bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigations in the field of material mechanics using strain gages
Authors: Lehmann Thomas , Stockmann Martin , Ihlemann Jörn 
Published: December 2018

AbstractIn this contribution, investigations of the stress‐strain behavior of different metals using strain gage technique are presented. The measurement of strains using strain gages provides high measuring accuracy. In case of large deformations, the nonlinearity of the resistance‐strain‐relation, including elastic and plastic strain of the gage grid material, has to be considered. Moreover, for the detection of large deformations, high‐elongation strain gages and special bonding adhesives are used. Furthermore, at larger resistance changes the nonlinearity of the Wheatstone bridge has to be taken into account. As an example, the stress‐strain behavior of the steel 50CrV4 with 3 different process states in the small deformation range during tensile tests is demonstrated. The differences of the resulting stress‐strain curves of the material in the different process states are analyzed. Additionally, specimens of the aluminum alloy EN AW‐2024 are investigated in a large deformation range using tensile tests. Therein, the strain transmission enabled by the bonding is in the special focus. Furthermore, results of the large deformation tests are compared to the strain measurement using Digital Image Correlation.
Computational stability analysis of magnetorheological elastomers across scales
Authors: Keip Marc‐André , Polukhov Elten 
Published: December 2018

AbstractThe present contribution discusses the computational multiscale stability analysis of magnetorheological elastomers (MRE) across multiple length scales. The effective properties of the MRE are determined by means of computational homogenization over representative volume elements (RVE). Localization‐type macroscopic instabilities are detected by checking the strong‐ellipticity condition of homogenized moduli. At micro‐level, bifurcation‐type instabilities are treated by means of a finite‐element based Bloch‐Floquet wave analysis. The latter allows to find changed periodicities of microstructures as well as critical macroscopic loading points. Some representative numerical examples demonstrate various aspects of instabilities occurring in MREs.
Stacking Sequence Optimization of Multilayer Composite Materials
Authors: Loske Simon , Barthold Franz‐Joseph 
Published: December 2018

AbstractThe application of composite materials in various types of devices has increased steadily in the past decades. Hence, it is worth investigating into the structural behavior of these materials. The optimization of stacking sequences in multilayer composite materials opens a large field of improvements in industrial applications of composite materials. The center of investigation is set on fiber reinforced laminate plies, which are examined in the case of linear anisotropic theory of elasticity and applied to an isoparametric shell element formulation. For these mechanical systems, the modeling approach using lamination parameters is consulted. Under application of these lamination parameters, an optimization problem is formulated which uses an optimization procedure based on the SQP algorithm that optimizes the material properties of laminates to maximize the stiffness of the considered structure. The material properties obtained by the optimization of the lamination parameters are converted into possible stacking sequences for laminates by using simplified approaches.
Influence of friction‐induced heating on the dynamic behaviour of rotors supported by journal bearings
Authors: Irmscher Cornelius , Nitzschke Steffen , Daniel Christian , Woschke Elmar 
Published: December 2018

AbstractDifferent oil‐film‐induced instabilities have to be accounted for when designing rotor systems supported by hydrodynamic bearings. Because the system's behaviour is strongly dependent on the thermal state, this contribution presents an approach for calculating the thermo‐hydrodynamic behaviour of a bearing‐rotor‐system. It incorporates a solution of the three‐dimensional energy equation for the fluid film and accounts for heat conduction through the surrounding parts of the bearing. The simulation model is validated with the help of experimental data and improvements are pointed out compared to an isothermal approach.
Mesh Bias for the Eigenerosion Approach
Authors: Qinami Aurel , Kaliske Michael 
Published: December 2018

AbstractIn fracture mechanics, having the right crack path is a necessary condition for achieving reliable results. On the other hand, a discretized continuum is unable to represent a random crack path perfectly. Thus, challenges lie ahead on the accuracy of the numerical representation of this crack. Albeit the eigenfracture scheme has been well established in the recent years, different simulation results have shown some dependencies of the crack path on the mesh orientation, particularly when dealing with unstructured meshes. An r‐adaptive mesh refinement technique is introduced in this work, which circumvents possible mesh bias. In this regard, eroded finite elements are adaptively aligned in the direction of configurational forces calculated at the crack tip. Investigating the bounds of the eigenerosion scheme related to meshing and the introduction of possible improvements contribute to avoiding mesh induced anisotropy and further consolidate the approach.
The effect of the medium‐range configuration on the atomistic fracture behaviour of vitreous silica
Authors: Ebrahem Firaz , Bamer Franz , Markert Bernd 
Published: December 2018

AbstractUsing molecular dynamics simulations, we prepare vitreous silica by quenching molten silica to ambient temperature. Varying the quenching rate, we show that the latter barely influences the short‐range order, whereas the medium‐range configuration is significantly affected. We subject the prepared silica specimens to tension until fracture occurs and demonstrate the effect on the material behaviour. We evaluate the medium‐range configuration in terms of the ring statics of the glass network structure. Linking the ring statistics with the deformation and fracture behaviour of vitreous silica, we provide a topologically motivated explanation of the material behaviour.
Chemical active porous media with internal mass exchange
Authors: Sauerwein Malte , Steeb Holger 
Published: December 2018

AbstractThe aim of this contribution is to model a multiphasic material subjected to internal phase transition. The material is composed of a porous matrix, while the pore space is simultaneously filled with an aqueous pore fluid and a visco‐elastic gel. The latter one is made of a granulate of cross‐linked polyelectrolytes, also known as superabsorbent polymers (SAPs). Depending on the pore fluid chemistry, e. g. the concentration of mobile ions, the polymer phase absorbs water from the pore fluid and transforms to a hydrogel. Since the hydro‐mechanical properties of the overall mixture, e. g. the intrinsic permeability, depends on the phase transition process in the void space, a reliable constitutive modeling for the inter‐phase mass exchange has been carried out. In addition, comparison with experimental data shows that the derived continuum model is able to mimic phase transition processes for different NaCl concentrations in the pore liquid.
Computational modelling of fretting wear of Ti‐6Al‐4V incorporating cyclic plastic deformations and the debris evolution
Authors: Zhang Le , Ma Songyun , Markert Bernd 
Published: December 2018

AbstractIn the present work, a new fretting wear model taking account of the dynamic evolution of the debris layer is proposed to predict the wear profile under gross sliding conditions. The dynamic evolution of the debris layer is described by an exponential function of the debris thickness. A multi‐linear kinematic hardening model is employed to describe the cyclic plastic deformation of Ti‐6Al‐4V. The ejection rate of debris is computed to account for the accumulation of the debris thickness. Different wear configurations are used to validate the predictive ability of the proposed wear model. The simulation results show that the proposed approach provides a reasonable prediction of wear profiles in different wear configurations.
Partitioned simulation of multi‐field problems – efficient and robust coupling of fluids and structures
Authors: Radtke Lars , Lampe Tobias , Abdel‐Maksoud Moustafa , Düster Alexander 
Published: December 2018

AbstractStrongly coupled multifield problems arise in various engineering applications. Fluid‐structure interaction problems are one of the most prominent examples, especially in maritime applications. Choosing a partitioned solution approach allows to reuse existing software that was specialized to solve the underlying structural and fluid dynamics subproblems. In this work, the general partitioned solution approach is applied to investigate the hydrodynamics around an elastic marine‐propeller. The software library comana is used to steer the solution process. It allows to couple a boundary element solver for the fluid subproblem with a finite element solver for the structural subproblem. It is shown that novel convergence acceleration methods ensure a stable and efficient simulation for different coupling algorithms.
The effect of the collagen fibrils network on the damage behaviour of articular cartilage: a computational study
Authors: Liu Dongxu , Ma Songyun , Stoffel Marcus , Markert Bernd 
Published: December 2018

AbstractCollagen fibrils are the main composition of articular cartilage. The aim of this work is to study the influence of the collagen network on the damage behaviour of articular cartilage by employing a multiscale computation approach. For this purpose, a visco‐hyperelastic damage model based on the finite strain theory is proposed to describe the damage process of collagen fibrils. Stress and damage distributions are investigated to determine the influence of the fibril morphology on the cartilage damage. The computation results reveal that the location and magnitude of the damage in cartilage are strongly dependent on the orientation, distribution and the ratio between the primary and secondary level of the collagen fibrils.
Numerical Analysis for Time‐Dependent Electromagnetic Field Control
Authors: Bommer Vera , Yousept Irwin 
Published: December 2018

AbstractAn optimal control problem of the full time‐dependent Maxwell equations and its numerical approximation are presented. A mixed finite element discretization in space and a Crank‐Nicolson scheme for the time‐dependent Maxwell equation lead to a discretized optimal control problem. A numerical example illustrates our approach.
Smoothed Particle Hydrodynamics model of poroelasticity‐fluid coupling
Authors: Osorno Maria , Steeb Holger 
Published: December 2018

AbstractAnalysis of hydraulic fracturing is highly relevant in the exploration and production of geothermal energy. The simulation of fluid‐filled fractures in porous media requires to model the coupling between a fracture saturated with a compressible fluid and a surrounding (fluid‐saturated) poroelastic rock. A numerical investigation of hydraulical fracturing in poroelastic media includes the treatment of evolving fractures and possible large deformations. The use of classical mesh‐based methods in these cases implies computationally expensive geometrical meshing and remeshing pre‐processing. Furthermore, employing mesh‐based methods may entail other error sources, such as mesh distortions and fracture mesh‐alignment. To overcome these difficulties, we use the meshless method Smoothed Particle Hydrodynamics (SPH). We apply the proposed model to low‐ratio fractures with rough surfaces and analyze the effect the fractures asperities.
Control design for a 2 ⊗ 2 hyperbolic system with application to preferential crystallization
Authors: Zuyev Alexander , Benner Peter 
Published: December 2018

AbstractThis paper deals with a mathematical model of the preferential crystallization of enantiomers. The dynamics is governed by two first‐order partial differential equations with controls appearing in the coefficients and in the boundary conditions. We study the problem of stabilizing the equilibrium of this system by a one‐dimensional input. For this purpose we construct a Lyapunov functional in the integral form whose density is defined through solutions of auxiliary ordinary differential equations. It is shown that the time derivative of this functional along the trajectories of the closed‐loop system is negative semidefinite. We also discuss some extensions of these results for the construction of a strict Lyapunov functional.
Model and Parameter Study of a Shape‐Adaptable Beam for Vibration Control
Authors: Nowak Alexander , Willner Kai , Hasse Alexander 
Published: December 2018

AbstractShape adaptation is an effective approach for vibration damping. In this context, a numerical model of a slender, shape‐adaptable beam is introduced. The beam is essentially an arrangement of compliant ribs which are interconnected by a hull structure. The compliant ribs are characterized by at least two desired deformations modes with a low modal stiffness, whereas the remaining modes are considerably stiffer. By actively exciting the first desired deformation mode, the cross‐sectional stiffness of the beam can be altered between a low and a high stiffness state and therefore, the vibration behavior of the beam can be influenced.In detail, this paper presents a surrogate model of the compliant ribs which easily allows for modifying the stiffness properties of the ribs by a low number of parameters. The surrogate model is integrated in the FE‐modelled hull structure in order to simulate the 3D behavior of the entire structure. The influence of shape adaptation on the dynamic behavior of the free vibrating beam as well as for excited oscillation is examined. Especially, modal energies and their transfer between the modes due to the shape adaptation are considered. In addition, we are conducting a study on the parameters of the surrogate model in order to gain a deeper insight into the complex interrelationships of vibration reduction through shape adaptation.
Taylor approximation for PDE‐constrained optimization under uncertainty: Application to turbulent jet flow
Authors: Chen Peng , Villa Umberto , Ghattas Omar 
Published: December 2018

AbstractWe present a scalable method for PDE‐constrained optimization under high‐dimensional uncertainty. The method is based on a functional Taylor approximation of the cost functional with respect to (w.r.t.) the random parameter field. We consider a risk‐averse optimization formulation via a mean‐variance measure for the control objective. A quadratic Taylor approximation of the control objective gives rise to a function involving the trace of the Hessian of the objective w.r.t. the random parameter, preconditioned by the covariance operator. We apply a randomized SVD algorithm to estimate the trace, which is demonstrated to be scalable w.r.t. the parameter dimension, i.e., the number of PDE solves is independent of the parameter dimension and depends only on the decay of the eigenvalues of the covariance‐preconditioned Hessian (which is typically dimension‐independent). We solve the resulting generalized eigenproblem‐constrained optimization problem by a quasi‐Newton method. We apply our method to a RANS turbulence model with an infinite‐dimensional random field representing model inadequacy, and demonstrate scalability on discretized problems with parameter dimensions up to one million.
A new material approach towards shear cutting of fiber reinforced plastics
Authors: Poggenpohl Lukas , Wulfinghoff Stephan , Reese Stefanie 
Published: December 2018

AbstractThe aim of this project is to develop and validate a new material model to simulate the material behavior of carbon fiber reinforced plastics (CFRP) during shear cutting. Here, the focus lies on the initiation and evolution of damage in the cutting plane. A geometrically nonlinear elastic‐brittle material model with non local damage variables will be used.
Passive Vibration Control by Frictional Energy Dissipation in Refrigerant‐Lubricated Gas Foil Bearing Rotor Systems
Authors: Leister Tim , Seemann Wolfgang , Bou‐Saïd Benyebka 
Published: December 2018

AbstractEven though the dynamic performance of rotors supported by refrigerant‐lubricated gas foil bearings (GFBs) is very sensitive to the amount of energy dissipated in the foil structure, almost none of the existing computational models really capture dry friction with typical stick–slip transitions. The presented work addresses this shortcoming by incorporating an elasto‐plastic bristle friction law into the structural model, which is coupled in an interconnected solution approach to a Reynolds equation for non‐ideal compressible gases and to a modified Jeffcott–Laval rotor model. Numerical results confirm that properly designed GFBs have the potential to benefit significantly from the foil structure acting as a passive vibration control device.
Modelling of constrained layer damping for bending waves in frequency domain using finite shell elements
Authors: Dorn Matthias , Langer Sabine Christine 
Published: December 2018

AbstractConstrained layer damping (CLD) is a damping principle which utilizes a viscoelastic layer between two elastic covering layers. Bending of the resulting plate structure mainly causes shear deformation in the viscoelastic layer which in theory leads to more efficient dissipation than damping due to pure strain deformation. This principle is brought into application by applying damping tape to the surface of a metallic base plate. Since extensive use of damping tape is economically expensive, a common aim is to achieve maximum dissipation with a limited amount of modified area. Therefore, there is an interest in predicting the optimal distribution of a given amount of damping tape by numerical simulations. In most applications where the Finite Element Method (FEM) is applied, shell elements are preferred over volume elements, because the shell elements are computationally more efficient. To be able to model CLD with shell elements, a mechanical model has to be derived first that represents the three layer structure with homogenized parameters. In this contribution, CLD is modelled in two different ways and solved with FEM: First, an experimentally validated volume model of a CLD‐structure and second, an effective material model using shell elements. The frequency responses of both models are compared.
Analyzing the Secretome of Gut Microbiota as the Next Strategy For Early Detection of Colorectal Cancer
Authors: Megat Mohd Azlan Putri‐Intan‐Hafizah , Chin Siok‐Fong , Low Teck Yew , Neoh Hui‐min , Jamal Rahman 
Published: December 2018

AbstractDysbiosis of gut microbiome can contribute to inflammation, and subsequently initiation and progression of colorectal cancer (CRC). Throughout these stages, various proteins and metabolites are secreted to the external environment by microorganisms or the hosts themselves. Studying these proteins may help enhance our understanding of the host–microorganism relationship or they may even serve as useful biomarkers for CRC. However, secretomic studies of gut microbiome of CRC patients, until now, are scarcely performed. In this review article, the focus is on the roles of gut microbiome in CRC, the current findings on CRC secretome are highlighted, and the emerging challenges and strategies to drive forward this area of research are addressed.
UCP2 Overexpression Redirects Glucose into Anabolic Metabolic Pathways
Authors: Sreedhar Annapoorna , Cassell Teresa , Smith Parker , Lu Daiwei , Nam Hyung W. , Lane Andrew N. , Zhao Yunfeng 
Published: December 2018

AbstractUncoupling protein 2 (UCP2) is often upregulated in cancer cells. The UCP2 upregulation is positively correlated with enhanced proliferation, tumorigenesis, and metabolic alterations, thus suggesting that UCP2 upregulation can play a key role in sensing metabolic changes to promote tumorigenesis. To determine the global metabolic impact of UCP2 upregulation, 13C6 glucose as a source molecule is used to “trace” the metabolic fate of carbon atoms derived from glucose. UCP2 overexpression in skin epidermal cells enhances the incorporation of 13C label to pyruvate, tricarboxylic acid cycle intermediates, nucleotides, and amino acids, suggesting that UCP2 upregulation reprograms cellular metabolism toward macromolecule synthesis. To the best of our knowledge, this is the first study to bring to light the overall metabolic differences caused by UCP2 upregulation.
Revisiting reweighted robust standard deviation estimators for univariate Shewhart S‐charts
Authors: Mutlu Ece Çiğdem , Alakent Burak 
Published: December 2018

AbstractPhase I outliers, unless screened during process parameter estimation, are known to deteriorate Phase II performance of process control charts. Reweighting estimators, ie, trimming outlier subgroups and individual observations, were suggested in the literature to improve both the robustness and efficiency of the resulting parameter estimates. In the current study, effects of various reweighted estimators at different trimming levels on the Phase II performance of S‐charts are elucidated using computer simulations including isolated and mixtures of contamination models. Outlier magnitudes in the simulations are held at a moderately low level to mimic industrial practice. Subtleties, such as varying Type I error rate among different trimming levels with respect to quantiles of dispersion estimates, prevent a single method to be revealed as the best performing one under all circumstances, and choice of estimators and trimming levels should depend on the number of subgroups in Phase I and the specifics of the process. Nevertheless, S‐chart using scale M‐estimator with logistic ρ and location M‐estimator at 2% trimming generally stands out in terms of Phase II performance, and high trimming levels are particularly recommended for high number of Phase I subgroups.
Strong Surface‐Bound Sulfur in Carbon Nanotube Bridged Hierarchical Mo2C‐Based MXene Nanosheets for Lithium–Sulfur Batteries
Authors: Lv Li‐Ping , Guo Chao‐Fei , Sun Weiwei , Wang Yong 
Published: December 2018

AbstractIn this work, hydroxyl‐functionalized Mo2C‐based MXene nanosheets are synthesized by facilely removing the Sn layer of Mo2SnC. The hydroxyl‐functionalized surface of Mo2C suppresses the shuttle effect of lithium polysulfides (LiPSs) through strong interaction between Mo atoms on the MXenes surface and LiPSs. Carbon nanotubes (CNTs) are further introduced into Mo2C phase to enlarge the specific surface area of the composite, improve its electronic conductivity, and alleviate the volume change during discharging/charging. The strong surface‐bound sulfur in the hierarchical Mo2C‐CNTs host can lead to a superior electrochemical performance in lithium–sulfur batteries. A large reversible capacity of ≈925 mAh g−1 is observed after 250 cycles at a current density of 0.1 C (1 C = 1675 mAh g−1) with good rate capability. Notably, the electrodes with high loading amounts of sulfur can also deliver good electrochemical performances, i.e., initial reversible capacities of ≈1314 mAh g−1 (2.4 mAh cm−2), ≈1068 mAh g−1 (3.7 mAh cm−2), and ≈959 mAh g−1 (5.3 mAh cm−2) at various areal loading amounts of sulfur (1.8, 3.5, and 5.6 mg cm−2) are also observed, respectively.