PSI - Issue 13

Ralf Lach et al. / Procedia Structural Integrity 13 (2018) 34–38 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

36

3

and an electrically driven roll (to vary the frequency) in such a way that the rolling ring is loaded under rotating bending, i.e. one rotation of the driven roll corresponds to two deformation cycles. Both the deformation E x (typically in the range of 6 – 19 %), i.e. the eccentricity of the rolling rings, and the frequency (rotational frequency: 100 – 250 min – 1 ) of the rotating bending can be varied. After rupture of the rolling ring the number N B of cycles at break is used as a measure of the lifetime. To analyze the lifetime as a function of the deformation the rotating bending was set to be 250 min – 1 . In any case five independent measurements of N B were performed for each data point. For calibration of the load the rolling rings were quasi-statically tested using the uniaxial compression test. All tests were performed under standard conditions (23 °C, 50 % relative humidity).

11 12 13 14

b

a

6

1

16

2

5

3

4

7

15

10

8

9

Fig. 1. Rolling ring tester: (a) front view (1 – rolling ring, 2 and 3 – bearings, 4 – movable roll, 5 – driven roll, 6 – motor, 7 – slide, 8 – base, 9 – spacer) and (b) top view (10, 11 and 12 – bearings slides, 13, 14 and 15 – screws, 16 – adjusting screw).

10 12 14 16 18 Deformation E x in %

b

10 12 14 16 18

a

Low cycle fatigue

Deformation E X in %

Fatigue life

6 8

0 40000 80000 120000 160000 6 8 No break

10 0

10 1

10 2

10 3

10 4

10 5

Number of cycles at break N B

Number of cycles at break N B

Fig. 2. Number of cycles at break ( N B ) depending of the deformation E x of laser sintered rolling rings made of PA12: (a) linear plot and (b) logarithmic plot; energy density: 160 Ws/cm 3 ; rotating bending: 250 min – 1 ; the straight lines are according to the best data fit using Equation (1).