Matthias Merzkirch

Tensile behaviour of spring steel wire reinforced EN AW-6082

The reinforcement of composite aluminium extrusions offers a high potential regarding weight reduction and improvement of mechanical properties, which is essential for components in lightweight constructions. The current work gives an overview of the quasi-static properties of spring steel wire reinforced EN AW-6082 with varying reinforcing ratio. The deformation and damage behaviour is investigated in detail for a reinforcing ratio of 11.1 vol.%. It is shown that the relatively ductile behaviour of the spring steel wire leads to multiple necking resulting in higher strains than expected. Current models are expanded and modified for a proper adaptation to the material system.

Applications of high-power diode lasers for aluminum welding

Industries worldwide are confronted with the need for an increased use of aluminum alloys in various applications. Therefore the requirements result in the necessity for a multitude of joining and welding innovations. Applications of modern aluminum alloys are not constricted to common components anymore. In fact, they are used in ever more complex lightweight structures. However, this complexity has to be fulfilled by a higher geometric flexibility in laser welding and represents a major challenge for new approaches in working lightweight structures. The present work includes the welding of aluminum utilizing Bifocal Hybrid Laser Welding (BHLW) and a 6 kW high power diode laser (HPDL) for welding. The welding setups allow for welded butt- and fillet-welds of tubes under consideration of the hardly fusion weldable alloy AA6060. Welded joints of AA6060 are investigated metallographically in regard to the influence of process parameters like intensity and the interconnected penetration. The weldability is characterized by qualitative investigations of the microstructure as well as the mechanical behavior under quasistatic loading. The investigations result in an adequate welding process for AA6060.

Numerical analysis to study the tensile behaviour of a spring-steel-wire-reinforced aluminium alloy metal matrix composite

The reinforcement of composite extruded light metal profiles offers a high potential in terms of weight reduction and the improvement of mechanical properties, both of which are essential for components in lightweight space frame constructions. In a previous study, the mechanical properties under tensile loading of spring-steel (301SS)-wire-reinforced aluminium extrusions based on EN AW-6082 were investigated in terms of a varying reinforcing ratio. The aim of the current study is to minimize the effort needed to gather mechanical data by calculation of the deformation and damage behaviour under tensile loading of 11.1 vol.% spring-steel-reinforced EN AW-6082. The simulation of the push-out test provided specific parameters concerning the interfacial properties – like the radial strength – needed for modelling the tensile test. It could be shown that the simulation of the tensile test is in good agreement with the experimental results, concerning quantitative values (stress–strain curve) and qualitative behaviour (necking and debonding).

Micro-Computed Tomography Image Based Numerical Elastic Homogenization of MMCs

Properties of an interpenetrating metal–ceramic composite with freeze-cast preforms are investigated. For the estimation of elastic properties of the composite numerical homogenization approaches for 2D and 3D finite element models are implemented. The FE models are created based on micro-computed tomography (μCT) images. The results of the numerical 2D and 3D modeling coincide and are in good agreement with available experimental measurements of elastic properties.

Documentation of the Corrosion of Composite-Extruded Aluminium Matrix Extrusions using the Push-Out Test

A possibility to increase both stiffness and strength of aluminium-based structures for the application in lightweight profiles for vehicle space frames is the use of composite extrusions in which high-strength metallic reinforcements are incorporated. Within the scope of the present investigations, composite-extruded profiles with wire-reinforcements made of austenitic spring steel 1.4310 (X10CrNi18-8), in an aluminium matrix AA6060 (AlMgSi0.5), which were exposed to different corrosive media for different times, were characterised in terms of the debonding shear strength using the push-out-technique. The formation of a galvanic couple could be conceived mathematically in regard of terms describing the formation of a shear-impeding layer and the corrosive attack. Thereby the parameters for the different media could be determined.

Interpenetrating Freeze Cast Composites: Correlation between Structural and Mechanical Characteristics

Ceramic freeze cast preforms based on alumina show an anisotropic behavior due to directional freezing during preform production. Beside the specific characteristics such as alumina content and lamellae spacing also the distribution of the so-called domains – regions with a relatively homogeneous orientation of alumina lamellae – play an important role considering stiffness and strength. The gas pressure infiltration process was used for infiltrating the freeze cast preforms with a eutectic aluminum/silicon alloy with a low melting point. Selected regions taken from the freeze cast preform have been analyzed via X-ray micro computed tomography (µCT) prior to the infiltration due to a higher contrast in comparison to the infiltrated preforms. The orientation of the lamellae has been determined from the three dimensional data with an algorithm which is based on the structure tensor. The mechanical stability - in terms of the strength - of the infiltrated preforms has been quantified via quasi static compression tests on cuboid samples. The results show a good agreement between the orientation of the lamellae distribution and the maximum strength of the preform which could also be verified using an analytical model.