光干涉法高精度材料线膨胀系数测量

中国计量科学研究院研制的高精度材料线膨胀系数测量装置,满足温度范围为5～40 ℃、被测件长度在20～1 000 mm之间的线膨胀系数测量。采用激光干涉法测量被测件长度变化量,用高精度温度传感器测量温度值。设计了热平衡式干涉镜,利用空气折射率修正和零位误差补偿技术,保证在5～40 ℃变温范围内激光干涉仪的测量精度。以500 mm标准量块作为测量对象,线膨胀系数测量结果与德国物理技术研究院(PTB)测量结果的相对偏差为0.2%。材料线膨胀系数测量不确定度达到3×10^-8K^-1。

Thermal Expansion Coefficient Measurements with Precision Interferometer

The thermal expansion measurements with NIM’s precision interferometer are described.The measurements are based on the observation of the length change of the material samples as a function of a temperature using laser interferometry. The interferometer and the material sample up to 1m are situated in a tight enclosure which temperature is controlled by a water circulation within a temperature range from 5 ℃ to 40 ℃.A heat-balanced interference mirror was designed.A high precision temperature measuring system is used for measuring the temperature of the material sample and the air.The accurate determination of the refractive index of air and the real-time compensation of zero error are accomplished. Using an 500 mm gauge block, thermal expansion coefficient is measured with a relative deviation of less than 0.2%, and it was compared with those of Physikalisch-Technische Bundesanstalt (PTB) of Germany. The coefficient of thermal expansion can be obtained with a uncertainty less than 3×10^-8K^-1.