A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 2 2 2 strength-to-ultimate tensile strain ratios for a given application. The arc melted material was found to have the lowest yield strength (113MPa) and lowest ultimate tensile strength (217 MPa). Regarding yield strengths (excluding the arc melted specimen discussed above), the hybrid CSAM and shot-peened, extruded, and CSAM processed Al 6xxx specimens were found to be 238, 300, and 338 MPa, respectively. At the same time, the ultimate tensile strengths (excluding the arc melted specimen) for the hybrid CSAM and shot-peened, extruded, and CSAM processed Al 6xxx specimens were found to be 381, 356, and 339 MPa, respectively. By coupling these insights regarding strength with implications for ductility from the nominal stress-strain curves obtained via PIP testing and analysis, hybrid CSAM and shot-peened processed Al 6061 resulted in the most pronounced balance between strength and ultimate tensile strain, i.e., the strain at which the onset of plastic instability initializes, followed by necking until critical failure occurs. Interestingly, one can demonstrate the value of using the Voce plasticity constitutive law parameters obtained from PIP testing to define the mechanical characteristics within FEA and affiliated models to obtain insights surrounding specimen-specific deformation behaviors. For example, SEMPID contains a tool for PIP users that provides operators with the ability to model Brinell indentation as a function of the Voce plasticity parameters garnered from PIP analysis (Fig. 3). Specifically, this built-in feature within SEMPID models a Brinell indentation test wherein the simulated Brinell indenter tip radius is 5 mm and the max indentation load applied is 3000 kg. Thus, Fig. 3 captures the final effective plastic strain fields and von Mises stress fields for the hybrid CSAM and shot-peened, extruded, and CSAM processed Al 6xxx specimens at the maximal external load applied. Concurrently, those interested can also obtain similar plots at various stages of external loading and plot displacement fields and Brinell residual indent profiles. In any case, for the extruded Al 6xxx, CSAM processed, and hybridized CSAM and intermittently shot-peened specimens, Brinell test simulations recorded Brinell hardness values and indent diameters of 123.9 kg/mm2 and 5.333mm, 121.1 kg/mm2 and 5.389mm, and 113.3 kg/mm2 and 5.556 mm, respectively. SEMPID software also en- ables users to model spherical inden- tation and uniaxial tensile tests using the plasticity parameters measured and the axisymmetric tensile coupon geometries and measured ductility. Note that the user must define both of these latter variables prior to performing computational analysis. CASE STUDY 2: WAAM APPLICATIONS This case study focuses on wire arc additive manufacturing (WAAM) and highlights PIP within the context of post-processing influence on strength. The research involved applying PIP testing to a WAAM-processed maraging 250 steel material system. More specifically, the as-printed and stress relieved WAAM-processed maraging 250 steel systems were produced using constant processing parameters and build plate compositions. Stress relief thermal post-processing was first performed on the WAAM-processed consolidations attached to the build plate. Accordingly, PIP testing enabled insights into the stress-strain behavioral evolution induced by thermal post-processing compared to the as-processed counterpart. The two WAAM-processed specimens are shown in Fig. 4 before metallogra- phic preparation and PIP testing. Nominal and true stress-strain data for both Fig. 3 — PIP and SEMPID-enabled FEA of simulated Brinell indentation testing of three uniquely processed Al 6xxx materials. (a) (c) (e) (b) (d) (f)
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