TECHNOLOGY AREA(S): Materials/Processes

ACQUISITION PROGRAM: Enterprise Platform Enabler (EPE)-17-03 Quality Metal Additive Manufacturing (Quality Made).

OBJECTIVE: Develop, optimize, and demonstrate use of high throughput mechanical testing at key length scales to inform computational tools and rapidly determine effects of defects for additive manufacturing (AM).� High throughput testing must focus on static and dynamic material properties equivalent to conventional American Society for Testing Materials (ASTM) tests.

DESCRIPTION: There have been significant advancements in computational modeling tools to correlate and explore the interactions of microstructure and material properties.� In order to validate these computational tools, static and dynamic tests are used to provide statistically relevant mechanical properties across the material composition and processing space.� In AM, this information is necessary to inform computational tools being developed.� Conventional tensile and fatigue tests are time-consuming to fabricate and test for the desired compositional and process windows.� Similarly understanding the effects of defects in AM requires testing at key length scales based on critical geometric features.� New techniques for high throughput testing can inform computational models and key acceptance criteria for non-destructive inspection.

Current testing protocols for qualification and certification are predicated on conventional test specimens and techniques for tensile (ASTM E8) and fatigue testing (ASTM E466).� To fully develop and characterize material properties to determine critical acceptance/rejection criteria, specifications such as Military Standard (MIL-STD)-2035A use historically developed empirical data to identify key indications and critical size/morphology.� AM is a new manufacturing technology that builds material up layer by layer and allows for new designs that could not be previously manufactured.� However, due to the complex geometries and fine resolution features, both inspection and conventional testing of these materials are challenges.� Currently, understanding the effects of defects in a new manufacturing process requires a large number of bulk test specimens to establish non-destructive testing acceptance and rejection criteria and may not be representative of the resolution in AM parts.

High throughput testing has been heavily utilized in the pharmaceutical industry to quickly screen combinations for drug development.� Similarly, there have been efforts within the materials community to use combinatorial analysis to identify promising new material compositions.� However, these tests focused primarily on thin film materials and may not be representative of bulk materials.� Similarly, there have been efforts in examining mesoscale tensile tests and correlation to larger ASTM-based best specimens.� Mesoscale testing is currently limited by throughput due to the necessary care in specimen fabrication and testing.� To realize fully the capabilities of AM, new high throughput test methodologies must be developed to test bulk materials at the critical length scales to enable accurate modeling and quantitative characterization and rapid development of design allowables and determination of effects of defects.

PHASE I: Define and develop a concept/approach for high throughput testing of metal AM to probe micro- and meso-scale features such as voids, porosity, and lack of fusion.� Key features may be on the order of 50-100um and test specimen sizes should be greater than 200um in thickness based on current MIL-STD-2035A criteria.� The concept must provide a 10x throughput improvement over conventional ASTM E8 and ASTM E466 tests.� This may include design or adaptation of existing techniques or equipment to support testing materials directly from a build plate and measurement of key load/displacements.� This topic will also consider methods for preparing (or extracting) test coupons with well characterized isolated defects for multi-length, scale model development.� If awarded the Phase I option, the small business will demonstrate the feasibility of the proposed concept/approach.� Develop a Phase II plan.

PHASE II: Based on Phase I results, develop, demonstrate, and validate the proposed high throughput test apparatus for tensile testing.� Rapid defect characterization methods, before and after destructive mechanical testing, should also be considered in specimen preparation and testing for testing validation.� The apparatus will be investigated for use in fatigue testing.� It is recommended that the performer work with bulk material vendors/Original Equipment Manufacturers (OEMs) to facilitate transition for Phase III.

PHASE III DUAL USE APPLICATIONS: Phase III will transition optimized high throughput testing techniques to commercial suppliers through bulk material vendors, OEMs, or other partnering agreement(s).� Commercialization of this technology may be through new material discovery or rapid process development.� Phase III will demonstrate the technology to Warfare Centers and other DoD production/maintenance facilities.

REFERENCES:

1. ASTM E8, Standard Test Methods for Tension Testing of Metallic Materials, https://www.astm.org/Standards/E8.htm

2. ASTM E466, Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials, https://www.bsbedge.com/astm/astme466-standard

3. MIL-STD-2035A, Department of Defense Test Method: Nondestructive Testing Acceptance Criteria (15 May 1995), http://everyspec.com/MIL-STD/MIL-STD-2000-2999/MIL-STD-2035A_6636/

4. Slotwinski, John A., Garboczi, Edward J. and Hebenstreit, Keith M. �Porosity Measurements and Analysis for Metal Additive Manufacturing Process Control.� Journal of Research of the National Institute of Standards and Technology, Vol. 119 (2014), http://nvlpubs.nist.gov/nistpubs/jres/119/jres.119.019.pdf

5. Lee, Jaewon.� �Failure Mechanism of Laser Welds in Lap-Shear Specimens of a High Strength Low Alloy Steel.�� J. Pressure Vessel Technology 134(6), 061402 (Oct 18, 2012), http://pressurevesseltech.asmedigitalcollection.asme.org/article.aspx?articleid=1661606

KEYWORDS: Additive Manufacturing; High Throughput Testing; Tensile; Fatigue; Effects of Defects; Non-destructive Inspection