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About Our Research
Lightweight structures are going to be the key to energy savings needed for the environment’s sustainability. Vehicles of tomorrow will have a high percentage of multi-material joints and composites. This change could be evolutionary or disruptive, but the need for new ways of making things is imperative. For over 20 years, development of novel manufacturing processes has been the main focus of Glenn Daehn's research group. Impulse based metal working and metallurgy (ceramic matrix composites, castings, and high strain rate behavior of materials) form the two main thrust areas of the group. The group expertise also consists of building pulsed power equipment and high velocity measurement devices such as the Photonic Doppler Velocimeter. Being affiliated with the Materials Science and Engineering Department at The Ohio State University, the group also has access to world-class microscopy (CEMAS) and material testing facilities.
-Impulse Manufacturing Lab Introduction
Forming, cutting and welding of metal by impulse has significant advantages, in that short time scales change the fundamental nature of the forming process and short duration impulses can enable much lighter and more agile equipment because large static forces do not need to be resisted. Increased forming limits, reduced springback, low cost tooling and reduced wrinkling are some of the documented advantages of impact forming. Shearing at high speeds has been shown to reduce sliver formation and provide increased dimensional tolerance. There is also a critical velocity above which shearing requires much less energy because of localized deformation along narrow adiabatic shear bands. Welding is a solid state process that allows the joining of dissimilar metals with little to no heat affected zone. A common observation in impact welding has been that the weld zone is stronger than the parent material. The group useselectromagnetic force, rapidly vaporizing conductors and dielectrics, and pulsed laser as tools for developing short-duration, high-magnitude impulses. Click to get more information on impulse forming.
High strain rate behavior of materials
Many problems exist today in engineering that concern materials deformation at high strain rates, in areas as diverse as high speed machining, automobile crash-testing, space vehicle and satellite protection, and numerous aspects of national security. In order to solve these problems, constitutive models and failure criteria have to be established and validated to describe the deformation behavior of materials under the conditions of interest. Through collaborative experimental and numerical modeling work this group has been actively pursuing this area of research. Fully instrumented ring expansion (FIRE) test has been developed to formulate constitutive properties of materials in the strain rate regime of 102-106/s. Previous work in the group has also focused on developing forming limit diagrams for various structural metals during high velocity forming.
Ceramic Matrix Composites and Castings
Typically, combining multiple materials to create lightweight high performance composites results in additional processing and material cost, limiting their widespread adoption. We create high performance composites utilizing a low cost method through the reactive transformation of silica with aluminum into a co-continuous network of aluminum and alumina. Silica parts are created using slip casting, injection molding, and other traditional processes. The transformation in molten aluminum is a near net shape process resulting in a composite part requiring minimal machining. Additionally, properties can be tailored for applications using additions of other particulates such as SiC, B4C, etc to improve wear, hardness, density, stiffness, and thermal performance. Final composite density ranges from 3-3.5 g/cc making them competitive with aluminum MMC’s and an attractive alternative to heavy cast iron and steels (7-8 g/cc).