Study On Strength Test System Based On Time Domain Analysis And Frequency Domain Analysis For Laminated Veneer Lumber

Laminated veneer lumber is one of the most widely used wood-based panel product in the world,because of the good use of performance like high strength and structure uniform.So testing the strength of laminated veneer lumber is a very important way to improve the quality of laminated veneer lumber and utilization ratio of timber and also has great significance to timber industry.With this purpose, based on the analysis of laminated veneer lumber nondestructive testing techniques abroad, this paper comprehensive use many inspection techniques like time domain analysis method, frequency domain analysis method and extensional vibration method to design the laminated veneer lumber strength testing system. Also the mature testing theories of domestic and overseas are taken into consideration. Data acquisition card PCI-1710HG was selected to collect data information in this system. Industrial computer was used as the core processor in this system. Computer expert system was used to analysis vibration signal in time-domain and frequency-domain aspects. By analysising vibration signal, this system can extract characteristic parameters about time-domain and frequency-domain like dynamic elastic modulus and logarithmic decrement which can represente laminated veneer lumber strength. Therefore the system use these characteristic parameters to forecast the strength of laminated veneer lumber and grade them. Designing plan, testing principle, system constitutes, hardware design and software control method were discussed in this paper.By multiple comparison and analysis the data detected from this system and the data detected from mechanics testing machine, there is linear correlation between dynamic elasticity modulus, logarithmic decrement calculated by this system and bending strength tested by mechanics testing machine. Moreover dynamic elasticity modulus and logarithmic decrement calculated by this system can forecast the strength of laminated veneer lumber. Therefore, the conclusion can be made that it is practical to apply this detect system to measur laminated veneer lumber strength in laminated veneer lumber production line. This system can measure laminated veneer lumber dynamic elasticity modulu and logarithmic decrement promptly and predict the mechanical strength destructively. Moreover this system have friendly interface, stable and efficient, simple and practical, so that the theoretical basis for properly use and extension of laminated veneer lumber could be provided.