Filtern
Dokumenttyp
Sprache
- Englisch (14)
Referierte Publikation
- ja (14) (entfernen)
Schlagworte
- Additive manufacturing (7)
- Heat accumulation (4)
- Laser powder bed fusion (4)
- AISI 316L (3)
- Additive Manufacturing (3)
- In situ monitoring (3)
- AGIL (2)
- Additive manufacturing (AM) (2)
- Infrared thermography (2)
- Laser Powder Bed Fusion (2)
- Representative specimens (2)
- Selective laser melting (SLM) (2)
- Thermal history (2)
- Thermography (2)
- 316L (1)
- Cellular substructure (1)
- Computed Tomography (1)
- Computed tomography (1)
- Convolutional neural networks (CNN) (1)
- Creep (1)
- Creep behavior (1)
- Defect detection (1)
- Diffraction (1)
- Elastic modulus (1)
- Electron backscatter diffraction (1)
- Fatigue damage (1)
- Finite element method (1)
- Flaw detection (1)
- Heat treatment (1)
- IN 718 (1)
- Image registration (1)
- In-situ monitoring (1)
- In-situ process monitoring (1)
- Inconel 718 (1)
- Inter layer time (1)
- Inter-layer time (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser Powder Bed Fusion (PBF-LB/M, L-PBF) (1)
- Laser beam melting (LBM) (1)
- Laser powder bed fusion (L-PBF) (1)
- Low-cycle fatigue (1)
- Machine learning (1)
- Microstructure (1)
- Online monitoring (1)
- Optical Tomography (1)
- PBF-LB/M/316L (1)
- Process monitoring (1)
- Process simulation (1)
- Reference data (1)
- Residual Stress (1)
- SWIR camera (1)
- SWIR thermography (1)
- Selective Laser Melting (SLM) (1)
- Shear modulus (1)
- Stainless Steel (1)
- Temperature dependence (1)
- Tensile strength (1)
- Tensile testing (1)
- Ti-6Al-4V (1)
- X-ray and Neutron Diffraction (1)
- X-ray computed tomography (XCT) (1)
- Young's modulus (1)
- infrared Thermography (1)
Organisationseinheit der BAM
- 9.6 Additive Fertigung metallischer Komponenten (14) (entfernen)
This study investigates the room‐ and high‐temperature (650 °C) tensile and low‐cycle‐fatigue behavior of Inconel 718 produced by laser powder bed fusion (PBF‐LB/M) with a four‐step heat treatment and compares the results to the conventional wrought material. The microstructure after heat treatment is characterized on different length scales. Compared to the wrought variant, the elastic and yield properties are comparable at both test temperatures while tensile strength, ductility, and strain hardening capacity are lower. The fatigue life of the PBF‐LB/M variant at room temperature is slightly lower than that of the wrought material, while at 650 °C, it is vice versa. The cyclic stress response for both material variants is characterized by cyclic softening, which is more pronounced at the higher test temperature. High strain amplitudes (≥0.7%) at room temperature and especially a high testing temperature result in the formation of multiple secondary cracks at the transitions of regions comprising predominantly elongated grain morphology and columns of stacked grains with ripple patterns in the PBF‐LB/M material. This observation and pronounced crack branching and deflection indicate that the cracks are controlled by sharp micromechanical gradients and local crystallite clusters.
Laser powder bed fusion is used to create near net shape metal parts with a high degree of freedom in geometry design. When it comes to the production of safety critical components, a strict quality assurance is mandatory. An alternative to cost-intensive non-destructive testing of the produced parts is the utilization of in-situ process monitoring techniques. The formation of defects is linked to deviations of the local thermal history of the part from standard conditions. Therefore, one of the most promising monitoring techniques in additive manufacturing is thermography. In this study, features extracted from thermographic data are utilized to investigate the thermal history of cylindrical metal parts. The influence of process parameters, part geometry and scan strategy on the local heat distribution and on the resulting part porosity are presented. The suitability of the extracted features for in-situ process monitoring is discussed.
Additive manufacturing (AM) of metals and in particular laser powder bed fusion (LPBF) enables a degree of freedom in design unparalleled by conventional subtractive methods. To ensure that the designed precision is matched by the produced LPBF parts, a full understanding of the interaction between the laser and the feedstock powder is needed. It has been shown that the laser also melts subjacent layers of material underneath. This effect plays a key role when designing small cavities or overhanging structures, because, in these cases, the material underneath is feed-stock powder. In this study, we quantify the extension of the melt pool during laser illumination of powder layers and the defect spatial distribution in a cylindrical specimen. During the LPBF process, several layers were intentionally not exposed to the laser beam at various locations, while the build process was monitored by thermography and optical tomography. The cylinder was finally scanned by X-ray computed tomography (XCT). To correlate the positions of the unmolten layers in the part, a staircase was manufactured around the cylinder for easier registration. The results show that healing among layers occurs if a scan strategy is applied, where the orientation of the hatches is changed for each subsequent layer. They also show that small pores and surface roughness of solidified material below a thick layer of unmolten material (>200 µm) serve as seeding points for larger voids. The orientation of the first two layers fully exposed after a thick layer of unmolten powder shapes the orientation of these voids, created by a lack of fusion.
The triaxial distribution of the residual stress in laser powder bed fused austenitic steel 316L was determined by X-ray and neutron diffraction. The residual stress analysis results were linked to the thermal history of the specimens, which were manufactured with varying inter-layer-times and scanning velocities. A clear link between the in-process temperature of the specimens and the residual stress was found, based on in-situ monitoring data.