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Metal structures are widely used in modern industrial fields, but their manufacturing and service processes often produce composite defects that affect the mechanical properties and service life. Defects can appear both on the surface and beneath the structure, making it challenging for a single nondestructive testing (NDT) method to address all issues. Furthermore, using multiple NDT methods can result in low efficiency and high costs. To address this, a novel electromagnetic-acoustic integrated testing method, called PECT-EMAT, has been developed in this study, with its detection capability evaluated based on the theory of probability of detection (POD). Firstly, we established a simulation method and experimental system for PECT-EMAT to test aluminum alloy specimens with both surface cracks and bottom thinning defects, and explored a signal separation method using spectrum analysis. Next, we built a POD model based on statistical methods and created a signal database for composite defects. Finally, we conducted a statistical analysis of this database to determine the minimum detectable size of the PECT-EMAT hybrid testing method. The research findings indicate that: (1) For metal structures with both surface cracks and bottom thinning defects, the proposed PECT-EMAT method can effectively identify composite defects through signal separation. (2) The PECT signals and EMAT signals separated from the original detection signals exhibit distinct characteristics for detecting surface cracks and bottom thinning defects, respectively, leading to the establishment of a signal features' database for composite defects. (3) POD analysis reveals that the minimum detectable lengths for surface cracks are 2.72 mm in simulation and 2.12 mm in experiments, while for bottom thinning defects, they are 4.13 mm and 1.92 mm, respectively. This study provides a theoretical foundation for the adoption of the PECT-EMAT hybrid testing method and offers a reliable technical means for detecting complex defects in engineering structures.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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