TY - CHAP
A1 - Lahmer, Tom
A1 - Ghorashi, Seyed Shahram
ED - Gürlebeck, Klaus
ED - Lahmer, Tom
ED - Werner, Frank
T1 - XFEM-BASED CRACK IDENTIFICATION APPLYING REGULARIZING METHODS IN A MULTILEVEL APPROACH
T2 - Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 04 - 06 2012, Bauhaus-University Weimar
N2 - Many structures in different engineering applications suffer from cracking. In order to make reliable prognosis about the serviceability of those structures it is of utmost importance to identify cracks as precisely as possible by non-destructive testing. A novel approach (XIGA), which combines the Isogeometric Analysis (IGA) and the Extended Finite Element Method (XFEM) is used for the forward problem, namely the analysis of a cracked material, see [1]. Applying the NURBS (Non-Uniform Rational B-Spline) based approach from IGA together with the XFEM allows to describe effectively arbitrarily shaped cracks and avoids the necessity of remeshing during the crack identification problem. We want to exploit these advantages for the inverse problem of detecting existing cracks by non-destructive testing, see e.g. [2]. The quality of the reconstructed cracks however depends on two major issues, namely the quality of the measured data (measurement error) and the discretization of the crack model. The first one will be taken into account by applying regularizing methods with a posteriori stopping criteria. The second one is critical in the sense that too few degrees of freedom, i.e. the number of control points of the NURBS, do not allow for a precise description of the crack. An increased number of control points, however, increases the number of unknowns in the inverse analysis and intensifies the ill-posedness. The trade-off between accuracy and stability is aimed to be found by applying an inverse multilevel algorithm [3, 4] where the identification is started with short knot vectors which successively will be enlarged during the identification process.
KW - Angewandte Informatik
KW - Angewandte Mathematik
KW - Computerunterstütztes Verfahren
Y1 - 2012
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-27717
UR - http://euklid.bauing.uni-weimar.de/ikm2012
SN - 1611-4086
ER -
TY - CHAP
A1 - Ghorashi, Seyed Shahram
A1 - Rabczuk, Timon
A1 - Ródenas García, Juan José
A1 - Lahmer, Tom
ED - Gürlebeck, Klaus
ED - Lahmer, Tom
ED - Werner, Frank
T1 - T-SPLINE BASED XIGA FOR ADAPTIVE MODELING OF CRACKED BODIES
T2 - Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 04 - 06 2012, Bauhaus-University Weimar
N2 - Safety operation of important civil structures such as bridges can be estimated by using fracture analysis. Since the analytical methods are not capable of solving many complicated engineering problems, numerical methods have been increasingly adopted. In this paper, a part of isotropic material which contains a crack is considered as a partial model and the proposed model quality is evaluated. EXtended IsoGeometric Analysis (XIGA) is a new developed numerical approach [1, 2] which benefits from advantages of its origins: eXtended Finite Element Method (XFEM) and IsoGeometric Analysis (IGA). It is capable of simulating crack propagation problems with no remeshing necessity and capturing singular field at the crack tip by using the crack tip enrichment functions. Also, exact representation of geometry is possible using only few elements. XIGA has also been successfully applied for fracture analysis of cracked orthotropic bodies [3] and for simulation of curved cracks [4]. XIGA applies NURBS functions for both geometry description and solution field approximation. The drawback of NURBS functions is that local refinement cannot be defined regarding that it is based on tensorproduct constructs unless multiple patches are used which has also some limitations. In this contribution, the XIGA is further developed to make the local refinement feasible by using Tspline basis functions. Adopting a recovery based error estimator in the proposed approach for evaluation of the model quality and performing the adaptive processes is in progress. Finally, some numerical examples with available analytical solutions are investigated by the developed scheme.
KW - Angewandte Informatik
KW - Angewandte Mathematik
KW - Computerunterstütztes Verfahren
Y1 - 2012
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-27637
UR - http://euklid.bauing.uni-weimar.de/ikm2012
SN - 1611-4086
ER -
TY - JOUR
A1 - Ghorashi, Seyed Shahram
A1 - Lahmer, Tom
A1 - Bagherzadeh, Amir Saboor
A1 - Zi, Goangseup
A1 - Rabczuk, Timon
T1 - A stochastic computational method based on goal-oriented error estimation for heterogeneous geological materials
JF - Engineering Geology
N2 - A stochastic computational method based on goal-oriented error estimation for heterogeneous geological materials
KW - Angewandte Mathematik
KW - Stochastik
KW - Strukturmechanik
Y1 - 2016
ER -
TY - JOUR
A1 - Jia, Yue
A1 - Anitescu, Cosmin
A1 - Ghorashi, Seyed Shahram
A1 - Rabczuk, Timon
A1 - Dias-da-Costa, D.
T1 - Extended Isogeometric Analysis for Material Interface Problems
JF - Journal of Applied Mathematics
N2 - Extended Isogeometric Analysis for Material Interface Problems
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
ER -
TY - JOUR
A1 - Ghorashi, Seyed Shahram
A1 - Valizadeh, Navid
A1 - Mohammadi, S.
A1 - Rabczuk, Timon
T1 - T-spline based XIGA for Fracture Analysis of Orthotropic Media
JF - Computers & Structures
N2 - T-spline based XIGA for Fracture Analysis of Orthotropic Media
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
SP - 138
EP - 146
ER -