scholarly journals Damping Evaluation of Linseed Oil-Based Engineering Elastomers by Vibration Response Method

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Rakesh Das ◽  
Rajesh Kumar ◽  
P. P. Kundu
Keyword(s):  
Free Vibration ◽  
Forced Vibration ◽  
Loss Factor ◽  
Vibration Mode ◽  
Linseed Oil ◽  
Low Cost ◽  
Vibration Damping ◽  
Experimental Setup ◽  
Bending Vibration ◽  
Loss Factors

A low cost experimental setup has been fabricated for evaluation of vibration damping properties of a variety of elastomers developed from linseed oil. Free and forced vibration principles were utilized in this experimental setup. Under forced vibration, the shear loss factor varies from 0.37 to 1.03 at 2nd bending vibration mode and 0.43 to 0.99 at 3rd bending vibration mode for different elastomers. The loss factor varies from 0.52 to 0.94 under free vibration. The loss factors determined by both forced and free vibration techniques are in good agreement with the loss factors obtained from dynamic mechanical analysis. The ultimate tensile strength and Young’s modulus of the elastomers vary from 0.37 to 3.71 MPa and 0.27 to 10.27 MPa, respectively, whereas these properties in compression are in the range of 3.1 to 72.9 MPa and 1.5 to 30.1 MPa, respectively. Thus, these elastomers are mechanically stable for vibration damping applications.

Design of a Directional Olfactory Display to Study the Integration of Vision and Olfaction

2018 ◽  
Author(s):  
Lorenzo Micaroni ◽  
Marina Carulli ◽  
Francesco Ferrise ◽  
Monica Bordegoni ◽  
Alberto Gallace
Keyword(s):  
Virtual Reality ◽  
Low Cost ◽  
Olfactory Cues ◽  
Input Device ◽  
Experimental Setup ◽  
Initial Testing ◽  
Head Mounted Display ◽  
Innovative System ◽  
The One ◽  
Olfactory Display

This research aims to design and develop an innovative system, based on an olfactory display, to be used for investigating the directionality of the sense of olfaction. In particular, the design of an experimental setup to understand and determine to what extent the sense of olfaction is directional and whether there is prevalence of the sense of vision over the one of smell when determining the direction of an odor, is described. The experimental setup is based on low cost Virtual Reality (VR) technologies. In particular, the system is based on a custom directional olfactory display, an Oculus Rift Head Mounted Display (HMD) to deliver both visual and olfactory cues and an input device to register subjects’ answers. The VR environment is developed in Unity3D. The paper describes the design of the olfactory interface as well as its integration with the overall system. Finally the results of the initial testing are reported in the paper.

scholarly journals A Study Regarding the Mechanical Properties of a Hybrid Matrix with Various Volume Proportions of Dammar

2020 ◽  
Vol 57 (1) ◽  
pp. 133-140
Author(s):  
Dumitru Bolcu ◽  
Marius Marinel Stanescu ◽  
Ion Ciuca ◽  
Cosmin Mihai Miritoiu ◽  
Alin Dinita ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Vibration Mode ◽  
Vibration Damping ◽  
The Other ◽  
Damping Properties ◽  
Elongation At Break ◽  
Hybrid Resin ◽  
Natural Resin ◽  
Volume Proportion

This paper studies the influence of the volume proportion between components on the mechanical behaviour of a hybrid resin obtained by combining the natural resin Dammar and epoxy resin. We analyse three sets of hybrid resin samples, in which we used a Dammar volume proportion of 60%, 70%, and 80% respectively and epoxy resin (employed together with its associated reinforcement in order to generate a quick process of polymerization). Following the tensile test we found the characteristic curves, the tensile strength and the elongation at break for each of the three types of resins. We also looked into the vibration damping properties of bars made of this resin. We experimentally determined the frequency and the damping coefficient of the first particular vibration mode for one bar taken out of each set of resins, with one end fixed and the other free. On the basis of the results, we calculated the loss coefficient for each type of resin.

The Lift Force on a Cylinder Vibrating in a Current

1990 ◽  
Vol 112 (4) ◽  
pp. 297-303 ◽  
Author(s):  
G. Moe ◽  
Z.-J. Wu
Keyword(s):  
Free Vibration ◽  
Forced Vibration ◽  
Cross Flow ◽  
Reference Frequency ◽  
Average Force ◽  
Vibrational Response ◽  
Uniform Current ◽  
Extensive Program ◽  
Vibration Tests ◽  
Lock In

This paper reports an extensive program of forced and free vibration tests on a single circular cylinder moving mainly perpendicularly to a uniform current. For both free and forced vibration tests, two cases were investigated: one in which the cylinder was restrained in the in-line direction and the other in which it was supported on suitable springs. The cross-flow vibrational response and hydrodynamic forces on the cylinder were measured. Large variations of motion frequency in the “lock-in” range were found from the free vibration tests. This leads to two different definitions of reduced velocity, namely, a so-called nominal reduced velocity based on one reference frequency and the true reduced velocity based on the actual vibration frequency. When different results are compared, the true reduced velocity should be used. The forced vibration tests showed, as may be expected, that the transverse force in the “lock-in” range on the average will add energy to the cylinder at moderate motion amplitudes and subtract energy at large amplitudes. Some conditions resulting in a steady-state vibration of a flexibly mounted cylinder were analyzed. The actual force traces also show very large and apparently random deviations from the average force amplitude. The results from the forced and the free vibration tests are consistent with each other if the true reduced velocity and reduced amplitude are the same.

Eigensensitivity of Planetary Gear Free Vibration Properties

1999 ◽  
Author(s):  
Jian Lin ◽  
Robert G. Parker
Keyword(s):  
Kinetic Energy ◽  
Free Vibration ◽  
Natural Frequency ◽  
Vibration Mode ◽  
Planetary Gear ◽  
Planetary Gears ◽  
System Parameters ◽  
Frequency Sensitivity ◽  
Vibration Properties ◽  
Inertia Parameters

Abstract The natural frequency and vibration mode sensitivities to system parameters are rigorously investigated for both tuned and mistimed planetary gears. Parameters under consideration include support and mesh stiffnesses, component masses, and moments of inertia. Using the well-defined vibration mode properties of tuned (cyclically symmetric) planetary gears [1], the eigensensitivities are calculated and expressed in simple, exact formulae. These formulae connect natural frequency sensitivity with the modal strain or kinetic energy and provide efficient means to determine the sensitivity to all stiffness and inertia parameters by inspection of the modal energy distribution. While the terminology of planetary gears is used throughout, the results apply for general epicyclic gears.

Large Amplitude Forced Vibration Analysis of Stiffened Plates under Harmonic Excitation

2012 ◽  
pp. 26-61
Author(s):  
Anirban Mitra ◽  
Prasanta Sahoo ◽  
Kashinath Saha
Keyword(s):  
Free Vibration ◽  
Forced Vibration ◽  
Large Amplitude ◽  
Vibration Analysis ◽  
Mathematical Formulation ◽  
Free Vibration Analysis ◽  
Harmonic Excitation ◽  
Stiffened Plates ◽  
Backbone Curve ◽  
Forced Vibration Analysis

Large amplitude forced vibration behaviour of stiffened plates under harmonic excitation is studied numerically incorporating the effect of geometric non-linearity. The forced vibration analysis is carried out in an indirect way in which the dynamic system is assumed to satisfy the force equilibrium condition at peak excitation amplitude. Large amplitude free vibration analysis of the same system is carried out separately to determine the backbone curves. The mathematical formulation is based on energy principles and the set of governing equations for both forced and free vibration problems derived using Hamilton’s principle. Appropriate sets of coordinate functions are formed by following the two dimensional Gram-Schmidt orthogonalization procedure to satisfy the corresponding boundary conditions of the plate. The problem is solved by employing an iterative direct substitution method with an appropriate relaxation technique and when the system becomes computationally stiff, Broyden’s method is used. The results are furnished as frequency response curves along with the backbone curve in the dimensionless amplitude-frequency plane. Three dimensional operational deflection shape (ODS) plots and contour plots are provided in a few cases.

Estimation of coupling loss factors for rectangular plates with different materials and junctions

2019 ◽  
Vol 50 (9-11) ◽  
pp. 306-312
Author(s):  
Mandale Maruti Bhagwan ◽  
Bangarubabu Popuri
Keyword(s):  
Loss Factor ◽  
Energy Analysis ◽  
Acoustic Analysis ◽  
Composite Plates ◽  
Rectangular Plates ◽  
Coupling Loss ◽  
Tightening Torque ◽  
Essential Parameter ◽  
Coupling Loss Factor ◽  
Loss Factors

In statistical energy analysis, coupling loss factor is the essential parameter for vibro-acoustic analysis of complicated structures. The coupling loss factors have been estimated using energy-level difference method. The tightening torque applied at structural junction has been varied. Higher values of coupling loss factor have been observed for higher tightening torque on bolted junction. The coupling loss factors have been determined for various structural junctions of rectangular composite plates. The riveted and bolted junctions have been examined for composite plates in same plane and size. The coupling loss factors for bolted junction are relatively higher than that for riveted junction of composite plates. The values of coupling loss factors are found to increase with increasing tightening torque applied at structural junctions of composite plates. It is also noted that the experimental results of coupling loss factors for point junctions vary with changes in fiber orientations of composite plates. It is firmly believed that the various findings of the coupling loss factors in this article help for vibro-acoustic analysis of complicated structures.

scholarly journals Measurements of Aerosols and Charged Particles On the BEXUS18 Stratospheric Balloon

2019 ◽  
Author(s):  
Erika Brattich ◽  
Encarnación Serrano Castillo ◽  
Fabrizio Giulietti ◽  
Jean-Baptiste Renard ◽  
Sachi N. Tripathi ◽  
...  
Keyword(s):  
Fine Particles ◽  
Low Cost ◽  
Charged Particles ◽  
Negative Ions ◽  
Ground Level ◽  
Experimental Setup ◽  
Vertical Profiles ◽  
Aerosol Model ◽  
Analysis Experiment ◽  
Stratospheric Balloon

Abstract. This paper describes the aerosol measurements setup and results obtained during the BEXUS18 stratospheric balloon within the A5-Unibo (Advanced Atmospheric Aerosol Acquisition and Analysis) experiment performed on October 10th, 2014 in northern Sweden (Kiruna). The experimental setup was designed and developed by the University of Bologna with the aim of collecting and analyzing vertical profiles of atmospheric ions and particles together with atmospheric parameters (temperature, relative humidity and pressure) all along the stratospheric ascent of the BEXUS18 stratospheric balloon. Particles size distributions were measured with the MeteoModem Light Optical Aerosol Counter (LOAC) and air ion density was measured with a set of two commercial and portable ion counters. Though the experimental setup was based upon relatively low-cost and light-weight sensors, vertical profiles of all the parameters up to an altitude of about 27 km were successfully collected. The results obtained are useful for elucidating the relationships between aerosols and charged particles between ground level and the stratosphere with great potential in collecting and adding useful information in this field, also in the stratosphere where such measurements are rare. In particular, the equipment detected coherent vertical profiles for particles and ions, with a particularly strong correlation between negative ions and fine particles, possibly resulting from proposed associations between cosmic rays and ions as previously suggested. In addition, the detection of charged aerosols in the stratosphere is in agreement with the results obtained by a previous flight and with simulations conducted with a stratospheric ion-aerosol model. However, further measurements under stratospheric balloon flights equipped with a similar setup are needed to reach general conclusions on such important issues.

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