No abstract

Systematic investigations of hardened cement paste, high-performance concrete and mortar with and without microfibers, subjected to static and cyclic tensile loadings, were conducted. The material degradation was investigated by means of microscopic analyses of the microcrack development. Notched specimens were subjected to a predefined number of load cycles. A nonsteady increase of microcracking with increasing load cycles was observed in high-strength concrete, whereas the addition of steel fibers lead to a steady increase of microcracks. Highstrength mortar often showed premature failure, while addition of steel micro fibers allowed completion of the cyclic tests. To obtain a deeper insight into physical mechanisms governing fatigue and structural failure, high-performance concrete (HPC) and fiber-reinforced concrete (FRC) under static and cyclic tensile loadings have been modeled using cohesive interface finite elements, micromechanics, and a fiber-bundle model. Analysis of model predictions shows the significance of strength disorder and fiber properties on the structural behavior. K E Y W O R D Scyclic loading, discrete crack model, disorder, finite element method, steel micro fibers

For the precise machining of demanding materials, wire electrical discharge machining (WEDM) is a flexible and often irreplaceable manufacturing process. In order to enhance productivity as the main focus of the wire EDM process, the advancement of the fundamental procedural understanding is of decisive importance. In order to be able to energetically evaluate the removal process, the individual energetic contributors of the process hence the individual discharges need to be understood in terms of their contribution to material removal. In this paper, an experimental setup is presented, which permits the generation of individual discharges on a modern industrial wire EDM machine tool. For three different wire electrodes, the correlation of the discharge energy and the individual removal volume is quantitatively described, showing that coated wires achieve a significantly higher energy-specific removal. Furthermore the removal efficiency is defined as a key figure to transfer the findings to the continuous process and compare theoretical and effective removal rate.

In the present study, the capability of high-strength short steel fibers to control the degradation in high-performance concrete was experimentally examined and numerically simulated. To this end, notched prismatic high-performance concrete specimens with (HPSFRC) and without (HPC) short steel fibers were subjected to static and cyclic tensile tests up to 100,000 cycles. The cyclic tests showed that the rate of strain increase was lower for HPSFRC specimens and that the strain stagnated after around 10,000 cycles, which was not the case with HPC specimens. The microscopic examinations showed that in HPSFRC, a larger number of microcracks developed, but they had a smaller total surface area than the microcracks in the HPC. To further investigate the influence of fibers on the behavior of HPSFRC in the cracked state, displacement-controlled crack opening tests, as well as numerical simulations thereof, were carried out. Experiments have shown, and the numerical simulations have confirmed, that the inclusion of short steel fibers did not significantly affect the ultimate strength; however, it notably increased the post-cracking ductility of the material. Finally, the unloading/reloading behavior was examined, and it was observed that the unloading stiffness was stable even for significant crack openings; however, the hysteresis loops due to unloading/reloading were very small.

This paper presents the underlying method of a proposed digital twin for proactive production planning. We derived the method based on a requirements analysis considering the challenges in maritime production. Using real-time production feedback data, alternative production scenarios are identified to prevent disruptions and delays in manufacturing and assembly. As part of the ProProS research project, the method is implemented and validated through the development of the digital twin, which offers a platform for the realization of further use cases to be diffused into industrial applications.