Prestressed%20bolt%20joints%20under%20dynamical%20load - PowerPoint PPT Presentation

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


1
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

2
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

3
We can find everywhere bolt joints
L
Notch effect
Detachable
J
4
Test bench
5
Three different end plate versions
6
The load spectras and the results of the tests
A2
A3
A1/1 and A1/2
7
The half FE model of the test bench
Contact area
Contact area
8
Simplified FE model of the bolt joint
Advantages

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

9
Load Case 1, Prestress of the bolts (minimal
load),

• On the flange plate

• On the I-beam

10
Load Case 2, The total load (maximal load),

• On the I-beam

• On the flange plate

11
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
12
FEMFAT calculation concept
Load spectra
FE model
s
s
ai
s
i
mi
N
s
s
mi
ai
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
.
D
s
D
.
c
s

k
m
i
.
c

s
m
Dn
13
Load case definition for Fatigue Analysis
Amplitude stress
Mean stress
14
Damage distribution on A1/1 without sequence
effect

• On the I-beam

• On the flange plate

15
Damage distribution on A1/2 without sequence
effect

• On the I-beam

• On the flange plate

16
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

17
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
!
18
Comparison the tests and the FEMFAT results
Test break
FEMFAT calculation without sequence effect
FEMFAT calculation with sequence effect
19
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
20
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.