Vacuum thermal-insulation material, and a device and method for assessing the degree of vacuum in the vacuum insulation material by using the frequency response method
Disclosed herein is a vacuum insulation material, which includes a barrier film and a core, wherein a rigid body thinner than a reference thickness or a getter harder than a reference hardness is formed between the barrier film and the core, or the rigid body thinner than the reference thickness is formed on the getter formed between the barrier film and the core to ensure surface flatness and surface hardness of the vacuum insulation material.
1. A vacuum insulation material comprising:
a barrier film; and
a core, wherein a rigid body thinner than a reference thickness and a getter harder than a reference hardness are formed between the barrier film and the core, and the rigid body is formed on the getter to ensure surface flatness and surface hardness of the vacuum insulation material, wherein the reference thickness ranges from 0.5 mm to 1.5 mm, and reference hardness ranges from 2H to 4H.
2. An apparatus for evaluating an internal vacuum degree of a vacuum insulation material, comprising:
a hammer unit which applies impact to a portion of a surface of the vacuum insulation material corresponding to a rigid body or a getter in the vacuum insulation material to excite the vacuum insulation material according to claim 1 ;
a displacement measuring unit which measures displacement of a material point according to the impact applied to the vacuum insulation material;
a frequency analysis unit which measures a natural frequency of the vacuum insulation material based on the measured displacement; and
a vacuum evaluation unit which evaluates the internal vacuum degree of the vacuum insulation material based on the natural frequency.
3. The apparatus according to claim 2 , wherein the frequency analysis unit processes the measured displacement via Fourier Transform to obtain a frequency spectrum and analyzes the frequency spectrum to measure the natural frequency of the vacuum insulation material.
4. The apparatus according to claim 2 , wherein the vacuum evaluation unit compares the natural frequency measured by the frequency analysis unit with the reference frequency to evaluate the internal vacuum degree of the vacuum insulation material.
5. The apparatus according to claim 4 , wherein the reference frequency is an average value of natural frequencies of normal vacuum insulation materials according to size and weight and is within a predetermined reference frequency range.
6. The apparatus according to claim 4 , wherein, when the measured natural frequency deviates from the reference frequency range, the vacuum evaluation unit determines that the internal vacuum degree of the vacuum insulation material is poor, and when the measured natural frequency is within the reference frequency range, the vacuum evaluation unit determines that the internal vacuum degree of the vacuum insulation material is good.
7. The apparatus according to claim 2 , further comprising:
a force sensor for measuring a magnitude of force transferred to the vacuum insulation material as the hammer unit strikes the vacuum insulation material, wherein the frequency analysis unit converts the measured displacement to a mechanical compliance value according to an equation regarding a relationship between the displacement and the force, and analyzes the converted mechanical compliance value in a frequency region to measure the natural frequency of the vacuum insulation material.
8. The apparatus according to claim 2 , wherein the displacement measuring unit comprises a laser displacement sensor which measures the displacement while being separated a predetermined distance from the vacuum insulation material.
9. A method of evaluating an internal vacuum degree of a vacuum insulation material, comprising:
applying impact to a portion of a surface of the vacuum insulation material according to claim 1 corresponding to a rigid body or a getter in the vacuum insulation material;
measuring displacement of a material point according to the impact applied to the vacuum insulation material;
measuring a natural frequency of the vacuum insulation material based on the measured displacement; and
evaluating an internal vacuum degree of the vacuum insulation material based on the natural frequency.
10. The method according to claim 9 , wherein the measuring a natural frequency of the vacuum insulation material comprises:
processing the measured displacement via Fourier Transform to obtain a frequency spectrum; and
analyzing the frequency spectrum to measure the natural frequency of the vacuum insulation material.
11. The method according to claim 9 , wherein the evaluating an internal vacuum degree of the vacuum insulation material comprises:
determining that the internal vacuum degree of the vacuum insulation material is poor when the measured natural frequency deviates from a reference frequency range; and
determining that the internal vacuum degree of the vacuum insulation material is good when the measured natural frequency is within the reference frequency range.
12. The method according to claim 9 , further comprising:
measuring a magnitude of force transferred to the vacuum insulation material as the hammer unit strikes the vacuum insulation material;
converting the measured displacement into a mechanical compliance value according to an equation regarding a relationship between the displacement and the force; and
analyzing the converted mechanical compliance value in a frequency region to measure the natural frequency of the vacuum insulation material.
13. The method according to claim 9 , wherein the measuring displacement of a material point comprises measuring the displacement of the material point using a laser displacement sensor separated a predetermined distance from the vacuum insulation material.