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 OPUS4-11004 Buch (Monographie) Staat, Manfred, m.staat@fh-aachen.de; Digel, Ilya, digel@fh-aachen.de; Trzewik, Jürgen, ; Sielemann, Stefanie, ; Erni, Daniel, ; Zylka, Waldemar, Symposium Proceedings; 4th YRA MedTech Symposium 2024 : February 1 / 2024 / FH Aachen Duisburg Universität Duisburg-Essen 2024 40 Seiten 978-3-940402-65-3 10.17185/duepublico/81475 weltweit https://doi.org/10.17185/duepublico/81475 Fachbereich Medizintechnik und Technomathematik OPUS4-11083 Wissenschaftlicher Artikel Zhen, Manghao, ; Liang, Yunpei, ; Staat, Manfred, m.staat@fh-aachen.de; Li, Quanqui, ; Li, Jianbo, Discontinuous fracture behaviors and constitutive model of sandstone specimens containing non-parallel prefabricated fissures under uniaxial compression 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. Amsterdam Elsevier 2024 13 Seiten Theoretical and Applied Fracture Mechanics 131 Art. No. 104373 10.1016/j.tafmec.2024.104373 campus https://doi.org/10.1016/j.tafmec.2024.104373 Fachbereich Medizintechnik und Technomathematik OPUS4-10589 Konferenzveröffentlichung Tran, Ngoc Trinh, Trinh.tran@fh-aachen.de; Trinh, Tu Luc, ; Dao, Ngoc Tien, ; Giap, Van Tan, ; Truong, Manh Khuyen, ; Dinh, Thuy Ha, ; Staat, Manfred, m.staat@fh-aachen.de Limit and shakedown analysis of structures under random strength 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. Hanoi Nha xuat ban Khoa hoc tu nhien va Cong nghe (Verlag Naturwissenschaft und Technik) 2022 8 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 978-604-357-084-7 510 518 weltweit https://www.researchgate.net/publication/366053333_Shakedown_analysis_of_structures_under_random_strength_by_chance_constrained_programming Fachbereich Medizintechnik und Technomathematik 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 OPUS4-10346 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de; Tran, Ngoc Trinh, Trinh.tran@fh-aachen.de Strain based brittle failure criteria for rocks 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. Hanoi Nha xuat ban Khoa hoc tu nhien va Cong nghe (Verlag Naturwissenschaft und Technik) 2022 9 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 978-604-357-084-7 500 509 weltweit https://www.researchgate.net/publication/366053178_Strain_based_failure_criteria_for_rocks Fachbereich Medizintechnik und Technomathematik OPUS4-10372 Wissenschaftlicher Artikel Tran, Ngoc Trinh, ; Trinh, Tu Luc, ; Dao, Ngoc Tien, ; Giap, Van Tan, ; Truong, Manh Khuyen, ; Dinh, Thuy Ha, ; Staat, Manfred, m.staat@fh-aachen.de FEM shakedown analysis of structures under random strength with chance constrained programming 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. Vietnam Academy of Science and Technology (VAST) 2022 14 Vietnam Journal of Mechanics 44 4 459 473 10.15625/0866-7136/17943 weltweit https://doi.org/10.15625/0866-7136/17943 Fachbereich Medizintechnik und Technomathematik OPUS4-10434 misc Topcu, Murat, ; Madabhushi, Gopal Santana Phani, ; Staat, Manfred, m.staat@fh-aachen.de Datasets from FEM Simulations done with COMSOL Multiphysics and Code_Aster Datasets from FEM Simulations done with COMSOL Multiphysics and Code_Aster for an elastic stress transfer between matrix and fibres having a variable radius. 2022 Forschungsdaten 10.6084/m9.figshare.19333295.v2 weltweit https://doi.org/10.6084/m9.figshare.19333295.v2 Fachbereich Medizintechnik und Technomathematik OPUS4-9877 Wissenschaftlicher Artikel Topçu, Murat, ; Madabhushi, Gopal S.P., ; Staat, Manfred, m.staat@fh-aachen.de A generalized shear-lag theory for elastic stress transfer between matrix and fibres having a variable radius 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. New York, NY Elsevier 2022 International Journal of Solids and Structures 239–240 Art. No. 111464 10.1016/j.ijsolstr.2022.111464 bezahl https://doi.org/10.1016/j.ijsolstr.2022.111464 Fachbereich Medizintechnik und Technomathematik OPUS4-9897 Wissenschaftlicher Artikel Defosse, Jerome, ; Kleinschmidt, Joris, ; Schmutz, Axel, ; Loop, Torsten, ; Staat, Manfred, m.staat@fh-aachen.de; Gatzweiler, Karl-Heinz, gatzweiler@fh-aachen.de; Wappler, Frank, ; Schieren, Mark, Dental strain on maxillary incisors during tracheal intubation with double-lumen tubes and different laryngoscopy techniques - a blinded manikin study New York, NY Elsevier 2022 6 Journal of Cardiothoracic and Vascular Anesthesia 36 8, Part B 3021 3027 10.1053/j.jvca.2022.02.017 bezahl https://doi.org/10.1053/j.jvca.2022.02.017 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