Study On Impulse Stress Wave Technology To Check Ancient Wood Components In Defects

AbstractARBOTOM impulse stress wave technology were used as main approach of testing in this paper, and the research objectives were obtained from demolished ancient wooden in Forbidden City which suffered decay,hollow,crack and so on.In the aim of provide some scientific basis and technology for detection of wood components of ancient building using impulse stress wave technology on the spot.the content of the testing including the research using impulse stress wave to detect and assess different kinds of defects of ancient wood and healthy wood members,the influence factors research of stress wave technology to test wood component,the relationship between the test results of impulse stress wave technology and the wood physical and mechanical properties.The main research conclusions were summarized as follow:1.It is efficient to improve the effect by using impulse stress wave technology,and it could easy to tell the difference between healthy wood and bad wood(such as decay,crack and so on).What's more, the result of it could reflect the internal defects of wood.2.The basic position,general shape,basic size compare to the cross section of internal defects of wood could be well detected through two-dimensional testing.And the hollow,decay,local bundle of pillar are except difficult to distinguish,should be further tested by using other instruments.3.Three-dimensional stress wave technology are more effective,and it is easy to estimate the trend and development of defect,what's more,the results could become theoretical basis which to give a primary inference to the defects.The three-dimensional stress wave technology is especially fit for big diameter or independent wood components.4.The results of stress wave testing could be influenced by the number of sensors,the arrangement of sensors in the section,weather or non-independent of the tested object.The more the number of sensors,the more acute of the result of stress wave testing;the accurate of the testing are influenced by the position of sensors,so the sensors should be averaged arrangement;the non-independent should be tested further besides the usual stress wave testing.5.The velocity of stress wave transmission could be influenced by the moisture content.radial velocity of stress wave in the test section increases with the decrease of moisture content,lower than the fiber saturation point(＜30%),the velocity increases more intensivly.6.The results showed that there were positive correlations of larch(Larix sp.),spruce(Picea sp.), pine(Pinus sp.) in the dynamic MOE which was measures with stress wave and mechanical MOE.7.The results showed that there were positive correlations of larch(Larix sp.),spruce(Picea sp.), pine(Pinus sp.) in the dynamic MOE which was measures with stress wave and MOR. 8.The relationship of density and dynamic MOE,MOR of three specimens with decay are:spruce (Picea sp.)＞larch(Larix sp.)＞pine(Pinus sp.),and the attenuation of MOR is obvious,it shows that stress wave velocity is relationship with density of old wood,mechanical MOE and MOR,the more the mechanical MOE and MOR and the density of old wood,the more of stress wave velocity.The innovative points of the study as follow:1.Use ARBOTOM impulse stress wave technology firstly to check famous ancient artificial buildings of our country and ancient wood components which were replaced,study the basis of judgment to check the crack,decay,hole and so on lie in the innertal of the ancient components of ancient artificial buildings with 2D and 3D testing.2.Study the influence factors of ARBOTOM impulse stress wave technology to check ancient artificial buildings,use2 sensors of ARBOTOM to get the longitudinal velocity of old wood components, and analysis the correlation of dynamic MOE and mechanical MOE and MOR for the first time.