Residual stress laboratory and stress analysis center
The hole-drilling method allows to perform experimental stress analysis in several kinds of materials of engineering interest (metals, polymers and composites) without using too expensive devices.
The hole-drilling method consists in drilling a hole in the centre of a special three-grid strain gage rosette installed on the specimens under test: the machining of the hole modifies the mechanical equilibrium of the workpiece allowing a redistribution of the strains (measured by the strain gage).
The hole-drilling strain-gage method has been standardized by the ASTM E837-20 “Standard Test Method for Determining Residual Stresses by the Hole-Drilling Strain-Gage Method”
The hole-drilling method works with a high-speed drilling technology that allows to perform the hole without changing the state of stresses in the material. Moreover, it also consents to drill holes without inducing new stresses, and this is a very important point during a test.
In detail, the high-speed drilling system comprises:
An high speed drilling device (high speed air turbine, 400000 RPM or electric motor, 50,000 RPM);
A tungsten carbide inverted cone endmill (with or without a special coating).