Use of the Acoustic Grading Method as Nondestructive Inspection to Measure the Elastic Modulus of Timbers for Experimental Education in Engineering

The quality assurance of architectural timbers becomes more important because the Building Standard Law was revised in 2000 and the House Quality Assurance Law was enforced. There are two indices to timber strength. One is 'Young's modulus' as the index at an initial deformation, and the other is 'ultimate strength' as the index of failure. Recently, the Young's modulus can be measured by the Acoustic Grading Method. This is one of the so-called nondestructive inspection methods, which is to measure the sound while beating the timber side, and detect predominant frequency using FFT (Fast Fourier Transform) analysis. The Young's modulus obtained by the Acoustic Grading Method is compared with the moduli detected by the axial compression and flexural failure tests of the timbers.