TY  - JOUR
A1  - Zhen, Manghao
A1  - Liang, Yunpei
A1  - Staat, Manfred
A1  - Li, Quanqui
A1  - Li, Jianbo
T1  - Discontinuous fracture behaviors and constitutive model of sandstone specimens containing non-parallel prefabricated fissures under uniaxial compression
JF  - Theoretical and Applied Fracture Mechanics
N2  - The deformation and damage laws of non-homogeneous irregular structural planes in rocks are the basis for studying the stability of rock engineering. To investigate the damage characteristics of rock containing non-parallel fissures, uniaxial compression tests and numerical simulations were conducted on sandstone specimens containing three non-parallel fissures inclined at 0°, 45° and 90° in this study. The characteristics of crack initiation and crack evolution of fissures with different inclinations were analyzed. A constitutive model for the discontinuous fractures of fissured sandstone was proposed. The results show that the fracture behaviors of fissured sandstone specimens are discontinuous. The stress–strain curves are non-smooth and can be divided into nonlinear crack closure stage, linear elastic stage, plastic stage and brittle failure stage, of which the plastic stage contains discontinuous stress drops. During the uniaxial compression test, the middle or ends of 0° fissures were the first to crack compared to 45° and 90° fissures. The end with small distance between 0° and 45° fissures cracked first, and the end with large distance cracked later. After the final failure, 0° fissures in all specimens were fractured, while 45° and 90° fissures were not necessarily fractured. Numerical simulation results show that the concentration of compressive stress at the tips of 0°, 45° and 90° fissures, as well as the concentration of tensile stress on both sides, decreased with the increase of the inclination angle. A constitutive model for the discontinuous fractures of fissured sandstone specimens was derived by combining the logistic model and damage mechanic theory. This model can well describe the discontinuous drops of stress and agrees well with the whole processes of the stress–strain curves of the fissured sandstone specimens.
KW  - Constitutive model
KW  - Damage mechanics theory
KW  - Discontinuous fractures
KW  - Uniaxial compression test
KW  - Non-parallel fissures
Y1  - 2024
U6  - http://dx.doi.org/10.1016/j.tafmec.2024.104373
SN  - 0167-8442
VL  - 131
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Wegmann, Kilian
A1  - Hackl, Michael
A1  - Staat, Manfred
A1  - Mayer, Katharina
A1  - Müller, Lars-Peter
T1  - Double plate osteosynthesis of proximal ulna fractures: biomechanical and clinical results
JF  - Knee surgery, sports traumatology, arthroscopy
N2  - While plate fixation of proximal ulna fractures might lead to superior clinical results compared to tension band wiring, regular plates represent an established risk factor for wound complications. The olecranon double plates (Medartis, Basel, CH) might decrease complications related to the osteosynthesis because of their low profile and better anatomical fit. This study aimed to evaluate the biomechanical performance and clinical results of the olecranon double plates.
Y1  - 2016
U6  - http://dx.doi.org/10.1007/s00167-016-4079-0
SN  - 0942-2056
VL  - Volume 24
IS  - Supplement 1
SP  - 58
EP  - 59
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Vu, Duc-Khoi
A1  - Staat, Manfred
T1  - An algorithm for shakedown analysis of structure with temperature dependent yield stress
N2  - This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature-dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithmfor shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools.
KW  - Einspielen <Werkstoff>
KW  - Temperaturabhängigkeit
KW  - Fließgrenze
KW  - Shakedown
KW  - shakedown analysis
KW  - yield stress
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Vu, Duc Khoi
A1  - Staat, Manfred
A1  - Tran, Ich Thinh
T1  - Analysis of pressure equipment by application of the primal-dual theory of shakedown
JF  - Communications in Numerical Methods in Engineering. 23 (2007), H. 3
Y1  - 2007
SN  - 1069-8299
SP  - 213
EP  - 225
ER  - 
TY  - JOUR
A1  - Vu, Duc Khoi
A1  - Staat, Manfred
T1  - Shakedown analysis of structures made of materials with temperature-dependent yield stress
JF  - International Journal of Solids and Structures. 44 (2007), H. 13
Y1  - 2007
SN  - 0020-7683
SP  - 4524
EP  - 4540
ER  - 
TY  - JOUR
A1  - Vant, Christianne
A1  - Staat, Manfred
A1  - Baroud, Gamal
T1  - Percutaneous Vertebroplasty: A Review of Two Intraoperative Complications
JF  - Bioengineering in Cell and Tissue Research / Artmann, Gerhard M. ; Chien, Shu (Eds.)
Y1  - 2008
SN  - 978-3-540-75408-4
SP  - 527
EP  - 539
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Ullrich, Sebastian
A1  - Grottke, Oliver
A1  - Rossaint, Rolf
A1  - Staat, Manfred
A1  - Deserno, Thomas M.
A1  - Kuhlen, Torsten
T1  - Virtual Needle Simulation with Haptics for Regional Anaesthesia
Y1  - 2010
N1  - IEEE Virtual Reality 2010, Workshop on Medical Virtual Environments, Waltham, MA, USA, March 21, 2010
SP  - 1
EP  - 3
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
A1  - Kreißig, R.
T1  - Calculation of load carrying capacity of shell structures with elasto-plastic material by direct methods
N2  - Proceedings of the International Conference on Material Theory and Nonlinear Dynamics. MatDyn. Hanoi, Vietnam, Sept. 24-26, 2007, 8 p. In this paper, a method is introduced to determine the limit load of general shells using the finite element method. The method is based on an upper bound limit and shakedown analysis with elastic-perfectly plastic material model. A non-linear constrained optimisation problem is solved by using Newton’s method in conjunction with a penalty method and the Lagrangean dual method. Numerical investigation of a pipe bend subjected to bending moments proves the effectiveness of the algorithm.
KW  - Finite-Elemente-Methode
Y1  - 2007
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
A1  - Kreißig, R.
T1  - Finite element shakedown and limit reliability analysis of thin shells
N2  - A procedure for the evaluation of the failure probability of elastic-plastic thin shell structures is presented. The procedure involves a deterministic limit and shakedown analysis for each probabilistic iteration which is based on the kinematical approach and the use the exact Ilyushin yield surface. Based on a direct definition of the limit state function, the non-linear problems may be efficiently solved by using the First and Second Order Reliabiblity Methods (Form/SORM). This direct approach reduces considerably the necessary knowledge of uncertain technological input data, computing costs and the numerical error. In: Computational plasticity / ed. by Eugenio Onate. Dordrecht: Springer 2007. VII, 265 S. (Computational Methods in Applied Sciences ; 7) (COMPLAS IX. Part 1 . International Center for Numerical Methods in Engineering (CIMNE)). ISBN 978-1-402-06576-7  S. 186-189
KW  - Finite-Elemente-Methode
KW  - Limit analysis
KW  - shakedown analysis
KW  - Exact Ilyushin yield surface
KW  - Random variable
KW  - First Order Reliabiblity Method
Y1  - 2007
ER  - 
TY  - JOUR
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
T1  - Shakedown analysis of two dimensional structures by an edge-based smoothed finite element method
Y1  - 2010
N1  - ECCM 2010, IV European Conference on Computational Mechanics, Paris, France, May 16-21, 2010.
SP  - 1
EP  - 7
ER  - 
TY  - JOUR
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
T1  - An Edge-Based Smoothed Finite Element Method for Primal-Dual Shakedown Analysis of Structures Under Uncertainties
JF  - Limit State of Materials and Structures : Direct Methods 2. Saxcé, Géry de (Hrsg.)
Y1  - 2013
SN  - 978-94-007-5424-9
SP  - 89
EP  - 102
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
ED  - Eberhardsteiner, J.
T1  - A primal-dual shakedown analysis of 3D structures using the face-based smoothed finite element method
T2  - Proceedings European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012)
Y1  - 2012
N1  - 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) Vienna, Austria, September 10-14, 2012
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
T1  - Shakedown analysis of Reissner-Mindlin plates using the edge-based smoothed finite element method
T2  - Direct methods for limit states in structures and materials / Dieter Weichert ; Alan Ponter, ed.
N2  - This paper concerns the development of a primal-dual algorithm for limit and shakedown analysis of Reissner-Mindlin plates made of von Mises material. At each optimization iteration, the lower bound of the shakedown load multiplier is calculated simultaneously with the upper bound using the duality theory. An edge-based smoothed finite element method (ES-FEM) combined with the discrete shear gap (DSG) technique is used to improve the accuracy of the solutions and to avoid the transverse shear locking behaviour. The method not only possesses all inherent features of convergence and accuracy from ES-FEM, but also ensures that the total number of variables in the optimization problem is kept to a minimum compared with the standard finite element formulation. Numerical examples are presented to demonstrate the effectiveness of the present method.
Y1  - 2014
SN  - 978-94-007-6826-0 (Print) 978-94-007-6827-7 (Online)
U6  - http://dx.doi.org/10.1007/978-94-007-6827-7_5
SP  - 101
EP  - 117
PB  - Springer
CY  - Dordrecht [u.a.]
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
ED  - Onate, E.
T1  - Uncertain multimode failure and limit analysis of shells
T2  - 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
Y1  - 2014
SP  - 1
EP  - 12
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Staat, Manfred
T1  - Uncertainty multimode failure and shakedown analysis of shells
T2  - Direct methods for limit and shakedown analysis of structures / eds. Paolo Fuschi ...
N2  - This paper presents a numerical procedure for reliability analysis of thin plates and shells with respect to plastic collapse or to inadaptation. The procedure involves a deterministic shakedown analysis for each probabilistic iteration, which is based on the upper bound approach and the use of the exact Ilyushin yield surface. Probabilistic shakedown analysis deals with uncertainties originated from the loads, material strength and thickness of the shell. Based on a direct definition of the limit state function, the calculation of the failure probability may be efficiently solved by using the First and Second Order Reliability Methods (FORM and SORM). The problem of reliability of structural systems (series systems) is handled by the application of a special technique which permits to find all the design points corresponding to all the failure modes. Studies show, in this case, that it improves considerably the FORM and SORM results.
KW  - Limit analysis
KW  - Shakedown analysis
KW  - Reliability analysis
KW  - Multimode failure
KW  - Non-linear optimization
Y1  - 2015
SN  - 978-3-319-12927-3 (print) ; 978-3-319-12928-0 (online)
U6  - http://dx.doi.org/10.1007/978-3-319-12928-0_14
SP  - 279
EP  - 298
PB  - Springer
CY  - Cham
ER  - 
TY  - JOUR
A1  - Tran, Thanh Ngoc
A1  - Pham, Phu Tinh
A1  - Vu, D. K.
A1  - Staat, Manfred
T1  - Reliability Analysis of Inelastic Shell Structures Under Variable Loads
JF  - Limit States of Materials and Structures : Direct Methods / Hrsg. Dieter Weichert; Hrsg. Alan Ponter
Y1  - 2009
SN  - 978-1-4020-9633-4
SP  - 135
EP  - 156
PB  - Springer Netherland
CY  - Berlin
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Pham, Phu Tinh
A1  - Staat, Manfred
T1  - Reliability analysis of shells based on direct plasticity methods
N2  - Abstracts der CD-Rom Proceedings of the 8th World Congress on Computational Mechanics (WCCM8) and 5th Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008) 30.06. - 04.07.2008 Venedig, Italien. 2 Seiten Zusammenfassung der Autoren mit graph. Darst. und Literaturverzeichnis
N2  - Abstracts of the Proceedings of the 8th World Congress on Computational Mechanics (WCCM8) and 5th Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008) June 30th - July, 4th 2008, Venice, Italy. 2 pages with abstracts of the authors, Ill. and references.
KW  - Finite-Elemente-Methode
KW  - Limit analysis
KW  - Shakedown analysis
KW  - First-order reliability method
KW  - second-order reliability method
KW  - Sensitivity
Y1  - 2008
ER  - 
TY  - CHAP
A1  - Tran, Thanh Ngoc
A1  - Novacek, V.
A1  - Tolba, R.
A1  - Klinge, U.
A1  - Turquier, F.
A1  - Staat, Manfred
T1  - Experimental and Computational approach to study colorectal anastomosis. ISB2011, Proceedings of the XXIII Congress of the International Society of Biomechanics, Brussels, Belgium, July 3-7, 2011
N2  - Summary: This paper presents a methodology to study and understand the mechanics of stapled anastomotic behaviors by combining empirical experimentation and finite element analysis. Performance of stapled anastomosis is studied in terms of leakage and numerical results which are compared to in vitro experiments performed on fresh porcine tissue. Results suggest that leaks occur between the tissue and staple legs penetrating through the tissue.
KW  - Anastomose
KW  - Finite-Elemente-Methode
KW  - Biomechanik
KW  - Anastomosis
KW  - Finite element method
KW  - Biomechanics
Y1  - 2011
ER  - 
TY  - JOUR
A1  - Tran, Thanh Ngoc
A1  - Kreißig, R.
A1  - Vu, Duc Khoi
A1  - Staat, Manfred
T1  - Upper bound limit and shakedown analysis of shells using the exact Ilyushin yield surface
JF  - Computer & Structures. 86 (2008)
Y1  - 2008
SN  - 0045-7949
SP  - 1683
EP  - 1695
ER  - 
TY  - JOUR
A1  - Tran, Thanh Ngoc
A1  - Kreißig, R.
A1  - Staat, Manfred
T1  - Probabilistic limit and shakedown analysis of thin plates and shells
JF  - Structural safety. 31 (2009), H. 1
Y1  - 2009
SN  - 0167-4730
SP  - 1
EP  - 18
PB  - -
ER  - 
TY  - CHAP
A1  - Tran, Ngoc Trinh
A1  - Trinh, Tu Luc
A1  - Dao, Ngoc Tien
A1  - Giap, Van Tan
A1  - Truong, Manh Khuyen
A1  - Dinh, Thuy Ha
A1  - Staat, Manfred
T1  - Limit and shakedown analysis of structures under random strength
T2  - Proceedings of (NACOME2022) The 11th National Conference on Mechanics, Vol. 1. Solid Mechanics, Rock Mechanics, Artificial Intelligence, Teaching and Training, Hanoi, December 2-3, 2022
N2  - Direct methods comprising limit and shakedown analysis is a branch of computational mechanics. It plays a significant role in mechanical and civil engineering design. The concept of direct method aims to determinate the ultimate load bearing capacity of structures beyond the elastic range. For practical problems, the direct methods lead to nonlinear convex optimization problems with a large number of variables and onstraints. If strength and loading are random quantities, the problem of shakedown analysis is considered as stochastic programming. This paper presents a method so called chance constrained programming, an effective method of stochastic programming, to solve shakedown analysis problem under random condition of strength. In this our investigation, the loading is deterministic, the strength is distributed as normal or lognormal variables.
KW  - Reliability of structures
KW  - Stochastic programming
KW  - Chance constrained programming
KW  - Shakedown analysis
KW  - Limit analysis
Y1  - 2022
SN  - 978-604-357-084-7
SP  - 510
EP  - 518
PB  - Nha xuat ban Khoa hoc tu nhien va Cong nghe (Verlag Naturwissenschaft und Technik)
CY  - Hanoi
ER  - 
TY  - JOUR
A1  - Tran, Ngoc Trinh
A1  - Trinh, Tu Luc
A1  - Dao, Ngoc Tien
A1  - Giap, Van Tan
A1  - Truong, Manh Khuyen
A1  - Dinh, Thuy Ha
A1  - Staat, Manfred
T1  - FEM shakedown analysis of structures under random strength with chance constrained programming
JF  - Vietnam Journal of Mechanics
N2  - Direct methods, comprising limit and shakedown analysis, are a branch of computational mechanics. They play a significant role in mechanical and civil engineering design. The concept of direct methods aims to determine the ultimate load carrying capacity of structures beyond the elastic range. In practical problems, the direct methods lead to nonlinear convex optimization problems with a large number of variables and constraints. If strength and loading are random quantities, the shakedown analysis can be formulated as stochastic programming problem. In this paper, a method called chance constrained programming is presented, which is an effective method of stochastic programming to solve shakedown analysis problems under random conditions of strength. In this study, the loading is deterministic, and the strength is a normally or lognormally distributed variable.
KW  - limit analysis
KW  - shakedown analysis
KW  - chance constrained programming
KW  - stochastic programming
KW  - reliability of structures
Y1  - 2022
U6  - http://dx.doi.org/10.15625/0866-7136/17943
SN  - 0866-7136
SN  - 2815-5882
VL  - 44
IS  - 4
SP  - 459
EP  - 473
PB  - Vietnam Academy of Science and Technology (VAST)
ER  - 
TY  - CHAP
A1  - Tran, Ngoc Trinh
A1  - Tran, Thanh Ngoc
A1  - Matthies, Hermann G.
A1  - Stavroulakis, Georgios Eleftherios
A1  - Staat, Manfred
T1  - FEM Shakedown of uncertain structures by chance constrained programming
T2  - PAMM Proceedings in Applied Mathematics and Mechanics
Y1  - 2016
U6  - http://dx.doi.org/10.1002/pamm.201610346
SN  - 1617-7061
N1  - Special Issue:
Joint 87th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM) and Deutsche Mathematiker-Vereinigung
VL  - 16
IS  - 1
SP  - 715
EP  - 716
ER  - 
TY  - CHAP
A1  - Tran, Ngoc Trinh
A1  - Tran, Thanh Ngoc
A1  - Matthies, H. G.
A1  - Stavroulakis, G. E.
A1  - Staat, Manfred
ED  - Papadrakakis, M.
T1  - Shakedown analysis of plate bending analysis under stochastic uncertainty by chance constrained programming
T2  - ECCOMAS Congress 2016, VII European Congress on Computational Methods in Applied Sciences and Engineering. Crete Island, Greece, 5–10 June 2016
Y1  - 2016
ER  - 
TY  - CHAP
A1  - Tran, Ngoc Trinh
A1  - Staat, Manfred
A1  - Stavroulakis, G. E.
ED  - Onate, E.
T1  - A multicriteria method for truss optimization
T2  - 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
Y1  - 2014
SP  - 1
EP  - 12
ER  - 
TY  - JOUR
A1  - Tran, Ngoc Trinh
A1  - Staat, Manfred
T1  - Direct plastic structural design under lognormally distributed strength by chance constrained programming
JF  - Optimization and Engineering
N2  - We propose the so-called chance constrained programming model of stochastic programming theory to analyze limit and shakedown loads of structures under random strength with a lognormal distribution. A dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit. The edge-based smoothed finite element method (ES-FEM) is used with three-node linear triangular elements.
Y1  - 2020
U6  - http://dx.doi.org/10.1007/s11081-019-09437-2
SN  - 1573-2924
VL  - 21
IS  - 1
SP  - 131
EP  - 157
PB  - Springer Nature
CY  - Cham
ER  - 
TY  - JOUR
A1  - Tran, Ngoc Trinh
A1  - Staat, Manfred
T1  - Direct plastic structural design under random strength and random load by chance constrained programming
JF  - European Journal of Mechanics - A/Solids
Y1  - 2021
U6  - http://dx.doi.org/10.1016/j.euromechsol.2020.104106
SN  - 0997-7538
VL  - 85
IS  - Article 104106
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - CHAP
A1  - Tran, Ngoc Trinh
A1  - Staat, Manfred
T1  - FEM shakedown analysis of Kirchhoff-Love plates under uncertainty of strength
T2  - Proceedings of UNCECOMP 2021
N2  - A new formulation to calculate the shakedown limit load of Kirchhoff plates under stochastic conditions of strength is developed. Direct structural reliability design by chance con-strained programming is based on the prescribed failure probabilities, which is an effective approach of stochastic programming if it can be formulated as an equivalent deterministic optimization problem. We restrict uncertainty to strength, the loading is still deterministic. A new formulation is derived in case of random strength with lognormal distribution. Upper bound and lower bound shakedown load factors are calculated simultaneously by a dual algorithm.
Y1  - 2021
SN  - 978-618-85072-6-5
U6  - http://dx.doi.org/10.7712/120221.8041.19047
N1  - Proceedings of UNCECOMP 2021, 4th International Conference on Uncertainty Quantification in Computational Sciences and Engineering, streamed from Athens, Greece, 28–30 June 2021.
SP  - 323
EP  - 338
ER  - 
TY  - CHAP
A1  - Tran, Ngoc Trinh
A1  - Matthies, Hermann G.
A1  - Stavroulakis, Georgios Eleftherios
A1  - Staat, Manfred
T1  - Direct plastic structural design by chance constrained programming
T2  - 6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7), 11-15 June 2018, Glasgow, UK
N2  - We propose a stochastic programming method to analyse limit and shakedown of structures under random strength with lognormal distribution. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit or the shakedown limit. The edge-based smoothed finite element method (ES-FEM) using three-node linear triangular elements is used.
Y1  - 2018
ER  - 
TY  - CHAP
A1  - Tran, N. T.
A1  - Tran, Thanh Ngoc
A1  - Matthies, M. G.
A1  - Stavroulakis, G. E.
A1  - Staat, Manfred
T1  - Shakedown Analysis Under Stochastic Uncertainty by Chance Constrained Programming
T2  - Advances in Direct Methods for Materials and Structures
N2  - In this paper we propose a stochastic programming method to analyse limit and shakedown of structures under uncertainty condition of strength. Based on the duality theory, the shakedown load multiplier formulated by the kinematic theorem is proved actually to be the dual form of the shakedown load multiplier formulated by static theorem. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit. The edge-based smoothed finite element method (ES-FEM) with three-node linear triangular elements is used for structural analysis.
Y1  - 2017
SN  - 978-3-319-59810-9
U6  - http://dx.doi.org/10.1007/978-3-319-59810-9_6
SP  - 85
EP  - 103
PB  - Springer
CY  - Cham
ER  - 
TY  - JOUR
A1  - Topçu, Murat
A1  - Madabhushi, Gopal S.P.
A1  - Staat, Manfred
T1  - A generalized shear-lag theory for elastic stress transfer between matrix and fibres having a variable radius
JF  - International Journal of Solids and Structures
N2  - A generalized shear-lag theory for fibres with variable radius is developed to analyse elastic fibre/matrix stress transfer. The theory accounts for the reinforcement of biological composites, such as soft tissue and bone tissue, as well as for the reinforcement of technical composite materials, such as fibre-reinforced polymers (FRP). The original shear-lag theory proposed by Cox in 1952 is generalized for fibres with variable radius and with symmetric and asymmetric ends. Analytical solutions are derived for the distribution of axial and interfacial shear stress in cylindrical and elliptical fibres, as well as conical and paraboloidal fibres with asymmetric ends. Additionally, the distribution of axial and interfacial shear stress for conical and paraboloidal fibres with symmetric ends are numerically predicted. The results are compared with solutions from axisymmetric finite element models. A parameter study is performed, to investigate the suitability of alternative fibre geometries for use in FRP.
KW  - Natural fibres
KW  - Polymer-matrix composites
KW  - Biocomposites
KW  - Stress concentrations
KW  - Finite element analysis
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.ijsolstr.2022.111464
SN  - 0020-7683
VL  - 239–240
IS  - Art. No. 111464
PB  - Elsevier
CY  - New York, NY
ER  - 
TY  - GEN
A1  - Topcu, Murat
A1  - Madabhushi, Gopal Santana Phani
A1  - Staat, Manfred
T1  - Datasets from FEM Simulations done with COMSOL Multiphysics and Code_Aster
N2  - Datasets from FEM Simulations done with COMSOL Multiphysics and Code_Aster for an elastic stress transfer between matrix and fibres having a variable radius.
KW  - Natural fibres
KW  - Polymer-matrix composites
KW  - Biocomposites
KW  - Stress concentrations
KW  - Finite element analysis (FEA)
Y1  - 2022
U6  - http://dx.doi.org/10.6084/m9.figshare.19333295.v2
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Vu, Khoi Duc
T1  - Limit loads of circumferentially flawed pipes and cylindrical vessels under internal pressure
JF  - International Journal of Pressure Vessels and Piping. 83 (2006), H. 3
Y1  - 2006
SN  - 0308-0161
SP  - 188
EP  - 196
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Vu, Duc-Khoi
T1  - An Algorithm for Shakedown Analysis for Materials with Temperature Dependent Yield Stress
JF  - Proceedings in Applied Mathematics and Mechanics (PAMM). 4 (2004), H. 1
Y1  - 2004
SN  - 1617-7061
SP  - 231
EP  - 233
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Vu, Duc-Khoi
T1  - Limit analysis of flaws in pressurized pipes and cylindrical vessels. Part I: Axial defects
JF  - Engineering Fracture Mechanics. 74 (2007), H. 3
Y1  - 2007
SN  - 0013-7944
SP  - 431
EP  - 450
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Vu, Duc Khoi
T1  - Limit analysis of flaws in pressurized pipes and cylindrical vessels Part II: Circumferential defects
JF  - Engineering Fracture Mechanics ; 97(2013), H. 1
N2  - Upper and lower bound theorems of limit analyses have been presented in part I of the paper. Part II starts with the finite element discretization of these theorems and demonstrates how both can be combined in a primal–dual optimization problem. This recently proposed numerical method is used to guide the development of a new class of closed-form limit loads for circumferential defects, which show that only large defects contribute to plastic collapse with a rapid loss of strength with increasing crack sizes. The formulae are compared with primal–dual FEM limit analyses and with burst tests. Even closer predictions are obtained with iterative limit load solutions for the von Mises yield function and for the Tresca yield function. Pressure loading of the faces of interior cracks in thick pipes reduces the collapse load of circumferential defects more than for axial flaws. Axial defects have been treated in part I of the paper.
Y1  - 2012
U6  - http://dx.doi.org/10.1016/j.engfracmech.2012.05.017
SN  - 0013-7944
VL  - 97
SP  - 314
EP  - 333
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Trenz, Eva
A1  - Lohmann, Philipp
A1  - Frotscher, Ralf
A1  - Klinge, Uwe
A1  - Tabaza, Ruth
A1  - Kirschner-Hermanns, Ruth
T1  - New measurements to compare soft tissue anchoring systems in pelvic floor surgery
JF  - Journal of Biomedical Materials Research Part B: Applied Biomaterials
N2  - Suburethral slings as well as different meshes are widely used treating stress urinary incontinence and prolaps in women. With the development of MiniSlings and special meshes using less alloplastic material anchorage systems become more important to keep devices in place and to put some tension especially on the MiniSlings. To date, there are many different systems of MiniSlings of different companies on the market which differ in the structure of the used meshes and anchors. A new objective measurement method to compare different properties of MiniSling systems (mesh and anchor) is presented in this article. Ballistic gelatine acts as soft tissue surrogate. Significant differences in parameters like pull-out strength of anchors or shrinkage of meshes under loading conditions have been determined. The form and size of the anchors as well as the structural stability of the meshes are decisive for a proper integration. The tested anchorings sytems showed markedly different mechanical function at their respective load bearing capacity. As the stable fixation of the device in tissue is a prerequisite for a permanet reinforcement, the proposed test system permits further optimisation of anchor and mesh devices to improve the success of the surgical treatment
Y1  - 2012
U6  - http://dx.doi.org/10.1002/jbm.b.32654
SN  - 1552-4981
VL  - 100B
IS  - 4
SP  - 924
EP  - 933
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - CHAP
A1  - Staat, Manfred
A1  - Tran, Thanh Ngoc
A1  - Pham, Phu Tinh
T1  - Limit and shakedown reliability analysis by nonlinear programming
N2  - 7th International Conference on Reliability of Materials and Structures (RELMAS 2008). June 17 - 20, 2008 ; Saint Petersburg, Russia. pp 354-358. Reprint with corrections in red Introduction Analysis of advanced structures working under extreme heavy loading such as nuclear power plants and piping system should take into account the randomness of loading, geometrical and material parameters. The existing reliability are restricted mostly to the elastic working regime, e.g. allowable local stresses. Development of the limit and shakedown reliability-based analysis and design methods, exploiting potential of the shakedown working regime, is highly needed. In this paper the application of a new algorithm of probabilistic limit and shakedown analysis for shell structures is presented, in which the loading and strength of the material as well as the thickness of the shell are considered as random variables. The reliability analysis problems may be efficiently solved by using a system combining the available FE codes, a deterministic limit and shakedown analysis, and the First and Second Order Reliability Methods (FORM/SORM). Non-linear sensitivity analyses are obtained directly from the solution of the deterministic problem without extra computational costs.
KW  - Finite-Elemente-Methode
KW  - Limit analysis
KW  - Shakedown analysis
Y1  - 2008
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Tran, Thanh Ngoc
A1  - Kreißig, R.
T1  - Load bearing capacity of thin shell structures made of elastoplastic material by direct methods
JF  - Technische Mechanik. 28 (2008), H. 3-4
Y1  - 2008
SP  - 299
EP  - 309
ER  - 
TY  - CHAP
A1  - Staat, Manfred
A1  - Tran, Ngoc Trinh
T1  - Strain based brittle failure criteria for rocks
T2  - Proceedings of (NACOME2022) The 11th National Conference on Mechanics, Vol. 1. Solid Mechanics, Rock Mechanics, Artificial Intelligence, Teaching and Training, Hanoi, December 2-3, 2022
N2  - When confining pressure is low or absent, extensional fractures are typical, with fractures occurring on unloaded planes in rock. These “paradox” fractures 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. But this criterion makes unrealistic strength predictions in biaxial compression and tension. A new extension strain criterion overcomes this limitation by adding a weighted principal shear component. The 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 failure modes, which are unexpected in the 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. 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 P. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.
KW  - Extension fracture
KW  - Extension strain criterion
KW  - Mohr–Coulomb criterion
KW  - Evolution of damage
Y1  - 2023
SN  - 978-604-357-084-7
SP  - 500
EP  - 509
PB  - Nha xuat ban Khoa hoc tu nhien va Cong nghe (Verlag Naturwissenschaft und Technik)
CY  - Hanoi
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Sponagel, Stefan
A1  - Nguyen, Nhu Huynh
T1  - Experiment and material model for soft tissue materials
JF  - Constitutive  models for rubber VI : proceedings of the sixth European Conference on Constitutive Models for Rubber, Dresden, Germany, 7 - 10 September 2009 / eds. Gert Heinrich ...
Y1  - 2010
SN  - 978-0-415-56327-7
SP  - 465
EP  - 470
PB  - CRC Press
CY  - Boca Raton [u.a.]
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Schwartz, M.
A1  - Lang, H.
A1  - Wirtz, K.
A1  - Heitzer, M.
T1  - Design by Analysis of Pressure Components by non-linear Optimization
JF  - The 10th International Conference on Pressure Vessel Technology, July 7-10, 2003, Vienna, Austria, Proceedings ICPVT-10 / Zeman, J. L. [ed]
Y1  - 2003
SN  - 3950152814
SP  - 59
EP  - 65
PB  - ÖGS, Österreichische Gesellschaft für Schweißtechnik
CY  - Wien
ER  - 
TY  - CHAP
A1  - Staat, Manfred
A1  - Heitzer, Michael
T1  - Limit and shakedown analysis for plastic design
N2  - Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of safety factors or of the load carrying capacity under constant and varying loads. Simple versions of limit and shakedown analysis are the basis of all design codes for pressure vessels and pipings. Using Finite Element Methods more realistic modeling can be used for a more rational design. The methods can be extended to yield optimum plastic design. In this paper we present a first implementation in FE of limit and shakedown analyses for perfectly plastic material. Limit and shakedown analyses are done of a pipe–junction and a interaction diagram is calculated. The results are in good correspondence with the analytic solution we give in the appendix.
KW  - Einspielen <Werkstoff>
KW  - Traglast
KW  - Finite-Elemente-Methode
KW  - Traglastanalyse
KW  - Einspielanalyse
KW  - FEM
KW  - limit analysis
KW  - shakedown analysis
Y1  - 1997
ER  - 
TY  - CHAP
A1  - Staat, Manfred
A1  - Heitzer, Michael
T1  - The restricted influence of kinematic hardening on shakedown loads
N2  - Structural design analyses are conducted with the aim of verifying the exclusion of ratcheting. To this end it is important to make a clear distinction between the shakedown range and the ratcheting range. In cyclic plasticity more sophisticated hardening models have been suggested in order to model the strain evolution observed in ratcheting experiments. The hardening models used in shakedown analysis are comparatively simple. It is shown that shakedown analysis can make quite stable predictions of admissible load ranges despite the simplicity of the underlying hardening models. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis. Both give identical or similar shakedown ranges. Structural shakedown analyses show that the loading may have a more pronounced effect than the hardening model.
KW  - Biomedizinische Technik
KW  - Einspielen <Werkstoff>
KW  - Shakedown
KW  - Ratcheting
KW  - Bruchmechanik
KW  - shakedown
KW  - material shakedown
KW  - linear kinematic hardening
KW  - nonlinear kinematic hardening
KW  - ratchetting
Y1  - 2002
ER  - 
TY  - CHAP
A1  - Staat, Manfred
A1  - Heitzer, Michael
T1  - Direct static FEM approach to limit and shakedown analysis
N2  - Safety and reliability of structures may be assessed indirectly by stress distributions. Limit and shakedown theorems are simplified but exact methods of plasticity that provide safety factors directly in the loading space. These theorems may be used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. In a FEM formulation the limit state function is obtained from a nonlinear optimization problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error. Moreover, the direct way leads to highly effective and precise reliability analyses. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis.
KW  - Einspielen <Werkstoff>
KW  - Nichtlineare Optimierung
KW  - Shakedown
KW  - Shakedown
KW  - limit load
KW  - lower bound theorem
KW  - nonlinear optimization
KW  - reliability
Y1  - 2000
ER  - 
TY  - CHAP
A1  - Staat, Manfred
A1  - Heitzer, Michael
ED  - Staat, Manfred
ED  - Heitzer, Michael
T1  - Probabilistic limit and shakedown problems
T2  - Numerical methods for limit and shakedown analysis. Deterministic and probabilistic problems
Y1  - 2003
SN  - 3-00-010001-6
N1  - NIC Series
VL  - 15
SP  - 217
EP  - 268
PB  - John von Neumann Institute for Computing (NIC)
CY  - Jülich
ER  - 
TY  - BOOK
A1  - Staat, Manfred
A1  - Heitzer, Michael
T1  - Numerical methods for limit and shakedown analysis. Deterministic and probabilistic problems.
Y1  - 2003
SN  - 3-00-010001-6
N1  - NIC Series Vol. 15 / Ed. by Staat, M; Heitzer, M.
PB  - John von Neumann Institute for Computing (NIC)
CY  - Jülich
ER  - 
TY  - BOOK
A1  - Staat, Manfred
A1  - Heitzer, M.
A1  - Yan, Ai-Min
A1  - Khoi, Vu Duc
A1  - Nguyen, Dang Hung
A1  - Valdoire, F.
A1  - Lahousse, A.
T1  - Limit Analysis of Defects
Y1  - 2000
SN  - 0944-2952
N1  - Bericht des Forschungszentrums, Jül-3746, Jülich (2000)
PB  - Forschungszentrum Jülich
CY  - Jülich
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Heitzer, M.
A1  - Reiners, H.
A1  - Schubert, F.
T1  - Shakedown and ratchetting under tension–torsion loadings: analysis and experiments
JF  - Nuclear Engineering and Design. 225 (2003), H. 1
Y1  - 2003
SN  - 0029-5493
SP  - 11
EP  - 26
ER  - 
TY  - JOUR
A1  - Staat, Manfred
A1  - Heitzer, M.
A1  - Lang, H.
A1  - Wirtz, K.
T1  - Direct Finite Element Route for Design-by-Analysis of Pressure Components
JF  - International Journal of Pressure Vessels and Piping. 82 (2005), H. 1
Y1  - 2005
SN  - 0308-0161
SP  - 61
EP  - 67
ER  -