定向刨花板剪切模量和弹性模量动态测试

Dynamic Testing of Shear Modulus and Elastic Modulus of Oriented Strand Board

【目的】研究定向刨花板(OSB)的各向异性,探讨OSB面内剪切模量动态和静态测试方法,以提供一种快速、简便、重复性好、精度高的动态测试方法测量和分析OSB弹性常数。【方法】应用ANSYS程序计算OSB自由板和悬臂板试件的振形系数,给出振形系数依赖于板长宽比和宽厚比的关系式,通过仿真计算、动态试验和方板静态扭转试验验证其正确性。动态试验测试OSB剪切模量试件从一块整张OSB上下料制作,分为3个方向,即沿整板纵向下料制作的试件(0°或x向)、横向方向下料制作的试件(90°或y向)和沿与纵向呈45°方向下料制作的试件;方板扭转试验测试OSB剪切模量试件沿整板纵向或横向下料制作;动态测试OSB纵向、横向和45°方向弹性模量以及面内剪切模量和45°方向剪切模量。【结果】OSB实测纵向弹性模量是横向弹性模量的2.89倍,45°方向剪切模量小于面内剪切模量。正交各向异性材料方板扭转试验测试剪切模量推算公式需用±45°方向应变测量值的差值进行推算,将其用于OSB,测得的静态剪切模量与动态测试的剪切模量相当吻合。【结论】OSB弹性模量具有方向性,纵向最大,横向最小,45°方向介于二者之间;自由板扭转振形法和悬臂板扭转模态法适用于动态测试OSB面内剪切模量,其正确性得到方板扭转试验验证;0°和90°OSB动态测得的剪切模量几乎相等,可作为OSB面内剪切模量Gxy的估计值;OSB不宜按单向复合材料处理,在理论分析时宜按正交各向异性处理,OSB45°方向的剪切模量G45°<G0°或G90°;方板扭转试验用于测试OSB面内剪切模量时,应在方板两表面中心沿2条对角线粘贴±45°应变片,按±45°方向应变测量值的差值进行推算;动态测试的剪切模量与方板扭转试验测试的剪切模量相当吻合,扭转振形法测试OSB剪切模量可行。

【Objective】In recent years,there have been few researches on the shear modulus test method for oriented strand board(OSB).It has been related to the acoustic emission method and the transverse vibration of the cantilever member to test the OSB shear modulus.This paper studies the OSB from the experimental aspect.Anisotropy,from the theoretical analysis and experimental aspects to explore the dynamic and static method for testing the in-plane shear modulus of OSB,involves the new concept of OSB free plate and cantilever plate shape coefficient,the principle of square plate static torsional strain method and its principle test implementation.【Method】Using ANSYS program to calculate the vibration shape coefficient of the OSB free plate and the cantilever plate test,it is given that the mode shape coefficient is dependent on the relational expression of length-to-width ratio and width-to-thickness ratio and verify the correctness of simulation calculation,dynamic test and static torsion test plate.The dynamic test of shear modulus about the OSB is made from a piece of the whole OSB board material,and the specimens were divided into three directions,namely,making specimen along the whole plate longitudinal(0°or x)direction,transverse(90°or y)direction and to the direction of 45°along with specimen longitudinal direction making.The test piece for testing the OSB shear modulus by square plate torsion test is made along the entire plate in the longitudinal or transverse direction.This study tests the dynamic elastic modulus of the OSB plate specimens about the longitudinal,transverse and 45°direction,and also tests the OSB plate specimen’s dynamic in-plane shear modulus and shear modulus of 45°direction.【Result】The measured longitudinal elastic modulus of OSB plate is 2.89 times of its transverse elastic modulus,and the shear modulus of the 45°is smaller than that of in-plane shear modulus.It was given that the shear modulus through square plate torsion test which is suitable orthotropic material,and the calculation formula needs to use±45°direction’s difference of strain measurement value of the shear modulus calculation,for the OSB plate,the measured static shear modulus and dynamic shear modulus test very well.【Conclusion】The OSB plate’s elastic modulus presents a direction tendency.The longitudinal elastic modulus is maximum,the transverse elastic modulus is minimum,and the 45°direction elastic modulus is the medium;the free plate torsional vibration shape method and cantilever plate torsional mode method are suitable for dynamic testing of OSB plate in-plane shear modulus,and its correctness is verified in square plate torsion test shear modulus;0°and 90°OSB plate dynamic are measured almost equal,and can be used to estimate the OSB plate in-plane shear modulus value G xy;OSB plate should not deal according to unidirectional composite processing,and in the theoretical analysis should be according to the orthotropic plate processing,OSB 45°direction of shear modulus G 45°<G 0°or G 90°;square plate torsion test for testing OSB in-plane shear modulus,should be in the center of the surface two square plate along the two diagonal paste±45°degrees of strain gages,according to the difference of±45°direction strain measurement calculation;shear modulus by dynamic test agrees with the shear modulus by square plate torsion test,which shows that the torsional vibration method is feasible in the test of OSB sheet shear modulus.