Paul Hans Kamm

We investigate the relationship between cellular topology and macroscopic mechanical behavior of metallic foams by analyzing eight tomographic datasets of aluminum-based foams produced via different manufacturing routes. Using a reconstruction method based on spatial adjacencies, we extract the combinatorial structure of the cellular networks and characterize each foam by the distribution of n-sided interior cells. These distributions serve as robust topological fingerprints that distinguish between different types of metal foams. Uniaxial compression tests reveal systematic differences in plateau stress and densification behavior that correlate with these combinatorial descriptors. Foams with highly connected and topologically constrained networks exhibit higher and more stable plateau stresses and reduced deformation localization. Relative density alone shows no significant correlation with plateau stress across the eight samples studied (r = -0.104), while the fraction of low-sided interior cells yields a substantially stronger relationship (r = -0.67), demonstrating that combinatorial topology is the more informative structural descriptor for predicting mechanical performance. Our results demonstrate that cell connectivity, beyond relative density alone, plays a central role in governing the mechanical response of metallic foams under compression.

The production of metallic foams is influenced by many aspects. Among other factors, compaction plays an important role in the powder metallurgical production of foamable precursors. A powder compaction metallurgical method, known as current‐activated pressure‐assisted densification (CAPAD), is applied to enhance the compaction of metal foam precursors. This method improves precursor quality by achieving higher density, lower electrical resistivity, and more uniform pore nucleation in the resulting foams. Changes in the microstructure, constituents’ distribution, and their influence on the foam nucleation and expansion behavior are investigated. Compared to traditional uniaxial hot pressing (UHP) methods, CAPAD operates at significantly lower pressures than UHP, reducing energy consumption and processing time. The reduced operational demands and improved material properties highlight CAPAD's potential as a cost‐effective and efficient alternative to conventional compaction techniques.

Understanding material’s micro- and macrostructure is key to linking inner structure information to large-scale physical properties and function. An improvement of the microstructure during production processes can lead to materials with enhanced physical properties or even to the development of new classes of materials. In this paper, we develop an ‘accurate’ topological model to describe the dual neighborhood structure of foams and other cellular materials (e.g. plant cell clusters or polycrystalline materials like steel, rocks, and ceramics) obtained by x-ray tomography, adhering to Plateau’s rules: four pores meet at a vertex, and three meet along an edge. While the degree of non-convexity in the pores is a priori unknown, our approach is designed for structures without extreme geometric irregularities (e.g. tangled pores). It provides meaningful combinatorial-numerical validation in such cases but may not extend reliably to more complex geometries. To illustrate our method, we analyze a sample of aluminum foam comprising 1911 pores. The resulting abstract combinatorial foam structure partially aligns with that of the associated power diagram—sharing 51.45% of the tetrahedra in the dual complex—but also reveals significant deviations.

This publication presents an improved manufacturing method for tetrahedral metal effect pigment particles that demonstrates reduced flowlines in injection-molded polymer components compared with conventional platelet-shaped pigment particles. The previously published cold forming process for tetrahedral particles, made entirely from aluminum, faced manufacturing challenges, resulting in a high reject rate due to particle adhesion to the micro-structured mold roller. In contrast, this study introduces a new manufacturing method for tetrahedral particles, now consisting of metallized UV-cured thermoset polymer. These particles, dispersed in amorphous matrix thermoplastics, have shown to maintain their shape during the injection molding process. The manufacturing technique for these novel particles is based on UV imprint lithography, omitting the reject rates compared with the previously presented cold rolling process of tetrahedral full aluminum particles. Thus, the novel manufacturing technique for tetrahedral pigment particles shows increased potential for automation through roll-to-roll manufacturing in the future.

This study applies extrusion-based additive manufacturing for the production of shape-defined, lightweight lignocellulose–fungal mycelium-based composites and pure 3D fungal mycelium skins, expanding the future applications of fungal materials.

For the development of aluminum scandium alloys to produce a hydrogen storage valves, various aluminum alloy series with different Sc and Zr contents are tested. The alloys are mainly characterized by hardness measurements and tensile tests. The hardening curves are recorded for different temperatures and compositions, and the selected parameters are validated with the corresponding mechanical tests. The alloys 5083 + 0.2% Sc and AlSi16Mg1Sc0.4 are selected for the production of hydrogen valves by forging and additive manufacturing.

The knowledge of underlying physical phenomena and the understanding of parameter dependencies are essential for the development of stable welding processes. Quantitative data based on a sensor-based approach are necessary to draw conclusions about the resulting quality. These are at the same time key factors for the optimization of industrial processes. The paper refers to this in the context of laser welding technology using superimposed dynamic beam oscillation of aluminum alloys. However, particularly die-cast aluminum is characterized by limited weldability due to entrapped gases, which lead to defects like high porosity and blow out formation along the weld seam. For the welding trails, a novel laser processing head was designed. The optics enables a synchronized and fast beam deflection in all three spatial directions. Therefore, a galvanometer scanner for x-y-oscillation was combined with a piezo-driven mirror for the beam movement in the z-direction. By means of in situ synchrotron x-ray imaging synchronized with recordings of acoustic process emissions and high-speed imaging of the melt pool, deep insights into the interactions of the laser beam and material could be investigated. The collected data show a clear correlation between oscillation parameters (frequency and amplitude) and the resulting weld seam quality. Furthermore, audio signal information provides an explicit link for different vapor capillary formations as well as melt flow fluctuations. The adapted process dynamics for dynamic beam oscillation welding enable a significant quality improvement and open up the possibility for efficient and safe process monitoring.

The phenomena occurring in a weld seam during advancement of a laser beam over a metallic component are still under dispute. The occurrence and evolution of porosity and the occasional blowout of melt need to be understood. Here, a recently developed X‐ray tomoscopy setup is applied, providing one hundred 3D images per second to capture the temporal evolution of the melt pool in an AlSi9Cu3(Fe) die‐casting while a laser beam advances. The number of pores, their size, shape and distribution are quantified with 10 ms time resolution and reflect a complex dynamic pattern. Apart from conventional welding, a variant involving a dynamic beam modulation superimposed onto the linear motion is studied. Reductions of porosity and surface roughness are observed and explained by increased pore mobility and stepwise degassing as the beam repeatedly cuts through pores. The keyhole formed in the melt pool integrated over 10 ms is represented in 3D.