Hole drilling method

The hole drilling method is popular for its simplicity and it is suitable for a wide range of applications and materials.

Key advantages of the hole drilling method include rapid preparation, versatility of the technique for different materials, and reliability.

Conversely, the hole drilling method is limited in depth of analysis and specimen geometry, and is at least semi-destructive.

In 1966 Rendler and Vignis introduced a systematic and repeatable procedure of hole drilling to measure the residual stress.

In the following period the method was further developed in terms of drilling techniques, measuring the relieved deformations, and the residual stress evaluation itself.

A very important milestone is the use of finite element method to compute the calibration coefficients and to evaluate the residual stresses from the measured relieved deformations (Schajer, 1981).

The measurement and evaluation procedure is standardised by the norm ASTM E837[4] of the American Society for Testing and Materials which also contributed to the popularity of the method.

The original residual stress in the material is then evaluated based on the measured deformations and using the so-called calibration coefficients.

Disadvantages include the destructive character of the technique, limited resolution, and a lower accuracy of the evaluation in the case of nonuniform stresses or inhomogeneous material properties.

In the vast majority of practical applications, however, the preconditions for using the theoretically derived coefficients are not met, e.g., the integral deformation over the tensometer area is not included, the hole is blind instead of through, etc.

They differ in the preconditions for use, the accuracy requirements on the calibration coefficients, or the possibility to take additional influences into account.

Both the methods are based on the assumption that the change in deformation is caused solely by the relieved stress on the drilled increment.

The hole drilling method Archived 2018-02-22 at the Wayback Machine finds its use in many industrial areas dealing with material production and processing.

The most important technologies include heat treatment, mechanical and thermal surface finishing, machining, welding, coating, or manufacturing composites.

These include especially the size and shape of the sample, distance of the measured area from the edges, homogeneity of the material, presence of residual stress gradients, etc.

Hole drilling method for measuring residual stresses – detail of the end mill in the measuring device.
Principle of the hole drilling method for residual stress measurement.
FEM mesh for computation of the calibration coefficients for the hole drilling residual stress measurement method.
Residual stress evaluation scheme by the Integral method. Shape of the calibration coefficients depending on the hole depth and the position in the hole.