The example in Fig. Proc. , Vol. Each data set corresponds to the average of five sets of measurements. Cracking becomes apparent even at low loads with severe chipping occurring at higher loads. The results presented in Fig.
Harder materials tend to exhibit a more pronounced gradient change as the strain is increased.
Although a spherical indenter theoretically produces a uniform stress field around its circumference, severe cracking is nevertheless observed in materials such as silicon, especially when several load-unload cycles are performed on the same area. The AFM images shown in Fig. 4 represent residual indents in pure copper and the corresponding cross-sectional profiles are plotted together in Fig. Previous measurements have shown that multicycle indentations produce less pile-up in soft metals such as copper than a monocycle indentation to the same maximum load. This phenomenon can be attributed to the effects of gradual work hardening under the indenter as the load is increased on every subsequent cycle. A careful choice of indenter radius, coupled with a suitable load range, allows a very wide range of materials to be investigated with this technique.