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 offing the following topics:

Bachelor and project theses:

Topics other than those listed here can be discussed and assigned with the employees at short notice.

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.

Die mittragende Breite gekrümmter Gurte – ein Vergleich

Es ist eine bekannte Tatsache, dass gekrümmte Gurtungen eine sog. mittragende Breite (MB) besitzen, die von der Krümmung des Gurtes abhängt. Die praktische Anwendung auf gekrümmte Spanten (UBoote) oder Kimmaussteifungen und Rahmenträgern erfordert daher eine entsprechende Berücksichtigung. Meist werden diese MB in Abhängigkeit einer dimensionslosen Kennzahl

anschaulich dargestellt.

Master Theses:

Topics other than those listed here can be discussed and assigned with the employees at short notice.

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

Fatigue testing of additive manufactured specimen made from AISI 316L

Powder bed fusion based additively manufactured components are known to have poor surface quality after production. These surfaces can contain defects, from which fatigue cracks can be initiated. However, the fatigue strength can be significantly increased by post-production methods like heat treatment or machining of the surface. In this work the notched fatigue behavior of AISI 316L specimens produced by selective laser melting are investigated. It is well known that the fatigue strength of notched components consist of crack initiation and propagation depending on different factors like defects and general shape of the notch. So far the focus of such tests was the interaction of surface defects and fatigue crack initiation from those defects. In order to overcome this problem, three different geometries are tested, with different amount of notch acuities.

In this study different fatigue assessment methods for notched structures are applied to validate the data. Hence, this project is concerned with the investigation of the applicability of fatigue assessment methods for AM parts of AISI 316L. For this purpose, finite element simulations will be applied.

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.

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.

Parallelisierung von FEM Simulationen mit Hilfe von OpenMP

Die im Bauingenieurwesen, Maschinenbau und Schiffbau anzutreffende Komplexität der strukturmechanischen Problemstellungen (Größe der Modelle, Nichtlinearitäten, Dynamik, Fluid-Struktur Interaktion) stellt sehr hohe Anforderungen an die Simulation. Um dieser Problematik entgegenzuwirken, soll die aktuelle Entwicklung der Hardwarearchitektur genutzt werden.

Simulation des superplastischen Umformens mit Hilfe der FEM

Mit Superplastizität wird die Eigenschaft von metallischen Legierungen und keramischen Werkstoffen bezeichnet, eine plastische Formänderung durch Korngrenzengleiten anstatt von Wanderung von Versetzungen zu erzielen. Dabei sind Formänderungen von weit über 200% ohne Bruch erreichbar.

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.