Prestressed%20bolt%20joints%20under%20dynamical%20load

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Prestressed bolt joints under dynamical load

• Kerekes Ervin, Dr. Szabó Bertalan, Bernhard
  Unger
• Steyr-Daimler-Puch AG, Technologie Zentrum
  Steyr
• Department of Steel Structures, Technical
  University of Budapest

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Contents

• Introduction (TZS BME)
• Tests (test bench, load spectras, failures)
• FE model (whole structure, simplified bolt model,
  FE loads, stress distributions)
• FEMFAT concept (theoretical background)
• Fatigue estimation (fatigue load, damage
  distributions)
• Comparison between the tests and the calculations
• Conclusions

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We can find everywhere bolt joints
L
Notch effect
Detachable
J
4
Test bench
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Three different end plate versions
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The load spectras and the results of the tests
A2
A3
A1/1 and A1/2
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The half FE model of the test bench
Contact area
Contact area
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Simplified FE model of the bolt joint
Advantages

• few number of elements
• linear
• very fast
• enough precision

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Load Case 1, Prestress of the bolts (minimal
load),

• On the flange plate

• On the I-beam

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Load Case 2, The total load (maximal load),

• On the I-beam

• On the flange plate

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FEMFAT technical contents
Technological influence factors
Load spectra
FE stress data (linear stress tensors)
FEMFAT
Material data
Endurance safety factor
Damage factor
Brake safety factor
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FEMFAT calculation concept
Load spectra
FE model
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ai
s
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mi
N
s
s
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Neuber hypothesis
S/N curve
k
s
s
D1
ai
Relative stress gradient
s
D
N
D
e
s
S
D
mi
D2
i
s
c

k
D
c

N
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Dn
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Load case definition for Fatigue Analysis
Amplitude stress
Mean stress
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Damage distribution on A1/1 without sequence
effect

• On the I-beam

• On the flange plate

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Damage distribution on A1/2 without sequence
effect

• On the I-beam

• On the flange plate

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Damage distribution on the A1/1 and the A1/2
cases with sequence effect

• In the A1/1 case on the flange plate

• In the A1/2 case on the flange plate

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The photos of the breaks in the A1/1 and the A1/2
cases

• In the case of A1/1

• In the case of A1/2

Damage
Damage
!
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Comparison the tests and the FEMFAT results
Test break
FEMFAT calculation without sequence effect
FEMFAT calculation with sequence effect
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Why have we got difference?
Calculation side
Test side

• Linear and simplified hypothesis
• Material properties from literatures
• Simplified bolt model
• Lifetime sk ð small amplitude stress changing
  means high lifetime changing !

• Test failures
• Too few tests

D1.77 D1.07 D0.67
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Conclusions

• From the tests and fatigue estimation we can say,
  the dangerous places for this kind of load
  conditions are the middle screw bores on the
  flange plate.
• The too high prestress is the reason of this weak
  point
• The prestresses on the bolts mean a constant
  stress, and this is dominant for this type of
  load.