Inst. Mechanik

81 Items

Recent Submissions
Effect of elastic grading on fretting wear

Willert, Emanuel ; Dmitriev, Andrey I. ; Psakhie, Sergey G. ; Popov, Valentin L. (2019-05-24)

We consider fretting wear in elastic frictional contact under influence of oscillations of small amplitude and investigate the question, how wear damage can be influenced by the introduction of material gradients. To achieve a general understanding we restrict our consideration to media with a power-law dependency of the elastic modulus on depth. In this case, a complete analytical solution can...

Numerical study of the hydraulic excavator overturning stability during performing lifting operations

Mitrev, Rosen ; Marinković, Dragan (2019-05-02)

This article presents a numerical study of the stability of a hydraulic excavator during performing lifting operations. A planar dynamic model is developed with six degrees of freedom, which considers the base body elastic connection with the terrain, the front digging manipulator links, and the presence of the freely suspended payload. Differential equations describing the excavator dynamic be...

Handbook of contact mechanics

Popov, Valentin L. ; Heß, Markus ; Willert, Emanuel (2019-04)

This open access book contains a structured collection of complete solutions of all significant axially symmetric contact problems. It provides solutions for classical profiles such as the sphere, cone or flat cylindrical punch as well as a multitude of other technically relevant shapes, e.g. the truncated cone, the worn sphere, rough profiles, hollow cylinders, etc. Normal, tangential and tors...

Numerical simulation and parametric investigation of the mechanical properties of fabric nap core sandwich

Ha, Giap Xuan (2019)

This research deals with the finite element (FE) simulation and the validation of FE models for a new type of sandwich-structured composite, the so-called nap-core sandwich. The nap-core is made of a two-dimensional knitted fabric impregnated with a thermosetting resin, which underwent deep drawing and curing processes to adopt a permanent three-dimensional shape. The nap-core can be considered...

Adhesive Strength of Contacts of Rough Spheres

Li, Qiang ; Pohrt, Roman ; Popov, Valentin L. (2019-03-26)

The adhesive contact between a parabolic indenter with superimposed roughness and an elastic half space is studied in the JKR-limit (infinitely small range of action of adhesive forces) using the boundary element method with mesh-dependent detachment criterion suggested in 2015. Three types of superimposed roughness are considered: one- and two-dimensional waviness and randomly rough roughness....

Drug Delivery From Polymer-Based Nanopharmaceuticals—An Experimental Study Complemented by Simulations of Selected Diffusion Processes

Macha, Innocent J. ; Ben-Nissan, Besim ; Vilchevskaya, Elena N. ; Morozova, Anna S. ; Abali, Bilen Emek ; Müller, Wolfgang H. ; Rickert, Wilhelm (2019-03-08)

The success of medical therapy depends on the correct amount and the appropriate delivery of the required drugs for treatment. By using biodegradable polymers a drug delivery over a time span of weeks or even months is made possible. This opens up a variety of strategies for better medication. The drug is embedded in a biodegradable polymer (the “carrier”) and injected in a particular position ...

Effect of vibrations on friction in the context of brake squeal

Nguyen, Thai Minh Tuan (2019)

Brake squeal is a case of friction-induced vibration that has not been fully understood yet due to difficulties in both experimental and theoretical approaches. Both approaches are considered in this research in order to contribute knowledge to this topic. Following the idea of the already existing Dynamic Compression Test Rig (DCTR), which shows that the dynamic stiffness of a pad specimen de...

Feuerwiderstand von unversteiften und versteiften CFK Schalenstrukturen und der Einfluss von integrierten Flammschutzlagen

Timme, Sebastian (2019)

Carbon fiber reinforced polymers (CFRP) are progressively used as lightweight materials in primary, load bearing structures for aircraft, ships and trains. However, their mechanical performance under direct flame impingement is identified to be a limiting factor decreasing their weight-saving potential. The fibers often behave inert with respect to pyrolysis while the mechanical properties of t...

Design, analysis, and control of a cable-driven parallel platform with a pneumatic muscle active support

Zhao, Xingwei ; Zi, Bin ; Qian, Lu (2017)

The neck is an important part of the body that connects the head to the torso, supporting the weight and generating the movement of the head. In this paper, a cable-driven parallel platform with a pneumatic muscle active support (CPPPMS) is presented for imitating human necks, where cable actuators imitate neck muscles and a pneumatic muscle actuator imitates spinal muscles, respectively. Analy...

Non-linear investigation of an asymmetric disk brake model

Spelsberg-Korspeter, G. ; Hochlenert, Daniel ; Hagedorn, P. (2011)

Among design engineers, it is known that breaking symmetries of a brake rotor can help to prevent squeal. From a modelling point of view, in the literature brake squeal is almost exclusively treated using models with a symmetric brake rotor, which are capable of explaining the excitation mechanism but yield no insight into the relation between rotor asymmetry and stability. In previous work, it...

A mathematical model in three-dimensional piezoelectric continuum to predict non-linear responses of piezoceramic materials

Samal, M. K. ; Seshu, P. ; Wagner, Utz von ; Hagedorn, P. ; Dutta, B. K. ; Kushwaha, H. S. (2008)

It has been experimentally observed that the piezoceramic materials exhibit different types of non-linearities under different combinations of electrical and mechanical fields. When excited near resonance in the presence of weak electric fields, they exhibit typical non-linearities similar to a Duffing oscillator such as jump phenomena and the presence of superharmonics in the response spectra....

Aspects of Modeling Piezoelectric Active Thin-walled Structures

Marinković, Dragan ; Köppe, Heinz ; Gabbert, Ulrich (2009)

The objective of this article is to reconsider some important aspects of modeling piezoelectric active thin-walled structures. Hence, it is dealt here with thin-walled laminated structures involving piezoelectric patches. A recently developed shell type finite element is used for the purpose. The first aspect is adequate modeling of electric field within the piezoelectric patches polarized in t...

Grundlagen und Anwendbarkeit von Magneto-Adaptronischen Transducern (MATs) an ferromagnetischen Materialien zur aktiven Schall- und Schwingungsminderung

Glugla, Markus (2018)

Die magnetischen Eigenschaften von ferromagnetischen Materialien zeigen zwei Effekte, den Joule- und den Villari-Effekt. Der Joule-Effekt, auch bekannt als magnetostriktiver Effekt, beschreibt die Längen- und Volumenänderung eines ferromagnetischen Materials unter Einwirkung eines magnetischen Felds. Der inverse Vorgang, die Änderung des Magnetfelds eines ferromagnetischen Materials unter Einwi...

Zur Modellbildung und Analyse von bistabilen Energy-Harvesting-Systemen

Lentz, Lukas (2018)

The subject of the thesis is the modeling and the analysis of a bistable energy-harvesting system. The energy-harvesting system consists of a bimorph beam that is made from a ferromagnetic substructure and piezoceramic layers on top. The beam is attached to a rigid frame which can be attached to a host structure. On the frame two permanent magnets are mounted in such a way, that the restoring f...

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....