Material Characterization for Additive, Part 2

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On October 31, 2017, Posted by , In Uncategorized, With No Comments

In our previous blog, we discussed the importance of material characterization to successfully build metal parts using additive manufacturing. Today’s post will cover some specifics on how Addaero exploits the advantages of additive manufacturing for efficient fabrication and testing of material properties.

Using a Design of Experiment Test Matrix

At Addaero, we explore several variables at once such that each fabrication run is as efficient as possible in providing the most data. For instance, we create builds that allow analysis of microstructures, testing of tensile properties (including yield and ultimate strengths, elongation and Young’s modulus), and testing for the chemistry of the produced material while at the same time testing topological variables that include part location and orientation. The location of fabrication within the envelope is captured for each specimen into a centralized database that allows us to revisit the data should the need arise.

Tensile and Fatigue Testing

For example, we make sure to have round bars that are orientated in a minimum of three orientations (corresponding to the main X, Y, and Z axes) to produce tensile or fatigue specimens in an equal number of orientations. We also fabricate several tiers or layers of these specimens such that we consider the effect of the Z height at which the specimen is produced. Further, we stagger the orientation from tier to tier such that we get the maximum degree of specimen orientation randomization.

Microstructure and Chemical Testing

When it comes to microstructure and chemical testing specimens, we traditionally produce several cubes (about ½” per side for microstructure and about a ¼” for chemical specimens) that are scattered throughout the build envelope to achieve a high degree of specimen randomization. In this fashion, we can probe these properties of the material throughout the fabrication envelope providing customers with the assurance that our team will work to achieve homogeneous properties for any component produced.

Surface roughness

Another example of this multi-variable testing approach was previously described in a later blog post: the effects of roughness on the tensile properties. As we discussed in that article, the design of experiment performed in this case allowed to test the effects of surface roughness on the tensile performance. Specimens were fabricated by EBM and their necks were tested in three conditions; as-fabricated, machined and processed through REM’s isotropic superfinishing (ISF) processing. For this, we also applied the specimen location and orientation design of experiment matrix further expanding the amount of data that was obtained from a single experimental run.

Efficient material use

Our approach to make the most of the material available includes the use of some pre-processing techniques that include:

  • Packing of the build envelop by distancing specimens the minimum allowed clearance that allows detaching them.
  • Using the minimum amount of support required, such as the use of the hanging supports in the EBM process.
  • We work with testing houses to specify the minimum dimensions necessary to create a blank that can be used for testing. The purpose is to lessen the material consumption while still providing the ability to perform the required testing.

There you have it, these are some of the strategies we employ to provide the most value to our customers while meeting testing requirements for a given application. If you are interested in learning more get in touch with us.

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