  
Equivalent Viscous Damping ◽  
Valve Spring ◽  
Coulomb Damping ◽  
Explicit Finite Difference

The dynamic behavior of a distributed parameter valve spring with Coulomb damping has been modeled. Such a spring is described by a nonlinear, nonhomogeneous wave equation. This equation is solved using an explicit finite difference scheme. Some sample results are presented. The results of the finite difference scheme are compared with the results of an analytical solution for zero damping. The two compare very well. The spring is also modeled using an equivalent viscous damping coefficient. The results of this analysis are compared with those of the Coulomb damping analysis.

An Advanced Damper Model for the Dynamics of Dry Friction Damped Systems

1999 ◽  
Author(s):  
Jérôme Guillen ◽  
Christophe Pierre ◽  
Thomas Lagrange
Keyword(s):  
Stiffness Matrix ◽  
Structural Systems ◽  
Friction Damper ◽  
Stick Slip ◽  
Bladed Disk ◽  
Hybrid Frequency ◽  
Modes Of Vibration ◽  
Frictional Interface ◽  
Resolution Algorithm ◽  
Damped Systems

Abstract In this work, a new, flexible friction damper model is introduced, for application to turbomachinery bladed-disk assemblies. The damper is modeled as a massless structure characterized by a stiffness matrix. It is connected to two (possibly more) structural systems at an arbitrary number of friction points where slip can occur. A new procedure is presented to calculate the force transmitted by the damper at each frictional interface. The multi-harmonic, hybrid, frequency/time method introduced previously by the authors, along with the Broyden resolution algorithm, are modified to handle this advanced damper model and to predict the steady-state periodic response of the system. The method is successfully applied to a four-degree of freedom friction damper connecting two beams at four frictional points. Several interesting features of the non-linear response are revealed, such as: situations where the damper slips at some frictional points and sticks at the other points; and complexity of the frequency response of the system, due to the existence of several modes of vibration that correspond to combinations of stick/slip motions at the various frictional interfaces.

Analysis of Actively Controlled Coulomb Damping for Rotating Machinery

1999 ◽  
Author(s):  
John M. Vance ◽  
Luis A. San Andrés
Keyword(s):  
Coulomb Friction ◽  
Critical Speed ◽  
Vibration Suppression ◽  
Friction Model ◽  
Rotating Machinery ◽  
Friction Damper ◽  
Control Laws ◽  
Coulomb Damping ◽  
Coulomb Type ◽  
Coulomb Friction Model

Attempts have been made in the past to use Coulomb damping for vibration suppression in rotating machinery. Typically, a dry friction damper is designed to operate on a flexible bearing support. These designs have usually been unsuccessful in practice, partly because the Coulomb coefficient changes with temperature, with ingress of dirt or lubricant, and with the surface wear conditions. It is known that purely Coulomb damping forces cannot restrain the peak rotor whirl amplitudes at a critical speed. The invention of a disk type of electroviscous damper, utilizing a fluid with electrorheological (ER) properties, has recently revived the interest in Coulomb type dampers. Several investigations have suggested that a Coulomb friction model was the best representation for an ER damper with voltage applied. This model was used to study the feasibility of developing actively controlled bearing dampers for aircraft engines. This paper analyzes the imbalance response of two different rotordynamic models with Coulomb friction damping and shows the benefit of adding active control. Control laws are derived to achieve minimum rotor vibration amplitudes while avoiding large bearing forces over a speed range that includes a critical speed. The control laws are derived for purely Coulomb type of damping and assuming a combination of Coulomb and viscous damping effects. It is shown that the most important feature of Coulomb damping for minimal rotordynamic amplitude response is the control of rotor support stiffness, i.e. leading to the relocation of critical speeds, rather than control of a damping coefficient.

Sign in / Sign up

Export Citation Format

Share Document