Doctor of Philosophy, The Ohio State University, 2014, Industrial and Systems Engineering

Precision glass molding is a net-shaping process to fabricate glass optics by replicating optical features from precision molds to glass at elevated temperature. The advantages of precision glass molding over traditional glass lens fabrication methods make it especially suitable for the production of optical components with complicated geometries, such as aspherical lenses, diffractive hybrid lenses, microlens arrays, etc. Despite of these advantages, a number of problems must be solved before this process can be used in industrial applications. The primary goal of this research is to determine the feasibility and performance of nonconventional optical components formed by precision glass molding. This research aimed to investigate glass molding by combing experiments and finite element method (FEM) based numerical simulations. The first step was to develop an integrated compensation solution for both surface deviation and refractive index drop of glass optics. An FEM simulation based on Tool-Narayanaswamy-Moynihan (TNM) model was applied to predict index drop of the molded optical glass. The predicted index value was then used to compensate for the optical design of the lens. Using commercially available general purpose software, ABAQUS, the entire process of glass molding was simulated to calculate the surface deviation from the adjusted lens geometry, which was applied to final mold shape modification. A case study on molding of an aspherical lens was conducted, demonstrating reductions in both geometry and wavefront error by more than 60%. In addition, mold materials and mold fabrications were explored as molds are crucial for fabrication of different freeform optics. The research for the first time demonstrated the use of graphene-coated silicon as an effective and high-performance mold material for precision glass molding. It was shown experimentally that Si-glass adhesion could be completely avoided by using the carbide-bonded graphene coating on Si m (open full item for complete abstract)

Committee: Allen Yi (Advisor); Jose Castro (Committee Member); James Lee (Committee Member) Subjects: Engineering; Experiments; Industrial Engineering; Materials Science; Mechanical Engineering

Master of Science, The Ohio State University, 2014, Industrial and Systems Engineering

Over the past decades Precision Glass Molding (PGM) technology has been used to manufacture high-quality infrared lenses with surfaces ranging from simple conics to complex aspheric. Since most of the infrared lenses utilize chalcogenide glasses including germanium, which is expensive as a raw material, the use of near net shape process like Precision Glass Molding Process as a cost effective process to eliminate material waste is necessary. In this case, Finite Element Analysis (FEM) is a tool that can simulate the PGM process and help designers to predict the appropriate mold geometry that can form the desire surface lens profile. This tool can also anticipate residual stress of the molded lens that can result in an inhomogeneous refractive index that directly affects the optical performance of the lens. As can be seen in the market, there is a lot of commercial FE software like ABAQUS, MSC MARC, ANSIS, DEFORM, and etc., that can be used to simulate the PGM process that each has its own advantages and disadvantages. In this case, a fair evaluation of software would be helpful for FEM users. This thesis starts with an understanding of glass properties as a fundamental to establish a model by FE software. To have an understanding of glass behavior, glass properties like glass viscoelasticity, glass viscosity and glass transition temperature and other related glass properties should be studied. The study of manufacturing process of an infrared lens by using a commercial glass molding machine, GP-10000HT, is the second step to figure out all the details of a real precision glass molding process that help us to provide a simulation that makes a better prediction of glass molding process. By having a good understanding of material properties as well as manufacturing process of glass molding process, the numerical modeling of PGM process by using two commercial FE software, MSC MARC and ABAQUS, is another approach of this thesis. These two numerical modeling are de (open full item for complete abstract)

Committee: Allen Yi (Advisor) Subjects: Engineering; Optics