Fraunhofer Institute for Mechanics of Materials IWM
Fraunhofer Institute for Mechanics of Materials IWM
© S.K.U.B./Fraunhofer IWM

Mechanical properties of materials in the meso- and microregime

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© S.K.U.B./Fraunhofer IWM

Meso- and Micromechanics

Applying self-developed test set-ups and experimental mechanics, we are capable of determining the material properties of samples with at least one dimension in the microscale. The testing of micro-parts is a routine, everyday occurrence for us, and we also carefully prepare small samples from larger components in order to determine the local material characteristics of critical parts. Our aim is to contribute to current material models, the design of metamaterials, the optimization of local materials properties and the understanding of size effects, which frequently appear in micro-regime samples. 

What we offer

 

  • Design and performance of tensile, bending and bending-resonant tests on microscale samples
  • Determination of mechanical material properties on microscale samples
  • Manufacturing of optimized micro-samples (minimized influence of the manufacturing process)
  • Development and optimization of micromechanical test rigs and corresponding software
  • Real-time strain measurement using Digital Image Correlation and Tracking
  • Detection of fatigue damage before crack initiation
  • High-resolution analysis with respect to microstructure and defect distributions
  • Deep learning based semantic segmentation of damage locations
  • Development of mechanical metamaterials

Topics

 

© Fraunhofer IWM

Mechanical testing of micro-samples


Special test set-ups are used in order to determine the properties of very small material samples. For example, the fatigue characteristics of 200 µm cantilevers were tested, the samples coming from electrical steel sheets that typically find application in the automotive sector. From mechanical construction, to the control and DAQ systems, the test set-ups are constantly being further developed. The set-ups are used in order to determine ...

 

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Detection of fatigue damage before crack initiation


With a micro resonance fatigue set-up, we are capable of detecting early-stage fatigue damage in samples with thicknesses of approximately 200 µm. This is accomplished by tracking changes in the sample’s eigenfrequency. Through SEM analysis of fatigued nickel samples, it was possible to correlate measured eigenfrequency changes with the following fatigue stages: extrusion development, crack initiation in single grains, and micro-crack growth. The ...

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Development of nanostructures for the creation of mechanical metamaterials 


In order to design the mechanical properties of metamaterials, we employ three-dimensional nanolithography. In our application, framework structures with a minimal thickness of 100 nm are polymerized out of a photoresist by a femtosecond laser. The unit cells of these structures are constructed so that they show a desired mechanical property when coupled in a large matrix. The structure shown...

 

 

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Process optimization 


The interdisciplinary field of process optimization deals primarily with multi-dimensional optimization tasks from materials science and other relevant engineering sciences. These tasks are solved by applying methods from computer science and mathematics. For example, the optical strain measurement parameters in a scanning electron microscope can be optimally set with only a few tests. Furthermore, complex production processes can be described through approximation...

 

 

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Machine learning in materials engineering
 

Data-driven methods are increasingly finding their way into materials science. Applications range from material design, identification of hidden relations (data mining), and prediction of material’s properties to characterization of microstructures, defects, and damage. By using such methods, predictions can often be greatly improved compared to purely knowledge-based approaches due to their ability to generate highly accurate representations and high fidelity. This is...

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Quantum Sensing for materials characterization
 

Features indicating damage or defects, for example, can be identitfied within the magnetic field of a material. For materials testing, this means that damage, such as in the form of cracks, can be detected at an early stage—before it is visible with other methods. These magnetic signals are very weak, however, and can only be read out and interpreteded with a highly sensitive measurement technique. At Fraunhofer IWM, we research how weak magnetic signals in material samples under stress can be used for the early detection of defects.

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Meso- and Micromechanics publications

 

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Contributions to scientific journals, books and conferences as well as dissertations and project reports...

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