*3.1.2 Acoustic emission cumulative count versus standard cycle diagram*

The count is the number of pulses that exceed the specified threshold value [3, 10]. The cumulative count vs. normalized cycle diagram, in each standard cycle, shows the total number of counts of that cycle with previous cycles. The number of counts indicates the internal events of the material [11]. Therefore, where the counts reach their maximum value, the rate of internal events of materials is also at its maximum. After examining the amplitude vs. standard cycle diagram and determining the start cycle of changes in each specimen, to ensure the results are obtained, the cumulative count vs. standard cycle diagram is examined.

To study and analyze changes in cumulative graphs, slope changes in different parts of the graph are used. After examining the slope in different parts of the


**Table 1.** *Max. Signal amplitude and amplitude of start signal changes in each specimen.* cumulative count vs. standard cycle diagram, it was determined that before standard cycle NO. 10, an increase in slope is observed in all specimens, which is due to the instability of the conditions at the beginning of the test. After the simultaneous start of the acoustic emission system and the bending fatigue machine, the acoustic emission sensors receive the noise due to the mechanical vibration of the device after starting and display it as an acoustic emission signal which increases the slope in the cumulative counting vs. standard cycle diagram. The slope then continues almost uniformly until the same standard cycle as the amplitude of the signals began to increase, the slope of the cumulative count vs. standard cycle also begins to increase sharply. For example, the acoustic emission cumulative count vs. normalized cycle diagram for specimen NO. 9 is shown in **Figure 9**.

**Figure 10** shows the cumulative count vs. standard cycle diagrams for specimens NO. 1 to 9. In diagram of specimen NO. 1, in the standard cycle, approximately 68 to 76 diagrams are in a horizontal line, which is the reason for stopping

**Figure 9.**

*Acoustic emission cumulative count vs. standard cycle diagram of specimen NO. 9.*

**Figure 10.** *Acoustic emission cumulative count vs. standard cycle diagram for all 9 specimens.*
