Transient Module Research Articles

AGN-201K educational and research reactor benchmark analyses by McCARD Monte Carlo calculations

In this study, a benchmark model for the AGN-201K educational and research reactor was newly developed based on its Final Safety Analysis Report data, with any unclear or missing specifications obtained from different AGN-201 reactors. The AGN-201K benchmark model was verified for criticality problems at various critical rod positions, the approach-to-criticality experiment problem, the fine rod worth measurement problem, and the flux distribution problem. The model was evaluated by comparing experimental values with calculated results by the McCARD Monte Carlo neutronic transport code, with the McCARD results of the AGN-201K benchmark showing good agreement with the experimental results. The most noteworthy point is that the recently developed McCARD TDMC (Time-Dependent Monte Carlo) transient module was successfully demonstrated through AGN-201K transient benchmark analyses. It is also noted that the reactor periods from McCARD results were very similar to the experimental results, confirming the suitability of TDMC analysis for realistic applications. Furthermore, the new AGN-201K benchmark model is expected to serve as a practical and useful tool for verifying and validating newly developed neutronic codes through various steady-state and transient analyses.

Development of multi-physics calculation method in lead cooled fast reactor code system MOSASAUR

A full-core three-dimensional multi-physics calculation method was researched based on the Lead cooled fast reactor (LFR) code system MOSASAUR, which is focused on both core steady-state and transient analyses of LFR. In the previous version of MOSASAUR, cross-sections generation module and core steady-state simulation module have been developed. In this research, the stiffness confinement method is employed to solve the time-dependent multi-group neutron transport equation to expand the capabilities of core transient analyses. And the thermal hydraulic calculation method is developed as thermal feedback module for core steady-state and transient analyses. Based on the fixed-point iteration scheme, the neutron module and thermal hydraulic module are coupled at each time step. The LMW benchmark and the problem based on ORAL 19-rod bundle are employed to verify the accuracy of transient calculation and thermal hydraulic module respectively. Finally, the multi-physics calculation method is utilized to simulate the transient process of the MicroURANUS core. The simulation results demonstrate the capability of the constructed multi-physics calculation framework to accurately simulate the transient behaviors of LMRs. Numerical results showed the good accuracy of the newly-developed multi-physics calculation module with MOSASAUR.

Анализ течений при лазерно-акустической обработке нержавеющей стали AISI 316L

The influence of ultrasonic vibrations on the flow of molten metal during laser processing is investigated. This problem is of interest within the context of modernization of existing technological processes, such as laser welding and cladding, for the production of structures with improved physical and mechanical properties. The introduction of additional ultrasonic energy into the liquid metal bath intensifies the metal flow via forced stirring, which provides its homogenization and leads to an increase in the mechanical properties of the processed material due to the growth of the number of crystallization centers during its solidification. In order to get a better understanding of this combined process and to control it, a method for synthesizing hydrodynamic and strength solvers used in the ANSYS software package is proposed. Setting up the coupling between two corresponding ANSYS Transient Structural and ANSYS CFX modules is executed through the additional ANSYS System Coupling module. Under this numerical implementation of the problem, it is possible to calculate the displacements at the solid metal boundary and their transfer to the liquid metal boundary and vice versa at each moment of time. The impact of laser radiation on the liquid metal is considered taking into account Marangoni convection, and convection and radiation heat transfer. The results of numerical experiments make it possible to conduct a qualitative and quantitative comparison between the liquid AISI 316L stainless steel flows formed without and with ultrasonic vibration. It is shown that the intensification and deceleration of the flows is observed at the average values of the ultrasonic amplitude. This fact correlates with the moments of time at which the deformed surface of the metal in the bath moves down and up. A comparative analysis of the maximum axial velocities inside the liquid metal bath was conducted. The absence of ultrasonic action on the liquid metal motion was observed at the maximum values of the vibration amplitude, which correspond to the maximum displacement and deformation of the surface at the interface between liquid and solid.

Time-frequency analysis of nonlinear structures under nonstationary excitation by directly solving structural dynamic equation through absolute displacement

The time-frequency evolution of seismic ground motion energy under strong earthquakes, which can be described by the evolutionary power spectral density (EPSD) matrix, will amplify the most unfavorable responses of members in nonlinear structural systems. However, the existing general finite element software fails to reduce the dimension of the EPSD matrix and then decouple time from frequency in frequency domain analysis. This failure greatly limits the simulation and calculation of multi-dimensional nonlinear structures with multiple degrees of freedom by the stochastic vibration theory. In this study, the pseudo excitation method (PEM), which can direct solve structural dynamic equations using absolute displacement, is used to derive the self-spectral and cross-spectral densities of seismic ground motions in one-dimensional and multi-dimensional cases. In MATLAB, the EPSD matrix is transformed into a four-dimensional uniform modulation excitation matrix independent of the time variable. Nonlinear iteration is conducted and the precise integration method (PIM) is employed through a transient analysis module. Furthermore, a simple one-dimensional example is presented to verify the correctness of the proposed algorithm herein. Finally, as an example, we select important parameters of the coherence model at different supports of a half-through three-span concrete-filled steel tubular (CFST) tied-arch bridge in view of real engineering conditions, and calculate the time-varying power spectrum and variance of the responses of arch ribs, arch feet and the bridge deck system. The results show that the theoretical derivation and the algorithm constructed in this paper can simulate the time-delay effect of the nonlinear structural system. This proves the feasibility of general finite element software in solving and analyzing random responses to multi-dimensional and multi-support non-stationary excitation of nonlinear structures.

Temperature field calculation of rail flash welding

The forging stage of rail flash welding has a decisive influence on joint strength, and the study of the temperature distribution in the process has an important role in further improving joint strength. In this paper, three calculation methods for the temperature field are given. First, the finite element model of the temperature field before forging rail flash welding is established by using the transient heat module of Ansys software and verified by infrared temperature measurement. Second, the temperature distribution of different parts of the rail before flash welding is obtained by using infrared thermal imaging equipment. Third, Matlab software is used to calculate the temperature of the non-measured part. Finally, the temperature distribution function along the rail axis is fitted through the temperature measurement data. The temperature distribution before the top forging of the rail flash welding can be used to analyze the joint and heat-affected zone organization and properties effectively and to guide the parameter setting and industrial production.

Generalization of crack growth mechanisms under isothermal and thermomechanical fatigue by COD and ERR parameters

An experimental-computational study of the crack opening displacement (COD) was performed to evaluate the ability of this parameter through the hysteresis loop area and energy release rate (ERR) to characterise fatigue crack growth under isothermal and thermomechanical conditions. To this end, a range of experimental crack growth tests were carried out including isothermal fatigue (IF), creep-fatigue interaction (CFI), in-phase (IP), and out-of-phase (OOP) thermomechanical fatigue (TMF). The crack growth experimental results in terms of COD and ERR were interpreted based on multi-physics finite element analyses of the stress–strain and displacement fields performed by incorporating Maxwell 3D, Fluent, and the transient structural modules of ANSYS. As a result of measurements and computations, the COD on the outer surface of the SENT specimen at the location of the original notch was found to be directly related to the crack tip opening displacement (CTOD). To gain insight into the fatigue crack growth mechanism operating under isothermal and TMF conditions, the fracture surfaces of all the tested specimens were examined using a scanning electron microscope to compare the morphology and changes in the dominant failure mechanisms. It was found that propagating cracks under isothermal and thermomechanical conditions interact with the microstructure of the material, and supporting fractography evidenced subtle differences in fracture mechanisms in terms of COD and ERR parameters. The relationship between the experimentally determined energy release rate and degradation function in the fatigue phase-field fracture methodology is discussed.

Electric and Magnetic Fields Analysis of the Safety Distance for UAV Inspection around Extra-High Voltage Transmission Lines

The deployment of small unmanned aerial vehicles (UAVs), or drones, for transmission line inspections, has brought attention to the potential impact of electromagnetic fields (EMFs) on UAV operations. This work describes a mathematical model based on the finite elements method (FEM), designed to examine the electric and magnetic fields produced by extra-high voltage (EHV) conductors. The current study extends the analysis to encompass both electric and magnetic fields and evaluates the safe distances for UAVs operating near 345 kV, 500 kV, and 765 kV transmission lines. The electromagnetic environment around these EHV transmission lines was simulated using electrostatic, magnetostatic, and transient magnetic modules within the QuickField software 6.6. Electric and magnetic profiles were estimated using 2D finite element analysis, including a numerical simulation for phase-to-phase fault EMFs for the above transmission lines. These results were then cross-verified with theoretical calculations at specific intervals and further validated using the EMFACDC analytical method developed by the International Telecommunication Union. This comprehensive assessment concludes that precise distance considerations are necessary to ensure UAV safety during power line inspections, mitigating potential risks from EMF interference.

Development and validation of transient analysis module in nodal diffusion code RAST-V with Kalinin-3 coolant transient benchmark

This study introduces a transient analysis module developed for RAST-V and validates it using the Kalinin-3 benchmark problem. For the benchmark analysis, RAST-V standalone and STREAM/RAST-V calculations were performed. STREAM supplies the few-group constants and RAST-V conducts a 3D core simulation utilizing few-group cross-sectional data. To improve accuracy, the main solver was developed based on the advanced semi-analytic nodal method. To evaluate the computational capability of the transient analysis module in RAST-V, Kalinin-3 benchmark is employed. Kalinin-3 represents a coolant transient benchmark that offers experimental data during the deactivation of the Main Circulation Pumps. Consequently, the transient calculations reflected the changes in the reactor flow rate. Benchmark comprising steady-state and transient calculations. During the steady state, the STREAM/RAST-V combination demonstrated a 30 ppm root mean square difference from 0 to 128.50 EFPD. For the transient calculations, STREAM/RAST-V showed power differences within ±7 % over a range of 0–300 s. Axial offset differences were within ±3 %, and the RMS difference in radial power ranged within 2.596 % at both 0 and 300 s. Overall, this study effectively demonstrated the newly developed transient solver in RAST-V and validated it using the Kalinin-3 benchmark problem.

Computational and experimental study on the resistance welding process of a glass fiber‐reinforced epoxy‐based composite with thermoplastic interlayer adherent

AbstractIn this work, resistance welding of a glass fiber‐reinforced epoxy composite (GFRC) was studied with numerical optimization and experimental validation. A steel mesh and polymethyl methacrylate (PMMA) films were used as the heating element and adherent interlayers, respectively. A transient heat transfer module was implemented to conduct the parametric optimization study, with variables of electricity power, clamping distance and weld time. The optimal welding condition was then confirmed as 20 W, 0.4 mm and 30 s, with a melting degree of 95.2%. A thermal meter and a thermal camera validated the simulated temperature results. Welding quality was experimentally characterized by single lap shear tests and scanning electron microscopy (SEM). The highest lap shear strength of 3.8 ± 0.3 MPa was captured on the specimen welded with the optimized condition. This was 76% that of the benchmark made with the adhesive bonding method but it was over 200 times faster.Highlights Resistance welding of GFRC with PMMA films and a steel mesh is studied with FEA. Simulation results are quantitatively validated with experimental methods. Optimal welding conditions are confirmed in association with welding tests.

Modeling of Pipe Whip Phenomenon Induced by Fast Transients Based on Fluid–Structure Interaction Method Using a Coupled 1D/3D Modeling Approach

The sudden increase in the operating pressure of nuclear power plants (NPPs) is due to the water hammer phenomenon, which tends to produce a whipping effect that causes serious damage to the pipes and their surroundings. The mechanical response of these pipelines under the influence of such fast fluid transients can be estimated using the fluid–structure interaction (FSI) method. The computational time and expense are predominantly dependent on the number of finite elements developed in the model. Hence, an effective modeling technique with limited and efficient nodes and elements is desired to obtain the closest possible results. A coupled 1D/3D finite element modeling approach using the FSI method is proposed to determine the influence of fast transients on the mechanical pipe whipping behavior of gas pipelines in NPPs. The geometric coupled modeling approach utilizes the presence of both the 3D solid elements and the 1D beam elements sharing a local conjunction. The computational model is modelled for a pipe-to-wall impact test scenario taken from the previously conducted French Commissariat a l’Energie Atomique (CEA) pipe whip experiments. The results of displacement, stresses, and impact velocity at the 3D section featuring the elbow are compared for the change in the 3D solid length varied at the juncture of the elbow. The computed results from the Ansys FSI coupling method using the Fluent and Transient Structural modules provides fair validation with the previously conducted experimental results and correlates with the CEA pipe whip tests on pipe-to-wall impact models. Thus, the 1D/3D coupled modeling approach, which minimizes the area of the solid region by constricting it to the impact area with appropriate contact modeling at the junctures, can be considered in the future for decreasing the computational time and the creation of finite elements.

Verification and validation of multi-physics numerical analysis of thermomechanical fatigue test conditions under induction heating and forced convection

This paper presents the validation and verification of thermomechanical fatigue multi-physics numerical analysis. To determine the local thermomechanical stress–strain state and displacement fields, an algorithm for the multi-physics numerical calculations is developed and implemented incorporating the Maxwell 3D, Fluent, and Transient Structural modules of ANSYS 2021R1. Single-edge-notch tension specimen heating is modelled using a rectangular induction coil. The temperature distribution in the specimen under forced and natural convection is considered. The nonlinear solid mechanics are analysed considering the temperature nonuniformity under in-phase and out-of-phase loading cycles with a triangular waveform and temperature range of 400–650 °C. Sensitivity analysis is performed to explore the effects of the mesh density. To complement the multi-physics computations, crack-opening displacement and infrared thermography temperature distribution measurements are employed for the thermomechanical fatigue test control in a single-edge-notch tension specimen produced from a nickel-based alloy XH73M. Based on the interconnected verification and validation of coupled numerical analysis, recommended ranges of numerical model parameters have been found to provide a stable solution.

Evaluation of Accelerator Pedal Strength under Critical Loads Using the Finite Element Method

The core idea of the research consists in a formulation of boundary conditions of a mechanical accelerator pedal’s strength in an Ansys environment, whose conditions are equivalent to full-scale tests under the critical loads defined by the UNECE’s Regulation No. 13. The lack of regulatory requirements for the strength of pedal types other than brake pedals is a major gap in vehicle certification, especially when it comes to agricultural machinery. In such cases, the authors suggest being guided by UNECE R 13 regarding the strength of the accelerator and other types of pedals and checking their behavior under loads of at least 1000 N. The real value of the yield strength of the material (Silumin 4000) is very important, both in the physical real-life experiments and in FEA simulation. The critical case of a short-term shock loading of the pedal in its extreme position has been considered separately. With the help of the Ansys Explicit Dynamics module, results of a pedal’s behavior were obtained; it lost its integrity and suffered destruction. It is also necessary to check the intermediate stress values depending on the loads for direct and hybrid tasks using the Transient Structural module in order to estimate other critical cases of the pedal behavior.

Crack tip field analysis for thermo-mechanical fatigue loading

This study aimed to establish a computational strategy for the thermo-mechanical fatigue (TMF) simulations of crack tip fields considering both the in-phase (IP) and out-of-phase (OOP) loading histories. To this end, an algorithm for multi-physics numerical calculations was developed and implemented by incorporating Maxwell 3D, Fluent, and the transient structural modules of ANSYS 2021R1, to understand the mechanics of crack tip deformation under thermo-mechanical loading conditions. These computations are based on the coupled heat loss from magnetic field eddy currents and the forced convective air-cooling accounted for by turbulence model response, which provides the gradients of mechanical elastic–plastic deformations. The proposed algorithm was applied to replicate and analyse the crack growth test conditions of polycrystalline XH73M nickel-based alloys subjected to a triangular waveform of IP and OOP cycles and a temperature range of 400–650 °C. Further, multi-physics finite element (FE) modelling of the stress, strain, and displacement fields in uncracked and fractured single-edge-notch tension specimens was performed. The novelty of the results lies in the crack tip fields, which strongly influenced by the phase relation between mechanical loading and temperature, provided the electromagnetic and fluid dynamics characteristics and the elastic–plastic properties of the material are dependent on the current temperature and time across a particular deformation cycle. Notably, the complete three-dimensional multi-physics FE analysis presented herein is expected to contribute toward a better understanding of the different mechanisms driving TMF crack growth and also help address the related outstanding questions.

Transient Solid Oxide Cell Reactor Model Used in rSOC Mode-Switching Analysis and Power Split Control of an SOFC-Battery Hybrid

Defossilization of the global energy system requires a transition towards intermittent renewable energy sources and approaches that enable efficient conversion of primary energy sources into electrical energy. Due to their high efficiency in converting chemical into electrical energy and vice versa, solid oxide cell (SOC) systems provide solutions for both of these aspects. However, mode transitions in SOC operation require operating strategies to ensure that thermal gradients in the reactors are suppressed. In this study, two researched cases utilizing SOC’s are presented, based on simulation studies and experiments with an SOC multi-reactor module. The transient module model is validated in 75 kW electrolysis and polygeneration, and applied to analyze the effect of internal steam methane reforming on the temperature profile of the reactors. Subsequently, it is coupled with a validated Li-ion battery model, to test a rule-based power split control strategy suitable for a demand curve characteristic of a ship.

Transient modelling of water condensation rate for top of line corrosion

Top of line corrosion (TOLC) is typically a concern in the first few kilometres of wet gas pipelines where water in the warm gas condenses on the cold pipe walls. With the introduction of a subsea tieback to existing infrastructure, the changing fluid composition and temperature profiles may increase condensation in sections not previously expected to have condensation. Accurate prediction of the water condensation rate (WCR) becomes essential to support reliable corrosion modelling. Transient flow simulation of pipeline operating conditions and detailed heat transfer modelling is required to calculate the WCR. This calculation is complicated because the mass of water condensation is very small compared to the fluid mass in the pipeline, and sensitive to glycol that is often present in the aqueous phase for hydrate management purposes. This paper introduces a method to calculate WCR by using detailed transient modelling of the pipeline operating conditions. The fluid thermal hydraulic behaviour and hydraulic pressure drop in the pipeline are considered in the model. The fluid composition in the pipeline and glycol component in the aqueous phase are calculated by using a PVT software package. A few sensitivity studies will also be presented. The implications of Equation of State (EoS) and transient flow module on WCR calculation will be quantified. The WCR sensitivity results will be analysed based on varying inlet temperatures, glycol concentrations, and pipeline heat transfer coefficients. A WCR calculation method will be recommended for TOLC modelling.

Automotive Steering System and Its Controller Design for Intelligent Vehicles

<div>With the rapid development of intelligent vehicles technology, it is extremely urgent to solve environmental pollution and energy crisis. The electric intelligent vehicles technology can accelerate the world to move towards low carbonization and intelligence. In this article, one automatic steering system and its controller are designed with this electric vehicle as the verification platform. First, based on the digital mock-up (DMU) module of the CATIA digital prototype, the motion simulation of the automatic steering system is carried out. Then, the transient dynamics and fatigue analysis module from ANSYS Workbench 16.0 software is used to simulate and analyze the transmission mechanism. After verifying the reasonable strength of the real vehicle parts, the original platform steering system is reformed. Our intelligent vehicle uses a monocular charge-coupled device (CCD) to detect road marking lines and then employs a linear two degrees of freedom (2-DOF) vehicle model to establish a preview deviation model based on the visual navigation lane lines. A vehicle lateral control method combining fuzzy logic rules, adaptive proportional-integral-derivative (PID) control strategy, and preview deviation is designed. A lateral controller is built using Simulink software for lane tracking simulation, and a good tracking effect is obtained. Finally, the results of low-speed real vehicle tests show that the vehicle can stably track the target lane line at low-speed conditions.</div>

Three-dimensional modelling and analysis of fracture characteristics of overlaid asphalt pavement with initial crack under temperature and traffic loading

The asphalt overlay is a major maintenance strategy to improve the performance of cracked pavement. However, the crack would propagate upwards and eventually reach to the limit of service life. The potential of the crack propagation of overlaid pavement with cracks will be the key point to evaluate the overlay strategy and the pavement service life. In this study, the Extended Finite Element Method (XFEM) in ANSYS was utilized as the analysis engine to establish the pavement finite model with cracks. Taking Beijing area as example, the transient thermal analysis module was used to construct the 24-hour temperature field in winter. The stress intensity factor (SIF) was adopted as the index to evaluate the effectiveness of the overlay thickness, the length and inclination of crack, as well as temperature under traffic loading. The results indicated that the sliding crack is the major fracture mode for pavement under pure vehicle loading, while the mixed mode of opening and sliding mode changes to be the major fracture mode for pavement under low temperature. The geometric property of existing crack has a significant influence on the critical loading position and peak value of SIF in overlaid pavement. And the promotion effect of increasing the overlay thickness on preventing crack propagation was gradually weakening. The achievement in this study will bring an insight into crack propagation for pavement overlay paving as well as the pavement maintenance.

High-precision transient fuel consumption model based on support vector regression

Due to the increasingly severe environmental issues caused by transportation, energy conservation and emission reduction have become one of the most important research directions in the field of transportation. As the key tool for estimating transient fuel consumption, fuel consumption models are crucial for quantifying the energy consumption of automobiles and achieving energy conservation and emission reduction. However, most existing fuel consumption models suffer from problems such as a complex structure, difficult-to-determine model coefficients, and difficult-to-measure input parameters. Therefore, it is necessary to propose a high-precision fuel consumption model with good applicability and easy implementation. The model proposed in this paper adopted a structure of steady-state estimation and transient correction and used support vector regression to predict fuel consumption. First, the engine torque was fitted based on the steady-state data, and the steady-state module was established. Then, based on data analysis using the Gaussian mixture model, the transient motion was divided into three driving conditions, and the transient module was obtained by transient correction for different driving conditions. Ultimately, the performance of the model was validated. The results show that the mean absolute percentage error of the new model is less than 14%, and the mean absolute error is less than 0.16 cc/s, which is a significant improvement compared with other classic models, indicating that the new model has a high prediction accuracy. In addition, the new model takes the most common engine speed, vehicle speed, and acceleration as inputs, making it easy to use and has good applicability and popularization value.

Taguchi Analysis of the Deformation Characteristics of Single-Point Cutting Tool with Micro-Tool Coatings During Orthogonal Machining

Machining, the art of processing materials, has progressed significantly over the past century. Advances in tool materials look at blended advantages of conventional and modern tool materials through coatings at micro-scales. Tool coatings improve the hot hardness and wear resistance of tool tip and faces. The current study utilizes the Taguchi technique to analyze the deformation response of HSS tools with three different tool coatings—titanium carbide, titanium nitride and titanium aluminum nitride. The coating thicknesses of 10, 50 and 100 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m were employed on the rake face and the flank faces of the single-point cutting tool. The response of the tools while machining medium carbon steel 42CrMo4 has been studied using the finite element approach—transient structural analysis module on ANSYS®. The tool deformation was taken up as the key metric.

An intelligent fault detection and diagnosis monitoring system for reactor operational resilience: Power transient identification

Various microreactor designs under development aim at fulfilling electricity and heat production requirements affordably and reliably in a variety of applications, like power generation for remote communities and military bases. The fission battery deployment strategy for microreactors provides battery-like simplicity for its installation and operation. A successful fission battery must be cost competitive, have unit standardization, enable flexible installation, possess high reliability, and feature unattended operations. Due to the design and operational features of microreactors, successful unattended operations of the system must be enabled through an on-line monitoring (OLM) system that can effectively and reliably detect and diagnose any fault in the reactor. This research introduces the concept and approach of an intelligent Fault Detection and Diagnosis Monitoring System (FDDMS) that can provide power transient dependent fault detection and diagnosis to fit within a future autonomous control framework. Specifically, this paper develops the first FDDMS module, the Power Transient Module, to reliably identify reactor operations as steady state, ramping up in power, or ramping down in power using data from a broad-scope simulator. Knowledge of the current power transient in the reactor is paramount for effective fault detection and diagnosis in any operational regime. This paper explores various data-driven methods to accurately evaluate the power transients: 1) Principal Component Analysis and Support Vector Machines, 2) Deep Neural Networks, and 3) Convolutional Neural Networks. To prepare the sensor data collected from the simulator for training the data-driven models, several preprocessing techniques were tested to optimize for evaluation accuracy. The final model selected for the Power Transient Module produced perfect evaluation results for several power transients, including in previously unseen regimes. Foundation for further module development of the FDDMS was established. Future works will see the implementation of the remaining FDDMS architecture.