Shear Stress and Strain Shear Stress, Shear Strain, Shear Stress and Strain Diagram 1.
LBF-TITELFOLIE / Titel in VERSALIEN schreiben · November 11 th, 2015 . Robert Keplin M.Sc. ......
Transcript of LBF-TITELFOLIE / Titel in VERSALIEN schreiben · November 11 th, 2015 . Robert Keplin M.Sc. ......
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UC 12 12th Users Conference on BiAxial Fatigue Testing
November 11th, 2015
Robert Keplin M.Sc. Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF www.lbf.fraunhofer.de
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LOAD FILE DEVELOPMENT
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Content
Load file fundamentals
Specification of a load file
Basic load file development process
Load file development for 3 axle semi-trailer application
Used wheel end instrumented with strain gauges
Local strain measurements for transformation of wheel loads to test rig loads
Process for load file development of used wheel end
Summary
Outlook
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Specification of a load file for a LBF BiAxial fatigue test machine LBF load file is specified by:
Combination of different actuator load sequences (vertical and lateral direction) in kN
Defined drum speed for each load sequence in km/h
Defined length of time for each load sequence in sec
By means of a test load file a correct correlation between the LBF design spectrum and the BiAxial time reduced test spectrum shall be given in terms of loading, stress and damage content
Seq Fv Fh v t[kN] [kN] [km/h] [sec]
1 37.5 0.00 73 18.02 50.0 27.50 73 6.03 25.0 7.50 73 15.04 37.5 0.00 73 43.55 62.5 29.00 73 6.0
98 45.0 21.00 73 2.099 37.5 0.00 73 30.1
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Basic load file development process (I)
Results of experimental stress analysis on LBF flat track are input for the load file development
Load assumptions
Determination of local peak stresses by measurements of local strains on LBF flat track
Derivation of the LBF design spectrum and calculation of RFS values − Required Fatigue Strength − for the relevant locations
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Basic load file development process (II)
Transformation of wheel loads to test rig loads by means of damage accumulation on the basis of local strain measurements in BiAxial test rig
Accurately stress reproduction for all design load cases
Measurements of local strains in BiAxial test rig for complete period of load sequences
Comparison of measured BiAxial test spectrum to LBF design spectrum via RFS value concept
Load file / load sequence adjustment until required analogy is given in terms of damage content
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Test duration for heavy duty truck application − front axle
Steel wheels and cast-iron hubs: 16,000 km
Basic Design Spectrum for 500,000 km of Service and Test Spectrum for heavy duty trucks (front axle)
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Load file development for 3 axle semi-trailer application
Seq Fv Fh v t[kN] [kN] [km/h] [sec]
1 37.5 0.00 73 18.02 50.0 27.50 73 6.03 25.0 7.50 73 15.04 37.5 0.00 73 43.55 62.5 29.00 73 6.0
98 45.0 21.00 73 2.099 37.5 0.00 73 30.1
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Wheel end for 3 axle semi-trailer − European usage
11.75x22.5 inset120 steel wheel typical semi-trailer wheel for European usage
Rated wheel load: 4.500 kg
Tire size: 385/65 R 22.5
No. of studs: 10
Pitch circle: ø335 mm
Stud hole diameter: ø26 mm
No. of ventilation holes: 10 aligned to area between stud hole center
Ventilation hole design: oval
Valve hole: aligned to ventilation hole center
mating flange thickness: ca. 13 mm
Hub system w/ brake disk typical semi-trailer hub system for European usage
Rated wheel load: 4.500 kg
Hub system consist of:
Hub flange (cylindrical | cast-iron)
Brake disk
Hub-unit
No. of studs / stud size:10 / M22x1.5
Brake disk: screwed w/ wheel studs
Hub-unit: screwed w/ flange screws M18x1.5
No. of flange screws: 12
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SGs used at different locations on the wheel and the hub flange
Wheel end instrumented w/ strain gauges
exemplary cross section wheel
exemplary cross section wheel end
23 SGs on wheel 4 on wheel flange outside 2 on mating flange 3 on disc radius inside 4 on ventilation hole inside 3 on ventilation hole outside 2 close to welding line 1 close to valve hole 2 on drop center 1 on rim well 1 on inner rim flange
9 SGs on hub flange 3 on radius behind wheel bolt head inside 3 on radius wheel centering outside 2 on casting skin inside 1 on casting skin outside
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Most important SGs used for the measurement of local strains in LBF BiAxial test rig
Wheel end instrumented w/ strain gauges
exemplary cross section wheel
exemplary cross section wheel end
6 SGs on wheel 1 on wheel flange outside, close to
wheel nut contour (screwing area) 1 on mating flange, pretty close to
the hub flange contour 1 on ventilation hole inside
(peak stress area) 1 on ventilation hole outside 1 close to valve hole (rim well area) 1 on inner rim flange 2 SGs on hub flange
1 on radius wheel centering outside 1 on casting skin inside (close to wheel bolt head |
peak stress area)
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Local strain measurement w/ 8 channel telemetry system
Using of high-precision telemetry system by datatel for the wireless transmission of the measured strains
6 measuring channels used for wheel structure
2 measuring channels used for hub flange structure
Sample rate: 200 hz
Operable temperature range of transmitter: 0 to 85 °C
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BiAxial fatigue testing Realistic wheel loads while testing
Straight driving Cornering Rough road
Different actuator forces are needed for generation of equivalent wheel forces/local stresses by tilting and running against sidewalls of inner drum system
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-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70
Vert
ical
whe
el lo
ad [k
N]
Lateral wheel load [kN]
Design load cases
Transformation of wheel loads to test rig loads Accurately stress reproduction for design load cases
Cornering
Actuator load combination
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Transformation of wheel loads to test rig loads Accurately stress reproduction − iteration loops
Many iteration loops needed until measured stresses are reproduced in an adequate way for all design load cases and each strain gauge
Inner rim flange
Ventilation hole inside
Mating flange inside
Ventilation hole outside
Wheel flange outside
Valve holeVertical Lateral
MPa in % MPa in % MPa in % MPa in % MPa in % MPa in % kN in % kN in %100 100 100 100 100 100 100 100
1. iteration 92,0 85,0 93,0 87,0 86,0 94,0 100,0 100,0
Relative deviation [%] -9,00 -15,00 -8,00 -13,00 -14,00 -7,00 0,00 0,00Absolute deviation [MPa] -12,00 25,00 -9,00 -20,00 -15,00 -6,00 0,00 0,00
2. iteration 95,0 92,0 96,0 93,0 93,0 96,0 105,0 110,0
Relative deviation [%] -5,00 -8,00 -4,00 -7,00 -7,00 -4,00 5,00 10,00Absolute deviation [MPa] -7,00 -13,00 -5,00 -10,00 -8,00 -3,00 4,00 3,00
Strain gauges on wheel structure Design load case cornering
Stresses for design load case Wheel loads
Actuator loadsMeasured stresses
X. iteration 102,0 99,0 103,0 101,0 102,0 104,0 110,0 120,0
Relative deviation [%] 2,00 -1,00 3,00 1,00 2,00 4,00 10,00 20,00Absolute deviation [MPa] 3,00 -2,00 4,00 2,00 3,00 3,00 8,00 6,00
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Final load file development − Transformation of wheel loads to test rig loads by means of damage accumulation
Damage accumulation
Analysis: BiAxial test spectrum vs. LBF design spectrum
Load file development/ adjustment until required analogy is given in terms of damage content
Measurements of local strains on BiAxial test rig for complete period of load sequences
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Developing of an adequate wheel load file for 3 axle semi-trailer application
Specification of the wheel test load file
Test load file consists of 99 load sequences
Driven distance of one period − 99 load sequences: ca. 65 km
Test duration: 16,000 km − ca. 246 repetitions
Matched to a drum speed of 73 km/h and an inner drum size of 1.8 m
Load sequences mixed for good drivability
Cover new LBF design spectrum for 3 axle semi-trailer application (500,000 km) in a good way Seq Fv Fh v t
[kN] [kN] [km/h] [sec]1 37.5 0.00 73 18.02 50.0 27.50 73 6.03 25.0 7.50 73 15.04 37.5 0.00 73 43.55 62.5 29.00 73 6.0
98 45.0 21.00 73 2.099 37.5 0.00 73 30.1
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Inner rim flange Ventilation holeinside
Mating flange inside Ventilation holeoutside
Wheel flange outside Valve hole
RFS
valu
e no
rmal
ized
to m
axim
um v
alue
RFS LBF design Spectrum RFS Load File Semi-Trailer
Results overview Load file adjustment by means of RFS value concept
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LBF design spectrum vs. test spectrum Strain gauge on ventilation hole inside
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Inner rim flange Ventilation holeinside
Mating flange inside Ventilation holeoutside
Wheel flange outside Valve hole
RFS
valu
e no
rmal
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axim
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alue
fron
t axl
e
RFS Load File Front Axle [16,000 km] RFS Load File Semi-Trailer [16,000 km]
Load file comparison by means of RFS value concept Load file front axle vs. new load file semi-trailer
+2%
+3%
+4%
+1%
+7%
+1%
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Summary Up to now an adequate wheel test load file has been developed for typical
11.75x22.5 IS120 steel wheels for 3 axle semi-trailer application
New load file for trailer axle application is in all relevant locations of the wheel structure more severe than the basic load file for front axle application, especially in the wheel screwing area
Validity for hub:
There is a deviation between the wheel and the hub due to the different lateral load transmission on BiAxial test rig for the hub higher actuator loads are necessary
According to the current load file status the RFS value for the most critical location is about 6% too low extended test duration is needed
Validity for aluminum wheels:
Until now not enough measurements have been done for verification of the load file for aluminum wheels
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Outlook Current load file, which is valid for steel wheels, will be most likely available in
the final version within 1. Quarter 2016
Outlook for hub
More measurements still need to be done for final conclusion
According to current status mixed test strategy could solve the deviation between wheel and hub e. g. test the wheel at first and continue hub testing w/ increased test parameters (cv and ch)
Outlook for aluminum wheels
With SGs instrumented typical 11.75x22.5 IS120 aluminum wheel as well an accurate regression model is already available
More measurements still needed for final validation
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… we will keep your wheels running
Thank you for your attention.