Impact Damper Research Articles

Suppression of multiple modal resonances of a cantilever beam by an impact damper

Impact dampers are usually used to suppress single mode resonance. The goal of this paper is to clarify the difference when the impact damper suppresses the resonances of different modes. A cantilever beam equipped with the impact damper is modeled. The elastic contact of the ball and the cantilever beam is described by using the Hertz contact model. The viscous damper between the ball and the cantilever beam is modeled to consume the vibrational energy of the cantilever beam. A piecewise ordinary differential-partial differential equation of the cantilever beam is established, including equations with and without the impact damper. The vibration responses of the cantilever beam with and without the impact damper are numerically calculated. The effects of the impact absorber parameters on the vibration reduction are examined. The results show that multiple resonance peaks of the cantilever beam can be effectively suppressed by the impact damper. Specifically, all resonance amplitudes can be reduced by a larger weight ball. Moreover, the impacting gap is very effective in suppressing the vibration of the cantilever beam. More importantly, there is an optimal impacting gap for each resonance mode of the cantilever beam, but the optimal gap for each mode is different.

Generalized dynamic analysis of structural single rocking walls (SRWs)

SummaryThe investigation of structural single rocking walls (SRWs) continues to gain interest as they produce self‐centering lateral load responses with reduced structural damage. The simple rocking model with modifications has been shown to capture these responses accurately if the SRW and its underlying base are infinitely rigid. This paper advances previous rocking models by accounting for (1) the inelastic actions at or near the base of the SRW and (2) the flexural responses within the wall. Included in the proposed advancements are hysteretic and inherent viscous damping associated with these two deformation components so that the total dynamic responses of SRWs can be captured with good accuracy. A system of nonlinear equations of motion is developed, in which the rocking base is discretized into fibers using a zero‐length element to locate the associated compressive deformations and damage. The flexural deformations of the rocking body are captured using an elastic term, while the impact events are modeled using impulse‐momentum equations. Comparisons with experiments of structural precast concrete and masonry SRWs show that the proposed approach accurately estimates the dynamic responses of different SRWs with and without unbonded posttensioning, for various dynamic excitations and degrees of hysteretic action. Using the proposed approach, a numerical investigation employs different configurations of structural SRWs to quantify the various sources of energy loss, including hysteretic action and impact damping, during various horizontal ground motions.

Size matters - The shell lander concept for exploring medium-size airless bodies

Once addressed as a side topic in planetary exploration, the investigation of small solar system bodies has now become one of the corner stones in the international science community in order to study the formation of the solar system and the evolution of life within. For rendezvous spacecraft, small carry-on landers have proven to be valuable assets, and to have a positive impact on the overall mission cost, by avoiding additional complexity of the main satellite and transferring the risk of close surface maneuvers entirely or at least to some extend to an independent deployable system. However, carry-on landers have been designed currently to land on very small bodies only, but medium-size class objects between diameters of 10–50 km are of great interest as well. In this paper we classify carry-on landers with respect to their touchdown and operational strategy, evaluate the constraints of ballistic deployments for different target bodies as well as identify the niche for using simple honeycomb impact dampers compared to optional retro-propulsion systems. Further, we introduce the system design of an attitude-stabilized Shell Lander using a generic instrument carrier attached to a single ejectable crash-pad with stabilizing capability to protect the instrument carrier from structural damage, limit internal shock loads for sensitive payloads as well as reduce the amount of bounces on the surface. Finally, we present a mission architecture for a reference case to the Martian moon Phobos as well as provide a proof of concept based on laboratory impact tests and a multi-body simulation to analyze touchdown dynamics including terrain interaction, shell-shedding and bouncing.

Design and optimisation of a turning cutter embedded with impact damper

The cutter with large length-diameter ratio has wide applications in machining structural parts with deep cavity and deep hole features. However, chatter occurs as its declined dynamic stiffness. The impact damper has been utilised to suppress machining vibration due to its simplicity and effectivity. A turning cutter with large length-diameter ratio is designed based on embedded impact damper. The dynamic model is built based on mode superposition method. The influence of cutting force and damping parameters on velocity response status (linear and nonlinear) is analysed. Design parameters of the impact damper are optimised numerically for achieving linear response. Finally, modal tests and machining tests are conducted. The experimental results show that the surface roughness of workpiece (aluminium alloy 7075) is decreased from Ra 1.95 μm to Ra 1.28 μm when the spindle speed n = 500 r/min, feed rate f = 0.05 mm/r, and cutting depth ap = 0.40 mm.

Design and optimisation of a turning cutter embedded with impact damper

Design and optimisation of a turning cutter embedded with impact damper

Design and experimental evaluation of an impact damper to be used in a slender end mill tool in the machining of hardened steel

In the manufacture of molds and dies, it is, sometimes, necessary to mill deep cavities with complex geometries. Therefore, tools with a large length/diameter ratio (L/D) are usually used in these processes, which stimulate tool vibration. The goals of this study are to develop a tool with an impact damping system and verify the effectiveness of this system applied to the cutting tool in high-speed milling operations of hardened steel. Aiming this goal, a ball nose end mill with L/D ratio of 7 was used, machining a curved, convex surface of hardened steel. Results of workpiece roughness, variation of cutting forces and tool wear when using the cutting tool with and without the damping system were compared. In addition, three diameters of steel spheres (used as elements to produce impact) were tested in the damping system. The results showed differences in the workpiece roughness and variation of the cutting forces when using the tool with and without the impact damper and the influence of the size of the spheres on the damping effect, mainly in the region of tool-workpiece contact with more tendency to generate vibration. The main conclusions were that the use the impact damping system used is really effective to decrease tool vibration, and the bigger the spheres used in the damper, the higher is their effects to damp the system.

Dynamic characteristics of magnetorheological fluid squeeze flow considering wall slip and inertia

Magnetorheological fluid has been investigated intensively nowadays, and magnetorheological fluid shows large force capabilities in squeeze mode with wide application potential such as control valve, engine mounts, and impact dampers. In these applications, magnetorheological fluid is flowing in a dynamic environment due to the transient nature of inputs and system characteristics. Hence, this article undertakes a comprehensive study of magnetorheological fluid squeeze flow dynamics behaviors with wall slip, yield, and inertia. First, the dynamic model with the bi-viscous constitutive of magnetorheological fluid squeeze flow including wall slip and inertial force is presented. Then, the mathematical model is validated, matching magnetorheological fluid squeeze dynamic test results very well. Finally, the dynamics behavior and mechanism of magnetorheological fluid squeeze flow with inertia, yield, and wall slip are explored. Results show that (1) increasing yield stress and decreasing initial gap will increase the magnetorheological fluid vertical force greatly; (2) the wall slip affects the yield surface of magnetorheological fluids in the squeeze zone and affects the squeeze force; (3) the inertial force is increasing tremendously as the increased excitation frequency and yield stress and should be included with high-frequency excitation or yield stress.

Wood Plastic Composites Produced from Postconsumer Recycled Polystyrene and Coconut Shell: Effect of Coupling Agent and Processing Aid on Tensile, Thermal, and Morphological Properties

Expanded polystyrene (EPS) has been widely used as a disposable packaging material in many industries thanks to properties like low density, lightweight, high impact, and vibration damping. Although usage of EPS increases annually, recycling facilities often refused to process postconsumed EPS due to the poor economic viability associated with high logistics and transportation cost in collection, storage, and shipment of the material. The objective of this research is to enhance the value chain of postconsumed EPS by investigating its potential as feedstock in the development of sustainable wood plastic composites (WPC), thereby providing an attractive business opportunity that also increases interest in EPS recycling and indirectly continue the lifespan of disposed EPS. Varying compositions of recycled polystyrene (rPS), coconut shell (CS), maleated polystyrene (MAPS) and Ultra‐Plast WP516 were compounded using a HAAKE internal mixer and compression molded to form WPC. The effects of material formulation on mechanical, thermal, and morphological properties of the composites were studied. The experiment showed that WPC formulated with 100 phr of rPS, 30 phr of CS, 3 phr of MAPS, and 1 phr of Ultra‐Plast WP516 possesses higher modulus and tensile strength compared to the neat EPS, measured at 2.5 GPa and 27.5 MPa, respectively. Although the WPC experienced initiation of thermal degradation at a temperature lower than neat rPS, but the thermal stability of rPS/CS composites containing varying composition of MAPS and Ultra‐Plast WP516 was better at high temperature. Furthermore, a 50% weight loss took place at a higher temperature. Nevertheless, the glass transition temperature of the rPS/CS composite with addition of MAPS and Ultra‐Plast WP516 was found lower than the neat rPS. POLYM. ENG. SCI., 60:202–210, 2020. © 2019 Society of Plastics Engineers

On the numerical simulations of amplitude-adaptive impact dampers

Two impact dampers are analysed and compared with respect to their effectiveness for vibration reduction. Estimations of nonlinear system behaviour are derived using only well-known solutions for a linear dynamic vibration absorber. Critical parameter values separating domains with qualitatively different system behaviours are found. Using numerical simulations, the estimations are verified and the influence of each system parameter on the vibration amplitudes is investigated individually. Each of these systems exhibits advantages in the suppression of particular resonances, because they react either to the absolute or relative motion within the system.

음향블랙홀 파동 전달 특성을 이용한 굽힘진동 저감용 충돌 댐퍼

음향블랙홀 파동 전달 특성을 이용한 굽힘진동 저감용 충돌 댐퍼

Modeling of Impact Damping Effect on Hypoid Gear Dynamic Response

Abstract An enhanced hypoid gear mesh model that incorporates the Hertzian impact damping function is developed in this study to reveal the mechanisms of damping during gear mesh. Two types of impact damping models, namely, viscous and nonviscous type based on the first principle of mechanics, are compared to previous empirical damping models with a constant damping coefficient. Parametric studies are performed for both steady-state and transient analyses to investigate the impact damping effect under numerous load conditions or physical parameters of a meshing gear pair. Comparative study between viscous and nonviscous damping models is also performed to examine their effects on dynamic response for various load levels. It is shown that impact damping can significantly reduce the amplitude of the dynamic mesh force. Nonviscous damping has more significant effect on the dynamic response under heavy torque load due to the influence of greater elastic deformation. Furthermore, it is observed that impact damping can turn double-sided impact into single-sided impact and suppress response peaks in a certain mesh frequency range during speed ramp up.

Effect of phenyl content, sample thickness and compression on damping performances of silicone rubber: A study by dynamic mechanical analysis and impact damping test

The relaxation behaviors and impact damping effects of phenyl silicone rubber were investigated using dynamic mechanical analysis (DMA) and a home-designed impact damping test. The effects of rubber phenyl content, sample thickness and compression on the damping performance were evaluated. DMA results over a broad temperature and frequency range indicate that silicone rubber with higher phenyl content would overall exhibit better damping capacity owing to the increase in friction between molecular chains, and the impact damping performances agree well with the relaxation results. Besides, sample thickness and compression will also strongly influence the damping performances as directly evidenced by the impact damping tests. It is demonstrated that a combination of DMA and impact damping test is of critical use for designing rubber damping devices according to the frequency range of interest. This work will provide deeper insight into damping performances of rubbers and practical guidance for their engineering applications.

Research of mechanical model of particle damper with friction effect and its experimental verification

Particle damping (PD) technology has a remarkable effect in reducing vibration and noise for high frequency vibration such as mechanical analysis and aviation, and has been widely applied in some engineering practices. However, in the field of low frequency and low amplitude vibration control for building structures, the research and application of particle damper technology is still in the preliminary stage. The deficiencies and problems mainly include the mechanical model of PD is not perfect enough and the mechanism of vibration reduction is not clear enough. In the light of the shortcomings of the existing theoretical model of the PD, a mechanical model of the PD with friction effect between the particle and the structure is proposed, and the analytical solution of the displacement response for the mechanical model subjected to harmonic excitation is obtained. The model can fully represent the collision and non-collision process of PD, and the phase trajectories can embody the complex nonlinear characteristics of PD. The theoretical and motion characteristics of the PD are verified by the electromagnetic shaking table test of a single-story steel frame with PD, which proves the rationality of the theoretical model and the correctness of the analytical results, as well as the necessity of considering the friction effect. The parameters of mass ratio, excitation amplitude, excitation frequency and motion gap are further analyzed, so the mechanism of vibration reduction is clearer. Finally, compared with the traditional model of impact damper, it is obvious that the mechanical model of PD with friction effect can more reasonably evaluate the damping performance in practical engineering.

Models for Materials Damping, Loss Factor, and Coefficient of Restitution

Common parameters between metallic and polymeric materials are the coefficient of restitution, the damping coefficient, and loss factor. Although the relationship between the coefficient of restitution and the loss factor is quite direct, their dependence on the damping coefficient is not so simple and mainly affected by the adopted model used to describe the material response under impact. In the present study, Kelvin–Voigt linear model and Hunt–Crossley complex model are analyzed to describe how the coefficient of restitution depends on the viscous damping coefficient of impact. The correlation between the theoretical models and the experimental data is also shown. A simple method to predict the impact damping factor of both polymeric and metallic materials from the measured temporal signal of the impact force is demonstrated.

Studies on vibration control effects of a semi-active impact damper for seismically excited nonlinear building

The semi-active impact damper (SAID) is proposed to improve the damping efficiency of traditional passive impact dampers. In order to investigate its damping mechanism and vibration control effects on realistic engineering structures, a 20-story nonlinear benchmark building is used as the main structure. The studies on system parameters, including the mass ratio, damping ratio, rigid coefficient, and the intensity of excitation are carried out, and their effects both on linear and nonlinear indexes are evaluated. The damping mechanism is herein further investigated and some suggestions for the design in high-rise buildings are also proposed. To validate the superiority of SAID, an optimal passive particle impact damper (PIDopt) is also investigated as a control group, in which the parameters of the SAID remain the same, and the optimal parameters of the PIDopt are designed by differential evolution algorithm based on a reduced-order model. The numerical simulation shows that the SAID has better control effects than that of the optimized passive particle impact damper, not only for linear indexes (e.g., root mean square response), but also for nonlinear indexes (e.g., component energy consumption and hinge joint curvature).

Nonlinear vibration of crowned gear pairs considering the effect of Hertzian contact stiffness

This study aims to analyze the influence of lead crowning modification of teeth on the vibration behavior of a spur gear pair. Two dynamic rotational models including an uncrowned and crowned gear are examined. Hertzian mesh stiffness is computed using tooth contact analysis in quasi-static state along a complete mesh cycle of teeth mesh. The dynamic orbits of the system are observed using some useful attractors which expand our understanding about the influence of crown modification on the vibration behavior of the gear pair. Nonlinear impact damper consists of non-integer compliance exponents identify energy dissipation of the system beneath the surface layer. By augmenting tooth crown modification, the surface penetration increases and consequently normal pressure of the contact area becomes noticeable. Finally, the results show modification prevents gear pair to experience period doubling bifurcation as the numerical results proved. Using this new method in dynamic analysis of contact, broaden the new horizon in analyzing of the surface of bodies in contact.

Assessment of abrasive powder behaviour during impact-abrasive wear of PCD elements

One of the most suitable renewable energy sources is geothermal energy (providing heating as well as electricity). In order to achieve a suitable depth of drilling (several kilometres), it is required to increase the wear resistance, durability and reliability of key components of the deep drills. The effect of abrasive powders on impact energy transmission and/or damping during wear of Polycrystalline Diamond (PCD) cutting elements was evaluated due to its highest resistance in abrasive conditions. The characteristic features of wear mechanism are presented and discussion is supported by SEM images and EDS maps. The strength of silica sand, quartzite, granite, basalt, marble, limestone, pumice is compared to the force transmitted through the contact zone, damping characteristics and stiffness of abrasive particles. It was found that the laboratory impact-abrasive device enables to initiate damage, characteristic for specific abrasive powder, imitating drilling of such mineral. The mechanism of wear of PCD elements in impact-abrasive conditions depends on the strength and shape of abrasive particles as well as on their behaviour during impact (impact energy damping). The wear of PCD elements in the impact-abrasive conditions was close to zero and their use in new generations of deep drills is expected.

Optimal porosity for impact squeeze of soft layers imbibed with liquids

Abstract During last two decades it was theoretically and experimentally proved that the fluid squeeze out from a soft and porous layer under the action of an external impact load produces high lifting forces. For high porosity, the elastic forces generated by the solid phase are negligible. The mechanism, strongly dependent on permeability variation with layer compression, can be used for shock absorbing devices. One of the key parameters for maximum impact damping is the initial porosity of the soft layer. This analysis provides a simple, analytical solution for optimum initial porosity that minimizes the peak impact force, for impact squeeze between two perfectly rigid and impermeable flat disks of a highly compressible porous layer imbibed with Newtonian liquid. The solution is based on a quasi-static Darcy flow approach. The comparison of predicted values with the experimental data from impact tests made on a gas gun test-rig, show good agreement for medium impact speed.

Investigation into the linear velocity response of cantilever beam embedded with impact damper

The impact damper causes momentum exchange between the primary structure and impact mass, and achieves vibration attenuation through repeated collisions. A cantilever beam embedded with the impact damper is modeled in the form of a continuous system, and the equations of motion are formulated based on the mode superposition method. The mechanism of the impact damper is investigated, and linear velocity response is achieved by a proper selection of a mass ratio of 8.4%, clearance within 0.30 mm, and excitation force ranged from 3.2 N to 5.5 N. The reverse collision has higher damping than co-directional collision, based on which a new criterion of response regimes is proposed for the design of the impact damper. The velocity responses of the damped cantilever beam under sinusoidal and impulse excitation are simulated and verified via the sinusoidal sweep experiments. The velocity amplitudes of the damped cantilever beam are linearly decreased when the clearance is increased within 0.30 mm. Finally, linear and nonlinear velocity responses of the damped cantilever beam are discussed. It is found that the nonlinear velocity response reaches larger damping, but that a strongly modulated response exists.

Experimental Study on Vibration Control of Suspended Piping System by Single-Sided Pounding Tuned Mass Damper

Suspended piping systems often suffer from severe damages when subjected to seismic excitation. Due to the high flexibility of the piping systems, reducing their displacement is important for the prevention of damage during times of disaster. A solution to protecting piping systems during heavy excitation is the use of the emerging pounding tuned mass damper (PTMD) technology. In particular, the single-sided PTMD combines the advantages of the tuned mass damper (TMD) and the impact damper, including the benefits of a simple design and rapid, efficient energy dissipation. In this paper, two single-sided PTMDs (spring steel-type PTMD and simple pendulum-type PTMD) were designed and fabricated. The dampers were tested and compared with the traditional TMD for mitigating free vibration and forced vibration. In the free vibration experiment, both PTMDs suppressed vibrations much faster than the TMD. For the forced vibration test, the frequency response of the piping system was obtained for three conditions: without control, with TMD control, and with PTMD control. These novel results demonstrate that the single-sided PTMD is a cost-effective method for efficiently and passively mitigating the vibration of suspended piping systems. Thus, the single-sided PTMD will be an important tool for increasing the resilience of structures as well as for improving the safety of their occupants.