Introduction

The invention concerns a method based on the Active Thermography technique in order to locally characterise residual stress fields due to thermal and mechanical treatments in metals and in mechanical components. The developed methodology aims to identify the microstructural modifications in materials by means of the corresponding measurement of physical and thermal properties variation.

Technical features

The patent refers to the identification in materials and mechanical components of residual stress fields due to many factors, as mechanical processing, thermal and mechanical treatments, and so on…. Residual stresses may modify the microstructural state of materials and then they may change the corresponding phisycal and thermal properties. This variation can be locally identify by Active Thermography, well known as a Non Destructive Technique, referring to the heat transmission phenomenon. The method aims to identify a stress distribution relating it to the corresponding thermal diffusion capacity, utilising a thermal source excitation (laser, lamps, inductor, …) and a response sensor (infrared thermocamera). The residual stress field may be characterised in terms of corresponding heat diffusion gradients by processing the measured data (temperature and/or radiance profiles).
TRL: 6

Possible Applications

• Characterization of residual stress from thermal or mechanical treatments;
• Industrial component analysis, e.g. gears, springs, shafts;
• Identification of residual stresses due to production errors or damage.

Advantages

• Non-destructive measurement technique;
• Punctual measurement of residual stresses permitted;
• Use of commercial equipment.