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Shock and Vibration in Rail and other Transport Modes
William C. Shust
2007OBJECTIVE ENGINEERS, INC.
Acknowledgements
z AAR / TTCIz ASF-Keystone, Union Pacificz FRAz Chicago Transit Authorityz Norfolk Southernz Monsanto Companyz International Truck & Engine
2007OBJECTIVE ENGINEERS, INC.
No, No, No
That regular rock.
Me need Phillips.
Bills
2007OBJECTIVE ENGINEERS, INC.
Broad overview of shock & vibration issues in railroading
z Vibration issues z Typical mechanical shocksz Various industry test standardsz Mitigation techniquesz Brief comparison of other transport modes to
the rail shipping environment.
z Technical conclusionsz Future trends for S&V in railroading
2007OBJECTIVE ENGINEERS, INC.
SHOCK & VIBRATION ISSUES
Overall car stability Component strength Human comfort Cargo damage
2007OBJECTIVE ENGINEERS, INC.
A closer look at the railcar environment: dynamic excitations
VehicleVehicle
Bogie and Unsprung Mass
Bogie and Unsprung Mass
Irregular running surfaces of wheel and rail[Wheelflats, out-of-round wheels, wheel corrugation,
rail corrugation, dipped welds and joints, shelling, etc]
Irregular running surfaces of wheel and rail[Wheelflats, out-of-round wheels, wheel corrugation,
rail corrugation, dipped welds and joints, shelling, etc]
Track components[Rail bending, railpads, tie bending,
ballast and subgrade]
Track components[Rail bending, railpads, tie bending,
ballast and subgrade]
Wheel/rail noise[Rolling and impact noises from irregularities on
wheel and rail, and squeal from stick-slip vibration]
Wheel/rail noise[Rolling and impact noises from irregularities on
wheel and rail, and squeal from stick-slip vibration]
0 - 20 Hz0 - 20 Hz
0- 500 Hz0- 500 Hz
0 - 1500 Hz0 - 1500 Hz
0 - 1500 Hz0 - 1500 Hz
0 - 5000 Hz0 - 5000 Hz
2007OBJECTIVE ENGINEERS, INC.
At the low frequency end: rigid carbody motions
z Pitch & bounce, yaw & sway, twist & roll, lateral hunting all under 4 Hz
2007OBJECTIVE ENGINEERS, INC.
60 Wavelength
Right RailVerticalPosition
Left RailVerticalPosition
0.75 Amplitude
Roll Input for AAR Chapter XI spec.(Left and right track vertical profiles)
2007OBJECTIVE ENGINEERS, INC.
0
1
2
3
4
5
0 20 40 60 80Simulated operating speed (mph) over repeated 3/4-inch twist and
roll perturbations
M
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60ft D.C.32ft Flatcar
0.6 Hz resonance -- Carbody roll(constant amplitude cross-level deviations)
2007OBJECTIVE ENGINEERS, INC.
Typical Twist & Roll resonance (generic tank car, 18 mph, 39 cusps)
2007OBJECTIVE ENGINEERS, INC.
More low freq. behavior ~ 2 Hz Wheelset Lateral Hunting
2007OBJECTIVE ENGINEERS, INC.
At the high frequency end -- potential fatigue of & on circuit boards
Small mechanical fittings on a high frequency source (100-200 Hz)
PC Board bending (70-150 Hz)
Tiny cantilevered components (up to 1500 Hz if small enough)
2007OBJECTIVE ENGINEERS, INC.
A few peculiarities related to certain car types
z Covered hoppers high CG, car rock-offz Tank Cars tors. stiff, track twist sensitivez Conversion of 89 flats to early car haulersz Heavy duty span bolster cars (8+ axles)z Lighter weight coal cars
2007OBJECTIVE ENGINEERS, INC.
Example project A: Infrequent top chord yielding of coal cars
Suspension bottoming, or component strength?
2007OBJECTIVE ENGINEERS, INC.
-5000
-4000
-3000
-2000
-1000
0
1000
0 10 20 30 40 50 60Train Speed (mph)
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6000 miles later; several dozen data bursts in 5 general groups
-3500ueDesignLimit
2007OBJECTIVE ENGINEERS, INC.
Vertical Bounce Detail ~ 1.9 Hz: Strain, neg(Accel.), Spring Deflection
Time (Secs)4 4.5 5 5.5 6 6.5 7
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
-1.2
-1.4
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-0.5
-1
-1.5
-2
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6
(
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-800
-1000
-1200
-1400
-1600
-1800
-2000
-2200
-2400
-2600
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2007OBJECTIVE ENGINEERS, INC.
Vibration issue: Over time, a little bounce leads to more bounce
2007OBJECTIVE ENGINEERS, INC.
Quasi-static event: Rotary Car Dumper Coal Unloading ~ highest strains of test
2007OBJECTIVE ENGINEERS, INC.
Example project B: Development of a test spec. for aftermarket hardware
ABCD
TOR nozzle location at end of sand bracketTruck frameElectrical control cabinetCompressor room floor
(Note: Locationsvary slightly withlocomotive type)
2007OBJECTIVE ENGINEERS, INC.
1
10
100
1000
1 2 3 4 5 6 7 8 9 10Correlation with Field Environment
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-1 .5
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-0.5
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1 .5
0 1 2 3
Lab tests are always a compromise between reality and cost
Over-the-Road Simulation, Whole Vehicle
Sine Sweep or Dwell, Single Axis
Multiple Axes, Shaped Random
Single Axis, Shaped Random Single Axis, Shaped Random
0 500 1000 1500 2000
10-4
10-3
10-2
10-1
100
810F Min. Integrity = 7.6 grms
MIL-STD-810F and IEC61373 Vibration Spectra
Frequency (Hz)
V
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)
810F Rail 0.49 grms
IEC bogie long. 2.0 grms
IEC bogie lat. 3.8 grms
IEC bogie vert. 4.3 grms
Single Shaker, Random Flat PSD
2007OBJECTIVE ENGINEERS, INC.
Mid-cost & moderately real: Random Shaker Input With Same Frequency Content As Field
time (secs)232 233 234 235 236 237
10
5
0
-5
-10
-15
S
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F
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a
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A
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c
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(
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)
CD12_072 Y
time (secs)70 71 72 73 74 75
10
5
0
-5
-10
-15
S
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F
r
a
m
e
A
c
c
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l
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(
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)
CD3_072 Y
time (secs)215 216 217 218 219 220
10
5
0
-5
-10
-15
S
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CD6_121 Y
97th Percentile Data Records
Random shaker drive file with similar energy distribution; similar
but more frequent peaks
66
72.080.1250
=
=
fieldRMS
labRMS
gg
5 second segment0
15
10
5
0
-5
-10
-15
S
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(
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Random Vibration with similar Energy Distribution as SideFrame
(e.g. Time Compression 250X)
2007OBJECTIVE ENGINEERS, INC.
Data collection on locomotive type A: Sander Bracket
Tri-axial access. on sander bracket:
at side frame (upper)
at free end (lower)
2007OBJECTIVE ENGINEERS, INC.
Data collection on locomotive type B: Sander Bracket
2007OBJECTIVE ENGINEERS, INC.
Revenue Service Routesfor Locomotive Vibration Tests
2007OBJECTIVE ENGINEERS, INC.
Overall Comparison PeakAccelerations versus Location
1
10
100
1000
Contr
oller
Fron
t Plow
Lube
Res
.Sid
e Fram
e
Sand
er Re
sps.
Journ
al Bo
xMa
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A
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)
2007OBJECTIVE ENGINEERS, INC.
Field Data to Lab Test Conversion Process
z Reduce field data Using all valid files, compute aggregate (damage-
equivalent) side frame RMS accelerations Envelope resulting shape of severe PSDs (power
spectral densities)z Simplify PSD envelope, amplify to compress shake
table time Select 10-20 breakpoints for PSD shape Scale for 250:1 time compression vs. field
z Augment 8-hour shaker period (per axis) with brief segments achieving similar g level extremes as found in field data
2007OBJECTIVE ENGINEERS, INC.
Locomotive Bearing Box Raw Vibration
time (secs)327.4 327.5 327.6 327.7 327.8
120
80
40
0
-40
-80
-120
time (secs)327.4 327.5 327.6 327.7 327.8
120
80
40
0
-40
-80
-120
251. g peak-to-peak, vertical direction
Almost all energy around 500 Hz
Estimated 0.01double amplitude displacement
2007OBJECTIVE ENGINEERS, INC.
Locomotive Bearing Box Same data in freq. domain (PSD)
Block length = second
Bandwidth = 2 Hz
N=144 blocksFrequency (Hz)
0 100 200 300 400 500 600 700 800 900 1000
101
100
10-1
10 -2
10 -3
10 -4
(
(
g
)
)
Frequency (Hz)0 100 200 300 400 500 600 700 800 900 1000
101
100
10-1
10 -2
10 -3
10 -4
(
(
g
)
)
2007OBJECTIVE ENGINEERS, INC.
Most Severe Spectra from 2 loco. types and two service routes
Frequency (Hz)25 50 75 100 125 150 175 200 225 250
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
A
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^
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/
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)
Lateral Spectra (Auto Parts Service)10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
Frequency (Hz)25 50 75 100 125 150 175 200 225 250
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
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Lateral Spectra (Coal Service)10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
10 0
10 -1
10 -2
10 -3
10 -4
10 -5
2007OBJECTIVE ENGINEERS, INC.
PSD Envelope of Many Field Spectraand simplified shake table Breakpoints
200 400 600 800 1000
10-4
10-3
10-2
10-1
100g
*
g
/
H
z
Freq. (Hz)
Overall lateral ampl. using breakpoints: 1.8 g RMS
200 400 600 800 1000
10-4
10-3
10-2
10-1
100g
*
g
/
H
z
Freq. (Hz)
Overall lateral ampl. using breakpoints: 4.47 g RMS
200 400 600 800 1000
10-4
10-3
10-2
10-1
100g
*
g
/
H
z
Freq. (Hz)
Overall lateral ampl. using breakpoints: 1.8 g RMS
2007OBJECTIVE ENGINEERS, INC.
Summary of Shake Table Amplitudes (compared to MIL & Euro. specs)
Location 120-day Simulations Brief Field ExtremesCab Vertical 0.26 1.32 0.81Compressor Vertical 0.52 1.31 0.81Plow Longitudinal 0.26 1.44 0.40Sideframe Lateral 1.80 4.32 3.77Unsprung Vertical 10.5 44.5 30.6MIL-STD-810F Rail Transport
0.49
MIL-STD-810F "Minimum Integrity" 7.7
Proposed Shake Table Vibration (g RMS) IEC 61373
"Long Life"
2007OBJECTIVE ENGINEERS, INC.
Finally Add Representative Thermal Cycling (-40 to 130 F)
012345
V
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(
g
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S
)
0306090
120150
Time
T
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LateralDay 1
Long.Day 2
Vert.Day 3
Lat.Day4
Record Vibr. andSample Spray 2-Minute Field Extremes
2007OBJECTIVE ENGINEERS, INC.
Proof of test: freezing, shaking & baking a locomotive rail friction-modifier nozzle.
Electro-magnetic shaker with 15000 pounds of force
Heating/cooling source
2007OBJECTIVE ENGINEERS, INC.
Collection Grid Pans to check Spray Pattern and Application Amount
2007OBJECTIVE ENGINEERS, INC.
Final product: AAR spec. of minimum performance, before fleet installations
Clean nozzle After build-up
2007OBJECTIVE ENGINEERS, INC.
0 5 10 15 20 25 3010
-3
10-2
10-1
100
Human Comfort Issues ISO-2631 (empirical weighting of spectra)
Original Signal 0.83 g rms
Energy Spectrum
Weighting Values
Final Area 0.63 g weighted
0 30 Hz
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1
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0
%
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z
Time (sec)PSD
Similar process for noise dBA
2007OBJECTIVE ENGINEERS, INC.
TYPICAL SHOCKS
Car coupling In-train forces (slack action) Wheel imperfections Suspension bottoming out Rattling pieces
2007OBJECTIVE ENGINEERS, INC.
Coal Car Project A -- revisitedZero Speed Yard Data, Unattended (unexplained)
0.2
0
-0.2-1
-1.2
-400-1000-1600-2200
Time (Secs)993600 10 6 1.02*10 6
10
5
0
Vertical Car Body Accel.
Vert. Spring Defl.
Top Chord Strain
Train Speed
1 4 1 5 1 6
-1 6 0 0
-2 0 0 0
-2 4 0 0
-2 8 0 0
-3 2 0 0
-3 6 0 0
-4328 ue for 1/15th sec, then 2 hours at 2000 ue before relaxing
2007OBJECTIVE ENGINEERS, INC.
0 1 2 3 4 5 6 7
x 104
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Accel
Shock events produce accelerations with energy into higher frequencies
2007OBJECTIVE ENGINEERS, INC.
0 1 2 3 4 5 6 7
x 104
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Strain Gage
But unlike car bounce, the shock accelerations are not scaled duplicates of strains
2007OBJECTIVE ENGINEERS, INC.
And thus, a common 4g Design spec. willbe exceeded by high-freq. accel. data
2007OBJECTIVE ENGINEERS, INC.
One coupling shock: accel. filtered at 4 freqs., and coupler load cell trace
2007OBJECTIVE ENGINEERS, INC.
Similar sampling/filtering questions for various impacts related to passing wheels.
_ _ _
Collection Time(secs)20 40 60 80 100 120
-300-200-1000
100200300
Filter_010.sif - [email protected]_1.f.f
Collection Time(secs)20 40 60 80 100 120
-300-200-1000
100200300
Original Data Lowpassed at 333Hz=fc
After instead applying 10 Hz Lowpass filter
Revenue Train Sampled at 1000 Hz
2007OBJECTIVE ENGINEERS, INC.
Zoom in on only 6 seconds
Original Data 333Hz=fc
Filter_010.sif - [email protected]_1.f.f
Collection Time(secs)60 61 62 63 64 65 66
-300-200-1000
100200300
After applying 10 Hz Lowpass filter
_ _ _
Collection Time(secs)60 61 62 63 64 65 66
-300-200-1000
100200300
2007OBJECTIVE ENGINEERS, INC.
Rail Strain Gage with various lowpass filtering
0%10%20%30%40%50%60%70%80%90%
100%
0 50 100 150 200 250 300 350
Filter cutoff Frequency (Hz)
P
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MaxMinRMS
Max is 95%
Min is 41%, Whats going on?
2007OBJECTIVE ENGINEERS, INC.
Answer found by again zooming in on the original data
Collection Time(secs)60.00 60.25 60.50 60.75 61.00
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-300
-200
-100
0
100
200
300
Different frequency content !
2007OBJECTIVE ENGINEERS, INC.
A SAMPLING OF INDUSTRY STANDARDS (S&V and related issues)
Car body stability & healthTrack health
Car component health
Cargo stability & healthLongitudinal shock
Human stability & comfort
Locomotive specific issues
z FRA 213 Track Geometryz AAR Chapter XI, and M-
976 specsz Wheel Impact Detectorsz AAR S-4200 ECP brake
specz pending AAR brake beam
workz IEC-61373z AAR Dam. Prev. Stds.z MIL-STD-810z ISO-2631 ride comfortz AAR on-board rail
lubricator vibration spec
2007OBJECTIVE ENGINEERS, INC.
Another recent example, AAR S-4200 ECP brake spec
Design to withstand:z Vibrations 0.4 g rms 1-150 Hz (with +/-3 g
peaks)z Half-sine shocks of 10g peak (20 50 msec)z If on car strength members, local
resonances can raise levels to: 15g (100-150 Hz) 50g (200-500 Hz)
2007OBJECTIVE ENGINEERS, INC.
S & V MITIGATION TECHNIQUES
z Limit input energy availableTrack geometry standardsWheel flat limits, wheel impact detectors
z Interrupt transmission paths Spring/elastomer isolators
between car components between loco. structure & crew track to ground
z Add damping, stiffness, mass
2007OBJECTIVE ENGINEERS, INC.
Limit the dynamic excitations to carsvia geometry or speed limits
2007OBJECTIVE ENGINEERS, INC.
Title 49 CFR, Part 213Track Safety Stds. (track geometry specs.)
2007OBJECTIVE ENGINEERS, INC.
WILD Detectors: maintain wheels based on revenue track impacts
2007OBJECTIVE ENGINEERS, INC.
Transmission and reflections of rail vibration are highly site dependent
from Transit Noise and Vibration Impact Assessment, Hanson, Towers, and
Meister, Fed.Transit.Admin. 2006
2007OBJECTIVE ENGINEERS, INC.
Earth vibration due to freight trains
50556065707580859095
0 10 20 30 40 50Distance from Track (m)
G
n
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(
f
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6
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)
2007OBJECTIVE ENGINEERS, INC.
Noise, Squeal and Corrugation(A human perception problem)
z Potential Solutions Grinding to remove
corrugation Improve curving via
W/R profile Lubrication Reduce surface
roughness of wheel turning and rail grinding
Structural or surface changes to wheel (block or cut sound transmission path)
2007OBJECTIVE ENGINEERS, INC.
Chicago Transit Authority: Wheel screech damper
2007OBJECTIVE ENGINEERS, INC.
More costly transit N&V mitigation
2007OBJECTIVE ENGINEERS, INC.
Example project C: (rarely) we come across a beneficial use of vibration
z Civil engineers brought us dynamic track stabilization for after tamping operations
z Essentially a combination of adding stiffness/strength via aggregate material
change delaying the time when small bounces will
beget bigger bounces
2007OBJECTIVE ENGINEERS, INC.
Ballast Stabilization (Use of vibration to control track settlement)
2007OBJECTIVE ENGINEERS, INC.
Track stabilization worth about 10-20 trains of otherwise slow ordered traffic
2007OBJECTIVE ENGINEERS, INC.
Thus, the desired vibration lessens chances of this: Lateral Track (Panel) Shift
2007OBJECTIVE ENGINEERS, INC.
Another potential beneficial use
z From this campus, Dr. Weavers research on rail neutral temperature
zWavelength of high frequency rail vibrations changes with longitudinal stress on the rail
z Goal: Non-destructive determination of rail neutral temperature.
2007OBJECTIVE ENGINEERS, INC.
RAIL VIBRATION COMPARED TO
OTHER TRANSIT MODES
(Example projects C & D)
2007OBJECTIVE ENGINEERS, INC.
First some
antique video
footage
2007OBJECTIVE ENGINEERS, INC.
Moving Cargo, Containers and Operators
2007OBJECTIVE ENGINEERS, INC.
Evolved from two projects involving weld failures on ISO tank containers
2007OBJECTIVE ENGINEERS, INC.
Unattended Container Shock Record(Does/does not exceed 4g Design Std?)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-30
-20
-10
0
10
L
o
g
g
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d
E
v
e
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V
a
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(
g
)
SN 13392 Event 39, Long.
Original extremum value: 20.4
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-10
-5
0
5
F
i
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t
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d
V
a
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s
(
g
)
Time (sec)
8.6 = extremum after 90 Hz lowpass3.5 = " " 40 Hz "2.5 = " " 30 Hz "1.3 = " " 16 Hz "
-20.4 g raw data?
-2.5g after 30 Hz lowpass filter
2007OBJECTIVE ENGINEERS, INC.
Well then, this is a much lower frequency event, surely it is abusive
-30.0
-22.5
-15.0
-7.5
0.0
+7.5
+15.0
+22.5
+30.0
0.0 0.1 0.199 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
g
Seconds
g ggX Y Z
Integrating the accel. signal yields a velocity change of 102 mph in 1/3 second. Invalid data!
2007OBJECTIVE ENGINEERS, INC.
Vibration for many vehicles
compared
(Bob Fries, N.Cooper-rider 1993)
2007OBJECTIVE ENGINEERS, INC.
TECHNICAL OBSERVATIONSz The highway truck environment is generally more
harsh on cargo & humans than rail. Shipboard environment is generally less harsh than rail. Ship environment is more like a factory floor.
z Low frequencies (
2007OBJECTIVE ENGINEERS, INC.
Observed & periodic opportunity for engineering confusion
CarModel
+VA
Load Measuring Axle
+Y
+LB+LA +T
+VB
+Z+X
+T
2007OBJECTIVE ENGINEERS, INC.
Another test risk: small populations
Four strain gages at same locations on cantilever beam next to fixed end.
(22 long, 3 wide,
1/16 thick)
2007OBJECTIVE ENGINEERS, INC.
Strain variations, even with careful attention to similar gage placement
Time (secs)25.3 25.4 25.5 25.6 25.7
300250200150100500
-50-100-150-200-250
g
a
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(
m
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)
4 gages at 1st bending freq. ~ 3 Hz
300250200150100500-50-100-150-200-250
g
a
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e
4
(
m
i
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r
o
s
t
r
a
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)
13% Variation in
Peak-to-peak
g3 = 543ue
g4 = 502ue
g7 = 477ue
g8 = 521ue
2007OBJECTIVE ENGINEERS, INC.
What about variations on a railcar?Structural member strains, Left vs. Right
time(secs)245 250 255
-200
-100
0
100
200
300
50% difference in amplitude.
2007OBJECTIVE ENGINEERS, INC.
Final reminder: accelerations vs. strains
CB_VT_SQBURST.SIF Channel 4
-8-6-4-2024
CB_VT_SQBURST.SIF - Channel 5
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CB_VT_SQBURST.SIF - Channel 6
time(secs)245 250 255 260 265
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Low freq. correlation, but not at high freqs.
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2007OBJECTIVE ENGINEERS, INC.
Wrap-up: industry trends relating to S&V
z Perfect engineering specification would fail 100.0% of latent bad designs or processes, while passing 100.0% of the good.
z Actual specifications tended to promote certain dimensional tolerances, minimum design strengths, or perfunctory initial performance not perfect.
z For about a decade, advances in technology have gradually begun to provide operational feedback, largely due to monitoring shock and/or vibration (or close cousins).
2007OBJECTIVE ENGINEERS, INC.
Implementation risksThis monitoring of S&V (or close cousins) can be
infinitely more complex than the old visual inspection. Thus, there is much concern about the false positives or negatives.
Fortunately, the industry is gradually moving ahead:z Wheel Impact Monitorsz Acoustic Bearing Signaturesz Excessive Railcar Bouncez Peak Wheel Forcesz Yard Coupling Shocks, or desired lack thereofz etc.
2007OBJECTIVE ENGINEERS, INC.
Two opinions about S&V work in railroading
z PLUS: In an otherwise mature industry, further exploiting shock and vibration to assist business decisions holds great opportunity for rail engineers.
z MINUS: Fostering adoption of these technologies requires great patience and persistence. (Railroads, suppliers, shippers, car owners, and the FRA have a complicated and symbiotic relationship. In some cases, these newer and more effective specifications redistribute costs. This may be unpopular.)
2007OBJECTIVE ENGINEERS, INC.
Example project E: 1994 brake beam tests. Adoption of standards is still in-process
2007OBJECTIVE ENGINEERS, INC.
Give an engineer just a simple request
2007OBJECTIVE ENGINEERS, INC.And the engineer will aim to please
2007OBJECTIVE ENGINEERS, INC.
2007OBJECTIVE ENGINEERS, INC.
Engineering Information is not the same thing as test (or analysis) data
Like Dilbert, we need to provide information, not just data, Here is $7.14, you owe
me five & a quarter.