0023-6152

AA00697606

9291

査読無

0023-6152

AA00697606

In the manufacture of glulam timbers, the laminae that have knots near the finger-joint and starved part in the finger-joint are often found, and it will greatly influence the decrease in strength of products. Therefore, the detection of knots and starved joints is important for preparation of laminae, and the method is hoped to be simple and non.destructive. In this study, sugi (Cryptomeria japonica D. Don) finger-jointed laminae with an intergrown knot near the finger-joint and starved joints in the finger-joint were prepared, and the evaluation of finger-joint performance was conducted by acoustic emission (AE) as the non-destructive method. That is, bending tests for these laminae were performed, and AE generated during bending test was measured along with load. Then, the correspondence between AE characteristics and the strength properties was examined. The main results are summarized as follows: for the laminae with a knot parallel to the finger-joint and starved joints in the finger-joints, AE signals were measured at the early stage of the bending test and the accumulated AE count was large as compared with the laminae without knots and starved joints/controls. Therefore, the AE technique is promising for the monitoring of knots and starved joints during bending test. In this experiment, for the laminae with a knot, the difference of the bending strength was not admitted. From this result, the bending strength was almost unaffected by the difference of the knot position near finger-joint. For the laminae with starved-joints, the MOE was almost unaffected by the presence of the starved joints, while the MOR decreased slightly as compared with the controls. It follows from the above results that the AE technique is promising for the detection of knot parallel to the finger-joint and starved joints in the finger-joint at the early stage of the bending test, even if the knot and starved joints do not cause much reduction in the bending strength.