Method and device for evaluating a wooden board

1. A method for evaluating a wooden board, the method comprising:

acquiring data indicating fiber orientation for a surface of the wooden board;

for each of a plurality of board sub-portions, determining a respective nominal local modulus of elasticity (MOE) associated with an elongated direction of the wooden board based on the fiber orientation and nominal material parameters E l , E r , E t , G lr , G lt , G rt , v lr , v lt , and v rt , wherein the parameters E l , E r , E t indicate a moduli of elasticity in orthotropic directions of the wooden board, the parameters G lr , G lt , and G rt indicate a shear moduli in respective orthotropic planes of the wooden board, and the parameters v lr , v lt , and v rt are Poisson's ratios;

generating a nominal global MOE associated with the elongated direction of the wooden board based on the determined nominal local MOEs;

determining a secondary global MOE for the wooden board by exciting the wooden board with an impact in a longitudinal direction of the wooden board and measuring a primary resonance frequency of the wooden board;

comparing the nominal global MOE with the secondary global MOE; and

for each of the plurality of board sub-portions, determining a respective estimated local MOE associated with the elongated direction of the wooden board based on the fiber orientation and the comparison of the nominal global MOE with the secondary global MOE.

2. The method according to claim 1 , wherein the data indicating fiber orientation over the surface of the wooden board is acquired using an optical scanner.

3. The method according to claim 1 , wherein determining the respective nominal local MOE associated with the elongated direction of the wooden board for a given board sub-portion is performed based on an assumption that a volume of wood beneath the surface of the given board sub-portion has the same fiber orientation as the surface of the given board sub-portion.

4. The method according to claim 1 , wherein the plurality of respective estimated local MOEs are used to determine a strength grade for the wooden board.

5. The method according to claim 4 , wherein the strength grade is further based on an indicating property (IP).

6. The method according to claim 5 , wherein the IP is based on a calculated bending stiffness in a number of cross sections along a length of the wooden board, and a minimum cross section bending stiffness is used as a basis for the IP.

7. The method according to claim 5 , wherein the IP is based on a calculated axial stiffness in a number of cross sections along a length of the wooden board, and a minimum cross section axial stiffness being used as a basis for the IP.

8. The method according to claim 1 , wherein the plurality of respective estimated local MOEs are used to determine a bending or an axial stiffness of the wooden board across a plurality of cross sections of a length of the wooden board.

9. A device comprising:

a scanner configured to acquire data indicating fiber orientation for a surface of a wooden board; and

a processing unit configured to:

determine, for each of a plurality of board sub-portions, a respective nominal local modulus of elasticity (MOE) associated with an elongated direction of the wooden board based on the fiber orientation and nominal material parameters E l , E r , E t , G lr , G lt , G rt , v lr , v lt , and v rt wherein the parameters E t , E r , E t indicate a moduli of elasticity in orthotropic directions of the wooden board, the parameters G lr , G lt , and G rt indicate a shear moduli in respective orthotropic planes of the wooden board, and the parameters v lr , v lt , and v rt are Poisson's ratios, and

generate a nominal global MOE associated with the elongated direction of the wooden board based on the determined nominal local MOEs; and

a resonance frequency sensing unit configured to:

determine a secondary global MOE for the wooden board by exciting the wooden board with an impact in a longitudinal direction of the wooden board, and

measure a primary resonance frequency of the wooden board,

wherein the processing unit is further configured to compare the nominal global MOE with the secondary global MOE, and

wherein the processing unit is further configured to determine, for each of the plurality of board sub-portions, a respective estimated local MOE associated with the elongated direction of the wooden board based on the fiber orientation and the comparison of the nominal global MOE with the secondary global MOE.

10. The device according to claim 9 , wherein the processing unit is further configured to determine a strength grade for the wooden board based on the plurality of respective estimated local MOEs.

11. The device according to claim 10 , wherein the strength grade is further based on an indicating property (IP).

12. The device according to claim 11 , wherein the IP is based on a calculated bending stiffness in a number of cross sections along a length of the wooden board, and a minimum cross section bending stiffness is used as a basis for the IP.

13. The device according to claim 9 , wherein the processing unit is configured to determine the respective nominal local MOE associated with the elongated direction of the wooden board for a given board sub-portion based on an assumption that a volume of wood beneath the surface of the given board sub-portion has the same fiber orientation as the surface of the given board sub-portion.

14. A method comprising:

acquiring data indicating fiber orientation for a surface of a wooden board;

for each of a plurality of board sub-portions, determining a respective estimated nominal local modulus of elasticity (MOE) associated with an elongated direction of the wooden board based on the fiber orientation and nominal material parameters E l , E r , E t , G lr , G lt , G rt , v lr , v lt , and v rt , wherein the parameters E l , E r , E t indicate a moduli of elasticity in orthotropic directions of the wooden board, the parameters G lr , G lt , and G rt indicate a shear moduli in respective orthotropic planes of the wooden board, and the parameters v lr , v lt , and v rt are Poisson's ratios;

generating a nominal global MOE associated with the elongated direction of the wooden board based on the determined nominal local MOEs;

determining a secondary global MOE for the wooden board by exciting the wooden board with an impact in a longitudinal direction of the wooden board and measuring a primary resonance frequency of the wooden board after excitation; and

for each of the plurality of board sub-portions, determining a respective estimated local MOE associated with the elongated direction of the wooden board based on the fiber orientation, the nominal global MOE, and the secondary global MOE.

15. The method according to claim 14 , further comprising:

comparing the nominal global MOE with the secondary global MOE.

16. The method according to claim 15 , wherein determining the respective estimated local MOEs for each of the plurality of board sub-portions is based on the comparison of the nominal global MOE with the secondary global MOE.

17. The method according to claim 14 , wherein determining the respective nominal local MOE associated with the elongated direction of the wooden board for a given board sub-portion is performed based on an assumption that a volume of wood beneath the surface of the given board sub-portion has the same fiber orientation as the surface of the given board sub-portion.