nanoindentation
TRANSCRIPT
Nanoindentation
Introduction to nanoindentation
It is an indentation hardness test applied to small volumes.Nanoindentation refers to depth-sensing indentation testing in the submicrometer range. • Force >N• Displacement nm• It is used to obtain:I. HardnessII. Elastic ModulusIII. Strain rate sensitivity IV. Other mechanical properties.Procedure of operation is similar to other indentation tests.
HYSITRON NANOINDENTER
Capacitive transducer , probe and high resolution camera
Nanoindenter Tip
Testing probes typically fit into one of the following three categories:
• Three-sided pyramidal probes
• Cono-spherical probes
• 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.
nanoindent
Motion of Indenter
• Force is applied and displacement is measured.
• Force is applied by 1. piezoelectric
actuation 2. electromagnetic
actuation.3. Other methods
Displacement measurement
Capacitive displacement gage
Differential capacitor
In this case, the capacitance measuring circuit is set up to measure the difference between the two capacitances C1 and C2 due to the displacement ∆.
3 PLATE CAPACITIVE TRANSDUCER
Nanoindentation data analysis methods
Hardness:
The hardness is given by the equation below, relating the maximum load to the indentation area.
H=Pmax/Ap
Where
Pmax = maximum loadAp = projected indentation areaArea of indentation can be calculated from displacement.
Nanoindentation data analysis methods
• 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 Young's 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
Young's modulus
ApplicationsTo measure hardness• 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.