Bilinear damage evolution in AA2011 wire drawing processes

This paper presents an experimental and numerical analysis of damage evolution in AA2011 aluminum alloy wires drawn under different scenarios. To this end, load-unload tensile tests were firstly carried out in order to characterize the degradation of the mechanical response in every cycle where the experimental results show a bilinear damage relationship in terms of the effective plastic strain. Therefore, a modification of the classical Lemaitre model is proposed in this work in order to reproduce bilinear paths of damage with the addition of only two parameters that can be directly obtained from the material characterization. Then, the damage predictive capability of this new experimental-based model is assessed in numerical simulations of the drawing process in one and two passes (considering for this last case the sequential and tandem configurations) where the computed predictions are compared with the corresponding experimental data showing a good agreement between them.

Landslide Susceptibility Analysis by Applying TRIGRS to a Reliable Geotechnical Slope Model

This paper presents the results of a research aimed at analysing the susceptibility to shallow landslides of a study area in the Calabria region (Southern Italy). These shallow landslides, which in some cases evolve as debris flows, periodically affect the study area, causing damage to structures and infrastructure. The involved soils come from the weathering of gneissic rocks and cover about 60% of the study area. To fulfil the goal of the research, the Transient Rainfall Infiltration and Grid-based Slope-Stability (TRIGRS) model was first used, assuming input data (including physical and mechanical parameters of soils) provided by the scientific literature. Then, the preliminary results obtained were used to properly locate in situ investigations that included sampling. Geotechnical laboratory tests allowed characterising the investigated soils, and related parameters were used as new input data of the TRIGRS model. The generated shallow landslide susceptibility scenario showed a good predictive capability based on the adoption of a cutoff-independent performance technique.

EUROfusion-theory and advanced simulation coordination (E-TASC): programme and the role of high performance computing

The paper is a written summary of an overview oral presentation given at the 1st Spanish Fusion HPC Workshop that took place on the 27th November 2020 as an online event. Given that over the next few years ITER will move to its operation phase and the European-DEMO design will be significantly advanced, the EUROfusion consortium has initiated a coordination effort in theory and advanced simulation to address some of the challenges of the fusion research in Horizon EUROPE (2021-2027), i.e. the next EU Framework Programme for Research and Technological Development. This initiative has been called E-TASC that stands for EUROfusion-Theory and Advanced Simulation Coordination. The general and guiding principles of E-TASC are summarized in the paper. In addition, an overview of the scientific results obtained in a pilot phase (2019-2020) of E-TASC are provided while highlighting the importance of the required progress in computational methods and HPC techniques. In the initial phase, five pilot theory and simulation tasks were initiated: 1. Towards a validated predictive capability of the L-H transition and pedestal physics; 2. Electron runaway in tokamak disruptions in the presence of massive material injection; 3. Fast code for the calculation of neoclassical toroidal viscosity in stellarators and tokamaks; 4. Development of a neutral gas kinetics modular code; 5. European edge and boundary code for reactor-relevant devices. In this paper we report on recent progress made by each of these projects.

Assessment of CHF and Post-CHF Heat Transfer Models for High-Pressure Condition

Supercritical heat transfer systems may undergo trans-critical procedures and work at subcritical conditions during startup, shutdown, or some accidents. However, well-validated heat transfer models for the high-pressure condition (P/Pc>0.7) are still missing. In the present work, with exhaustive literature review, extensive experimental databanks of CHF and post-dryout heat transfer under high-pressure condition are established, respectively. Existing prediction models for the high-pressure condition are also summarized from all over the world. Thereby, with the aid of the high-pressure experimental databank, prediction models get evaluated. It has been demonstrated that CHF correlation developed by Song et al. shows good predictive capability. Post-dryout heat transfer could get well predicted by the Song correlation. These recommended prediction models could be implemented to upgrade safety analysis codes for simulation of trans-critical transients.

Assessing Mechanical Catheter Dysfunction in Peritoneal Dialysis Patients: A Case Control, Proof-of-Concept Study

New guidelines on evaluation of peritoneal membrane function recommend ruling out catheter dysfunction when evaluating patients with low ultrafiltration capacity. We introduce the use of a combination of parameters obtained from daily measurements of the cycler software for predicting catheter dysfunction in automated peritoneal dialysis patients. Out of 117 patients treated between 2015 and 2021, all patients with verified catheter dysfunction (n=14) were identified and compared to controls (n=19). We retrieved cycler data for seven days each and tested parameters predictive capability of catheter dysfunction. Total number of alarms/week >7 as single predictive parameter of catheter dislocation identified 85.7% (sensitivity) of patients with dislocated catheter and 31.6% (1-specificity) of control patients. A combination of parameters (number of alarms/week >7, drain time >22 min, ultrafiltration of last fill <150 mL) where at least two of three parameters appeared identified the same proportion of patients with catheter dislocation, but was more accurate in identifying controls (21% false positive). An easily applicable combination of daily cycler readout parameters, also available in remote monitoring platforms can be used as predictor of inadequate catheter function during routine follow-up with potential for earlier diagnosis of this frequent complication in the future.

Bayesian Uncertainty Identification of Model Parameters for the Jointed Structures with Nonlinearity

Jointed structures in engineering naturally perform with some of nonlinearity and uncertainty, which significantly affect the dynamic characteristics of the structural system. In this paper, the method of Bayesian uncertainty identification of model parameters for the jointed structures with local nonlinearity is proposed. Firstly, the nonlinear stiffness and damping of the joints under the random excitation are represented with functions of excitation magnitude in terms of the equivalent linearization. The process of uncertainty identification is separated from the representation of local nonlinearity. In this way, the dynamic behavior of the joints is penetratingly characterized instead of ascribing the nonlinearity to uncertainty. Secondly, a variable-expanded Bayesian (VEB) method is originally proposed to identify the mixed of aleatory and epistemic uncertainties of model parameters. Different from traditional Bayesian identification, the aleatory uncertainties of model parameters are identified as one of the most important parts rather than only measurement noise of output. Notablely, a series of intermediate variables are introduced to expand the parameter with aleatory uncertainty in order to overcome the difficulty of establishing the likelihood function. Moreover, a 3-DOF numerical example is illustrated with case studies to verify the proposed method. The influence of observed sample size and prior distribution selection on the identification results is tested. Furthermore, an engineering example of the jointed structure with rubber isolators is performed to show the practicability of the proposed method. It is indicated that the computational model updated with the accurately identified parameters with both nonlinearity and uncertainty has shown the excellent predictive capability.

Uniting The Sun’s Hale Magnetic Cycle and ‘Extended Solar Cycle’ Paradigms

Through meticulous daily observation of the Sun’s large-scale magnetic field the Wilcox Solar Observatory has catalogued two magnetic (Hale) cycles of solar activity. Those two (∼22-year long) Hale cycles have yielded four (∼11-year long) sunspot cycles-21 through 24. Recent research has highlighted the persistence of the “Extended Solar Cycle” (ESC) and its connection to the fundamental Hale Cycle-albeit through a host of proxies resulting from image analysis of the solar photosphere, chromosphere and corona. This Letter presents, for the first time, a direct mapping between the ESC, the Sun’s toroidal magnetic field evolution of the Hale Cycle. As Sunspot Cycle 25 begins to accelerate its growth, interest in mapping the Hale and Extended cycles could not be higher given potential predictive capability that synoptic scale observations can provide.

Testing the PTT Rheological Model for Extrusion of Virgin and Composite Materials in View of Enhanced Conductivity and Mechanical Recycling Potential

One of the challenges for the manufacturing processes of polymeric parts is the dedicated control of composite melt flow. In the present work, the predictive capability of the Phan-Thien-Tanner (PTT) viscoelastic model is evaluated in relation to the extrudate swell from slit dies at 200 °C, considering polypropylene and graphite filler, and applying ANSYS Polyflow software. It is shown that for sufficiently low filler amounts (below 10%; volumetric) the PTT accurately reflects the viscoelastic interactions, but at higher filler amounts too large swellings are predicted. One can although obtain insights on the swelling in the height direction and consider a broader range of swelling areas compared to virgin materials. Guidelines are also provided for future experiments and model development, including the omission of the no-slip process boundary condition.