ISSN: 0090-3973
Page Count: 8

Initial Deformation During Small Punch Testing

Cheon, JS
Ph.D. candidate and professor,Korea Advanced Institute of Science and Technology,

Kim, IS
Ph.D. candidate and professor,Korea Advanced Institute of Science and Technology,

(Received 5 July 1995; accepted 12 February 1996)

Abstract

Initial deformation behavior during small punch (SP) testing was investigated in order to estimate yield stress using two sizes of SP specimens, 10 by 10 by 0.5 mm³ and 10 by 10 by 0.25 mm³ by finite element (FE) analysis and by experiments with heattreated SA508 and 12Cr steels. The increase of thickness resulted in a deviation from the initial linearity of the load-displacement curve at higher loads. The deviation was attributed to different causes, namely loss of the constraint by the surrounding material and radial propagation of plastic bending deformation for 0.5 and 0.25-mm specimens, respectively. The causes for the transition of deformation mode were identical irrespective of material strength and work-hardening rate in the range of yield stress about 400 to 900 MPa. Based on the invariance of the deformation mode, a distinct linear relationship between the load at the breakaway from initial linearity and the yield stress was predicted by the FE analysis and compared with the experimental results.

Keywords:
small punch (SP) test, initial deformation, ball indentation, contact stress, specimen thickness, stress and strain contour, yield stress

Paper ID: JTE11449J
DOI: 10.1520/JTE11449J
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