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The Experiences of Esterline Advanced Sensors using SAMCEF® in the development of Aeronautic Sensors
Paul CARRICO , Designer /Materials Expert Esterline Advanced Sensors – AUXITROL SA – Bourges (France)
Abstract : This presentation comprises 3 main discussion topics :
o A quick overview of FEA’s performance over the past few years using the SAMCEF® module for sensors development (THERMAL®, MECANO®, DYNAM®, REPDYN®, SPECTRAL®)
o The ability of SAMCEF® to interface with external routines for increased reliability i.e. leading to a good correlation of the modelling to the test measurements : a specific development including an hyperelastic material is presented for model analysis (modal analysis and dynamic response)
o A few examples which highlight gains in efficiency (the ability to launch multiple runs, automatic post-processing …)
1- Quick insight to Esterline Advanced Sensors
Esterline Advanced Sensors offers ours customers a broad range of high precision
solutions for aeronautics (cockpit, airframe and engine) and derivative products for
marine, defence and the industrial sector. It is based on a strong company culture,
shown by our 936 employees, who are driven by high added-value customer service,
reliability and the best operational performance of our products. The company asserts its
leadership in the field of sensors for pressure, temperature, speed, torque and analogue
indicators.
The ability to master programs - from design to development and through industrial to
production - and to work with partners in different fields of application makes Esterline
Advanced Sensors a tier one supplier.
Each new product incorporates our world class pedigree, but is unique and application
specific in line with customer requirements. Examples of our sensors and harnesses are
shown in Fig 1.
Fig 1 : Engine and aircraft views featuring some Esterline Advanced Sensors products (The Engine depicted above is a Rolls Royce Trent and has been used for illustrative purposes only. Esterline Advanced Sensors is
only one of many suppliers to this power unit and therefore it is used here for the ease of understanding sensor applications and
part locations)
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
2- Introduction
Finite Elements Analyses (FEA) correlated with physical testing, is a key step in
certifying new Sensor designs. This work allows Esterline to determine many aspects
of a design, including the safety margin, a fundamental part of the design validation
process.
Furthermore FEA’s are crucial towards extrapolating the mechanical behaviour of our
sensors in extreme conditions where physical tests are unrealistic, such as very low
temperatures (typically in cryogenic conditions), very high temperatures and high
frequency environments.
In our Temperature Design Office in Bourges (France), Esterline Advanced Sensors
uses a number of packages including SAMCEF®
for mechanical and thermal modelling
(in vibration conditions or in non-linear geometrical/material conditions) and
HYPERMESH®
(from Altair for meshing the parts). Following some years of using
SAMCEF®
, we are satisfied that it provides a good correlation between our test
measurements and provides a robust and high performance from the different
modules we use.
The current article is organised around three major experiences:
1- A brief presentation of recent Esterline Advanced Sensors’ developments
making intensive use of SAMCEF®
packages (an example per module is
presented)
2- How the high capacity of SAMCEF®
packages can be interfaced with external
tools throughout the modelling of a sensor, including a hyperelastic material
(through BACON® and SAMRES®
- modal analysis and dynamic response),
3- Finally, additional examples (some anecdotal) will be discussed : a way to
manage and launch multiple runs and to “automatically” plot, resize and crop
pictures in a post-processing stage.
3- Examples of Esterline Advanced Sensor modelling, performed using the SAMCEF ® package
3-1 Thermal modelling on an engine structural ring (THERMAL® module) Our objective was to determine the maximum temperature of the stud soldering of
the engine features (in terms of specific mass flows W, static temperatures Ts and
static pressure Ps of internal flow and secondary one).
After calculating “by hand” the forced convective heat exchange coefficients h
(D
Nuh
extint/
⋅= λ where the Nusselt number ( )PrRe,fNu = depends on Prandtl number
Pr and Reynolds one Re) inside and outside the ring as Boundary Conditions BC’s,
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
the Finite Element Analysis is performed in non-linear steady state condition (see
Fig 2-b and Fig 3).
Note no radiation has been taken into account in the current FEA.
(a) (b)
Fig 2 : Mesh (a) and thermal field (b)
(a) (b)
Fig 3 : Thermal field (zoom on the studs) and nodal values (cross section)
3-2 Thermo-mechanical modelling on sensor (THERMAL® and MECANO® modules) Our aim here was to validate the strength of the flange under fire conditions
(sensor on a hydraulic duct). The analysis includes the fire test conditions for the
thermal loading (flux, fluid temperature and heat exchanges) as well as the fluid
pressure and the tightening for the mechanical loading.
In addition to material non-linearity, contact conditions were implemented (.MDS
command) between the flange and a rigid plane (that simulates the wall duct) as
well as between the flange and the screws (.MCT command). The tightening at
room temperature was validated through an initial static computation using .MNT
command (plus .MCE + FRE1 command and .SUB + IREF 1 one).
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
(a) (b)
(c) (d)
Fig 4 : Mesh in BACON® (a), contact conditions (b) and thermal mapping (c-d)
The Safety Factor SF (SF = σequivalent / σUTS where σequivalent is the equivalent stress
in Von Mises meaning) is calculated in MECANO®
through XC keyword in the
.MAT command (see Fig 5-b). In addition we can note the tightening lost (minus
60 % between room temperature & max. temperature) due to the difference of
material expansion between the screws and the flange (i.e. difference of C.T.E).
(a) (b)
Fig 5 : Safety margin calculation (a) and tightening lost (b)
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
(a) (b)
(c) (d)
Fig 6 : Displacements due to thermal expansion (a to c) and plastic strain of
the flange (d)
3-3 Dynamic non-linear calculation (MECANO® module) At the very early stage of the development our Customer asked us to estimate the
force on four screws of an inlet sensor following a bird impact (see Fig 7). This
initial study required an elastic-plastic calculation to be performed (without
considering any strain rate effect).
The loading was considered as a Pressure applied onto the intrusive part in
transitory conditions ( VCP x2
21 ρ= - see Fig 8-a). The resulting forces in the 4
screws are plotted in Fig 8-b.
Contact conditions were implemented (.MDS and .MCT commands).
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
(a) (b)
(c) (d)
Fig 7 : Mesh (a-b) and Rigid surfaces (c) and Impact surface (d)
The forces are plotted thanks to .MNT command (see Fig 8-b).
(a) (b)
Fig 8 : Transitory scheme and resulting efforts in the 4 screws (.MNT command)
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
3-4 Modal analysis and Dynamic response (DYNAM® and REPDYN® modules) Modal analysis and dynamic response analyses are often performed to determine
the maximum stress, and subsequently, to calculate the Safety factor (from the
material fatigue strength or from the Goodman diagram).
The section 4 presents a more detailed example of modal analysis and dynamic
response.
3-5 Random vibrations on a pre-loaded sensor (ASEF® and DYNAM® / SPECTRAL® modules) Here follows an example of a sensor placed in cryogenic ducts (Hydrogen and
Oxygen liquids) and worked under high (random) vibration spectrum (see Fig 9) for
a short duration (600 seconds). The analysis was performed in two steps : a pre-
loading with ASEF®
(a mapping of the pressure drag) and random calculations with
DYNAM®
/ SPECTRAL®
(see Fig 10).
The results provide either σRMS and δRMS (where σ is the stress and δ the
displacement) or σpeak and δpeak for PSD’s applied in the 3 directions at the same
time (see Fig 10).
(a) (b)
(c) (d)
Fig 9 : Mesh (a), Pressure profile following the azimuth (b-c) and vibration
spectrum (PSD –d)
VCPP p2)(
2
1)( ∞∞ ⋅⋅+= θρθ
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(a) (b)
Fig 10 : RMS Stress field with σRMS << σPeak (a) and RMS
displacements (b)
4- Interfacing of SAMCEF ® with Esterline Advanced Sensors’ external routines/modules
In addition to its robustness and its reliability, SAMCEF®
proved relatively easy to
interface with external routines. And, to illustrate this, below is a good example!
In this study, the sensor was suspended through an elastomeric damper i.e. hyperelastic
material (see blue sub-part in the Fig 12). The material is highly non-linear : indeed, its
stiffness depends on both the mass of the sensor and on the vibration spectrum (i.e.
mechanical loading). Fig 11 illustrates this particular behaviour well : Fig 11-a shows
that the transmissibility changes with the vibration spectrum as well as the natural
frequency and Fig 11-b shows resonance decreases of more than 40%, between 1g peak
input and 40g peak.
(a) (b)
Fig 11 : Test measurement : transmissibility’s in one direction (a) and
normalized resonance change
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
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With 3 million D.O.F (Degree Of Freedom), the direct integration to take into account
the non-linearities (both material non-linearity and contact BC’s) is not possible. So, in
order to use the modal superposition method, our solution was to replace the elastomeric
material by springs (BUSH elements) with a different stiffness and a different damping
value in each direction (KTx ≠ KTy ≠ KTz and CTx ≠ CTy ≠ CTz where KT represent the
stiffness and CT the damping value).
Specific vibration tests were performed in order to isolate the specific behaviour of the
damper in vibration conditions i.e. to avoid any specific mode of the intrusive part (see
Fig 12-c – the mock-up has the same weight and the same centre of gravity CG) ; the
tests were modelled to fit the spring parameters (Fig 12-d and Fig 13). For that purpose
SAMCEF®
was interfaced with SCILAB [2] to manage the optimization process (non-
linear NELDER-MEAD simplex algorithm) as well as the recording of the intermediate
results coming from BACONPOST®
/FAC®
and SAMRES®
and the updates of the input
.dat files (see Fig 15 and Fig 16).
(a) (b)
(c) (d)
Fig 12 : Mesh of the complete sensor (a-b) and damper characterization
mock-up (c-d)
Based on the test measurement analysis, a strategy has been adopted to reduce the
number of variables from 14,000 to 12 depending on the node localization (see Fig 14):
1- The cost function has been defined as the Sum of the Square Errors (SSE)
between the resonance calculated by DYNAM®
and the measured ones to fit the
BUSH stiffness (see Eq. 1),
2- In the same manner the cost function is defined as the SSE of the displacements
for the fitting of BUSH damping values in REPDYN®
module (see Eq. 2).
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
( )∑
−⋅==
n
isfrequencie
F
FFWSSE
measured
measuredFEA ii
1
2
_0
_0_0
(Eq. 1)
Where
○ Wi is the Weight of the ith natural frequency
○ F0_FEA is the ith resonance calculated by
DYNAM®
○ F0_measured is the ith test measurement on the
shaker
○ n is the number of natural frequencies
( )∑
−⋅==
n
intsdisplaceme
measured
measuredFEA iiWSSE
1
2
δδδ
(Eq. 2)
Where
○ δFEA is the ith displacement calculated by
REPDYN®
○ δmeasured is the measured displacement of the
ith mode
The damper is replaced by BUSH elements with one end connected to the flange, and
the other end linked to the shaker node with the .LIA command (see Fig 13).
(a) (b)
(c) (d)
Fig 13 : Damper modelled with springs
(a) (b)
Fig 14 : Fitting parameters strategy depending on nodes localization
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Fig 15 : Algorithm for fitting parameters (each update is performed thanks to Scilab)
* Case study No : X
* Gamma : 1 G
* Iteration No : X
* KG_X = 9.45225
* KG_Y = 6.98881
* KG_Z = 22.0209
* KS_X = 17.5172
* KS_Y = 54.706
* KS_Z = 17.1971
* CG_X = 0.000226055
* CG_Y = 0.000869445
* CG_Z = 0.00264304
* CS_X = 0.00113199
* CS_Y = 0.00138422
* CS_Z = 0.000223629
* Bacon 0 in progress .....
* Bacon 0 ended .....
* Dynam in progress .....
* Dynam ended .....
* The FEA is launched following the 3 axis !
* axis 1
* Repdyn 1 in progress .....
* Repdyn 1 ended .....
* Baconpost 1 in progress .....
* Baconpost 1 ended .....
* Samres 1 in progress .....
* Samres 1 ended .....
* axis 2
* Bacon 2 in progress .....
* Bacon 2 ended .....
* Repdyn 2 in progress .....
* Repdyn 2 ended .....
* Baconpost 2 in progress .....
* Baconpost 2 ended .....
* Samres 2 in progress .....
* Samres 2 ended .....
* axis 3
* Bacon 3 in progress .....
* Bacon 3 ended .....
* Repdyn 3 in progress .....
* Repdyn 3 ended .....
* Baconpost 3 in progress .....
* Baconpost 3 ended .....
* Samres 3 in progress .....
* Samres 3 ended .....
* Samcef displacements :
1. 0.0011229
2. 0.0005520
3. 0.0008592
* Measured displacements for 1 G:
1. 0.00112
2. 0.00054
3. 0.00086
* SSE = 6.66996e-005
Fig 16 : Example of a loop for fitting damping values on the displacements in REPDYN®
- Each file / update / run is managed with algorithms written in Scilab
(note the stiffness were initially fitted)
DYNAM® : stiffness’s � natural
frequencies + modes fitting
REPDYN® damping values =
displacements peak
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
(a) (b)
From 35G the changes have significant sliding
origin
(c)
Fig 17 : Parameter changes with the vibration spectrum (a-b)
The two tables below show that the Finite Elements Analyses correlate well with the
practical test results (see Table 1 and Table 2) : after performing the vibration test we
analysed the initial results (by adding further instrumentation we could record the
thermal increases due to the friction at the damper/flange interface) � the curves
inflection describes the conditions where the sliding become significant (see Fig 17-c).
Vibration Spectrum [g peak]
Mode 1g 5g 10g 15g 20g 25g 30g 35g 40g
1 0.08% -0.01% -0.11% 0.02% -0.24% 0.02% 0.08% -0.12% 0.17%
2 0.03% -0.04% -0.14% 0.02% -0.01% -0.17% 0.18% 0.15% 0.11%
3 -0.08% -0.11% -0.04% -0.10% -0.03% 0.03% 0.02% 0.01% 0.02%
Table 1 : Comparison of resonances between FEA analysis and actual measurements
Vibration Spectrum [g peak]
Mode 1g 5g 10g 15g 20g 25g 30g 35g 40g
1 0.24% -0.15% 0.05% -0.23% -0.14% 0.27% -0.87% -0.72% -0.56%
2 2.43% -0.77% 0.31% 0.53% 2.54% -1.31% 3.15% 1.67% 0.41%
3 0.05% -0.24% -0.04% -0.67% -0.47% 0.44% -0.50% 0.30% -0.73%
Table 2 : Comparison of displacements between FEA analysis and actual measurements
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may not be copied or used for any purpose other than that for which it is issued, without the written authority of Weston Aerospace Limited or Auxitrol SA or Norwich Aero.
The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
From the test vibration (i.e. in an inverse method) and based on the customer vibration
spectrum (see Fig 18), the stress mapping is calculated re-using the fitted parameters:
- Between input γ the parameters are linear interpolated,
- A complete run (DYNAM®
+ REPDYN®
) is needed per input γ
and natural frequency
The previous FEA’s are driven with Scilab.
Fig 18 : Example of vibration spectrum provided by a customer
The picture hereafter (see Fig 19) presents an example of the resulting modal analysis
(DYNAM®
) for an input γ coming from test results analysis.
(a) (b)
(c) (d)
Fig 19 : Example of modal analysis performed after fitting parameters
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The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
5- Miscellaneous 5-1 Multiple runs in batch mode
In the same manner as the previous example, it is possible to plan multiple runs, in
batch mode, from a Scilab file.
5-2 “Automatic” picture post-processing The pictures are generated from a script into BACON
®/ BACONPOST
® (.PLOT
command). Commonly dozens of pictures may be generated in a complex
modelling mode to present shapes, displacements, stress fields and so on. The
previous pictures can be easily resized, cropped and so on (using ImageMagick
libraries [2]) so that they’ll be included in a report, technical note or any other
document.
This is currently done in two steps. Firstly, a grid is superimposed onto the picture
giving the parameters (cropping) and, in a second step, the picture is cropped and
eventually resized (see Fig 20).
Fig 20 : Example of picture “automatic” cropping
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The information contained within this document is subject to patents and possible patent applications and is considered proprietary of Weston Aerospace Limited or Auxitrol SA or Norwich Aero
6- Conclusion
SAMCEF codes are routinely used at Esterline Advanced Sensors to help reinforce the
quality of our products, with FEA’s performed at both the development and
qualification stages.
The initial work is undertaken to validate the strength of our sensors, followed by a
second phase to determine the safety margin or to explore conditions where physical
tests cannot be performed e.g. cryogenic conditions, very high frequencies, high
spectrum and low frequency (such as the fan blade off condition).
After some years of intensive use of the SAMCEF package, Esterline Advanced Sensors
has no reservations about the robustness, reliability and efficiency of this solution.
7- References
[1] Scilab webpage : http://www.scilab.org/
[2] ImageMagick webpage : http://www.imagemagick.org/script/index.php
Author Reference : paul.carrico “at” esterline.com
8- Thanks
Thanks to James Ewing (V-P Engineering and New Technologies – Esterline Advanced
Sensors) for his input and support.