Field of the lnve'ntion
The invention relates to mechanical engineering field and specifically to
testing of gas turbine engine parts.
Background of the Invention
The current fatigue testing for aero engine accessory shaft is carried out
by testing the specimen in the fatigue testing apparatus. Simple specimen
shapes and actual components have compared for fatigue life and
noticeable difference in fatigue life is observed between them. The
specimen testing is limited by the type of loading it can endure during the
testing is. torsion, push-pull or rotating bending. The excitation from
driving gears cannot be included in the specimen testing. Further, the
weight of the overhanging components supported on the shaft cannot be a
part of the specimen testing.
These problems are addressed by introducing a real component fatigue
test rig for aero engine accessory shaft at engine operating conditions.
3.1 Prior Art
US101126201 BZ discusses the fatigue testing of a specimen. The
invention pertains to a combination of a test rig and test specimen for
performing a fatigue test‘ US 6732591 82 discusses a device for fatigue
testing of materials. A device for fatigue testing of materials comprises a
frame, first and second clamping means for holding a specimen to be
tested. The above patents discuss the testing at the specimen level and
identifying the real structure'behavior from the specimen test data.
Direct comparison between simple specimen shapes and real structure
have revealed marked difference in fatigue life. Hence a fatigue test rig has to be developed for carrying out the fatigue test of actual component
at the operating conditions.
4 Brief Summary of the Invention
The fatigue test rig introduced, comprises of the following features:
The test rig comprises a DC motor [010] driving a step-up gear box [030]
through a low speed coupling [020] and a high speed coupling [040] which
is coupled to the gear box shaft [050]. The high speed coupling [0401‘ is
attached to a driving gear [050] which in turn drives the testing shaft [060].
The shaft [060] drives the blower wheel [080] which draws air [100]
through the casing [070] mounted heat exchanger [090] to cool the engine
oil to the desired level allowing continuous operation for long hours and the air exits [110] through the opening in the casing [070].
The test rig has capability to include effect of the weight of the
overhanging components supported on the accessory shaft [060] Le. the
blower wheel [080], heat exchanger [090] and the casing [070]. The
excitation from driving gear [050] can also be included as a part of the
fatigue testing in the present rig.
5 Detail Description of the Drawings
The invention can be better understood by reading the detail description of
the disclosed embodiment followed by the accompanied drawings in
which,
Figure 1: depicts the schematic of the test rig where DC motor [010], low
speed coupling [020], step-up gear box [030], high speed coupling [040],
driving gear [050], test component [060], blower wheel [080], heat
exchanger [090] and the casing [070] are shown.
Figure 2: details of the arrangement where blower wheel [O80] draws air
[100] through the casing [070] mounted heat exchanger [090] to cool the engine oil to the desired level. The air exits [110] through the opening in
the casing [070].
Figure 3: shows the driving gear [050] and the test component [060] in
detail.
Figure 4: shows the constructional details of the high speed coupling
[040}
Figure 5: explain the provision for adapting the test rig for different driving
gear [050} and test component [060] combinations by having a detachable
gear [052].
6 Detail Description of the Invention
The following specification particularly describes the invention and the
manner in which it is to be performed.
Referring to Figure 1, the test rig comprises a DC motor [010] driving a
step-up gear box [030] through a low speed coupling [020] and a high
speed coupling [040] is attached to the gear box shaft. The other end of
the high speed coupling [040] is attached to a driving gear [050] which in
turn drives the testing shaft [060].
Referring to Figure 2, the shaft drives the blower wheel [080] which draws
air [100] through the casing [070] mounted heat exchanger [090] to cool
the engine oil to the desired level allowing continuous operation for long
hours. The air goes out [110] through the opening in the casing [070].
Referring to Figure 3, the fatigue load is generated by the excitation from
the driving gear [050] used to drive the accessory shaft [060].
Referring to Figure 4, the high speed coupling [040] is given provision for
installation of variable diameter sizes to carry out testing of different
shafts. It has a flexible member [041] connecting an inner shaft [043] to an
intermediate shaft [042] and a similar flexible member [041] connecting an intermediate shaft [042] to the detachable outer shaft [044] which will be
modified to suit different shaft driving gears.
Referring to Figure 5, provisions are provided to use different driving
gears [050] to identify the effect of excitation of driving gear on the fatigue
5 life of the testing shaft [060]. The driving gear haé detachable gear [52]
assembled to the shaft [051] to permit changing the same to find out the
effect on fatigue life‘
Thus this test rig is a comprehensive fatigue testing arrangement for
engine accessory shaft [060] with the capability to carry out the fatigue
10 testing by including the overhanging blower wheel [080], heat exchange(
[090] and the casing [070] as well as the excitation force generated by the driving gear [050].
Structural analysis has been carried out for the test rig to assess structural
integrity during torque application. Subsequently, detailed drawings of the
15 components have been released. The accuracy of the results has
improved compared to the existing specimen fatigue testing methods by
the introduction of the present rig.
We Claim,
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