Description
Nanoindentation is a technique developed over the last two decades for studying the mechanical properties of materials at micro or nano scales. The availability of depth-sensing indentation instruments with capabilities for measuring displacements on the order of nanometers now makes it possible to study mechanical properties of finely structured materials where small volumes need to be probed. Flexure-based compliant mechanisms have been used in an ultra-precision stage, stage for nano imprint machines, AFM scanner, and MEMS structures, etc. Flexure stages employ a non-conventional flexure bearing' mechanism in the system, in which the moving platform is linked to a static base by flexure hinges. The platform's movement, driven by piezo actuators, is guided by the flexure mechanism. The guiding motion is generated by elastic deformation of the flexure material. Therefore, the linkage is friction and stiction free, resulting in smooth motion. This thesis discusses the development of Nanoindentation system with a flexure-hinged mechanism. The key components which the system consists are: Flexure based linear motion stage (the Z-axis stage) that provides vertical positioning of the tool tip in addition to measuring the contact load of the tool upon the sample, Berkovich indenter is used as a tool tip and flexure based stage (the XY-stage) for positioning the sample horizontally below the tool. As load is applied to the indenter and sample, reaction forces cause the load frame to be elastically deflected. This can lead to an overestimate of penetration depth into the sample. Thus actual penetration depth is found by subtracting the load frame deflection out of the load-depth curve. To verify the system performance, we conducted standard indentation tests on a fused silica sample and a nickel specimen prepared by Current Activated Tip-based Sintering (CATS). For fused silica, hardness and elastic modulus determined through testing were shown to be close to literature values and for nickel sintered specimen the hardness determined through testing were shown to be close to the results determined from the Vickers test.
