Using Multi-Dimensional Digital Image Correlation to Measure Mechanical Properties of Additively Manufactured and Anisotropic Materials

Abstract

The additive manufacturing market is continuing to grow as 3D printing gains further attention as a popular manufacturing option. With this, the demand for material property characterization of AM materials has also increased. Qualification of new, or custom, additively manufactured mechanical structural components presents a significant barrier to large-scale industry adoption. One of the challenges of characterizing AM material mechanical properties is the anisotropy of these properties resulting from the manufacturing process. This is particularly true for AM metals and metal alloys. An additional challenge is that 3D printing larger-sized samples is expensive and time consuming. Testing smaller samples in the millimeter size range, is more efficient and, therefore, desirable.

Previous work has been conducted applying 2D and stereo planar digital image correlation (DIC) to measure mechanical properties of AM metallic tensile specimens. Application of multi-dimensional, multi-planar tensile tests of AM metallic specimens has not been employed. In this effort, a multi-dimensional digital image correlation (Multi-DIC) tool was developed using MultiDIC, an open-source library for multi-dimensional DIC analysis, to illustrate that multi-dimensional DIC is a highly practical method for quantification of mechanical properties of 3D printed metals. Tensile tests using this tool were conducted on sub-sized laser powder bed fusion copper-alloy C-18150. For each test, the tool provided an array of mechanical properties in multiple directions on multiple planes as well as engineering and true stress-strain curves from test start to near fracture.

In addition to measurement of AM mechanical properties, the versatility of the DIC tool was illustrated with the measurement of compressive deformations of AM complex cellular structures. Additional potential applications of the DIC tool, such as high-temperature tensile testing or simultaneous use with other instrumentation (i.e. surface roughness) are discussed.