Crack defect identification in additively manufactured steel plate using frequency response function curvature method

Non-destructive vibration evaluations for detecting defects in additively manufactured parts have become a key research focus because they can identify flaws across an entire structure without targeting specific areas. Among different vibration-based techniques, one effective approach involves comparing the frequency response functions (FRFs) of healthy and defective parts to determine defect locations. Although vibration mode shapes are often used for this purpose, their application in additively manufactured components is complex, as small defects require high-frequency measurements and fine modal analysis. This study demonstrates that, by using the frequency response function curvature (FRFC) method, it is possible to detect even small defects at low frequencies, before the first resonance occurs. This characteristic provides a major practical advantage. To verify this, the researchers conducted modeling and numerical simulations on a thin plate with three cracks of varying depths and then performed experimental modal testing on a steel plate fabricated by selective laser melting, containing the same cracks. The results showed that, at low frequencies, the FRFC method accurately located cracks with 50%, 30%, and 10% damage intensities in simulations and achieved less than one percent error in experiments, confirming its precision and reliability for non-destructive evaluation.