Evaluation of Finger-jointed Laminae for Glulam Timber by Acousitic Emission II Development of Evaluation System for Finger-jointed Laminae with Starved Joints

Abstract

The laminae that comprise glulam timber are generally finger–jointed. However, laminae with starved joints in the finger–joint are occasionally found in the manufacture of glulam timber, and greatly decrease the timbers’ strength. Therefore, for the manufacture of glulam timber with good strength properties, the evaluation of finger–joint properties after finger–jointing is important, and the method is hoped to be simple and non–destructive. In our previous studies, we paid attention to acoustic emission (AE) as a non–destructive method, and bending test for finger–joint laminae with starved joints was performed. We clarified that AE generated during the bending test was promising for the detection of starved joints in the finger–joint at the early stage of the bending test. In addition, it became clear that the position of starved joints in finger–joint could be presumed by one– dimensional method of using AE signal (Ohuchi et al., 2004: Yano et al., 2007). Furthermore, in consideration of installing the AE monitoring method into the production line of the finger–joint laminae, a special attachment (jig) for the AE sensor installed into the production line was developed. From the result of verification test with the jig, it was clear that the possibility of the detection of the starved joints by AE as a non–destructive method was suggested in the case of loading to the finger–jointed part of laminae in 4 kN as the detection load with the jig (Ohuchi et al., 2009). However, it was pointed out that this method with the jig was not efficient for the following two reasons; first, it is difficult to set the position of the jig beforehand because neither the position nor the number of finger–joint parts in the laminae is decided. Secondly, it is necessary to stop the production line for the bending process. In this study, the main objective was to develop the evaluation method for detecting of the laminae with starved joints without stopping the production line regardless of both the position and the number of finger– joint parts in the laminae. In this report, the new type attachment (jig) which installed the AE sensor as non– destructive method for the detection of the laminae with starved joints is designed, and the evaluation tests of finger–jointed laminae were conducted by using this jig. That is, the evaluation system which installed the new Evaluation of Finger–jointed Laminae for Glulam Timber by Acoustic Emission II Development of Evaluation System for Finger–jointed Laminae with Starved Joints