金属压力囊与应变测量技术在异型超导磁体结构装配过程中的应用研究

Pressurized Bladders and strain measurments technology for allotype superconducting magnet structure during an assembly

为了研究异型超导磁体结构预应力施加及其应变控制性测量等问题,基于自主集成的气压-水压混合高压增压系统,结合电阻应变片与非接触式DIC(Digital Image Correlation)全场应变测量方法,本文提出了一种超导磁体结构装配后预应力施加与应变测量控制技术。为了验证研制系统及其应变测量的可靠性和准确性,模拟超导二极线圈结构,自制了一套带有铝壳约束的铁质二极结构,对其进行装配后的预应力施加与应变测量,即:在二极结构内部放置一种自主研制的类似千斤顶设备--用薄钢板制成的长方形金属压力囊(称Bladder),利用自制的高压增压系统将较高的水压打入压力囊中,通过其有限的位移对二极结构内部人为地施加均布压应力,最终到达为二极结构内部施加预应力的目的。在施加预应力过程中,运用电阻应变片与基于高速CCD(Charge Coupled Device)设备的非接触DIC技术,对二极结构外部的约束结构--铝壳进行实时的应变测量。多组重复性实验结果表明:高压增压系统可控水压范围为5~120MPa,步长为4MPa,可同步显示压力,并且在此范围内能够维持设定的压力恒定不变,误差控制在±1.5MPa以内;采用连续激光焊接技术自主研制的加宽型金属Bladder可在30MPa范围内循环使用8次以上;对于带有铝壳约束的铁质二极结构,其铝壳表面的应变与打压压强成线性关系,电阻应变片与非接触的CCD应变测试技术均能给出高精度的测量结果,且非接触的CCD应变测试技术可以给出打压过程中铝壳表面全场应变测试结果。相关设备、技术和结果将为中科院近代物理研究所自主研制的全Nb3Sn超导离子源装配后预应力施加以及应变控制性测量提供方法和指导。

In order to study the pressure exertion and the strain measurement and control of allotype superconducting magnet structure,some key technologies based on pneumatic-hydraulic booster system and homemade pressurized Bladders are developed.The resistance strain gauges and a high speed/resolution CCD camera with noncontact digital image correlation method to measure the full-field strain are employed.To verify the reliability and accuracy of pneumatic-hydraulic booster and strain measurement system,the iron dipole with shrink-fit aluminum shell is used to simulate the allotype superconducting magnet structure′s assembly.During its assembly and pressure exertion,strain on shrink-fit aluminum shell is detected synchronously by the strain gauges and the high-speed CCD camera,respectively.The results show that the pneumatic-hydraulic booster system can work well between 5 MPa and 120 MPa with the controllable step of 4 MPa and the deviation of±1.5 MPa.The widening pressurized Bladders made by the continuous laser welding technology can be used for 8 times under 30 MPa hydraulic conditions.There is a linear relationship existing on strain between shrink-fit aluminum shell and Bladder′s pressure for the iron dipole with shrink-fit aluminum shell.Strain gauges and the high speed/resolution CCD camera with noncontact digital image correlation method can both work well during assembly and pressure exertion of the iron dipole with shrink-fit aluminum shell,and the full-field strain of aluminum shell can be obtained under proper experimental conditions including lights,speckle and focal length.The present results may provide some basis measurements on pressure exertion and strain measurements of full Nb3Sn superconducting ion sourcesmagnet during its assembly at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS).