Uniaxial tension is a universal material characterization experiment. However, studies have shown that increased formability can be achieved with simultaneous bending and unbending of the material. This so-called continuous bending under tension process is an example of bending stress superposition to a uniaxial tension process. In this research, experiments are conducted on stainless steel 304 to investigate the effects of bending stress superposition on the austenite to martensite phase transformation. Two vortex tubes are mounted to the carriage of the machine and used to decrease the temperature in a localized region of the specimen to evaluate two temperature conditions. The in-situ strain and temperature fields are captured using 3D digital image correlation and infrared cameras. The deformation induced α′
-martensite volume fraction is measured at regular intervals along the deformed gauge length using a Feritscope. The number of cycles that the rollers traverse the gauge length, corresponding to the strain level, is also varied to create five conditions. The deformed specimens revealed heterogeneous martensite transformation along the gauge length due to the non-uniform temperature fields observed for each test condition. Decreasing the temperature and increasing the number of cycles led to the highest amount of phase transformation for this bending-tension superposed process. These results provide insight on how stress superposition can be applied to vary the phase transformation in more complex manufacturing processes, such as incremental forming, which combines bending, tension, and shear deformation.
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Manipulating martensite transformation of SS304L during double-sided incremental forming by varying temperature and deformation path
Double-sided incremental forming (DSIF) is a die-less sheet metal forming process capable of fabricating complex parts. The flexibility of DSIF can be used for in-situ mechanical properties alteration, e.g., by controlling deformation-induced martensite transformation of austenitic stainless steels. In this paper, SS304L is deformed using DSIF at three different cooling conditions and two different tool paths to affect the martensite transformation. Additionally, finite element analyses were used to understandthe effect of tool paths on springback and plastic strain. Implementing a reforming tool path at the lowest achievable temperature resulted in a martensite volume fraction as high as 95%.
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- Award ID(s):
- 1757371
- NSF-PAR ID:
- 10470484
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- CIRP Annals
- Volume:
- 72
- Issue:
- 1
- ISSN:
- 0007-8506
- Page Range / eLocation ID:
- 221 to 224
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.cirp.2023.04.015
