140
Z. Wang et al.
0
200
400
600
800
1000
t / min
0
2
4
A / V
Event Count
Average Event Ring Count
Maximum Ring Count
Total Ring Count
Average Event Rise Time
Average Event Duration
Average Event Amplitude
0
2
4
6
8
1 0
t / s
-0.1
0
0.1
Amplitude
A / V
A
C
7.74
7.75
7.76
7.77
7.78
7.79
t / s
-0.1
0
0.1
Amplitude
A /
V
B
0
2
4
6
8
1 0
t / s
-0.1
0
0.1
Amplitude A / V
V Shape
0
2
4
6
8
1 0
t / s
-0.5
0
0.5
Amplitude A / V
D
B
Fig. 13.4 Trends of improved AE index and stage observations
is divided into A area (between [0,160.7]), B area (between [160.7,863.7]), C area
(between [863.7,1055]) and D area (between [1055,1160]).
A area stage is a process with small shocks. A quick saltation appears at the end
of the stage (V shape) before it goes into B area. Event count has the most volatility
in A area. Ring count maximum and total ring count have the 2nd and 3rd volatility
respectively. Other indexes are relatively steady. At this stage, AE signal has no
obvious impact and the background noise is large. The reason for this may be the
micro-plastic deformation that leads to a large number of AE events. No obvious
damage is found in disassembly observation of ball bearing at this stage. To define
this phase as a running initial stage.
The trend of each index remains relatively stable in B area with a long period of
relative stability. However, individual AE event during this period is emerged. Slight
damage on race surface of ball bearing in this stage is observed with color industrial
camera as shown in Fig. 13.4. By measurement and calculation, the size of the slight
damage is around 0.05 mm (50 micron). The damage length direction is almost in
line with the rolling direction (see the arrow in Fig. 13.4). Therefore, it is likely to
be the period of subsurface crack initiation that leads to the slight damage at the
beginning of the stage. In B area, the stability performance of improved AE index
may be due to the stabilization of the microplastic deformation process. Newlyformed
surface damage is compacted rapidly (work hardening) and that restrains the damage
expansion. There’s a new stress concentration which is occurred around the damage.
This will become the main damage source in the subsequent evolutionary stage in a
very high probability. This stage is defined as slight damage stage.
In C area, steady ascent appears around 863 min. AE amplitude gradually
increased at this stage. There are many shocks in AE signal. It has a certain random
characteristic. It is observed that a slight pitting occurs at the same location as the
slight damage by shutdown observation of the test rig. The size of the pitting is about
Z. Wang et al.
0
200
400
600
800
1000
t / min
0
2
4
A / V
Event Count
Average Event Ring Count
Maximum Ring Count
Total Ring Count
Average Event Rise Time
Average Event Duration
Average Event Amplitude
0
2
4
6
8
1 0
t / s
-0.1
0
0.1
Amplitude
A / V
A
C
7.74
7.75
7.76
7.77
7.78
7.79
t / s
-0.1
0
0.1
Amplitude
A /
V
B
0
2
4
6
8
1 0
t / s
-0.1
0
0.1
Amplitude A / V
V Shape
0
2
4
6
8
1 0
t / s
-0.5
0
0.5
Amplitude A / V
D
B
Fig. 13.4 Trends of improved AE index and stage observations
is divided into A area (between [0,160.7]), B area (between [160.7,863.7]), C area
(between [863.7,1055]) and D area (between [1055,1160]).
A area stage is a process with small shocks. A quick saltation appears at the end
of the stage (V shape) before it goes into B area. Event count has the most volatility
in A area. Ring count maximum and total ring count have the 2nd and 3rd volatility
respectively. Other indexes are relatively steady. At this stage, AE signal has no
obvious impact and the background noise is large. The reason for this may be the
micro-plastic deformation that leads to a large number of AE events. No obvious
damage is found in disassembly observation of ball bearing at this stage. To define
this phase as a running initial stage.
The trend of each index remains relatively stable in B area with a long period of
relative stability. However, individual AE event during this period is emerged. Slight
damage on race surface of ball bearing in this stage is observed with color industrial
camera as shown in Fig. 13.4. By measurement and calculation, the size of the slight
damage is around 0.05 mm (50 micron). The damage length direction is almost in
line with the rolling direction (see the arrow in Fig. 13.4). Therefore, it is likely to
be the period of subsurface crack initiation that leads to the slight damage at the
beginning of the stage. In B area, the stability performance of improved AE index
may be due to the stabilization of the microplastic deformation process. Newlyformed
surface damage is compacted rapidly (work hardening) and that restrains the damage
expansion. There’s a new stress concentration which is occurred around the damage.
This will become the main damage source in the subsequent evolutionary stage in a
very high probability. This stage is defined as slight damage stage.
In C area, steady ascent appears around 863 min. AE amplitude gradually
increased at this stage. There are many shocks in AE signal. It has a certain random
characteristic. It is observed that a slight pitting occurs at the same location as the
slight damage by shutdown observation of the test rig. The size of the pitting is about