Algorithm for automatic fatigue crack growth simulation on welded high strength steels

Nowadays the demand for high strength steels is increasing. In order to design and develop high performance products, it is essential to understand the fatigue behavior of these materials. When considering welded components, the fatigue behavior is even more complex. The material parameters may change along the crack growth and mixed mode crack propagation may also occur. To assess welded high strength steel fatigue behavior, different welded CT specimens were tested. The Paris law material constants were obtained for the heat affected zone material. Fatigue crack growth life predictions were made using the obtained parameters and different automatic techniques. Previous work showed that the ABAQUS extended finite element method can predict fatigue crack growth, but as the implementation of the Paris law is not straight forward, to many conversions must be made and the results are too computer intensive. A simpler and more intuitive Python algorithm was developed, to enable the use of the experimental material parameters, to predict the crack propagation path. The obtain results show a good agreement with both the experimental Paris curves, and the analytical solution

Optimal cruciform specimen design using the direct multi-search method and design variable influence study

Nowadays the development of new testing machines and the optimization of new specimen geometries are two very demanding activities. In order to study complex material stress and strain distributions, as in-plane biaxial loading, one must develop new technical solutions. A new type of testing machine has been developed by the present authors, for the fatigue testing of cruciform specimens, but the low capacity of the testing machine requires the optimization of the specimen in order to achieve higher but uniform stress and strain distributions on the specimen center. In this paper, the authors describe the procedure to optimize one possible geometry for cruciform specimens, able to determine the fatigue initiation life of material subjected to out of phase in-plane biaxial fatigue loadings. The high number of design variables were optimized using the direct multi-search method, considering two objective functions, the stress level on the specimen center and the uniformity of the strain distribution on a 1.0 mm radius of the specimen center. Several Pareto Fronts were obtained for different material thickness, considering the commercially available sheet metal thickness. With the optimal solution, the influence of every design variable was studied in order to provide others with a powerful tool that allows selecting the optimal geometry for the desired application. The results are presented in the form of design equations considering that the main design variable, the material thickness, was chosen from a Renard series of preferred numbers. The end user is then able to configure the optimal specimen for the required fatigue test.info:eu-repo/semantics/publishedVersio

The complete genome sequence of Chromobacterium violaceum reveals remarkable and exploitable bacterial adaptability

Chromobacterium violaceum is one of millions of species of free-living microorganisms that populate the soil and water in the extant areas of tropical biodiversity around the world. Its complete genome sequence reveals (i) extensive alternative pathways for energy generation, (ii) ≈500 ORFs for transport-related proteins, (iii) complex and extensive systems for stress adaptation and motility, and (iv) wide-spread utilization of quorum sensing for control of inducible systems, all of which underpin the versatility and adaptability of the organism. The genome also contains extensive but incomplete arrays of ORFs coding for proteins associated with mammalian pathogenicity, possibly involved in the occasional but often fatal cases of human C. violaceum infection. There is, in addition, a series of previously unknown but important enzymes and secondary metabolites including paraquat-inducible proteins, drug and heavy-metal-resistance proteins, multiple chitinases, and proteins for the detoxification of xenobiotics that may have biotechnological applications