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MDF弹性模量、泊松比和剪切模量静态测试方法探讨

王韵璐 王正 李敏敏 曹瑜

王韵璐, 王正, 李敏敏, 曹瑜. MDF弹性模量、泊松比和剪切模量静态测试方法探讨[J]. 北京林业大学学报, 2017, 39(10): 117-121. doi: 10.13332/j.1000-1522.20170107
引用本文: 王韵璐, 王正, 李敏敏, 曹瑜. MDF弹性模量、泊松比和剪切模量静态测试方法探讨[J]. 北京林业大学学报, 2017, 39(10): 117-121. doi: 10.13332/j.1000-1522.20170107
WANG Yun-lu, WANG Zheng, LI Min-min, CAO Yu. Discussion on static testing method of material MDF constants of elastic modulus, Poisson's ratio and shear modulus[J]. Journal of Beijing Forestry University, 2017, 39(10): 117-121. doi: 10.13332/j.1000-1522.20170107
Citation: WANG Yun-lu, WANG Zheng, LI Min-min, CAO Yu. Discussion on static testing method of material MDF constants of elastic modulus, Poisson's ratio and shear modulus[J]. Journal of Beijing Forestry University, 2017, 39(10): 117-121. doi: 10.13332/j.1000-1522.20170107

MDF弹性模量、泊松比和剪切模量静态测试方法探讨

doi: 10.13332/j.1000-1522.20170107
基金项目: 

南京林业大学大学生科技创新项目立项课题 DXSKC-201606

江苏省苏北科技专项(富民强县)项目 BN2015143

详细信息
    作者简介:

    王韵璐。主要研究方向:木材科学与技术。Email: wyl_12@126.com   地址:210037 南京市龙蟠路159号南京林业大学材料科学与工程学院

    责任作者:

    王正,博士,高级工程师。主要研究方向:木材科学与技术。Email:wangzheng63258@163.com  地址:同上

  • 中图分类号: TS612

Discussion on static testing method of material MDF constants of elastic modulus, Poisson's ratio and shear modulus

  • 摘要: 提出了一种静态测试MDF泊松比μ和弹性模量E的新方法,即悬臂板静态弯曲法。首先,阐述了悬臂板静态弯曲法测试MDF泊松比和弹性模量的原理。根据MDF悬臂板受集中力作用下静态弯曲应力、应变分析,确定了静态测试MDF泊松比的十字应变片粘贴位置。为说明悬臂板静态弯曲法测试MDF弹性模量和泊松比的正确性,采用轴向拉伸法、四点弯曲法进行MDF的弹性模量和泊松比值的验证试验。最后,针对MDF为各向同性材料特点,通过方板静态扭转试验测得的剪切模量G,验证悬臂板静态弯曲法测试弹性模量和泊松比的正确性。结果表明:悬臂板静态弯曲法中,用于测试泊松比的应变片粘贴位置由板内横向应力σy=0的位置所确定;悬臂板静态弯曲法和轴向拉伸法测试的MDF的泊松比和弹性模量吻合得相当好,悬臂板静态弯曲法测试泊松比和弹性模量的正确性得到轴向拉伸试验的验证;悬臂板静态弯曲法测试MDF弹性模量E、泊松比μ的正确性还得到方板静态扭转试验的验证,即根据悬臂板静态弯曲法测试得到MDF的弹性模量和泊松比,并按G=E/2(1+μ)推算剪切模量G是可行的。

     

  • 图  1  悬臂板自由端中点受集中力静态弯曲时-εy/εxσy/σxx/l的变化

    σy为横向应力,Pa;σx为纵向应力,Pa;εy为横向应变;εx为纵向应变;x表示悬臂板中央线上的点到固定端的距离,m; l表示悬臂外伸长度,m。

    Figure  1.  Changes of y/εx and σy/σx with x/l during static bending caused by the concentrated force at the midpoint of the free end

    σy is transverse stress (Pa), σx is longitudinal stress (Pa), εy is transverse strain, εx is longitudinal strain, x represents for the distance from cantilever plate central line point to the fixed end (m), and l is cantilever length (m).

    图  2  悬臂板静态弯曲法测试示意图

    P为载荷;h为厚度;b为宽度;a为加载点到纵向应变片中心的距离。

    Figure  2.  Schematic diagram of static bending test of cantilever plate

    P is load, h is thickness, b is width, and a is the distance from load point to the center of the longitudinal strain gauge.

    图  3  悬臂板静态弯曲试验测试泊松比十字应变片粘贴位置示意图

    Figure  3.  Schematic diagram of the cross strain gauge position during the static bending test of cantilever plate to test the Poisson's ratio

    图  4  测试MDF弹性模量和泊松比的试验框图

    Figure  4.  Test block diagram of MDF elastic modulus and Poisson's ratio

    图  5  四点弯曲法测试弹性模量(a)和泊松比(b)推荐的应变片位置

    Figure  5.  Recommended placements of the strain gauges to test E(a) and μ(b) during four-point bending test

    图  6  方板静态扭转试验加载装置照片

    Figure  6.  Picture of loading device of square plate static torsion test

    图  7  方板四角点的受力图及应变片位置

    Figure  7.  Diagram of the stress on four corners of the square plate and the placement of the strain gauge

    表  1  悬臂板静态弯曲法测试的MDF弹性模量和泊松比(ΔP=4.165 N, a=228 mm)

    Table  1.   MDF elastic modulus and Poisson's ratio by static bending test of cantilever plate(ΔP=4.165 N, a=228 mm)

    试件编号Specimen No. Δεy×106 Δεx×106 弹性模量Elastic modulus (E)/GPa 泊松比Poisson's ratio (μ)
    MDF-1 -61.4 222.1 2.58 0.279
    MDF-2 -56.2 218.2 2.66 0.258
    MDF-3 -47.8 219.3 2.72 0.218
    均值Mean value -55.1(12.4%) 219.9(0.9%) 2.65(2.6%) 0.252(12.3%)
    注:Δεy为横向应变增量; Δεx为纵向应变增量; 表中括号内为变异系数。Notes: Δεy is the increment of transverse strain, εx is the increment of longitudinal strain. There are variation coefficients in brackets in the table.
    下载: 导出CSV

    表  2  各种方法测试MDF的EμG

    Table  2.   Values of E, μ and G obtained by different tests

    悬臂板静态弯曲试验
    Static bending test of cantilever plate
    轴向拉伸试验
    Axial tensile test
    四点弯曲试验
    Four-point bending test
    方板扭转试验
    Square plate torsion test
    E/GPa μ G/GPa E/GPa μ G/GPa E/GPa μ G/GPa G/GPa
    2.65(2.6%) 0.252(12.3%) 1.06 2.64(3.2%) 0.247(4.3%) 1.06 2.76(2.9%) 0.234(1.9%) 1.12 1.01(11.8%)
    注:悬臂板静态弯曲试验、轴向拉伸试验、四点弯曲试验中的G值是通过$\mathit{G}{\rm{ = }}\mathit{E}{\rm{/2(1 + }}\mathit{\mu }{\rm{)}}$.计算得到的; 方板扭转试验则直接测试得到G值。表中括号内为变异系数。Notes: the G values of static bending test of cantilever plate, axial tensile test and four-point bending test are calculated by $\mathit{G}{\rm{ = }}\mathit{E}{\rm{/2(1 + }}\mathit{\mu }{\rm{)}}$. The square plate torsion test directly tests the G value. There are variation coefficients in brackets in the table.
    下载: 导出CSV
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  • 收稿日期:  2017-03-25
  • 修回日期:  2017-08-20
  • 刊出日期:  2017-10-01

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