Automated and precise residual stress measurements via the cos alpha method at the Fraunhofer IWM
Automated and precise residual stress measurements via the cos alpha method at the Fraunhofer IWM, Dr. Eva-Regine Carl
Residual stress analyses at the Fraunhofer IWM:
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With innovative measurement and evaluation methods, we help to ensure that highly stressed components can be used safely. In addition, targeted surface modification can extend service life, allowing products to be operated more sustainably.
Internal, mechanical stresses within a component are referred to as residual stresses. These are not caused by external loads, but by plastic deformation during manufacturing and machining processes. They are caused by cold deformation, inhomogeneous microstructural transformations and thermal influences.
Casting, welding and heat treatment can cause components to warp during rapid cooling, which means that dimensional tolerances can sometimes no longer be maintained. The culprit is the formation of local residual stresses in the microstructure.
By knowing local residual stress distributions and adjusting the temperature control in the processes, distortions can be minimized or even avoided. Spatially resolved measurement results also play an important role here in the verification of component simulations.
The analysis of the influence of shot peening treatments on the stress state as well as the distribution of local residual stresses in welded joints and built-up welded components is also of great interest:
Shot peening, for example, specifically introduces residual stresses into components, which can be determined using our methods. Subsequently, the effects of these residual stresses on component lifetime can be calculated.
For the first time, this handy diffractometer enables a measurement time of one minute for the punctual determination of residual stress. This is significantly faster compared to one hour with conventional methods and now enables close-meshed and large-area mappings in conjunction with a robotic arm. These large-area mappings can have a side length of up to half a meter and can be carried out in any orientation in space.
This opens up completely new possibilities for automated determination of residual stress fields over large areas. For example, residual stress gradients in welded joints can be investigated in detail, and surfaces of additively manufactured components can be measured and evaluated. These measurements can be performed on a wide variety of materials such as metals, for instance steel and aluminum as well as ceramics.
Due to the small size of the device, residual stresses can now be determined in places that are difficult to reach for conventional devices.
With the smallest possible beam diameter of 0.2 mm, detailed analyses can also be performed. Residual stresses can be measured in notches or on complex geometries. We can thus investigate cases of damage caused by cracks in complexly built components.
We then interpret these results together with our customers and advise on further improvements to the manufacturing processes. Taking the residual stress state into account, service life evaluations can be carried out to calculate the specific service life for a component under defined operating conditions.
After a feasibility check, we will be happy to provide you with a quotation. Please do not hesitate to contact us.