In end-jointing of laminae for the glulam timber, finger-joint is generally used. However, the strength properties of the glulam timber greatly decrease by slippage-off and destruction in starved joints of fingerjointed part when the laminae with starved joints in the finger-joint are located on the external layer of the glulam timber. Therefore, for the 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 this study, hinoki (Chamaecyparis obtua) finger-jointed laminae with starved joints (NH-laminae) and without starved joints (C-laminae) were prepared, respectively. The evaluation of finger-joint properties with a special attachment (jig) for installing the acoustic emission (AE) monitoring method into the production line of the laminae was conducted. That is, bending tests for these laminae with the jig were performed, and AE generated during the bending test was measured along with the load. Then, AE characteristics and bending strength properties of these laminae were examined. In addition, the verification test with the jig was performed. The main results are summarized as follows: AE signals of NH-laminae in the threshold of 20 mV were measured at the early stage in bending test as compared with C-laminae. The AE generation load of NH-laminae showed a small value and showed the smallest value in 20 mV. From these results, it became clear that AE technique with the jig in the threshold of 20 mV will be promising for the detection of the difference between C-and NH-laminae at the early stage during bending test. From the obtained result of the verification test with the jig under the conditions of the load:4 kN and the threshold:20 mV for the detection of the starved joints, it became clear that NH-laminae could be detected at the probability of about 70% under these conditions. Therefore, in the case of loading to the finger-jointed part of laminae in 4 kN as the detection load with the jig, the possibility of the detection of the starved joints by AE as a non-destructive method was suggested.
|Number of pages||4|
|Journal||Journal of the Faculty of Agriculture, Kyushu University|
|Publication status||Published - Oct 2009|
All Science Journal Classification (ASJC) codes
- Agronomy and Crop Science