PSI - Issue 58

K N Pandey et al. / Procedia Structural Integrity 58 (2024) 122–129 K. N. Pandey and G. Singh / Structural Integrity Procedia 00 (2019) 000–000

125

4

Table 2. PZT patch properties (Bhalla et al.et al., 2004). S. No Physical Parameter

Symbols

Value 6.3×10 10 / 2 -166×10 −12 / 1.5×10 −8 / 7650 kg/ 3 .012

31 ∈ ρ

1

Young’s modulus at constant electric field Piezoelectric strain coefficient Electric permittivity at constant stress

2 3 4 5 6 7

ℵ h

Density

Dielectric loss factor Mechanical loss factor Thickness of PZT patch

.001

.1mm

Table 3. Loading conditions.

��� (kN) ��� (kN)

R ratio

Frequency (Hz)

Load

Constant Amplitude Load

CAL - 1 CAL - 2

4.0 4.5 4.0 4.5 4.5 4.0

0.40 0.45 0.40 0.45 0.45 0.40

0.1 0.1 0.1

10

Block Loading

Block - Lo-Hi

Low High High Low

10

Block - Hi-Lo

0.1

10

Fig. 2. LCR meter (HIOKI IM 3538).

First of all constant amplitude load (CAL) fatigue tests were conducted to determine the life under CAL at two levels of the maximum stresses at which the block loading tests were to be conducted. After determining the life under CA loads as shown in Table 3, the number of cycles under low and high load of block loading were considered as 60% and 40% of the life for CAL condition with maximum stress equal to 4.0 kN and 4.5 kN respectively. Life for a particular loading condition was the average of the three tests performed under that test condition, Table 3. To assess the damage with EMI technique, the fatigue pre-cracked specimen with crack length of 12 mm was considered as the initial stage of the component and EMI signature was taken by the LCR meter. Thereafter, different loads as shown in Table 3 were applied and propagation of crack was observed with the help of a COD gauge. When crack propagated to a length of 13.5mm, 15.5mm, 18mm, 21mm and 24mm, then again EMI signatures were taken. From the EMI signatures, conductance versus frequency plots were drawn to determine the effect of different level of damage on the EMI signature.