Nanoindentation

  • Spherical Nanoindentation Stress-Strain analysis

    We have pioneered the development of novel data-analysis protocols for spherical nanoindentation which allow meaningful indentation stress-strain curves to be extracted from the raw datasets. Read more about the analysis

    Hertz Principle

    Assumptions: Linear elastic, isotropic material response, frictionless contact

     

     

     

     

    where a is the radius of the contact boundary at the indentation load P, and he is the elastic indentation depth. Reff and Eeff are the effective radii and effective modulus of the indenter and the specimen system respectively.

     

     

     

     

    where γ and E are the Poisson’s ratio and Young’s modulus and subscript s and i refer to the specimen and the indenter, respectively.

     

     

     

    where P ̃, h ̃e, and S are the measured load signal, the measured displacement signal, and the continuous stiffness measurement signal in the initial loading segment from the machine, respectively. P* and h* are the values of load and displacement signals at the point of effective contact.

     

     

     

     

    Indentation stress

     

     

     

    indentation strain

     

    		  

    Fig. (a) Schematic of the indentation zone in the spherical indentation. (b) Schematic of a typical measured spherical indentation load-displacement curve with the initial and final contact geometries.

    ref. Pathak, S., & Kalidindi, S. R. (2015). Spherical nanoindentation stress-strain curves. Materials science and engineering: R: Reports, 91, 1-36.