孔对落叶松板材抗弯性能的影响  

Effect of holes on the bending strengthof larchlumber

作　　者：谢力生[1] 伍家华 刘佳权 陶钧 刘嘉诚 XIE Lisheng;WU Jiahua;LIU Jiaquan;TAO Jun;LIU Jiacheng(College of Materials Science and EngineeringCentral South University of Forestry and Technology,Changsha 410004,Hunan,China;Shenzhen Academy of Metrology&Quality Inspection,Shenzhen 518055,Guangdong,China)

机构地区：[1]中南林业科技大学材料科学与工程学院,湖南长沙410004 [2]深圳市计量质量检测研究院,广东深圳518055

出　　处：《中南林业科技大学学报》2021年第7期150-155,164,共7页Journal of Central South University of Forestry & Technology

基　　金：国家林业公益性行业科研重大专项(201304504);湖南省高校创新平台开放基金项目(19K110,14K113)。

摘　　要：【目的】研究孔的位置和直径对落叶松板材抗弯性能的影响规律。【方法】以兴安落叶松无缺陷木材为研究对象,首先采用抗弯试验方法测试一批试件的弹性模量与静曲强度,建立其静曲强度与弹性模量的数学模型;接着对其他试件采用同样的方法(荷载只加到破坏荷载的约3/7)测试其弹性模量,利用前述数学模型推算其静曲强度;然后对其进行钻孔,并测定各试件钻孔后的静曲强度和弹性模量;比较各试件钻孔前后的静曲强度和弹性模量值,求取孔所引起的静曲强度削弱率和弹性模量削弱率,分析孔对试件抗弯性能的影响规律。【结果】孔与试件下表面或上表面相切,孔径与厚度之比为0.2时,板材静曲强度削弱率(平均值)达38.84%或27.02%;试件的下表面或上表面有半孔时,静曲强度削弱率为21.55%或7.99%;孔位于试件厚度中心层下方且与之相切时,静曲强度削弱率仅为0.85%;对于孔相切于抗拉侧、孔径与厚度之比为0.2的试件,孔位于支承点到加载点的中间位置时,其静曲强度削弱率为21.44%,相比孔在加载点位置时的38.84%,下降了约45%;对于加载点下方与试件下表面相切的孔,孔径与厚度之比由0.2增大到0.5时,静曲强度削弱率由38.84%增大到82.08%;钻孔试件的弹性模量所对应的静曲强度值具有显著的离散性。【结论】1)对于板材长度方向,孔位于加载点下方时的静曲强度削弱率最大;随着孔远离加载点其静曲强度削弱率减小。2)对于板材厚度方向,孔越靠近板面其静曲强度削弱率越大,且受压侧的强度削弱率大于受拉侧;孔与板面相切时其静曲强度削弱率最大,且孔位于受拉侧时更大;孔位于中心层稍偏下时其静曲强度削弱率最小。3)处于板面的半孔,对板材静曲强度的削弱也很显著,且受拉侧的影响更大。4)孔径对板材静曲强度的影响显著,随着径厚比的增大,静曲强度削弱率呈直线递�【Objective】The purpose of this work is to study the effect law of hole location and diameter on the bending properties of larch plates.【Method】Taking non-defective larch plates as the research object,the MOE and the MOR of a batch of test pieces were firstly tested by bending test method,and established their mathematical model.The same method(load is only added to about 3/7 of the breaking load)to test the MOE,and the mathematical model is used to calculate the MOR;then the test piece is drilled,and determine the MOR and the MOE after drilling.By comparing the MOR and the MOE values before and after drilling of each test piece,the experiment calculated their weakening rate caused by the hole,and analyzed the influence of the hole on the bending properties of test pieces.【Result】The weakening rate(the average value)of MOR reached 38.84%or 27.02%,when the hole tangent to the surface of top or the surface of bottom and the ratio of aperture to thickness is 0.2.The weakening rate of MOR is 21.55%or 7.99%,when half hole in the lower surface or upper surface.The weakening rate of MOR is only 0.85%,when the hole tangent and below to the central layer of the thickness direction of the specimen.The MOR weakening rate is 21.44%,when the hole tangent to the tensile side and ratio of aperture to thickness is 0.2 and the hole in the middle of the supporting point to the loading point,which is about 45%lower than the holes are at the loading point.The weakening rate of MOR increases from 38.84%to 82.08%,when the ratio of aperture to thickness increases from 0.2 to 0.5.The MOE value corresponding to the MOR value of the drilled test pieces has significant discreteness.【Conclusion】1)For the length direction of the plate,the weakening rate of MOR is the largest when the hole below the loading point;The weakening rate of MOR decreases with the distance of hole to the loading point increasing.2)For the thickness direction of the plate,the weakening rate of MOR will be greater when the distance of hole to the surfac

关 键 词：落叶松 孔 静曲强度 弹性模量 数学模型 

分 类 号：S791.22[农业科学—林木遗传育种]