Analysis of Vibration Modal Testing for the Full-size Artificial Board

Abstract

The vibration method is one of the most effective methods for nondestructively testing the elasticity modulus of wood. But the past research was mostly concentrated in the small size specimens. In order to better prepare for the nondestructive testing of the elasticity modulus of full-size artificial board, here tests and analyzes its vibration modal. In order to solve the modal parameters of full-size artificial board in free vibration, it uses 6 full-scale artificial boards of two kinds of materials, and for each kind there are 3 kinds of thicknesses, in which including the particle board and medium density fiberboard as the test objects. Then it props them at the first order pitch line of free vibration, namely the 22.4% and 77.6% of the full-length of the full-size artificial board. After exciting by the pulse hammer and vibration picking by the acceleration sensor, it can measure the vibration mode, the vibration frequency and the damping ratio of the full-size artificial boards at each order. It obtains the vibration mode, the frequency and the damping ratio of the full-size artificial board at the first 3 orders in the free vibration form. The results show that: 1) for the three materials of full-size artificial boards with all thicknesses, their vibration modes at the first order are bending along with the length direction; 2) the vibration modes of the full-size artificial boards with the same thickness are the same at the same order, and are all bending vibration.