加载头不确定度评定方法研究

在风洞天平校准系统中,加载头的主要功能是保证力的三要素中“作用点”位置的准确。然而,由于加工制造误差和尺寸测量误差的存在,加载头施力点的实际位置总是会偏离其相应的理论正确位置,从而导致施力点位置坐标产生误差。这些误差会经由加载头传导到天平校准公式中,从而影响天平载荷测量的准确性。因此,有必要对加载头不确定度的评定方法进行研究。首先采用GUM(guide to the expression of uncertainty in the meas-urement,ISO/IEC GUIDE 98-3:2008)方法建立了加载头不确定度的评定方法和步骤,接着给出了加载头不确定度的表示方法及指标要求,最后以某加载头为例,给出了不确定度评定的详细过程及结果。结果表明,该型加载头各施力点位置坐标的扩展不确定度平均值为0.044mm;力矩力臂的相对扩展不确定度平均值为0.0072%。

Research on evaluation method for uncertainty of a load adapter

In the wind tunnel balance calibration system,the main function of the load adapter is to ensure that the application point’s location coordinates are accurate.However,because of the manufacture error and dimension measurement error,the application points’real locations are drifted off from the relevant right locations in the theory,which brings errors to the applica-tion point’s location coordinates.These errors would be transferred to a balance calibration for-mula by a load adapter,which affects the accuracy of the loads measured by the balance.There-fore,it is necessary to research on the evaluation and expression of the uncertainty for a load a-dapter.Firstly,according to GUM (guide to the expression of uncertainty in the measurement, ISO/IEC GUIDE 98-3:2008),a method and steps for uncertainty assessment of a load adapter are founded.Then an expression and technical indices of the uncertainty for a load adapter are given.Finally,taking the type A load adapter belonging to the balance calibrated rig (code:TJZ-1 )for example,detailed evaluation processes and results about the uncertainty are given.The e-valuation results of the uncertainty indicate that the mean value of the standard uncertainty of all application points is 0.044mm;the mean value of the relative expanded uncertainty of all mo-ment’s arms is 0.0072%.