bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical properties and formability of EN AW-7075 in cold forming processes
Authors: Behrens B-A , Hübner S , Vogt H , Golovko O , Behrens S , Nürnberger F
Published: November 2020

Due to a low density and high tensile strength, the aluminum alloy EN AW 7075 T6 offers a high lightweight potential for structural components. Since its formability is limited at room temperature in the T6 temper state, the potential of this alloy for automotive bodies is only utilizable by adapted deep drawing processes. In recent years, process chains suited for warm and hot forming have been researched and developed. However, warm and hot forming solutions require additional process steps and a complex tooling system in comparison to cold forming processes. Alternatively, the forming of such blanks at room temperature in the W temper state is favorable since conventional tools can be used. The W temper state is a heat treatment condition achieved after solution heat treatment and subsequent quenching, which is characterized by an increased ductility. However, this condition is unstable, due to the onset of natural ageing. With increasing time after the quenching step, the strength of the material increases, which leads to a reduction of formability. Another phenomenon that occurs after quenching is the Portevin Le-Chatelier effect. This effect causes the formation of flow lines during cold forming and results in a decrease of ductility. Hence, the objective of the investigations was to determine the formability of EN AW 7075 as a function of the natural ageing time after solution heat treatment and quenching. Therefore, tensile tests of various aged samples were carried out. The results show a relation of the formability to the natural ageing time and a dependency on the quenching rate. Furthermore, a heat treatment strategy for EN AW-7075 was developed, that considers manufacturing processes like the cathodic dip coating. The influence of the quenching rate, ageing time and temperature as well as the influence of temperature of the paint baking process after the cathodic dip coating were considered. Therefore, a design of experiments and tensile tests were carried out. Thus, the deep drawing of EN AW-7075 at room temperature is particularly promoted.
The roles of yield function and plastic potential under non-associated flow rule for formability prediction with perturbation approach
Authors: Hu Q , Yoon J W
Published: November 2020

In this study, the perturbation approach for predicting material’s forming limit strains under non-associated flow rule (non-AFR) is proposed. The influence of yield function and plastic potential function on the forming limit curve (FLC) evaluated by the perturbation approach are discussed through analyzing the normalized growth rate of a perturbation. In the framework of non-AFR, Hill’48 and Yld2000-2d are chosen for AA5754-O. The results show that the left side of FLCs predicted with the different forms of yield function and plastic potential nearly overlap. Hence, it is concluded that the yield function and plastic potential have a negligible influence on the forming limit strain under a negative strain path. However, the FLC under a positive strain path is principally dependent on the relationship between strain ratio β and stress ratio α, which can be determined by the plastic potential. Additionally, in comparison to the FLC under AFR, an increase in the forming limits strain is observed near the plain strain region, when the derivative of the normalized yield function concerning α is positive and vice versa.
Description of stress-strain response and evaluation of the formability for Al-Cu-Mg alloy under the impact hydroforming
Authors: Chen Da-Yong , Zhang Shi-Hong , Xu Yong , Ma Yan , Song Hong-Wu , Xia Liang-Liang
Published: November 2020

This study aims at investigating on the descriptions of stress-strain response and the assessment of formability for Al-Cu-Mg alloy under impact hydroforming (IHF). IHF process effectively combines the advantages of the flexible liquid and the impact impulse. The formability of low plastic materials can be increased by using IHF process. The elongation of Al-Cu-Mg alloy can even be more than 50 % compared with the quasi-static forming means (27 %∼30 %) if the strain rate was on the level of 5000/s. The stress-strain curve is characterized with S-shape. It is found that the strain hardening rate decreases linearly at the stage III, increases linearly at the stage IV and decreases non-linearly at the stage V. The deformation mechanism is the interaction of dislocation accumulation and dynamic recovery under the transmission from non-sheared to sheared precipitation when the strain rate is on the level of 3000/s∼5000/s. A modified Kocks-Mecking model was established to describe the mechanical property of AA 2B06. In addition, the high strain rate formability was evaluated by the new means which revealed the relationship between the impact energies, deep drawing height ratios and the deep drawing ratios by using the finite element modelling of the solid liquid coupling.
Comparison of Artificial Intelligence Methods for Prediction of Mechanical Properties
Authors: Lee Kyungmin , Hong Charmgil , Lee Eun-Ho , Yang WooHo
Published: November 2020

This paper compares artificial intelligence (AI) methods to predict mechanical properties of sheet metal in stamping processes. The deviation of the mechanical properties of each blank leads to unpredicted failures in stamping processes, such as fracture and spring back. The research team of this paper has been building a real time control system for stamping process in a smart factory. In order to facilitate that, it is necessary to predict the mechanical properties of each blank with non-destructive testing. The regression models based on the linear algebraic scheme have traditionally brought reliable results in terms of matching the measured non-destructive testing values to the mechanical properties. With a parallel to algebraic regression models, in recent studies on various domains, AI models have been adopted to improve the accuracy of the end-results and effectiveness of the models. This paper discusses the applicability of AI models for predicting the mechanical properties based on the eddy-current non-destructive testing method. For the study, 6 input features are collected through the eddy-current non-destructive testing to map eddy-current input data to mechanical properties of the blank. Yield stress and uniform elongation were predicted by using five AI methods, i.e., regularized linear regression, support vector regularized linear regression, support vector regression, multi-layer neural network, random forest regression, and gradient boosting regression were compared. The model performance, validated with 20% of test data that are intact during the training phase, is the main discussion point of this paper. Future works to improve the predictive accuracy of AI models is also discussed.
Additive Manufacturing of Tailored Blank for Sheet-Bulk Metal Forming Processes
Authors: Schulte R , Papke T , Lechner M , Merklein M
Published: November 2020

Functional integration and lightweight construction pose increasing demands on manufacturing processes and require innovative approaches. In this context, sheet-bulk metal forming combines the advantages of conventional sheet and bulk forming processes expanding the limitations of these particular processes. However, the intended three-dimensional material flow contains major challenges regarding the material flow control. To enhance material flow control and part quality the application of process-adapted semi-finished products is an expedient approach for sheet-bulk metal forming processes. So-called Tailored Blanks have a process-adapted sheet thickness profile or combine different mechanical properties within a single blank and were applied in the 1980s for the first time. Since then tailored approaches gained in importance and find broad application in research and industry. At present, various technologies are used to manufacture Tailored Blanks. The Tailored Blanks applied in sheet-bulk metal forming are often manufactured by sheet-bulk metal forming processes themselves. The achievable gradient in thickness depends on various factors but is eventually constraint by the material volume of the initial blank. In this regard, Additive Manufacturing offers new possibilities to overcome those limitations and to expand the limits of sheet-bulk metal forming processes further. Additional material can be allocated with high geometric flexibility. Besides the allocation of additional material, this technology allows the manufacturing of discrete functional elements within the production of Tailored Blanks. In this investigation, Tailored Blanks made out of stainless steel are produced using sheet material and additively manufactured elements. These Tailored Blanks are processed in a deep drawing and a subsequent upsetting operation to manufacture a functional component with an external gearing. Conventional sheet material is also processed to compare the resulting part properties and to evaluate the different semi-finished product strategies. For this purpose, an analysis of geometrical as well as mechanical Tailored Blank properties is conducted. Furthermore, the part properties after deep drawing and upsetting are analysed. The investigation evaluates the potential for Tailored Blanks consisting of sheet metal with additively manufactured elements in sheet-bulk metal forming and conclusively points out the need for further research in this field.
Forming and trimming of 2-mm thick DP600 sheet steel in tools and dies 3D-printed in maraging steel by laser-based powder bed fusion
Authors: Skåre Thomas , Asnafi Nader
Published: November 2020

In a previous investigation, 3D-printed solid and topology optimized semi-industrial tools for forming and trimming of 2-mm thick hot-dip galvanized DP600 were certified. This certification required 50,000 strokes in U-bend forming and 100,000 strokes in trimming/cutting/blanking. The present paper focuses on the tool wear, the U-bend sheet surfaces, the shear and fracture zone lengths in trimming, and the punch forces in this certification. The 3D-printed tools behave as conventional tools do. Although small, there seems to be a difference in wear at the profile radius between the solid and topology optimized U-bending tool halves 3D-printed in maraging steel DIN1.2709.
New Physical Scaling Approach to compensate the part contraction in drawing operations
Authors: Birkert A , Zimmermann P , Hartmann B , Scholle M , Straub M
Published: November 2020

Further increasing requirements to the quality of car body components represent a huge challenge for the process planner. Springback effects are causing dimensional deviations of the car body components from their respective target geometry. Both elastic membrane and bending stresses result in global and regional distortions and deflections. In addition to these effects in particular the membrane stresses furthermore result in a contraction of the drawshell with the effect that the drawshell is smaller than the tool after drawing. In order to compensate this contraction the drawing tool has to be increased. This process is known as the so-called scaling. An appropriate scaling should result in a contracted part which has the same surface area and unwound lengths as the target geometry. In case of deviations of the unwound lengths unwanted plastic deformations of the part in subsequent operations have to be expected and the part’s assembly dimensions will differ from the target geometry which can cause significant quality issues in the car body. Today the scaling is usually done by increasing the tool with a unique global scaling factor or with different scaling factors for different directions. However, since the contraction varies along the part surface in reality the results are only suboptimal. Here a new scaling approach is being presented which uses the simulation results to scale the tool surfaces locally. By doing so the locally different contractions can be better compensated.
Investigation on ductile fracture of an aluminium alloy using a mean-field crystal plasticity framework
Authors: Lee J , Park H , Joo M , Jeong Y
Published: November 2020

The onset of ductile fracture can be described by a simple damage parameter, which accounts for the accumulation of damage under arbitrary deformation. The damage parameter is usually given as integral form of strain over loading history which also has been described as a function of stress state. While the evolution of strain field can be experimentally determined using digital image correlation, experimental measurement of the multiaxial stress state is still a challenging task. Therefore, various uncoupled fracture criteria rely on stress states calculated from phenomenological plasticity model. As a result, the number of mechanical tests required to calibrate the fracture criterion may significantly increase when an anisotropic constitutive model is used. We propose an alternative approach on the basis of a mean field crystal plasticity (VPSC) model, which accounts for the microstructural features such as slip system, crystallographic texture and its evolution. While stress fields can be obtained from the use of full-field crystal plasticity framework, the proposed method utilizes the mean field crystal plasticity framework and repeat the stress estimation on various spatially resolved locations to which DIC technique provides strain history. The repeated VPSC calculations at various locations efficiently provide the map of stress evolution. The resulting map of spatially resolved stress response is further validated by comparing with the bulge stress strain curves.
Finite element analysis of self-piercing riveting of aluminum alloy and carbon fiber reinforced polymer composites
Authors: Hur Y C , Kim D , Lee K S , Bae M G , Park S E , Kim J H
Published: November 2020

Self-piercing riveting (SPR) is a high-speed fastening process that can join similar and dissimilar sheet materials without the need for pre-processing such as drilling or punching. During SPR processes, two overlapping sheets are joined by a rivet. The upper sheet is punched first by the rivet and then the lower sheet is deformed between the rivet and the die, creating a mechanical interlock. In this study, self-piercing riveting of aluminum alloy and carbon fiber reinforced polymer composites (CFRP) sheets was analysed using finite element simulations. For the finite element simulation of SPR processes, the orthogonal elasticity, the fracture model, and the cohesive zone model were used for describing the behaviour of CFRP. For validation of the composite material model, the punching process of CFRP was performed and the results were compared with FE predictions. The SPR process of the aluminum alloy and CFRP was simulated numerically and the performance of the joint was evaluated.
Evaluation of the stress-strain relationship in the high strain region of high strength materials by using the shear stretch test
Authors: Taguchi Y , Maeda Y , Maeda Y
Published: November 2020

Stress-strain relationships are used in FEM analysis. After uniform deformation, they are simply extended values expected from ones measured without experiment. The purpose of this research was to understand the stress-strain relationship in the high strain region after uniform deformation. We investigated a method for understanding this relationship in high strength materials using a simple shear test. The relationship in this region was calculated by determining a constant parameter κ as the coefficient between equivalent stresses and shear stresses. Using this constant, the relationship after uniform deformation was extended from the result of a stretching test. This method is called the κ method. In the case of high-strength materials, it is difficult to avoid rotating the specimen under a high testing load. Because of this problem, we designed the shape of the specimen so that it had two symmetrical deformation areas. The notch shapes for the deformation areas on the specimen were designed to reduce the load and provide a strong gripping force. In terms of shortening the deformation region, it is difficult to ignore a non-uniform deformation. To reduce the influence of non-uniform deformations, the effect of the R shape on the notch end was evaluated. The uniformity of two specimens with R1.5 mm and R7.0 mm on the notch end was examined by FEM. The values of κ, which were determined from the shear stress and shear strains based on the results of FEM, depended on the equivalent strain. In the case of R7.0 mm, the κ results were almost constant, and this was a suitable result for applying the κ method. The change in κ was affected by the non-proportional stress ratio, the stress error of the observed shear stress, and the strain error of observed shear strain. In the case of R7.0 mm, it was found that there was an advantage for the constant stress error in the higher strain region. Using R7.0 mm and R1.5 mm specimen shapes, we applied a shear test with two kinds of high-tensile steels and aluminum materials. From experimental results, the values for κ on R7.0 mm were also more constant than on R1.5 mm in the higher strain region. A high stress-strain relationship after uniform deformation was obtained in high-tensile steels and aluminum materials. This research could therefore be used to understand the stress-strain relationship in the high strain region of high strength materials.
A fully coupled damage model with stress triaxiality and Lode dependence
Authors: Zhang K , Badreddine H , Hfaiedh N , Saanouni K , Liu J
Published: November 2020

In the present work, an advanced CDM model considering stress triaxiality and Lode angle effect is proposed. The framework of thermodynamics of irreversible processes with state variables is used to build the constitutive equations accounting for strong and full coupling between all the dissipative phenomena. The proposed model is implemented into Finite Element (FE) code ABAQUS/Explicit via a user material subroutine (VUMAT). A detailed parametric study with various values of the new material parameters is conducted in order to show the predictive capability of the proposed model. Applications to sheet metal forming simulation have been performed to validate the damage prediction capability of the proposed model, and the numerical simulation results are analysed and discussed.
Distortional Hardening Behavior and Strength Different Effect of Pure Titanium Grade 1 Sheets: Experimental Observation and Constitutive Modeling
Authors: Pham Quoc Tuan , Lee Myoung Gyu , Suk Kim Young
Published: November 2020

This study presents a systematic methodology that used to identify the subsequent yield surfaces of a pure titanium grade 1 sheet at different levels of equivalent plastic work. Several experimental tests including uniaxial tensile tests (UT), hydraulic bulge test (BT), simple shear tests (SS), and uniaxial compressive tests (UC) have been conducted for samples prepared in different orientations to achieve a comprehensive experimental data of yielding behaviors observed in different forming modes. Under the condition of equivalent plastic work, the yielding behaviors are characterized and normalized to clarify the distortional hardening behavior and strength different effect for the tested material. It is seen that the yielding surface of the tested material distorts largely during plastic deformations and approaches to its final shape at an equivalent plastic work value of 40 MPa. Under the plane-stress assumption, experimental data obtained from on-axis tests (UT, BT, UC) are used to calibrate three constitutive models: Yld2k, CPB06, and CB04. Finite element analyses for a simple shear test have been performed in Abaqus/explicit software to validate the developed material models. In conclusion, the CPB06 model provides the best prediction for plastic yielding behaviors of the tested material.
Work-hardening behavior prediction model of arbitrary reloading process based on material crystallographic structure
Authors: Oya T , Yanagimoto J , Ito K , Uemura G , Mori N
Published: November 2020

In the case of complex forming process that receives a secondary loading after the primary loading, it is necessary to appropriately represent the work-hardening state according to the forming history. Namely, it is necessary to accurately model complex forming process including reversal loading (Bauschinger effect) and orthogonal loading (cross-hardening). In this study, a composite anisotropic hardening expression based on the crystallographic structure using the finite element polycrystal model is proposed. Numerical investigations are conducted to consider the effectiveness of the proposed model. In which, an alternation rate is introduced to capture the activity of the slip systems to support the idea behind the proposed model. In addition, flow curves of the secondary loading are produced by the proposed model, which is compared with the conventional model.
A novel testing method to evaluate edge formability nondestructively with eddy current
Authors: Gu J , Pathak N , Freed S , Todorov E , Kim H
Published: November 2020

Eddy current (EC) testing is one of the most extensively used NDE techniques in the automotive industry for automatic in-line inspection of ferrous materials such as advanced high strength steels (AHSS). In addition, shearing is a very common forming operation in the automotive industry. With the increase of shearing clearance, the sheared-edge experiences significant work-hardening that normally decreases the formability of the sheared edge. This paper introduces a novel and real-time monitoring NDE method based on the EC sensor to characterize variations in shear edge quality for two different grade advanced high strength steels, DP780 and 980GEN3. The developed NDE method was applied to scan the edges sheared at various clearances between 5 and 25% of the material thickness. The NDE signal received was correlated with pre-straining introduced during the shearing process at various clearances. Microhardness measurements were taken to compare the trends obtained from the NDE tool with the hardness values. To evaluate the edge formability, half-specimen dome testing (HSDT) was conducted for the edges sheared at various clearances. A digital image correlation (DIC) system was used to measure failure strain during the HSDT. The failure strain of sheared edges was correlated with the NDE measurements for each clearance to assess the application of an NDE measurement in determining edge quality. The NDE method can potentially be used to inspect the sheared edge quality for sheet metal stamping process.
Development of rapid heat solid solution process of Al 7075-T6 alloy applying near-infrared ray heater
Authors: Jung Seon-Ho , Kim Yongbae , Choi Seogou , Lee Jongsup
Published: November 2020

To improve the formability and productivity in cold forming of aluminum alloy, w-temper forming process was developed. In this process, the T6-temper blank is subjected to the solution heat treatment (SHT) and then quenched to achieve the w-temper. At present, the main problem of this process is that too long SHT time cannot meet the manufacturing cost. For example, the quenching time is 10 sec, while the SHT time is 30 min. In this paper, rapid solid solution of Al 7075-T6 alloy sheet was implemented in near-infrared ray(IR) heater. Applying IR, contact heater was developed instead of the traditional heater using cartridge heater. The results have shown that it is possible to accurately control the sheet temperature for solid solution temperature in short time. Also, compared to SHT using traditional heater, the rapidly heating using IR heater could make the mechanical properties of w-temper.
Reduced texture approach for crystal plasticity finite element method toward macroscopic engineering applications
Authors: Noh D , Yoon J W
Published: November 2020

In Crystal Plasticity Finite Element Method (CPFEM), normally over thousands Euler angles are used. It leads to high computational cost. To efficiently solve this problem, a reduced texture approach was implemented through User MATerial Interface (UMAT). Specific material parameters including the texture information were calibrated to characterize anisotropic behavior. For the calibration, it is used the stress-strain curves and r-values along the rolling, diagonal, and transverse directions. In this study, AA 2090-T3 was modelled with the reduced texture approach by characterizing 12 parameters. Single element simulation result from the reduced texture approach shows a good agreement with the experimental data. In addition, a deep drawing simulation for AA 2090-T3 was performed. The simulation results from the reduced texture approach were compared with those from the advanced constitutive models such as Yld2000-2d and Yld2004-18p in terms of accuracy and time efficiency. It shows a great potential that the reduced texture approach based on the crystal plasticity theory could be applied to macroscopic engineering problems as an alternative solution for continuum level advanced constitutive models.
Simulation of springback in cyclic wipe-bending
Authors: Bok H H , Oh K S , Kang Y S
Published: November 2020

This paper proposes a bending method to measure the robustness of advanced material constitutive models, which are developed aiming to precisely express material responses including the Bauschinger effect, permanent softening, etc. Such constitutive models, in general, require multiple sophisticated material tests, e.g. cyclic uniaxial tension-compression, followed by appropriate numerical optimizations to identify corresponding material model parameters. These tests, for example, intrinsically require anti-buckling measures for specimens that can lead to redundant frictional forces and biaxial effects. Besides, the strategy for the optimization of material parameters or the selection of elastic modulus model is also an important point to influence the final performances. In an effort to provide more robust reliability for springback simulation results, a wipe-bending tool enabling cyclic load reversals has been developed as an intermediate validator positioned between the role of the cyclic uniaxial tension-compression and that of the U-drawbending. Predicted springback results employing the Yoshida-Uemori model have shown that this approach can be considered as an effective way to confirm both the reliability of material model parameters and the capability of a selected constitutive model in a part development or tooling stage.
Experimental issues in the instrumented 3 point bending VDA238-100 test
Authors: Wagner L. , Larour P. , Dolzer D. , Leomann F. , Suppan C.
Published: November 2020

The instrumented 3-point bending test according to VDA238-100 test standard is increasingly used within the steel and automotive industry. Originally developed for aluminum hemming characterization, this bending test has been shown to be also relevant for local formability and crash foldability assessment originally of press-hardened steel grades and more recently for newly developed advanced and ultra high strength AHSS/UHSS steels grades. This instrumented bending test delivers bending load vs. bending angle curves. It is commonly assumed that material failure shortly happens beyond maximum load after a 30N load drop. The bending angle at maximum force aFmax characterizes then the bendability of the investigated material. The assumption maximum force = bending crack initiation, while being true for press-hardened grades, is in too many case not valid for steel grades with tensile strength ⩽1200MPa and cannot be universally trusted. An alternative approach is presented using passive acoustic emission sensors placed in the vicinity of the bending punch. The interpretation of such acoustic data is however quite subjective and still in trial status. Redundant crack detection systems based on load, acoustic as well as optical measurements may have to be considered together for increasing crack detection reliability within the VDA238-100 bending test specification.
Edge crack sensitivity versus tensile local ductility of AHSS sheet steels
Authors: Larour P , Freudenthaler J , Kerschbaum M , Dolzer D
Published: November 2020

There is a growing interest in correlating usual tensile testing results with edge crack sensitivity testing from punched ISO16630 hole expansion ratio HER (10mm shear cut hole, 12% clearance, conical expansion tool). A new kind of tensile local ductility parameter has been developed lately based on broken sample surface of tensile specimens after testing. Reduction in area or thickness at fracture are more sensitive than conventional fracture elongation with a 50 to 80m gage length to characterize the local ductility potential of sheet steels. A representative amount (300 different sets of samples) of cold rolled sheet steels have been tested in the tensile strength range 600-1200MPa and thickness range 1-2mm with 3 replicates in the transverse and longitudinal direction with ISO 6892-1, type 2, A80 tensile samples. Correlation levels of ISO16630 HER values with conventional tensile mechanical properties such as uniform & fracture elongation, yield & tensile strength, n-& r-values or derivatives are disappointing low for the investigated AHSS grades. There is however a massive improvement in the empirical statistical correlation when using local ductility properties based on fracture area or thickness reduction measurements on broken tensile samples. Logarithmic local ductility strains correlate generally linearly with logarithmic hole expansion ratio. Logarithmic true local ductility values are proving more suitable than engineering strains for correlations. Transverse direction improves slightly the correlation quality vs. longitudinal direction. The correlation is also higher for thickness reduction in comparison to reduction of area based properties.
A full-field optimization approach for iterative definition of yielding for non-quadratic and free shape yield models in plane strain
Authors: Hippke Holger , Berisha Bekim , Hora Pavel
Published: November 2020

An advanced strategy for iterative definition of initial yielding based on planar strain distribution is presented. It is shown that full-field DIC measurement of NTR5 samples provides information on initial yielding for plane strain. The interdependency of strain increment and yield locus under assumption of associated flow allows for definition of yield parameters using a non-linear optimization scheme with LS-OPT. Pivotal for research in direction of additional support points for definition of initial yielding was the discovery that definition of yielding based only on tensile and biaxial experiments is not sufficient for aluminum alloy. Special focus was placed on the area of generalized plane strain, which is the most critical stress state. Previous publications illustrated experimental options using cruciform tension and crystal plasticity as support points in generalized plane strain. This publication introduces an additional strategy to determine data for multiaxial stress states without need of additional experiments. The iterative strategy shows promising results for definition of yielding in generalized plane strain. Additionally, it is illustrated that common yield models such as non-quadratic YLD2000-2D and free-shape Vegter are sufficiently capable to describe yielding of aluminum alloy, if their full potential is exploited. The strategy is evaluated on the basis of Nakajima strain distributions and a conclusion is drawn on applicability and predictive capabilities.
Study on the influence of the yield surface shape in the hole expansion test
Authors: Oliveira M C , Neto D M , Alves J L , Menezes LF
Published: November 2020

The hole expansion test has become popular since it allows to study the formability of metallic sheets, in particular the onset of necking in stretch flanging areas. The accurate prediction of strain localization and consequent fracture requires a proper description of the plastic behavior, particularly the anisotropic yield function. In the context of strain localization prediction, the yield criterion adopted plays an important role, particularly when using an associated flow rule, since the direction of the plastic strain tensor is modelled by the normal to the yield surface. In this work, the parameters of an advanced yield criterion are calibrated considering a wide set of experimental data, which includes results from uniaxial and biaxial tension tests. This enables establishing yield surfaces with similar shape in the plane defined by the stress components in the rolling and transverse directions and a null shear component in the same plane. However, their shape changes slightly when considering non-null values for that shear component. The numerical simulations of the hole expansion test demonstrate the impact of these slight differences on the thickness strain distribution and, consequently, in the instant and location of the necking.
Deep drawing behavior of IN625 alloy under the influence of different process parameters
Authors: Morchhale Ayush , Kotkunde Nitin , Kumar Singh Swadesh
Published: November 2020

The Ni-Cr based IN625 alloy has been extensively used in critical applications of aerospace and nuclear industries. Various components have been manufactured using sheet metal forming processes. In the present work, the deep drawability of material has been examined under the influence of different process parameters such as temperature, punch speed, lubrication, and blank holding pressure using the processing window. The deep drawability has been analyzed in three different zones, namely, safe, wrinkling, and fracture. The limit drawing ratio increased by 7.12 % on increasing the temperature from 300K to 673K. The thickness distribution across the deep-drawn component plays a crucial role in examining the quality and life of it. Therefore, in this context, a detailed analysis of different process parameters over the drawn cup’s thickness distribution has been done. The minimum thickness was obtained near the punch corner or the cup junction region of the deep drawn cup. The uniformity in the thickness distribution and drawing height also increased with the forming temperature and decrease in punch speed. Additionally, two different yield criteria, namely, Hill 1948 and Barlat 1989, have been analyzed and further used for the numerical analysis using the user material subroutines in Abaqus software. The results predicted using Barlat 1989 yield criterion more closely followed the experimental results as the average absolute error obtained is well within the 5% of the acceptable limit.
The Utility of Next-Generation Sequencing in Advanced Breast and Gynecologic Cancers
Authors: Jones Terrell E , Zou Jian , Tseng George C , Roy Somak , Bhargava Rohit
Published: November 2020

Objectives

Next-generation sequencing (NGS) has the potential to identify genetic alterations that are actionable with targeted therapy. Our objective was to identify the impact of NGS testing on advanced breast and gynecologic malignancies.

Methods

A retrospective review of 108 patients who underwent NGS testing between 2015 and 2019 was performed. The NGS clinical action rate was calculated based on documentation of positive clinical action taken in cases with an actionable NGS result.

Results

The 108 specimens tested included 35 breast cancers and 73 gynecologic malignancies, with most of the testing performed at Foundation Medicine (90%). Actionable mutation(s) were identified in 79 (73%) of 108 cases. The overall clinical action rate of NGS testing was 38% (30 of 79 cases). Overall, 47 (44%) of 108 patients died, all succumbing to disease. The average survival was 10.9 months. The survival difference between patients with actionable NGS result and targeted treatment, actionable NGS result but no targeted treatment, and patients with nonactionable NGS result was not significant (log-rank test, P = .5160).

Conclusions

NGS testing for advanced breast and gynecologic cancers at our institution has a 38% clinical action rate. However, the increased clinical action rate over the years did not translate into improved survival.
Identification of quantitative trait loci for dynamic and steady-state photosynthetic traits in a barley mapping population
Authors: Salter William T , Li Si , Dracatos Peter M , Barbour Margaret M
Published: November 2020

Enhancing the photosynthetic induction response to fluctuating light has been suggested as a key target for improvement in crop breeding programmes, with the potential to substantially increase whole-canopy carbon assimilation and contribute to crop yield potential. Rubisco activation may be the main physiological process that will allow us to achieve such a goal. In this study, we assessed the phenotype of Rubisco activation rate in a doubled haploid (DH) barley mapping population [131 lines from a Yerong/Franklin (Y/F) cross] after a switch from moderate to saturating light. Rates of Rubisco activation were found to be highly variable across the mapping population, with a median activation rate of 0.1 min−1 in the slowest genotype and 0.74 min−1 in the fastest genotype. A unique quantitative trait locus (QTL) for Rubisco activation rate was identified on chromosome 7H. This is the first report on the identification of a QTL for Rubisco activation rate in planta and the discovery opens the door to marker-assisted breeding to improve whole-canopy photosynthesis of barley. This also suggests that genetic factors other than the previously characterized Rubisco activase (RCA) isoforms on chromosome 4H control Rubisco activity. Further strength is given to this finding as this QTL co-localized with QTLs identified for steady-state photosynthesis and stomatal conductance. Several other distinct QTLs were identified for these steady-state traits, with a common overlapping QTL on chromosome 2H, and distinct QTLs for photosynthesis and stomatal conductance identified on chromosomes 4H and 5H, respectively. Future work should aim to validate these QTLs under field conditions so that they can be used to aid plant breeding efforts.
Deep learning approaches for neural decoding across architectures and recording modalities
Authors: Livezey Jesse A , Glaser Joshua I
Published: November 2020

Decoding behavior, perception or cognitive state directly from neural signals is critical for brain–computer interface research and an important tool for systems neuroscience. In the last decade, deep learning has become the state-of-the-art method in many machine learning tasks ranging from speech recognition to image segmentation. The success of deep networks in other domains has led to a new wave of applications in neuroscience. In this article, we review deep learning approaches to neural decoding. We describe the architectures used for extracting useful features from neural recording modalities ranging from spikes to functional magnetic resonance imaging. Furthermore, we explore how deep learning has been leveraged to predict common outputs including movement, speech and vision, with a focus on how pretrained deep networks can be incorporated as priors for complex decoding targets like acoustic speech or images. Deep learning has been shown to be a useful tool for improving the accuracy and flexibility of neural decoding across a wide range of tasks, and we point out areas for future scientific development.
Tractographic and Microstructural Analysis of the Dentato-Rubro-Thalamo-Cortical Tracts in Children Using Diffusion MRI
Authors: Toescu Sebastian M , Hales Patrick W , Kaden Enrico , Lacerda Luis M , Aquilina Kristian , Clark Christopher A
Published: November 2020

The dentato-rubro-thalamo-cortical tract (DRTC) is the main outflow pathway of the cerebellum, contributing to a finely balanced corticocerebellar loop involved in cognitive and sensorimotor functions. Damage to the DRTC has been implicated in cerebellar mutism syndrome seen in up to 25% of children after cerebellar tumor resection. Multi-shell diffusion MRI (dMRI) combined with quantitative constrained spherical deconvolution tractography and multi-compartment spherical mean technique modeling was used to explore the frontocerebellar connections and microstructural signature of the DRTC in 30 healthy children. The highest density of DRTC connections were to the precentral (M1) and superior frontal gyri (F1), and from cerebellar lobules I–IV and IX. The first evidence of a topographic organization of anterograde projections to the frontal cortex at the level of the superior cerebellar peduncle (SCP) is demonstrated, with streamlines terminating in F1 lying dorsomedially in the SCP compared to those terminating in M1. The orientation dispersion entropy of DRTC regions appears to exhibit greater contrast than that shown by fractional anisotropy. Analysis of a separate reproducibility cohort demonstrates good consistency in the dMRI metrics described. These novel anatomical insights into this well-studied pathway may prove to be of clinical relevance in the surgical resection of cerebellar tumors.
Evidence of Severe Acute Respiratory Syndrome Coronavirus 2 Reinfection After Recovery from Mild Coronavirus Disease 2019
Authors: Lee Jee-Soo , Kim So Yeon , Kim Taek Soo , Hong Ki Ho , Ryoo Nam-Hee , Lee Jaehyeon , Park Jae Hyeon , Cho Sung Im , Kim Man Jin , Kim Young-gon , Kim Boram , Shin Ho Seob , Oh Hyeon Sae , Seo Myoung-Seock , Gwon Tae-Rin , Kim Yeonjae , Park Jun-Sun , Chin Bum Sik , Park Wan Beom , Park Sung Sup , Seong Moon-Woo
Published: November 2020

Background

Positive results from real-time reverse-transcription polymerase chain reaction (rRT-PCR) in recovered patients raise concern that patients who recover from coronavirus disease 2019 (COVID-19) may be at risk of reinfection. Currently, however, evidence that supports reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has not been reported.

Methods

We conducted whole-genome sequencing of the viral RNA from clinical specimens at the initial infection and at the positive retest from 6 patients who recovered from COVID-19 and retested positive for SARS-CoV-2 via rRT-PCR after recovery. A total of 13 viral RNAs from the patients’ respiratory specimens were consecutively obtained, which enabled us to characterize the difference in viral genomes between initial infection and positive retest.

Results

At the time of the positive retest, we were able to acquire a complete genome sequence from patient 1, a 21-year-old previously healthy woman. In this patient, through the phylogenetic analysis, we confirmed that the viral RNA of positive retest was clustered into a subgroup distinct from that of the initial infection, suggesting that there was a reinfection of SARS-CoV-2 with a subtype that was different from that of the primary strain. The spike protein D614G substitution that defines the clade “G” emerged in reinfection, while mutations that characterize the clade “V” (ie, nsp6 L37F and ORF3a G251V) were present at initial infection.

Conclusions

Reinfection with a genetically distinct SARS-CoV-2 strain may occur in an immunocompetent patient shortly after recovery from mild COVID-19. SARS-CoV-2 infection may not confer immunity against a different SARS-CoV-2 strain.
RecipeDB: a resource for exploring recipes
Authors: Batra Devansh , Diwan Nirav , Upadhyay Utkarsh , Kalra Jushaan Singh , Sharma Tript , Sharma Aman Kumar , Khanna Dheeraj , Marwah Jaspreet Singh , Kalathil Srilakshmi , Singh Navjot , Tuwani Rudraksh , Bagler Ganesh
Published: November 2020

Cooking is the act of turning nature into the culture, which has enabled the advent of the omnivorous human diet. The cultural wisdom of processing raw ingredients into delicious dishes is embodied in their cuisines. Recipes thus are the cultural capsules that encode elaborate cooking protocols for evoking sensory satiation as well as providing nourishment. As we stand on the verge of an epidemic of diet-linked disorders, it is eminently important to investigate the culinary correlates of recipes to probe their association with sensory responses as well as consequences for nutrition and health.

RecipeDB (https://cosylab.iiitd.edu.in/recipedb) is a structured compilation of recipes, ingredients and nutrition profiles interlinked with flavor profiles and health associations. The repertoire comprises of meticulous integration of 118 171 recipes from cuisines across the globe (6 continents, 26 geocultural regions and 74 countries), cooked using 268 processes (heat, cook, boil, simmer, bake, etc.), by blending over 20 262 diverse ingredients, which are further linked to their flavor molecules (FlavorDB), nutritional profiles (US Department of Agriculture) and empirical records of disease associations obtained from MEDLINE (DietRx). This resource is aimed at facilitating scientific explorations of the culinary space (recipe, ingredient, cooking processes/techniques, dietary styles, etc.) linked to taste (flavor profile) and health (nutrition and disease associations) attributes seeking for divergent applications.

Database URL:  https://cosylab.iiitd.edu.in/recipedb
High-frequency global wavefields for local 3-D structures by wavefield injection and extrapolation
Authors: Pienkowska Marta , Monteiller Vadim , Nissen-Meyer Tarje
Published: November 2020

Earth structure is multiscale, and seismology remains the primary means of deciphering signatures from small structures over large distances. To enable this at the highest resolution, we present a flexible injection and extrapolation type hybrid framework that couples wavefields from a pre-computed global database of accurate Green’s functions for 1-D models with a local 3-D method of choice (e.g. a spectral element or a finite-difference solver). The interface allows to embed a full 3-D domain in a spherically symmetric Earth model, tackling large-scale wave propagation with focus on localized heterogeneous complex structures. Thanks to reasonable computational costs (10k CPU hours) and storage requirements (a few TB for 1 Hz waveforms) of databases of global Green’s functions, the method provides coupling of 3-D wavefields that can reach the highest observable body-wave frequencies in the 1–4 Hz range. The framework is highly flexible and adaptable; alterations in source properties (radiation patterns and source-time function), in the source–receiver geometry, and in local domain dimensions and location can be introduced without re-running the global simulation. The once-and-for-all database approach reduces the overall computational cost by a factor of 5000–100 000 relative to a full 3-D run, provided that the local domain is of the order of tens of wavelengths in size. In this paper, we present the details of the method and its implementation, show benchmarks with a 3-D spectral element solver, discuss its setup-dependent performance and explore possible wave-propagation applications.