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continuous
C D
5.4 45-4,3 B C
5.5 40-4,3 C D
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VI DESIGN AND CALCULATION 78 | 79
The stress ratio, R, is the minimum
stress divided by the maximum
stress in a constant amplitude
stress history or a cycle
derived from a variable amplitude
stress history. Favourable
stress ratio will enhance the
fatigue strength for some cases
compared with the values given
in the standard. For initiation
sites in base material away from
connections, there will be an
increase in the fatigue strength
for R < +0.5. For initiation site at
welded or mechanical fastened
connections in simple structural
elements, where the residual
stresses has been established,
taking into account any preaction
or lack of fit, there will be an
increase in the fatigue strength
for R < -0.25. For other cases
there will be no change from the
values in the standard.
Some typical details categories
are shown in the Table VI.6. The
first row in the table gives the
detail type number, the second
row gives the detail category, the
third gives a sketch of the detail
and also showing the initiation
site and the direction of the
stress, the fourth gives the weld
type, the fifth gives the stress
parameter, the sixth gives stress
concentrations already allowed
for, the seven gives the welding
characteristics, the eight gives
the quality level for the internal
imperfections and the ninth gives
the quality level for the surface
and geometrical imperfections.
The requirements for the quality
levels are found in EN ISO 10042
and additional requirements are
given in EN 1090-3.
TABLE VI.6
Nominal stress at initiation site
Full penetration
butt weld
Weld caps ground
flush
Full penetration
butt weld
Continuous fillet
weld
At weld discontinuity
At weld discontinuity
At weld discontinuity
Δσ
Δσ
Δσ
Δσ
Δσ
Δσ
79
EUROPEAN ALUMINIUM ASSOCIATION
Detail types 5.4 and 5.5 are an
example where the same detail
has different fatigue strength
depending on the quality of the
weld.
The SN curves that correspond to
these detail categories are shown
on Figure VI.15.
The numerical values for the
same curves are shown in the
Table VI.7 :
INFLUENCE OF WELD QUALITY ON FATIGUE STRENGTH
FIGURE VI.15
500
400
300
200
150
100
50
40
30
20
15
10
5
Δσ
N/mm2
NC NO NL
104 103 106 107 108 109
63-4,3
56-4,3
45-4,3
40-4,3
36-4,3
28-4,3
S
N
80
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VI DESIGN AND CALCULATION 80 | 81
SLOPE Cycles N
m1 m2 1E+05 1E-06 2E+06 5E+06 1E+07 1E+08 1E+09
4,3 6,3 126,4 74,0 63,0 50,9 45,6 31,6 31,6
4,3 6,3 112,4 65,8 56,0 45,3 40,5 28,1 28,1
4,3 6,3 90,3 52,9 45,0 36,4 32,6 22,6 22,6
4,3 6,3 80,3 47,0 40,0 32,3 29,0 20,1 20,1
4,3 6,3 72,3 42,3 36,0 29,1 26,1 18,1 18,1
4,3 6,3 56,2 32,9 28,0 22,6 20,3 14,1 14,1
TABLE VI.7
Fatigue field test (Benalu)
81
EUROPEAN ALUMINIUM ASSOCIATION
The following sections shows
good and bad design solutions
for aluminium trailer chassis.
They all refer to the load case
described in Figure VI.16.
8.2. Practice: comparison between good and bad chassis solutions
7300
3000 2150
1000 1250
7300
115
N
cm
BOUNDARY CONDITIONS AND BEAM GEOMETRY AS A BASIS
FOR THE FINITE ELEMENT ANALYSIS
FIGURE VI.16
165
1900 941
R1000
7300
60
100
400
R1000
1
Load case with 0,5x115 N/cm is used (dashed rectangle).
Cross section of the beam is a simple symmetrical H-section with a flange-width of 150 mm,
flange-thickness of 12 mm and web-thickness 8 mm.
(1: To achieve the gooseneck, a part of the web has been cut off and re-joined by welding
at a distance of 60 mm from the lower flange.)
82
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VI DESIGN AND CALCULATION 82 | 83
8.2.1. Gooseneck
The Gooseneck area of the chassis
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