General FAQs About Nanomechanical Testing

There are many reasons why a having a maximum load of 500 mN (low load head) and 30 N (high load head) can be very useful

For example:

• To improve data reliability on rough surfaces
• To observe pop-ins with larger radius probes and study size effects in plasticity
• To produce well-defined crack patterns and measure fracture toughness
• To avoid tip-wear in nano-scratch testing
• To enable more reliable calibration of frame compliance
• To be able to measure more of the whole system response in a multi-layer coating
• To be able to test adhesion in thicker coatings
  
  
  

Constant frame stiffness is critical for ensuring accurate elastic modulus measurements across the entire load range. A simple direct frame stiffness calibration method developed by MML has been used to prove that the frame stiffness of the NanoTest does not vary across the entire load range of each loading head.  The correlation coefficient is 0.9999 over the full load range.

However, researchers  (1, 2) have reported that the stiffness of other nanoindenter instruments is not constant, especially at lower forces which results in questionable data. The superiority of the NanoTest is shown (comparison with data from ref 1) below. The stiffness of the competitor instrument is not constant, especially below 60 mN.

1. p233 in T. Chudoba, (2006) Nanostructured coatings, A. Cavaleiro and J.Th.M. De Hosson, eds. Chapter 6, “Measurement of hardness and Young’s modulus of coatings by nanoindentation” (Springer) pp216-260.
2. Effects of machine stiffness on the loading–displacement curve during spherical nano-indentation, W. Li et al, J. Mater. Res., 1903-1911, 28, 2013
   

There are a number of factors which make the NanoTest particularly well suited for nano and micro scratch and wear testing:

• Load range – up to 500 mN with the low load head, and 30 N with the high load. Using higher loads allows for the use of  larger radius indenters for the investigation of thicker, harder coatings whilst minimising the risk of damaging the indenter.
• The high lateral stiffness of the NanoTest means that the probe does not get twisted. The scratch tracks remain straight and the friction measurements are much more reliable.
• Highly sensitive friction transducer to be used to (1) measure lateral forces with greater precision (2) perform measurements across the entire 500 mN load range.

Yes, Micro Materials have partnered with the Saxonian Institute of Surface Mechanics to provide advanced analysis software for indentation and scratch experiments.

The Indentation and Scratch Analyzer (ISA) includes the ‘Oliver & Pharr for Coatings’ program which enables the user to mechanically characterise complex surfaces by fully automatic analysis of indentation measurements. This program enables the user to calculate Young’s modulus, yield strength, Poisson’s ratio, intrinsic, thermal, or residual stresses (and many more materials properties) of up to 100 layers (including the substrate).

The ISA also includes the ‘Scratch-Stress Analyzer’. This easy-to-use software enables the user to conduct a physical analysis of scratch tests as it evaluates the distribution of 28 field components (e.g. von Mises stress, normal stresses, shear stresses, etc.) of bulk materials and coated systems (up to 100 layers).

Micro Materials have been at the forefront of nanomechanics innovation since 1988 – our pioneering approach as led to many world firsts, including the first commercial nano-impact tester and the first commercial high temperature nanoindentation stage.

We are now the only independent manufacturer of nanomechanical test instrumentation. This provides us with the flexibility to develop new capabilities in response to customer and market requirements. We focus on listening to their customers and helping them develop solutions that they require in order to push the boundaries of nanomechanical testing.

The integrity, reliability and accuracy of our equipment is paramount, as is our relationship with our customers.