The present invention relates generally to environmental stress screening
of fighter aircrafts airborne avionics component and more particularly to fixture
used in vibration testing and method of vibration testing using this fixture. It is an
10 object of the present invention to provide vibration-testing apparatus in which the
amplitude and/or frequency of the IFU of JAGUAR aircraft can be tested. The
present invention employs a simplified but efficient technique and apparatus
design.
15
BACKGROUND OF THE INVENTION
In conjunction with the design and testing of various products, e.g. military
20 products, fighter aircraft, and airborne component , vibration forces are applied to
the product along selected axes thereof to determine if the product can survive
such forces and continue to perform designed function properly. Because it is
typically time consuming and some what difficult to attach and detach an object
to be vibration tested to and from a vibration source, e.g. a shaker table, fixtures
25 have been developed for facilitating the mechanical coupling the work piece with
the vibration source. These fixtures generally comprise a base plate which is
securely attached to the vibration source and one or more mounting surfaces
with work piece holding arrangement to which the work piece to be vibration
tested can be quickly and easily attached.
30 The present invention is particularly concerned with the vibration testing of
IFU of JAGUAR aircraft. The IFU of JAGUAR aircraft are typically exposed to
very severe vibrations during flight operation. These vibrations may have
frequencies in the range 20-2000 Hz.
35
Annexure‐II
SUMMARY OF PRESENT INVENTION
In 5 accordance with one aspect of present invention is to provide a multi
axes vibration fixture that is simple in design and facilitates effective vibration
testing the IFU of JAGUAR aircraft.
In accordance with second aspect of present invention is to provide a
apparatus of the character, aforesaid, wherein the plane of vibration along the
10 major orthogonal may be achieved without complicated mounting and
dismounting of the specimen, and wherein vibration along these axes may be
achieved with the minimum amount of angular measurement to assure such
vibration.
In accordance with yet another aspect of present invention is to provide
15 apparatus wherein vibration along a number of other orthogonal axes may be
achieved with the minimum amount of movement of the specimen and without
the necessity of complicated flange attachments and mounting brackets.
In accordance with yet another aspect of present invention is to provide a
smaller multi axes vibration fixture.
20 In accordance with yet another aspect of present invention is to provide a
rigid multi axes vibration fixture.
In accordance with yet another aspect of present invention is to provide a
multi axes vibration fixture that permits testing of IFU of JAGUAR aircraft with
any arbitrarily selected energy versus frequency profile.
25 In accordance with yet another aspect of present invention is to provide a
multi axes vibration fixture that can be properly and effectively utilized to hold and
firmly fixed the IFU of JAGUAR aircraft by lesser skilled individuals in performing
the vibration test.
In accordance with yet another aspect of present invention is to provide a
30 multi axes vibration fixture that can be properly and effectively fastened to the
shaker table by lesser skilled individuals.
In accordance with yet another aspect of present invention is to provide a
multi axes vibration fixture that can be used to test IFU that does not requires
repeated fastening of IFU to be tested on the vibration fixture.
35 Briefly, the present invention is a straight, vibration fixture for supporting
the IFU of JAGUAR aircraft while the IFU undergoes vibration testing. The
Annexure‐II
vibration fixture includes a base surface and IFU supporting and holding plates,
which is coupled to a shaker table. Thus, energizing the vibration apparatus
causes the vibrating surface to shake along a pre-established vibration axis
which 5 correspondingly shakes the multi-axis vibration fixture.
To reduce as much as possible the weight of the vibration fixture, as much
as possible it’s mounting surface is preferably formed as small as possible to
match, as well as practical, the shape of the IFU being tested, making the
vibration fixture as small and as light as possible while maintaining its rigidity
10 facilitates obtaining more uniform vibration spectrum over a larger frequency
range. The Aluminum Alloy is used for the fabrication of vibration fixture to
achieve the light weight and high rigidity characteristic. These characteristics of
the vibration fixture are also beneficial to employing any arbitrary vibration energy
versus frequency profile.
15 An advantage of the present invention is that during Vibration testing, IFU
receive the same vibration that is applied by the shaker due to the rigidity of
fixture.
BRIEF DESCRIPTION OF THE DRAWINGS
20
The features and advantages of the present invention will become more apparent
and descriptive in the description when considered together with figures/flow
charts presented:
25
Fig. 1 is a Sectional Front view of Vibration Fixture
Fig. 2 is a Top view of Vibration Fixture
Fig. 3 is a Side view of Vibration Fixture
30
DETAILED DESCRIPTION
Referring now to FIGS. 1, 2 & 3, the present invention is a Vibration test
fixture 22 adapted for use with a conventional shaker table 23, e.g., an electro
35 magnetic/electro dynamic vibrator of the type manufactured by Tarang Kinetic (P)
Ltd And identified by model number CHE 040.
Annexure‐II
Vibration fixture 22 is designed to support a test object 24 (IFU) having
mutually-orthogonal X, Y and Z axes (see FIG. 1) in fixed predetermined
relationship with respect to a substantially flat mounting surface on which fixture
22 is supported. As described 5 ibed in greater detail hereinafter the mounting surface
is the top surface 25 of a shaker table 23.
Vibration test fixture 22 comprises a base plate 1 having a substantially
flat top surface ‘A’ and bottom surface ‘B’. Base Plate 1 is made from a material
10 having suitable strength and vibration transfer characteristics, such as Aluminum
alloy plate having a thickness of about 22 mm.
Vibration test fixture 22 comprises holding plate means for securing IFU
24 for the JAGUAR aircraft to Base Plate 1. Such holding plate 5 is having
15 means to hold the IFU in the fixture exactly in same manner as in aircraft in
actual working condition.
As noted above, vibration test fixture 22 is adapted to be attached to either
the mounting surface of a slip table or a shaker table. When it is desired to attach
20 test fixture 22 to the mounting surface 25 of a shaker table 23, fixture 22
comprises a base plate 1 having parallel top and bottom surfaces ‘A’ and ‘B’.
Surfaces ‘A’ and ‘B’ are substantially flat. Base plate 1 is adapted to be attached
to mounting surface 25 of shaker table 23 by conventional means, e.g. by
fastening base plate 1 to mounting surface 25 by mean of conventional
25 fasteners. To enable the conventional means of fastening, twelve counter bore
holes 26 & two holes 27 are fabricated in base plate 1 & vertical angle plate 2 for
clamping on the surface 25 of shaker table 22. When base plate 1 is attached to
mounting surface 25 of shaker table 23, top surface ‘A’ of plate 1 extends in
parallel with mounting surface 25. Vibration test fixture 22 further comprises a
30 vertical member 2 and supporting member 3 & 4 rigidly secured to base plate1
by means of dowel pins and welded structure for creating fixture multi axis to
facilitate the testing of IFU in multi axis.
To use the vibration test apparatus of the present invention, base plate 1
35 is attached to mounting surface 25 of shaker table 23 by conventional means,
e.g. by bolting the plate to the mounting surface. Because vertical angle plate 2
and support blocks 3 & 4 is attached to base plat 1, attaching base plate 1 to
shaker table 23 attaches the entire vibration fixture 22 to the shaker table. As
such, vibration forces generated by shaker table 23 are transmitted via base
40 plate 1, vertical angle plate 2, holding plate 3 & 4 and the support spacer 21 to
the IFU 24 secured to the vibration fixture 22.
Annexure‐II
By supporting IFU 24 in the manner described above with respect to
mounting surface 25 of shaker table 23, vibration testing is simplified because
the IFU 24 does not have to be repositioned 5 in the vibration fixture after vibration
testing along each of three mutually-orthogonal axes of the IFU. After the
vibration testing in one axis vibration fixture is re fastened on the shaker table by
fastening the vertical plate 2 to the mounting surface 25 of shaker table 23. With
known vibration test apparatus, an object is first vibration tested along its X axis,
10 ‘repositioned and vibration tested along its Y axis, and then repositioned again
and vibration tested along its Z axis. Especially where vibration testing is
performed by unskilled personnel or where it is essential that the vibration testing
be performed in as little time as possible, the vibration test apparatus of the
present invention is highly advantageous in as much as the test object does not
15 have to be repositioned for testing along each of its three mutually axes.

WE CLIAMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. We Claim

1. A multi axes vibration test fixture for supporting an object to be vibration tested, said vibration test Fixture being designed for use with a conventional shaker table assembly capable of generating a vibration force which extends along a predetermined vibration axis, said shaker table assembly having a substantially Fiat mounting table surface which extends substantially normally to said vibration axis, said vibration test Fixture comprising: support means, having a substantially Flat surface, for quick release and supporting a test object having mutually orthogonal X, Y and Z axes so that (a) said X, Y and Z axes are in fixed relationship to said support means, and (b) said X and Y axes lie along a plane that extends in parallel with said flat surface; and attachment means for providing a vibration transmissive connection between said substantially Fiat surface and said table surface.
2. The multi-axis vibration fixture of claim 1 wherein, base surface and device mounting surface form respectively a base and upper surface of a multi-axis vibration fixture having a L-shape.
3. The multi-axis vibration fixture of claim 1 wherein the vibrating surface and said base surface are both substantially flat and disposed substantially perpendicular to the vibration axis.
4. The multi-axis vibration fixture of claim 1 further comprising a base plate wherein the vibrating surface is a surface of the base plate.
5. The multi-axis vibration fixture of claim 4 further coupled with the shaker to which said base plate is secured.
6. The multi-axis vibration fixture of claim 1 wherein the multi-axis vibration fixture is monolithic.
7. The multi-axis vibration fixture of claim 1 further comprising a resilient mounting required to mount device to be vibrated on vibrating surface having the same feature as actual working condition on aircraft.
8. A method for vibration testing of IFU by vibrating the device simultaneously along three mutually orthogonal axes comprising the steps of: securing to a vibrating surface, that when energized vibrate along a pre-established vibration axis. A multi axis vibration fixture having a base surface adapted to be juxtaposed with and coupled to the vibrating surface so shaking of the vibrating surface shakes the multi-axis vibration fixture. The multi-axis vibration fixture also having a single plane mounting surface that is the opposite surface of base plate, so shaking of said base surface vibrates IFU being vibration tested. The base surface and the device mounting surface forming respectively a base and upper surface of a multi-axis vibration fixture having an L-shape. Energizing the vibrating surface to shake along the pre established vibration axis vibrates the IFU to be tested for the desired time and frequency. ,TagSPECI:As per Annexure-II