VIBRATION FIXTURE
FIELD OF THE INVENTION
5
The present invention relates to apparatus for vibration testing of test
piece, and more particularly to Fixtures and Jigs used in conjunction with
apparatus for generating a vibration force. It is a signal feature of the invention
10 that faithful transmittal of vibration input to the work piece is obtained on a
consistent basis.
BACKGROUND OF THE INVENTION
15
The reliability of electronic and mechanical assemblies exposed to severe
working environments has been tested by subjecting the assemblies to a
prescribed treatment of vibration. Typically the electronic and/or mechanical
20 assembly or like work piece is secured to a fixture commonly termed a vibration
fixture, which in turn is secured to an electrodynamics shaker to be vibrated in
predetermined directional patterns with predetermined energy inputs. For
accuracy in testing, faithful replication of the input energy to the work piece is
essential, and thus vibration fixtures must be very rigid, lightweight structures to
25 which the work piece can be rigidly bolted.
The present invention is particularly concerned with the vibration testing of
test pieces typically exposed to very severe vibrations during flight operation.
These vibrations may have frequencies in the range 8-2000 Hz.
30
SUMMARY OF PRESENT INVENTION
In accordance with one aspect of present invention is to provide a
35 vibration fixture that facilitates effective vibration testing of test piece.
In accordance with second aspect of present invention is to provide a
smaller vibration Fixture.
Annexure‐II
In accordance with another aspect of present invention is to provide a
lighter vibration Fixture.
In accordance with yet another aspect of present invention is to provide a
5 more rigid vibration Fixture.
In accordance with yet another aspect of present invention is to provide a
vibration Fixture that permits testing a device with any arbitrarily selected energy
versus frequency profile.
In accordance with yet another aspect of present invention is to provide a
10 vibration fixture that can be properly and effectively utilized to hold and firmly
fixed the test piece by lesser skilled individuals in performing the vibration test.
In accordance with yet another aspect of present invention is to provide a
vibration fixture that can be properly and effectively fastened to the shaker table
by lesser skilled individuals.
15 Briefly, the present invention is a straight, Multi-axis vibration fixture for
supporting the test piece while it undergoes vibration testing. The vibration
Fixture includes a base surface that is coupled to a shaker table. Thus,
energizing the vibration apparatus causes the vibrating surface to shake along a
pre-established vibration axis which correspondingly shakes the multi-axis
20 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 test piece like SSFDR being
tested, making the vibration fixture as small and as light as possible while
25 maintaining its rigidity 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. While a vibration fixture in
30 accordance with the present invention for use in performing vibration testing on a
particular product may result in fabrication of fixtures having various different
overall shapes.
An advantage of the present invention is that during Vibration testing, test
piece receive the same relative vibration along each of their three mutually
35 orthogonal axes even, if they are tested at widely different times.
BRIEF DESCRIPTION OF THE DRAWINGS
Annexure‐II
The features and advantages of the present invention will become more apparent
and 5 descriptive in the description when considered together with figures/flow
charts presented:
Fig. 1 is a Front view of Vibration Fixture
Fig. 2 is a Top view of Vibration Fixture
10 Fig. 3 is a Side view of Vibration Fixture
DETAILED DESCRIPTION
15 Referring to FIGS. 1, 2& 3, the present invention is a Vibration test fixture
7 adapted for use with a conventional shaker table 8, e.g., an electro
magnetic/electro dynamic vibrator.
Vibration fixture 7 is designed to support a test object 10 having mutually20
orthogonal X, Y and Z axes (see FIG. 1) in fixed predetermined relationship with
respect to a substantially flat mounting surface on which fixture 7 is supported.
As described in greater detail hereinafter the mounting surface is the top surface
9 of a shaker table 8.
25 Vibration test fixture 7 comprises a base plate 1 having a substantially flat
top surface 11 and bottom surface 12. Base Plate 1 is made from a material
having suitable strength and vibration transfer characteristics, such as Aluminum
alloy plate having a thickness of about 22 mm.
30 Vibration test fixture 7 comprises holding plate means for securing test
piece 10 like SSFDR to Base Plate 1. Such holding plate support means may
comprise, for example, a pair of elongate members named locating pin 6
attached to the holding plate 4 and locating threaded bush 5 fitted to base plate 1
so as to hold the test piece in the fixture exactly in same manner as in actual
35 working condition.
As noted above, vibration test fixture 7 is adapted to be attached to either
the mounting surface of a slip table or a shaker table. When it is desired to attach
test fixture 7 to the mounting surface 9 of a shaker table 8, fixture 7 comprises a
40 base plate 1 having parallel top and bottom surfaces 11 and 12. Surfaces 11 and
Annexure‐II
12 are substantially flat. Base plate 1 is adapted to be attached to mounting
surface 9 of shaker table 8 by conventional means, e.g. by fastening base plate 1
to mounting surface 9 by mean of conventional fasteners. To enable the
conventional means 5 of fastening, fourteen counter sink hole 13 is fabricated in
base plate. When base plate 1 is attached to mounting surface 9 of shaker table
8, top surface 11 of plate 1 extends in parallel with mounting surface 9. Vibration
test fixture 7 further comprises a vertical member 2 and supporting member 3
rigidly secured to base plate1 for creating fixture multi axis to facilitate the testing
10 of test piece in multi axis.
To use the vibration test apparatus of the present invention, base plate 1
is attached to mounting surface 9 of shaker table 8 by conventional means, e.g.
by bolting the plate to the mounting surface. Because vertical plate 2 is attached
15 to support member 2 and base plat 1, attaching base plate 1 to shaker table 8
attaches the entire vibration fixture 7 to the shaker table. As such, vibration
forces generated by shaker table 8 are transmitted via base plate 1, vertical plate
2, locating pin 6 and holding plate 4 and the support means to the test piece 10
secured to the vibration fixture 7.
20
By supporting test piece 10 in the manner described above with respect to
mounting surface 9 of shaker table 8, vibration testing is simplified because the
test piece 10 does not have to be repositioned in the vibration fixture after
vibration testing along each of three mutually-orthogonal axes of the test piece.
25 After the vibration testing in one axis vibration fixture is re fastened on the shaker
table 8 by fastening the vertical plate 2 to the mounting surface 9 of shaker table
8. With known vibration test apparatus, an object is first vibration tested along its
X axis, ‘repositioned and vibration tested along its Y axis, and then repositioned
again and vibration tested along its Z axis. Especially where vibration testing is
30 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
have to be repositioned for testing along each of its three mutually axes.