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University of Canterbury

1. Hamilton, Kent Anthony. Improvements to the Design of a Flexible Diaphragm for use in Pressure Wave Generators for Cryogenic Refrigeration Systems.

Degree: M. Eng., Mechanical Engineering, 2013, University of Canterbury

Low cost cryocoolers suitable for long term use in industrial environments are required for superconducting technologies to be competitive with copper based devices in real world applications. Industrial Research Limited is developing such cryocoolers, which use metal diaphragm based pressure wave generators to convert electrical energy to the gas volume displacement required. This project explores methods of increasing the volume displacement provided by the diaphragms while ensuring the components stay within the acceptable material limits. Various alternative diaphragm shapes are tested against the currently used shape through finite element analysis. In addition to testing alternative diaphragm shapes, each shape’s dimensions are optimised. It is concluded the currently used design can be improved by offsetting the piston rest position and slightly reducing the piston diameter. A more detailed analysis is carried out of the bend radii created during fabrication of the diaphragm, and physical testing is performed to verify unexpected calculated stress concentrations. High stresses are observed, however it is concluded unmodelled material features have a large effect on the final stress distribution. It is recommended advantageous shape changes calculated in the first part of the work be trialled to increase the efficiency of the cryocooler, and that investigation of the material behaviour during commissioning of the pressure wave generator be carried out to better understand the operational limits of the diaphragms.

Subjects/Keywords: Cryocooler; cryogenic; flexible diaphragm; metal diaphragm; pressure wave generator

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hamilton, K. A. (2013). Improvements to the Design of a Flexible Diaphragm for use in Pressure Wave Generators for Cryogenic Refrigeration Systems. (Masters Thesis). University of Canterbury. Retrieved from http://dx.doi.org/10.26021/2351

Chicago Manual of Style (16th Edition):

Hamilton, Kent Anthony. “Improvements to the Design of a Flexible Diaphragm for use in Pressure Wave Generators for Cryogenic Refrigeration Systems.” 2013. Masters Thesis, University of Canterbury. Accessed October 20, 2020. http://dx.doi.org/10.26021/2351.

MLA Handbook (7th Edition):

Hamilton, Kent Anthony. “Improvements to the Design of a Flexible Diaphragm for use in Pressure Wave Generators for Cryogenic Refrigeration Systems.” 2013. Web. 20 Oct 2020.

Vancouver:

Hamilton KA. Improvements to the Design of a Flexible Diaphragm for use in Pressure Wave Generators for Cryogenic Refrigeration Systems. [Internet] [Masters thesis]. University of Canterbury; 2013. [cited 2020 Oct 20]. Available from: http://dx.doi.org/10.26021/2351.

Council of Science Editors:

Hamilton KA. Improvements to the Design of a Flexible Diaphragm for use in Pressure Wave Generators for Cryogenic Refrigeration Systems. [Masters Thesis]. University of Canterbury; 2013. Available from: http://dx.doi.org/10.26021/2351


Virginia Tech

2. Seek, Michael Walter. Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method.

Degree: PhD, Civil Engineering, 2007, Virginia Tech

Z-sections are widely used as secondary members in metal building roof systems. Lateral restraints are required to maintain the stability of a Z-section roof system and provide resistance to the lateral forces generated by the slope of the roof and the effects due to the rotation of the principal axes of the Z-section relative to the plane of the roof sheathing. The behavior of Z-sections in roof systems is complex as they act in conjunction with the roof sheathing as a system and as a light gage cold formed member, is subject to local cross section deformations. The goal of this research program was to provide a means of predicting lateral restraint forces in Z-section supported roof systems. The research program began with laboratory tests to measure lateral restraint forces in single and multiple span sloped roof systems. A description of the test apparatus and procedure as well as the results of the 40 tests performed is provided in Appendix II. To better understand the need for lateral restraints and to provide a means of testing different variables of the roof system, two types of finite element models were developed and are discussed in detail in appended Paper I. The first finite element model is simplified model that uses frame stiffness elements to represent the purlin and sheathing. This model has been used extensively by previous researchers and modifications were made to improve correlation with test results. The second model is more rigorous and uses shell finite elements to represent the Z-section and sheathing. The shell finite element model was used to develop a calculation procedure referred to as the Component Stiffness Method for predicting the lateral restraint forces in Z-section roof systems. The method uses flexural and torsional mechanics to describe the behavior of the Z-section subject to uniform gravity loads. The forces generated by the system of Z-sections are resisted by the "components" of the system: the lateral restraints, the sheathing and Z-section-to-rafter connection. The mechanics of purlin behavior providing the basis for this method are discussed in appended Paper II. The development of the method and the application of the method to supports restraints and interior restraints are provided in appended papers III, IV and V. Advisors/Committee Members: Murray, Thomas M. (committeechair), Easterling, William Samuel (committee member), Charney, Finley A. (committee member), Setareh, Mehdi (committee member), Sotelino, Elisa D. (committee member).

Subjects/Keywords: diaphragm; standing seam; through-fastened; cold-formed; component stiffness method; finite element method; lateral bracing; Z-section; purlin; metal building

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Seek, M. W. (2007). Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28357

Chicago Manual of Style (16th Edition):

Seek, Michael Walter. “Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method.” 2007. Doctoral Dissertation, Virginia Tech. Accessed October 20, 2020. http://hdl.handle.net/10919/28357.

MLA Handbook (7th Edition):

Seek, Michael Walter. “Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method.” 2007. Web. 20 Oct 2020.

Vancouver:

Seek MW. Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method. [Internet] [Doctoral dissertation]. Virginia Tech; 2007. [cited 2020 Oct 20]. Available from: http://hdl.handle.net/10919/28357.

Council of Science Editors:

Seek MW. Prediction of Lateral Restraint Forces in Sloped Z-section Supported Roof Systems Using the Component Stiffness Method. [Doctoral Dissertation]. Virginia Tech; 2007. Available from: http://hdl.handle.net/10919/28357

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