Wooden Board Strength Grading via Fiber Orientation and Resonance
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Solution Overview
Problem
Existing methods for evaluating wooden boards lack precision in determining local modulus of elasticity and strength grading, particularly in accounting for variations in fiber orientation and board location within a log, leading to uncertainty in predicting bending strength and stiffness.
Innovation Solution
A method that acquires fiber orientation data over the board's surface using a laser scanner, determines nominal and secondary global modulus of elasticity by measuring resonance frequency, and adjusts local modulus of elasticity based on fiber angle and material parameters to provide a more reliable estimate, enabling improved strength grading through calculated bending or axial stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fiber orientation data is acquired and used to determine local modulus of elasticity, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple evaluation methods (fiber orientation measurement, resonance frequency measurement, and mechanical property calculation) into a unified evaluation system. The fiber orientation data from the laser scanner is merged with resonance frequency data and material parameters to calculate local modulus of elasticity, creating a comprehensive evaluation approach that improves precision while managing complexity through integration.
Solution Approach 2:
The patent uses fiber orientation data as an intermediary to bridge the gap between surface measurements and internal mechanical properties. By measuring fiber orientation at the surface and using it to infer local modulus of elasticity through calculations involving material parameters, the system indirectly determines properties that would be difficult to measure directly, thus improving measurement precision without requiring complex internal sensing.
2Measurement precision
If local modulus of elasticity is determined for each board sub-portion, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary determination of fiber orientation data across the entire board surface before conducting the local modulus of elasticity calculations. By acquiring all necessary fiber orientation measurements in advance and storing them for subsequent processing, the system prepares the data foundation beforehand, which streamlines the actual evaluation process and reduces the time required for detailed local analysis.
Solution Approach 2:
The patent divides the board into multiple sub-portions and determines the local modulus of elasticity for each segment independently. This segmentation allows the evaluation process to be broken down into manageable units that can be processed efficiently, with each sub-portion evaluated based on its specific fiber orientation characteristics, thereby improving overall measurement precision through localized analysis.
3Reliability
If fiber orientation data is used to adjust local modulus of elasticity, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent uses fiber orientation data to dynamically adjust the local modulus of elasticity values from nominal material parameters. By changing the elasticity parameters based on actual measured fiber angles at each location, the system adapts the mechanical property predictions to reflect real board conditions, significantly improving reliability and accuracy of strength grading while using computational rather than hardware complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a substantially more reliable evaluation of wooden boards, allowing for more accurate strength grading and increased classification into higher strength classes while meeting industry standards, with a coefficient of determination of 0.68 between bending strength and minimum cross-section stiffness.
Implementation Method 1
acquiring data indicating fiber orientation over the surface of the board using a laser scanner
Implementation Method 2
obtaining a secondary global modulus of elasticity, MOE, for the board by exciting the board with an impact in its longitudinal direction and measuring its primary resonance frequency
Data Source
AI summary
The present disclosure relates to a method and device for evaluating a wooden board with an elongated direction. Data indicating fiber orientation over the surface of the board is acquired and for a number of board sub- portions a nominal local modulus of elasticity, MOE, is determined based on the fiber orientation data and a nominal material parameter. A nominal global MOE in the elongated direction for the wooden board as a whole is generated and compared with a secondary global MOE. Based on the fiber orientation data and this comparison an estimated local modulus of elasticity, MOE, in said elongated direction is generated for a number of board sub-portions. This data may be used e.g. for reliable strength grading of wooden boards.