采用电子拉力万能试验机测量了聚丙烯塑料的屈服应力，讨论了测量重复性、电子拉力万能试验机屈服负荷测量、游标卡尺宽度测量、游标卡尺厚度测量等因素带来的不确定度分量，计算了测量塑料屈服应力的合成标准不确定度及扩展不确定度。结果表明：当包含因子k=2、置信概率P=95%时，屈服应力测量的扩展不确定度为0.16 MPa。

The yield stress of polypropylene plastic was measured by electronic tensile universal testing machine. The uncertainty components caused by measurement repeatability, yield load measurement of electronic tensile universal testing machine, width measurement of vernier caliper and thickness measurement of vernier caliper were discussed. The combined standard uncertainty and expanded uncertainty of measuring plastic yield stress were calculated. The results show that the expanded uncertainty of yield stress measurement was 0. 16 MPa when the inclusion factor k=2 and the confidence probability p=95%.