206840713-Analysis-of-Fracture-in-Porcelain-Enamels.pdf - Analysis of Fracture in Porcelain Enamels by Kyla McKinley Holger Evele Charles Baldwin Ferro

206840713-Analysis-of-Fracture-in-Porcelain-Enamels.pdf -...

This preview shows page 1 - 3 out of 13 pages.

1 Analysis of Fracture in Porcelain Enamels by Kyla McKinley, Holger Evele, Charles Baldwin Ferro Corporation Porcelain enamel is a superior coating material from a thermomechanical perspective, but it is weak in tension because of its ionically-bonded disordered vitreous atomic structure. Porcelain enamel is toughened by being in a residual compressive stress state, and a thorough theoretical understanding of the stress state with supporting experimental data is required for designing enameled ware. A laboratory study comparing the fracture resistance of different ground coat and cover coat combinations where the cover coats are new enamel formulations was done to study the compressive stress state in a multi-coat enamel system using those technologies. 1. Introduction Recently, novel appearances and surface functionality have been formulated into porcelain enamels. 1 New enamel technologies such as metallic finishes and low-temperature cleaning coatings are cover coats that require application over ground coat for adhesion to steel. These finishes are subject to the same strength in compression and weakness in tension as conventional enamels. The residual compression in the low-temperature cover coat is of particular interest for optimization of application to oven cavity interiors, for which single coat systems have been common. Therefore, a study was undertaken to: Review the literature regarding the residual compressive strengthening of cover coats Run a Design-of-Experiment (DOE) study to evaluate the fracture resistance of different ground coat and cover coat combinations Lay the groundwork to bridge the literature model with the capabilities of modern computer finite element modeling (FEM) software to facilitate the optimization of the design of the enameled ware Porcelain enamel-coated metal can be modeled as a glass/metal composite. Glass theoretically has a strength of about ten million pounds per square inch, however, even under the best laboratory conditions, the strength has not been seen at more than a million pounds per square inch. Theoretical strength is based on zero defects in the atomic structure. 2 This is not the case in actual solids where the measured fracture toughness 3 is less than 1 MPa m 1/2 . There are missing atoms or extra atoms that do not create a uniform solid. Therefore, when stress is applied to the solid, the stress is not applied evenly and imperfections of the solid will start to fail. Once one imperfection fails, then surrounding areas bear more stress on them and eventually start to fail as well. The enamel is toughened by being in a state of residual compression from having a lower coefficient of thermal expansion, α e , than the steel. The residual compressive stress state and fracture resistance of porcelain enamel have been investigated using the following approaches:
Image of page 1

Subscribe to view the full document.

2 1) Thermal expansion curves which provide data to mathematically estimate the stress states.
Image of page 2
Image of page 3
  • Fall '19

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Ask Expert Tutors You can ask 0 bonus questions You can ask 0 questions (0 expire soon) You can ask 0 questions (will expire )
Answers in as fast as 15 minutes