MODIFIED HOLE-DRILLING TECHNIQUE FOR DETERMINING RESIDUAL STRESSES (GROWTH STRESSES) IN TREE TRUNKS.

The primary advantage of the modification is that it can be applied to a standing tree. Two holes drilled above and below the strain measuring point release completely the strain in the longitudinal direction of a trunk. On the other hand, two holes drilled on both sides of the measuring point bring in a relaxation of the strain in the tangential direction of a trunk but, at the same time, create a new strain due to the diagonal stresses at above and below the holes. The occurrence of such new stresses can be avoided by drilling a number of holes at above and below the measuring point.