Experimental Determination of the Complete Dynamical Properties of a Two-Degree-Of-Freedom Model Having Nearly Coincident Natural Frequencies

1967 ◽  
Vol 9 (5) ◽  
pp. 402-413 ◽  
Author(s):  
R. W. Traill-Nash ◽  
G. Long ◽  
C. M. Bailey
Keyword(s):  
Experimental Investigation ◽  
Experimental Determination ◽  
Natural Frequencies ◽  
Degree Of Freedom ◽  
Influence Coefficients ◽  
Stiffness Properties ◽  
Modes Of Vibration ◽  
Dynamical Properties ◽  
Two Degree Of Freedom

Existing techniques of resonance testing have shown a marked inability to find the principal modes, natural frequencies and levels of damping in a structure which possesses two or more close natural frequencies (1)§. This paper describes an experimental investigation on a two-degree-of-freedom model of a technique which makes use of dynamical influence coefficients (or receptances) measured at a number of stations on the structure (2) (3) (4) (5). The measured coefficients are used to calculate natural frequencies and modes of vibration, and the mass, damping and stiffness properties of the system. Several model configurations having different natural frequency separations were tested and no special difficulty resulted when natural frequencies were close or even coincident.

The mechanics of vibrating flames in tubes

1977 ◽  
Vol 353 (1675) ◽  
pp. 459-473 ◽  
Keyword(s):  
Experimental Determination ◽  
Wave Motion ◽  
Pressure Oscillations ◽  
Acoustic Modes ◽  
Closed Tube ◽  
Modes Of Vibration ◽  
Dynamical Properties ◽  
Narrow Section ◽  
Derivatives Of

A mechanism of flame vibration is proposed which depends upon the instability of a reacting gas with respect to wave motion. A flame, steadily advancing down a tube, is represented by a narrow section of reacting gas bounded on either side by non-reacting gases at appropriate temperatures. By matching the derivatives of the velocity potentials of the reacting gas and the non-reacting gases at the two interfaces the dynamical properties of the flame are investigated. Relative values of the intensities of the possible acoustic modes, as well as their frequencies, are calculated and are shown to be in general agreement with observations. The pressure oscillations at the end of a closed tube in the unburnt gases are investigated and it is shown how such measurements can provide an experimental determination of the rate of growth of the amplitudes of the permissible modes of vibration.

Determination of the first n modes of a tall building from a reduced eigenvalue problem

1964 ◽  
Vol 54 (4) ◽  
pp. 1233-1254
Author(s):  
Moshe F. Rubinstein
Keyword(s):  
Eigenvalue Problem ◽  
Natural Frequencies ◽  
Tall Building ◽  
Degree Of Freedom ◽  
Mode Shapes ◽  
Story Building

Abstract The first n natural frequencies and mode shapes of an N degree of freedom structure (n < N) are derived from the solution of a reduced eigenvalue problem of order smaller than N. The reduced eigenvalue problem is formulated by using experience to select approximations to the first n modes desired. Accuracy is improved when more than n modes are selected. The method is illustrated by a study on an 18 story building.

The Use of Rubber in Vibration Isolation: Including the Case of Six Degree of Freedom Systems

1937 ◽  
Vol 4 (3) ◽  
pp. A109-A114
Author(s):  
E. H. Hull
Keyword(s):  
Elastic Properties ◽  
Elastic Material ◽  
Vibration Isolation ◽  
Natural Frequencies ◽  
Degree Of Freedom ◽  
Modes Of Vibration ◽  
Six Degree Of Freedom

Abstract The desirable properties of an elastic material applicable to many types of vibration-isolation problems are outlined. Of those materials at present available, rubber appears most suitable for this type of work. The general elastic properties of rubber are discussed and data given for determining the stiffness of pads made from one particular compound. Equations are developed for the six natural frequencies and associated modes of vibration of a mass supported on elastic pads and examples of vibration isolation worked out using this theory.

Shrinkage of Fine-Grained Composites Based on Alkali-Activated Slag

2018 ◽  
Vol 761 ◽  
pp. 7-10 ◽  
Author(s):  
Barbara Kucharczyková ◽  
Vlastimil Bílek Jr. ◽  
Dalibor Kocáb ◽  
Ondřej Karel
Keyword(s):  
Experimental Investigation ◽  
Experimental Determination ◽  
Alkali Activated Slag ◽  
Fine Grained ◽  
Shrinkage Reducing Admixture ◽  
Activated Slag ◽  
Alkali Activated

The paper deals with the experimental determination of shrinkage development of the composites based on the alkali-activated slag (AAS). The main aim of the experimental investigation was to verify the effect of the addition of shrinkage-reducing admixture (SRA) on the overall process of shrinkage properties during AAS composites ageing.

Technical Note: A two-degree-of-freedom ambulance stretcher suspension: Part 3: Laboratory and road test performance

1998 ◽  
Vol 212 (5) ◽  
pp. 401-407 ◽  
Author(s):  
R. J. Henderson ◽  
J. K. Raine
Keyword(s):  
Test Performance ◽  
Natural Frequencies ◽  
Low Cost ◽  
Mechanical Systems ◽  
Technical Note ◽  
Suspension System ◽  
Degree Of Freedom ◽  
Road Test ◽  
Pneumatic Suspension ◽  
Two Degree Of Freedom

Parts 1 and 2 of this paper gave a design overview and described the dynamics of a prototype two-degree-of-freedom pneumatic suspension for an ambulance stretcher. This concluding part briefly reviews laboratory shaker table and ambulance road test performance of the suspension with passive pneumatic damping. The suspension system is found to offer compact low-cost isolation with lower natural frequencies than achieved in earlier mechanical systems.

Free Vibration of Continuous Skin-Stringer Panels

1960 ◽  
Vol 27 (4) ◽  
pp. 669-676 ◽  
Author(s):  
Y. K. Lin
Keyword(s):  
Free Vibration ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Normal Modes ◽  
Time Dependent ◽  
Experimental Measurements ◽  
Structural Configuration ◽  
Modes Of Vibration ◽  
Fuselage Skin

The determination of the natural frequencies and normal modes of vibration for continuous panels, representing more or less typical fuselage skin-panel construction for modern airplanes, is discussed in this paper. The time-dependent boundary conditions at the supporting stringers are considered. A numerical example is presented, and analytical results for a particular structural configuration agree favorably with available experimental measurements.

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