Evaluation of finger-jointed laminae for glulam timber by acoustic emission, 2: Development of evaluation system for finger-jointed laminae with starved joints

In our previous studies, we paid attention to acoustic emission (AE) as a non-destructive method, and bending test for finger-jointed laminae with starved joints was performed. In addition, for installing the AE monitoring method into the production line of the finger-jointed laminae, a special attachment (jig) for the AE sensor installed into the production line was developed. However, this method with the jig was not efficient for the following two reasons; first, it is difficult to set the position of the jig. Secondly, it is necessary to stop the production line for the bending process. In this study, the new type jig which installed the AE sensor for the detection of the laminae with starved joints regardless of both the position and the number of finger-joint parts is designed, and the evaluation tests of finger-jointed laminae were conducted by using this jig. That is, the evaluation system which installed the jig was constructed, and hinoki (Chamaecyparis obtusa) finger-jointed laminae with starved joints were prepared, and the evaluation tests of finger-joint properties were conducted by using this system. The main results are summarized as follows: The evaluation system for the finger-jointed laminae was constructed. This system was composed of the motive power part, the AE measurement part, and the data collection part which controls some devices and collects sampling data. For the laminae with starved joints, the peak of AE signals which were measured by this system corresponded to the position of starved joints in the finger-jointed laminae. In addition, for the laminae with defects such as knots and loosed grains, the peak of AE signals which were measured besides the finger-joint part corresponded to the position of defects. From these results, this evaluation system which installed the jig with AE sensor was promising for detecting of the starved joints and the presence of defects in the finger-jointed laminae. It was found that modulus of elasticity (MOE) of the laminae during the evaluation test with this system could be measured in the grasp of the section size of the laminae beforehand. Therefore, it was suggested that the grading for the laminae after finger-jointed based on MOE could be possible by this system.