静态法和共振法测量弹性模量的不确定度分析

Uncertainty analysis of measuring elastic modulus by static method and resonance method

分别采用静态法和共振法测量金属材料的弹性模量。其中静态法采用电子万能试验机和引伸计进行哑铃型棒状试样拉伸试验,采用工程应力-工程应变曲线弹性段的斜率计算弹性模量。共振法采用动态弹性模量与阻尼分析仪进行矩形自由梁试样的弯曲共振试验,基于弹性模量和弯曲共振基频的关系进行间接测量。依据测量不确定度评定与表示标准,以7075航空铝合金材料为例,对比了弹性模量静态法和共振法测量不确定度。结果表明:静态法的最大不确定度来源是引伸计测量的变形误差,共振法的最大不确定度来源是厚度测量误差。采用共振法的测量结果优于静态法测量结果,测量不确定度分析可为弹性模量的测量方法选择和结果评定提供参考。

The elastic modulus of metal materials was measured by the static method and the resonance method,respectively.In the static method,an electronic universal testing machine and extensometer were used for the tensile test of dumbbell-shaped bar samples,and the slope of the elastic section of the engineering stress-engineering strain curve was used to calculate the elastic modulus.In the resonance method,the bending resonance test of rectangular free beam sample was carried out by using dynamic elastic modulus and damping analyzer,and the elastic modulus was indirectly measured according to the relationship between the elastic modulus and the fundamental bending frequency.According to the standard for evaluation and expression of uncertainty in measurement,the measurement uncertainty of elastic modulus by static method and resonance method was compared using 7075 aviation aluminum alloy as an example.The results showed that the maximum uncertainty of static method was the deformation error measured by extensometer,and the maximum uncertainty of resonance method was the thickness measurement error.The measurement results by resonance method were better than those by static method.The measurement uncertainty analysis could provide reference for the selection of measurement methods and evaluation of results of elastic modulus.