Inst. Mechanik

67 Items

Recent Submissions
A mesoscopic approach to diffusion phenomena in mixtures

Palumbo, Nunzia ; Papenfuss, Christina ; Rogolino, Patrizia (2005)

The mesoscopic concept is applied to the theory of mixtures. The aim is to investigate the diusion phenomenon from a mesoscopic point of view. The domain of the field quantities is extended by the set of mesoscopic variables, here the velocities of the components. Balance equations on this enlarged space are the equations of motion for the mesoscopic fields. Moreover, local distribution functio...

Thermodynamical Frameworks for Higher Grade Material Theories with Internal Variables or Additional Degrees of Freedom

Papenfuss, Christina ; Forest, Samuel (2006)

The objective of the present work is to compare several thermomechanical frameworks, taking into account the influence of strain gradient, internal variables, gradient of internal variables, and temperature gradient on the constitutive behavior of materials. In particular, the restrictions by the second law of thermodynamics are derived. The method of exploitation consists of two steps: an appl...

Mesoscopic Modeling for Continua with Pores: Application in Biological Soft Tissue

Weinberg, Kerstin ; Böhme, Thomas (2008)

In this work, the damage in biological soft tissue induced by bubble cavitation is investigated. A typical medical procedure with such damaging side effects is the kidney stone fragmentation by shock-wave lithotripsy. We start with a mesoscopic continuum model that allows the consideration of microstructural information within the macroscopic balance equations. An evolution equation for the tem...

Mesoscopic Modeling for Continua with Pores: Dynamic Void Growth in Viscoplastic Materials

Weinberg, Kerstin ; Böhme, Thomas (2008)

The temporal development of arbitrarily distributed voids in a viscoplastic material under different loading regimes is investigated. For this reason, we make use of a mesoscopic continuum model extending the classical space–time domain of continuum mechanics. This extended domain requires a reformulation of the classical balance equations as well as the consideration of additional constitutive...

Heterogeneity of material structure determines the stationary surface topography and friction

Li, Qiang ; Voll, Lars ; Starcevic, Jasminka ; Popov, Valentin L. (2018-09-21)

The character of surface roughness and the force of friction in the stationary state after a sufficiently long run-in process are of key importance for numerous applications, e.g. for friction between road and tire. In the present paper, we study theoretically and experimentally the asymptotic worn state of a bi-phasic material that is arbitrarily heterogeneous in the contact plane, but homogen...

Inverse analysis of cellulose by using the energy-based method and a rotational rheometer

Abali, Bilen Emek (2018-08-12)

Biological and polymer-type materials usually show a complicated deformation behavior. This behavior can be modeled by using a nonlinear material equation; however, the determination of coefficients in such a material equation is challenging. We exploit representation theorems in continuum mechanics and construct nonlinear material equations for cellulose in an oscillatory rheometer experiment....

Theoretical and experimental investigations of the bifurcation behavior of creep groan of automotive disk brakes

Zhao, Xingwei ; Gräbner, Nils ; Wagner, Utz von (2018)

There are several low frequency vibration phenomena which can be observed in automotive disk brakes. Creep groan is one of them provoking noise and structural vibrations of the car. In contrast to other vibration phenomena like brake squeal, creep groan is caused by the stick-slip-effect. A fundamental investigation of creep groan is proposed in this paper theoretically and experimentally with ...

Application of the mode-shape expansion based on model order reduction methods to a composite structure

Peredo Fuentes, Humberto (2017)

The application of different mode-shape expansion (MSE) methods to a CFRP based on model order reduction (MOR) and component mode synthesis (CMS) methods is evaluated combining the updated stiffness parameters of the full FE model obtained with a mix-numerical experimental technique (MNET) in a previous work. The eigenvectors and eigenfrequencies of the different MSE methods obtained are compar...

Application of the Craig-Bampton model order reduction method to a composite structure: MACco, COMAC, COMAC-S and eCOMAC

Peredo Fuentes, Humberto ; Zehn, Manfred (2016)

The Craig-Bampton model order reduction (CBMOR) method based on the Rayleigh-Ritz approach was applied in a previous work to simulate dynamic behavior of a composite structure (CFRP) using the modal assurance criteria (MAC) and cross orthogonality (XOR) to validate the correlation. Different coordinate modal assurance criteria are applied to complement and verify the eigenfrequencies and eigenv...

Application of the Craig-Bampton model order reduction method to a composite structure: MAC and XOR

Peredo Fuentes, Humberto ; Zehn, Manfred (2014)

The Craig-Bampton model order reduction (CBMOR) method based on the Rayleigh-Ritz approach is applied to dynamic behavior simulation of a composite structure in order to verify the method's feasibility and accuracy. The principle of this method is to represent a coupled component model based on the mass, damping and stiffness matrices. The methodology consists of a finite element model based on...

FEM-gestützte Analyse der linear-elastischen und hyperelastischen eigengravitierenden Erde unter dem Aspekt geometrischer und physikalischer Nichtlinearitäten

Lofink, Paul (2018)

Die vorliegende Arbeit befasst sich mit der Deformation der Erde aufgrund der Eigengravitation. Es werden zunächst kontinuumstheoretische Grundlagen vorgestellt. Dabei werden mechanische und thermodynamische Gesetze erläutert. Um das System aus Feldgleichungen zu schließen, werden nach der Methode von Coleman-Noll thermodynamisch-konsistente Materialgesetze hergeleitet. Das Eigengravitationsp...

Theoretical and experimental investigations of creep groan in automotive disk brakes

Zhao, Xingwei (2018)

Due to the increasing comfort claims of customers, the study on low frequency creep groan has been receiving increasing attention currently. This thesis forces on the study of the fundamental mechanism of creep groan theoretically and experimentally. In order to understand creep groan step by step, the design of test rigs concentrating on creep groan are presented. A test rig with an idealized...

Model reduction of components and assemblies made of composite materials as part of complex technical systems to simulate the overall dynamic behaviour

Peredo Fuentes, Humberto (2017)

The composite components and model order reduction (MOR) methods are widely used to improve the weight/strength ratio and the computational time respectively in different areas of the industry. The objective of this research is to evaluate the dynamic behaviour applying a MOR method in a composite component assembly. A new mixed numerical-experimental technique (MNET) is developed to obtain acc...

Neue MKS-FEM-Methode zur direkten Integration geometrischer und/oder materieller Nichtlinearitäten in die Simulation deformierbarer Mehrkörpersysteme

Nguyen, Viet Anh (2017)

Die vorliegende Arbeit präsentiert neue Möglichkeiten zur effizienten Behandlung geometrisch- und/oder physikalisch-nichtlinearer Probleme in der Dynamik deformierbarer Mehrkörpersystemen (MKS). Dabei werden beliebig große Starrkörperrotationen und nichtlineares Materialverhalten der Komponenten direkt in das Bewegungsgleichungssystem des Mehrkörpersystems einbezogen. Keine Co-Simulations- oder...

An analytical framework for the structural stability analysis of damageable structures and its application to delaminated composites

Köllner, Anton (2017)

In the current work, a novel analytical framework is developed which extends the general elastic stability theory to certain non-conservative deformation processes for which an extended total potential energy can be derived. The extended total potential energy constitutes the governing functional for the non-conservative deformation processes. The mechanical systems considered are described by ...

Coupling of continuum mechanics and electrodynamics

Reich, Felix Alexander (2017)

In the literature, many models of electromagnetic momentum are proposed. Each model implies a form of the electromagnetic force density, which acts as a source in the mechanical momentum balance. The debate as to which model of the electromagnetic force is "correct" for arbitrary materials and processes is ongoing. Most authors argue in favor or against specific models by virtue of thought expe...

Diffusionsphänomene beim Löten mit Nickelbasisloten

Stahn, Oliver (2017)

Beim Hochtemperaturlöten mit Nickelbasisloten besteht seit langem das Problem der Bildung spröder Phasen in der Lötnaht. Dieses wurde bisher nur in wenigen Einzelfällen gelöst. Ziel dieser Arbeit ist es die Prozessführung während des Lötens so zu wählen, dass sich keine spröden Phasen bilden können. Dies resultiert in einer signifikanten Steigerung der Verbindungsqualität und der Gebrauchseigen...

Dynamical modelling of hydraulic excavator considered as a multibody system

Mitrev, Rosen ; Janošević, Dragoslav ; Marinković, Dragan (2017)

This paper considers the development of a plane multibody mechanical model of a hydraulic excavator simultaneously containing an open kinematic chain and closed loops. The Lagrange multiplier technique is used for modelling of the constrained mechanical systems. This approach is used for working out the dynamic equations of excavator motion in the case of performing transportation and digging o...

Beschreibung des Reaktionsablaufs energetischer Materialien bei Laserbestrahlung

Lück, Martin (2017)

Die Untersuchung der Wirkung intensiver Laserstrahlung auf energetische Materialien ist ein Thema mit großer Relevanz für die Sicherheitsforschung und findet Anwendung bei der Entwicklung neuartiger Verfahren zur sicheren Entschärfung von Sprengsätzen. Die dabei auftretenden Prozesse konnten in der Vergangenheit noch nicht adäquat beschrieben werden und sind Gegenstand der vorliegenden Arbeit. ...

A novel excitation method for pyroshock simulation

Houshmand, Behnam ; Lacher, Alexander ; Juengel, Níkolas ; Prasol, Lukas ; Wagner, Utz von ; Uhlmann, Eckart (2016)

Pyroshocks are structural responses to transient excitation caused by the essential use of pyrotechnic devices in aerospace applications. In order to avoid damage in aerospace structures due to pyroshocks, tests are performed on earth prior to launching space modules. In these tests, explosive loads are often replaced by alternative excitation methods such as hammer pendulums or shakers simulat...