PSI - Issue 71

Ajay Patel et al. / Procedia Structural Integrity 71 (2025) 196–202

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Using ANSYS software, a structural model of the mild steel coupon was created with dimensions and material characteristics identical to those of the actual specimen. The model uses the physical properties of mild steel. For mild steel, SOLID 45 elements were employed, whilst SOLID 5 elements were used for the PZT patch, allowing displacements for degrees of freedom in the x, y, and z directions, as well as an electrical degree of freedom in volts. As illustrated in Fig. 2, the boundary conditions encompassed fixed constraints on all the degrees of freedom from the rear side.

Fig. 2. Finite Element Model (FEM) of mild steel coupon with PZT patch integration To emulate the corrosion effects, the observed mass loss at 10-day intervals was represented by reducing the density in the ANSYS model. The FEM model incorporated density values corresponding to each mass-loss interval, reflecting the gradual degradation as per the actual experimental values. A piezoelectric ceramic transducer (PZT) patch, measuring 10 mm × 10 mm x 0.3 mm, id modelled to the center of the mild steel coupon in the FEM model to monitor damage due to corrosion. The characteristics of the PZT patch are derived from PI Ceramics (2010) and are also referenced in Moharana and Bhalla (2012). To conduct piezoelectric analysis, it is necessary to link the upper and lower nodes of the PZT patch using the "VOLT" degree of freedom. By executing a comprehensive harmonic analysis, the resulting output can be acquired as a reaction force (-Q), which is denoted as AMPS in the time history post-processor of ANSYS 17.0 (Patel et al. (2024)). To determine the current (I), one must consider the negative of the charge and differentiate the charge with respect to time, as follows in equation (5), (6) & (7): − = −( + ) (5) = ( − ) =( − ) (6) = ̄ = ( ) = −1 ( )= ( ) ( ) = + (7) The admittance consists of real and imaginary parts, as can be expressed as (Liang et al. (1994)) in equation (7). The admittance( Y ) value consists of two elements: conductance ( G ), which is the real component, and susceptance ( B ), which represents the imaginary part. Equation (7) provides the admittance value as the ratio of current and voltage. Using ANSYS 17.0, one can directly calculate the electric current for the admittance signature from the EMI technique (with ̅ = 1V), This approach eliminates the need to convert mechanical impedance into electrical admittance through the impedance-based electromechanical coupling equation (equations 1 & 2), which is typically required in FEA-based semi-analytical impedance models. 3. Results and Discussions: The admittance signatures were utilized to compare the outcomes of the FEM simulations, which depicted the structural response with a decreased density due to corrosion progress. To illustrate the progression of the damage,