Impact Damper Research Articles

Reduction of impact vibration by momentum exchange impact damper using electromagnetic force

Reduction of impact vibration by momentum exchange impact damper using electromagnetic force

A New Type Of Impact Damper With Long Overhangs In The Internal Turning Of Hardened Materials.

The performance of this impact damper with three different sizes of spheres was compared to the performance of a solid steel bar, in terms of workpiece surface roughness, tool vibration and tool life. The main conclusion of this work is that the use of the kind of impact damper tested in this work makes possible the increase of the tool overhang (tool length outside the machine turret) without damaging surface roughness and tool life and, consequently, it also makes the turning of longer holes possible than when a solid bar is used.

The Function of Horn Ridges for Impact Damping

This study investigates the role of ridges of ram horns with regard to damping of mechanical impacts arising from ramming. We measured ram horn ridges from eight specimens of six different species and analyzed the ridges’ pitch distributions. Also, using finite element analysis, a ridged horn model was compared with a non-ridged horn model. The results demonstrate three functions of ram horn ridges; 1) transferring longitudinal waves to shear waves, 2) filtering out shear waves, and 3) stabilizing structures by reducing excessive strain.

Research on chattering occurrence condition in a vibro-impact system

Chattering in the impact damper refers to a continuous impact phenomenon during vibration. This paper establishes the dynamic model of the nonfixed constrained vibro-impact system on the base of cl...

Evaluating the use of a new type of impact damper for internal turning tool bar in deep holes

In internal turning operation of long holes, the tool is not rigid, since it must be out from the lathe turret in a length longer than the machined hole length. This problem is even more serious in the internal turning of hardened steels, where the requirements for surface quality are more restrict, due to the fact that this is a finishing operation, which aims to replace grinding. Therefore, some procedures have to be taken in order to minimize vibration and, consequently, to make the attainment of a good workpiece surface quality possible. One of these procedures is the use of a damped tool. In this work, we tried a simple and different kind of impact damped tool bar, using spheres placed in a cavity manufactured in the tool bar. The performance of this impact damper with three different sizes of spheres was compared to the performance of a solid steel bar, in terms of workpiece surface roughness, tool vibration, and tool life. The main conclusion of this work is that the use of the kind of impact damper tested in this work makes possible the increase of the tool overhang (tool length outside the machine turret) without damaging surface roughness and tool life and, consequently, it also makes possible the turning of longer holes than when a solid bar is used.

Impact damping ratio of a nonlinear viscoelastic foam

Damping is an important parameter to measure the energy dissipated by a cushion foam during an impact. Damping is commonly characterized by damping indices such as damping ratio, loss factor, and tangent of the phase lag. In general, these indices are defined based on steady-state harmonic oscillations of a single degree of freedom, linear viscoelastic model, with an inertia and low damping. When any of these assumptions are violated, the simple linear relationships relating the different damping indices are no longer valid. A steady-state linear model is not well suited for describing impact damping of nonlinear cushion foams. This study reviews classical damping theory and linear and nonlinear viscoelastic models, and proposes a contact force law based nonlinear viscoelastic model for modeling drop platen tests (impact) of a cushion foam. Based on this nonlinear model, a mathematical relationship between the specific damping capacity and damping ratio is formulated. Drop platen tests were carried out under different loading weights and drop heights. The raw data were channeled into dynamic force-deflection curves for calculating analytically specific damping capacity and impact damping ratio. The raw data were also imported into Matlab to develop the numeric impact model for calculating the impact damping ratios. The results show that the nonlinear viscoelastic model, both analytic and numeric, yield damping ratios that are 3–5 times larger than the linear viscoelastic model. The proposed nonlinear viscoelastic model is shown to be an effective tool to describe impact damping and cushion characteristics of a polymer foam. For cushion design, damping ratios of a nonlinear cushion foam are affected by loading weight and strain rate. In addition, the analytical computation of damping ratio, ζ, from specific damping capacity, D, opens up the possibility to project impact damping ratios based on quasi-static compression tests.

Investigation of the stability on boring tool attached with double impact dampers using Taguchi based Grey analysis and cutting tool temperature investigation through FLUKE-Thermal imager

This article focuses on the investigation of machining characteristics of double impact dampers attached with boring tool and grey relational analysis (GRA) based multi-objective optimization for lower tool wear and better cutting force. Taguchi based orthogonal array method was exploited to formulate the experimental plan for the boring operation. Considering impact damper positions, speed and depth of cut as the input control factors, the output responses such as cutting force and tool wear were obtained from the L27 orthogonal array. ANOVA results exposed that damper position and speed had more effect on tool wear and cutting force respectively than depth of cut. Based on the obtained output response for cutting force and tool wear a comprehensive mathematical model was developed. The developed mathematical model for tool wear and cutting force predicted values similar to that of experimental results. The obtained result was corroborated clinched Fluke thermal image analyzer. Thermal imaging result showed that the optimized cutting conditions gives low tool temperature there by reduced tool wear can be obtained. Multi-objective criteria optimization was done through GRA technique and the recommended optimum parameters set provides better cutting force (Cf) of 342.47 N and less tool wear (Tw) of 0.22 mm.

Design and experimental analysis of new industrial vibration dampers

Vibration dampers are the first line of defense against shock and impacts sustained by mechanical and structural systems. Consequently, for decades, new impact damping technologies have been developed and applied in several engineering fields to attenuate undesired vibrations. Linear particle chain (LPC) impact dampers are the latest category of impact dampers being developed for the mitigation of unwanted vibrations in many systems. However, the challenges associated with prototyping such devices made their application in practical systems very limited. This paper proposes five innovative designs for the LPC impact dampers satisfying a wide range of industry needs in terms of efficiency, cost, and sustainability. The proposed designs are fabricated and tested under the same conditions to assess their efficiency in attenuating the vibration of a simple structure. Each design showed consistent behavior, but some designs outperformed others depending on the geometry, physical characteristics, and type of structure. The detailed design, experimental study, and time response comparisons are presented here to provide an initial study towards the development of practical sustainable LPC vibration dampers for real engineering applications.

Stiffness and Damping Formulations for Jointed Deployable Space Truss Structure

In this paper, the dynamic behaviors of a elastic rod connected by a joint with clearance of deployable truss structures are investigated. A one-dimensional cantilever with joint support is examined in the deployable truss structure. These formulations consist of the nonlinear joint dynamic stiffness model and damping models are formulated and the dynamic characteristics of free-vibrating structures are estimated. The natural frequency transitions are investigated by considering the contact and noncontact conditions of the clearances, then the formulation of dynamic stiffness model is obtained. The friction models are mathematically formulated and simplified to make them easy to calculate. The impact damping models are formulated using the linear envelope of the time response and it can be negligible when the speed is small. The dynamic characteristics can be estimated by integrating these models and formulations using the energy loss factors. Experimental evaluations show the dynamic characteristics and demonstrate the validity of the formulations.

Dynamical mechanical characterization of a nanostructured vibration damping layer

A vibration damping layer can dissipate relatively large amounts of energy. A known effect of this dissipation of energy is the reduction of the response of a structure to sound and vibration excitation and the reduction of the transmission of sound through structures at high frequencies. Added damping also increases the impedances of structures at their resonances and thus may improve the effectiveness of vibration isolation at these resonances. It has been observed that the molecular behavior of new nanomaterial composites may have significant influence on their shock and vibration insulation properties. Dynamical mechanical characterization of these nanostructured materials is important for determining the potential application as a viscoelastic vibration damping layer. In this work, inclusion of several nanostructures to thermostable polyurethane has been made and their main elastic properties have been measured using current standard methods. It is observed that specific amounts of nanostructures can improve the impact damping capabilities of the material, with the advantage of reduced thickness and weight as compared to traditional materials.

Research on a New Particle Impact Damper

The conventional impact damper cannot completely exhaust vibration energy through momentum exchange and friction. To overcome these shortcomings, this paper proposes a new particle impact damper (PID) which for the first time introduces the fine particle plastic deformation as an irreversible energy sink. Then, the experiments of the cantilevered beam with the CID and that with the PID are respectively carried out to investigate the behaviour of PID. The experimental results indicate that the PID has a better performance in vibration damping than the CID. And the PID works well in control of the vibration with frequency lower than 50 Hz, which is absent to the non-obstructive particle damper. Thus, the PID has a bright and significant application future because most of the mechanical vibration falls in the range of low frequency.

Investigations of Particle Impact Damper with Elastic Support

Compared with traditional impact damping devices, particle impact damper under elastic support, a new impact damper with double damping structure, has better damping performance. For the purpose of further studying its damping effects on cantilever beam, this paper comes up with both the dynamic model and the movement differential equation of the particle impact damper system with elastic support, and stimulates the damping effects of cantilever beam under the influence of this device. Simultaneously, based on experiments on the damping effects of the particle impact damper with elastic support under five different stiffness conditions, it is concluded that: results from the theoretical calculation basically agree with those from experiments, which verifies the reliability of the calculation model of the particle impact damper with elastic support built by this paper.

Performance-based optimal design of tuned impact damper for seismically excited nonlinear building

This paper proposes a performance-based optimal design method for a tuned impact damper system, which is composed of a solid mass in a container and is located at the top of a 20-story complex nonlinear benchmark building of the third generation. This benchmark building is a steel frame, accounting for nonlinear response via material non-linearity (bi-linear hysteresis) concentrated at the ends of moment-resisting beam-column joints, and is designed for the SAC PhaseIIISteel Project. In order to illustrate the real-world implementable optimal design approach for designing an optimal tuned impact damper system attached to practical complex structures, a reduced-order data-driven physical model is developed by using the response data specifically from finite element model and the optimization-based parameter identification algorithm. The reduced-order model has been iteratively constructed to be consistent favorably with the finite element model on the aspects of both modal frequencies and mode shapes. Based on the reduced-order model, the optimal parameters of the tuned impact damper system are subsequently designed by adopting proposed performance indices and the differential evolution algorithm conveniently. The optimal vibration control effects are evaluated by using the original finite element model structure with the optimal tuned impact damper. Such optimal performance is also compared with that of the original finite element model with a conventionally designed tuned impact damper system. The results show that the optimal designed tuned impact damper system not only can significantly mitigate the peak and root mean square values of dynamic displacements, but also can reduce effectively the number of plastic hinges of the nonlinear benchmark structure compared with that with the conventional design. Furthermore, the performance-based optimal design can lead to a better robust performance of the tuned impact damper system in the cases of the main structure subjected to unknown earthquake excitations.

Vibration Suppression of Cantilever by Impact Damper

Vibration Suppression of Cantilever by Impact Damper

A concept of smart multiaxial impact damper made of vacuum packed particles

The conceptual design of smart crash energy absorber made of Vacuum Packed Particles (VPP) is presented in this work. This structure is composed of granular material inside a plastomer sleeve. The absorber can change the flexural stiffness and as a result the amount of dissipated energy depending on the impact conditions. The special properties of the granular structure create the possibility of various applications as different working modes can be used. When the pressure inside is equal or higher than atmospheric pressure the system behaves similarly to a liquid, otherwise it has properties similar to viscoplastic solid. The physical properties of the structure may be rapidly changed by adjusting the pressure inside the system. Due to these properties Vacuum Packed Particles is considered to be a smart material.

Performance of Prototype Pneumatic Boxing Gloves under Two Different Conditions of Target Padding

The impact damping capabilities of four different boxing gloves were assessed under two different conditions of target padding to determine whether target characteristics might influence previous conclusions concerning potential for impact mitigation through novel glove design. A conventional 10 oz glove (Std 10 oz), a conventional 16 oz glove (Std 16 oz), a prototype pneumatic glove with a sealed bladder (SBLI) and a prototype pneumatic glove with a bladder allowing air exchange with the external environment (ARLI) were each dropped three times on to a force plate from six heights ranging from 2.5 to 5.0 metres. The force plate was covered by a 50 mm thick mat of EVA material and results obtained were compared with those of an earlier experiment involving use of a similar protocol but a 25 mm thick EVA force plate covering. The thicker mat greatly reduced peak impact forces for all gloves, with values for the Std 10 oz glove becoming much closer to those reported by other researchers for punches delivered by elite boxers to crash test manikins. Peak rates of force development were also substantially decreased. Protective effects provided by the ARLI glove relative to the Std 10 oz glove were diminished but still in the order of 17% - 22% for peak impact force and 27% - 49% for peak rate of force development across the range of drop heights. With the 50 mm mat thickness, the SBLI glove was as effective as the ARLI glove in reducing peak impact force, whereas this was not the case with the 25 mm mat. It was, however, always inferior to the ARLI glove in decreasing peak rate of force development. The ability of the ARLI glove to afford protection across a spectrum of impact conditions could yield important practical advantages.

Investigation of chattering behavior of impact damper

Impact dampers are able to reduce vibration effectively through impacts and thus have wide applications in mechanical control. This work investigated the chattering behavior of a two-degree-of-freedom impact damper. Chattering is a phenomenon of continuous collisions within a short time. A theoretical model was developed to obtain the completing position and time of chattering. The fourth-order Runge–Kutta method was adopted to numerically solve the model. The results of bifurcation diagram and temporal map were obtained with different parameters, confirming the validity of the model. Furthermore, the model showed that viscosity is an important parameter separating the completing chattering from the non-completing chattering. The results demonstrated that the model can help solve chattering of impact damper by developing better understanding of the underlying mechanisms.

Analysis for Material of Particle of Particle Impact Damper on Damping Performance of Fixed Fixed Beam

Analysis for Material of Particle of Particle Impact Damper on Damping Performance of Fixed Fixed Beam

Carbon nano fibers reinforced composites origami inspired mechanical metamaterials with passive and active properties

Core panels used for compression or impact damping are designed to dissipate energy and to reduce the transferred force and energy. They are designed to have high strain and deformation with low density. The geometrical configuration of such cores plays a significant role in redistributing the applied forces to dampen the compression and impact energy. Origami structures are renowned for affording large macroscopic deformation which can be employed for force redistribution and energy damping. The material selection for the fabrication of origami structures affects the core capacity to withstand compression and impact loads. Polymers are characterized by their high compression and impact resistance; the drawback of polymers is the low stiffness and elastic moduli compared with metallic materials. This work is focused on the study of the effect of Carbon Nano Fibers (CNF) on the global mechanical properties of the origami panel cores made of polymeric blends. The base matrix materials used were Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) blends, and the percentages of the PLA/TPU were 100/0, 20/80, 65/35, 50/50, 20/80, and 0/100 as a percentage of weight. The weight percentages of CNF added to the polymeric blends were 1%, 3%, and 5%. This paper deals with the fabrication process of the polymeric reinforced blends and the origami cores, in order to predict the best fabrication conditions. The dynamic scanning calorimetry and the dynamic mechanical analyzer were used to test the reinforced blended base material for thermomechanical and viscoelastic properties. The origami core samples were fabricated using per-molded geometrical features and then tested for compression and impact properties. The results of the study were compared with previous published results which showed that there is considerable enhancement in the mechanical properties of the origami cores compared with the pure blended polymeric origami cores. The active properties of the origami unit cell made of composite polymers containing a low percentage of CNF were also investigated in this study, in which the shape memory effect test conducted on the origami unit cell.

Optimization of the impact multi-mass vibration absorbers

The problem of attaching dynamic vibration absorber (DVA) to a discrete multi-degree-of-freedom or continuous structure has been outlined in many papers and monographs. An impact damping system can overcome some limitations by impact as the damping medium and impact mass interaction as the damping mechanism. The paper contemplates the provision of DVA with the several of the impact masses. Such originally designed absorbers reduce vibration selectively in maximum vibration mode without introducing vibration in other modes. An impact damper is a passive control device which takes the form of a freely moving mass, constrained by stops attached to the structure under control, i.e. the primary structure. The damping results from the exchange of momentum during impacts between the mass and the stops as the structure vibrates. The paper contemplates the provision of the impact multi-mass DVA’s with masses collisions for additional damping. For some cases of DVA optimization such a design seems more effective than conventional multi-mass DVA with independent mass moving. A technique is developed to give the optimal DVA’s for the elimination of excessive vibration in harmonic stochastic and impact loaded systems.