Pittsburgh’s Swanson School of Engineering-Research Aimed at Enhanced AM Modeling/Simulation Technology and New AM Qualification Standards

 

Engineers at the University of Pittsburgh’s Swanson School of Engineering were recently awarded two grants with focus on additive manufacturing (AM). One grant will be used to develop enhanced modeling and simulation technology and the other, development of new qualification standards. (For information about both grants, press here.)

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.

We caught up with Albert To, PhD, to share his thoughts and insight about the University’s AM research grants in an AMazing® exclusive Q&A session.

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AMazing®: Thank you Dr. To for your participation. This must be an exciting time with the recent award of two research grants involving additive manufacturing (AM). When we last connected in April of this year, you were involved in a research contract involving computational “latticework” for additive manufacturing. How is the research effort progressing? 

Dr. To: The research on the “latticework” project is progressing nicely. We have been designing and fabricating lattices and testing them to obtain their mechanical properties as a function of the designed density. The structure-property relationships for different lattices will be utilized in the topology optimization tool that we are developing.

(To read Dr. To’s earlier Q&A session regarding computational “latticework” for AM, press here.)

AMazing®: In a recent press release, you mentioned additive manufacturing is at a critical juncture in its evolution, where both computer modeling and qualification methods need to be enhanced to reduce manufacturing times and costs, while improving quality and product integrity. With regard to computer modeling and qualification methods for AM, what needs do these grants address? 

Dr. To: Specific to the project, computer modeling will be used to evaluate the residual stress resulting from the laser-based AM process that we are looking at.  Residual stress can cause failure during fabrication. Being able to predict this by simulating the process can help designers prevent failure of the designed part under consideration.

In terms of qualification methods, the current qualification method is not adequate for determining the quality of an AM part. This is because AM materials are fundamentally different from traditional materials in several ways. First, they have thermal residual stress resulting from the laser melting process. Second, structural flaws and defects tend to show up in AM materials more often than in traditional materials and their sizes and locations are uncertain.

The research that will be conducted by my team will combine modeling and experiments to determine the characteristics of these flaws/defects and residual stress, and their effects on mechanical properties, and then use this new knowledge to develop a better qualification method for AM parts.

Figure IncoBPrismFront: “Top view optical micrograph of an Inconel 718 prism printed with the Optomec LENS 450. Due to the interruption of the printing within the top layer, the alternating printing direction of the hatching for the last two layers can be seen, as diagonal and horizontal lines. Within the final layer (diagonal lines), the printing pattern shows that each subsequent line overlaps with the previous. In the bottom left corner of the prism, where the second to last layer is visible, the contour line at the edges is still partially uncovered.” (Photo courtesy of Erica Stevens, Samples by Jakub Toman and PuZhang)

Figure IncoBPrismFront: “Top view optical micrograph of an Inconel 718 prism printed with the Optomec LENS 450. Due to the interruption of the printing within the top layer, the alternating printing direction of the hatching for the last two layers can be seen, as diagonal and horizontal lines. Within the final layer (diagonal lines), the printing pattern shows that each subsequent line overlaps with the previous. In the bottom left corner of the prism, where the second to last layer is visible, the contour line at the edges is still partially uncovered.” (Samples by Jakub Toman and Pu Zhang. Micrographs courtesy of Erica Stevens)

AMazing®: We understand that enhancing modeling capability may reduce residual stress in complex, sometimes microscopic structures, during manufacturing. How do you propose to reduce modeling errors? 

Dr. To: That’s a great question. Many believe that the modeling errors are mainly due to inaccurate material laws or constitutive relationships that govern the mechanical behavior of AM materials. We will develop an accurate constitutive relationship for the material in order to reduce modeling errors.

AMazing®: How do you propose developing new qualification standards for additive technologies? What areas will you focus on?

Dr. To:  The development will be based on identifying critical flaws using X-ray micro-CT in conjunction with computation.

AMazing®: Besides computer modeling and qualification methods what other critical areas need to be enhanced to further the maturation process for additive technologies?

Dr. To: There are still many critical areas that need to be addressed in maturing AM technologies. For example, how to account for the geometric distortion of parts resulting from the AM process is still a very key issue for AM.

AMazing®: Finally, how will your research be helpful to small and medium size businesses?

Dr. To: It is my hope that the computational tools we develop from the research will help businesses of all sizes to design and qualify AM parts in future.

This concludes our interview. Thank you very much Dr. To. We are grateful for the opportunity to learn about the University of Pittsburgh Swanson School of Engineering’s commitment and advances in additive manufacturing technologies.

Figure IncoBPrismFront: “Top view optical micrograph of an Inconel 718 prism printed with the Optomec LENS 450. Due to the interruption of the printing within the top layer, the alternating printing direction of the hatching for the last two layers can be seen, as diagonal and horizontal lines. Within the final layer (diagonal lines), the printing pattern shows that each subsequent line overlaps with the previous. In the bottom left corner of the prism, where the second to last layer is visible, the contour line at the edges is still partially uncovered.”

Figure InconelD (top): “Scanning electron micrograph of an Inconel 718 prism cross-section printed with the Optomec LENS 450. The regions of lighter color indicate a Nb-rich precursor to the strengthening phase of Inconel 718.” Micrographs by Erica Stevens. Micrograph samples were made with the Optomec LENS 450 by Jakub Toman and Pu Zhang.

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AM_Dr_ToAbout Dr. To
Professor Albert To is currently Associate Professor in the Department of Mechanical Engineering and Materials Science at the University of Pittsburgh. He received his Ph.D. and B.S. degrees from U.C. Berkeley and his S.M. degree from MIT.

Dr. To was a postdoctoral research fellow at Northwestern University prior to joining University of Pittsburgh. His recent research interests include mechanics of AM materials and development of computational methods to support AM such as design optimization and process modeling. In 2009, Dr. To received the prestigious NSF BRIGE award for his early achievement in both research and education.

About the Swanson School of Engineering
The University of Pittsburgh’s Swanson School of Engineering is one of the oldest engineering programs in the United States and is consistently ranked among the top 25 public engineering programs nationally.

The Swanson School has excelled in basic and applied research during the past decade and is on the forefront of 21st century technology including sustainability, energy systems, bioengineering, micro- and nanosystems, computational modeling, and advanced materials development. Approximately 120 faculty members serve more than 2,600 undergraduate and graduate students and Ph.D. candidates in six departments, including Bioengineering, Chemical and Petroleum Engineering, Civil and Environmental Engineering, Electrical Engineering, Industrial Engineering, Mechanical Engineering, and Materials Science.

Contact
Paul A. Kovach

Director of Marketing and Communications Swanson School of Engineering University of Pittsburgh
3700 O’Hara St Benedum Hall Suite 104E
Pittsburgh, PA  15261 USA
Phone: 412-624-0265
Fax: 412-624-1010
Cell: 412-427-9422
pkovach@pitt.edu

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