What indentation strength testing tells you
Yield and tensile strength are usually measured on machined tensile coupons. That is slow, needs plenty of material, and cannot test a coating, a weld’s heat-affected zone, a small part or a finished component. Flat-punch indentation measures strength on a small polished area, so it reaches places a tensile test cannot and allows many repeats on a single sample.
How flat-punch indentation works
A cylindrical flat diamond punch is pressed into the surface under controlled load while depth is recorded. Because the punch face has a constant contact area, the load–depth curve is roughly linear while the material deforms elastically. It changes slope distinctly as the material beneath the punch yields. Analysing the curve gives yield strength and, from the subsequent response, ultimate tensile strength.
In NANOVEA’s published study, SS304 and Al6061 were tested in microindentation mode with a 200 µm flat diamond punch on mirror-polished samples, giving yield and tensile strength comparable with conventional tensile test values.
Why it avoids some tensile-test pitfalls
Tensile results depend on coupon preparation and on the alignment and configuration of the tensile machine, and different machines can give noticeably different results. Machining can also introduce defects that dominate the outcome. Indentation sidesteps coupon preparation entirely, and the small indent size allows several tests on one sample, so local variation becomes data rather than noise.
Fatigue by repeated indentation
Loading and unloading the same location repeatedly shows how a material responds to cyclic stress: whether depth keeps increasing, how stiffness evolves and when damage accumulates. Indentation fatigue gives comparative fatigue behaviour on small volumes such as coatings and treated surfaces, complementing conventional fatigue tests.
Related small-scale strength tests
The same platform measures the elastic limit by spherical indentation, and stiffness and fracture load in micro three-point bending. Together these build a picture of mechanical strength from samples far smaller than a tensile bar.
