Fracture behavior of high strength pearlitic steel wires

Steel wires are widely used in various industrial applications. Hence, the drawing process and the resulting mechanical properties are of significant scientific and industrial importance. In this investigation the focus is on pearlitic steel wires with relatively high drawing strains and resulting high ultimate tensile strengths up to several GPa. The fracture behavior was investigated for two different wires with a drawing strain of 3.10 and 6.52 with a diameter of about 100 µm and 20 µm, respectively. The resulting ultimate tensile strength varies between 4 and 7 GPa [1]. The fracture toughness was measured with crack propagation direction in drawing direction and perpendicular to it. To test the fracture toughness of the samples in drawing direction micro-bending beams were fabricated utilizing a focused ion beam (FIB). For investigating the direction perpendicular to the drawing direction, the wires were notched with a FIB and tested under tensile and bending loading. The fracture toughness experiments for both directions were performed in-situ in the SEM. In addition, some samples of the perpendicular direction were tested ex-situ as well. The results of the fracture experiments show a strong anisotropy of the fracture behavior. It was revealed that in drawing direction the wires show a significantly lower fracture toughness than perpendicular to it. This is further supported by the in-situ and ex-situ bending experiments of the second testing direction, where the crack kinks into the drawing direction

Autonomous weapons systems: UN expert talks facing failure time to consider alternative formats

The Group of Governmental Experts (GGE) has been discussing autonomous weapons systems (AWS) in the UN arms control context since 2017. Russia boycotted the latest round of talks in Geneva in March, in connection with its 24 February 2022 invasion of Ukraine. Regulation of AWS is an increasingly remote prospect, and some representatives even admit privately that the talks may have failed. The new German gov­ern­­ment’s commitment to work to outlaw AWS is increasingly looking like a labour of Sisyphus. Given that the GGE requires unanimity, but constructive cooperation with Russia is off the table for the foreseeable, other forums will need to be found for the international debate on AWS control. Germany must prepare for options within NATO, the European Union and the United Nations. It is clear that any meaningful process presupposes coherent coordination with the NATO partners on all levels. In order to achieve that, Germany must first develop a clear national position on AWS. (author's abstract