目的 实现平面场中主应变的测量不确定度评定.方法 首先建立主应变的是非线性传播测量模型,然后应用基于二阶TAYLOR级数展开理论的不确定度传播方法(LPU方法),开展平面问题中主应变的测量不确定度评定.针对二种常用的应变花,建立以主应变为输出量、以应变花之三个方向测量应变为输入量的测量模型,并将二阶LPU方法应用于该模型.设计数值计算算例,以说明主应变不确定度的评定过程和方法,并与一阶LPU结果进行了比较.结果 当应变花三个方向的应变测量结果相近时,文中方法与一阶LPU方法获得的主应变的不确定度评定结果存在明显的差异,主应变不确定度评定结果在数值上都大于应变花测量的不确定度.当应变花三个方向的应变测量结果相差较大时,文中方法和一阶LPU方法获得的主应变测量不确定度评定结果相差不大.结论 特定情况下,主应变的测量不确定度值远大于应变花测量的不确定度,且与一阶LPU方法的评定结果有显著差异,二者可相差一倍.%Objective To assess the measurement uncertainties of principal strain in plane field.Methods A measure-ment model of nonlinearity transmission was established for the principle strain. The Law of Propagation of Uncertainty (LPU) approach based on second order Taylor expansion was applied to analyze the measurement uncertainty of the prin-ciple strain. The measurement models were established for two typical strain rosettes with the principle strain as the out-put, the values measured in the three directions of the strain rosettes as the input and the LPU was applied to the models. Numerical examples were designed to illuminate the procedures and methods of assessment and to compare with the first order LPU estimations.Results When strain rosette strain measurements were close in three directions, uncertainty esti-mation results of the principal strain obtained through this method and the method of first-order LPU had obvious differ-ence. That of the principal strain was greater than that of the strain rosette in numerical value. When strain rosette strain measurements differ in three directions, the results obtained through this method and the first-order LPU method has little difference.Conclusion In special circumstances, the uncertainty value of principal strain is higher than those in any di-rection of rosette and different from the first order evaluations by one time.
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