To develop standard qualification methods for AM, "Multiscale Structure-Mechanical Property Investigation of Additive Manufactured Components for Development of a Reliable Qualification Method" is a three year, $300,000 grant funded by the National Science Foundation's Division of Civil, Mechanical and Manufacturing Innovation (CMMI). To address the modeling and simulation challenge, "Automation Tools for Modeling AM Process of Complex Geometries in ABAQUS" was awarded $150,000 Research for Additive Manufacturing in Pennsylvania (RAMP) grant, funded jointly by the Pennsylvania Department of Community and Economic Development's (DCED) "Discovered in PA, Developed in PA" program and America Makes (National Additive Manufacturing Innovation Institute).
Principal investigator for both grants is Albert To, PhD, associate professor of mechanical engineering and materials science; and co-PIs are Minking K. Chyu, PhD, the Leighton and Mary Orr Chair professor of materials science and mechanical engineering, associate dean for international initiatives and dean of the Sichuan University – Pittsburgh Institute; and Markus Chmielus, PhD, assistant professor of mechanical engineering and materials science. RTI International Metals Inc. of Pittsburgh will partner with Pitt on the RAMP grant.
According to Dr. To, AM is at a critical juncture in its evolution where both computer modeling and qualification methods need to be enhanced in order to reduce manufacturing time and costs while improve quality and product integrity.
"Additive manufacturing continues to demonstrate its ability to manufacture very complex lattice structures and geometries, enabling us to build complex structures that would be difficult to replicate using traditional or "subtractive" manufacturing," Dr. To says. "However, these increasingly complex parts are very time-consuming to model and therefore more prone to errors. The RAMP grant will enable us to develop computer codes that first will automate the finite element simulation of certain AM process and material.
"By improving the modeling of these complex, sometimes microscopic structures, we can design the process path and/or part geometry to reduce residual stress that causes failure to the part during manufacturing."
Improving the modeling and simulation processes in additive manufacturing go hand-in-hand with developing new qualification methods that ensure the quality of a manufactured part or component. Dr. To notes that additive manufacturing has advanced so rapidly that typical manufacturing standards have yet to catch up.
"Traditional qualification standards are not adequate for additive manufacturing because AM parts are "built" by adding layer upon layer of powdered ceramics, metals and polymers, which therefore exhibit residual stresses and higher number of defects," Dr. To says. "For example, in aerospace manufacturing, a machined part is inspected for surface cracks, dimensional accuracy, and material composition. To develop qualification methods for AM components, we need a better understanding of the microstructure and its mechanical behavior."
Accomplishing this, Dr. To explains, begins with the use of a common medical device – X-ray micro computerized tomography, or a CT scan. In conjunction with mechanical testing and computer simulation, this will enable the researchers to investigate at the microscopic level the mechanical effects of flaws and residual stress, and later develop a computer-based, non-destructive method that is rapid, reliable, and affordable, thereby greatly improving AM techniques and quality.
"Additive manufacturing is poised to revolutionize the production of complex and distinctive parts and machines, but like its predecessor it requires the qualification methods necessary to ensure viability, safety and integrity," Dr. To says. "We are quite literally building the foundation for a 21st century manufacturing revolution."
Provided by University of Pittsburgh
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