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Combining the resonance method and the direct wave extracting method, the dynamic mechanical parameters of viscoelastic materials in a continuous and wide frequency range under controllable water pressure were measured. A pressure chamber test system capable of realizing underwater pressurization was built, a short time broadband impulse generated by an electromagnetic shaker was employed to excite a bar-like sample attached inside the pressure vessel. On one hand, the resonance method was used to calculate the mechanical parameters at resonance frequencies while on the other hand, the direct wave signal was extracted, and the mechanical parameters in a wide frequency range were calculated by the wave velocity method. The broadband mechanical parameters (including the storage modulus and loss factor) under variable water pressure conditions (0.1-6 MPa) for two types of viscoelastic materials were obtained. The experimental results agree well with each other, proving the test method in this paper could directly determine the Young’s modulus at frequencies ranging from 500 Hz to 5000 Hz under variable water pressure. This method provides simplified processing for underwater dynamic mechanical parameter measurements.
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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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