Research On The Application Of Non-Destructive Evaluation Techniques Used In The Maintenance Of Ancient Wood Members

The application of stress wave, ultrasonic wave and pilodyn non-destructive evaluation techniques used in the maintenance of ancient wood members was researched with some healthy woods obtained from Tibet and northeast China, some woods treated by CCA wood preservative and some ancient wood members replaced from the Potala Palace and Norbu Linka aged timber buildings as testing specimens. The purpose was material-state-exploration of aged timber buildings under the prerequisite of not destroy the connect form and mechanical state of the original wood structures and grasping the laws of physical and mechanical attenuation. Thus the safety assessment of ancient wood members would change from traditional eye-distinguish to non-destructive evaluation and quantitatively scientific evaluation, which would offer theoretical foundations for formulating maintenance scheme of the aged timber building at the same time.The main research conclusions were summarized as following:1. The stress wave transit speeds of Sea Buckthorn, Poplar, Cypress and Larch woods obtained from Tibet and Larch, Korean Pine and Mongolian Scotch Pine woods obtained from northeast China, the ultrasonic wave transit speeds of Sea Buckthorn and Poplar woods obtained from Tibet and the relative surface hardness expressed by pilodyn penetration depth of Sea Buckthorn, Poplar and Larch woods obtained from Tibet and Larch, Korean Pine and Mongolian Scotch Pine woods obtained from northeast China were got through the non-destructive evaluation of healthy woods.2. The dynamic modulus of elasticity (MOE) could be easily and conveniently got through the testing of stress wave and ultrasonic wave speeds of woods. The non-destructive evaluation results of woods treated by CCA wood preservative indicated that the dynamic MOE of Sea Buckthorn had no significant difference before and after CCA treatment and the dynamic MOE of Larch woods treated by different methods with CCA wood preservative also had no prominent difference. This meant that CCA treatment had not notably effects on the physical and mechanical properties of woods and the stress wave and ultrasonic wave non-destructive evaluation techniques used for assessing the dynamic MOE of CCA treated woods were completely feasible.3. Through the stress wave non-destructive evaluation of the ancient wood members replaced from Potala Palace and Norbu Linka aged timber buildings, the conclusions that the majority of ancient wood members contained various degree internal decay and insect-damage state besides the prominent surface decay and insect-damage. Comparative analysis with the visual classification indicated that ancient wood members could be divided into two cases, one was the evaluation results by two methods were consistent with each other, and the other one was opposite with each other. Compared with visual classification, stress wave non-destructive evaluation techniques could find the internal decay and insect-damage to eliminate the hidden hazard for ancient wood members, and offer relatively accurate quantitative information for the safety status. This was particularly important for the aged timber buildings.4. With the virtue of fast, conveniently and easily to operate, pilodyn non-destructive evaluation techniques could get live results and offer comparatively accurate information for the extent of internal decay and insect-damage of the ancient wood members. So the pilodyn instrument used for material state exploration of aged timber buildings was feasible. But the maximum measurement range of it was only 40mm, which limited its more extensive use to a certain extent, and the completion of pilodyn was expected.