ADAPT researchers Nathan Johnson (PhD candidate), Dr. Cheikh Cissé (postdoctoral scholar), Prof. Mohsen Asle Zaeem and Prof. Aaron Stebner are co-authors on a paper published in the most recent issue of Science.
“Fatigue-resistant high-performance elastocaloric materials made by additive manufacturing” appears in the November 29 issue (Vol. 366, Issue 6469) on page 1116.
The article documents the additive manufacturing of a highly efficient and eco-friendly elastocaloric cooling material composed of several different phases made from nickel and titanium. The work is the result of a collaboration led by researchers from the University of Maryland, together with Ames Laboratory, Colorado School of Mines, Xi’an Jiaotong University and Iowa State University.
The key finding of the research is that while elastocaloric materials typically used for solid-state cooling show a degradation in cooling behavior after hundreds of cycles, laser melting these metals creates fatigue-resistant nanocomposite microstructures that can cycle, with consistent cooling capacity, a million times.
ADAPT’s role in this research is directly related to other work the consortium has done on shape memory alloys, specifically nickel–titanium (NiTi). Nathan Johnson conducted the in situ diffraction work, and Cheikh Cissé performed the finite element modeling. X-ray diffraction was used on the additively manufactured samples to verify that phase transformation was happening, was reversible and was not changing its behavior through many cycles. It was also used to verify different phases in the material that made up the nanocomposite microstructure.
Cooling technology, used in refrigeration and HVAC systems around the globe, is a multibillion dollar business. Vapor compression cooling, which has dominated the market for more than 150 years, has not only plateaued where efficiency is concerned but also uses chemical refrigerants with high global warming potential.
Solid-state elastocaloric cooling, where stress is applied to materials to release and absorb (latent) heat, has been under development for the last decade and is a front-runner in alternative cooling technologies. Shape memory alloys are found to display a significant elastocaloric cooling effect; however, the presence of hysteresis—work lost in each cycle and the cause of materials fatigue and eventual failure—remains a challenge.
To that end, an international team of collaborators led by UMD Materials Science and Engineering Professor Ichiro Takeuchi has developed an improved elastocaloric cooling material using a blend of nickel and titanium metals, forged using a 3D printer, that is not only potentially more efficient than current technology, but is completely “green.” Moreover, it can be quickly scaled for use in larger devices.
Takeuchi said, “Dr. Stebner’s expertise played a crucial role in developing understanding of the fundamental mechanism behind fatigue-resistant behavior of additive manufactured shape memory alloys. His group’s in situ synchrotron diffraction and finite element modeling capabilities gave us unique insight into the inner workings of the material.”
Read the University of Maryland’s release on this paper’s publication at https://www.umdrightnow.umd.edu/news/umd-led-team-creates-novel-material-potentially-offers-efficient-eco-friendly-advance-cooling.
Access the abstract at https://science.sciencemag.org/content/366/6469/1116.abstract.
To access the full text of the paper as published, log in at https://science.sciencemag.org/content/366/6469/1116.full using your AAAS, OpenAthens, or Shibboleth credential. You can also purchase digital access or a print issue of this issue of Science.
Supplementary materials from the paper can be downloaded at https://science.sciencemag.org/content/suppl/2019/11/25/366.6469.1116.DC1.
Research on process–structure–property relationships tied to earliest questions when ADAPT consortium formed
A research paper on ADAPT-led investigations into heat treating additively manufactured Inconel 718 parts is in revision with the journal Additive Manufacturing and is available as a preprint via Arxiv.
“Knowledge of Process–Structure–Property Relationships to Engineer Better Heat Treatments for Laser Powder Bed Fusion Additive Manufactured Inconel 718” documents work done by Thomas G. Gallmeyer, Senthamilaruvi Moorthy, Branden B. Kappes, Michael J. Mills, Behnam Amin-Ahmadi and Aaron P. Stebner.
ADAPT Executive Director Aaron Stebner recalled how this research started: “When ADAPT began in 2016, one of the first big questions from our members was, ‘Are we heat treating parts the right way?’ Generally, standards in industry at that time recommended that additive Inconel 718 parts should be heat treated the same way as traditionally manufactured parts.”
Then, in 2017, researchers from Lawrence Livermore National Laboratory published research that indicated that additively manufactured 316L stainless steels could perform better than traditionally manufactured materials. Their 2018 article in Nature Materials, “Additively Manufactured Hierarchical Stainless Steels with High Strength and Ductility,” documented that the dislocation cells that result from the AM process augment grain structures and result in improved strength and ductility.
“We knew the same dislocation cells form in additively manufactured Inconel 718,” said Stebner. “But you don’t have to heat treat 316 stainless steel, and after heat treating Inconel parts the usual way, those dislocation cells were no longer there. Heat treating Inconel 718 the same way as traditionally manufactured parts removed the dislocation cells and the benefits they provided, even as it precipitated out secondary phases that enhanced high-temperature strength.”
The question became: Can we heat treat Inconel 718 in a way that retains the dislocation cells and still precipitates out secondary phases to improve strength and ductility? And how?
“The answer is, yes,” said Stebner. “We can do it, and we get better strength and ductility compared to both AM and forged parts heat treated the traditional way using a nominal, slightly cooler heat treatment approach.” This work also explains a German research team’s previous findings of better high-temperature creep performances in additively manufactured Inconel 718 using slightly modified heat treatments.
In the next phase of this work, ADAPT will examine if the low-cycle fatigue operating temperatures of Inconel 718 parts can be increased as a result of this new knowledge. If it could, Inconel 718—which is known to be easier to process than other higher temperature nickel-based alloys and is less expensive—would be used in more applications. For example, Inconel 718 parts made using AM and heat treated in this new way can be used closer to the core of turbine engines because they can better withstand the stresses of that location.
Another finding will likely tie into Metallurgical and Materials Engineering Associate Professor Jeff King’s research on how radiation affects AM parts. Since nuclear operations are at high temperatures—around 500–600 °C, right at the upper temperature limit of Inconel 718—enabling Inconel to operate at 650 °C “will be a big win for nuclear applications,” said Stebner. “There is also an opportunity to look at radiation and elevated temperature and how the combination of both impacts the strength and lifespan of AM parts.”
An important part of this research was the collaboration with The Ohio State University to look at sample material from additively manufactured Inconel parts on a special electron microscope in Columbus. That device allowed Behnam Amin-Ahmadi to see some of the effects the modified heat treatment has at the atomic scale. “We don’t have a microscope that is aberration-corrected and capable of seeing the aluminum/niobium co-precipitate that adds strength even at high operating temperatures,” noted Amin-Ahmadi. “Fortunately, we were able to use the state-of-the-art microscope on campus in Columbus to see those formations within the AM structure. We’re grateful to our colleague Michael J. Mills at Ohio State for that access.”
Multi-organizational, interdisciplinary work advances workforce development and retraining
ADAPT faculty Sam Spiegel, Xiaoli Zhang and Craig Brice are leading teams recently awarded National Science Foundation grants to
Mines is one of five U.S. universities to receive NSF PEER (Production Engineering Education and Research) awards, designed to advance the workforce for future needs through a convergent science approach that integrates knowledge, methodology and expertise from different disciplines.
The learning platforms developed by PEER awardees will be online courseware, an increasingly prevalent educational tool that has received comparatively little study due to its recent emergence. In addition to developing new platforms, PEER awardees will study the effectiveness of online courseware, finding out what connects best with learners at various levels of skills in several different environments.
NSF’s PEER program is made possible in part by a $10 million gift from The Boeing Company. The Mines team is led by Sam Spiegel, director of the Trefny Innovative Instruction Center, and includes Brice, director of the Advanced Manufacturing program, and other faculty from Mines, Red Rocks Community College and Colorado Community College Online. The team will focus its attention on data science in advanced manufacturing by developing adaptive learning progressions that assess and advance current workers as well as students at community colleges and universities. This program builds from the Trefny–ADAPT partnership established for additive manufacturing workforce development, outreach and training through the Department of Defense Office of Economic Adjustment (DOD-OEA) Mountain West Advanced Manufacturing Network program, which began in January 2017 and is now in phase II.
Displaced Worker Retraining
Another Mines team led by Xiaoli Zhang, associate professor of mechanical engineering, was one of 43 awardees in NSF’s pilot Convergence Accelerator program. The awards, totaling $39 million, will support projects across the country that will find new ways to apply Big Data to science and engineering and create technologies that can enhance the lives of American workers.
The Mines team will focus on retraining workers displaced by changes in industry attributed to the proliferation of advanced manufacturing. “The fourth industrial revolution is here,” said Zhang, “and while AI is assisting people in many ways, it and other advanced technologies may replace humans in some job scenarios.”
This “fourth industrial revolution” is expected to impact tens of thousands of jobs—mostly engineers—between 2020 and 2060. The Mines team will create proactive AI-enabled tools aimed at curbing this looming workforce displacement crisis by developing algorithms that will automatically assess skills and gaps, then generate individualized retraining plans to quickly prepare workers for new jobs.
Traditional retraining programs can be time-consuming and costly to develop. They also tend to treat all trainees the same, without regard to their age, experience or specialized knowledge.
The work in process by Zhang as principal investigator, supported by Brice, Spiegel, Sridhar Seetharaman (ADAPT Board Member), Aaron Stebner (ADAPT Executive Director), and others, aims to create an AI-enabled approach to training that enables fast, fair, cost-effective and customized training at scale. Each worker will benefit from a tailored training approach based on their skills, interests, experience and best fit for a new role.
One of the greatest promises of additive manufacturing is enabling new technologies, especially new paradigms in functional complexity.
A big limitation of shape memory alloys (SMAs) like nickel–titanium (NiTi) is that their unique characteristics only work with relatively simple, axially symmetric shapes like tubes and square stock. Conventional NiTi SMAs require cold work to achieve the proper superelastic behavior; while additive manufacturing could enable more complex part geometries, postprocessing requirements like cold work negate AM as a reasonable processing method.
ADAPT collaborated with NASA Glenn Research Center (GRC) and ADAPT member Confluent Medical Technologies to develop 38 wrought NiTiHf SMAs for custom functional performance. These compositions cover a range of functional performances, including high-temperature actuators, biomedical implants and ultra-dent-resistant bearing materials. Funding for the work was provided by NASA GRC, Confluent and the National Science Foundation.
These alloys, which use hafnium as a strengthening precipitate, hold the promise of requiring only heat treatment to attain functional shape memory performance. This opens the door to using AM to fabricate metal parts with shape memory characteristics and geometries that are far more complex than those made with conventional NiTi alloys.
Compared with the cold work required to add strength to NiTi, new NiTiHf alloys reach high strength and superelasticity through the formation of H-phase precipitates without cold working. These alloys can therefore be good candidates for using AM for SMAs.
Our researcher of the month, Dr. Behnam Amin-Ahmadi, has collaborated with NASA and Confluent to apply different chemical compositions and heat treatments to NiTiHf alloys to achieve the desired mechanical properties and martensitic transformation temperatures. The microstructures of these alloys have been investigated in detail using advanced microscopy techniques, such as scanning electron microscopy (SEM), focused ion beam (FIB), electron backscatter diffraction SEM (EBSD-SEM), high-resolution transmission electron microscopy (TEM), scanning TEM (STEM), and STEM with energy-dispersive X-ray (EDX) analysis, among others. These fundamental studies reveal the responsible mechanisms affecting transformation temperature, superelasticity and plastic deformation in these alloys.
The second part of Amin-Ahmadi’s project focuses on optimizing process parameters for AM NiTiHf and characterizing 3D-printed parts in detail along with two students that he is mentoring: ADAPT PhD student John (Charlie) Fuller and undergraduate research assistant Katerine (Katya) Flaska.
Once ideal alloy compositions were identified, two more ADAPT members contributed to the work: ATI Specialty Materials made the compositions in bulk powder (with cost share from ATI and funding from the Colorado Office of Economic Development and International Trade), and Elementum 3D printed test parts for characterization work in the ADAPT lab.
The use of AM with NiTi-X alloys removes the limitations of conventional NiTi SMAs and enables more complex parts, promising a new realm of applications for SMAs not only in the biomedical field but also in aerospace, automotive and wind energy applications.
ADAPT PhD student Thomas Gallmeyer won the Best Paper Award at GVSETS 2019. The 11th annual GVSETS & APBI (Ground Vehicle Systems Engineering and Technology Symposium and Advanced Planning Briefings for Industry) was hosted by the Michigan chapter of the National Defense Industrial Association Aug. 13–15 in Novi, Michigan.
Tom’s paper is titled “Systematic Development of Framework for Validation and Performance Quantification of Additively Manufactured (AM) Replacement Parts for Structural Steel Applications.” Co-authors include Jinesh Dahal, Branden Kappes, Aaron Stebner, Ravi Thyagarajan, Juan Miranda, Adam Pilchak and Jacob Nuechterlein. Funding for the research was provided by the U.S. Army CCDC Ground Vehicle Systems Center.
GVSETS & APBI brings together more than 1,000 executives, program managers, engineers, and key decision-makers to discuss and collaborate technology, initiatives, programs and plans in the ground domain. Through its program of presentations, panel discussions, speakers, exhibits, technical paper presentations and one-on-one meetings with Army Ground Systems decision makers, GVSETS & APBI is a unique opportunity for the community to come together to shape the future success of the nation’s Warfighters.
ADAPT welcomes new member First RF Corporation! Located in Boulder, Colorado, First RF is an advanced technologies company specializing in antennas and radio frequency (RF) systems. As a product-focused company, they provide their customers with concept-to-deployment support through their Technologies and Manufacturing divisions. First RF offers cutting-edge applied R&D capabilities by exploring, maturing, and applying new technologies into product designs.
ADAPT Executive Director Aaron Stebner spent the summer as a visiting researcher at the International Center for Young Scientists (ICYS) at the National Institute for Materials Science in Tsukuba, Japan. Read the interview about Stebner’s research and his views on the future of materials.
Jeff King and team explore radiation’s impact on additively manufactured stainless steel and Inconel
The use of additive manufacturing (AM) for mission-critical applications is often limited due to a lack of characterization and property data, which is necessary to meet quality assurance requirements. The nuclear industry is no exception. Data is needed on the performance of AM parts during irradiation in a nuclear reactor to ensure that they can survive and function as intended in challenging nuclear energy environments.
Dr. Jeffrey King and his team at Colorado School of Mines are collecting irradiation performance data for stainless steel (SS) and Inconel samples from billets produced using different AM techniques, including laser powder bed fusion, laser free-form fabrication, and electron beam wire feed. Mines is conducting pre-irradiation thermomechanical testing (tensile strength, yield strength, elastic modulus, ductility, thermal conductivity and thermal diffusivity) and microstructural characterization of the unirradiated specimens. Mines is uniquely positioned to research this area with its strong materials background and interdisciplinary nuclear program as well as with the work of the Nuclear Science and Engineering Center (NuSEC) and ADAPT.
“We’re not the first to do this, but we’re close,” said King. Bombarding metals with neutrons causes physical changes, typically making metals harder but more brittle, or more likely to break suddenly. King’s research examines how additively manufactured parts might perform in a reactor environment compared to conventional parts. “We hope to show AM materials where strength goes up or stays the same and ductility does not go down,” noted King.
AM could benefit the nuclear industry in several ways. Additive processes could be used to create novel geometries for components that improve reactor performance, such as filters or fuel elements. Additionally, given that most nuclear plants are decades old, there are critical parts, such as valves, that are no longer made and that are expensive to replace. This issue is also common in the military, as investigated in ADAPT’s hinge redesign program with the U.S. Army’s CCDC Ground Vehicle Systems Center (previously named TARDEC). AM could enable single replacements of reactor parts to be made at reasonable cost with short turnaround time.
The Advanced Test Reactor (ATR) at Idaho National Laboratory irradiated a set of specimens produced by Dr. King’s group. The ATR is the highest-power research and testing reactor in the United States. It has a fraction of the power of most commercial nuclear plants, but 10 times their neutron flux. The effects of that flux on AM metal parts are what King and his colleagues hope to observe.
Thermomechanical testing and microstructural characterization of the irradiated specimens will begin soon at the Low Activation Materials Design and Analysis (LAMDA) facility at Oak Ridge National Laboratory and the Nuclear Science User Facilities (NSUF) at Idaho National Laboratory.
A comparison of the physical properties and microstructure of the irradiated specimens to those of the as-fabricated specimens will provide insight into the viability of AM parts for nuclear reactor applications. It will also identify key areas of concern for further technology development efforts and provide data for future computational model development.
The NSUF continues to provide funding and facility support for this project. For more on Jeffrey King, visit https://metallurgy.mines.edu/project/king-jeffrey/.
Mines’ Advanced Manufacturing Program Director Craig Brice and several of his students worked with Adam Savage on an episode of “Savage Builds,” a brand-new series premiering on the Discovery Channel on June 14. The series is all about extreme and innovative engineering challenges.
Brice partnered with ADAPT member company EOS to design and build a 3D-printed titanium suit of armor inspired by the Iron Man films. But Savage and the team didn’t stop there—with the help of a customized Gravity Jet Suit designed by Richard Browning’s Gravity Industries, the suit actually flew.
Pictured to the right is the full titanium suit, and above, Craig Brice shakes the Iron Man–gloved hand of show creator Adam Savage. The glove represents about 25 of the approximately 250 3D-printed pieces that went into the suit. Brice’s project was chosen for the premier episode, which airs on June 14 on the Discovery Channel. Read an interview with Brice that outlines the details of the project, and check out these teaser videos from Savage’s Instagram feed: Brice outfitting Savage with glove pieces, and the suit flight test.
Post-show “behind the scenes” video: https://www.cnet.com/news/adam-savage-tests-an-iron-man-suit-that-really-flies-go-behind-the-scenes/
NASA’s investment helps improve 3D metal printing for aviation
NASA, as part of its Aeronautics Research Mission Directorate (ARMD), selected three university-led teams last month to explore new ways to build and power the aircraft of the future. Colorado School of Mines and ADAPT are part of a team led by the NextManufacturing Center at Carnegie Mellon University (CMU) to explore new ways to use additive manufacturing to reduce costs and increase the speed of mass-producing aircraft without sacrificing quality, reliability, and safety.
This is the second year NASA has asked the academic world to help it achieve its strategic goals through the University Leadership Initiative (ULI). The three teams (including groups from University of Wisconsin–Madison and University of Illinois at Urbana-Champaign), will receive about $15 million over three years. Almost $7 million of that will go to the team led by NextManufacturing.
The ULI was created to initiate a new type of interaction between ARMD and the university community, where U.S. universities take the lead, build their own teams, and set their own research paths. This initiative seeks new, innovative ideas that can support the NASA ARMD portfolio and the U.S. aviation community.
The NextManufacturing-led project, Development of an Additive Manufacturing Ecosystem for Qualification of Additive Manufacturing Processes and Materials in Aviation, is led by Dr. Anthony Rollett, with a number of co-investigators from CMU, Colorado School of Mines, Case Western Reserve University, University of Pittsburgh, University of Texas at El Paso, Worcester Polytechnic Institute, The Barnes Group, and Materials Resources LLC. Other partners will include the Air Force Research Laboratory’s Materials and Manufacturing Directorate, Argonne National Laboratory, ANSYS, Lockheed Martin, Trumpf, Eaton, General Electric, Pratt & Whitney, Northrop Grumman, Materials Solutions, Metal Powder Works, and Siemens.
The project will focus on process qualification for laser powder bed fusion 3D printing. The aim is to lower the cost of manufacturing, especially for short-run production and replacement parts, and to encourage economic growth by enabling small contractors to qualify their AM processes and equipment.
Mines/ADAPT researchers, including Drs. Owen Hildreth, Branden Kappes, Aaron Stebner, Craig Brice, and Behnam Amin-Ahmadi, will work with ADAPT member company Citrine Informatics to use machine learning to characterize and qualify additively manufactured parts and to help overcome the challenge of creating a scientifically sound basis for qualifying 3D printed parts. This is an important step toward demonstrating how to design and use facilities for efficient, large-scale production of these parts.
ULI provides the opportunity for university teams to exercise technical and organizational leadership in proposing unique technical challenges, defining interdisciplinary solutions, establishing peer review mechanisms, and applying innovative teaming strategies to strengthen the research impact. By addressing the most complex challenges associated with ARMD strategic thrusts, universities will accelerate progress toward achieving high-impact outcomes while leveraging their capability to bring together the best and brightest minds across many disciplines. To transition their research, Principal Investigators (PIs) are expected to actively explore transition opportunities and pursue follow-on funding from stakeholders and industrial partners during the award.
An opportunity for ULI Round 3 is now open in NSPIRES.
Earlier this year, ADAPTSM and Citrine Informatics completed Phase I and applied for Phase II funding for ongoing research for the Naval Sea Systems Command (NAVSEA), the largest of the U.S. Navy’s five systems commands. With 74,000 civilian, military and contract support personnel, NAVSEA engineers, builds, buys and maintains the Navy’s ships, submarines and combat systems.
Since it is impractical to use high-fidelity, destructive instruments to analyze additively manufactured parts in the field (e.g., micro X-ray computed tomography, electron microscopy, tensile testing, etc.), the program’s research is focused on developing a machine learning platform that correlates statistics from such high-fidelity, destructive test results with signals from low-fidelity, nondestructive test approaches. When completed, this platform will provide Navy personnel in the field a reliable way to evaluate new or in-service parts to determine if they are at risk of failure and/or to determine the expected life remaining on additively manufactured parts.
Phase I showed that the platform can automatically upload and analyze mechanical testing and X-ray computed tomography (XCT) data, and that models can be built to statistically determine the effects of pore defects on the strength and stiffness of AM Inconel 718 samples. It also laid the foundation to generate and incorporate nondestructive ultrasonic and radiographic testing data, as well as fatigue performances, into the statistics-based framework.
The model will enable fast, predictive evaluation of the quality of AM-built parts, when they are printed and as they degrade in service, using nondestructive methods. It will be created using machine learning to establish relationships between low-fidelity, nondestructive tests and high-fidelity, destructive tests.
Phase I began with completing XCT and mechanical property characterizations, generating nondestructive test data, and training XCT-ultrasonic and radiographic models for Inconel 718. It is proposed to expand the framework to quantify effects of defects in other alloy classes like titanium and stainless steel, and other types of defects, such as grain size, texture and dislocation morphologies.
The proposed three-year continuation program’s final deliverable will be a web-based software platform that will generate and update models for Navy engineers to transform raw nondestructive testing data into quantitative prediction of part performance in minutes, with visualization and plotting tools to report the information. This tool will also be available to ADAPT member companies for use and critique as it is being developed through the adapt.citrination platform.
In April, the ADAPTSM Center hosted Senator Cory Gardner of Colorado as part of his visit to Colorado School of Mines.
Discussion focused on the future of manufacturing shifting to a network-based, on-demand model enabled by additive manufacturing (AM). Such a model can democratize manufacturing, help the country adapt to shifting manufacturing needs, and impact military readiness.
An important part of preparing for this shift is a new partnership with Prof. Steve Simske at Colorado State University to bring cyber-physical security to manufacturing networks and supply chains and to address forgery concerns.
Sen. Gardner’s American Innovation and Competitiveness Act, enacted during President Obama’s term, has benefited ADAPT’s work and funding. ADAPT Executive Director Aaron Stebner and other ADAPT leadership shared details about the TARDEC program, including MAXXPRO/MRAP part replacement and supply chain simplification; the Quality Made program to develop a laser hot wire system that builds in process control with integrated machine learning for flexible, large-scale manufacturing; and ADAPT’s DOD-OEA program.
See Sen. Gardner’s full statement on his Mines visit here:
The ADAPTSM Center’s work on behalf of the US Department of Defense Office of Economic Adjustment (DoD OEA) began in 2017 and has been extended into 2020. This collaborative effort with the University of Utah, Colorado School of Mines, and Carnegie Mellon University is focused on diversifying the manufacturing supply chain of the future.
A key part of the project, both in Colorado and Utah, is educating manufacturers – especially defense contractors – about metal AM. A strong foundation of metal AM knowledge and capability offers a path to economic resilience for manufacturers. AM provides flexibility to enable manufacturers to diversify and gives the DoD a way to build a more resilient defense supply chain based on AM.
“This collaboration sets the foundation of how we diversify the manufacturing supply chain of the future,” emphasized ADAPT Executive Director Aaron Stebner. “We’re moving away from the assembly line to a distributed network of AM machines. That promotes a more even keel for the defense manufacturing supply chain and provides opportunities for others to get involved.”
One example of the potential AM holds is the redesign of the MRAP hinge assembly for the Army’s TARDEC group featured in last month’s ADAPT newsletter.
Through workshops and training sessions, ADAPT and the collaborating institutions on the DoD OEA program have been able to help local manufacturers. “We invite them to learn about the technical and business case for using metal AM to enhance and diversify their businesses,” said Bart Raeymaekers, project lead with University of Utah. “That helps make their companies and the workforce as a whole more resilient and able to deal with the ups and downs in defense spending.”
In Utah, work with Hill Air Force Base has focused on new approaches to keep the aging A-10 Warthog and the brand-new F-35 Lightning II fleets in the air. “The supplier that made a part may no longer exist, or we may have better ways to build a part today than when the plane was originally manufactured. Using AM is proving effective in sustainment for old aircraft and in field repairs for very new aircraft,” said Raeymaekers.
Together, the team is printing parts with titanium and Inconel using different process parameters to characterize material and mechanical properties, which are stored in a cloud-based database. Machine learning algorithms from Citrine Informatics then mine the database produced.
The result is data-driven models that can direct future research. “It takes a lot of trial and error to tune process parameters for a metal AM process to produce parts with the desired properties,” said Raeymaekers. “We’re working to use machine learning to accelerate that work. Usually, we work to understand the physics and then capture that in a mathematical model. With machine learning, we build models based on large data sets.”
Another key focus of this collaborative approach is exploring how machine learning and data analytics can enhance communication across the supply chain. The data-driven approach allows technicians to share information with R&D engineers, and engineers to share their discoveries with technicians, without the significant communication gaps that often muddy that part of the process.
Phase 1 of the DoD OEA program has proven successful enough that Phase 2 funds were awarded based on the progress achieved in Phase 1. That extends the work of ADAPT, Citrine, Colorado School of Mines, University of Utah, and Carnegie Mellon University, along with the University of Utah MEP Center, to July 2020. The results achieved through the TARDEC project, initiated by Fort Carson in Colorado, created an opportunity to discuss ways to apply AM to help Peterson Air Force Base with some specific needs as the project moves into Phase 2.
The efforts in the DoD OEA program have ranged from granular research – Carnegie Mellon’s work to understand the fundamentals of porosity in AM builds, why it happens, where it comes from, and how to control for and avoid it – to strategic questions of the nation’s defense supply chain and diversifying and increasing resiliency of supply chains for all of manufacturing. This important work continues to demonstrate the potential of AM.
Accelerating Additive Process Qualification with Redesigned Hinge Replacements
In 2007, in response to a growing threat of IEDs (improvised explosive devices) in the Iraq War, the U.S. Department of Defense began a program to produce Mine-Resistant Ambush Protected (MRAP) light tactical vehicles. At some point, in response to changing threats in the field, the cab doors were modified to add a 400-lb. armor plate to the existing 800-lb. design to better protect people inside the trucks.
Unfortunately, this up-armoring added weight that tested and often exceeded the strength of the doors’ hinges. In some cases, the hinges failed while on base. In other instances, doors fell off in the field while on patrol in Afghanistan and Crimea, leaving soldiers to figure out how to reattach a 1,200-lb door to get themselves and their vehicle back to safety.
Hinge failure could take the vehicle out of commission for an extended time – as long as two years – while replacement hinges from the original equipment manufacturer (OEM) were procured, delivered and installed through the traditional supply chain. At times, the valuable vehicles would need to be transported back to the U.S. at great expense to complete the repair. That led TARDEC, the U.S. Army’s Tank and Automotive Research, Development and Engineering Center, to seek an alternative supply for replacement hinges. TARDEC brought the challenge to the ADAPTSM Center, and together with its members and partners, ADAPT used data-driven additive manufacturing (AM) to reproduce and ultimately redesign the hinges.
An ADAPT partnership of Colorado School of Mines, Elementum 3D, Citrine Informatics and Ft. Carson worked with TARDEC and the Air Force Research Laboratory to first replicate and characterize the fatigue performances of the direct replacement parts made using AM. The knowledge gained from that initial phase of the program informed a redesign of the hinge using design for additive principles, which reduced the number of parts in the hinge assembly from six to one and reduced the maximum stress in the hinge joints from 900 MPa to below 90 MPa (an order of magnitude increase in the factor of safety). Then, in the final stage of the program, ADAPT partnered with Professor Albert To at the University of Pittsburgh to optimize the geometry of the designed-for-AM hinges, which reduced their weight by 38% relative to the original hinge assemblies.
This collaborative process took a data-driven approach that showcased the strengths of the ADAPT Consortium. Using preexisting data from other ADAPT projects already in the adapt.citrination platform, the team was able to predict the quality of the replacement part, which was built using a completely new material/printer combination. The result was an 84% accurate prediction of build parameters on the first print, which simply replicated the design of the existing OEM hinge assembly. Then, the group was able to focus on how to create a simpler, lighter hinge, not just a direct replacement.
Using a design/build strategy that incorporated new modeling, simulation and experimental test data into the adapt.citrination database, the team was able to quickly produce quality specifications for temporary or permanent replacement parts. This feedback method – build, test, then use machine learning to evaluate and update the build – can significantly reduce development and qualification time. Testing verified that predicted settings like build direction and build speed produced a final product that meets or exceeds the performance required in the field in terms of strength, weight and durability.
The final hinge design, significantly stronger and lighter than the OEM hinges, eliminated the failure problem under the 1200-lb load and is a direct one-piece replacement that uses the same bolt pattern. A set of MRAP hinges built using ADAPT’s Optimize for AdditiveSM strategy are ready for ground vehicle testing by the Army in mid-2019.
Key improvements from the original OEM hinge include:
Through collaboration and the application of data-driven Optimize for Additive methodologies, ADAPT met the challenge of qualifying an AM process for ground vehicle part replacement by producing parts ready for ground testing, all within one year.