Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Bemerkung Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Zugriffsart Link Abteilungen OPUS4-9947 Wissenschaftlicher Artikel Bhattarai, Aroj, ; Horbach, Andreas, horbach@fh-aachen.de; Staat, Manfred, m.staat@fh-aachen.de; Kowalczyk, Wojciech, ; Tran, Thanh Ngoc, tran@fh-aachen.de Virgin passive colon biomechanics and a literature review of active contraction constitutive models The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel-Gasser-Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill's three-element model, Murphy's four-state cross-bridge chemical kinetic model and Huxley's sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine. Basel MDPI 2022 19 Biomechanics 2 2 138 157 10.3390/biomechanics2020013 weltweit https://doi.org/10.3390/biomechanics2020013 Fachbereich Medizintechnik und Technomathematik OPUS4-10231 Wissenschaftlicher Artikel Bhattarai, Aroj, ; May, Charlotte Anabell, ; Staat, Manfred, m.staat@fh-aachen.de; Kowalczyk, Wojciech, ; Tran, Thanh Ngoc, Layer-specific damage modeling of porcine large intestine under biaxial tension The mechanical behavior of the large intestine beyond the ultimate stress has never been investigated. Stretching beyond the ultimate stress may drastically impair the tissue microstructure, which consequently weakens its healthy state functions of absorption, temporary storage, and transportation for defecation. Due to closely similar microstructure and function with humans, biaxial tensile experiments on the porcine large intestine have been performed in this study. In this paper, we report hyperelastic characterization of the large intestine based on experiments in 102 specimens. We also report the theoretical analysis of the experimental results, including an exponential damage evolution function. The fracture energies and the threshold stresses are set as damage material parameters for the longitudinal muscular, the circumferential muscular and the submucosal collagenous layers. A biaxial tensile simulation of a linear brick element has been performed to validate the applicability of the estimated material parameters. The model successfully simulates the biomechanical response of the large intestine under physiological and non-physiological loads. Basel MDPI 2022 16 Bioengineering 9 Der Artikel gehört zum Sonderheft "Computational Biomechanics" 10, Early Access 1 17 10.3390/bioengineering9100528 weltweit https://doi.org/10.3390/bioengineering9100528 Fachbereich Medizintechnik und Technomathematik OPUS4-7297 Wissenschaftlicher Artikel Duong, Minh Tuan, duong@fh-aachen.de; Nguyen, Nhu Huynh, ; Tran, Thanh Ngoc, tran@fh-aachen.de; Tolba, R. H., ; Staat, Manfred, m.staat@fh-aachen.de Influence of refrigerated storage on tensile mechanical properties of porcine liver and spleen London Taylor & Francis 2015 9 International biomechanics Vol. 2 Iss. 1 79 88 10.1080/23335432.2015.1049295 campus http://doi.org/10.1080/23335432.2015.1049295 Fachbereich Medizintechnik und Technomathematik OPUS4-4812 Wissenschaftlicher Artikel Nguyen, Nhu Huynh, ; Duong, Minh Tuan, duong@fh-aachen.de; Tran, Thanh Ngoc, tran@fh-aachen.de; Pham, Phu Tinh, ; Grottke, O., ; Tolba, R., ; Staat, Manfred, m.staat@fh-aachen.de Influence of a freeze-thaw cycle on the stress-stretch curves of tissues of porcine abdominal organs The paper investigates both fresh porcine spleen and liver and the possible decomposition of these organs under a freeze-thaw cycle. The effect of tissue preservation condition is an important factor which should be taken into account for protracted biomechanical tests. In this work, tension tests were conducted for a large number of tissue specimens from twenty pigs divided into two groups of 10. Concretely, the first group was tested in fresh state; the other one was tested after a freeze-thaw cycle which simulates the conservation conditions before biomechanical experiments. A modified Fung model for isotropic behavior was adopted for the curve fitting of each kind of tissues. Experimental results show strong effects of the realistic freeze-thaw cycle on the capsule of elastin-rich spleen but negligible effects on the liver which virtually contains no elastin. This different behavior could be explained by the autolysis of elastin by elastolytic enzymes during the warmer period after thawing. Realistic biomechanical properties of elastin-rich organs can only be expected if really fresh tissue is tested. The observations are supported by tests of intestines. Amsterdam Elsevier 2012 4 Journal of Biomechanics 45 14 2382 2386 10.1016/j.jbiomech.2012.07.008 campus https://doi.org/10.1016/j.jbiomech.2012.07.008 Fachbereich Medizintechnik und Technomathematik OPUS4-9533 Wissenschaftlicher Artikel Nguyen-Xuan, H., ; Rabczuk, T., ; Nguyen-Thoi, T., ; Tran, Thanh Ngoc, tran@fh-aachen.de; Nguyen-Thanh, N., Computation of limit and shakedown loads using a node-based smoothed finite element method Weinheim Wiley 2011 23 International Journal for Numerical Methods in Engineering 90 3 287 310 10.1002/nme.3317 campus https://doi.org/10.1002/nme.3317 Fachbereich Medizintechnik und Technomathematik OPUS4-4811 Wissenschaftlicher Artikel Novacek, V., ; Tran, Thanh Ngoc, tran@fh-aachen.de; Klinge, U., ; Tolba, R. H., ; Staat, Manfred, m.staat@fh-aachen.de; Bronson, D. G., ; Miesse, A. M., ; Whiffen, J., ; Turquier, F., Finite element modelling of stapled colorectal end-to-end anastomosis : Advantages of variable height stapler design The impact of surgical staplers on tissues has been studied mostly in an empirical manner. In this paper, finite element method was used to clarify the mechanics of tissue stapling and associated phenomena. Various stapling modalities and several designs of circular staplers were investigated to evaluate the impact of the device on tissues and mechanical performance of the end-to-end colorectal anastomosis. Numerical simulations demonstrated that a single row of staples is not adequate to resist leakage due to non-linear buckling and opening of the tissue layers between two adjacent staples. Compared to the single staple row configuration, significant increase in stress experienced by the tissue at the inner staple rows was observed in two and three rows designs. On the other hand, adding second and/or third staple row had no effect on strain in the tissue inside the staples. Variable height design with higher staples in outer rows significantly reduced the stresses and strains in outer rows when compared to the same configuration with flat cartridge. Amsterdam Elsevier 2012 4 Journal of Biomechanics 45 115 2693 2697 10.1016/j.jbiomech.2012.07.021 campus https://doi.org/10.1016/j.jbiomech.2012.07.021 Fachbereich Medizintechnik und Technomathematik OPUS4-3994 Wissenschaftlicher Artikel Pham, Phu Tinh, ; Vu, Khoi Duc, ; Tran, Thanh Ngoc, tran@fh-aachen.de; Staat, Manfred, m.staat@fh-aachen.de A primal-dual algorithm for shakedown analysis of elastic-plastic bounded linearly kinematic hardening bodies 2010 6 ECCM 2010, IV European Conference on Computational Mechanics, Paris, France, May 16-21, 2010. 1 7 weltweit http://www.eccm2010.org/complet/fullpaper_901.pdf Fachbereich Medizintechnik und Technomathematik OPUS4-3596 Wissenschaftlicher Artikel Staat, Manfred, m.staat@fh-aachen.de; Tran, Thanh Ngoc, tran@fh-aachen.de; Kreißig, R., Load bearing capacity of thin shell structures made of elastoplastic material by direct methods 2008 10 Technische Mechanik. 28 (2008), H. 3-4 299 309 weltweit http://www.uni-magdeburg.de/ifme/zeitschrift_tm/2008_Heft3_4/13_Staat_Kreissig_Tran.pdf Fachbereich Medizintechnik und Technomathematik OPUS4-208 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de; Tran, Thanh Ngoc, tran@fh-aachen.de; Pham, Phu Tinh, Limit and shakedown reliability analysis by nonlinear programming 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. 2008 Fachbereich Medizintechnik und Technomathematik OPUS4-8150 Teil eines Buches Tran, N. T., ; Tran, Thanh Ngoc, tran@fh-aachen.de; Matthies, M. G., ; Stavroulakis, G. E., ; Staat, Manfred, m.staat@fh-aachen.de Shakedown Analysis Under Stochastic Uncertainty by Chance Constrained Programming 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. Cham Springer 2017 18 Advances in Direct Methods for Materials and Structures 978-3-319-59810-9 85 103 10.1007/978-3-319-59810-9_6 campus http://doi.org/10.1007/978-3-319-59810-9_6 Fachbereich Medizintechnik und Technomathematik