A modal analysis-based nondestructive acoustic method for evaluating the elastic properties of solid structures

Accurate and nondestructive estimation of elastic properties is essential for material design and structural assessment. Conventional methods, such as mechanical testing, resonance ultrasound spectrometry, and impulse excitation technique, often require expensive equipment, precisely shaped specimens, and tightly controlled testing conditions. To avoid these rigid requirements, a natural frequency-informed finite element modal analysis (NF-FEMA) method was developed as a flexible and cost-effective alternative. This approach combines acoustic recordings of impulse-induced free vibrations with finite element simulations to inversely estimate elastic properties such as Young’s modulus, Poisson’s ratio, Bulk modulus, and Shear modulus. After successful validation on aluminum specimens with regular geometries, the method was extended to three diverse material types: 3-D-printed Nylon 11, irregularly shaped metal samples, and rock samples. Natural frequencies were extracted from recorded vibrations, and modal responses were simulated across a range of elastic property values. Best-fit parameters were identified by minimizing the difference between experimental and simulated frequencies. Results showed strong agreement with the ultrasound pulse velocity method, 2% for metals and around 8% for other samples, demonstrating the method’s accuracy and versatility. NF-FEMA offers a geometry-independent, low-cost solution for characterizing materials in additive manufacturing, geomechanics, and non-destructive testing.