Stress Wave Propagation Velocity Model In Different Angles Longitudinal Section Of Standing Trees

This Paper will apply stress wave non-destructive testing technology to analyze trees in the longitudinal stress wave propagation.To build the velocity Model of Stress Wave in Longitudinal Section of wood;to learn more about Stress Wave Propagation in Longitudinal Direction of Trees and improve Nondestructive Testing Three-Dimensional Imaging Technology of Stress Wave wood.1.By the analysis of theory,we build the velocity Model of Stress Wave in Longitudinal Section of Wood and get the fitting result of the health sample test data is:V(θ,α)/V0≈kx2+1(0≤k≤1).The value of k depends on the size of the angle α between the longitudinal section and the radial section of the tree under test.By this result we can put forward the theoretical model to indicate the relation between the variety of the angle α and direction angle θ,with the propagation velocity of the internal stress wave.In the same longitudinal section;the stress wave propagation velocity increases with the increase of the direction angle θ;In different vertical sections;with the cross-section angle α increases,the stress wave change rate increases,the K value increases.By verifying the proposed theoretical model,we get the correlation coefficient R2 is greater than 0.93,which indicates that the proposed theoretical model has high accuracy.2.By analyze the changes of the propagation velocity of stress wave in different tree species and direction in the experiment;we verified the propagation velocity of stress wave in the standing tree is not affected by the impact intensity and the initial height.When the stress wave propagation path is located at the tree defect location,speed will be greatly reduced,no longer conforms to the proposed propagation model.Through the study of artificially made hollow defects,we can get the location and size of defects conveniently and accurately by measuring the longitudinal cross-sections from differentα angles.3.Based on the longitudinal stress wave propagation velocity model established in this paper,and the test of the decay,cracks and other defects in the sample,we get the experimental results that the obtained data not conform to the proposed propagation model.Therefore,it is practicability to adopt the propagation velocity model of the stress wave in the tree longitudinal section in this paper for the inspection of defects within the tree.