@article{Staat2021,
  author    = {Staat, Manfred},
  title     = {An extension strain type Mohr-Coulomb criterion},
  series = {Rock mechanics and rock engineering},
  volume    = {54},
  journal   = {Rock mechanics and rock engineering},
  number    = {12},
  publisher = {Springer Nature},
  address   = {Cham},
  issn      = {1434-453X},
  doi       = {10.1007/s00603-021-02608-7},
  pages     = {6207 -- 6233},
  year      = {2021},
  abstract  = {Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr-Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.},
  language  = {en}
}
@article{DachwaldUlamecPostbergetal.2020,
  author    = {Dachwald, Bernd and Ulamec, Stephan and Postberg, Frank and Sohl, Frank and Vera, Jean-Pierre de and Christoph, Waldmann and Lorenz, Ralph D. and Hellard, Hugo and Biele, Jens and Rettberg, Petra},
  title     = {Key technologies and instrumentation for subsurface exploration of ocean worlds},
  series = {Space Science Reviews},
  volume    = {216},
  journal   = {Space Science Reviews},
  number    = {Art. 83},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {1572-9672},
  doi       = {10.1007/s11214-020-00707-5},
  pages     = {45},
  year      = {2020},
  abstract  = {In this chapter, the key technologies and the instrumentation required for the subsurface exploration of ocean worlds are discussed. The focus is laid on Jupiter's moon Europa and Saturn's moon Enceladus because they have the highest potential for such missions in the near future. The exploration of their oceans requires landing on the surface, penetrating the thick ice shell with an ice-penetrating probe, and probably diving with an underwater vehicle through dozens of kilometers of water to the ocean floor, to have the chance to find life, if it exists. Technologically, such missions are extremely challenging. The required key technologies include power generation, communications, pressure resistance, radiation hardness, corrosion protection, navigation, miniaturization, autonomy, and sterilization and cleaning. Simpler mission concepts involve impactors and penetrators or - in the case of Enceladus - plume-fly-through missions.},
  language  = {en}
}
@inproceedings{BaaderReiswichBartschetal.2018,
  author    = {Baader, Fabian and Reiswich, M. and Bartsch, M. and Keller, D. and Tiede, E. and Keck, G. and Demircian, A. and Friedrich, M. and Dachwald, Bernd and Sch{\"u}ller, K. and Lehmann, R. and Chojetzki, R. and Durand, C. and Rapp, L. and Kowalski, Julia and F{\"o}rstner, R.},
  title     = {VIPER - Student research on extraterrestrical ice penetration technology},
  series = {Proceedings of the 2nd Symposium on Space Educational Activities},
  booktitle = {Proceedings of the 2nd Symposium on Space Educational Activities},
  pages     = {1 -- 6},
  year      = {2018},
  abstract  = {Recent analysis of scientific data from Cassini and earth-based observations gave evidence for a global ocean under a surrounding solid ice shell on Saturn's moon Enceladus. Images of Enceladus' South Pole showed several fissures in the ice shell with plumes constantly exhausting frozen water particles, building up the E-Ring, one of the outer rings of Saturn. In this southern region of Enceladus, the ice shell is considered to be as thin as 2 km, about an order of magnitude thinner than on the rest of the moon. Under the ice shell, there is a global ocean consisting of liquid water. Scientists are discussing different approaches the possibilities of taking samples of water, i.e. by melting through the ice using a melting probe. FH Aachen UAS developed a prototype of maneuverable melting probe which can navigate through the ice that has already been tested successfully in a terrestrial environment. This means no atmosphere and or ambient pressure, low ice temperatures of around 100 to 150K (near the South Pole) and a very low gravity of 0,114 m/s^2 or 1100 μg. Two of these influencing measures are about to be investigated at FH Aachen UAS in 2017, low ice temperature and low ambient pressure below the triple point of water. Low gravity cannot be easily simulated inside a large experiment chamber, though. Numerical simulations of the melting process at RWTH Aachen however are showing a gravity dependence of melting behavior. Considering this aspect, VIPER provides a link between large-scale experimental simulations at FH Aachen UAS and numerical simulations at RWTH Aachen. To analyze the melting process, about 90 seconds of experiment time in reduced gravity and low ambient pressure is provided by the REXUS rocket. In this time frame, the melting speed and contact force between ice and probes are measured, as well as heating power and a two-dimensional array of ice temperatures. Additionally, visual and infrared cameras are used to observe the melting process.},
  language  = {en}
}
@inproceedings{JungFrotscherStaat2018,
  author    = {Jung, Alexander and Frotscher, Ralf and Staat, Manfred},
  title     = {Electromechanical model of hiPSC-derived ventricular cardiomyocytes cocultured with fibroblasts},
  series = {6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7), 11-15 June 2018, Glasgow, UK},
  booktitle = {6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7), 11-15 June 2018, Glasgow, UK},
  pages     = {11 Seiten},
  year      = {2018},
  abstract  = {The CellDrum provides an experimental setup to study the mechanical effects of fibroblasts co-cultured with hiPSC-derived ventricular cardiomyocytes. Multi-scale computational models based on the Finite Element Method are developed. Coupled electrical cardiomyocyte-fibroblast models (cell level) are embedded into reaction-diffusion equations (tissue level) which compute the propagation of the action potential in the cardiac tissue. Electromechanical coupling is realised by an excitation-contraction model (cell level) and the active stress arising during contraction is added to the passive stress in the force balance, which determines the tissue displacement (tissue level). Tissue parameters in the model can be identified experimentally to the specific sample.},
  language  = {en}
}
@inproceedings{StaatDuong2016,
  author    = {Staat, Manfred and Duong, Minh Tuan},
  title     = {Smoothed Finite Element Methods for Nonlinear Solid Mechanics Problems: 2D and 3D Case Studies},
  series = {Proceedings of the National Science and Technology Conference on Mechanical - Transportation Engineering (NSCMET 2016), 13th October 2016, Hanoi, Vietnam, Vol.2},
  booktitle = {Proceedings of the National Science and Technology Conference on Mechanical - Transportation Engineering (NSCMET 2016), 13th October 2016, Hanoi, Vietnam, Vol.2},
  pages     = {440 -- 445},
  year      = {2016},
  abstract  = {The Smoothed Finite Element Method (SFEM) is presented as an edge-based and a facebased techniques for 2D and 3D boundary value problems, respectively. SFEMs avoid shortcomings of the standard Finite Element Method (FEM) with lower order elements such as overly stiff behavior, poor stress solution, and locking effects. Based on the idea of averaging spatially the standard strain field of the FEM over so-called smoothing domains SFEM calculates the stiffness matrix for the same number of degrees of freedom (DOFs) as those of the FEM. However, the SFEMs significantly improve accuracy and convergence even for distorted meshes and/or nearly incompressible materials. Numerical results of the SFEMs for a cardiac tissue membrane (thin plate inflation) and an artery (tension of 3D tube) show clearly their advantageous properties in improving accuracy particularly for the distorted meshes and avoiding shear locking effects.},
  language  = {en}
}
@inproceedings{DuongJungFrotscheretal.2016,
  author    = {Duong, Minh Tuan and Jung, Alexander and Frotscher, Ralf and Staat, Manfred},
  title     = {A 3D electromechanical FEM-based model for cardiac tissue},
  series = {ECCOMAS Congress 2016, VII European Congress on Computational Methods in Applied Sciences and Engineering. Crete Island, Greece, 5-10 June 2016},
  booktitle = {ECCOMAS Congress 2016, VII European Congress on Computational Methods in Applied Sciences and Engineering. Crete Island, Greece, 5-10 June 2016},
  editor    = {Papadrakakis, M.},
  pages     = {13 S.},
  year      = {2016},
  language  = {en}
}
@inproceedings{FrotscherDuongStaat2015,
  author    = {Frotscher, Ralf and Duong, Minh Tuan and Staat, Manfred},
  title     = {Simulating beating cardiomyocytes with electromechanical coupling},
  series = {II. International Conference on Biomedical Technology : 28-30 October 2015 Hannover, Germany / T. Lenarz, P. Wriggers (Eds.)},
  booktitle = {II. International Conference on Biomedical Technology : 28-30 October 2015 Hannover, Germany / T. Lenarz, P. Wriggers (Eds.)},
  organization    = {International Conference on Biomedical Technology <2, 2015, Hannover>},
  pages     = {1 -- 2},
  year      = {2015},
  language  = {en}
}
@inproceedings{FrotscherStaat2015,
  author    = {Frotscher, Ralf and Staat, Manfred},
  title     = {Homogenization of a cardiac tissue construct},
  series = {CMBE15 : 4th International Conference on Computational \& Mathematical Biomedical Engineering ; 29th June - 1st July 2015 ; {\´E}cole Normale Sup{\´e}rieure de Cachan ; Cachan (Paris), France},
  booktitle = {CMBE15 : 4th International Conference on Computational \& Mathematical Biomedical Engineering ; 29th June - 1st July 2015 ; {\´E}cole Normale Sup{\´e}rieure de Cachan ; Cachan (Paris), France},
  editor    = {Nithiarasu, Perumal},
  publisher = {CMBE},
  address   = {[s.l.]},
  issn      = {2227-9385},
  pages     = {645 -- 648},
  year      = {2015},
  language  = {en}
}
@inproceedings{TranStaatStavroulakis2014,
  author    = {Tran, Ngoc Trinh and Staat, Manfred and Stavroulakis, G. E.},
  title     = {A multicriteria method for truss optimization},
  series = {11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona},
  booktitle = {11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona},
  editor    = {Onate, E.},
  organization    = {World Congress on Computational Mechanics <11, 2014, Barcelona>},
  pages     = {1 -- 12},
  year      = {2014},
  language  = {en}
}
@inproceedings{DuongStaat2014,
  author    = {Duong, Minh Tuan and Staat, Manfred},
  title     = {A face-based smoothed finite element method for hyperelastic models and tissue growth},
  series = {11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona},
  booktitle = {11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona},
  editor    = {Onate, E.},
  organization    = {World Congress on Computational Mechanics <11, 2014, Barcelona>},
  pages     = {1 -- 12},
  year      = {2014},
  language  = {en}
}