A comparison of deconvolution techniques to improve MOR estimation from stress grading machine output

Summary Both time and frequency domain techniques to calculate lengthwise local MOE variation in timber, from stress grading machine output, have been examined. Three variants of a frequency domain method were selected for further evaluation with the objective of improving the timber stress grading process. MOR-local MOE correlation coefficients have been obtained by each method for over 50 structural timber specimens. These showed that due to the ill-conditioned nature of the deconvolution process and the inability to differentiate between noise and defect detail, only marginal improvements were possible over the existing technique that uses apparent MOE values calculated directly from suitably filtered machine load readings.This work was supported from contracts EMC 132/88 and EMC 3/91 awarded by the Building Research Establishment, Garston, Watford WD2 7JR.Appreciation is also expressed to R. O. Foschi and F. Lam (University of British Columbia, Canada) who supplied, through A. R. Fewell (Building Research Establishment, U.K.), Fortran routines of development versions of their methods