bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of inferior turbinate reconstruction with Medpor for the treatment of empty nose syndrome
Authors: Jiang Chenyan , Shi Runjie , Sun Yiyuan
Published: December 2012

Objectives/Hypothesis

Patients with empty nose syndrome experience considerable discomfort in their daily lives and treatment is difficult for their physicians. The purpose of this study was to evaluate the outcome of an empty nose syndrome treatment via reconstruction of the inferior turbinate with porous polyethylene (Medpor).

Design and Method

A prospective self‐controlled study was conducted, and 19 patients suffering from empty nose syndrome underwent a surgical therapy through submucosal implantation of Medpor in order to reconstruct their inferior turbinate. The outcome was assessed by comparison of the preoperative and follow‐up symptoms, nasal endoscopy findings, CT scans, mucociliary clearance, acoustic rhinometry, and the Sino‐Nasal Outcome Test‐20 scores.

Results

In a follow‐up period of 3 to 18 months, all patients reported subjective symptom improvements and a statistically significant improvement of the Sino‐Nasal Outcome Test scores was achieved (P < 0.05). Mucociliary clearance assessments showed improvements at 3, 6, and 12 months postoperatively, but without statistical significance. Acoustic rhinometry assessments showed postoperative improvements of nasal resistance, nasal volume, and minimum cross‐sectional area with a significant overall average score (P < 0.05).

Conclusion

The reconstruction of inferior turbinate with Medpor is a new promising approach to treat patients with empty nose syndrome.

Level of Evidence

4.
Syntheses and Properties of Novel Copolymers of Poly(1,4‐dioxane‐2‐one) and Aliphatic Polycarbonate Based on Ketal‐Protected Dihydroxyacetone
Authors: Wang Lian‐Sheng , Cheng Si‐Xue , Zhuo Ren‐Xi
Published: December 2012

Novel random copolymers of 1,4‐dioxane‐2‐one (DON) and 2,2‐ethylenedioxy‐1,3‐propanediol carbonate (EOPDC) are synthesized in bulk at 120 °C using Sn(Oct)2 as a catalyst. The effects of different molar feed ratios of EOPDC/DON on the yield and molecular weight of the copolymers are investigated. The copolymers are obtained with a yield of 55.4–98%. The number‐average molecular weight of the copolymer is 0.49–4.18 × 104 g mol−1 with a polydispersity of 1.52–1.68. The poly(DON‐co‐EOPDC)s obtained are characterized by FTIR, 1H NMR, and 13C NMR spectroscopy, gel‐permeation chromatography (GPC), and DSC. The hydrolytic degradation of the copolymer in phosphate buffered saline (PBS) is also investigated. The results show that both the hydrophilicity and the degradation rate of the copolymers increase with increasing copolymer DON content.
On the interrelation between dissipation and chemical energies in modeling shape memory alloys
Authors: Junker Philipp , Hackl Klaus
Published: December 2012

We use the principle of maximum dissipation for thermo‐mechanically coupled modeling of poly‐crystalline shape memory alloys (SMA). This modeling scheme demands approaches for both Helmholtz free energy and dissipation. For time‐independent processes, dissipation is usually modeled by the norm of the internal variable's rate times a factor. We show that for SMAs this factor is not an additional modeling parameter. In contrast, it can be calculated from the Helmholtz free energy. This reduces the number of model parameters and provides furthermore an interesting effect of the model which allows to display the material behavior in an even more realistic manner. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational Phase Field Modeling of Laminate Deformation Microstructure in Finite Gradient Crystal Plasticity
Authors: Hildebrand Felix , Miehe Christian
Published: December 2012

The macroscopic mechanical behavior of many materials crucially depends on the formation and evolution of their microstructure. In this work, we consider the formation and evolution of laminate deformation microstructure in plasticity. Inspired by work on the variational modeling of phase transformation [5] and building on related work on multislip gradient crystal plasticity [9], we present a new finite strain model for the formation and evolution of laminate deformation microstructure in double slip gradient crystal plasticity. Basic ingredients of our model are a nonconvex hardening potential and two gradient terms accounting for geometrically necessary dislocations (GNDs) by use of the dislocation density tensor and regularizing the sharp interfaces between different kinematically coherent plastic slip states. The plastic evolution is described by means of a nonsmooth dissipation potential for which we propose a new regularization. We formulate a continuous gradient‐extended rate‐variational framework and discretize it in time to obtain an incremental‐variational formulation. Discretization in space yields a finite element formulation which is used to demonstrate the capability of our model to predict the formation and evolution of laminate deformation microstructure in f.c.c. Copper with two active slip systems in the same slip plane. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Perspectives on Constructive and Functional Optimizing of a Serial Robot with Four Degrees of Freedom Destined for Special Applications
Authors: Petrişor Silviu Mihai , Bârsan Ghiţă
Published: December 2012

This paper deals with aspects on the dynamic modulation of the robots mechanical structure, using Lagrangian formalism, choosing the adequate DC servomotors, translation modules constituting the TTRT robot, the constructive solution and modelling the three translation subassemblies of the studied robot, with the intention that, in the end, based on a dynamic‐organologic algorithm, a functional optimization of the robot be brought out within a workcell destined for special applications, so that the energetic consumption be as low as possible. This paper also presents the organological calculi and solutions for the efficient design of modules specific to mechanical structures of industrial serial‐modular robots. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Discrete Element Model for Degradation of Ballast Tracks
Authors: Ergenzinger Christian , Seifried Robert , Eberhard Peter
Published: December 2012

A Discrete Element Model that is capable to describe degradation of ballast tracks in consideration of breakage of the ballast stones is presented. Strong rock is modelled as a granular solid by introduction of breakable bonds with suitable failure criteria between adjacent particles. Irregular angular stones are generated from the granular solid and their crushing strength is evaluated. The degradation process of a ballast bed is assessed and related to the damage occurring to the individual stones. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐excited vibrations of deformable multibody systems due to friction: Explanation with the help of two point masses and a belt
Authors: Maier Christian , Glocker Christoph , Meier David
Published: December 2012

The aim of this paper is to present the results of the investigations of the ability of self‐excited vibrations due to friction in a planar simplified mechanical model, with a constant coefficient of friction. The Hurwitz criteria is used for the stability analysis and the determination of the critical value of the coefficent of friction. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Hamiltonian conserving indirect optimal control method for multibody dynamics
Authors: Siebert Ralf , Betsch Peter
Published: December 2012

In the past, a lot of effort has gone into the development of structure‐preserving time‐stepping schemes for forward dynamic problems. This is due to the superior numerical stability of these integrators. Guided by previous developments in the design of energy‐momentum integrators for forward dynamic problems, a Hamiltonian conserving indirect optimal control method will be introduced. For the state equations, a consistent variant of the midpoint evaluation introduced in [1] will be applied. Based on this specific discretization of the state equations, a discretization of the costate equations will be introduced, which is based on the notion of a discrete derivative and which leads to the algorithmic conservation of the discrete Hamiltonian. The newly developed method will be compared with a direct transcription method. We will test the newly proposed method within two numerical examples, which are the optimal control of a particle in a gravitational field and a 3‐link manipulator. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Analysis of Multibody Systems in the Presence of Uncertainties
Authors: Walz Nico‐Philipp , Hanss Michael
Published: December 2012

This contribution introduces and illustrates the concept of fuzzy arithmetic as a modeling and analysis tool for the simulation of multibody systems subjected to uncertainties. The uncertainties are described by the use of fuzzy numbers and the simulation procedure is performed by employing the Transformation Method, which is a practical methodology for the implementation of fuzzy arithmetic. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hybrid coordinate approach for the modelling and simulation of multibody systems
Authors: Becker Christian , Betsch Peter , Franke Marlon , Siebert Ralf
Published: December 2012

The main goal of the present work is to provide an add‐on scheme for the formulation of multibody dynamics, based on natural coordinates, in regard to ideally balanced rigid bodies with high rotational spin, e.g. gyroscopes. The underlying aim of this approach is to achieve higher numerical accuracy whenever the preferred axis of rotation coincides with the balanced main axis of the body. This will be achieved by seperating the spin of the balanced rigid body along the denoted axis as an additional angular coordinate, whereas the other rotations will be covered by a carried frame, parameterized via natural coordinates. At the same time the carried frame provides a link to the existing modelling framework in terms of natural coordinates, enabling a straightforward implementation into existing multibody systems (e.g. rotary crane [2]). (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Natural co‐ordinates for control applications
Authors: Sänger Nicolas , Betsch Peter
Published: December 2012

Natural coordinates have emerged to be well‐suited for both rigid and flexible multibody dynamics. Especially the combination of structural elements and energy‐momentum consistent time stepping schemes leads to superior numerical stability as well as an automatable assembly, resulting in both excellent run‐time behaviour as well as moderate modelling effort (see [1]). Incorporation of modern methods for finite‐element simulations, such as mortar methods for contact or domain decomposition both for structural elements as well as continuum elements is straightforward ([2]).

Augmentation techniques allow a systematic integration of both mechanical and non‐mechanical quantities for simulation (see [3] and [4]), which makes this approach suitable especially for emulation and simulation of mechatronic systems. We will present an approach for evaluating forward control strategies with flexible multibody systems. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Topology Optimization of Members of Elastic Multibody Systems
Authors: Held Alexander , Seifried Robert
Published: December 2012

Lightweight techniques are applied increasingly often for modern machine designs in order to reduce the moving masses and therewith the energy consumption. However, as a result the stiffness of the system decreases causing undesired elastic deformations and therewith end‐effector deviations. In this work a topology optimization procedure for elastic multibody systems based on the solid isotropic material with penalization approach is presented to lower end‐effector tracking errors. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Maxwell‐Contact
Authors: Grundl Kilian , Cebulla Thomas , Schindler Thorsten , Ulbrich Heinz
Published: December 2012

In multibody systems, two alternative approaches exist to compute contact forces between bodies. The unilateral constraint contact and the unilateral regularized contact do not take into account the influence of the deformation due to other contacts on a body using rigid body dynamics. In this paper, a third alternative, i.e. the Maxwell‐Contact, is derived coupling the deformations of different contacts on one body quasi‐statically. An academic example validates the fundamental properties of the contact model and the application in a simulation of a pushbelt CVT shows improved results. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recursive Methods in Modeling and Control of Modular Robotic Systems
Authors: Oberhuber Bernhard , Gattringer Hubert , Bremer Hartmut , Fellhauer Bruno
Published: December 2012

This paper addresses the dynamical modeling and control of reconfigurable modular robots. The modular actuators (brushless DC motors with Harmonic Drive gears) for the robots under consideration are connected by rigid links. This way the robot can be assembled in different configurations by rearranging these components. For dynamical modeling the Projection Equation in Subsystem representation is used, taking advantage of its modular structure. Due to the lack of position sensors at the gearbox output shaft, deflections caused by the elasticities in the gears can not be compensated by the PD motor joint controller. Therefore, a correction of the motor trajectory is needed, which can be calculated as part of a flatness based feed‐forward control using the exact model of the robot. With the recursive approach proposed in this paper the concept of reconfigurability is retained. For validation a redundant articulated robot arm with seven joints is regarded and results are presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A modular and efficient approach to computational modeling and sensitivity analysis of robot and human motion dynamics
Authors: Friedmann Martin , Wojtusch Janis , von Stryk Oskar
Published: December 2012

In this paper a new class library for the computation of the forward multi‐body‐system (MBS) dynamics of robots and biomechanical models of human motion is presented. By the developed modular modeling approach the library can be flexibly extended by specific modeling elements like joints with specific geometry or different muscle models and thus can be applied efficiently for a number of dynamic simulation and optimization problems. The library not only provides several methods for solving the forward dynamics problem (like articulated body or composite rigid body algorithms) which can transparently be exchanged. Moreover, the numerical solution of optimal control problems, like in the forward dynamics optimization of human motion, is significantly facilitated by the computation of the sensitivity matrix with respect to the control variables. Examples are given to demonstrate the efficiency of the approach. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical and experimental investigation of cartilage replacement material for medical applications
Authors: Zhou B. , Stoffel M. , Weichert D. , Rath B.
Published: December 2012

Soft tissues are commonly applied in surgery to replace the injured articular cartilage. Many biological researches were carried out through mechanical and histological experiments. They focus on the function, degeneration and regeneration of the articular cartilage and fibrocartilage. The aim of the presented work is to develop a method to characterize the mechanical properties of different kinds of soft tissues and to trace the evolution of elastic properties in implants during the remodeling process. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and simulation of injecting acrylic bone cement into osteoporotic vertebral bones within percutaneous vertebroplasty
Authors: Kolmeder Sebastian , Lion Alexander , Landgraf Ralf , Ihlemann Jörn , Lebsack Helena , Kober Cornelia , Blattert Thomas R.
Published: December 2012

Percutaneous vertebroplasty is a common clinical procedure to treat vertebral compression fractures and osteoporotic vertebral bodies. However, this operation technique is accompanied by different complications due to lack of knowledge about the complicated behaviour of bone cement within the human body. To contribute to a better understanding of the processes that take place inside the body during a vertebroplasty, a detailed model of the thermomechanical behaviour of acrylic bone cement has been developed. All important effects are covered, that influence the behaviour of acrylic bone cement during the injection in a human vertebral body. Implemented in the opensource CFD‐code OpenFOAM®, first results show that this comprehensive simulation of the minimal invasive injection is capable to accurately predict the cement distribution and temperature field of acrylic bone cement inside the vertebral body. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupling 3D and 1D Skeletal Muscle Models
Authors: Sprenger Michael , Schmitt Syn , Röhrle Oliver
Published: December 2012

This work introduces a modelling framework towards a forward dynamics simulation of skeletal muscle mechanics that couples three‐dimensional (3D) continuum‐mechanical‐based Finite Element (FE) simulations to rigid body simulations. In this regard, this is a methodological approach, which incorporates different methods to realise simulations of the musculoskeletal system. Such simulations are at present computationally not feasible.

To set up such a modelling framework the upper limp is selected. Here, the upper limb consists of an antagonistic muscle pair, the elbow (a simple hinge joint) and an external load. The skeletal muscles are represented by a 3D continuum‐mechanical model. The tendons are, for now, assumed to be rigid. The results demonstrate the ability of the system to converge to a physiological realistic position. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Study of Psychoacoustic Effects of Noise Emitted by the Machine Tools Structure
Authors: Ţepeş‐Bobescu Alina‐Sabina , Ţepeç‐Bobescu Florin , Gligor Anamaria , Arghir Mariana
Published: December 2012

The main sources of noise at work, in industrial environments, are machine tools: namely, mechanical transmission structure composed of gears, bearings, electric motors drive and the cutting process. Generated vibrations are transmitted through structures, carcasses or directly to environment, developing a complex acoustic field around machine tools. In terms of occupational medicine, the noise is generated by a combination of vibrations producing sounds with different characteristics and that are produced in the workplace [2]. It is important to identify the dominant noise source, the cause of exceeding the admissible limits (87dB) and noise transmission mode to make an objective correlation with effects on humans [1]. Hearing loss can occur immediately at extreme sound levels, but, in general, the problem is noise exposure over time. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Remodelling Processes in Bones: A Biphasic Porous Media Model
Authors: Krause Robert , Schittler Daniella , Waldherr Steffen , Allgöwer Frank , Markert Bernd , Ehlers Wolfgang
Published: December 2012

In the context of the Theory of Porous Media (TPM), a continuum‐mechanical model is introduced to describe the complex fluid‐structure interaction in bone tissue on the macro‐scale. The tissue is treated as an aggregate of two immiscible constituents, where the cells and the bone matrix are summarised to the solid phase, and the fluid phase summarises the extracellular fluids and their components. The remodelling process is described on the macro‐scale by a distinct mass exchange that also causes a change of the constituents' material properties. In addition to the mechanical description, systems‐biological control mechanisms are included into the model by evaluating a systems‐biological cell interaction model at every integration point of the spatially discretised domain.

Here, an integrative solution strategy is presented for this combined mechanical and systems‐biological problem. Therein, the mechanical problem is treated using the Finite‐Element Method (FEM), where the systems‐biological problem is solved locally on integration point level in the sense of a collocation method. To reveal the whole capability of this approach, a 3‐dimensional numerical example of the remodelling process in the upper human femur under physiological loading conditions is presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic crack analysis in 2D elastic solids with the singular edge‐based smoothed finite element method
Authors: Bui Tinh Q. , Zhang Chuanzeng
Published: December 2012

The singular edge‐based smoothed finite element method (sES‐FEM) is developed for stationary dynamic crack analysis in two‐dimensional (2D) elastic solids. The paper aims at providing a better understanding of the dynamic fracture behaviors in linear elastic solids by means of the strain smoothing technique. The strains are smoothed and the system stiffness matrix is performed using the strain smoothing over the smoothing domains associated with the element edges. A two‐layer singular five‐node crack‐tip element is employed while the standard implicit time integration scheme is used for solving the discrete sES‐FEM equation system. Dynamic stress intensity factors (DSIFs) are extracted using the domain‐form of interaction integrals in terms of the smoothing technique. The normalized DSIFs are compared with reference solutions showing a high accuracy of the sES‐FEM. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interpretation of parameters in phase field models for fracture
Authors: Kuhn Charlotte , Müller Ralf
Published: December 2012

Phase field fracture models typically feature a length parameter, which controls the width of the diffuse transition zone between broken and undamaged material. In the limit case of a vanishing length parameter, these models converge to a sharp crack formulation. From this point of view, the length scale parameter is a purely auxiliary numerical quantity. However, the study of the stability of homogeneous solutions in a one dimensional setting permits a different interpretation. Since the length parameter is directly related to the critical stress at which the homogeneous solution becomes unstable and crack nucleation occurs, it can be related to the strength of the material. In this regard, the length parameter itself may be seen as a material parameter. These analytical findings are approved by finite element simulations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanical properties of hybrid composites made of a steel plate and a laminate connected by means of barbed studs
Authors: Zolkiewski Slawomir
Published: December 2012

In this paper the research results of hybrid composite materials made of a steel plate and laminates are presented. The tested composites were made of a metal sheet plate and a laminate plate connected by means of barbed studs. The laminates were made of three different types of fabrics with: fibreglass, carbon fibres and aramid fibres. As a warp, epoxide resin and polyester resin were used. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary Integral Equations in the Frequency Domain for Interface Cracks under Impact Loading
Authors: Menshykov Oleksandr , Menshykova Marina
Published: December 2012

In the study interface cracks between two dissimilar homogeneous isotropic half‐spaces undergoing impact loading are considered. The problem is solved using the boundary integral equations in the frequency domain. The distributions of the displacements and tractions at the bonding interface and surfaces of the cracks are obtained and analyzed. The stress intensity factors (opening and shear modes) are computed for different load conditions and various properties of the bimaterial. The results are compared with the ones obtained in the time domain. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic formulae for the flexibility of an infinite row of pin‐loaded holes
Authors: Kratochvil Jan , Becker Wilfried
Published: December 2012

The problem of the flexibility of an infinite row of pin‐loaded holes in an elastic plane or half‐plane is considered within the framework of the complex potential method [1] and the theory of compound asymptotic expansions [2]. The holes are loaded by a given distribution of normal stresses with a resultant equal to the overall transmitted force. First, the relative radius of the holes is introduced as a small parameter. Then, an asymptotic expansion of the complex potentials in terms of this small parameter is constructed. This expansion is uniformly valid in the whole domain, i.e. in the vicinity of the holes as well as in the far‐field. Finally, the flexibility of the row of pin‐loaded holes is evaluated using this solution. In this manner, closed‐form analytical approximations of the flexibility of an infinite row of pin‐loaded holes in a full plane and a half‐plane are obtained. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of domain decomposition methods to isogeometric analysis
Authors: Hesch Christian , Betsch Peter
Published: December 2012

During the past decade various new spatial discretization techniques have been developed. In particular, the usage of NURBS based shape functions, well known to the CAD community, has been adapted to finite element technology. In the present work we use the mortar finite element method for the coupling of nonconforming discretized sub‐domains in the framework of nonlinear elasticity. We show that the method can be applied to isogeometric analysis with little effort, once the framework of NURBS based shape functions has been implemented. Furthermore, a specific coordinate augmentation technique allows the design of an energy‐momentum scheme for the constrained mechanical system under consideration. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Incompatible Modes for Volumetric Shell Elements in Explicit Time Integration
Authors: Mattern Steffen , Schmied Christoph , Schweizerhof Karl
Published: December 2012

Explicit time integration is characterized by small time steps and efficient global operations, leading to a domination of element processing regarding CPU‐time, in particular, as diagonal mass matrices are used. The Enhanced Assumed Strain (EAS) approach requires local operations in order to condense‐out additional degrees of freedom. The method of Incompatible Modes (IM) is presented as an alternative, where incompatible degrees of freedom are included in the global equations, which leads to efficient element formulations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bayesian inference of linear time‐varying systems based on Hilbert‐Huang transform
Authors: Hu Han , Proppe Carsten
Published: December 2012

This paper proposes an identification method for general linear time‐varying (LTV) MDOF systems (including chainlike and non‐chainlike systems) based on the Hilbert‐Huang Transform (HHT). First, by using Bayesian Inference and a Transitional Markov Chain Monte Carlo (TMCMC) algorithm [1], initial knowledge about the system responses and the white noise in system responses is updated based on measured system responses, which yields the posterior distributions of the noise parameters. Second, each sample system responses are obtained from the posterior distribution and are processed by HHT in order to obtain intrinsic mode functions (IMFs) and the residue as well as the corresponding analytical IMFs and the analytical residue for system responses of each DOF. Finally, the above analytical signals for each DOF are summed respectively to form new analytical responses for each set of sample system responses, which are then used in the identification equations [2] to identify the distributions of system parameters. The proposed method is applied to chainlike and non‐chainlike LTV systems with three types of stiffness variations: smooth, abrupt and periodical variations. The effectiveness and accuracy of the proposed method on 1DOF and 2DOF systems is discussed in numerical simulations. System responses are perturbed by white noise, and the identified results demonstrate the robustness of the method. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy‐consistent time‐integration for a dynamic finite deformation thermoviscoelastic continuum
Authors: Krüger Melanie , Groß Michael , Betsch Peter
Published: December 2012

The main goal of the present work is to develop a structure‐preserving time integrator, which is based on the works of Öttinger [2] (GENERIC formalism) and Romero [4] (Thermodynamically consistent (TC) algorithm). This intergator is called the enhanced TC algorithm for thermoviscoelastic continuums. The underlying structure is then called enhanced GENERIC, analogously to the earlier puplished thermoviscoelastic double pendulum of Krüger et al. [1]. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature and displacement fields in brake and clutch systems with thermoelastic instabilities
Authors: Graf Matthias , Ostermeyer Georg‐Peter
Published: December 2012

In brake and clutch systems kinetic energy is converted into thermal energy. Experiments show that the corresponding temperature field can develop unstable periodic structures. The temperature field couples to the displacement field by thermal expansion. Local pressure maxima in the frictional plane and the corresponding maxima in heat generated cause thermoelastic instabilities (TEI). A model describing both effects covers layers of thermoelastic materials for all necessary mechanical components of the system. The set of field equations of each layer can analytically be solved by separation of constants. These solutions must fulfill the boundary conditions e.g. in the sliding plane. A stability discussion yields whether TEI appear or not. As a study a brake system is analyzed comprising two pads pressed against a rotating disk with cooling channels inside. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrically exact solution of a buckling column with asymmetric boundary conditions
Authors: Prechtl Gerhard , Schagerl Martin , Schröder Kai‐Uwe
Published: December 2012

For the symmetrically supported Euler buckling column with both ends hinged the classical stability theory yields simple trigonometric functions as buckling modes, i.e. w(x) = A sin αx. The eigenvalues α are just multiples of π. In comparison, the analysis of the asymmetrically supported Euler buckling column with one end clamped and the other end hinged is more complicated: The buckling modes are a combination of trigonometric functions in form of w(x) = A (sin αx − αx cos (αL)). The eigenvalues follow from a transcendental equation.

Applying a geometrically exact theory to the aforementioned Euler buckling problems, a similar relation in the complexity of the analyses will naturally arise. Using, e.g., the elastica model the buckling behavior of the symmetrically supported column is represented by elliptic integrals. However, the determination of the buckling behavior of the asymmetrically supported column turns out to be much more complex and elaborate. This article presents a direct comparison of the symmetrically and asymmetrically supported buckling columns regarding their analyses by means of classical stability theory and by the geometrically exact theory of the elastica. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐mechanical analysis of creep behavior in a multipass weld
Authors: Lvov Ivan
Published: December 2012

A method of evaluating creep response of the multipass weld based on the micro‐macro mechanics approach is introduced. Multipass weld microstructure that consists from columnar, coarse and fine grained zones is considered. Materials of these constituents assumed to be isotropic. Weld metal properties of inelastic behavior have general type of symmetry and are described by the anisotropic creep constitutive model.

To model the microstructure of the multipass weld metal the representative volume element (RVE) is created for CAE Abaqus. Material properties of weld metal grain type zones are taken from the experiments. Numerical tests on uniform loading of the RVE are performed. Creep material properties for equivalent weld material are found for welds with different number of passes. The symmetry type of the creep material properties of multi‐pass weld are evaluated for the equivalent weld material. As an example of macro model analysis of the welding, the creep calculation of the cylindrical shell with the welding under the uniform inner pressure is performed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plastic deformation of rough surfaces
Authors: Willner Kai , Hauer Franz
Published: December 2012

Friction forces are only transferred within the the real area of contact Areal, which is usually smaller than the apparent area of contact Ao. The maximum friction stress τfric is therefore determined by the shear limit τmax in the area of real contact and the fraction of the real area of contact (τfric = τmax (Areal/Ao)). For rough surfaces the size of Areal is governed o by the plastic deformation of the surface roughness. We present a fully elasto‐plastic halfspace contact formulation based on the work of Jacq et al. [1]. Linear elastic‐plastic material behavior is modeled based on v. Mises plasticity with isotropic hardening. The algorithm gives the residual stress as well as the full plastic deformation field due to a frictionless normal contact. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical modelling of layered composite struts
Authors: Völlmecke Christina , Müller Wolfgang H.
Published: December 2012

A numerical approach simulating the effects of interlaminar defects on the buckling stability of layered composite struts is presented. The formulation is based on the weak form of the balance of linear momentum whilst large strains are considered. First results are presented whilst comparisons are drawn to analytically derived results. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Methodology of ROMing applying POD of BWR Fuel Assemblies applied to Introductory Examples
Authors: Prill Dennis P. , Stokmaier Markus , Class Andreas G.
Published: December 2012

For high‐power low‐flow operating conditions associated with unfavorable power distribution Boiling Water Reactor (BWR) operation requires maintaining a certain distance to the stability limit given. The stability boundary with respect to small perturbations is given by analytical methods. Supplementary evaluation of non‐linear states require time‐consuming numerical integration or experimental data and strongly depend on the considered transient. Developing a self‐contained methodology for investigating the full non‐linear BWR system parameter space at low computational cost supplements established methods. The methodology of Reduced Order Modeling based on Proper Orthogonal Decomposition (ROM‐POD) is tested for this purpose and validation in terms of the Korteweg de‐Vries (KdV) equation. A transient analysis of simplified reactor physics [1] yields a low‐rank ROM and is depending on the chosen transients but not on the details. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of a stochastic friction coefficient depending on a randomly rough surface
Authors: Gaus Nicole , Proppe Carsten , Hetzler Hartmut
Published: December 2012

The goal of this contribution is to calculate the the friction coefficient for a scanned surface of a worn brake pad. The data shows that the asperities can be approximated by paraboloids which allows to calculate the contact force and area with the Hertz contact model if the deformation is elastic. The friction force is calculated with the Bowden‐Tabor approach which suggests that the friction force is the force to shear apart contacting asperities. This is considered to be the dominant friction cause in dry contact. To generate many surfaces with similar peak statistics the spectral decomposition is used. The friction coefficient and it's stochastic properties is calculated for these surfaces. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zur Interaktion von Sägedraht und Ingot
Authors: Lorenz Michael , Ams Alfons
Published: December 2012

Es wird ein mechanisches Modell zur Beschreibung des bewegten Sägedrahtes unter Einwirkung des Siliziumblocks (Ingot) vorgestellt. Mit dem Prinzip von HAMILTON wird, unter der Voraussetzung nichtlinearer Verformungskinematik sowie unter Berücksichtigung der Dehn‐ und Biegesteifigkeit des Drahtes, das Variationsproblem und die Bewegungsgleichungen hergeleitet. Die Wirkung des Ingot auf den bewegten Draht wird als Folgelast modelliert. Ausgehend vom Variationsproblem wird mit einem gemischten RITZ‐Ansatz die stationäre Lage des Drahtes für verschiedene Einflussparameter berechnet und Stabilitätsuntersuchungen durchgeführt. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of human motion in interaction with sports surface – Energetic Aspects vs. Risk of Injury
Authors: Bellanger Claudia , Hetzler Hartmut , Seemann Wolfgang
Published: December 2012

The aim in high‐performance sports activities is reaching the optimum between high efficiency and low risk of injuries during workout. This paper wants to investigate several types of human motion in interaction with a compliant ground. The influence of the surface parameters on the human metabolic cost consumption and the reaction force is analysed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Experimental Method for the Phase Controlled Frequency Response Measurement of Nonlinear Vibration Systems
Authors: Mojrzisch Sebastian , Wallaschek Jörg , Bremer Jan
Published: December 2012

Experimental determination of frequency response function of nonlinear systems is difficult when there exists more than one solution branch. Depending on the system at hand, various types of jump phenomena can be observed and in the example of the well‐known Duffing‐oscillator, it is not possible to experimentally determine the unstable solution branch if the system is excited by a harmonic force. In the present paper we investigate the Duffing‐oscillator and present a method, which allows to reformulate the equation of motion of the system with force‐excitation in the form of an equivalent self‐excited system. Considering the phase between force and response as the input variable, it is possible to evaluate the frequency of the systems vibration for any given phase shift. In the same way the corresponding response amplitude is determined. An experimental set‐up is presented, which is used to validate the performance of the method. Measurements of the backbone curve are performed and discussed on the background of theoretical predictions. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degenerate cases of stability loss of an elastic fluid‐conveying tube
Authors: Jurisits Richard , Steindl Alois
Published: December 2012

The two‐dimensional non‐linear dynamics of a liquid‐filled tube is considered. The tube is clamped at the upper end, a point mass is fixed to its free lower end and laterally it is supported by two springs. The uniform flow velocity of the fluid, the end mass, the spring constant and the vertical position of the springs are considered as the distinguished parameters of the problem. A linear stability analysis shows that the (degenerate) case of a Takens‐Bogdanov‐Hopf bifurcation exists, which is associated with a high frequency flutter movement superimposed on a low frequency flutter around a statically buckled state of the tube. We account for this degenerate case by indicating the parameter regime necessary for its occurence and and give the bifurcation diagram for the trivial equilibrium position of the tube. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamically and variationally consistent modeling of distortional hardening: application to magnesium
Authors: Shi Baodong , Mosler Jörn
Published: December 2012

To capture the complex elastoplastic response of many materials, classical isotropic and kinematic hardening alone are often not sufficient. Typical phenomena which cannot be predicted by the aforementioned hardening models include, among others, cross hardening or more generally, the distortion of the yield function. However, such phenomena do play an important role in several applications in particular, for non‐radial loading paths. Thus, they usually cannot be ignored. In the present contribution, a novel macroscopic model capturing all such effects is proposed. In contrast to most of the existing models in the literature, it is strictly derived from thermodynamical arguments. Furthermore, it is the first macroscopic model including distortional hardening which is also variationally consistent. More explicitly, all state variables follow naturally from energy minimization within advocated framework. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of microstructure in a Cosserat continuum using relaxed energies
Authors: Khan Muhammad Sabeel , Hackl Klaus
Published: December 2012

We develop a nonlinear incompressible multiphase material model in a Cosserat continuum with microstructure. The free energy of the material is enriched with an interaction potential taking into account the intergranular kinematics at the continuum scale. As a result the total energy becomes non‐convex, thus giving rise to the development of microstructural phases. To guarantee the existence of minimizers an exact quasi‐convex envelope of the corresponding energy functional is derived. As a result a three phase material energy appears, among them two of the phases are with microstructure in the translational motion (displacment field) and micromotion (microrotation field), whereas the third phase is without internal structure. The corresponding relaxed energy is then used for finding the minimizers of the two field minimization problem corresponding to a Cosserat continuum. Results from a numerical example predicting the development of microstructure in the material are presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
About the Microstructural Effects of Polycrystalline Materials and their Macroscopic Representation at Finite Deformation
Authors: Lehmann Eva , Loehnert Stefan , Wriggers Peter
Published: December 2012

In the sheet bulk metal forming field, the strict geometrical requirements of the workpieces result in a need of a precise prediction of the material behaviour. The simulation of such forming processes requires a valid material model, performing well for a huge variety of different geometrical characteristics and finite deformation.

Because of the crystalline nature of metals, anisotropies have to be taken into account. Macroscopically observable plastic deformation is traced back to dislocations within considered slip systems in the crystals causing plastic anisotropy on the microscopic and the macroscopic level. A finite crystal plasticity model is used to model polycrystalline materials in representative volume elements (RVEs) of the microstructure. A multiplicative decomposition of the deformation gradient into elastic and plastic parts is performed, as well as a volumetric‐deviatoric split of the elastic contribution. In order to circumvent singularities stemming from the linear dependency of the slip system vectors, a viscoplastic power‐law is introduced providing the evolution of the plastic slips and slip resistances. The model is validated with experimental microstructural data under deformation. The validation on the macroscopic scale is performed through the reproduction of the experimentally calculated initial yield surface. Additionally, homogenised stress‐strain curves from the microstructure build the outcome for a suitable effective material model. Through optimisation techniques, effective material parameters can be determined and compared to results from real forming processes. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of an anisotropic growth formulation to computational structural design
Authors: Waffenschmidt Tobias , Menzel Andreas
Published: December 2012

Common structural optimisation problems consist of problem‐specific objective functions which have to be minimised mathematically with respect to design and state variables taking into account particular constraints. In contrast to this, we adopt a conceptually different approach for the design of a structure which is not based on a topology‐optimisation technique. Instead, we apply a one‐dimensional energy‐driven constitutive evolution equation for the referential density–originally proposed for the simulation of remodelling effects in bones–and embed this into the micro‐sphere‐concept to end up with a three‐dimensional anisotropic growth formulation. The objective of this contribution is to investigate this approach with emphasis on its application to structural design problems by means of two three‐dimensional benchmark‐type boundary value problems. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards the simulation of Internal Traverse Grinding – from mesoscale modelling to process simulations
Authors: Holtermann Raphael , Menzel Andreas
Published: December 2012

The present work aims at the modelling and simulation of Internal Traverse Grinding of hardened 100Cr6/AISI 52100 using electro plated cBN grinding wheels. We focus on the thermomechanical behaviour resulting from the interaction of tool and workpiece in the process zone on a mesoscale.

Based on topology analyses of the grinding wheel surface, two‐dimensional single‐ and multigrain representative numerical experiments are performed to investigate the resulting load‐displacement‐behaviour as well as the specific heat generation due to friction and plastic dissipation.

A thermoelastic‐viscoplastic constitutive model is used to capture thermal softening of the material taken into account. Based on previous work, an adaptive remeshing scheme which uses a combination of error estimation and indicator methods, is applied to overcome mesh dependence. In consequence, the formulation allows to resolve the complex deformation patterns and to predict a realistic thermomechanical state of the resulting workpiece surface. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anisotropic finite strain hyperelasticity based on the multiplicative decomposition of the deformation gradient
Authors: Al‐Kinani Raad , Hartmann Stefan , Netz Torben
Published: December 2012

In this contribution a new constitutive model for transversely isotropic materials is presented. The proposed model is based on the multiplicative decomposition of the deformation gradient into one part containing the deformation only in the direction of anisotropy and another part describing the remaining deformation. This clear assignment leads to a decoupling of the stress‐state. The model is investigated analytically in view of simple tension. Moreover, an inhomogenous deformation is solved using a finite elements simulation. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zur Abtragssimulation beim Strömungsschleifen
Authors: Schmitt Joachim , Diebels Stefan
Published: December 2012

In dieser Arbeit werden zunächst für eine handelsübliche AFM‐Paste die Parameter eines nicht‐Newtonschen Stoffgesetzes experimentell in Rotationsrheometerversuchen bestimmt und die Ergebnisse an einer weiteren Versuchsreihe (Düsenauspressversuche) mit Hilfr einer FEM‐Simulation überprüft. Danach werden ein einfaches Abtragsmodell vorgestellt und die Funktionsfähigkeit dieses Modells an einem Beispiel demonstriert. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)