DIC Challenge 2.0: Developing Images and Guidelines for Evaluating Accuracy and Resolution of 2D Analyses

Experimental Mechanics - The DIC Challenge 2.0 follows on from the work accomplished in the first Digital Image Correlation (DIC) Challenge Reu et al. (Experimental Mechanics 58(7):1067, 1). The...     

Monitoring Methylmalonic Aciduria by NMR Urinomics

The paper reports on monitoring methylmalonic aciduria (MMA)-specific and non-specific metabolites via NMR urinomics. Five patients have been monitored over periods of time; things involved were diet, medication and occasional episodes of failing to comply with prescribed diets. An extended dataset of targeted metabolites is presented, and correlations with the type of MMA are underlined. A survey of previous NMR studies on MMA is also presented.     

Tensile failure of micro-concrete: from mechanical tests to FE meso-model with the help of X-ray tomography

In this work, concrete is studied at meso-scale (aggregates, macro-pores and mortar matrix), where the local failure mechanisms are known to drive the macroscopic behaviour of the material. In order to highlight the impact of the mechanical and morphological properties of each phase (along with their interfaces), micro-concrete specimens are prepared with rather small dimensions compared to the size of the heterogeneities. X-ray tomography is used to reliably obtain the morphology of the heterogeneous meso-structure, which is then given as an input to a 3D FE meso-model with enhanced discontinuities. A uniaxial tensile numerical simulation is performed as a first application. To validate the numerical model, a uniaxial tensile test of the same micro-concrete specimen is performed inside the X-ray scanner and the in-situ evolution of the micro-structure is followed. Thus, both a direct validation of the model and a valuable insight of the 3D fracture mechanisms while the load progresses are obtained. After identification of the numerical parameters, comparison of experimental and numerical results reveals the capability of the meso-model to reproduce the actual material response (in terms of macroscopic strength, Young’s modulus and fracture patterns), with the explicit representation of the meso-scale heterogeneities being its key feature. To further challenge the meso-model, a new morphology coming from an X-ray scan of another characteristic micro-concrete specimen is introduced and its macroscopic behaviour is computed without a priori numerical identification. Starting from an X-ray scan in meso-scale, it is shown that the 3D meso-model is capable to predict the macroscopic behaviour and the failure patterns of the material.

     

On the comparative study of three silver coins of the IIIrd century B.C. minted in Korkyra, Dyrrachion and by the Illyrian king Monounios

The microstructure of three silver coins dating back to the IIIrdcentury B.C. from the Illyrian King Monounios, the ancient Greek city of Dyrrachion and the ancient Greek city of Korkyra was studied with XRF, PIXE, microhardness measurements, and light and electron microscopy. From this investigation it turned out that these coins have different chemical compositions and different microstructures. The as-collected data allow the determination of a possible minting method. The Korkyra coin was probably hot-worked or cold-worked and annealed, while after cooling, it was cold-worked again. The coin of King Monounios is composed by equi-axed grains which are overrun by slip lines. Consequently it is likely that this coin was casted and then cold-struck. Finally the coin from Dyrrachion is characterized by small-sized grains and strain lines and as a result this coin was probably cold-struck. PACS 07.60.Pb; 78.70.En; 68.37.Ef; Hk; Lp; Nq; 61.66.Bi; 61.72.Mm