Influence of weld toe radius and steel grade on the fatigue life of fillet welds analysed by a strain based approach

Nowadays the marine industry plays an important role in our everyday life, offering a cost effective way for international freight transfer. From a financial point of view the more cargo can be transferred, the better. For a vessel with a set dimensions this can be achieved by increasing the deadweight, hence decreasing the lightweight. To that end, there is an increasing trend of application of HSS material, thin plate structures or both. Key challenges with these new structure is the consideration of their fatigue strengths. The Thesis project deals with the fatigue life of fully penetrated fillet welds and the effects of the weld toe radius in HSS and LSS. A localised strain based approach was used for the fatigue strength assessment. This approach applies a step by step discrete crack growth simulation for the total fatigue damage process (crack initiation and propagation) within the LCF (Low Cycle Fatigue) and HCF (High Cycle Fatigue) range, respectively. The model considers the effects of the microstructure, i.e. hardness and grain size for the two material, and the toe radius (R= 1 mm and 0.01 mm). Using Abaqus, the FEM analysis was carried out on a simplified parametric model of the fillet welds created with Matlab. The resulting stress and strain values were averaged using a characteristic length of the material, and the summation of the cycles, estimated by the Coffin-Manson relation for each discrete step, gave the overall fatigue life of the welded structure. The predicted fatigue strength and the shape of the S-N curve for both materials are in line with expectations. However, due to the material model used, where the strain vs life curves of the two materials differ significantly in the LCF range but seem to be similar at HCF one, the resulting S-N curves differ. The smooth-weld, R= 1 mm without any initial cracks seem to have a higher FAT class for both materials, whereas the weld with R= 0.01 mm gave a lower FAT class than the IIW recommended values. Also, the long crack propagation rate is reasonably in line with the recommendations for fillet welds. The differences of the short crack initiation and propagation period are significant for the two materials, whereas the long crack propagation and final fracture showed fairly similar behaviour. The initiation period in the presence of a larger toe radius, R= 1 mm lasts longer and is more dominant for the HSS material than for the LSS material. Hence, for this geometry, the HSS material could offer a better fatigue resistance. On the contrary, a smaller toe radius, R= 0.01 mm, or the presence of initial cracks of the size of 0.1 or 0.2 mm, seems to significantly lower the fatigue strength more for the HSS, than for the LSS weldments. This result shows the high dependency on the geometry, related to the actual material and implies that, due to the higher notch sensitivity of HSS, the fatigue strength will be lower for the R= 0.01 mm case than for the R = 1 mm. This tendency is not prominent in the LSS material

A román állam területi kialakulásának története IV. Nagy-Románia születése 1918-1920

European states are of various ages. The formation of the statehood of some of them took place in the Middle-Ages, and they have existed in dynastic relations, though in different ways, ever since. Others are young states which have become independent statehoods in the 19th and 20th centuries, either by breaking away from earlier states or by transforming their dependent and partial statehood in opposition to power politics. Such areas in Europe are the Balkan and Eastern-Europe, among whose young states Romania stands out because of the special historical development of its statehood and its territorial changes. The Romanian state became an independent European state over several historical periods, by building from several territorial bases, and through various kinds of political dependence, at the end of the 19th century. Later on, it grew its territory several times as a result of its peculiar 20th century politics. In the fourth section of our six part series we present the detailed history of the Romanian state from the peace treaty of Bucharest (May of 1918) till the start of peace conference of Versailles (January of 1919)

A comparative study on the privacy risks of face recognition libraries

The rapid development of machine learning and the decreasing costs of computational resources has led to a widespread usage of face recognition. While this technology offers numerous benefits, it also poses new risks. We consider risks related to the processing of face embeddings, which are floating point vectors representing the human face in an identifying way. Previously, we showed that even simple machine learning models are capable of inferring demographic attributes from embeddings, leading to the possibility of re-identification attacks. This paper examines three popular Python libraries for face recognition, comparing their face detection performance and inspecting how much risk each library's embeddings pose regarding the aforementioned data leakage. Our experiments were conducted on a balanced face image dataset of different sexes and races, allowing us to discover biases in our results

Analysis of Grasshopper, a Novel Social Network De-anonymization Algorithm

Social networks have an important and possibly key role in our society today. In addition to the benefits, serious privacy concerns also emerge: there are algorithms called de-anonymization attacks that are capable of re-identifying large fractions of anonymously published networks. A strong class of these attacks solely use the network structure to achieve their goals. In this paper we propose a novel structural de-anonymization attack called Grasshopper. By measurements we compare Grasshopper to the state-of-the-art algorithm, and highlight its enhanced capabilities, such as having negligible error rates and accessing yield levels that was not possible before: in cases when there is greater noise in the background knowledge. We furthermore evaluate an anonymity measure for the Grasshopper algorithm which enables the approximate ranking of nodes according to their re-identification rates. Finally, we characterize the robustness of Grasshopper in tackling identity separation, a privacy-enhancing technique that facilitate hiding of structural information