Development of Dynamic Portable Graders for Structural Lumber Using Tapping Method

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The object of this project was directed to the development of the portable dynamic graders which are used for the non-destructive strength evaluation of structural lumber.1. The following systems were developed : (1) An automated high-speed system which was composed of an Fast Fourier Transformation (FFT) spectrum analyzer and a 16-bit personal computer, (2) A pocket Young's-modulus tester which was composed of a counter LSI and logic ICs, (3) An automated system which was composed of a 16-bit personal computer and a commercial A/D converter board, and (4) A system which was composed of a pocket computer and a commercial A/D converter board.2. In situ application test of the automated system : The automated system using a FFT spectrum analyzer was transported to lumber mills and a forest-side log yard in order to examine the applicability and to obtain the data on the physical parameters of 2X4 lumber (S-P-F) and structural lumber of sugi and hinoki for the traditional Japanese wooden house. The maximum measuring speed was 100 pieces of lumber per an hour in the case of structural lumber. The rate-determining step of the measurement was the changing of specimens by human handling. In the case of logs, the weight measurement should be improved.3. Numerical analysis of the flexural vibration theory of tapered beam was made to adopt the flexural vibration technique to logs by using the transfer matrix method. The results made the application of the vibration theory of the beam with homogeneous cross-section possible.4. Knowledge base of the physical properties of structural timbers which was stored during in situ test was use to examine the algorism of the non-destructive strength prediction of structural timber. MOE prediction by the resonance frequency and the multiple regression model were studied.