3 research outputs found
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Calibration of the Johnson-Cook Material Model for Additively Manufactured 304L SS Parts: Modeling and Experiments
Selective laser melting (SLM) is a type of additive manufacturing technique which uses a powder
bed to form complex metal parts in a layer-by-layer process. This study aims to understand the
material flow of parts manufactured by SLM process using 304L stainless steel powder, which is
widely used in numerous applications. The tensile specimens were manufactured using 304LSS
powder through SLM process. Low strain-rates, high temperature tensile tests were carried out to
calibrate the parameters of the constitutive Johnson-Cook strength model. To conduct the tensile
tests, different temperatures (25
oC, 150 oC and 250 oC) and strain-rates (0.1 s-1, 0.01 s-1 and 0.001
s-1) were used. The material model developed was used in numerical simulation of the tensile tests
and compared with the experimental results.Mechanical Engineerin
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JOHNSON-COOK FAILURE MODEL FOR ADDITIVELY MANUFACTURED 304L STAINLESS STEEL PARTS
Laser powder bed fusion (LPBF) process is a type of additive manufacturing technique
which uses a powder bed to form complex metal parts in a layer-by-layer process. This study aims
to understand the damage initiation in the parts manufactured by LPBF process using 304L
stainless steel powder, which is widely used in numerous applications. The tensile specimens were
manufactured using 304LSS powder through LPBF. Tensile specimens with varying notches were
tested to calibrate the parameters of the constitutive Johnson-Cook failure model. To obtain the
strength parameters, the tensile tests were performed at different temperatures and strain-rates. The
material model developed was used in numerical simulation of the tensile tests and compared with
the experimental results.Mechanical Engineerin
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INFLUENCE OF STEEL ALLOY COMPOSITION ON THE PROCESS ROBUSTNESS OF AS-BUILT HARDNESS IN LASER-DIRECTED ENERGY DEPOSITION
To ensure consistent quality of additively manufactured parts, it is advantageous to identify
alloys which can meet performance criteria while being robust to process variations. Toward such
an end, this work studied the effect of steel alloy composition on the process robustness of as-built
hardness in laser-directed energy deposition (L-DED). In-situ blending of ultra-high-strength lowalloy steel (UHSLA) and pure iron powders produced 10 alloys containing 10-100% UHSLA by
mass. Thin-wall samples were deposited, and the hardness sensitivity of each alloy was evaluated
with respect to laser power and interlayer delay time. The sensitivity peaked at 40-50% UHSLA,
corresponding to phase fluctuations between lath martensite and upper bainite depending on the
cooling rate. Lower (10-20%) or higher (70-100%) alloy contents transformed primarily to ferrite
or martensite, respectively, with auto-tempering of martensite at lower cooling rates. By avoiding
martensite/bainite fluctuations, the robustness was improved.Mechanical Engineerin