Scientists investigating how metals fail under shear stress have uncovered an unexpected accelerator of damage: stiff particles inside the material can trigger rapid void growth even when shear loading alone was long assumed to be less damaging. The finding, led by researchers at KIT’s Institute for Photon Science and Synchrotron Radiation (IPS) and the Laboratory for Applications of Synchrotron radiation (LAS), together with colleagues at Mines Paris PSL University, challenges simplified views of mechanical failure and carries implications for lightweight engineering and recycled metals.
Shear stress occurs when neighboring parts of a material are displaced relative to one another, generating internal stress. Until now, much research treated shear-driven damage as limited, which made it difficult to fully explain why components sometimes deteriorate faster than expected when subjected to shear-dominated conditions.
To reveal the mechanism, the team focused on aluminum alloy AA2198-T851, a material valued for transportation applications, especially in aviation. They first applied tensile loading to initiate microstructural voids, then switched to shear loading to observe how those pre-formed damage features evolved over time.
The experiments demonstrated a dramatic effect: voids at intermetallic particles continued to enlarge during shear, with the total void volume increasing up to sixfold. Rather than allowing the metal’s internal structure to reorganize and reduce stress concentrations, the stiff intermetallic particles restrained material movement and effectively boosted the rate and extent of void expansion.
The researchers did not rely on indirect measurements. Instead, they combined synchrotron computed laminography (SR-CL)—a technique akin to high-resolution 3D X-ray imaging—with advanced three-dimensional simulation. SR-CL enables visualization inside centimeter-scale, flat samples with micrometer-range detail, making it possible to track voids and their spatial relationship to particle networks.
In parallel, finite element modeling supported interpretation of the evolving microstructure, connecting observed damage patterns to mechanics under shear. Together, imaging and simulation offered a coherent picture of how particles promote void growth rather than merely serving as passive inclusions.
“Our results show a previously unknown damage route in metals under shear,” said Dr. Mathias Hurst from IPS. “Contamination in the form of stiff particles can induce significant damage growth under shear loading.”
By clarifying this particle-induced pathway, the study provides guidance for designing components that better resist failure in real-world loading scenarios. It also highlights a practical challenge for sustainability: recycled metals may contain abundant intermetallic particles, potentially increasing vulnerability to shear-driven degradation.
Original publication: 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.
Subject of Research: Damage mechanisms in metals under shear loading; particle-induced void growth
Article Title: Particle-induced void growth under shear loading revealed by 3D X-ray laminography and finite element modeling
News Publication Date: 15-Jun-2026
Web References: https://doi.org/10.1016/j.ijplas.2026.104724
References: International Journal of Plasticity (2026), DOI: 10.1016/j.ijplas.2026.104724
Image Credits: Simon Bode, KIT
Keywords: shear stress, void growth, intermetallic particles, aluminum alloy, synchrotron computed laminography, 3D imaging, finite element modeling, material damage, metal recycling, ductility
