Mechanical Characterization of a Novel Concept of Adaptive Electrostatic Friction Damper

2020 ◽  
Author(s):  
Oleg Testoni ◽  
Sampada Bodkhe ◽  
Paolo Ermanni ◽  
Andrea Bergamini
Keyword(s):  
Surface Roughness ◽  
Mechanical Test ◽  
Air Gap ◽  
Friction Damper ◽  
Operating Life ◽  
Aerospace Applications ◽  
Resistive Torque ◽  
Novel Concept ◽  
Energy Dissipated ◽  
Static Conditions

Abstract In this work, we present a novel concept of adaptive friction damper based on electrostatic adhesion and we characterize its performance under quasi-static conditions. The concept is based on a stack of circular electrodes structurally coupled to different ends of the damper, separated by a thin dielectric film and hinged around a common axle. When an electric potential is applied, the electrodes experience an attractive force, which is used to control the transfer of shear stress between electrodes and thus the resistive torque of the assembly and the amount of energy dissipated. However, imperfections on the contact surfaces and air gaps have a strong detrimental effect on the resistive torque. A prototype of the damper was manufactured and the resistive torque was measured as a function of applied voltage. Theoretical and experimental results were compared to estimate the average thickness of the air gap. The surface roughness of the electrodes and of the dielectric was measured before and after the mechanical test. Moreover, the surface of an entire electrode was scanned to measure its planarity. Then, the results were compared with the value of the air gap previously estimated. The maximum resistive torque measured was constant over five actuation cycles for constant values of the voltage applied and, as expected, increased quadratically with the voltage. The estimated value of the air gap amounted to 38 μm. Both the electrodes and the dielectric showed an increase in average surface roughness after the mechanical test; however, the surface roughness was lower than 1 μm in both cases and could not justify the estimated air gap. On the other hand, we observed a large inhomogeneity in the planarity of the electrode, which was comparable with the thickness of the air gap previously estimated. The results obtained demonstrated the possibility to adapt the resistive torque of the damper using an electrical input and proved the feasibility of the concept. Further work has to focus on the design of the electrodes and on the operating life of the damper. We envisage that the concept could replace traditional, semi-active dampers in automotive or in aerospace applications.

Tangguh Project: Multidisciplinary and Challenging Design of a Novel Concept of Buckle Initiator

2021 ◽  
Author(s):  
Formentini Federico ◽  
Luigi Foschi ◽  
Filippo Guidi ◽  
Ester Iannucci ◽  
Lorenzo Marchionni ◽  
...  
Keyword(s):  
Soil Liquefaction ◽  
Operating Conditions ◽  
Contributing Factors ◽  
Operating Life ◽  
Foundation Design ◽  
Production Pipeline ◽  
Offshore Pipeline ◽  
Design Loads ◽  
Pipeline Route ◽  
Novel Concept

Abstract This paper is based on the experience made during the design and installation of an offshore pipeline recently completed in Indonesia, where a 24” subsea production pipeline (16km long in 70m water depth) was found susceptible during design to lateral buckling. To limit the development of excessive deformation within the acceptance criteria, a mitigation strategy based on interacting planned buckles has been adopted installing three Buckle Initiators (BI) along the pipeline route. Buckling is a well understood phenomenon. However, this project was characterized by major uncertainties mainly driven by soil characterization, soil-pipe interaction, seabed mobility and soil liquefaction. These uncertainties have played a key role in the in-service buckling design. A lot of engineering efforts have been spent to go through the screening between alternative concepts, the validation of the chosen solution and its detailed engineering phase. This paper discusses the main contributing factors and how the uncertainties have been tackled. The Buckle Initiators are quite large and heavy structures with two main bars: the first ramp has an inclination equal to 30° and the pipeline has been laid on it; a second horizontal ramp was used as sleeper to accommodate the development of the lateral buckle during the operating life. A rotating arm was also used to restrict the pipeline lay corridor on the inclined ramp guaranteeing a combined horizontal and vertical out-of-straightness in the as-laid configuration. The rotating arm has been released as soon as the pipeline passed the BI permitting the pipeline to slide freely over the two BI ramps. The foundation of the Buckle Initiator has a footprint surface of about 60m2 guaranteeing its stability for different soil types characterizing the three installation areas. This more complex solution was preferred with respect to a typical sleeper to increase the robustness of the system in terms of buckle mobilization. The design of the Buckle Initiator was a multidisciplinary activity where many novel concepts were developed and many issues were faced (i.e. pipeline laying on an inclined sleeper, anti-scouring system, foundation design, etc.). The Buckle Initiator design was focused on structural calculations against design loads expected during temporary and operating conditions, geotechnical verifications, installation analysis, pipeline configuration and fatigue assessment. This paper presents all main engineering aspects faced during design and first feedbacks from field after the pipeline installation.

scholarly journals Modelling of a Microslip Friction Damper Subjected to Translation and Rotation

1999 ◽  
Author(s):  
Gabor Csaba
Keyword(s):  
Surface Roughness ◽  
Degrees Of Freedom ◽  
Forced Response ◽  
Least Square ◽  
Contact Model ◽  
Contact Radius ◽  
Algebraic Equations ◽  
Friction Damper ◽  
Six Degrees Of Freedom ◽  
Winkler Elastic Foundation

This paper presents a friction interface model where one of the mating surfaces is curved. The model is based on a discretization of the Winkler elastic foundation model and is general in the sense that it allows for relative motion in all six degrees of freedom. The variables for the contact model are based on damper geometry and material data, except coefficient of friction and tangential stiffness coefficient, which have to be measured. Simulated and experimental hysteresis curves are presented. A model of a curved wedge damper has been developed using the contact model. An algorithm for solving forces and displacement when the damper is allowed to move in all six degrees of freedom has been presented. The governing algebraic equations are solved using a nonlinear least-square method routine in a commercial software package. Forced response of a beam-damper-beam test set-up has been simulated and compared with experiments. The results highlighted some effects which have not been modelled e.g. the actual contact area between damper and blade is influenced by surface roughness for low normal loads. It is assumed that this effect resulted in problems in getting agreement between experiments and analysis. The influence of surface roughness is assumed to be negligible when vibrations of real turbomachinery are considered. This is due to the fact that both normal and excitation force on the clamper are about ten times higher than what was used in the experiments and simulations in this paper. Variation of contact radius of the damper shows that a larger radius e.g. a flatter contact gives better damping and increases the resonance frequency. The disadvantage is that the alignment of the damper becomes more unreliable.

scholarly journals Tailoring Performance, Damping, and Surface Properties of Magnetorheological Elastomers via Particle-Grafting Technology

Polymers ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1411 ◽  
Author(s):  
Martin Cvek ◽  
Miroslav Mrlik ◽  
Jakub Sevcik ◽  
Michal Sedlacik
Keyword(s):  
Molecular Weight ◽  
Surface Roughness ◽  
Surface Properties ◽  
Carbonyl Iron ◽  
Magnetorheological Elastomers ◽  
Molecular Weights ◽  
Magnetorheological Effect ◽  
Novel Concept ◽  
Chain Lengths ◽  
Damping Capability

A novel concept based on advanced particle-grafting technology to tailor performance, damping, and surface properties of the magnetorheological elastomers (MREs) is introduced. In this work, the carbonyl iron (CI) particles grafted with poly(trimethylsilyloxyethyl methacrylate) (PHEMATMS) of two different molecular weights were prepared via surface-initiated atom transfer radical polymerization and the relations between the PHEMATMS chain lengths and the MREs properties were investigated. The results show that the magnetorheological performance and damping capability were remarkably influenced by different interaction between polydimethylsiloxane chains as a matrix and PHEMATMS grafts due to their different length. The MRE containing CI grafted with PHEMATMS of higher molecular weight exhibited a greater plasticizing effect and hence both a higher relative magnetorheological effect and enhanced damping capability were observed. Besides bulk MRE properties, the PHEMATMS modifications influenced also field-induced surface activity of the MRE sheets, which manifested as notable changes in surface roughness.

Effect of Drill Point Angle on Surface Integrity when Drilling Titanium Alloy

2013 ◽  
Vol 845 ◽  
pp. 966-970
Author(s):  
Muhamad Nasir Murad ◽  
Safian Sharif ◽  
E.A. Rahim ◽  
Rival
Keyword(s):  
Surface Roughness ◽  
Surface Integrity ◽  
Surface Microhardness ◽  
Machined Surface ◽  
Safety Requirements ◽  
Subsurface Deformation ◽  
Aerospace Applications ◽  
Average Hardness ◽  
Drill Point ◽  
Deformation Layer

Surface integrity of machined component is of major importance for the reliability and safety requirements during in service especially for the aerospace applications. This paper presents an investigation on the effect of drill geometry on the surface integrity of drilled hole of Ti-6AL-4V during drilling operation. Drilling experiments were conducted under the MQL using a special vegetable oil known as Jatropha oil. Experimental results revealed that drill point angle and coolant-lubricant conditions significantly influence the surface integrity which include surface roughness, micorhardness and microstructure defects. The surface roughness decreased with greater drill point angle. The subsurface deformation layer thickness was approximately 9 - 15 μm from the top of the machined surface. Microhardness profiles of the last hole indicated that the subsurface deformation extend up to a 150 to 200 μm until it reaches to the average hardness.

scholarly journals Impact of Particle Size on Performance of Selective Laser Sintering Walnut Shell/Co-PES Powder

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 448
Author(s):  
Yueqiang Yu ◽  
Minzheng Jiang ◽  
Suling Wang ◽  
Yanling Guo ◽  
Ting Jiang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Particle Size ◽  
Powder Particle ◽  
Mechanical Test ◽  
Selective Laser Sintering ◽  
Particle Diameter ◽  
Laser Sintering ◽  
Walnut Shell ◽  
Powder Particle Size ◽  
Shell Powder

The agricultural and forestry waste walnut shell and copolyester hot-melt adhesives (Co-PES) powder were selected as feedstock. A kind of low-cost, low-power consumption, and environmentally friendly walnut shell/Co-PES powder composites (WSPC) was used for selective laser sintering (SLS). Though analyzing the size and morphology of walnut shell particle (≤550 μm) as well as performing an analysis of surface roughness, density, and mechanical test of WSPC parts with different particle sizes, results showed that the optimal mechanical performance (tensile strength of 2.011 MPa, bending strength of 3.5 MPa, impact strength of 0.718 KJ/m2) as walnut shell powder particle size was 80 to 120 μm. When walnut shell powder particle diameter was 120 to 180 μm, the minimum value of surface roughness of WSPC parts was 15.711 μm and density was approximately the maximum (0.926 g/cm3).

Fatigue Life Enhancement of Titanium Alloy by the Development of Nano/Micron Surface Layer Using Laser Peening

2019 ◽  
Vol 19 (11) ◽  
pp. 7064-7073 ◽  
Author(s):  
S. Sudhagara Rajan ◽  
S. Swaroop ◽  
Geetha Manivasagam ◽  
M. Nageswara Rao
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
High Surface ◽  
Electron Back Scatter Diffraction ◽  
Laser Peening ◽  
Near Surface ◽  
Aerospace Applications ◽  
Beta Alloy ◽  
Stress Maximum ◽  
Bulk Hardness

Ti-15V-3Cr-3Al-3Sn (Ti-15-3) is a metastable beta alloy which is considered to be a potential alternative for Ti-6Al-4V alpha+beta alloy for aerospace applications, especially for sheet products. This paper describes the work carried out to enhance the fatigue life of Ti-15-3 in an economical way by means of laser peening without coating (LPwC) using Nd:YAG laser operating at a power density of 5 GW cm-2. In order to have a sufficient bulk hardness and high compressive stresses on the surface, as-received beta solution treated (ST) Ti-15-3 was subjected to aging (520 °C/10 h/Air-cooled) and then to LPwC. Laser peening induced a notable increase in Ra (arithmetic mean roughness), which was measured using MAHR GD-120 profilometer. The Electron Back Scatter Diffraction (EBSD) analysis of the aged sample (STA) revealed a significant increase in the alpha precipitation (20 vol%), and this led to a substantial increase in the hardness (~40%) and UTS (~50%). In addition to this, peening of aged (STA+LPwC) sample resulted in a considerable increase (~12%) in near-surface microhardness and compressive residual stress (maximum stress of -195 MPa at a depth of 150 μm). This increase in compressive stress and microhardness led to an enhancement in the fatigue life of the STA+LPwC sample by 210% when compared to STA sample. In spite of high surface roughness induced by the LPwC, fractography studies revealed that crack initiation was independent of surface roughness.

A novel concept for adaptive friction damper based on electrostatic adhesion

2020 ◽  
Vol 29 (10) ◽  
pp. 105032
Author(s):  
Oleg Testoni ◽  
Andrea Bergamini ◽  
Sampada Bodkhe ◽  
Paolo Ermanni
Keyword(s):  
Friction Damper ◽  
Novel Concept ◽  
Electrostatic Adhesion

Rapid fabrication of metal-coated composite stereolithography parts

2007 ◽  
Vol 221 (9) ◽  
pp. 1431-1440 ◽  
Author(s):  
Z Zhou ◽  
D Li ◽  
J Zeng ◽  
Z Zhang
Keyword(s):  
Surface Roughness ◽  
Adhesive Strength ◽  
Nickel Coating ◽  
Mechanical Test ◽  
Flexural Modulus ◽  
Test Results ◽  
Fabrication Method ◽  
Rapid Fabrication ◽  
Electrodeposited Nickel ◽  
Strength And Stiffness

In this paper, the rapid fabrication method based on stereolithography (SL) and electrochemical deposition is described in detail and mechanical test results of composite nickel-coated SL parts are presented. Coatings of electrodeposited nickel on SL prototypes result in increases in Young's modulus, UTS, flexural modulus, and strength. Electrodeposited nickel coating has dramatically improved the overall strength and stiffness of SL parts. The adhesive strength of the roughened SL resin-nickel interface is higher than the original. In particular, the influence of the surface roughness on adhesive strength between SL and metal is investigated. Moreover, this paper has presented an application of a structural electrodeposited nickel coating over SL parts to make a functional airfoil model with a complex internal structure and sufficient mechanical strength and stiffness.

Effects of Operating Conditions on Thin Film Deposition Performance in Air Atomizing Spray Pyrolysis

2010 ◽  
Author(s):  
Changxue Xu ◽  
Yong Huang ◽  
Yafu Lin
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Thin Film Deposition ◽  
Air Gap ◽  
Film Deposition ◽  
Operating Conditions ◽  
Air Pressure

Thin films have been finding more and more applications in electronics, optical devices, and energy conversion and storage devices, to name a few. As one of the most promising thin film deposition techniques, air atomizing spray pyrolysis, which uses compressed air to disrupt the liquid stream into droplets, has been favored in scientific and engineering communities. However, the effects of operating conditions such as liquid flow rate, atomizing air pressure, fan air pressure, and air gap on the geometric properties of deposited thin film are still not systematically studied. The objective of this study is to experimentally investigate the effects of air spraying operating conditions on the surface roughness and thickness of deposited zinc oxide (ZnO) thin film. It is found 1) The surface roughness increases with the liquid flow rate, but decreases with the atomizing air pressure, fan air pressure, and air gap; 2) The surface roughness decreases along both the X and Y directions under any given operating condition; 3) The thickness increases with the liquid flow rate and the atomizing air pressure, but decreases with the fan air pressure and the air gap; and 4) The thickness generally changes differently along the X and Y directions. Along the X direction, it decreases monotonically; however, along the Y direction, it increases first then decreases as in a saddle shape. While ZnO film deposition is studied, it is expected that the above conclusions may be applicable in air spraying other materials.

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