|
|||||||
|
|
|
Mechanical Property Testingby Continuous Depth Recording |
|
 |
|
|
The NanoTest employs continuous depth recording (CDR) to automatically monitor the penetration of a diamond indenter into a surface. Since the depth resolution is better than 1 nm, extremely shallow indentations can be quantified. This is particularly valuable for testing thin solid films and small particles. In the case of thin hard films on soft substrates, for instance, the indentation depth should generally not exceed 10% of the film thickness in order to preclude any influence of the substrate.
Typical NanoTest indentations involve increasing the load on the indenter until a particular load or depth occurs, then holding the load constant for a pre-defined period, and finally decreasing the load on the indenter back to zero. The diamond displacement relative to the initial surface position is monitored continuously. The hardness and elastic modulus of the material are derived from the resultant Depth vs. Load curve.
The results shown illustrate the indentation behaviour of aluminium, tungsten and fused silica. As one would expect, for a given load the indentation depth is highest for aluminium, which is the softest material. The elastic modulus is derived from the slope of the unloading curve and the contact area between the indenter and plastically deformed material at maximum load. Contact areas are determined automatically from the Depth vs. Load data. From the figure, it can also be seen that for fused quartz, much of the on-load depth is recovered elastically as the load on the indenter is reduced.
A 3-faceted Berkovich diamond indenter was used. The maximum load in each case was 60 mN, the dwell period at this load was 60 s, and the time to achieve maximum load was approximately 30 s. For averaging, 10 indentations were produced for SiO2 and W, and 5 were produced for Al.
|
|