Abstract:The primary purpose was to investigate the influence factors on stress wave propagation in larch standing trees and pave a foundation for further study on the propagation mechanism of stress wave in standing trees. Standing trees were considered to be a twolayers material only consisted of heartwood and sapwood, and the propagation of stress wave in standing trees was simulated. The effect of loading impulse frequency, diameter at breast height (DBH) and ratio of heartwood on stress wave propagation in standing trees were studied by using COMSOL Multiphysics finite element analysis software based on stress wave propagation theory in the solid medium and orthotropic assumption of standing trees. It was found that the velocity of stress wave in standing trees was decreased with the increase of impulse frequency; for a tree model with 10cm DBH, the wave front of stress wave was changed into onedimensional plane wave as the propagation distance was increased to 12m, however, the stress wave still propagated as threedimensional dilatational wave for a tree model with DBH over 30cm though the propagation distance was increased to 12m; DBH had an influence on the propagation speed of stress wave, wave velocity was firstly small and almost no change as DBH was less than 10cm, and then it was increased when DBH was changed from 10cm to 40cm, finally, slightly increased and remained relatively stable as DBH was over 40cm; the velocity of stress wave in standing trees was decreased with the increase of ratio of heartwood. DBH had an impact on the propagation patterns and shapes of stress waves in standing trees, however, the impulse frequency and the ratio of heartwood had no effect on the propagation patterns and shapes of stress. But all of them had an influence on wave propagation velocity. The optimal loading impulse frequency was 25kHz. The propagation velocity of stress wave in standing trees was not only depended on the mechanical properties of sapwood, but in fact relied on both heartwood and sapwood.
