Introduction to nanoindentationIt is an indentation hardness test applied to small volumes.Nanoindentation refers to depth-sensing indentation testingin the submicrometer range.• Force > N• Displacement nm• It is used to obtain:I. HardnessII. Elastic ModulusIII. Strain rate sensitivityIV. Other mechanical properties.Procedure of operation is similar to other indentation tests.
Capacitive transducer , probe and highresolution camera
Nanoindenter Tip Testing probes typicallyfit into one of thefollowing threecategories: • Three-sidedpyramidal probes • Cono-sphericalprobes • Specialty probes Cono- spherical probe
Diamond Berkovich tip• It is a three sided pyramid• It has a very flat profile, with a total included angle of 142.3 degrees and a half angle of 65.35 degrees.• The Berkovich tip has the same projected area to depth ratio as a Vickers indenter.
Motion of Indenter• Force is applied and displacement is measured.• Force is applied by1. piezoelectric actuation2. electromagnetic actuation.3. Other methods
Displacement measurementCapacitive displacementgage In this case, the capacitancemeasuring circuit is set up tomeasure the difference betweenthe two capacitances C1 andC2 due to the displacement ∆. Differential capacitor
Nanoindentation data analysis methodsHardness:The hardness is given by theequation below, relating themaximum load to theindentation area.H=Pmax/ApWherePmax = maximum loadAp = projectedindentation areaArea of indentation can becalculated from displacement.
Nanoindentation data analysis methods Youngs modulus• When the indenter is unloaded, the material recovers by a process that is primarily elastic.• The slope of the curve, dP/dh, upon unloading is indicative of the stiffness S of the contact. This value generally includes a contribution from both the material being tested and the response of the test device itself. The stiffness of the contact can be used to calculate the reduced Youngs modulus Er:where A = F(hc) is the area of contact of the indentation at the contact depth hc.For a perfect Berkovich indenter,A(hc) = 24.5hc2
ApplicationsTo measurehardness• of thin films• Composite materials• Grain boundaries• Phases Image showing a residual high-load indent impression with low-load indentation tests placed along the pile-up.