The resistance of material against mechanical loads is a decisive factor for component safety - such as in aircraft. Working in an international team, researchers from the Karlsruhe Institute of Technology (KIT) have found a previously unknown damage mechanism in metals: Contamination in the form of stiff particles can make the volume of voids grow up to sixfold when exposed to deformation by shear loading. The results of the study are particularly relevant to the ductility and safety of materials in recycling processes. Publication in the International Journal of Plasticity. (DOI: 10.1016/j.ijplas.2026.104724 )
The manufacturers of component parts should be aware of the loads the materials will be exposed to. Mechanical loads such as tension, pressure, bending, or shear affect the material behavior. In the case of shear loading, individual areas of the material are displaced relative to each other, inducing internal stress, which is called shear stress. So far, research relied on the assumption that damage in materials would not increase significantly under shear loading so that material failure under such loads could not be elucidated. Now, scientists from the Institute for Photon Science and Synchrotron Radiation (IPS) and from the Laboratory for Applications of Synchrotron radiation (LAS) of KIT, jointly with colleagues from the Mines Paris PSL University in France, discovered a previously unknown damage mechanism in metals that are exposed to shear loading.
"Contamination in the form of stiff particles can induce significant damage growth under shear loading", said Dr. Mathias Hurst from the IPS. As an example, the researchers demonstrated this damage mechanism in an aluminum alloy, which is especially well suited for the lightweight construction of means of transportation - particularly in the aircraft sector. The study is therefore highly relevant to the ductility of materials, especially in the mobility and transportation industries. On the other hand, it is also of great importance to recycling processes, as recycled metals often contain large numbers of intermetallic particles.
Study Uses Synchrotron Computed Laminography and 3D Simulation
To demonstrate damage growth under shear loading, the researchers combined imaging and simulation methods: They used synchrotron computed laminography (SR-CL), a method similar to computer tomography, which was developed at KIT. It creates a high-resolution 3D representation of the inside of flat, wide objects. The SR-CL method allows to examine individual areas of centimeter-scale samples with a resolution in the micrometer range. The team additionally used advanced 3D simulation methods they developed in collaboration with French scientists to study the identified damages in a model.
test sample after a component part failed under
shear loading. (Photo: Mathias Hurst, KIT)
Stiff Particles Inhibit Material Movement and Boost Void Growth
The researchers investigated an aluminum alloy (AA2198-T851) by exposing the material first to tensile loading and then to shear loading. The tensile stress induced voids in the material, and the team observed their continued growth under shear. This showed that the volume of the voids that had developed at the intermetallic particles increased up to sixfold. "Intermetallic particles are therefore a significant driver of damage growth under shear loading in metals," said Hurst. "The stiff particles inhibit material movement and boost void growth."
The findings of the study provide new insights into damage mechanisms under shear loading and thus contribute to a better understanding of failures of component parts when exposed to loads that are relevant to their application. This means that future component parts can be designed such that they are more long-lived and at the same time more lightweight - an important contribution to safety and sustainability, particularly in the transportation sector.
Original publication
Mathias Hurst, Jean-Michel Scherer, Xiang Kong, Maryse Gille, Simon Bode, Djamel Missoum-Benziane, Tilo Baumbach, Lukas Helfen, Thilo F. Morgeneyer: Particle-induced void growth under shear loading revealed by 3D X-ray laminography and finite element modeling. International Journal of Plasticity, 2026. (DOI: 10.1016/j.ijplas.2026.104724 )
