Non-linear model-predictive-control for thermomechanical ring rolling

he authors present a new ring rolling variant that combines a semi-warm forming process of a bearing ring with controlled cooling directly followed by a cold forming process. The aim is to produce near net shape rings with a selected microstructure and high strength without additional consecutive heat treatment. To achieve this, a new and fast control strategy is necessary that not only controls the geometrical forming of the ring, but also considers temperature development and microstructure formation. The proposed control strategy is based on the application of a fast semi-analytical simulation model with a very short response time in combination with a FE-analysis of the thermomechanical ring rolling process. The semianalytical model is used as a predictor and a parallel FEA or experimental results as a corrector for the control model. The aim is to correctly identify transient process parameters needed to achieve defined product properties as a basis for a later implementation in a non-linear modelpredictive-control of thermomechanical ring rolling. The new approach will be described in detail and demonstrated numerically and experimentally

An experimental and CFD study of liquid jet injection into a partially baffled mixing vessel: a contribution to process safety by improving the quenching of runaway reactions

Thermal runaway remains a problem in the process industries with poor or inadequate mixing contributing significantly to these incidents. An efficient way to quench such an uncontrolled chemical reaction is via the injection of a liquid jet containing a small quantity of a very active inhibiting agent (often called a stopper) that must be mixed into the bulk of the fluid to quench the reaction. The hazards associated with such runaway events mean that a validated computational fluid dynamics (CFD) model would be an extremely useful tool. In this paper, the injection of a jet at the flat free surface of a partially baffled agitated vessel has been studied both experimentally and numerically. The dependence of the jet trajectory on the injection parameters has been simulated using a single-phase flow CFD model together with Lagrangian particle tracking. The comparison of the numerical predictions with experimental data for the jet trajectories shows very good agreement. The analysis of the transport of a passive scalar carried by the fluid jet and thus into the bulk, together with the use of a new global mixing criterion adapted for safety issues, revealed the optimum injection conditions to maximise the mixing benefits of the bulk flow pattern

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022

Determination of the Mechanical Properties of Hot Stamped Parts from Numerical Simulations

AbstractHot stamping is a well-established process in car manufacturing today. However, the resulting mechanical properties of a hot stamped part and its behaviour during a crash are still open questions. The usual procedure includes destructive experiments to determine the mechanical properties resulting from the forming and quenching process. The gained information is then used for crash simulation. Using images from micrographs to determine the proportion of bainite and martensite resulting from the hot stamping process has proved to be difficult, as these structures are fairly similar and hard to distinguish.Sophisticated numerical simulations of the hot stamping process are available. The hardness resulting from the hot stamping process can be predicted fairly well from these process simulations. However, information like the tensile strength that is more relevant for the crash behaviour cannot be predicted that easily. It is not yet state of the art to map the results from the hot stamping simulation directly into the crash simulation. The approach to be presented in detail in this contribution uses the forming speed and the quenching velocity to predict the relevant mechanical properties of the hot stamped parts. Both input parameters, the forming speed and the quenching velocity, can be derived from the numerical hot stamping simulation. By means of experiments using a thermomechanical test system Gleeble well defined process parameters were used. Micro tensile test specimens were manufactured out of the Gleeble specimens to eliminate the effect of the Gaussian temperature profile created during the Gleeble experiments. Afterwards, tensile tests were carried out to derive a response surface for 22MnB5. The validated results allow the determination of the tensile strength of hot stamped parts from the numerical simulation of the hot stamping process with good accuracy