ABSTRACT
The rise of additive manufacturing, particularly laser powder bed fusion, has enabled new degrees of freedom in terms of design and functionality. Notably high-performance industries such as the medical, automotive, and aerospace industries are on the edge of broad industrial application. However, the quality standards required for these industries are not yet entirely met. Process-related temperature-induced residual stresses within the component can lead to warpage and deformations causing rejects. Support structures are a vital counter measure to absorb these residual stresses and ensure the required print quality. While the current industrial standard for support structure generation mainly focuses on geometrical boundary conditions, this study presents a simulation-based approach taking into account residual stresses. The proposed approach determines the stress distribution during the process from a thermomechanical finite element process simulation and uses these results for the allocation of topology-optimized stackable unit cells. To assure a reliable connection to the component while offering easy removability of the support, different connection support structures in the interface area were tested and integrated in the proposed approach. The result is a robust tailored lattice support structure minimizing residual stresses to achieve high component quality, while focusing on cost-efficiency factors such as minimal material usage, easy support removability, and numerical efficiency. Finally, the proposed approach was tested on a demonstrator part printed from AlSi10Mg.
ABSTRACT
A recent development in ground-based remote sensing of atmospheric constituents by UV-visible absorption measurements of scattered light is the simultaneous use of several horizon viewing directions in addition to the traditional zenith-sky pointing. The different light paths through the atmosphere enable the vertical distribution of some atmospheric absorbers, such as NO2, BrO, or O3, to be retrieved. This approach has recently been implemented on an airborne platform. This novel instrument, the airborne multiaxis differential optical absorption spectrometer (AMAXDOAS), has been flown for the first time. In this study, the amount of profile information that can be retrieved from such measurements is investigated for the trace gas NO2. Sensitivity studies on synthetic data are performed for a variety of representative measurement conditions including two wavelengths, one in the UV and one in the visible, two different surface spectral reflectances, various lines of sight (LOSs), and for two different flight altitudes. The results demonstrate that the AMAXDOAS measurements contain useful profile information, mainly at flight altitude and below the aircraft. Depending on wavelength and LOS used, the vertical resolution of the retrieved profiles is as good as 2 km near flight altitude. Above 14 km the profile information content of AMAXDOAS measurements is sparse. Airborne multiaxis measurements are thus a promising tool for atmospheric studies in the troposphere and the upper troposphere and lower stratosphere region.
