A dual indentation method for evaluating intrinsic material properties of metals under residual stress

초록

A dual flat -spherical indentation (DFSI) method is proposed for evaluating elastic -plastic properties of metallic materials under equi-biaxial residual stress (RS) state. DFSI consists of two indentation steps: (step I) performing flat indentation (FI) on a specimen having significant presence of residual stress, and (step II) performing spherical indentation (SI) at the center of residual imprint generated by the FI (step I). Indentation load -depth curve in conventional single spherical indentation (SSI) generally varies with RS, while the load -depth curves of SI step in DFSI are almost identical even under significant RS; this is attributed to stress redistribution during the preceding FI step. A set of FE analyses are performed for a wide range of properties of general metals. Regressionbased mapping functions are established for evaluating the elastic -plastic properties from the SI data of step II. Finally, the proposed method is validated by performing DFSI experiments on the mechanically stressed SM45C and SS400 specimens.

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