EFFECT OF INDENTER TIP RADIUS ON THE LOAD DEFLECTION BEHAVIOR OF THINPLATES

The effect of indenter radius on the load-deflection behavior of a cla mped, thin isotropic and homogeneous plate is discussed. A depth-sensi ng nanoindenter was used to apply a transverse load to the plate cente r and measure the corresponding plate center deflections. The applied stress is assumed to be uniformly distributed over the contact area. T his study shows that the central deflection of the plate is insensitiv e to small changes of indenter tip radius when the normalized indenter tip radius is smaller than about 0.10 (here, normalized indenter tip radius is defined as the ratio of the indenter tip radius to the plate radius). For these small normalized indenter tip radii, the indenter radius effect is the same in both the small (linear) deflection range and in the large (nonlinear) deflection range. Blunt indenter tips hel p to minimize material nonlinearity in the region of contact due to lo calized plastic deformation and/or microcracks, allowing geometrically nonlinear deflection;data to be obtained in a less ambiguous manner.