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Experimental and Numerical Analysis of Hydroformed Tubular Materials for Superconducting Radio Frequency (SRF) Cavities

Kim, Hyun Sung
http://rave.ohiolink.edu/etdc/view?acc_num=osu1462533811

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
Superconducting radio frequency (SRF) cavities represent a well established technology benefiting from some 40 years of research and development. An increasing demand for electron and positron accelerators leads to a continuing interest in improved cavity performance and fabrication techniques. Therefore, several seamless cavity fabrication techniques have been proposed for eliminating the multitude of electron-beam welded seams that contribute to the introduction of performance-reducing defects. Among them, hydroforming using hydraulic pressure is a promising fabrication technique for producing the desired seamless cavities while at the same time reducing manufacturing cost. This study focused on experimental and numerical analysis of hydroformed niobium (Nb) tubes for the successful application of hydroforming technique to the seamless fabrication of multi-cell SRF cavities for particle acceleration. The heat treatment, tensile testing, and bulge testing of Cu and Nb tubes has been carried out to both provide starting data for models of hydroforming of Nb tube into seamless SRF cavities. Based on the results of these experiments, numerical analyses using finite element modeling were conducted for a bulge deformation of Cu and Nb. In the experimental part of the study samples removed from representative tubes were prepared for heat treatment, tensile testing, residual resistance ratio (RRR) measurement, and orientation imaging electron microscopy (OIM). After being optimally heat treated Cu and Nb tubes were subjected to hydraulic bulge testing and the results analyzed. For numerical analysis of hydroforming process, two different simulation approaches were used. The first model was the macro-scale continuum model using the constitutive equations (stress-strain relationship) as an input of the simulation. The constitutive equations were obtained from the experimental procedure including tensile and tube bulge tests in order to investigate the influence of loading condition on deformation behavior. The second model was a multi-scale model using both macroscopic continuum model and microscopic crystal plasticity (CP) model: Frist, the constitutive equation was obtained from the other microscopic simulation model (CP-FEM) using the microstructural information (i.e., orientation) of materials from the OIM and simple tensile test data. Continuum FE analysis based on the obtained constitutive equation using CP model were then fulfilled. Several conclusions can be drawn on the basis of the experimental and numerical analysis as follows: 1) The stress-strain relationship from the bulge test represents a more accurate description of the deformation behavior for a hydroforming than that from tensile tests made on segments cut from the tubular materials. 2) For anisotropic material, the incorporation of anisotropic effects using anisotropy coefficient from the tensile test led to even more accurate results. 3) A multi-scale simulation strategy using combination of continuum and CP models can give high quality predictions of the deformation under hydroforming of Cu and Nb tubes.
Michael Sumption (Advisor)
Glenn Daehn (Committee Member)
Alan Luo (Committee Member)
Edward Overman (Committee Member)
154 p.
Engineering
SRF cavities, hydroforming, FEM, Crystal plasticity

Recommended Citations

Citations

  • Kim, H. S. (2016). Experimental and Numerical Analysis of Hydroformed Tubular Materials for Superconducting Radio Frequency (SRF) Cavities [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462533811

    APA Style (7th edition)

  • Kim, Hyun Sung. Experimental and Numerical Analysis of Hydroformed Tubular Materials for Superconducting Radio Frequency (SRF) Cavities. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1462533811.

    MLA Style (8th edition)

  • Kim, Hyun Sung. "Experimental and Numerical Analysis of Hydroformed Tubular Materials for Superconducting Radio Frequency (SRF) Cavities." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462533811

    Chicago Manual of Style (17th edition)

osu1462533811
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This open access ETD is published by The Ohio State University and OhioLINK.