Study on Measurement of Material Properties for Platy Specimen with Impulse Excitation Technique
| Autor: | Ching-lung, Lee, 李青隆 |
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| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 This study used the Impulse Excitation Technique (IET) and numerical analysis to explore the dynamic moduli of platy specimens. When the specimens was hit by the impactor of steel ball, the resulting vibration produced the time-domain sound wave and the resonant frequencies were obtained by the Fast Fourier Transform (FFT) to calculate the experimental values of dynamic modulus Together with the results from numerical simulation, the appropriate dimension of platy specimen for testing and the feasibility of application to the heterogeneous material were addressed. The experimental procedures started with numerical analysis of metal material with different aspect ratios to study the changes of resonance frequency and mode shape, then the IET method was used to test the dynamic modulus with non-contact receiver of microphone and contact receivers of accelerometer to detect nine kinds of different dimensions of metal material. Then both the cement mortar and fly ash cement mortar specimens were made to investigate the evolution of dynamic modulus using resonance frequency method, strength development and variations of unit weight. Afterward, the feasibility of application of the IET technique to the porous platy material. The research results show that:(1) Numerical analysis can obtain the resonance frequency and mode shape to justify the frequency from the experimental results to be the flexural frequency or the torsional frequency;(2) When the aspect ratio of 1:1, the errors of dynamic elastic modulus from the numerical analysis with two mode shape of flexural frequency were -70% and 150%;(3) When the aspect ratios between 2:1 and 4:3, errors of dynamic elastic modulus from the numerical analysis were less than 1%; (4) When the aspect ratio of 1:1, the error of dynamic elastic modulus from the IET tested was higher than 60%, which shows that the IET is not suitable for square plate specimen; (5) When the aspect ratio of 2:1, the thickness ratio of 0.3、0.4、0.5， error of dynamic elastic modulus from the IET tested were 0.8%、1.2%、1.5%, respectively, which shows that the IET is suitable with thinner specimen; (6) The difference of dynamic elastic modulus and dynamic shear modulus was less than 1% when the wave results were received by either the microphone or the accelerometer; (7) Both the cement mortar specimen and cement fly ash mortar at age of 28days were tested by the IET and the resonance frequency method, the results show that the differences of both methods of dynamic elastic modulus and dynamic shear modulus were less than 1%, which shows that the IET method can be applied to nonhomogeneous materials like cement-based material. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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