bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial impedance control of two cooperative industrial manipulators
Authors: Kaserer Dominik , Gattringer Hubert , Müller Andreas 
Published: October 2016

AbstractNowadays robotic manipulators are considered to perform a wide range of tasks. Since robotic systems consisting of multiple manipulators are capable of handling a variety of tasks that cannot be executed by single manipulators, cooperation of multiple manipulators is becoming increasingly interesting in particular for industrial applications. The interaction with other manipulators, respectively the environment, requires an extension of the conventional position control in order to achieve a desired compliance, and thus to limit the interaction wrench so to avoid damaging the involved objects. In this contribution the cooperation of two industrial manipulators, a Stäubli RX130L (6‐DOF) and a Stäubli TX90L mounted on a linear axis (constituting a redundant 7‐DOF manipulator), is addressed applying an impedance control scheme. The manipulation task is to grasp an object with both manipulators and to follow a prescribed trajectory by simultaneously limiting the contact forces between the manipulators and the object and ensuring a compliant behavior towards the environment. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact Simulations Using a Quasi‐Static Contact Submodel in Reduced Flexible Multibody Systems
Authors: Tschigg Stephan , Seifried Robert 
Published: October 2016

AbstractFor an efficient approximation of the local and global deformation behavior, impact simulations using reduced elastic models can be performed. Modally reduced models require a large number of eigenmodes to capture all local deformation effects. For this reason, the use of static shape functions in the contact area is recommended. However, due to high eigenfrequencies introduced by the static shape functions, the time integration is no longer efficient. Hence, this work presents an approach to reduce the influence of these high frequencies on the time integration. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Prediction Model for State Observation and Model Predictive Control of Biped Robots
Authors: Wittmann Robert , Rixen Daniel 
Published: October 2016

AbstractBiped walking robots present a class of mechanical systems with many different challenges such as nonlinear multi‐body dynamics, a large number of degrees of freedom and unilateral contacts. The latter impose constraints for physically feasible motions and in stabilization methods as the robot can only interact due to pressure forces with the environment. This limitation can cause the system to fall under unknown disturbances such as pushing or uneven terrain. In order to face such problems, an accurate and fast model of the robot to observe the current state and predict the state evolution into the future has to be used. This work presents a nonlinear prediction model with two passive degrees of freedom (dof), point masses and compliant unilateral contacts. We show that the model is applicable for real‐time model predictive optimization of the robot's motion. Experiments on the biped robot LOLA [1] underline the effectiveness of the proposed model to increase the system's long term stability under large unknown disturbances. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of confocal microscopy image data of Physcomitrella chloroplasts to reveal adaptation principles leading to structural stability at the nanoscale
Authors: Asgharzadeh Pouyan , Özdemir Bugra , Müller Stefanie J. , Reski Ralf , Röhrle Oliver 
Published: October 2016

AbstractProteins of the FtsZ (filamentous temperature‐sensitive Z) family establish complex polymeric spatial patterns in plastids of the moss Physcomitrella patens. These structures represent a "plastoskeleton" that might contribute to plastid shape and stability. The aim of this work is to develop computer models of FtsZ network connectivity and dynamics. These computer models are developed from green fluorescent protein (GFP) images obtained by Prof. Reski's Plant Biotechnology group at the University of Freiburg by means of laser scanning confocal microscopy. Subsequently, structural reconstruction techniques based on cellular automata algorithm are applied on the raw image data to compensate for any information that is lost in the process of imaging. Segmentation of the processed data will result in the computer model of the targeted structures, which are used for further analysis. Model generation and experimental testing in the moss system is conducted in an iterative process with the aim of both forward and reverse biomimetics. A developed image processing algorithm with the aim of quantification of structural characteristics is utilized to extract structural features of the FtsZ network in Physcomitrella enabling us a statistical analysis on the extracted data. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A novel model to describe the intervertebral disc mechanical response
Authors: Azarnoosh Marzieh , Heider Yousef , Stoffel Marcus , Markert Bernd 
Published: October 2016

AbstractThe main objective of the present work is the development of a simplified, efficient and easy‐to‐implement single‐phase material model, which is able to describe the essential effects characterising the behaviour of multi‐phase saturated materials, such as of intervertebral discs (IVDs). The presented new model mainly focuses on extending a viscoelastic material model in order to not only take the mechanical behaviour of the solid part into account, but also the fluid‐flow‐dependent behaviour of the material. By applying this model, the complexity and constitutive parameters are reduced, the implementation is more convenient and the experimental investigations can be better supported in comparison to multi‐phase material models of IVDs. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale modelling of skeletal muscle tissue by incorporating microstructural effects
Authors: Bleiler Christian , Ponte Castañeda Pedro , Röhrle Oliver 
Published: October 2016

AbstractThe macroscopic mechanical response of skeletal muscle tissue is mainly influenced by the properties and arrangement of microstructural elements, such as, for example, sarcomeres and connective tissue. Like for many biological materials, the mechanical properties of skeletal muscle tissue can vary quite significantly between different specimens like, for example, different persons or muscle types. Current state‐of‐the‐art continuum‐mechanical muscle models often lack the ability to take into account such variations in a natural way. Further, phenomenological constitutive laws face the challenge that appropriate material parameter sets need to be found for each tissue variation.Thus, the present work aims to identify the microstructural features and parameters governing the overall mechanical response and to incorporate them into a macroscopic material model by applying suitable homogenisation methods. The motivation hereby is that the estimation of material parameters for microstructures, such as collagen fibres, can be done in a more reliable and general way and that fluctuations between specimens are included by, for example, adapting the alignment of the collagen fibres inside the muscle. Moreover, instead of computationally expensive homogenisation methods like FE2, this work proceeds from well‐founded analytical homogenisation techniques in order to keep the model as simple as possible. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The investigation of femoroacetabular impingement using motion capture, FEM and multi‐body simulations
Authors: Cichon Robert , Raab Dominik , Hewera Simon , Lazik‐Palm Andrea , Theysohn Jens , Landgraeber Stefan , Kowalczyk Wojciech 
Published: October 2016

AbstractIn recent years, femoroacetabular impingement (FAI) has become increasingly common. As published in the literature, FAI is caused by an unphysiological contact between the proximal femur and the acetabular rim, which may lead to pain, limitation of movement, and damage of cartilage. In this paper, patient‐specific finite element simulations of the movement of the hip based on gait motion data and MRI segmentation were conducted to check stresses of the acetabulum and femur, and additionally whether a bony contact is present or not. The study's findings show no bony contact between femur and acetabulum, which may lead to the hypothesis that the labrum and its deformation and/or the articular capsule are involved in the mechanism of FAI. In order to verify this hypothesis more simulations including labrum and capsule must be performed. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Failure of adhesive bonds between proteoglycans causes viscoelasticity of soft tissues
Authors: Hillgärtner Markus , Linka Kevin , Itskov Mikhail 
Published: October 2016

AbstractSoft tissues can be considered as a composite material where a matrix (ground substance) is reinforced by collagen fibers. These fibers consist of fibrils, which are connected by proteoglycan (PG) bridges. The time‐dependent properties of soft tissues appear to be mainly caused by proteoglycans [3]. This contribution presents a modeling approach where damage in the PG bridges arises due to the failure of the covalent bonds between two proteoglycans. The breakage of covalent bonds is reversible over time and incorporated using a healing formulation. A high PG density supports interfibrillar sliding and hence leads to a lower fibril stretch [8]. Accordingly, the damage propagation in PG bridges leads to a higher stretch in the fibrils and therefore to a stiffer material response. The strain energy of the fibrils is based on the response of single tropocollagen molecules and takes both, an entropic and an energetic regime into account [5]. Finally, the model is compared against experimental data available in the literature. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical and experimental investigation of bone fracture in the human proximal femur
Authors: Hülsmann Angelina , Stoffel Marcus , Heider Yousef , Knobe Matthias , Markert Bernd 
Published: October 2016

AbstractProximal femur fractures are very common injuries especially among older patients. Although, there are various alternatives and improvements in implant design and operating techniques, the treatment still represents a big medical challenge. Therefore, the understanding of crack initiation and propagation in the proximal femur is of great interest. The objective of this work is to present a simplified phenomenological model that is able to predict crack initiation and propagation in the proximal femur. This will be simulated by using a phase‐field modelling (PFM) approach. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational and experimental analysis of wound healing processes
Authors: Liang Jinghu , Bolea Albero Antonio , Füller Jendrik , Müller‐Goymann Christel , Böl Markus 
Published: October 2016

AbstractWound healing in epidermis is a complex physiological process in which new cells are created to repair the damaged tissue. The timing of cell division and growth mechanisms in wound healing are influenced by biological, mechanical and medical factors. In this work we aim to provide a numerical model based on the observations realised in in‐vitro experiments for the understanding of wound healing. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fatigue damage modeling of fibrous soft tissues
Authors: Linka Kevin , Itskov Mikhail 
Published: October 2016

AbstractUltimate tendon failure is often caused by fatigue loading. Recent interventions revealed a three‐phase progression of histological changes during cyclic loading of the tendon. It starts from localized kinked fiber deformations, continues with additional fiber delaminations and finally leads to fiber angulations and discontinuities [5, 6]. In the present contribution, we propose a physically motivated constitutive model able to describe fatigue evolution in tendon subject to cyclic loading. The damage of the collagen fibers is elucidated by a successive permanent opening of tropocollagen molecules [7], which represent the basic building blocks of collagen fibrils. The fibril strain increase is triggered by a time‐force depending rupture of glycosaminoglycan sidechains of adjacent collagen fibrils. The so obtained model is in line with recent experimental findings available in literature. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An examination of tissue engineered scaffolds in a bioreactor
Authors: Niedermeyer Angela , Zhou Bei , Dursun Gözde , Stoffel Marcus , Artmann Aysegül , Markert Bernd 
Published: October 2016

AbstractReplacement tissues, designed to fill in articular cartilage defects, should exhibit the same properties as the native material. The aim of this study is to foster the understanding of, firstly, the mechanical behavior of the material itself and, secondly, the influence of cultivation parameters on cell seeded implants as well as on cell migration into acellular implants. In this study, acellular cartilage replacement material is theoretically, numerically and experimentally investigated regarding its viscoelastic properties, where a phenomenological model for practical applications is developed. Furthermore, remodeling and cell migration are investigated. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multi‐component modelling and simulation of metastases proliferation within brain tissue
Authors: Schröder Patrick , Wagner Arndt , Ehlers Wolfgang 
Published: October 2016

AbstractOriginated from a lung tumour, cancer cells can spread via the blood‐vessel system, travel to the cerebrum and may pass the blood‐brain barrier. The extravasation is followed by migration, and the formation of micrometastases. Further proliferation causes interveined metastases. A pressure‐driven infusion of a therapeutic solution counteracts the disturbance by the metastases within the brain. These processes are described with a continuum‐mechanical model based on the Theory of Porous Media. Numerical applications demonstrate the feasibility of the model and include multicellular‐tumour spheroid experiments in the macroscopic simulation of metastases growth and atrophy. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On an electrical‐chemical‐mechanical approach for modelling smooth muscle excitation in bladder tissue
Authors: Seydewitz Robert , Böl Markus 
Published: October 2016

AbstractThe urinary bladder is characterised by its ability to withstand high deformations under harsh chemical conditions. Occurring irregularities in the bladder wall disturb the correct functioning during storage and release. In order to support the development of effective therapeutic treatments for dysfunctional urinary bladder a theoretical model was developed. Accounting for different pathways of smooth muscle activation the proposed model is based on a coupled electrical‐chemical‐mechanical approach. Finally, the model is implemented in the finite‐element framework to consider complex geometries and boundary conditions. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of active muscle contraction on whiplash injury
Authors: Sharma Nisha N. , Carmai Julaluk , Koetniyom Saiprasit , Markert Bernd 
Published: October 2016

AbstractThe objective of this work is to develop a finite element model of active human skeletal muscle, which can mimic its contraction behaviour. The model is then used to analyse the effects of active muscle contraction into occupant kinematics and injuries during rear‐end collision. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bi‐phasic theory vs. volumetric viscoelasticity for modelling the behaviour of thin collagenous membranes
Authors: Stracuzzi Alberto , Ehret Alexander E. 
Published: October 2016

AbstractA relation is established between a recently proposed single‐phase model for human amnion [1], in which an internal state variable accounts for viscoelastic volume changes due to fluid outflow, and an explicitly bi‐phasic representation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional reconstruction of M. gastrocnemius contraction
Authors: Weichert Christine , Leichsenring Kay , Ernst Michael , Wick Carolin , Siebert Tobias , Blickhan Reinhard , Böl Markus 
Published: October 2016

AbstractThere exist many different approaches investigating the contraction mechanisms of skeletal muscles. Thereby, the mechanical behavior, such as force generation in association with kinematic and microstructure, play an important role in modeling of muscle behavior. Besides the mechanical behaviour, the validation of muscle models requires the geometrical environment, too. The geometry of a muscle can be divided into macrostructure, existing of aponeurosis‐tendon‐complex (ATC) and muscle tissue (MT), as well as the fascicle architecture, representing the microstructure of the MT.In this study, the macrostructure of the isolated M. gastrocnemius was observed during isometric contraction by using three‐dimensional optical measurement systems in combination with mechanical measurement techniques. The surface deformation was reconstructed at specific force and length relationships and further the muscle tissue, aponeurosis, and tendon were distinguished, building up a macroscopic geometrical dataset. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical investigation of tendons and tendon cells
Authors: Willenberg Wolfgang , Azarnoosh Marzieh , Stoffel Marcus , Markert Bernd 
Published: October 2016

AbstractTendon injuries are a common problem in medicine. While healthy tendons do not rupture, tendon injuries are mostly accompanied by pathological changes and microruptures. Unfortunately, still less is known about the underlying processes. Thus, in the present study, we introduce artificial damages into native tendon tissue and investigate its mechanical behaviour experimentally. In the second part of this study, we propose a theoretical model for predicting the mechanical behaviour of the damaged tendon and present its validity. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A regularized damage‐plasticity model: micromorphic formulation and numerical aspects
Authors: Brepols Tim , Wulfinghoff Stephan , Reese Stefanie 
Published: October 2016

AbstractA gradient‐extended damage‐plasticity model is discussed which is based on a micromorphic approach according to Forest [1]. Damage and plasticity are treated as independent but strongly coupled dissipative phenomena by considering separate yield and damage loading functions to describe the onset of plastic flow and / or damage evolution. A numerical benchmark test conducted in the study reveals that the model is able to essentially cure the well‐known mesh‐dependence issue which is known from finite element simulations involving conventional (i. e. ‘local’) damage material models. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A microcrack‐based continuum damage model with application towards refractories
Authors: Gundlach Janto , Henneberg Dimitri , Ricoeur Andreas 
Published: October 2016

AbstractThe present work discusses numerical results of damage evolution due to thermoshock processes at refractory ceramics. Damage patterns have been generated using a two‐scale approach for brittle materials, implemented into a finite element framework. For this purpose, a cell model has been employed, incorporating cracks on a microscopic level. The impact of these discontinuities on macroscopic material properties and damage evolution is determined with the help of analytical homogenization techniques. Finally, the potential of the numerical tool is demonstrated by means of refractory bricks, being imposed by thermomechanical loading. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical approach to simulate printed electronics on fiber reinforced composites
Authors: Heinrich Felix , Lammering Rolf 
Published: October 2016

AbstractPrinted conductive paths can transmit electrical information and form an alternative to conventional wiring. In lightweight applications, where the reduction of weight is crucial, printed conductive paths and electronics could help to diminish the total mass of the structure. A possible application in aeronautics is Structural Health Monitoring (SHM) ‐ a collective term describing the structural integration of electronics that serve as a central nervous system to detect damages. As the electronics cannot only be printed on surfaces but also in between the layers of CFRP materials, it is currently under investigation whether the electronics favor delamination. To describe the electronics‐CFRP interface failure numerically, a suitable approach for a finite element analysis shall be found. Based on a homogenized and simplified description of the interface, different numerical approaches are presented and advantages and disadvantages are considered. The most promising approach is discussed in greater detail and first numerical simulations are shown. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of singularity exponents in 3D elasticity problems using enriched base functions in the Scaled Boundary Finite Element Method
Authors: Hell Sascha , Becker Wilfried 
Published: October 2016

AbstractThe SBFEM is employed for the extraction of 3D stress singularity exponents and their associated deformation modes. It makes use of a separation of variables approach, which is substituted into the virtual work equation so that only parts of the boundary need to be discretized while the 3D boundary value problem is considered analytically in a scaling variable. The enrichment of the standard separation of variables representation for the displacements with a decomposition of the analytical crack displacement field yields a substantial improvement of the method's accuracy and convergence properties. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A combined molecular dynamics‐phase‐field modelling approach to fracture
Authors: Patil Sandeep P. , Heider Yousef , Hernandez Padilla Carlos Alberto , Cruz‐Chú Eduardo , Markert Bernd 
Published: October 2016

AbstractIn order to better understand and ease the determination of material and model parameters required for the macroscopic modelling of brittle fracture, a bottom‐up comparative study between molecular dynamics (MD) simulations and the continuum phase‐field modelling (PFM) is carried out. In particular, based on the MD simulations of fracture of a highly brittle material, a number of PFM parameters such as the width of the transition zone between the damaged and the undamaged material, the crack resistance and the elasticity modulus are estimated. This study opens the door for an efficient way for multi‐scale modelling of fracture. To illustrate this approach, a comparative two‐dimensional numerical initial‐boundary‐value problem (IBVP) for the highly brittle aragonite (CaCO3) is presented. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)