Study On Non-destructive Testing And Fracture Monitoring Of Spec Timber

This study investigated the non-destructive testing and fracture monitoring of spec timber by theory, experiment and model. The different methods of dynamic and static testing were used to obtain the diagnostic parameters. The regression analysis between the parameters and strength were obtained on the basic of theory to assess the strength. The acoustic emission technology was used to real time monitor samples. And the finite element model was set up to predict the distortion and stress distribution of sawn timber. The main purpose was to improve the accuracy of strength grading processes with the aim of achieving a better utilization of the available timber qualities and provide reference for the designing of wood construction. The results were summarized as following:(1) Dynamic characteristics (dynamic modulus of elasticity, resonant frequency) and effect factor (density, knot and so on) were systematically studied by using transverse vibration testing system. Dynamic characteristics, static characteristics and MOR were studied by regression analysis,the dynamic modulus of elasticity can be used as a testing index of non-destructive evaluation.(2) The regression analysis of static modulus of elasticity and bending strength was studied by flatwise bending. While span is 900mm, the result is better.(3) Density can not be assessed as a single indicator, while the static modulus of elasticity as indicators of strength grading, can increase the proportion of high-grade lumber, intended to make the best use of the objective material.(4) Acoustic emission technique appears effectively to avoid excessive loading of specimen damage for real-time monitoring test pieces loaded in the process of whether there had been minor damage, by characteristic parameters (the ringing counting , swing and so on).(5) ANSYS was used for finite element analysis and deformation of the description in dimension lumber, stress distribution and deformation were clearly observed under certain load, from ANSYS. Test results were compared with the analysis, the relative error is less than 10%.