Research On Influential Factors Of Stress Wave Propagation In The Wood

In the past decades, the forest resources in our country have been felled excessively, while thesocial demand is far beyond the growth in the forest resource. So the great shortfall between woodsupply and demand makes the research on timbers utilization very important. The woodnondestructive testing (NDT) technology has been popular increasingly, and the standing trees andtimbers can be evaluated nondestructively to decide whether there is internal defect, so that thewaste of wood resources can be prevented and the resources can be saved indirectly.In this paper, a series of experiments were carried out to study the influence on the stresswave velocity in wood caused by different factors, such as the holes and cracks, the seasons andtemperatures, as well as the species of the trees. The experimental results were analyzed andstudied. The main contributions are given as follows.1. The distribution rule of the stress wave velocity in chinaberry disk was studied in cases ofdifferent size of holes and cracks, and the regression equations were obtained.2. The stress wave velocities in the camphor tree in different seasons were collected. Theexperimental results show that the stress wave velocity is the highest speed in winter, and it is thelowest in summer.3. The experiments for the cedar disk under different temperatures were finished. The resultsdemonstrate that the stress wave velocity reduces gradually with the rise of temperatures. Thecorresponding quadratic regression equation was derived.4. Seven species (cryptomeria, cypress, cedar, java bishopwood, gingko, tulipwood, andsweetgum) were classified to two kinds (the coniferous or broadleaf), and some experiments werecarried out. The influence on the stress wave velocity by the species was analyzed, and theregression equation of each species was generated.In conclusion, the influence on the stress wave velocity in wood under different factors wasanalyzed. With the established polynomial fitted model, we can get the predicted value of thestress wave velocity in wood, which can be used as the basic reference data in the nondestructivetesting of wood.