Swift Model Research Articles

Generation of SWIFT Models Virtually Using FE Analysis: Application to Cleat Simulations

ABSTRACT Parameterization methods for two “commercial tire models—short wavelength intermediate frequency tire (SWIFT) model and flexible ring tire model—are developed around existing testing protocols. As an example, cleat tests are used for estimating belt mass and stiffness and enveloping tests are used for estimating belt bending and contact stiffness parameters in the respective tire models. This is the only possible way when commercial tire models are parameterized and used mainly by vehicle original equipment manufacturer companies. At present, tire suppliers are stepping up to supply commercial tire models as a part of virtual tire submissions and are virtually simulating standard testing protocols. It is envisioned that with a proper fundamental understanding of commercial tire model parameters and their modeling approaches to capture the respective tire dynamics, we can develop simple finite element (FE) techniques to estimate respective tire model parameters, thereby avoiding the simulation of cleat and other dynamic tests by using FE. With that motivation, previous work has already shown the estimation of belt mass and bending properties from FE part separation technique [1]. In this work, with a fundamental understanding that the front cam and rear cam models in SWIFT are mathematically modeling the curvature of a loaded tire just outside of the footprint, we show that by fitting the tandem model to the loaded FE model deformed coordinates: length, height, order of cam, and distance between the cams can be estimated easily. This simple loaded FE model-fitting technique is combined with other computationally simple FE static stiffness, footprint, and modal analyses to estimate other SWIFT parameters. Finally, SWIFT models from the above-mentioned FE techniques are developed for several tire designs and validated against enveloping and dynamic in-plane cleat test data. The variations in enveloping and other ride metrics from simulations are inline with testing data.

SEAM: An integrated activation-coupled model of sentence processing and eye movements in reading

Models of eye-movement control during reading, developed largely within psychology, usually focus on visual, attentional, lexical, and motor processes but neglect post-lexical language processing; by contrast, models of sentence comprehension processes, developed largely within psycholinguistics, generally focus only on post-lexical language processes. We present a model that combines these two research threads, by integrating eye-movement control and sentence processing. Developing such an integrated model is extremely challenging and computationally demanding, but such an integration is an important step toward complete mathematical models of natural language comprehension in reading. We combine the SWIFT model of eye-movement control (Seelig et al., 2023) with key components of the Lewis and Vasishth sentence processing model (Lewis and Vasishth, 2005). This integration becomes possible, for the first time, due in part to recent advances in successful parameter identification in dynamical models, which allows us to investigate profile log-likelihoods for individual model parameters. We present a fully implemented proof-of-concept model demonstrating how such an integrated model can be achieved; our approach includes Bayesian model inference with Markov Chain Monte Carlo (MCMC) sampling as a key computational tool. The integrated Sentence-Processing and Eye-Movement Activation-Coupled Model (SEAM) can successfully reproduce eye movement patterns that arise due to similarity-based interference in reading. To our knowledge, this is the first-ever integration of a complete process model of eye-movement control with linguistic dependency completion processes in sentence comprehension. In future work, this proof of concept model will need to be evaluated using a comprehensive set of benchmark data.

Bridge Structural Reliability for Maintenance Prioritization

A significant percentage of assets of the Italian national bridge stock have outlived their nominal design service lives, a situation that has led to an increasing number of structural failures over the years, e.g. the deadly 2018 collapse of Morandi Bridge in Genoa. It would have been impossible to replace all existing infrastructural assets, so the focus was shifted to their upkeep. This is commonly achieved through structural health assessments of bridges and through properly planned and prioritized maintenance interventions. For a proper management of their bridge stock, infrastructure managers need a prioritization tool capable of quickly assessing whether a particular unit is in immediate need of maintenance. Currently, the prioritization of each bridge inside a stock is often based on its structural reliability. Yet, whilst several complex and time-consuming structural reliability assessment methodologies exist, these often fail to be quick in application. The present article provides for this shortcoming by introducing a novel simplified structural reliability model. In particular, it provides a framework for the assessment of overload, degradation, seismic, hydraulic and landslide risk factors and a detailed formalization of the most widespread, i.e. overload and degradation. On the basis of such a swift model, infrastructure managers can quickly detect rapidly deteriorating bridges, guarantee well-timed interventions and improve infrastructure user safety.

Performance evaluation of a liquid-sodium thermoacoustic engine with magnetohydrodynamic electricity generation based upon the Swift model.

Liquid sodium is an attractive working fluid for thermoacoustic conversion. Herein, a numerical study on a standing-wave thermoacoustic electricity generation system with liquid sodium as the working fluid is presented, based upon the Swift model. The characteristics of the thermoacoustic conversion and the output performance of the system have been investigated. The results show that the sodium engine can reach a power density much higher than the classical gas engine. Due to the strong acoustic coupling between components, the electricity output is significantly affected by the input heating power, the magnetic flux density, and the load ratio. In a typical case, the thermal-to-electric efficiency and the relative Carnot efficiency can reach 4.6% and 7.8%, respectively, with a temperature difference of 563 K and an input heat of 5 kW. More importantly, the output electricity density reaches 150 kW/m3, higher than some commercially available technologies. These results demonstrate the potential of such technology for small-scale electricity generation. Its extremely simple structure without any mechanical moving part endows the system with high reliability and long lifetime, if risks of corrosion and exposure to air and water can be avoided.

Tensile Behaviors and Mechanical Property Analyses of T-Welded Joint for Thin-Walled Parts in Consideration of Different TIG Welding Currents Using Multiple Damage Models and Fracture Criterions: Numerical Simulation and Experiment Validation.

In order to deeply investigate the tensile properties and fracture behaviors that are obtained by tensile tests of welded joints, constitutive and damage models are imperative for analyzing the tensile behaviors. In this work, the tensile tests are conducted on the T-welded joint specimens of aluminum alloy 6061-T6, which were cut from the T-welded joints of thin-walled parts under different welding currents of Tungsten Inert Gas Welding (TIGW). A modified Johnson-Cook (J-C) model based on the original J-C equation, Swift model, Voce model, and Hockett-Sherby (H-S) model, their linear combination model, and fracture failure model are constructed and applied to simulate tensile behaviors, combined with tensile test data. What is more, the finite element (FE) simulation of tension tests is executed with the VUMAT and VUSDFLD subroutines. Compared to those results simulated with different fracture criteria and tensile experiments, the tensile strength and yield strength of T-welded joint thin-walled parts under different welding currents were achieved, and their best mean errors were only about 1%. Furthermore, the accuracy of different fracture criteria is also evaluated by the correlation coefficient and mean squared error. The results show that the combination model can accurately predict the tensile properties and fracture behaviors of T-welded joints better than the single model, especially the results simulated with the Swift-H-S model and H-S-Voce model, which are in good agreement with tensile test results, which will provide an analysis foundation for enhancing the welding assembly quality and preventing fracture failure for complex thin-walled antenna structures.

General Blending Approach of Fundamental Cold Flow Models for an Almost Complete Cold Flow Model in Terms of Tensile Test

The importance of two major issues in obtaining an almost complete cold flow model (ACCFM) from a tensile test, that is, the necking conditions (including the Considère condition and tensile strength) and several selected representative flow points in both pre‐ and postnecking strain hardening regions, is emphasized. It is shown using the AISI 1010 steel for automatic multistage cold forging (AISI 1010 equivalent) that all the traditional fundamental flow models (FFMs) such as the Ludwik, Voce, Hollomon, and Swift models cannot simultaneously satisfy the two major issues. A general blended flow model (BFM) is proposed, which is a linear combination of known basis blending functions satisfying the necking conditions. The number of basis blending functions is unconstrained. The constants of the linear combination, called blending coefficients, are calculated by a set of linear equations to meet the selected representative flow points. Numerous combinations of basis flow functions are tried. It has been shown that there is no interpolation case among all the obtained BFMs but that there are a few ACCFM‐acceptable cases among them, which are based on the extrapolation of the basis blending functions.

Equivalent material properties of the heat-affected zone in welded cold-formed rectangular hollow section connections

A welded connection consists of three main material zones, the base material (BM), the heat-affect zone (HAZ), and the weld metal (WM). The strength of HAZ depends on the BM grade and manufacturing process, electrode grade, and welding parameters. Under certain conditions, HAZ has the lowest material strength, especially for high-strength steel. Therefore, a semi-empirical methodology is proposed to establish a constitutive model of HAZ necessary for predicting the fracture position of welded connections. This methodology is based on an engineering approach to consider HAZ as an isotropic and homogeneous material, with no consideration of different volumetric fractions of microstructures within a HAZ. The equivalent material properties of HAZ in butt-welded hollow section connections were investigated experimentally and numerically. Hardness tests and microstructure investigations were conducted to determine the boundaries of material variations and the width of HAZ. The stress–strain relationship of HAZ was established and calibrated based on tensile coupon tests and finite element analyses. Using the calibrated HAZ stress–strain relationship, the effect of transverse constraint imposed by the adjacent and stronger material (BM and WM) on HAZ was evaluated in the welded connections. Finally, the new methodology of a semi-empirical constitutive model based on the Swift model was used to propose equivalent characteristics of HAZ as a function of the mechanical properties of BM for a specific welding procedure considered in the project.

Ductilization of high carbon, high silicon carbide-free nanostructured bainitic steel

In the present study, the influence of the volume fraction of blocky austenite on the microstructure and mechanical properties of novel bainitic steel was investigated. The rolled homogenized sheets were austenitized at 950 °C and austempered at 250 °C for 18h (B15VA-1) and 50 h(B15VA-2). X-ray diffraction study of B15VA-1 & B15VA-2 confirmed the presence of carbide-free nanostructured bainitic ferrite (BF) and retained austenite (RA). Optical, scanning and transmission electron microscopic studies delineate the morphology of retained austenite to filmy and blocky forms. On the tensile deformation, majority of blocky austenite in B15VA-1 transformed to strain-induced martensite of ε type. Hardness and yield strength (YS) were increased with an increasing amount of bainitic ferrite, however, ultimate tensile strength (UTS) was found to be a strong function of the extent of strain-induced martensitic (SIM) transformation. As a result of the high amount of SIM, UTS of B15VA-1 increased to 1889 MPa. Ductility is mainly controlled by the transformation-induced plasticity of blocky austenite. Uniform plastic elongation and total plastic elongation were found to be 25% and 28%, respectively. The work hardening behavior can be described by the Swift model. Deformation under tensile load takes place in three stages which are homogeneous deformation, strain-induced martensitic transformation and multiphase deformation-led interaction of dislocations and their recovery. The alloy with nanostructured bainitic ferrite fails by mixed mode of ductile-brittle fracture.

Transport parameterization of the Polar SWIFT model (version 2)

Abstract. The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in the polar vortex in winter. It is intended for use in general circulation models (GCMs) and earth system models (ESMs) to enable the simulation of interactions between the ozone layer and climate when a full stratospheric chemistry scheme is computationally too expensive. In addition to the simulation of chemistry, ozone has to be transported in the GCM. As an alternative to the general schemes for the transport and mixing of tracers in the GCMs, a parameterization of the transport of ozone can be used in order to obtain the total change of ozone as the sum of the change by transport and by chemistry. One of the benefits of this approach is the easy and self-contained coupling to a GCM. Another potential advantage is that a transport parameterization based on reanalysis data and measurements can avoid deficiencies in the representation of transport in the GCMs, such as deficits in the representation of the Brewer–Dobson circulation caused by the gravity wave parameterization. Hence, we present a transport parameterization for the Polar SWIFT model that simulates the change in vortex-averaged ozone by transport in a fast and simple way without the need for a complex transport scheme in the GCM.

원통 인장시험과 고변형률의 유동특성을 이용한 체적소성가공용 실용적 혼합 유동모델

The fundamental flow models of metallic materials at room temperature, including the Ludwik, Hollomon, Swift and Voce models, were evaluated in terms of tensile test with an emphasis on the necking phenomena and post-necking behavior, to emphasize their limitation in satisfying tensile strength and Considère condition as well as the pre-necking and post-necking strain hardening. To resolve this limitation and enhance the applicability of the new proposed flow model to typical strain hardening materials, the Ludwik-Swift blended flow model is proposed after investigation into three blended flow models among the Ludwik, Voce and Swift models. Results revealed that there is no interpolation-based blended flow model of the fundamental flow models for the example flow curve exhibiting typical strain hardening but that the extrapolation-based combination of them can provide an engineering solution when the Ludwik and Swift models are blended. It was revealed that the reason for their good matching lies in the distinct difference in the strain hardening exponent, between the Ludwik and Swift models in the case of metallic materials with typical strain hardening.

Study on Flow Stress Model of AA5005 Material

Due to the continuous emergence of new alloys and the improvement of basic research requirements for aluminum alloy, researchers need to further study the flow constitutive relationship of new aluminum alloys. This paper used Model MTS-810 tensile machine to conduct tensile tests on AA5005 aluminum alloy at temperature of 360°C and strain rate of . Hollomon model, Swift model, Voce model, Voce+Voce model were used to compare the fitting accuracy with the experimental stress-strain curves, and the fitting parameters required by each formula were obtained from the fitting results, so as to obtain the constitutive model of AA5005 aluminum alloy. The Voce+Voce model which with more fitting freedom degree, lower flow stress increasing rate and saturation rate is most suitable to describe flow stress relation of aluminum alloy AA5005.

Effect of Cold Deformation on Microstructure and Mechanical Behavior of Commercially Pure Grade 4 Titanium Strip

The microstructure and mechanical behavior of commercially pure grade 4 (Gr.4) titanium strips with different deformations were studied by optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), uniaxial tensile test, and hardness test. The work-hardening characteristics of a Gr.4 strip were analyzed with a true-stress–strain curve. The results show that cold deformation can significantly improve the strength and hardness of a commercially pure titanium Gr.4 strip, which has significant work hardening characteristics. With the increase in deformation amount, the grain is stretched into a fibrous shape along the longitudinal direction, while the strength and hardness increase and the plasticity decreases. Moreover, there is a significant linear relationship between the tensile strength and hardness. The true-stress–true-strain curves of a Gr.4 strip in different states were analyzed by combining three hardening models. It was found that the true-stress–true-strain curve of an annealed Gr.4 strip can be regressed by the Ludwigson, Voce, and Swift models, the Ludwigson model has a higher fitting accuracy, and the fitting results of the tensile true-stress–true-strain curves of Gr.4 strips after cold deformation hardening are not ideal. The cold deformation mechanism of a Gr.4 strip is mainly based on slippage, with an increase in dislocation density and dislocation tanglement leading to work-hardening behavior during cold deformation.

A Review of Flow Characterization of Metallic Materials in the Cold Forming Temperature Range and Its Major Issues.

We focus on the importance of accurately describing the flow behaviors of metallic materials to be cold formed; we refer to several valuable examples. We review the typical experimental methods by which flow curves are obtained, in addition to several combined experimental-numerical methods. The characteristics of four fundamental flow models including the Ludwik, Voce, Hollomon, and Swift models are explored in detail. We classify all flow models in the literature into three groups, including the Ludwik and Voce families, and blends thereof. We review the experimental and numerical methods used to optimize the flow curves. Representative flow models are compared via tensile testing, with a focus on the necking point and pre- or post-necking strain hardening. Several closed-form function models employed for the non-isothermal analyses of cold metal forming are also examined. The traditional bilinear C-m model and derivatives thereof are used to describe the complicated flow behaviors of metallic materials at cold forming temperatures, particularly in terms of their applications to metal forming simulations and process optimization.

The SWIFT Model for Lichen Sclerosus Among Premenarchal Girls.

Delay in diagnosis of childhood lichen sclerosus (LS) can be ameliorated with an efficient evaluation tool. We sought to create a useful prognostic tool for rapid and accurate risk stratification for LS in premenarchal girls. We conducted a retrospective chart review at a single institution of premenarchal girls presenting with vulvovaginal complaints at a specialty pediatric and adolescent gynecology clinic at a major academic center. Sixty-nine patients seen between July 2019 and September 2020 were used as a pilot study to create a model for LS based on 18 signs and symptoms. Accuracy of the pilot model was confirmed in a larger data set (additional 105 patients, seen between January 2017 and December 2020), and model parameters were refined through cluster-based analytics. Pilot study yielded 5 predictors for LS: soreness (S), whitening (W), urinary incontinence (I), fissures (F), and thickening of the clitoral hood (T)-SWIFT. The final refined model is given as log odds (LS) = -7 + 3·S + 17·W + 3·I + 3·F + 18·T. This model yielded a >97% accuracy in predicting LS among 174 unique patients (LS prevalence = 18%). The SWIFT model accurately predicts clinical diagnosis of LS in premenarchal girls. Replication in other patient populations is highly encouraged. Awareness of LS is paramount, and an efficient, accurate evaluation tool will prove invaluable in assuring timely diagnosis and treatment for premenarchal patients.

A Bayesian approach to dynamical modeling of eye-movement control in reading of normal, mirrored, and scrambled texts.

In eye-movement control during reading, advanced process-oriented models have been developed to reproduce behavioral data. So far, model complexity and large numbers of model parameters prevented rigorous statistical inference and modeling of interindividual differences. Here we propose a Bayesian approach to both problems for one representative computational model of sentence reading (SWIFT; Engbert et al., Psychological Review, 112, 2005, pp. 777-813). We used experimental data from 36 subjects who read the text in a normal and one of four manipulated text layouts (e.g., mirrored and scrambled letters). The SWIFT model was fitted to subjects and experimental conditions individually to investigate between-subject variability. Based on posterior distributions of model parameters, fixation probabilities and durations are reliably recovered from simulated data and reproduced for withheld empirical data, at both the experimental condition and subject levels. A subsequent statistical analysis of model parameters across reading conditions generates model-driven explanations for observable effects between conditions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Strengthening and strain hardening mechanisms of a plain medium carbon steel by multiscale lamellar structures

Plain medium carbon steel with the multiscale lamellar structure was produced through quenching and subsequent warm rolling. The microstructure characteristic was conducted based on statistical parameters and physical metallurgy by electron backscattered diffraction (EBSD), the mechanical properties were investigated using uniaxial tensile tests at room temperature. The heterogeneous structure is characterized with multiscale lamellar distribution with three-level grain size spanning the nano-to micro-meter range, which is defined as ultrafine-grained (UFG), fine-grained (FG) and coarse-grained (CG). The results of kernel average misorientation (KAM) and Taylor factor (TF) revealed that the existence of interface effects. The nucleation and accumulation of geometrically necessary dislocation (GND) were activated by multiscale lamellae, to cause the formation of sharp up-turn in strain hardening curves. The results of multiple model fits showed that the Swift model was the most appropriate for the studied steel, and the instantaneous strain hardening values were obtained on its basis. The existence of an extra strengthening mechanism (hetero-deformation induced strengthening) was confirmed by calculating. The results showed WR84 had outstanding mechanical properties and strain hardening ability. The improved toughness of WR84 is mainly attributed to ultrafine grain strengthening, and the reasonable ductility is owing to hierarchical hetero-structured of the lamellae, particle dispersion distribution and the three-level coordinated control of grain size as they can increase the strain hardening ability by the interaction constraint.

A Novel Flow Model of Strain Hardening and Softening for Use in Tensile Testing of a Cylindrical Specimen at Room Temperature.

We develop a new flow model based on the Swift method, which is both versatile and accurate when used to describe flow stress in terms of strain hardening and damage softening. A practical issue associated with flow stress at room temperature is discussed in terms of tensile testing of a cylindrical specimen; we deal with both material identification and finite element predictions. The flow model has four major components, namely the stress before, at, and after the necking point and around fracture point. The Swift model has the drawback that not all major points of stress can be covered simultaneously. A term of strain to the third or fourth power (the “second strain hardening exponent”), multiplied and thus controlled by a second strain hardening parameter, can be neglected at small strains. Any effect of the second strain hardening exponent on the identification of the necking point is thus negligible. We use this term to enhance the flexibility and accuracy of our new flow model, which naturally couples flow stress with damage using the same hardening constant as a function of damage. The hardening constant becomes negative when damage exceeds a critical value that causes a drastic drop in flow stress.

Formability of aluminum 1050A at high temperatures: Numerical modeling and experimental validation

Abstract The sheet metals are prone to large plastic deformation during forming processes. The study purpose is to investigate 1050A aluminum sheets thermomechanical behavior with ductile damage. A modified Swift model coupled to isotropic ductile damage and thermal effects was used. The forming parameters are introduced using Swift model coefficients and Erichsen index. An inverse identification procedure is applied to non-homogeneous Erichsen test results. Bulge test is then used to validate the identified parameters. Erichsen test (Punch force vs displacement) results were obtained by experimental testing and simulation to build the objective function. Aluminum 1050A plasticity flow parameters and ductile damage variables were identified using a part of Erichsen test results. The remaining part of Erichsen test and bulge test results were used for validation. The numerical approach allowed the detection of failure zones with respect to thermal gradient induced by heat exchange. Within the isothermal condition, equivalent stresses and strains for 1050A Aluminum were obtained by simulations and experimental data.

Estimation of sea water salinity from dielectric measurements: Effect of temperature

Dielectric measurements have been carried out for distilled water and saline water solutions of salinities 10000, 20000, 30000, 40000 ppm, as well as sea water of Diu beach area, using Anritsu Shockline Vector Network Analyzer (VNA, model no: MS46322A) in the frequency range from 1 GHz to 20 GHz, over the temperatures of 20°, 30° and 40 °C. From the measured values of dielectric constant and dielectric loss, the values of tanδ, conductivity and emissivity of water solutions have been calculated. The variation in dielectric properties of water with salinity and temperature of measurement is compared with values calculated using Stogryn equations as well as Klein and Swift model and results are found to be in good agreement with corresponding values. From the dielectric loss values and the emissivity values of distilled water and saline water solutions at certain fixed frequencies, the salinity of sea water collected from Diu beach has been estimated to be 36,327 ppm which agrees very well with the physicochemical analysis report of laboratory.

Multi-objective optimization, experimental and CFD approach for performance analysis in square cyclone separator

ABSTRACT In this article, square cyclone separator performance has been analyzed by varying the five important geometric parameters. Primarily, Swift (1971) model is considered to develop the mathematical square cyclone. Body height and inlet height, total height, inlet width and outlet diameter are the controlling parameters considered for governing the responses namely cut-off diameter and pressure drop. The L27 orthogonal array is developed using Taguchi Robust Design. Based on the design matrix, the regression equation is developed for the two responses. The quality of the equation arrived has been validated by ANOVA followed by optimization using multi-objective genetic algorithm approach. The optimal results are identified through the Pareto approach. The optimization results are validated by experimental analysis. Numerical simulation is performed to obtain the flow pattern and separation efficiency. The final result confirms that the optimum square cyclone produces the enhanced performance.