Synopsis

Depth sensing indentations are indentation experiments in which the load and the displace-ment of a hard indenter are measured continuously. The complete deformation history of the material indented is recorded as the load-displacement characteristics. The projected area of the indent is obtained from the depth of penetration, known as the geometry of the indenter. Thus hardness of the material is obtained without imaging the resulting impression. This makes the depth sensing indentation ideal for determining the property of small volumes of material, as in nano-indentation. Apart from the hardness, there is a wide range of other material properties that can be obtained from the load-displacement characteristics. The common thread running through this thesis is depth sensing indentation. Chapter 2 deals with a mechanical model of elasto-plastic indentation. A parameter- strength of the Blister eld, that characterises the stress eld in an elastic-plastic indentation is obtained ab initio. Chapter 3 describes the design of a depth sensing indenter capable of measuring material properties by indenting to a depth of nanometers. Chapters 4, 5 and 6 address the problems encountered in indentation when penetration depth is comparable to the surface roughness. Blister eld model [111] gives the stresses in an elastic-plastic indentation as a sum of tw