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Static and dynamic load superposition in spacecraft structural analysis
Vaquer-Araujo, Xavier,Schottle, Florian,Kommer, Andreas,Konrad, Werner Techno-Press 2018 Advances in aircraft and spacecraft science Vol.5 No.2
In mechanical analysis of spacecraft structures situations appear where static and dynamic loads must be considered simultaneously. This could be necessary either by load definition or preloaded structures. The superposition of these environments has an impact on the load and stress distribution of the analysed structures. However, this superposition cannot be done by adding both load contributions directly. As an example, to compute equivalent Von Mises stresses, the phase information must be taken into account in the stress tensor superposition. Finite Element based frequency response solvers do not allow the calculation of superposed static and dynamic responses. A manual combination of loads in a post-processing task is required. In this paper, procedures for static and harmonic loads superposition are presented and supported by analytical and finite element-based examples. The aim of the paper is to provide evidence of the risks of using different superposition techniques. Real application examples such as preloaded mechanism structures and propulsion system tubing assemblies are provided. This study has been performed by the Structural Engineering department of Airbus Defence and Space GmbH Friedrichshafen.
Comparison of mass operator methods considering test uncertainties
Olympio, K.R.,Blender, F.,Holz, M.,Kommer, A.,Vetter, R. Techno-Press 2018 Advances in aircraft and spacecraft science Vol.5 No.2
In the space industry, structures undergo several vibration and acoustic tests in order to verify their design and give confidence that they will survive the launch and other critical in-orbit dynamic scenarios. At component level, vibration tests are conducted with the aim to reach local or global interface loads without exceeding the design loads. So, it is often necessary to control and limit the input based on a load criterion. This means the test engineer should be able to assess the interface loads, even when load cannot be measured. This paper presents various approaches to evaluate interface loads using measured accelerations and by referring to mass operators. Various methods, from curve fitting techniques to finite element-based methods are presented. The methods are compared using signals with known imperfection to identify strengths and weaknesses of each mass operator definition.
Muscular and collagenous cerebellar choristoma in a dog
Angel Ripplinger,Stella Maris Pereira de Melo,Dênis Antonio Ferrarin,Marcelo Luís Schwab,Mathias Reginatto Wrzesinski,Júlia da Silva Rauber,Mariana Martins Flores,Glaucia Denise Kommers,Alexandre Mazz 대한수의학회 2022 Journal of Veterinary Science Vol.23 No.2
This report aims to describe the first case of muscular and collagenous choristoma in a dog. A 10-yr-old female mixed-breed dog presented with lateral recumbence, vocalization, positional vertical nystagmus, divergent strabismus, anisocoria, and status epilepticus. The clinical condition evolved to stupor and ultimately, death. Necropsy revealed a white mass causing an irregular increase in the volume of the cerebellar vermis. In histological analysis, a well circumscribed, unencapsulated mass was observed in the cerebellum, consisting of fibers of striated skeletal muscle and collagen fibers, mostly mineralized. Based on the histopathological and histochemical findings, a diagnosis of muscular and collagenous cerebellar choristoma was made.