SPF规格材弹性模量的动态测试及其概率分布  

Dynamic Testing and Probability Distribution of Elastic Modulus of SPF Dimension Lumbers

作　　者：王正[1] 顾玲玲[2] 高子震[1] 刘斌[2] 

机构地区：[1]南京林业大学材料科学与工程学院,南京210037 [2]南京林业大学机械电子工程学院,南京210037

出　　处：《林业科学》2015年第2期105-111,共7页Scientia Silvae Sinicae

基　　金：2013-2014年江苏省高校优势学科建设工程项目资助(PAPD)

摘　　要：【目的】应用频率法精确测量SPF规格材的弹性模量，探讨应用威布尔分布分析其弹性模量数据的可行性。【方法】从南京北美木屋有限公司一批 SPF规格材中随机抽取容量为300的样本作为试件，采用弹性绳垂直自由悬挂方式的支承结构对试件实现自由梁，模态试验验证自由梁的精度。在瞬态激励下，通过测试试件一阶弯曲频率，得其弹性模量值；应用应力波法验证频率法测试结果的正确性。对其测试数据采用 Weibull分布拟合检验、威布尔分布和正态分布的 K-S检验、SPF规格材总体弹性模量在给定值下的概率计算和 SPF 规格材质量评价的概率分布方法进行研究。【结果】频率法和波速法测得的弹性模量具有较好的相关性；从威布尔分布和正态分布在参数未知时的 K-S检验结果可知，SPF规格材弹性模量不服从两参数威布尔分布（Eu =0），但服从于位置参数 Eu 大于最小测试值一半的三参数威布尔分布和正态分布；从 SPF 规格材总体弹性模量在给定值下的概率数据分析可得：以3500，4000，4500 MPa为Eu 的设定值时，计算的概率值稳定且基本相同，这时Eu 设定值分别是弹性模量测试的最小值5526 MPa的63%，72%和81%，因此推荐采用根据实测数据最小值的60%～80%作为位置参数Eu 设定值的三参数威布尔分布进行概率计算；三参数威布尔分布和正态分布计算的 SPF规格材弹性模量在给定值下的概率相等；从 SPF 规格材弹性模量的概率分布曲线和概率密度曲线可知，威布尔概率密度相对于它的均值（9997 MPa）略显不对称性，弹性模量不超过7000 MPa 时，正态概率分布曲线略高于威布尔概率分布曲线，超过7000 MPa后，则正好相反。【结论】模态试验验证了文中的试验装置实现了试件自由悬挂的支承条件，提出了频率法的测试方案，保证了一阶弯曲振动固有频率测试精�[Objective]SPF dimension lumber is a principal material for light-frame timber structures. In this paper, modulus of elasticity （ MOE） of SPF dimension lumbers was accurately measured by frequency method. The feasibility of the measured data was studied by Weibull distribution. Then,the data was fitted linearly and verified by K-S method. Meanwhile,a series of possible Weibull parameters was obtained by linear fitting of MOE data in Weibull coordinate.[Method]We randomly extract SPF dimension lumbers with capacity of 300 from Nanjing Cogent Home Manufactory Ltd. We realize free beam of test samples by supporting structure hung vertically and freely with elastic rope. The accuracy of＆nbsp;free beam realization is proved by the result of modal test. Under transient excitation,the elastic modulus value of the samples is obtained by testing their first transverse bending frequency. The correctness of the test results of frequency method is proved by stress wave method. To exactly evaluate the quality of SPF dimensional lumbers,the testing data was deeply studied by using methods such as Weibull distribution, K-S method in normal distribution, calculation of probability data of MOE value under given values and probability distribution method. [Result]A good correlation was found between elastic modulus tested with frequency method and that tested with wave-speed method. As can be seen from the K-S testing results of Weibull distribution and normal distribution,the elastic modulus of SPF dimension lumbers is not subjected to two-parameter Weibull distribution （Eu =0）,but it is subjected to three-parameter Weibull distribution,in which location parameter Eu is larger than half of the minimum test value. By analyzing the probability data of MOE value under given values for the total SPF dimension lumbers,the calculated probability values are stable and similar when using 3 500,4 000 and 4 500 MPa as the given value of Eu. In this case,the given values of Eu are 63%,72% and 81% of the minimum value of elastic mo

关 键 词：云杉 -松木 -冷杉( SPF) 弹性模量 频率 应力波 威布尔分布 正态分布 

分 类 号：TS643[轻工技术与工程]