Crack Paths 2009

that occurred regularly during spectrum loading testing, transverse anti-buckling

supports were used.

Equation 1 can be used as a measured of the equivalent constant amplitude stress

range for a variable amplitude history. For the S960 load spectrum (Fig 2a) used in this

study,

eq

= 0.337 max

for m=5and eq

= 0.313max for m=3. For the S700 load

eq

eq

max

spectrum (Fig 2b) used in this study,

= 0.439

for m=5 and

=

0.389max for m=3.

n

m

N 



i i

m

i



  

1

(1)

eq

N

total

cycle / cumulative distribution

cycle / cumulative distribution

1

1

plitud e

0.8

0.8

.a m

0.6

0.6

a x

p elitud / m

0.24

0.4

0.2

am

0

0

cycles

10

1

100

1000

10000 100000

1

10

100 1000 10000 100000 1000000 1E+07

cycles

a)

b)

100

80

60

40

20

0

1

3

5

7

9

1 1

1 3

1 5

1 7

1 9

2 1

2 3

2 5

2 7

2 9

3 1

3 3

3 5

3 7

3 9

4 1

4 3

4 5

4 7

4 9

5 1

5 3

5 5

5 7

5 9

6 1

6 3

6 5

-20

-40

-60

-80

-100

c)

time

Figure 2. Distribution of fatigue cycles in the load spectrum for the a) S960 specimens

and b) S700 specimens. C) Sample from one short segment of the spectrum.

Post-weld treatments

The post-weld improvement techniques chosen either ultrasonic impact treatment (UIT)

[21] or ultrasonic peening (UP) [22]. Both devices are hand held units powered with

ultrasonic generator. Ultrasonic elements within the body of the device cylindrical

276 4