Bachelor-, project- and master theses

We always appreciate your interest in executing a bachelor’s, project or master’s theses at our institute. As part of our ongoing research, we are offering the following topics. Topics other than those listed here can be discussed and assigned with the employees at short notice. Please contact Prof. Sören Ehlers or Prof. Alexander Düster for further information. It is also possible to find suitable thesis topics in cooperation with out national and international partners.

Bachelor and project theses:

Application of the strain energy density method to butt-welded joints

To this day many different local fatigue assessment methods have been proposed and are still being developed. Each of them has benefits and downsides for particular problems.

The most common local fatigue assessment method in ship and offshore industry is the structural hot-spot stress approach. One of the more sophisticated methods is based on the integration of the averaged strain energy density (SED) in a small volume surrounding for example the notch at a weld toe. In different studies the accuracy of the method has proven to be eminent; however, the computational effort is still high, due to particular requirements on the finite element mesh used for calculation of the SED.

In order to improve the applicability of the method for fatigue assessment of larger structures like ships or offshore structures it is necessary to decrease the computational effort of this method and to verify its accuracy based on different scenarios. Thus, this thesis aims at comparing different approaches for SED-based assessment of butt-welded joints.

Please send an email to moritz.br(at)tuhh.de

Finite element modeling of the triaxial test

In this project, the triaxial test as one of the important characterizing tests for powder materials shall be simulated using the finite element method (FEM). This approach can help to study the behavior of discrete materials in two different ways. It may consider all particles together as a continuum and discretize it with finite elements. Here, some constitutive models like the Mohr-Coulomb or the Drucker-Prager model may be used. The other way is using the multi-particle finite element method (MPFEM) where each particle is modeled separately and discretized by finite elements. For this study, it is required to carry out a parametric study using the commercial software Ansys and prepare the corresponding macro scripts (APDL). Comparing the results of two above mentioned approaches and a scientific discussion is also expected.  

      Schematic view of the triaxial test

Interested applicants are asked to contact Dr. Amir Atrian: amir.atrian(at)tuhh.de

Simulation des Bruchverhaltens poröser Materialien mit der Diskrete-Elemente Methode

Im Rahmen des Graduiertenkollegs, Prozesse in natürlichen und technischen Partikel-Fluid-Systemen (PintPFS), werden zum Thema ”Identifikation von kontinuumsmechanischen Materialparametern granularer Materialien mit Hilfe von Partikelmethoden” Bachelor-, Projekt- und Masterarbeiten vergeben.

Der aktuelle Schwerpunkt des Projekts liegt in der Simulation und Auswertung verschiedener Experimente wie z.B. dem Oedometertest, mit deren Hilfe das Bruchverhalten von Partikeln untersucht werden kann. Die Simulationen werden mit einer Diskrete-Elemente Methode durchgeführt. Die Partikel werden dabei als Agglomeratebestehend aus Primärpatikeln und verbindenden Feststoffbrücken dargestellt. Durch das Versagen der Feststoffbrücken kann das Brechen der Partikel simuliert werden.

Weitere Informationen hier

Kontakt: sonja.kraus(at)tuhh.de

Master Theses:

Topics related to fatigue strength of 3D printed materials

Additive manufacturing as a new production process offers great advantageous for certain applications compared to classical processes; however, additively manufactured components are known to have poor surface quality after production. These surfaces can contain defects, from which fatigue cracks can be initiated. Possibilities to improve the fatigue strength included post-production methods like heat treatment or hybrid production processes (e.g. machining of the surface). In current projects the fatigue behavior of 316L specimens produced by selective laser melting and wire and arc additive manufactured are investigated. Topics for project and master thesis include:

• Fatigue strength of welded 3D printed materials
• Fatigue strength of wire and arc additive manufactured (WAAM) materials
• Hybrid additive manufacturing

Please send an email to moritz.br(at)tuhh.de

Instructor: MSc. Moritz Braun

Fatigue assessment of welded joints under consideration of notch acuity, material strength, and crack initiation behaviour

In recent years there has been a trend towards steels of higher and higher strength in various industrial sectors. In order to be able to use the advantages of greater strength constructively, high demands are placed on the quality of weld seams. The estimation of the fatigue strength according to the classification regulations of DNV GL etc. As a result, no high-strength materials are currently being considered in welded joints. Within the scope of this thesis, the fatigue strength behavior of butt weld joints shall be investigated and evaluated. For this purpose, fatigue strength evaluations are to be carried out under consideration of notch acuity, material strength, and crack initiation behaviour. The aim of this study is an estimation of the fatigue strength based on the aforementioned properties and an estimation of the constructional possibilities by the use of high-strength steels in shipbuilding.

Please send an email to moritz.br(at)tuhh.de

Instructor: MSc. Moritz Braun

Fatigue assessment of post-weld treated joints for high-speed sailing yachts

The keels of high-performance sailing yachts are increasingly made of high-strength steels with yield strengths above the usual strengths of ship structural steel. The constructions of these keels consist of both milled profiles and welded hollow chamber profiles which are often post-weld treated. However, the assessment of the fatigue strength according to the DNV GL regulations does not currently include consideration for high-strength materials in welded joints and the effect of post-weld treatment. Within the scope of this project thesis, the fatigue behaviour of high-strength steels will be investigated and evaluated. For this purpose, fatigue tests are carried out for different steel grades and production methods. Herein welded joints in as-welded state and after grinding are considered. In addition, the effect of notches in the base material due to milling of the structure will be investigated. To secure and validate the test results, the sample series should be analysed with the aid of the finite element method.

Please send an email to moritz.br(at)tuhh.de

Instructor: MSc. Moritz Braun

Investigation of temperature effect on fatigue crack growth in welded structures

The fatigue life of structures can be divided in two stages. While the crack initiation stages can occupy up to 90% of the lifetime of smooth specimen (Clark and Knott, 1975), the fatigue life of welded structures is generally propagation-dominated. Crack growth is usually influenced by temperature effects and since more ship and offshore structures are employed in arctic environments these effects need to be analysed.

Assessment of the differences between model-scale ice and sea ice and their impact on the performance of ships

Simulation or calculation methods are not yet sufficiently mature to evaluate the resistance and performance of ships in ice. Model-scale testing is the most used performance prediction method and plays a very important role in Arctic ship design. However, some of the most important properties in model-scale (bending strength, crushing strength, compressive strength and elastic modulus) differ significantly from full-scale.

The thesis work has to analyze the differences in mechanical properties between full-scale and model-scale. Furthermore, the possible impact on the performance prediction of ships is to be addressed, especially with regard to vertical ship motions.

Please send an email to Franz.vonbock@tuhh.de
Instructor: D.Sc. (Tech.) Franz von Bock und Polach

Strukturnachweise für Offshorebauwerke

Für Bauwerke der Offshorewindindustrie ist in Deutschland der BSH Standard Konstruktion anzuwenden. Der BSH Standard sieht generell eine Konstruktion nach den Eurocode-Standards vor, gängige Offshoreregelwerke können nur ergänzend zur Anwendung kommen. Aus dieser Forderung ergeben sich für die Industrie zwei Probleme: Zum einen ergeben sich aus den unterschiedlichen Regelwerken unterschiedliche Sicherheitsniveaus. Zum anderen gibt es bei Anwendung der Eurocodes immer noch offene Fragen zu offshorespezifischen Problemen, wie der Bestimmung der anzusetzenden Lasten und der Durchfüh- rung des Betriebsfestigkeitsnachweises.

Im Rahmen von ein oder zwei Masterarbeiten soll deshalb eine vergleichende Auslegung von exemplarischen Gründungsstrukturen durchgeführt werden.

Die Durchführung und Betreuung der Arbeit erfolgt im Büro der MAREVAL AG in Hamburg. Die Bearbeitung des Themas kann sofort beginnen. Bei Interesse an dem Thema bitten wir Zusendung einer aussagekräftigen Bewerbung an info@mareval.de.

Mehr Informationen zur Arbeit hier.

A comparative study of deformation and crushing behavior of particles using DEM and MPFEM

The Poraver expanded glass granules may be used as filler material in the void spaces between two walls in double hull vessels. Recent studies demonstrated that this filler material has improved crashworthiness and energy absorption of ship structures during collision.

To model discrete materials like powder, sand, soil, rock, etc., two techniques, i.e. the finite element method (FEM) and the discrete element method (DEM) are mainly used. In DEM, for each particle the equation of motion is solved, considering contact with its neighbors. On the other hand, FEM considers all particles together as a continuum and discretizes it with finite elements. Now, if each particle is modeled separately and discretized by finite elements, we have the multi-particle finite element method (MPFEM). Both DEM and MPFEM may be used for modeling of breakage and crushing behavior of Poraver granules. For DEM, an open source code is available, and for MPFEM, the commercial software Ansys may be employed. In this project, the Poraver particles are under quasi-static compressive loading, and the particles crushing behavior is investigated using these two techniques. It is also expected to have a comparative study on the theory and different aspects of each technique.

Interested applicants are asked to contact DR. Amir Atrian: amir.atrian(at)tuhh.de

Simulation des Bruchverhaltens poröser Materialien mit der Diskrete-Elemente Methode

Im Rahmen des Graduiertenkollegs, Prozesse in natürlichen und technischen Partikel-Fluid-Systemen (PintPFS), werden zum Thema ”Identifikation von kontinuumsmechanischen Materialparametern granularer Materialien mit Hilfe von Partikelmethoden” Bachelor-, Projekt- und Masterarbeiten vergeben.

Der aktuelle Schwerpunkt des Projekts liegt in der Simulation und Auswertung verschiedener Experimente wie z.B. dem Oedometertest, mit deren Hilfe das Bruchverhalten von Partikeln untersucht werden kann. Die Simulationen werden mit einer Diskrete-Elemente Methode durchgeführt. Die Partikel werden dabei als Agglomeratebestehend aus Primärpatikeln und verbindenden Feststoffbrücken dargestellt. Durch das Versagen der Feststoffbrücken kann das Brechen der Partikel simuliert werden.expected.

Weitere Informationen hier

Kontakt: sonja.kraus(at)tuhh.de

Fluid-Struktur-Interaktion

Die Interaktion von Fluid und Struktur spielt insbesondere im Schiffbau eine bedeutende Rolle, da die Belastung, Bewegung und Deformation des Schiffes ganz wesentlich von dem umgebenden Fluid beinflusst wird. Für beide Teilbereiche (Fluid und Struktur) existieren bereits problemangepasste Simulationscodes, die speziell für die jeweilige Aufgabenstellung (Fluid oder Struktur) entwickelt wurden.

Die Berechnung der Fluid-Struktur-Interaktion bedarf jedoch einer gesamtheitlichen Betrachtung des Fluids und der Struktur. Zur Simulation der Fluid-Struktur-Interaktion (FSI) wird dazu in einem partitionierten Lösungsansatz ein Fluidlöser mit einem Strukturlöser gekoppelt. Ziel der Diplomarbeit ist die Realisierung einer FSI Simulation durch die Kopplung von zwei existierenden Simulationscodes. Hierbei ist eine enge Kooperation mit Prof. M. Abdel-Maksoud, Institut für Fluiddynamik und Schiffstheorie, geplant.
Weitere Details finden sich hier.

Kontakt: Prof. A. Düster