The life expectancy of a structural part is mainly determined by the interaction between defects in the component and the stresses to which it is subjected. These stresses are the result of stresses applied in service, compounded with those that develop in the object during manufacturing and machining processes, commonly termed residual stresses. These residual stresses can add to operating loads, thus accelerating the growth rate of defects and leading, in some cases, to premature failure of parts, with very serious economic implications.
Although applied stresses are generally taken into account in design engineering, residual stresses are often overlooked, being closely correlated with the material, the manufacturing processes and its heat treatment, and also being able to change during operation.
There is also a limited awareness of the effect of these stresses on the performance of a component and, consequently, of the potential economic benefits that could ensue from their being accurately evaluated.
Hence the reason for organizing theoretical-practical courses on residual stresses with the following objectives:
To present the concept of residual stresses and the effect of residual stresses on the strength of metallic parts from a theoretical viewpoint;
To discuss practical cases where the transformation processes can introduce residual stresses (for example, welding, molding, heat treatment);
To show an overview of the main residual stress measurement methods (mechanical relaxation, diffractive and other minor methods)
To help the participants to choose the most appropriate residual stress technique with knowledge and care, in order to achieve the best overall results for their application
To illustrate the fundamental principles, the strengths and limits of one of the most widely used techniques forÂ measuring residual stressesÂ available today â€“ theÂ hole-drilling strain-gage methodÂ â€“ including also the regulatory issues;
To offer a full rundown of applications of this technique, both where residual stresses are negative for the performance of the part in service and also when they are deliberately introduced into a component to raise its fatigue limit (e.g. by shot peening), and have therefore to be quantified.