Public defence in Mechanical Engineering, M.Sc. Federica Mancini

Enhancing the structural stress assessment of distorted lightweight ship deck structures 

Technological advancement and modernization in cruise shipbuilding have driven a continuous growth in ship size and design complexity. The need for lightweight design solutions becomes ever more critical to ensure the structural integrity and energy efficiency of these massive structures. Among several weight-saving strategies, reducing the thickness of plates composing the ship superstructure decks appears achievable, sustainable, and economically feasible. 

Nonetheless, thin plates are susceptible to complex welding-induced distortions, generating stress concentrations that are detrimental to the fatigue performance of the overall structure. Given that the effect of complex distortions on thin plates is not entirely considered by ship design rules, their structural assessment requires costly numerical analyses based on an accurate geometry modelling from full-field scanning of the welded plates. 

In this regard, this dissertation proposes computationally efficient structural stress assessment approaches for distorted thin plates. The study utilises full-scale thin decks panels from actual shipyard production. The effect of the distortion is studied under tension, simulating the effect of hull girder bending on the superstructure decks. A 3D geometrically non-linear finite element analysis of the panels is validated experimentally and considered as reference model to perform a scale reduction from 3D to 2D and 1D numerical and analytical models. Within the elastic regime, the von Kármán kinematic assumption of small displacements and moderate rotations is assumed. While showing modelling simplifications, and thus computational savings, for the structural stress assessment of distorted thin plates, the scale reduction gradually leads to the adaptation of an Euler-Bernoulli beam model with a simple curvature to the butt-welded area between thin plates in stiffened panels.

Doctoral Student: Federica Mancini

Opponent: Prof. Grzegorz Glinka, University of Waterloo, Canada

Custos: Prof. Heikki Remes, Aalto University School of Engineering, Department of Mechanical Engineering

The public defense will be organized in Lecture Hall 216, Otakaari 4

The thesis is publicly displayed 10 days prior to the defense in the publication archive Aaltodoc of Aalto University. 

Contact information of doctoral student:

Doctoral theses in the School of Engineering: https://aaltodoc.aalto.fi/handle/123456789/49