无损检测足尺人造板弹性模量和面内剪切模量

【目的】研究足尺人造板沿长度和宽度方向的弹性模量与面内剪切模量的快速和在线无损检测。提出了一种基于横向自由振动的方法,即通过测量在四节点支承下足尺人造板自由振动时沿长度方向的一阶弯曲、沿宽度方向的一阶弯曲和扭转的3个频率以及板材的密度,来检测其沿长度和宽度方向的弹性模量与面内剪切模量。【方法】利用试验模态分析方法,对3种厚度中密度纤维板和2种厚度胶合板的足尺人造板进行了模态试验,获得了四节点支承下足尺人造板自由振动前9阶模态的频率和振型,同时也进行了力学性能检测试验,并对测量结果进行了重复性分析。【结果】中密度纤维板和胶合板第1和第7阶的振型都分别是沿长度方向的一阶弯曲和沿宽度方向的一阶弯曲,中密度纤维板第5阶的振型是扭转,胶合板第4阶的振型是扭转,同时该检测方法测量结果的重复性很好。【结论】基于横向自由振动理论测定四节点支承下足尺人造板沿长度和宽度方向的弹性模量以及面内剪切模量是可行的。

Non-destructive determination of modulus of elasticity and in-plane shear modulus of full-size wood composite panels

Objective] This paper presents a method based on transverse free vibration for the rapid,online non-destructive determination of the modulus of elasticity (MOE) along the length and width directions as well as in-plane shear modulus of full-size wood composite panels (WCPs).Accordingly,the three frequencies for the first-order bending along the length and width directions,as well as the torsion for the full-size WCPs supported on four nodes and their density,were measured.Method] Five full-size WCP pieces were tested through experimental model analysis,including three different thicknesses of medium density fiberboards (MDF) and two different thicknesses of plywood(PW).The naturalfrequencies and mode shapes of the first nine modes for full-size WCPs supported on four nodes were obtained.Following modal testing,the mechanical properties for the full-size WCPs were neasured,and the repeat ability of the test results was analyzed.Result] The first and seventh order mode shapes for both MDF and plywood indicated the first order bending along the length and width directions respectively.The fifth order mode for MDF and fourth order mode for plywood indicated torsion.The results of the test showed excellent repeatability.Conclusion] Determination of the MOE along the length and width directions,as well as the in-plane shear modulus of the full-size WCPs supported on four nodes based on the transverse free vibration,is thus feasible.