Parameters Of Numerical Model Research Articles

Numerical Investigation on Crack Propagation of Three-Dimensional Pipeline Under Seismic Wave Loading

Cracks in transport pipelines significantly impact their structural safety, making pipeline fracture damage a major concern. While experimental tests can study crack growth, their setup and costs are substantial. To address this, our work involves parametric analyses to investigate the effects of initial crack length, load types and sizes, and pipe wall thickness on the crack tip stress field. The finite element model is established according to the actual operation, and the crack defects of the pipe are established by the extended finite element method (XFEM). The crack tip variation is studied by extracting the von Mises stress and strain at the crack tip. When the crack propagates, the stress field at the crack tip will fluctuate in a certain range. The relationship between stress field fluctuation and crack propagation was studied by changing the XFEM crack growth for comparative analysis. Utilizing 429 numerical results obtained from a parametric numerical model implemented with Python and Abaqus, we establish a back propagation (BP) neural network prediction model to forecast the stress field at the crack tip. The relative errors between the numerical results and the predictions by our model remain below 5%. In conclusion, our proposed approach for analyzing pipeline fracture under multiple loads proves valuable for pipeline safety assessment, and it offers useful insights for evaluating the suitability of transportation pipelines.

An investigation of a supersonic fluidic oscillator generating pulsations in chambers during pressurization

A load-type supersonic fluidic oscillator has potential application for introducing small oscillations in the chamber of a superplastic forming process to improve performance. This paper presents a study of a special bi-stable load-type supersonic fluidic oscillator capable of simultaneously producing self-sustained oscillations in two gas pressure chambers during their filling at high-pressure. The experimental portion of the work verifies the robust nature of the device performance. Distinct differences, however, are observed compared to those previously shown for a similar prototype supplying pressure fluctuations to a single chamber at low pressure. It is also found that a three-dimensional computational fluid dynamics model is required to accurately simulate the transient filling process of the current oscillator facility, unlike the previous case. This leads to an unaffordable computational cost. To address this issue, a low-order fluid circuit model is developed. This simplified approach is based on a quasi-steady assumption and is of the same form as the one which accurately predicts the performance of the previous prototype. The model is “numerically empirical” in that the model parameters are determined using steady state 3D-CFD analysis rather than physical experiments. The circuit model combined with a lumped parameter numerical model of tank filling with realistic heat transfer to the surroundings provides an accurate and rapid prediction of the transient performance of the device. Also, the usefulness of the circuit model as an industrial design tool is demonstrated by predicting the effect of two design changes.

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.

Uncertainty of the crack width model based on fracture of concrete

AbstractA reliable crack width assessment is a basic part of the sustainability control of the reinforced concrete structures subjected to corrosion degradation. The uncertainty of the concrete cracking model based on a finite element method and nonlinear fracture mechanics is investigated. The parameters of numerical model, such as the finite element mesh size and amount and arrangement of reinforcement are the subject of a case study. The uncertainty of the crack width model is verified on the experimental data from the tests of reinforced concrete beams. The constitutive model of crack propagation is based on the smeared cracks. The effects of numerical discretization as well as dimensional simplification are shown.

NUMERICAL MODELING OF BAR-BUILT ESTUARIES AND IMPLICATIONS FOR THE MANAGEMENT OF INTERMITTENT INLETS

Bar-built estuaries are common in tropical and temperate regions, accounting for nearly 3 percent of the estuaries throughout the world (McSweeney et al. 2017). Bar-built estuaries tend to have intermittent inlets that can open from the estuary side outward in regions with seasonal changes in river discharge (Kraus et al., 2008; Orescanin and Scooler 2018). It is well known that intermittent inlet dynamics primarily depend on the interplay between wave energy and inlet discharge driven by lagoon water levels (Rich and Keller, 2013). Forcing processes are generally understood, however, less is known about their interaction or thresholds, which is ultimately what drives the closure of intermittent inlets. The aim of this study is to explore numerical modeling techniques and parameters to simulate the hydrodynamics and closure of intermittent inlets in bar-built estuaries. Increasing the understanding of the conditions that lead to closing of intermittent inlets would allow for improved flood, sediment, and water quality management in the communities surrounding bar-built estuaries.

Seismic and collapse behavior of existing high-rise steel buildings under long-period earthquakes

This work presented the experimental and numerical evaluation of the seismic and collapse behavior of Japanese existing high-rise steel buildings subjected to long-period ground motions (LPGMs). Initially, the experiment (E-Defense, 2008) was performed by the full-scale shaking table tests on a typical 21-story steel frame substructure. Accordingly, a nonlinear rotational spring model was used in the numerical modeling. In consideration of the stiffness/strength deterioration and fatigue fracture of beam-column connections, the cyclic pushover analysis was utilized to account for such effect using seismic response data from system-level testing. Subsequently, the numerical model parameters were derived and validated with the initial experiment on the high-rise steel frame substructure. Herein, a well agreement on the seismic failure behavior between simulation and experiment was found in this situation. Furthermore, both field-welded and shop-welded connections on the seismic performance were included for comparison. For the 21-story prototype steel building (built before 1970s), a series of numerical collapse analyses were performed. The above revised model using nonlinear static pushover analysis and time history analysis were conducted to simulate and compare the effects of connection details and composite slabs on the 21-story prototype building. Finally, a cyclic loading protocol for simulating LPGMs was proposed, and the related ultimate failure behavior of the high-rise building was analytically discussed. Critically, this work should provide a viable strategy to numerically simulate the seismic and collapse behavior of high-rise steel buildings in this progressing construction field.

Blast response of bioinspired nacre-like staggered composite plates combined with steel and polyurea

Inspired by the mother-of-pearl layered structure, a multilayered staggered composite plate (SCP) consisting of steel and polyurea was designed, and its dynamic responses under high impulse loads were investigated. The precision of the numerical model design and parameter selection was first validated by the blast experiment results of a normal composite plate (NCP). The center point displacement, velocity, and acceleration of the NCP and SCP were compared, and the corresponding values for the SCP decreased by 38.43%, 5.77%, and 63.30%, respectively. The backplate overpressure and intra-plate stress of the SCP were reduced by 86.67% and 81.48%, respectively. The SCP greatly improved the energy absorption efficiency through the phenomena of interlocking, friction, and slippage between layers. As the delamination number of the SCP increased, both the displacement, velocity, and acceleration of the center point and the energy absorption efficiency increased. When the polyurea layer thickness ratio and the steel table thickness ratio were 0.1675 and 0.125, respectively, the deformation response and energy absorption efficiency of the SCP tended to be similar. Finally, the effective modulus of elasticity of the SCP was analyzed based on a shear-lag model.

Multirate mass transfer simulation of denitrification in a woodchip bioreactor

Denitrifying woodchip bioreactors (DWBs) have proven to be an efficient nature-based solution for nitrate removal. Modeling DWBs is required for improving their design and operation, but is hindered by the complexity of the modeled system where numerous chemical species and model parameters are needed. Reactions inside the woodchips are different from those at the edges, causing chemical localization (i.e., apparent simultaneous occurrence of incompatible reactions). We used the Multi Rate Mass Transfer (MRMT) approach to overcome these problems when simulating reactive transport processes in a DWB located at Kiruna, Sweden. Besides denitrification, other nitrogen-cycling processes (e.g., nitrification, dissimilatory nitrate reduction to ammonium, anammox) and alternative electron donors (e.g. oxygen, sulfate) were also considered. Biomass concentration is incorporated into the biochemical reaction rates, including growth and decay, to characterize microbial catalysis. We found that the MRMT model: 1) can account for the heterogeneity of the porous woodchips; 2) was capable of reproducing the nitrogen species evolution in the DWB with kinetic parameters from the literature; and 3) allows reproducing localized biochemical reactions (e.g., aerobic reactions on the woodchip edges, near the DWB entrance and anaerobic reactions inside); and 4) reproduces the full denitrification reactions sequence, but with the different reactions occurring in different portions of the woodchip (e.g., nitrate to nitrite near the edges and nitrite to nitrous oxide further inside). The latter observation suggests that increasing woodchip size may reduce the outflow of these undesired species.

Numerical modeling of FS-trench IGBTs by TCAD and its parameter extraction method

The electrical behavior of the IGBTs is the key factors to the application of IGBTs. Technology Computer Aided Design (TCAD) is one of the most effective methods for characterizing of electrical behavior of IGBT. However, the great difficulties in extracting the model's parameters hinder its widely applications. In the present work, a high-precision TCAD model for FS-Trench IGBT was established and verified by experiments. Firstly, the parameters necessary for TCAD models were analyzed in theoretical and experimental. The key process parameters need to be determined in a value range table. A Convolutional Neural Network (CNN) was proposed and trained to form a relationship from characteristic curves to key process parameters. Subsequently, the numerical model's parameters were established by combining the trained CNN model with experimental data. Finally, the TCAD model was established and the simulations of IGBTs were carried out and verified by experiments. Results demonstrate that the proposed TCAD model is well consistent with experiments with a Root Mean Square Error (RMSE) of about 3.7 %. This work may provide a feasible method to obtain highly precise numerical models of power semiconductor devices. It may also promote the application of Artificial Intelligence in the device modeling and optimization design.

Master equation model for solute transport in river basins: part I channel fluvial scale

Normal and anomalous diffusion are ubiquitous in many physical complex systems. Here we define a system of diffusion equations generalized in time and space, using the conservation principles of mass and momentum at channel scale by a master equation. A numerical model for describing the steady one-dimensional advection-dispersion equation for solute transport in streams and channels imposed with point-loading is presented. We find the numerical model parameter as the solution of this system by estimating the transition probability that characterizes the physical phenomenon in the diffusion regime. The results presented (Part I) refer to the channel scale and represent the first part of a research project that has been extended to the basin scale.

Numerical Evaluation of Dynamic Earth Lateral Pressure on Basement Walls in Cohesionless Soils (A Case Study of Iranian Earthquakes)

Various earth-retaining structures are extensively used in different civil engineering projects. Using the results of experimental and numerical modeling, the effect of the earthquake loading on the distribution of the earth lateral pressures on basement walls was investigated. The UBCHYST constitutive model was used in the performed numerical simulations, and using the results of 12 centrifuge dynamic model tests, a calibration process was conducted to obtain the proper input parameters for numerical models. Based on the results, some correlations between the dynamic increment coefficient of earth lateral pressure (ΔKae) and the free-field peak ground acceleration (PGAff) were established. The correlations are different for stiff and flexible basement walls. In the end, the results of the model calibration process were verified by the examination of 12 major earthquakes that occurred in the Iran plateau. The results showed that the proposed ΔKae-PGAff correlations are precise enough for the applied design projects.

Differential evolution-based convolutional neural networks: An automatic architecture design method for intrusion detection in industrial control systems

Industrial control systems (ICSs) are facing serious and evolving security threats because of a variety of malicious attacks. Deep learning-based intrusion detection systems (IDSs) have been widely considered as one of promising security solutions for ICSs, but these deep neural networks for IDSs in ICSs have been designed manually, which are extremely dependent on expert experience with numerous model parameters. This paper makes the first attempt to develop an automatic architecture design method of convolutional neural networks (CNNs) based on differential evolution (abbreviated as DE-CNN) for the intrusion detection issue in ICSs. The first phase of the proposed DE-CNN is the off-line architecture optimization of the CNNs constructed by three basic units such as ResNetBlockUnit, DenseNetBlockUnit, and PoolingUnit, including encoding the architecture parameters of a CNN as a population, evaluating the fitness of the population by the validation accuracy and the number of CNN model parameters, implementing the evolutionary process including mutation and crossover operations, and selecting the best individual from the population. Then, the optimal CNN model obtained by the off-line optimization of DE-CNN is deployed for the online IDSs. The experimental results on two intrusion detection datasets in ICSs including SWaT and WADI have demonstrated the superiority of the proposed DE-CNN to the state-of-the-art manually-designed and neuroevolution-based methods under both unsupervised and supervised learning in terms of Precision, Recall, F1-Score and the number of the CNN model parameters.

Bayesian RC-Frame Finite Element Model Updating and Damage Estimation Using Nested Sampling with Nonlinear Time History

This paper proposes a Bayesian RC-frame finite element model updating (FEMU) and damage state estimation approach using the nonlinear acceleration time history based on nested sampling. Numerical RC-frame finite element model (FEM) parameters are selected through nested sampling, and their probability density is estimated using nonlinear time history. In the first step, we estimate the error standard deviation and select the FEM parameters that are required to be updated by FEMU. In the second step, we estimate the probability density of the selected parameters and realize the FEMU through the resampling method and kernel density estimation (KDE). Additionally, we propose a damage state estimate approach, which is a derivative method of the FEMU sample. The numerical results demonstrate that the proposed approach is reliable for the Bayesian FEMU and damage state estimation using nonlinear time history.

Viable Energy Recovery Strategies Through Advanced Directional Control Valve

The demand for more efficient machines is pushing hydraulic manufacturers to develop a new generation of systems capable of energy saving and recovering. An advanced flow sharing directional control valve with downstream compensation reduces meter-out pressure losses and recovers energy both in combined movements and with overrunning loads. Tests carried out on a prototype on a test bench confirm the proper functioning of the concept and allow tuning its lumped parameters numerical model. A control strategy based on keeping the optimal compensator position allows computing the maximum theoretical recovery. The simulation of a mini-excavator digging cycle shows the energy saving and recovery compared to a standard flow sharing system.

Robust Design Optimization of Expensive Stochastic Simulators Under Lack-of-Knowledge

Abstract Robust design optimization of stochastic black-box functions is a challenging task in engineering practice. Crashworthiness optimization qualifies as such problem especially with regards to the high computational costs. Moreover, in early design phases, there may be significant uncertainty about the numerical model parameters. Therefore, this paper proposes an adaptive surrogate-based strategy for robust design optimization of noise-contaminated models under lack-of-knowledge uncertainty. This approach is a significant extension to the robustness under lack-of-knowledge method (RULOK) previously introduced by the authors, which was limited to noise-free models. In this work, it is proposed to use a Gaussian Process as a regression model based on a noisy kernel. The learning process is adapted to account for noise variance either imposed and known or empirically learned as part of the learning process. The method is demonstrated on three analytical benchmarks and one engineering crashworthiness optimization problem. In the case studies, multiple ways of determining the noise kernel are investigated: (1) based on a coefficient of variation, (2) calibration in the Gaussian Process model, (3) based on engineering judgment, including a study of the sensitivity of the result with respect to these parameters. The results highlight that the proposed method is able to efficiently identify a robust design point even with extremely limited or biased prior knowledge about the noise.

Simulation of a ground-mounted prism in ABL flow using LES: on overview of error metrics and distribution

The accuracy of wind loading predictions using Large Eddy Simulation (LES) is usually influenced by numerous model parameters, which can influence the obtained results. The validation of numerical simulations with traditional Wind Tunnel Test (WTT) is still an important task, necessary to increase our a priori knowledge of possible inaccuracies and set up mitigation strategies. In this study, LES is used to simulate the wind fields around an isolated model high-rise building, under seven wind attack angles and validated with WTT results. The influence of various settings and parameters on the model performance is studied. For the angle of attack showing higher inaccuracy, different mesh refinement strategies and turbulence models are tested. Results indicate that LES can accurately predict the mean and local maxima of the pressure coefficients for both perpendicular and skew wind attack angles, as well as reproduce global forces and their envelopes with very good accuracy. Conversely, pronounced errors are found in the prediction of the pressure coefficient standard deviation and the local minima. The highest deviations between LES and WTT are found close to the leading edge in correspondence of flow separations which are observed in WTT and not in LES for skew flows. The addition of boundary layer cells and the use of different subgrid models have very limited effectiveness in modifying the obtained results for the analysed case.

Hydraulic Vehicle Damper Controlled by Piezoelectric Valve.

In this paper, an original construction of a vehicle vibration damper controlled by means of a valve based on piezoelectric actuator is presented and investigated. The presented valve allows us to control dissipation characteristics of the damper faster than in other solutions adjusting the size of the gap through which the oil flows between the chambers of the damper. The article also presents the results of the experimental investigation of the above-mentioned damper showing the possibility of changing the value of the damping force five times in about 10 ms by changing the voltage supplying the piezoelectric actuator. Based on these results, dissipative characteristics were determined which enabled the identification of the parameters of the damper numerical model. The article also presents the results of numerical investigations a vehicle model equipped with the developed dampers. The results showed that the developed damper controlled by the use of the piezoelectric actuator can significantly affect vehicle traffic safety by reducing the variation of vertical forces acting on the wheels. The results obtained are so promising that the authors undertook preparations to conduct road tests of a vehicle equipped with the developed dampers.

Back-Analysis of Slope GNSS Displacements Using Geographically Weighted Regression and Least Squares Algorithms

Numerical simulation is a powerful technique for slope stability assessment and landslide hazard investigation. However, the physicomechanical parameters of the simulation results are susceptible to uncertainty. Displacement back-analysis is considered an effective method for the prediction of the geomechanical parameters of numerical models; therefore, it can be used to deal with the parameter uncertainty problem. In this study, to improve the interpretability of the back-analysis model, an analytical function relationship between slope displacements and physicomechanical parameters was established using geographically weighted regression. By combining the least-squares and linear-algebra algorithms, a displacement back-analysis method based on geographically weighted regression (DBA-GWR) was developed; in particular, the multi-objective displacement back-analysis was represented as an analytical problem. The developed method was subsequently used for a slope of the Guiwu Expressway in Guangxi, China. Simulation experiments and GNSS real-data experiments demonstrated that the GWR could achieve high-precision deformation modelling in the spatial domain with model-fitting precision in the order of mm. Compared with state-of-the-art methods, the precision of the simulated displacement with the proposed method was significantly improved, and equivalent physicomechanical parameters with higher accuracy were obtained. Based on the corrected numerical model, the most severely deformed profiles were forward-analysed, and the simulated deformation and distribution patterns were found to be in good agreement with the field investigation results. This approach is significant for the determination of geomechanical parameters and the accurate assessment of slope safety using monitoring data.

The Application of Porous Material in the Capillary Barrier System for Residual Soil Slope Stabilization

A drainage system that is used to flow excess rainfall infiltration is an excellent alternative to enhance lateral diversion capacity at the interface of Grade VI and Grade V soil slope layers thus delaying breakthrough occurrences. This study aims to explore the performance of porous transport layer on slope behavior via numerical simulation by GeoStudio SEEP/W. In this study, a 2-dimensional non-homogenous residual soil configuration model, which is composed of Grade VI and Grade V residual soil was constructed. Laboratory tests were conducted on the soil samples collected from the Faculty of Engineering, UTM JB to determine the soil properties as input parameters in numerical modeling. The soil slope model is designed as an infinite residual soil slope according to Jabatan Kerja Raya (JKR) design specification on the cut slope and fill slope with 27 ° inclination respectively. High rainfall intensities were chosen to represent rainfall infiltration in Johor. The slope model was modeled with a porous transport layer at the Grade VI and Grade V layer interfaces. The porous transport layer is introduced as the transport layer and its effectiveness is expected to be similar to the optimum compacted soil mix in the previous study. In addition, porous concrete as a transport layer is introduced and it must meet the adequate porosity and hydraulic conductivity requirements. The suction distribution pattern with depth and time was subsequently observed to identify the volume of infiltrated water and retention time in the transport layer. The porous transport layer is also expected to be efficient in diverting infiltrating water and decreasing the interface's suction distribution between Grade VI and Grade V soil layers. HIGHLIGHTS The water built up within the residual soil slope is one of the common factors of rainfall-induced residual soil slope failure thus porous transport layer introduced The detailed laboratory testing and numerical modelling conducted in order to identify the performance of porous transport layer within residual soil slope The application of porous transport layer sandwiched between residual soil is effective to decrease the water built up and matric suction thus decrease the risk of slope failure GRAPHICAL ABSTRACT

Determination of Johnson-Cook Constitutive of 15-5 PH Steel Processed by Selective Laser Melting.

To obtain a Johnson-Cook model of 15-5 PH steel formed by selective laser melting (SLM), and to determine the difference between the forging process, in this work, mechanical testing, penetration testing and numerical simulations were used to study 15-5 PH steel formed by SLM and forging. Finally, the Johnson-Cook model parameters and failure parameters of the 15-5 PH steel formed by SLM and forging were obtained. We found that the SLM process was beneficial for refining the grain size of 15-5 PH steel and for improving the mechanical properties of 15-5 PH steel, where the yield strength of its specimens increased by 13.1% compared with the forged specimens. The error between the numerical simulations and penetration tests was less than 10%, which verified the validity of the numerical model parameters. It was also found that the penetration ability and abrasion resistance of the SLM-shaped projectiles were slightly superior to those of the forged projectiles.