Issue 67

A. Aabid et alii, Frattura ed Integrità Strutturale, 67 (2024) 137-152; DOI: 10.3221/IGF-ESIS.67.10

Levels

Factors

1

2

3

Actuator Thickness (mm)

0.5

0.75 954 0.03

1.0

Adhesive Shear Modulus (MPa)

882

1022 0.035

Adhesive Thickness (mm)

0.025

Table 5: Selected parameter variables

Taguchi’s L 9 orthogonal array Taguchi design (robust parameter design) suggested highly fractionated factorial designs and other orthogonal arrays along with some novel statistical methods to solve these types of problems [22]. If resources like cost and time are available, opting for an L 9 orthogonal array is advisable. This choice is advantageous because it allows for comprehensive testing of multiple parameters at various levels, including all three levels of other variables. On the other hand, if conducting a full factorial analysis entails significant costs and time investment, and problem-solving the accuracy of outcomes is not of utmost importance, then the application of the orthogonal Taguchi array method is recommended. The orthogonal array is typically used in industrial applications to investigate the impact of various control parameters. Additionally, the columns for the independent variables are orthogonal to one another in this form of study. To outline an orthogonal array, it's essential to establish distinct levels and constituents which can be seen in Tab. 6.

Runs

Coded Values

Response Output

A

B

C

S1 S2 S3 S4 S5 S6 S7 S8 S9

X1 X1 X1 X2 X2 X2 X3 X3 X3

X1 X2 X3 X1 X2 X3 X1 X2 X3

X1 X2 X3 X2 X3 X1 X3 X1 X2

Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Y9

Table 6: Taguchi’s L 9 orthogonal array.

F INITE ELEMENT RESULTS BASED ON THE T AGUCHI TABLE

he initial phase involved simulations utilizing Taguchi's orthogonal array, with a total of 9 simulations conducted on the repaired plate, maintaining a constant voltage of 150 V. This voltage choice aligns with previous findings by Abuzaid et al. [13], substantiating that a maximum voltage up to 150 V remains feasible and adaptable within aircraft maintenance. The study suggests that raising the voltage correlates with a reduced SIF (K), contributing to enhanced structural integrity. However, limitations in aircraft systems restrict voltage increase. As per existing research, the optimal selection revolves around the 150 V threshold, substantiating its suitability within the aircraft domain. From the Taguchi method, the computation of degrees of freedom (DOF) was conducted for three parameters within each of the three sets, encompassing multiple instances of level 1. A three-level L 9 orthogonal array comprising nine experimental trials was chosen. The overall DOF for the experiment amount to 8, calculated as 9 - 1. Total 9-DOF is the most suitable orthogonal array for simulation also known as L 9 array, and these values are selected in ascending order. Hence, the Taguchi orthogonal array is illustrated in Tab. 7. All the value of SIF (K) has been computed for the repaired plate whereas the value of the unrepaired plate is 0.1771 MPa √ m. Based on the results obtained for an orthogonal array the higher reduction of SIF was found at approximately 0.113663 MPa √ m which is approximately 36% of the reduction in repaired bonded PZT actuator effect. The DOE technique is the primary emphasis of the current work; hence the simulation is limited to the Taguchi design with an L 9 orthogonal array. This data was then utilized to optimize the SIF (K) for certain values and levels which can be seen in the next section of this paper. T

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