The Hole drilling method is a specific test method used to determine residual stresses inside materials. It is applicabile to a wide range of materials and mechanical components: metallic or non metallic materials.

For composite or plastic materialsit can be performed thanks to a modification of the measurement instrument.

There are several techniques to measure residual stresses: the Hole Drilling Method still remains one of the most appreciated; it can be used both on laboratory than on-site.

The Hole drilling method is very versatyle and it concern a semi-destructive tecnique: the generated hole do not impair the structural integrity of the material to analyze.

It is also the most flexible and reliable technique for performing residual stress analysis and it gives an high level of accuracy.

How does it work?

The hole drilling method consists in drilling a small hole (approx. 1.8 mm x 2.0 mm) into the center of a special 3-element strain rosette and using the high-speed drilling technique (introduced and studied by Flaman in 1982.)

The hole changes the initial strain allowing redistribution of the residual stresses originally existing in the material.

The hole drilling procedure allows to keep stresses "uniform" during the test, without involing additional ones. That's why the hole drilling method is also called semi-destructive: the risk of damage the material during the residual stress test is small. 

Semi-destructive methods remove only a small quantity of material very close to the 
strain gage rosette used in the measurement area, leaving its overall
structural integrity for other testing or use.  

Also, the high speed drilling used by MTS3000- Restan, do not change the state of stresses in the material: it allows relief holes to be drilled without inducing new stresses.

The measurement procedure involves these other steps:

  1. Installation of the specific strain gage rosette with three radial grids
  2. The hole is drilled through the geometric center of the rosette
  3. The residual stresses are calculated from the measured strains using special calculation algorithms.

Click here to get more info about the Strain Gage Residual stress measurement 

Moreover the Hole drilling residual stress method is regulated by the ASTM E837-13a standard applicable to uniform or not uniform residual stress field in the depth.

SINT Technology has developed and patented a fully automated system for measuring residual stresses by the hole drilling method: MTS3000 - Restan

Measurement of Residual stresses - Download Brochure