Abstract
BackgroundPrior work described an approach for mapping the two-dimensional spatial distribution of biaxial residual stress in plate-like samples, the approach combining multiple slitting measurements with elastic stress analysis. Objective This paper extends the prior work by applying a new variation of the slitting method that uses measurements of cut mouth opening displacement (CMOD) rather than back-face strain (BFS). MethodsFirst, CMOD slitting is validated using an experiment where: BFS and CMOD are measured simultaneously on the same sample during incremental slitting; two residual stress profiles are computed, one from the BFS data and a second from the CMOD data; and the two residual stress profiles are compared. Following validation, multiple adjacent CMOD slitting measurements are used to construct two-dimensional maps of residual stress in plates cut from quenched aluminum. ResultsThe two residual stress versus depth profiles, each computed separately from BFS or CMOD data, are in agreement, with compression near the plate boundaries (-150 MPa) and tension near the plate center (100 MPa); differences between the two stress profiles have a maximum of 25 MPa and a RMS of 7.2 MPa. Repeated biaxial residual stress mapping measurements show the CMOD technique is repeatable, and complementary contour method measurements show the mappings are valid. Aspects of CMOD and BFS deformations during slitting are also described and show they are generally complementary but that CMOD slitting is favorable in narrow samples.
Highlights
Quenching, the rapid cooling of a hot workpiece, is a mainstay of material processing in a variety of metallic alloys [1]
A total of 29 slitting measurements are made on samples D1, F7, F8 and G14 to determine the longitudinal and transverse components of bulk residual stress (BRS)
The differences in stress computed from back-face strain (BFS) or cut mouth opening displacement (CMOD) for y < 15mm may be an effect of the notch used to accommodate the CMOD gage, the relatively low sensitivity of the strain gage at small cut depths, or both
Summary
The rapid cooling of a hot workpiece, is a mainstay of material processing in a variety of metallic alloys [1]. This work describes experimental measurements of two in-plane components of the residual stress tensor field in plate-shaped aluminum parts that had been cut perpendicular to the length of long rectangular quenched bars. Multiple adjacent CMOD slitting measurements are used to construct two-dimensional maps of residual stress in plates cut from quenched aluminum. Results The two residual stress versus depth profiles, each computed separately from BFS or CMOD data, are in agreement, with compression near the plate boundaries (-150 MPa) and tension near the plate center (100 MPa); differences between the two stress profiles have a maximum of 25 MPa and a RMS of 7.2 MPa. Repeated biaxial residual stress mapping measurements show the CMOD technique is repeatable, and complementary contour method measurements show the mappings are valid. Aspects of CMOD and BFS deformations during slitting are described and show they are generally complementary but that CMOD slitting is favorable in narrow samples
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