Apparatus and method for detecting defect of press panel

1. An apparatus for detecting a defect of a press panel, the apparatus comprising:

an acoustic emission sensor unit configured to detect at least one elastic wave signal emitted from the press panel as a detection target during press work;

a period measurer configured to measure a period as a section in which there are consecutive signals with a greater voltage than a threshold voltage among the at least one detected signals; and

a defect existence determination unit configured to determine that a defect is generated in the press panel when the measured period is greater than a first reference value and to determine that the press panel is in a normal state when the measured period is smaller than a second reference value which is smaller than the first reference value.

2. The apparatus of claim 1 , wherein:

the first reference value and the second reference value are determined using a period value pre-measured from a plurality of press panels as a comparison target, and

the first reference value and the second reference value refer to a value of a boundary line on distribution of a period of a press panel in which a defect is generated from the comparison target and a period of a press panel in a normal state from the comparison target.

3. The apparatus of claim 1 , further comprising:

an extractor configured to extract from the at least one detected signals: i) at least one parameter among the number of pulses with a greater output voltage than the threshold voltage, ii) energy as the sum of areas of pulses with a greater output voltage than a threshold voltage, and iii) an average frequency generated during the period.

4. The apparatus of claim 3 , wherein:

the defect existence determination unit is further configured to determine whether the press panel is defective using the at least one extracted parameter when the measured period has a value between the first reference value and the second reference value.

5. The apparatus of claim 4 , wherein:

the defect existence determination unit is further configured to:

determine that a defect is generated in a corresponding press panel when the number of pulses and the energy are higher than a reference number among the extracted parameter, and

determine that a defect is generated in the corresponding press panel when the average frequency generated during the period is lower than a reference number.

6. A method for detecting a defect using a press panel defect detection apparatus, the method comprising:

detecting at least one elastic wave signal emitted from the press panel as a detection target during press work;

measuring a period as a section in which there are consecutive signals with a greater voltage than a threshold voltage among the at least one detected signals;

determining that a defect is generated in the press panel when the measured period is greater than a first reference value; and

determining that the press panel is in a normal state when the measured period is smaller than a second reference value which is smaller than the first reference value.

7. The method of claim 6 , wherein:

the first reference value and the second reference value are determined using a period value pre-measured from a plurality of press panels as a comparison target, and

the first reference value and the second reference value refer to a value of a boundary line on distribution of a period of a press panel in which a defect is generated from the comparison target and a period of a press panel in a normal state from the comparison target.

8. The method of claim 6 , further comprising:

extracting from the at least one detected signal: i) at least one parameter among the number of pulses with a greater output voltage than the threshold voltage, ii) energy as the sum of areas of pulses with a greater output voltage than a threshold voltage, and iii) an average frequency generated during the period.

9. The method of claim 8 , wherein the determining that the defect is generated comprises:

determining whether the press panel is defective using the at least one extracted parameter when the measured period has a value between the first reference value and the second reference value.

10. The method of claim 9 , wherein the determining that the defect is generated further comprises:

determining that a defect is generated in a corresponding press panel when the number of pulses and the energy are higher than a reference number among the extracted parameter; and

determining that a defect is generated in the corresponding press panel when the average frequency generated during the period is lower than a reference number.

11. A non-transitory computer readable medium containing program instructions for detecting a defect of a press panel, the computer readable medium comprising:

program instructions that measure a period as a section in which there are consecutive signals with a greater voltage than a threshold voltage among at least one elastic wave signal emitted from the press panel detected as a detection target during press work;

program instructions that determine that a defect is generated in the press panel when the measured period is greater than a first reference value; and

program instructions that determine that the press panel is in a normal state when the measured period is smaller than a second reference value which is smaller than the first reference value.