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SUMMARYA novel approach to simulate crack growth within an extended finite element framework is presented. The introduced approach combines the material force concept and the extended finite element method (xFEM) that is not straight forward and faces the major problem that a crack tip node, which is required for the evaluation of the material force, is not available within an xFEM framework.The introduced concept enables an efficient single step evaluation of the crack state and the crack growth direction based on a continuum mechanics approach and represents an alternative to the common procedure of using the stress intensity factor solution within a stress or energy-based empirical formulation for the determination of the crack growth direction. Two different approaches are introduced that evaluate the crack tip material force within the xFEM based on a domain or contour approach, both providing equivalent results. After an evaluation of the method, a major focus is set on crack growth investigations with increased complexity, including mixed mode loading and crack interaction with other discontinuities. The influence of different evaluation parameters is studied by comparing the results with empirical, experimental and alternative numerical solutions and confirms the applicability and capability of the proposed combination of both concepts.

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In this paper, a surrogate model approach for non-linear aerodynamics is presented in order to reduce the computational effort of coupled aeroelastic analyses. The usability of the approach is demonstrated in static as well as transient aeroelastic analyses of the HIRENASD wingfuselage configuration. Furthermore, it is shown that the surrogate model approach is able to cover variations of flow conditions at a fixed Mach and Reynolds number.

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This paper describes the simulation approach for the analysis of fluid structure interactions(FSI) of rocket thrust chambers. It is based on a partitioned approach and includes several buildingblocks: codes for computational fluid dynamics (CFD) and computational structural mechanics(CSM) as well as techniques to handle non conforming surface grid and to solve the nonlinear coupledequations in time. One target application is the life time prediction and to simulate the structuralfatigue behaviour. Thus, cyclic loading conditions are important and are the motivation for a surrogatemodel, which is the focus of this contribution. It uses nonlinear mapping algorithms between surfacetemperature and heat flux in combination with a reduction of dimensionality via proper orthognal decomposition(POD). It can be used as a replacement of the time consuming CFD code and acceleratesthe FSI analysis several orders in time. Some applications regarding the validation of the FSI softwareenvironment finalize the description of the simulation approach showing that the simulation ofcomplex and multidisciplinary problems is laborious and needs a widespread understanding.