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Miniature Axisymmetric Streamline Tensile (MAST) Specimen

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Patent application, Filed 1 Apr 2004

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The Navy has a need to test piezoelectric ceramic materials to determine their performance in sonar transducers. Piezoelectric ceramic materials are typically grown as a single crystal, which limits the size of the sample. These materials are very brittle and subject to cracking during use as a transducer. The Navy needs to know the useful life of these materials and the amount of stress that they can be subjected to while still being useful. It also is necessary to determine the electrical properties of the materials and how small flaws in the material affect these properties. No prior art test configuration properly gives this information for piezoelectric ceramics. Tensile testing of ceramic materials using a standard tensile testing machine is not commonly performed because the tensile strength of ceramic materials is typically very sensitive to small cracks. These cracks are almost always present in normally sized specimens. A bend test is more commonly used to determine the transverse rupture strength of a ceramic however, this test does not give the true tensile strength of the material, and the ceramic is subject to failure at the points of load. This patent application discloses a miniature axisymmetric streamline tensile MAST specimen having improved axisymmetric surface profile design and surface stress concentration factor SSCF improvements i.e., close to unity. The MAST specimen also has improved variable curvature transition fillets, miniaturized profile dimension, and shoulder region features used in conjunction with the collet loading method. An axisymmetric, rather than flat, design is preferred since no stress gradients exist in the hoop direction i.e., circumferential direction of the specimen. The MAST specimen is designed to permit various loading options. The MAST specimen may be used for testing any suitable material, including, but not limited to, metals, plastics and ceramics. 6 figures

Subject Categories:

  • Ceramics, Refractories and Glass
  • Test Facilities, Equipment and Methods
  • Electricity and Magnetism
  • Mechanics

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