07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/8
Browse
26 results
Search Results
Item Open Access Local laser heat treatment of AlSi10Mg as-built parts produced by Laser Powder Bed Fusion(2024) Kramer, Steffen; Jarwitz, Michael; Schulze, Volker; Zanger, FrederikToday, complex structural components for lightweight applications are frequently manufactured by laser powder bed fusion (PBF-LB), often using aluminum alloys such as AlSi10Mg. However, the application of cyclic load cases can be challenging as PBF-LB produced AlSi10Mg parts typically have low ductility and corresponding brittle failure behavior in the as-built condition. Therefore, this paper presents investigations on the feasibility of a laser heat treatment of PBF-LB produced AlSi10Mg parts to locally increase the ductility and decrease the hardness in critical areas. Potential heat treatment process parameters were derived theoretically based on the temperature fields in the material calculated assuming three-dimensional heat conduction and a moving heat source. PBF-LB produced specimens were then laser heat treated at varying laser power and scan speed. Hardness measurements on metallographic cross sections showed hardness reductions of over 35 % without inducing hydrogen pore growth.Item Open Access General mathematical model for the period chirp in interference lithography(2023) Bienert, Florian; Graf, Thomas; Abdou Ahmed, MarwanItem Open Access Influence of geometry variations during pyrometric temperature measurement in laser material processing(2024) Traunecker, David; Jarwitz, Michael; Michalowski, AndreasItem Open Access Stream finishing of additively manufactured AlSi10Mg PBF-LB parts: influence on surface quality and fatigue behaviour(2024) Wexel, Helena; Kramer, Steffen; Schubert, Johannes; Schulze, Volker; Zanger, FrederikItem Open Access Comparison of in-process laser drying with furnace and vacuum drying to reduce moisture of AlSi10Mg powder processed in Laser Powder Bed Fusion(2024) Lubkowitz, Victor; Fayner, Leonie; Kramer, Steffen; Schulze, Volker; Zanger, FrederikIn most powder bed-based laser melting systems (PBF-LB), metal powders must be handled without inertization but in an air atmosphere for a short time, increasing the AlSi10Mg powder moisture and reducing the achievable component density. Consequently, different drying methods were investigated. Drying in a furnace with an inert atmosphere, using a vacuum to evaporate the water at low temperatures, and vaporizing moisture layerwise from the spreaded powder with a defocused, low-power laser beam as a further process step of the PBF-LB process. Therefore, four different moisturized powders, which were dried with different settings for the drying methods, are analyzed. All drying methods reduce the moisture content of the powder, with in-process drying being the most effective. Due to the oxide layer growth around the particles during furnace and vacuum drying, the achievable sample density after drying is worse. In-process drying with low energy density is the best option to reach a reduction of hydrogen pores and an increase of density.Item Open Access Different coupling mechanisms for a novel modular plate in acetabular fractures : a comparison using a laparoscopic model(2024) Menger, Maximilian M.; Herath, Steven C.; Ellmerer, Andreas E.; Trulson, Alexander; Hoßfeld, Max; Leis, Artur; Ollig, Annika; Histing, Tina; Küper, Markus A.; Audretsch, Christof K.Introduction: Acetabular fractures are among the most challenging injuries in traumatology. The complex anatomy usually requires extensive surgical approaches baring the risk for iatrogenic damage to surrounding neurovascular structures. As a viable alternative, minimally invasive endoscopic techniques have emerged during the recent years. This paper reports on the feasibility of different coupling mechanisms for a novel suprapectineal plate especially designed for minimally invasive acetabular surgery. Methods: A total number of 34 participants contributed to the present study, who differed in their arthroscopic and surgical experience. A laparoscopic model was used to compare four different coupling mechanisms by the number of failed attempts, the time required for plate fixation, the influence of surgical experience as well as the learning success for each individual coupling mechanism. Moreover, the feasibility of each mechanism was evaluated by a questionnaire. Results: The results demonstrate that plates employing grooved and pressure-sliding coupling mechanisms exhibit fewer failed attempts and reduce trial times, especially in contrast to sole sliding mechanisms. Furthermore, our study revealed that proficiency in endoscopic procedures significantly influenced the outcome. Notably, the subjective evaluation of the participants show that the pressure base and pressure-slide base plate designs are the most supportive and feasible designs. Conclusions: In summary, the present study evaluates for the first-time different plate and coupling designs for minimal-invasive surgery, indicating a superior feasibility for plates with a grooved and pressure-sliding mechanism.Item Open Access Generation of a radially polarized beam in a polycrystalline ceramic Yb:Lu2O3 thin-disk laser(2023) Didychenko, Denys; Esser, Stefan; Beirow, Frieder; Savchenko, Anton; Pruss, Christof; Graf, Thomas; Abdou Ahmed, MarwanAbstractWe report on the generation of a continuous-wave (CW) radially polarized beam with an Yb:Lu2O3 polycrystalline ceramic disk in a thin-disk laser (TDL) oscillator. A circular grating-waveguide mirror (CGWM) with a high polarization discrimination given by a reflectivity difference between the two orthogonal polarization states of 44.6% was used as a polarization-selective cavity end-mirror. An output power of 175 W was achieved with an optical efficiency of 39.6%. A high degree of radial polarization of 96.2% and a beam propagation factor of M2hor. = 2.05 and M2ver. = 2.32 were measured at the maximum output power.Item Open Access Feasibility assessment of parallelized helical drilling(2023) Brinkmeier, David; Onuseit, Volkher; Graf, ThomasItem Open Access Self-shielding of X-ray emission from ultrafast laser processing due to geometrical changes of the interaction zone(2024) Holland, Julian; Hagenlocher, Christian; Weber, Rudolf; Graf, ThomasMaterials processing with ultrashort laser pulses is one of the most important approaches when it comes to machining with very high accuracy. High pulse repetition rates and high average laser power can be used to attain high productivity. By tightly focusing the laser beam, the irradiances on the workpiece can exceed 1013 W/cm2, and thus cause usually unwanted X-ray emission. Pulsed laser processing of micro holes exhibits two typical features: a gradual increase in the irradiated surface within the hole and, with this, a decrease in the local irradiance. This and the shielding by the surrounding material diminishes the amount of ionizing radiation emitted from the process; therefore, both effects lead to a reduction in the potential X-ray exposure of an operator or any nearby person. The present study was performed to quantify this self-shielding of the X-ray emission from laser-drilled micro holes. Percussion drilling in standard air atmosphere was investigated using a laser with a wavelength of 800 nm a pulse duration of 1 ps, a repetition rate of 1 kHz, and with irradiances of up to 1.1·1014 W/cm. The X-ray emission was measured by means of a spectrometer. In addition to the experimental results, we present a model to predict the expected X-ray emission at different angles to the surface. These calculations are based on raytracing simulations to obtain the local irradiance, from which the local X-ray emission inside the holes can be calculated. It was found that the X-ray exposure measured in the surroundings strongly depends on the geometry of the hole and the measuring direction, as predicted by the theoretical model.Item Open Access Enhanced scaling of material removal rate with high surface quality through combined laser processes(2023) Buser, Matthias; Hofele, Markus; Menold, Tobias; Riegel, Harald; Michalowski, AndreasAbstractIn the field of ultrashort pulse laser processing, the effective utilization of average power provided by todays laser systems presents an almost unsolvable challenge. This study aims to address this challenge in the context of laser volume ablation. We propose a solution for utilization of high average power while producing a high-quality finish, even when starting from arbitrary surfaces. The approach combines closed loop laser volume ablation, laser cleaning and laser polishing in a subsequent process strategy. The closed loop approach enables ablative laser processes to be used to produce precise target geometries and surfaces, even if the initial geometry of the component is very different from the target geometry. One application example is the post-processing of components manufactured using additive processes such as laser powder bed fusion. Therefore, we demonstrate automated removal of support structures and finishing of a sample made of AlSi10Mg material by laser powder bed fusion. The combination of laser ablation and laser polishing made it possible to significantly increase the productivity of the post-processing and achieving a surface roughness of Ra = 0.3 µm.
- «
- 1 (current)
- 2
- 3
- »