Dry Friction Damping Research Articles

A mechanical calculation model for the nonlinear mechanical behavior of the metal rubber clamp in aero engine

As an important pipeline support component, metal rubber clamp is mainly used for pipeline connection, fixation and vibration isolation. At present, the researches on hysteretic and stiffness characteristics of metal rubber clamps in aero engines are still in their infancy. This work aims to develop a nonlinear mechanical calculation model for metal rubber clamps to effectively capture the nonlinear mechanical properties, such as hysteresis characteristics and variable stiffness behavior. The equivalent stiffness model of metal rubber clamps was established by introducing tightening torque and friction between metal wires as control variables, and the mechanical behavior under repeated loads is analyzed by combining the force and deformation relations of typical hysteretic curves. By comparing the measured hysteretic curve and natural frequencies, the proposed equivalent stiffness model of a metal rubber clamp is verified. This also suggests that the proposed model can effectively simulate the dry friction damping characteristics of metal rubber. In addition, the effects of tightening torque and friction coefficient on hysteretic characteristics and stiffness are also analyzed. The aim of this study is to develop mechanical anisotropy tests integrated with equivalent numerical simulation techniques to elucidate the mechanical characteristics of the aero engine clamp. The research can provide theoretical support for the structural design of metal rubber clamps.

Evaluation of Dynamics of a Freight Wagon Model with Viscous Damping

The aim of this work was to perform a simulation analysis of the dynamics of a freight wagon with a variant vibration damping: dry friction and viscous damping. The following mathematical models of the damping characteristics are presented: the Maxwell model and the Kolsch model. The differences among the types of damping were first analyzed based on the dynamic responses of the 1 DOF model. Simulation studies were then carried out in a VI-Rail environment with the use of S-curved track models comprising short straight sections connecting the curves. The track models differed in the values of curve radii, cant, and length, which made it possible to run at different speeds. The multibody model of the vehicle represents a typical two-axle freight wagon. The dynamics of the wagon model were investigated for two states: empty and laden. Standard kinematic and dynamic values were compared in order to investigate if the nature of the damping has a significant impact on the dynamic properties of a freight wagon. The analysis of the simulation study showed that replacing dry friction damping with the viscous one can generally reduce forces acting on the wheel–rail contact, which, in turn, can be related to improving the running behavior of wagons while reducing the negative impact on the track.

Two-parameter dynamics and multistability of a non-smooth railway wheelset system with dry friction damping.

A deep understanding of non-smooth dynamics of vehicle systems, particularly with dry friction damping offer valuable insights into the design and optimization of railway vehicle systems, ultimately enhancing the safety and reliability of railway operations. In this paper, the two-parameter dynamics of a non-smooth railway wheelset system incorporating dry friction damping are investigated. The effect of the crucial parameters on the complexity of the evolution process is comprehensively exposed by identifying different dynamic responses in the two-parameter plane. In addition, the multistability and the various routes transition to chaos for the system are also discussed. It is found that dry friction induces highly complex dynamics in the system, encompassing a range of behaviors such as periodic, quasi-periodic, and chaotic motions. These intricate dynamics are a direct result of the interplay between multiple parameters, such as speed and damping coefficients, which are critical in determining the system's stability and performance. The presence of multistability further complicates the system, resulting in unpredictable transitions between different motion states.

Numerical and Experimental Study on Dummy Blade with Underplatform Damper

To confirm the variation in damping ratio offered by dry friction dampers against structural vibration stress, this study developed a blade vibration response test system for capturing damping characteristic curves through both frequency sweep excitation and damping-freevibration methods. The damping-free vibration method demonstrates high efficiency, allowing for the acquisition of a complete damping ratio characteristic curve in a single experiment. Experimental findings indicate that the two contact surfaces on the triangular prism damper produce distinct damping effects, closely aligning with the predicted damping characteristic curves. The peak damping ratio was found to be independent of the centrifugal load of the damper; dampers with varying contact areas produce approximately similar damping characteristics; and the damping effect shows a positive correlation with the root extension length.

Robust design of turbine blades with friction contacts in the presence of multiple response levels

Dry friction damping is a widely used solution to mitigate vibrations of turbine blades. At design stage, the computation of the forced response of assemblies of bodies in contact (whose relative motion could result in dry friction damping) could give non-unique solutions due to the possibility of having different static equilibria. Infinite possible vibratory levels in a range are hence possible. A desirable condition for designers is to deal with systems whose response boundaries are not far from each other, i.e. with a low scatter in the response. For systems with multiple vibration levels, the notion of robustness (a robust system has a small response scatter, and viceversa), is particularly important.A robust design is hence needed for such assemblies. Once a design parameter is identified, two possible approaches are possible to accomplish this task.The so-called manual approach explores a certain number of values of the design parameter belonging to a certain interval, and chooses the most robust configuration among those calculated. This computation could result in a huge effort if the number of considered values of the design parameter is high.To overcome this issue, a second approach is here proposed. It is based on a Nested Optimization Algorithm (NOA), which consists in two levels of optimization in order to directly find the most robust configuration in the considered range for the design parameter.In this paper, NOA is applied to a particular test case consisting in a lumped-parameter system simulating three blades with two UPDs interposed among them. Such a system provides the necessary coupling between different contact interfaces necessary to obtain multiple response levels. In addition, it is useful to investigate the mutual interaction among different UPDs.Results of NOA are presented together with the results of the manual approach in order to give a validation of the double optimization. Dependence of the response scatter from the contact states of the interfaces is also investigated.

Nonlinear dynamics of a dual-rotor-bearing system with active elastic support dry friction dampers

Nonlinear dynamics of a dual-rotor-bearing system with active elastic support dry friction dampers

Design of Dry Friction Damper to Reduce Vibration Impacts to Circuit Cards at Critical Frequencies

Design of Dry Friction Damper to Reduce Vibration Impacts to Circuit Cards at Critical Frequencies

The impact of vibration on buildings: Problems and solutions

The article presents a comprehensive overview of a study investigating the influence of soil-foundation interaction on the natural frequencies and vibration safety of reinforced concrete cellular and frame buildings. Through numerical modelling and analysis, the researchers investigate the relationship between structural modes and soil-induced vibrations, emphasizing the sensitivity of vibration frequencies to soil composition. Findings reveal that alterations in foundation conditions can significantly affect building dynamics, particularly in mid-rise structures, highlighting the importance of targeted monitoring for early detection of potential issues. Furthermore, the study discusses the implications of vibrations on human comfort and safety, underscoring the need for effective vibration mitigation strategies. Various damping systems, including hydraulic, dry friction, and dynamic dampers, are proposed as practical solutions to minimize the adverse effects of vibrations on both structures and occupants. Overall, the study underscores the critical role of vibration safety in ensuring the resilience and well-being of buildings and their inhabitants.

Experimental Investigation of the Dynamic Response of a Flat Blade with Dual Dry Friction Dampers

One test rig comprising two blades and dual under-platform dampers (UPDs) was built to enhance the understanding of the dynamic response behavior of blades with dual UPDs. A turnbuckle was applied to enable the smooth and uninterrupted linear adjustment of the normal load on the dual UPDs. Non-contact vibration-response measurements were achieved through eddy-current displacement sensors. Contact excitation was employed using an electromagnetic exciter to determine the magnitude of the excitation load, which was measured using a force sensor mounted on the excitation rod. A feedback system was established to maintain a constant magnitude of the excitation force throughout the excitation process. The chosen experimental variables include the normal load, the amplitude of the excitation force, the effective contact area, and the position of the damper action. The frequency response function of the blade under various experimental parameters was obtained through frequency sweeping under sinusoidal excitation. The influence of each parameter on the dynamic characteristics of blades was studied. The results demonstrate that the double-layer damping system offers distinct advantages over its single-layer counterpart. The upper damping has a wider frequency-adjustment range and a lower resonance amplitude and takes a larger share of the damping efficiency.

Turbine wheel reduced modal model for self-excited vibration suppression by inter-blade dry-friction damping

Turbine wheel reduced modal model for self-excited vibration suppression by inter-blade dry-friction damping

Study on the Forced Torsional Vibration Response of Multiple Rotating Blades with Underplatform Dampers

Underplatform dampers (UPDs), a type of dry friction damper, are commonly used for vibration reduction of turbine blades. This study investigated the effect of UPDs on the forced torsional vibration response of turbine blades within a multi-blade system. Pre-stressed finite element modal analysis and the harmonic balance method were combined to calculate the forced torsional vibration responses of a system with and without UPDs. The experiments were then carried out on a rotating multi-blade system with and without UPDs, with a focus on the effect of mass stacking on damping performance. The results showed that the installation of underplatform dampers could increase the frequency corresponding to the maximum response of the blade torsional vibration and cause multiple peaks that varied in the vibration response based on the mass of the UPDs. With an appropriate normal force, the underplatform dampers could effectively reduce the blade torsional vibration by 68.9%. However, excessive normal force of UPDs could lead to multiple large vibration peaks, which should be avoided in engineering practice. Additionally, the numerical results for the forced torsional vibration response of the rotating multi-blade system with UPDs were relatively close to the experimental results, indicating that the calculation method could be effectively applied to the nonlinear prediction of forced vibrations of rotating blades with dampers.

Sensitivity Analysis of Dry Friction Damper in Stay Cables

The aim of this study is to provide an overview of damper sensitivity with dry friction mechanism in relation to its positioning and force to control cable vibrations in cable-stayed bridges. Finite element method is used to implement the cable model. Decay tangent evaluation takes into account the damper position varying in the first 5% of cable total length. To numerically solve the second-order nonlinear ordinary differential equation, the Newmark method with average acceleration is used. The results indicate the appearance of higher vibration modes with the application of dry friction damping, which can influence the interaction between two dampers. With the application of two dry friction dampers to the same cable using the equivalent viscous damping theory and the Newmark method, it is possible to perceive different results, where dry friction presents a considerable gain when not adapted to the linear viscous damping theory.

Numerical Analysis on Shimmying Wheels with Dry Friction Damper

The dynamics of the 1.5-degree-of-freedom model of towed wheel is investigated. Dry friction at the king pin is considered, leading to a non-smooth dynamical system. Beyond analytical and numerical linear stability analysis, the nonlinear vibrations are investigated by numerical bifurcation analysis with smoothing and by numerical simulations with event handling. The effect of dry friction at the king pin on the birth of separated periodic branches is presented on bifurcation diagrams. The presence of bistable parameter domains is also shown. The effect of smoothing is investigated by comparing bifurcation diagrams of the smoothed and the original non-smooth systems.

Nonlinear dynamics of asymmetrically supported supercritical rotor equipped with a dry friction damper

To suppress the excessive transcritical vibration of a supercritical rotor, dry friction damper is a popular choice especially in rotorcraft and aero-engine design. In the current work, we focus on the nonlinear dynamics of asymmetrically supported supercritical rotor equipped with a dry friction damper and the influence of support asymmetry on damper’s performance. Governing equations of the rotor/damper system, which fully consider the nonlinear rub-impact and side dry friction effects, are derived. Typical results of symmetrically supported rotor/damper systems are firstly demonstrated and quantitatively compared with experimental counterparts to confirm the predicting capability of the nonlinear dry friction damper model. Afterward, influences of asymmetric direct stiffness and skew-symmetric cross-coupling stiffness are discussed. It is found that direct stiffness asymmetry deteriorates the transcritical vibration attenuation capability of the damper but reduces the width of transcritical region. For system with a severer direct stiffness asymmetry, a larger pre-tightening force is suggested to be imposed. Besides, unstable self-excited vibration induced by skew-symmetric cross-coupling stiffness is found to be well-limited by the dry friction damper within entire interested rotational speed range. Moreover, during critical speed transition, the self-excited frequency component is completely suppressed.

Nonlinear vibration response of a helicopter supercritical tail rotor drive shaft equipped with a dry friction damper

PurposeThe supercritical design of tail rotor drive shaft has attracted more attention in helicopter design due to its high power–weight ratio and low maintenance cost. However, there exists excessive vibration when the shaft passes through the critical frequency. Dry friction damper is the equipment applied to the drive shaft to suppress the excessive vibration. In order to figure out the damping mechanism of the dry friction damper and improve the damping efficiency, the dynamic model of the shaft/damper system is established based on the Jeffcott rotor model.Design/methodology/approachThe typical frequency response of the system is studied through bifurcation diagrams, amplitude-frequency characteristic curves and waterfall frequency response spectrum. The typical transient responses under frequency sweeps are also obtained.FindingsThe results show that the response of the system changes from periodic no-rub motion to quasi-periodic rub-impact motion, and then to synchronous full annular rub-impact, and finally, back to periodic no-rub motion. The slip of the rub-impact ring improves the stability of the system. Besides, the effects of the system parameters including critical dry friction force, rub-impact friction coefficient, initial clearance on the stability and the vibration damping capacity are studied. It is observed that the stability changes significantly varying the three parameters respectively. The vibration damping capacity is mainly affected by the critical dry friction force and the initial clearance.Originality/valuePresented results provide guidance for the design of the dry friction damper.

Nonlinear dynamics and stability of the supercritical tail rotor drive shaft with dry friction damper

Due to its high power-weight ratio and low maintenance cost, the supercritical tail rotor drive shaft has attracted more and more attention in helicopter design. The dry friction damper is specifically designed to suppress the excessive vibration of the supercritical shaft when passing through the critical speed. The stability of the shaft/damper system and the vibration damping efficiency are affected by the nonlinear rub-impact process between the shaft and the damper. In order to reveal the damping mechanism and the stability of the shaft/damper system, and to guide the design of the damper, a nonlinear dynamic model of the system is established. Typical responses for systems with different rub-impact stiffness, clearance, rub-impact friction coefficients and critical dry friction forces are obtained by numerically solving the nonlinear governing Equations. The dynamic characteristics and stability of the system are investigated by drawing the bifurcation diagrams, whirling orbits and time history diagrams. It is demonstrated that there exists three forms of rub-impact between the shaft and the friction damper, namely, the forward full annular rub-impact, forward local annular rub-impact and backward local annular rub-impact. The unstable backward full annular rub-impact is not present. With an increasing critical dry friction force and rub-impact friction coefficient, the rub-impact system will easily evolve into the backward local annular rub-impact region which decreases the system's stability. A decreasing clearance or an increasing rub-impact stiffness will induce a similar effect, but the influence of rub-impact friction coefficient and critical dry friction force is more obvious. Moreover, the effects of these four device parameters on the transcritical vibration amplitude are also derived, which will give a useful guidance for the design of the dry friction damper.

Modeling vibration energy transfer of fresh concrete and energy distribution visualization system

This paper combines the working mechanism of internal vibrators and the vibration energy theory to propose an energy transfer model and develops an energy distribution visualization system. The input power of the driving motor is primarily consumed by the damping energy consumption rate of the internal vibrator (DECR-IV) and the energy absorption rate of concrete (EARC). The DECR-IV is generated by the dry-friction damping of the internal vibrator components and the fluid damping between the vibrator casing and concrete. Moreover, the EARC is proportional to the square of the vibrator acceleration, and the EARC accounts for a smaller proportion of the input power; the maximum proportion is only 34.9% in the experimental examples. In addition, the energy rapidly attenuates around the vibrator, and the energy attenuation slows down with increasing the fluidity of fresh concrete; meanwhile, the EARC decreases, but the DECR-IV increases. Furthermore, the energy distribution visualization system is developed utilizing Java and WebGL and is combined with the energy transfer model to quantitatively characterize the vibration energy distribution in fresh concrete. The system and model are applied to a construction site, providing a reliable method for the quality evaluation of vibrated concrete consolidation.

Nonlinear dynamics and stability analysis of dry friction damper for supercritical transmission shaft

Nonlinear dynamics and stability analysis of dry friction damper for supercritical transmission shaft

Efficient Model of the Interaction of Elastomeric Filler with an Open Shell and a Chrome-Plated Shaft in a Dry Friction Damper.

The results of a study of the contact interaction of an open shell and a chrome-plated shaft with elastomeric filler installed coaxially are presented. The considered contact system is a model of the original design of the shell damper of dry friction. The design feature is the following: the bearing link of the damper is a thin-walled cylindrical shell with a cut along the generatrix; the working body of the damper is elastomeric filler; a hollow chrome-plated shaft centers the damper elements and allows it to be used in technological processes with the presence of aggressive and abrasive-containing media. The mechanical-mathematical modeling of the behavior of the presented damper under the conditions of operational loads has been carried out. The idea of identifying the properties of a cut isotropic shell, which bends under the conditions of a nonaxisymmetric contact load, and a strongly orthotropic continuous shell is applied. As a result, dependences were obtained to determine the rigidity and the maximum allowable load of the damper. The effect of the coefficient of friction of the contact pairs elastomer-shell and elastomer-shaft on the damper performance properties has been studied. A technique for the quasi-static analysis of structural damping in non-mobile, non-conservative shell systems with deforming filler has been developed. The hysteresis loops of the damper under a nonmonotonic load are constructed, the dependence of the amount of dissipated energy on the cycle asymmetry coefficient is found. An analysis of the results obtained showed that the use of open shells in friction shock absorbers can significantly reduce their rigidity compared to solid shells and thereby reduce the resonant frequencies of the dynamic system. This circumstance makes such vibration isolators particularly attractive for use in superresonance vibrators as working modules of drilling shock absorbers and elastic hangers of sucker rods in oil and gas production.

All-round responses and boundaries of a shaft and dry friction damper assembly

A helicopter tailrotor driveline is equipped with dampers to suppress the resonance of transmission shafts. A dry friction damper and a slender shaft form an assembly The comprehensive understanding of different responses of the assembly provides the basis for a more reasonable parameter configuration of the damper. To this end, the assembly is modeled as a dynamic system with rub impact between a rotor with continuous parameter distribution and a suspended elastic stator. Boundaries of rub impact and condition of Hopf bifurcation are derived. Pinned natural frequencies and backward whirl frequencies are solved by analytical deduction. The critical speed for triggering a backward whirl with consideration of eccentric excitation is obtained by the multiple scale perturbation method. Then, all-round responses and boundaries are solved by both analytical and numerical approaches based on the parameters of a helicopter. The effects of friction coefficient, internal damping, suspension stiffness, variable impact stiffness, etc. on the boundaries are presented in detail with the discussion of relationships between physical reasons and analytical conditions. Results show that smaller impact stiffness difference and friction coefficient, a greater mass damping ring, moderate suspension stiffness, greater internal and external damping are the key factors for the damper design. This study has reference significance not only for the assembly in a helicopter but also for similar mechanical systems.