Reduced elastic modulus represents the elastic deformation that occurs in both sample and indenter tip.Reduced modulus can be calculated by:
E* = Reduced Modulus
E= Modulus of the specimen
E'=Modulus of the indenter
V= Poisson's ratio of the specimen
V'= Poisson's ratio of the indenter
For each loading and partial unloading cycle, the curve is plotted between load with depth which provides information about hardness, elastic modulus and plasticity of the material under examination.
In this experiment a nanoindenter tip of known geometry is projected into the selected location on the material surface of the material to be tested. The load is continuously increased till a designated maximum value, after which we partially unload the material until desired depth is attained. Next holding segment is introduced to allow the material to relax before unloading. The process is repeated many times and position of the indenter tip and the surface is monitored with a differential transformer. The modulii values are calculated using the img/formulae given above.