Crack Paths 2009

1200

1200

10178900

ten.-comp.

10

tp45°o9r0r°os.p.

1100

ten.-comp.

tors.

prop.

1000

45°

90°

900

800

m a x

700

600

600

500

10 2

10 3

10 4

10 5

10 6

500

3

4

5

6

10

10

10

N

Nci or Nf

cgr

Figure 14. Crack-initiation and failure

Figure 15. Crack growth lives

lives

Out of these experiments the following conclusions can be drawn:

• Depending on the loading type, two to four cracks initiate as corner cracks on

the inner side of the specimen on different positions within the slot.

• Under pure tension-compression loading pure mode I crack growth has been

observed.

• Under pure torsional loading four cracks initiated and grow firstly under an

angle of about 45° degree to the longitudinal axis. With increasing crack length

the cracks grow in a plane which is perpendicular to the longitudinal axis.

• The crack growth behavior of specimens under proportional and out-of-phase

loading with a phase angle of 45° are similar.

• Under out-of-phase loading with a phase angle of 90° various different types of

crack initiation and growth have been identified.

• The crack initiation life is almost independent of the load type

• Considerable differences for the failure and crack growth life have been found

for the five loading types

R E F E R E N C E S

1. Brüning, J. (2008). PhD. Thesis, Technische Universität Darmstadt, Germany.

2. Savaidis, G. (1995). PhD. Thesis, Technische Hochschule Darmstadt, Germany.

3. Hoffmeyer, J., Döring, R., Seeger., T., Vormwald, M. (2006) Int. J. Fatigue 28,

508-520

560