INTRODUCTION
The industrial products in operation, such as for example a rotor, a pressure vessel and so on, are subjected to continuous mechanical and thermal stresses.
After a certain period, it becomes useful to estimate the residual life, evaluate the conditions of safety and reliability of the structural metal component in operation. This is even more necessary when the component itself has been subjected to severe operating conditions. Anomalous thermal cycles, too high temperatures, too intense mechanical stresses and vibrations, act on the material degrading the component in an anomalous manner.
The risks for safety and the economic repercussions associated with a possible failure of the operation would certainly have a high impact.
To evaluate the state of health of the material in use, laboratory tests must be carried out to analyze the mechanical and metallurgical characteristics. One of the most used tests to evaluate and calculate the mechanical properties is the Small Punch method (SPM).
These tests must obviously be carried out on a sample of material taken from the component in operation.
The main problem lies in the methods of taking samples from the component to be analysed. With the current machinery, the quantity of material to be taken from the component is generally not negligible. This brings to a reduction of the structural performance of the component itself having the sampling damage. Furthermore, the mechanical removal of the sample could affect the mechanical properties of the material, thus distorting the subsequent mechanical tests.
OUR PROPOSAL
Our instrument uses a sampling method that allows you to obtain minimal quantities of material, even in particularly narrow and difficult to reach areas.
Based on the EDM technique, the removal takes place thanks to continuous electric discharges generated between two electrodes, one is the tool, the other is the component from which we want to take the sample. A dielectric liquid is interposed between the two electrodes which has the dual function of removing the resulting material from the working front and cooling it. The maximum temperature reached by the sample during the extraction process is 35°C.
In the images below an example of an extracted sample (first two images on the left) and an example of a groove left on the component following extraction (last image on the right).
CONCLUSIONS
It is important to monitor the reliability and safety conditions of the components in operation. The possible structural failure would in fact cause safety risks and heavy economic repercussions.
Taking a sample of material and subjecting it to appropriate tests is the only way to evaluate the mechanical and metallurgical conditions of the component in its current state.
Thanks to electro-erosion, the tool we use allows you to take very minimal quantities of material, so as not to damage the component in operation. The lack of mechanical and thermal stresses during extraction leads to a sample with completely unaltered mechanical and metallurgical properties.