bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of soluble CD279 (sCD279) and CD274 (sCD274) in Iraqi patients with Acute Myeloid Leukemia (AML) with Toxoplasmosis
Authors: Issa Ali A. , Yaseen Ali N. , Aldabagh Muhammed A. H.
Published: June 2021

Toxoplasma gondii has been suggested as an important opportunistic pathogen in immunocompromised patients. Possible associations of parasite infection with cancer risk have recently attracted much attention. Published studies concerning the association between Toxoplasma gondii infection and leukemia risk have generated inconsistent results. In the present study, we aimed was to investigate the sero- prevalence of the anti-Toxoplasma
gondii IgG antibodies in Iraqi patients with Acute Myeloid Leukemia (AML) with Toxoplasmosis and to clarify the role of sCD249 and sCD274 in Iraqi AML patients with toxoplasmosis. Enzyme Linked Immunosorbent Assay (ELISA) was used to detect anti- T.
gondii IgG antibodies in the sera of 120 patients with AML and 50 apparently healthy controls. The results showed that 49(41%) samples of sera patients have been founded AML with toxoplasmosis, 71(59%) samples have AML, 20(40%) cases have control toxoplasmosis (those patients were had toxoplasmosis but showing no symptoms) and 30 (60%) cases samples were considered as a control group without any infections. Sera (sCD279 and sCD274) levels were determined by ELISA using a quantitative sandwich enzyme immunoassay technique. The results showed that levels of sCD279 and sCD274 levels were significantly higher in patients group than healthy subjects (P<0.01).
Evaluation of Hydraulic Properties of the Euphrates Aquifer in Al-Qaim Area, West of Iraq
Authors: Alsalmani Mohamed H. , Al-Shama’a Aysser M.
Published: June 2021

Three wells in Al-Qaim city (Western Desert of I), were selected to determine the hydraulic characteristics of the upper aquifer in the area by conducting pumping test operation on them. The Euphrates aquifer represents the shallow aquifer in the area where the flow direction is toward the north and northeast. The amount of hydraulic gradient was (0.036) were the groundwater flux (V) and pore velocity (U) values reached (0.35136) (8.784) m2/day respectively. Transmissivity(T), permeability(K), specific yield(Sy) and specific capacity(SC) are ranged between (656-777.9) m2/day, (7.40-11.45) m/day, (0.1-0.01) and (588.5-869.8) m2/day respectively. The obtained results show that there are no remarkable variations in the hydraulic values, which indicates the homogeneity of the aquifer in the studied area.
Influence of Fluorine Content on physical Characterization of Sprayed CdO
Authors: Agool Ibrahim R , Dawood Mohammed O , Hassan Ehssan S , Habubi Nadir Fadhil , Abdulmunem Oday M , Chiad Sami S
Published: June 2021

CdO and CdO: F films were grown using spray pyrolysis method (SPM). The effects of F doping on physical characterization were estimated using XRD, AFM and optical absorption. XRD patterns indicate that samples are cubic polycrystalline with preferred (111) orientation. AFM images assure that films consist of uniform spherical shaped grains, smooth morphology free of cracks. Optical bandgap was decreased as Fluorine doping increased
Synthesis, Characterization and Optoelectronic Properties of Solar Cells Device for Vacuum Thermally Evaporated Pure and Gallium Doped CdSe Thin Films
Authors: Agool Ibrahim R. , Mohammed Hamza M. , Abd Al Hussan Shahlaa M.
Published: June 2021

Heterojunctions n-CdSe/p-Si, n-CdSe/P-Si and CdSe:Ga/p-Si have, through thermal evaporation, been based on P-type Si (002). Thin films with different doping ratios of 1, 3 and 5 wt percent are made. For the purpose of achieving optimal conditions the electrical and photovoltaic aspects of these films have been established. Solar cell quality is graduated. They were made of a vacuum heat evaporated mixture of CdSe and ga atoms to create a thin, p-Si single wafer film with a thickness of 3.5 μm and resistivity of 0.78-1.5 Ohm-cm-2 on R.T. They are then formed by n-CdSe/p-Si and n-Cdse(Ga)/p-Si heterojunctions. The density of the existing short circuit (jsc, open-circuit (Voc/fill factor (ff)) and conversion rate of 40 mW/cm2 (AM1) intensity. The efficiency of solar cells is calculated prior to and after a Ga dopant. The aim of this analysis was to determine characterization and optoelectronic characteristics of CdSe pure and gallium-doped solar cells in thin films. The result of this analysis under dark I-V conditions show good disciplinary behavior and an exponential relationship to the potential present bias. The calculation of the C-V suggested an abrupt form of heterozone diodes. The built-in potential Vbi is calculated and is found increasing after Ga-doping process. The built-in potential and the depletion width increases with increasing of Ga doping ratio. Solar cell conversion efficiency of n-CdSe/p-Si and n-CdSe:Ga/p-Si heterojunction properties were studied is found to be 5.25 % at 5 Wt% of Ga doping ratio. In conclusions, The I-V characteristic of Ga-doped CdSe solar cell thin film under the illumination conditions gives conversion efficiency of 5.25% at doping ratio 5%. This result of conversion is directly proportional to the Ga concentrations.
Soil and Plant Nutrients Status of Salak Sidimpuan in South Tapanuli, North Sumatra Indonesia
Authors: Nasution Yusriani
Published: June 2021

Salak Sidimpuan is the superior fruit in South Tapanuli. Increased production of salak is very important to meet the needs of consumers in the South Tapanuli area and outside this area. One of the factors that can affect the increase in the quality and quantity of salak sidimpuan plant production is the provision of fertilizers in accordance with the needs of the plant. This research was conducted to determine the need for salak sidimpuan fertilizer. The method used was a survey by measuring soil and plant samples based on land units. The nutrients observed were macro (N, P, K, Ca, Mg and S) and micro (Na, Fe, Cu, Zn, Mn, B and Si) elements. Soil nutrient reserves in salak land, respectively N, P, K, Ca, Mg and S are 46.53 kgha-1, 113.84 kgha-1, 190.52 kgha-1, 183.66 kgha-1, 101, 47 kgha-1, 69.18 kgha-1. Thus, the status of soil nutrient reserves in salak land in West Angkola in the macro nutrient group is low. The status of nutrients transported to the harvest in macro nutrients is more than micro nutrients in the sequence K≫ Ca≫ N≫ Mg≫ P≫ S. The addition of nutrients to fertilization activities in salak soil is greatly recommended.
Extraction Of Silica Dioxide (SiO2) From Mount Sinabung Volcanic Ash with Coprecipitation Method
Authors: Hasanah Moraida , Sembiring Timbangen , Sebayang Kerista , Humaidi Syahrul , Rahmadsyah  , Saktisahdan Tengku Jukdin , Handoko Fauzi , Ritonga Sally Irvina
Published: June 2021

Mount Sinabung volcanic ash is a basic material that can be used to produce silicon dioxide (SiO 2). SiO 2 can be used as a building raw material as well as in food and beverage packaging. To produce SiO 2, the volcanic ash of Mount Sinabung must be synthesized using the coprecipitation method. The result of this process produces SiO 2 content as much as 48%, a formed function group that states the existence of SiO 2 namely Si-O-Si and Si-O at absorption of 1095.57 cm-1 and 798.53 cm-1. From the results of SEM can be seen the morphology of SiO 2 formed. In the XRD results, the phase of SiO 2 is amorphous.
Ecology and Disturbances in Bryophytes
Authors: Ginting Nurmaini , Batubara Melvariani Syari , Darwis Muhammad , Faradillah Vira , Santi Melia Afnida
Published: June 2021

Bryophytes is a non vascular plant that has many benefits. However, the population and diversity of its kind experienced a significant decline. This decrease is caused by several factors such as deforestation, forest fragmentation, air and soil pollution and climate change. All these factors are caused by natural activities and mainly caused by human activities that make use of the environment without preserving nature.
Investigation of the impact of heat treatment on the layer formation of AlSi-coated boron-manganese steel
Authors: He F , Merklein M
Published: June 2021

Hot stamping is a well-established technology for producing safety relevant car components. The usage of hot stamping allows for reduced sheet thicknesses and weight of formed parts due to an increase in strength because of martensitic phase transformations. To prevent surface carburization and the formation of oxide layers AlSi coatings are applied to the workpiece surface. Due to a lack of suitable lubricants at process temperatures of over 800 °C, severe friction and wear affect the final part quality. Furthermore, process temperatures influence the layer formation and surface roughness due to diffusion processes. Consequently, a deeper process understanding is needed to acquire detailed knowledge of the impact on the tribological behavior to increase part quality and reduce tool wear. To this end the influence of heat treatment parameters on the coating layer and the subsequent layer formation is analyzed by comparing the resulting material composition and surface roughness. This is achieved by analyzing the impact of the furnace temperature and holding time on an AS150 coating and determining the effect of the parameters via metallographic investigation and tactile measurement.
MBW 1200 – Hot Stamping Steel with Increased Ductility
Authors: Rosenstock D , Banik J , Rottger R P , Graff S , Gerber T
Published: June 2021

Hot stamping steels are trending towards increased ductility without sacrificing too much stiffness. Thus a new aluminum silicon coated grade, MBW 1200 + AS has been developed, with typical yield strength after hot stamping and paint baking of YS ≈ 1000 MPa, tensile strength TS ≈ 1200 MPa and A80
> 5.0 %. The highly increased ductility compared to 22MnB5 expresses through the particularly increased bending angle of >75° and the logarithmic true thickness strain of ≈0.90. Hence MBW 1200 shows the desired significantly higher ductility compared to 22MnB5 in lateral crash testing without crack appearance. The process stability has been approved by different tests, e.g. increased furnace dwell time, tool temperature and transfer time. Verifying MBW 1200 in patchwork blank applications with total thicknesses of 3.0 and 3.5 mm showed only a minor decrease of YS and TS between 30 and 50 MPa and leaves the Vickers hardness at ≈400 HV10 with fully martensitic microstructure. In partial press hardening tests, using tools heated of up to 550 °C, bending angles reach the test’s maximum and YS falls below 500 MPa with a hardness of ≈210 HV1. Finally in a comparison between experiment and numerical hot stamping simulation it can be shown, that the determined material modelling parameters can well be used in the feasibility analysis of new automotive components.
Investigation of Material Softening and Increase of Deep Drawing Capacity of 22MnB5 during Press Hardening using CRP Technology
Authors: Birnbaum P. , Xu Y. , Zhuang X. , Zhao Z. , Kraeusel V.
Published: June 2021

The cushion-ram pulsation (CRP) technology offers a significant increase in formability by the novel stepwise deep drawing with holding pauses. The influence of different incremental drawing depths and breaks on the deep drawability of 22MnB5 during press hardening with CRP is investigated for unheated and heated tools. Softening induced by the holding times during hot forming with CRP can play a relevant role in achieving higher drawing depths and is consequently described. The forming analysis is carried out by means of FE simulation and experiments. The influence of softening on the improved forming capacity can consequently be quantified and a recommendation for the CRP technology in press hardening can be determined.
Friction Characterization of Al-Si Coated Ultra-High Strength Steel under Hot Stamping Conditions
Authors: He R , DiCecco S , George R , Worswick M , Chiriac C , Luckey G , Tjong J , Shi C , Boettger J
Published: June 2021

Friction characterization of a hot stamped 1,800 MPa Al-Si coated ultra-high-strength steel (UHSS) is considered. Quantification of the coefficient of friction during a hot stamping process is essential for an accurate constitutive finite element model. The current work considers the twist compression test (TCT), in which an annular cup rotates against the surface of a fixed specimen using heated tooling. The measured sliding force and normal force determine the coefficient of friction. The test conditions used in this research simulate thermo-mechanical histories operative during hot stamping. Specimens are austenitized in a chamber furnace at a nominal temperature of 930 °C and a hold time of 5 minutes. They are then transferred to the TCT apparatus in which frictional sliding and die quenching occur simultaneously. The tooling components are uncoated and heated to 80 °C. Contact pressure of up to 30 MPa was considered between the tooling and specimen and a sliding speed of up to 38 mm/s. An increase in contact pressure caused the coefficient of friction to increase during dynamic friction. On the other hand, changes in sliding speed did not have a significant impact on the coefficient of friction. Likewise, repeated tests on the same tooling surface show that the coefficient of friction remains consistent during tool wear. Surface roughness of the tooling only increased after the first test and then remains stable during subsequent tests.
Advanced Data Acquisition for Hot Stamping and its Application
Authors: Rouet C , Trattnig G
Published: June 2021

Hot Stamping is a complex technology, which requires many control parameters. Some data may be measured in-situ, to be used for trigger purposes or just for protocol. Other data need to be measured in advance to act as sort of calibration data. At voestalpine Stahl GmbH, we utilize a hot forming simulator to support the product development of hot forming steels. Linking process parameters and product properties is a major key for successful product development. Advanced data acquisition and data processing is the tool for a better understanding, increased precision and reproducibility during hot forming, as well as for the generation and improvement of material cards. We present the measurement matrix and show how that data and the derived models can be used for the development of materials, processes, material cards and full Finite Element (FE) Models. Those models are validated on medium scale test components and results will be presented. Our intensive efforts lead to a stable and robust part production at our customers hot forming lines. Extending these methods to hot forming lines would assist process design, failure analysis and quality assurance.
Application of an Advanced Friction Model in Hot Stamping Simulations: A Numerical and Experimental Investigation of an A-Pillar Reinforcement Panel from Volvo Cars
Authors: Güner A. , Hol J. , Venema J. , Sigvant M. , Dobrowolski F. , Komodromos A. , Tekkaya A. E.
Published: June 2021

Although hot stamping is now an established method, numerical analysis of the process is still a challenge. In industrial applications, process engineers use sophisticated models which consider complex physical effects including phase transformation, phase dependent flow curves, temperature dependent r-values and temperature dependent FLC’s. However, in most of the industrial applications the tribological system is still oversimplified by using a constant Coulomb friction coefficient. Currently, there is enough experimental evidence in literature showing that friction coefficients evolve during the process, depending on contact pressure, temperature and sliding velocity. This work focuses on accurate modelling of friction in hot stamping processes. The advanced modelling technique presented in this paper tracks each material point and calculates the corresponding coefficient of friction depending on the current process conditions. This technique was used on simple part geometries in order to generate fundamental knowledge. In this analysis, part geometry, process conditions and tool kinematics are varied. In the next step, an A-Pillar reinforcement panel from Volvo Cars was analyzed experimentally and numerically. It was seen that accurate friction modelling enhances the quality of the simulation results and evolving friction conditions have a direct effect on the feasibility analysis of industrial parts.
Reduction of Young’s modulus for a wide range of steel sheet materials and its effect during springback simulation
Authors: Wagner L. , Wallner M. , Larour P. , Steineder K. , Schneider R.
Published: June 2021

Springback is among the key issues to be addressed in order to facilitate the application of AHSS in the automotive body. Since numerical simulations have become a standard tool during process design in automotive panel production, advanced material models considering springback-related material properties are increasingly getting into the focus. Next to the Bauschinger-Effect, describing early re-yielding during load reversal, also a reduction of Young’s modulus with increasing plastic strain is depicted in several material models implemented in different FEM codes. Herein, we focus on this Young’s modulus reduction. The initial Young’s modulus as well as its reduction are measured from uniaxial tensile tests with multiple unloading-reloading cycles without load reversal. Results are shown for steel sheet materials ranging from mild steels to AHSS containing retained austenite. Differences of the Young’s modulus decrease among the different steel grades are discussed with respect to their respective microstructure. Material models, depicting the Young’s modulus reduction, are fitted to the obtained data. The consequence of considering this effect during forming simulation is shown for bending-under-tension tests of DP600, representing the largest reduction.
Springback Behaviour due to Die Deflection during Bending
Authors: Tsutamori H , Nakamoto Y , Nishiwaki T
Published: June 2021

The material strength of rolled steel sheet for car bodies is increasing considerably. It has been experientially known that the die deflection affects the springback, but there are few experimental verification cases. In this study, two bending dies with different rigidity but the same shape were manufactured. The springback of panels bended by each die was compared in detail. Using 590MPa class and 980MPa class steel sheets, the deformation of the dies due to bending also measured. The springback and deflection of the die were clearly large using the low rigidity die. From these results, it was suggested that it is necessary to consider the die deflection for accurate springback prediction of bending.
Parameterized data handling for forming tool tryout: reverse engineering, data consolidation and springback compensation
Authors: Maier L , Hartmann C , Volk W
Published: June 2021

The forming tool design process generates large amounts of data up to the first falling parts. On the one hand, simulation results, geometric measurements and design models originate from different software tools, which leads to a non-consolidated set of data inventory. On the other hand, the total data volume is hard to handle economically. A stable and user-friendly data structure for overarching tool tryout is missing. Often several experience-based iterations are necessary to derive the tool’s working surfaces, which is both time- and resource consuming and even may lead to postponed start of production. Meanwhile, early-generated data does not involve into the manual optimization process. Therefore, in this paper a parameterized data handling methodology is introduced, which enables systematic reverse engineering, data consolidation, and springback compensation. Each generated dataset during tryout is traced back to a mathematical description of geometry using so called control points (B-Spline model). Through, the parameterized description, the different data formats interact straightforward and need minimum storage. The developed concept is demonstrated for the springback analysis of a forming component using design models and numerical data.
Effect of blank-holder force on springback of ultra-thin copper sheets
Authors: Ayachi’ N , Guermazi N , Manach PY
Published: June 2021

After forming by plastic deformation, it’s rare that the part produced retains its shape perfectly after removing the tools, the shape and dimensions that the tools imposed on it. This change in shape is mainly due to springback. This study focuses on the springback of U-shaped channels made of thin sheets of beryllium copper alloy 0.1 mm thick. The intensity of springback depends on several factors of part geometry and process parameters. Among the parameters of the process, we investigated the clamping force, which is an essential factor influencing the final shape of the part. It is shown that the springback is inversly proportional to the clamping force. As a consequence, there is no significant change of the geometry of the final part. Indeed, uneder high clamping force, the internal stresses (already existing in the material) become very important, which makes it possible to attenuate significantly the local moment effect in bending. The result is an uniform distribution of residual stresses in the thickness of the sheet which is studied in this paper.
Adapted part design methods for springback minimization of stamped sheet metal car body components
Authors: Birkert A , Dreiseitel F , Hartmann B , Held T , Hetterle O , Markin M , Scholle M
Published: June 2021

In sheet metal forming, both the dimensional accuracy of the manufactured parts and the robustness of the forming process are significantly compromised by elastic springback effects. In contrast to traditional compensation methods mostly relying on modifications of the tool geometry, a part geometry-based approach reduces the amount of springback by appropriately manipulating the part stiffness through slight modifications of the part geometry. To date, part-geometric measures are mostly based on practical experience and trial-and-error processes resulting in a need for simple and effective simulation-based approaches. In the present work three novel simulation-based approaches for a suitable modification of structural component design are suggested relying on unconventional topology optimization, the so-called line-of-force method and shape optimization. First tests with a classical hat profile reveal that the optimized geometries, compared to the nominal one, lead to significant reductions of the springback after stamping and simultaneously to a notable decrease of the process variation when parameters of the forming process are varied slightly. For the adapted topology optimization approach the excellent results are also confirmed when applied to the industry-relevant case of a truck rear panel.
Experimental and numerical study of springback effect of advanced high strength steel in a V-shape bending
Authors: Julsri W , Sanrutsadakorn A , Uthaisangsuk V
Published: June 2021

Advanced high strength (AHS) steel sheets are increasingly used for the production of various automotive structural parts. The components of new lightweight vehicles have very complex Shapes, for which more precise forming procedures are required in order to achieve a desired geometry. Hereby, springback occurrences of such AHS parts are often the most critical concern. In this work, it aimed to investigate springback effects of the AHS steel grade 980 in a V-shape bending process. Experimental bending test and its corresponding FE simulations were conducted. The Hill’48 and Barlat89 yield criteria, and the Yoshida-Uemori (Y-U) kinematic hardening model were applied. The yield function parameters were obtained from the tensile tests of samples in various orientations. The Y-U model parameters were determined from a cyclic tension-compression test and were afterwards calibrated with the 1-element simulation. The resulted bend angles measured from the experiment and predicted by FE simulations using the different models were compared and evaluated. For the bending in this work, the Hill’48 and Barlat89 models showed the predictive errors of springback angle 1% and 2% higher than the Y-U model, respectively. The accuracy of springback prediction could be improved by the Y-U model using C1 and C2
parameters around 1%. In addition, effects of sheet thickness and punch radius on the springback were afterwards studied and discussed by using the Y-U model.
The Effects of Piercing Methods on Burring Formability under Practical Hole Diameter
Authors: Urushibata R , Ito Y
Published: June 2021

Advanced High Strength Steels (AHSS) sheets are used for automobile bodies to comply with the demands for weight reduction and collision performance. However, as the tensile strength is increasing, the ductility of steel sheets is decreasing. Therefore the forming defects such as fractures may occur. In case of chassis components, it is needed to prevent stretch flange fractures from burring edge. There are following methods to improve burring formability. 1) Double Punching Method (DPM): punching blank coaxially with a pre-punched hole. 2) Humped bottom Punch Method (HPM): punching blank under tension using a punch with a humped part. However, there isn’t much previous evidence evaluating the burring formability of DPM and HPM under practical punching diameter for chassis components. In this study, the burring formability using DPM and HPM has been evaluated under 30mm punching diameters, through experiments and FEM analysis. The results showed that: 1) DPM: deforming mainly occurred in scrap side and equivalent plastic strain was reduced on the punched edge surface. 2) HPM: the burring formability requires both increasing stress triaxiality in blank and reducing equivalent plastic strain applied by the preceding bumped part. Under identical conditions, the same improvement effect of DPM was obtained with HPM.
Influence of pass reduction in cold rolling on damage evolution in deep drawing of rotationally symmetric cups
Authors: Nick M , Liebsch C , Müller M , Weiser IF , Hirt G , Bergs T
Published: June 2021

Improvement of component performance by controlling the damage state after metal forming enables a reduction in sheet thickness and, consequently, in component weight and material cost. To establish methods for controlling damage in finished parts, the entire process chain from steelmaking and casting through hot and cold rolling to deep drawing must be considered. Previous research has shown that in hot rolling of an S355 steel, the influence of pass reduction on damage in the hot strip disappears when the accumulated pass reduction becomes large. However, the influence of cold rolling parameters on damage and specifically on its evolution in subsequent forming processes has not yet been systematically investigated. In the present work, specimens of the the mentioned S355 steel are cold rolled with two different pass reductions and heat treated to obtain a DP800 dual phase steel. These specimens are deep drawn into rotationally symmetric cups with variation of the drawing die radius. Sheet specimens and deep drawn cups are investigated using scanning electron microscopy to determine the respective void area fractions. While no influence of height reduction on the void area fraction after cold rolling is found, the void area fraction after deep drawing differs with variation of the pass reduction. This effect is connected to the formation of a larger number of small voids in the material rolled with a larger pass reduction.
On the mechanics of edge cracking and the reliable determination of edge formability limits
Authors: Manopulo N , Chezan A R , Atzema E , Picas Anfruns I , Carleer B , Pilthammar J , Sigvant M
Published: June 2021

Blanked edge surfaces are rough and hardened. They therefore lead to inhomogeneous deformation on the edge, which can trigger localization within the shear affected zone (up to few mm from the edge). The size and extent of these phenomena are primarily a function of the shearing process and are only marginally coupled to the global/homogeneous deformation behavior of the blank. A direct numerical simulation of such local deformation effects would require a prohibitively high resolution to capture the microgeometry of the edge and thus remains unfeasible in the current industrial practice. A predictive model can therefore only be achieved by determining limit strains on the edge, which are compatible with the homogeneous numerical framework used. The present contribution aims discussing the basic mechanics of edge cracking based on tensile tests with edges blanked with different die clearances. The local and global strain evolutions in the vicinity of the edge are analysed and a new evaluation procedure is proposed for the reliable determination of limit strains. The application of this method in industrial context is also discussed.
Potentials for material card validation using an innovative tool
Authors: Eder M , Gruber M , Manopulo N , Volk W
Published: June 2021

For the numerical description of the material behavior of sheet metals, there is a large diversity of models. These models vary strongly in terms of complexity and calibration effort. Before using a material model for numerical analyses, it is essential to validate it. The paper presents an innovative tool that allows generating a well-founded database for a comprehensive validation of the yield locus description with few and simple tests: the MUC-Test (Material Under Control). The special geometry of the punch and die generates complex strain distributions in sheet metal samples during forming. The experiment covers the strain range between uniaxial and equibiaxial tension. The contribution shows the potential of this innovative tool by using the test results of three different material classes. Using numerical analyses, sensitivities of different material model parameters were investigated. Thereby, the focus lies on the curvature of the yield locus in the area between uniaxial and equibiaxial stress state.
Constitutive modelling of Usibor® 1500 sheets after intercritical quenching
Authors: Dastgiri M. S. , Thakkar R. , Shi J. , Sarraf I.S. , Green D. E.
Published: June 2021

In this study, 0.9 and 1.8 mm thick Usibor® 1500 sheets were subjected to intercritical quenching by heating to 760-930°C and quenching at a controlled rate. The tensile behavior of as-quenched Usibor® 1500 was experimentally obtained using uniaxial tension tests at strain rates ranging from 0.001 to 0.25 s−1. The constants in the hardening models, including Johnson-Cook, were optimized using a Genetic algorithm and linear regression for each condition at each strain rate. Then, these models were numerically modified to account for heat treatment dependency. Uniaxial tensile tests were simulated using the fitted models and compared to experimental flow curves and strain distribution maps to determine the accuracy of the prediction of each model. Optical microscopy was used to determine the volume fraction of each phase using image processing tools and these characteristics were used to explain the behavior of Usibor® 1500 after intercritical quenching. It was found that intercritical quenching process parameters determine the distribution and morphology of each phase and consequently the range of mechanical properties. This model can be used to simulate the deformation of hot-stamped components with tailored properties produced under controlled austenitization.
Lightweight design of an automotive lower control arm using topology optimization for forming process
Authors: Sookchanchai K , Olarnrithinun S , Uthaisangsuk V
Published: June 2021

The global environmental regulations have become very strict nowadays, thus most car manufacturers aim to fulfil such restrictions by different strategies including lightweight technologies that contain design, advanced materials and manufacturing. Hereby, optimally designed geometries of structural components needs to be conformed to their functional requirements and manufacturing process. In this work, a topology optimization (TO) was performed for weight reduction and performance improvement of a lower control arm (LCA) of vehicle suspension. First, FE simulations of the recently used LCA were performed under different load cases according to the actual application. The resulted stress distribution and overall stiffness were gathered as the baseline reference. Then, TO procedure was carried out and critical regions for load carrying were classified. In addition, the member-size constraint was applied to enable a LCA layout, which can be likely produced by metal forming process. The introduced optimization method serves as a guidance in practice for the lightweight design of other automotive stamping parts.
On the use of fixed point translations as input variable for digital twins in deep drawing compared to current methods
Authors: Ryser Matthias , Hora Pavel , Bambach Markus
Published: June 2021

Recent work aims at the inverse parameter estimation in deep drawing using pretrained surrogate models for the detection of the current process, material or tool parameters. The use of the methodology requires the definition of state variables to describe the current process state. Whereas our recent work makes use of draw-ins and local blankholder forces, other approaches from the literature also use skid-lines measured after the deep drawing process. For the future, the solution with even higher information content would be to detect the global strain distribution on the final part and use it as a state variable for process detection, which has not been documented in the literature to the best knowledge of the authors.

In this work, we present a first step into this direction by comparing the surrogate model based parameter estimation by using draw-ins and by using the movement of material fixed points on the blank over the deep drawing process. The result shows that the mathematical methods used for parameter prediction based on draw-ins can directly be used for the prediction with fixed point translations as reference. For the investigations, a cup drawing process is used.
Simulation of Dynamic Effects in Progressive Die Operation and Control
Authors: Budnick D. , Steinlehner F. , Weinschenk A. , Volk W. , Melek W. , Worswick M. , Huhn S.
Published: June 2021

The demand from the automotive industry for increasingly complex sheet metal components and higher throughput in progressive die operations has led to the increased integration of sensors and control-systems in the sheet metal forming process. However, current control-systems used in sheet metal forming are often limited to measuring the state of the tooling during the forming process, neglecting the dynamic effects of the strip during its transfer between tooling operations. Developing a control strategy that accounts for the strip dynamics requires knowledge of how various process parameters influence the strip behaviour during both the transfer and forming stages. FE element models can accurately model the behaviour of sheet metal, but by themselves cannot identify a robust control strategy. Machine learning can solve this issue by constructing a probabilistic representation for the data generated from FE simulations to be used to identify a control strategy for sheet metal forming. The goal of this work is to conduct a parametric study on a progressive die FE model and evaluate the influence of various input parameters. The data collected from this FEM study will be used to construct a neural network model that will inform a control strategy for a progressive die.
Robustness analysis with LS-OPT® and LS-DYNA® for sheet metal forming simulations
Authors: Merten M , Liebold K , Haufe A
Published: June 2021

This contribution shows the application of the optimization and probabilistic analysis program LS-OPT on the drawing step of a generic fender geometry simulated with LS-DYNA to judge on the robustness and reliability of the model. Input variables of a typical sheet forming simulation that are subject to uncertainties are alternated automatically within the framework of LS-OPT based on an inherent Monte Carlo approach. Using metamodel approximations as well as classifiers to evaluate statistical results is discussed. The influence of the variation of the input variables on typical sheet forming results is investigated, e.g. thickness reduction and the Formability Index. Alternated parameters were material properties like yield and tensile strength.
Process Linearization for Closed-Loop Control of Incremental Sheet Forming
Authors: Havinga Jos , Sikkelbein Dylan , Boogaard Ton van den
Published: June 2021

Incremental sheet forming has, despite its great flexibility, not yet been widely adopted by the forming industry, due to its limited geometric accuracy. One of the approaches to overcome this problem is the development of closed-loop control systems. Such control systems are mostly based on linearization with respect to a nominal toolpath. In this work, different approaches to create such linearized process models are reviewed. By implementing the models in a numerical simulation of a model predictive control system for incremental sheet forming, it is investigated how manufacturing accuracy is affected by the chosen linearization. Based on these results, the validity of the most commonly used linearization method is critically discussed. Furthermore, it is shown that the geometric accuracy can be improved by extending the process model with a time-varying component that contains historical information about past control actions.
Predicting springback variation and process-reliable tolerance limits of outer car-body panels by stochastic sheet metal forming simulation
Authors: Brix P. , Liewald M. , Eckstein J.
Published: June 2021

Modern car-body design entails increasing requirements for the dimensional accuracy of outer car-body panels. However, tolerance limits to be met in this regard are based on specifications from component engineering aimed at ensuring dimensional accuracy of the product, less on real structural springback behaviour of outer car-body panels. Process-reliable tolerance limits for outer car-body panels can be characterized by a bandwidth in springback variation caused by fluctuations in material characteristics and process parameters during production. Differences between assumptions from component engineering and real structural springback behaviour of outer car-body panels thus leads to avoidable iterative corrections in die manufacturing and following processes. Therefore, the goal of this research work presented in this paper is to predict springback variation potentially occurring during production already in the virtual design stage of a car-body and hence set process-reliable tolerance limits. Stochastic sheet metal forming simulation is used for prediction of springback variation. Here, deterministic multi-stage springback simulation of a sidewall panel is extended by stochastic variation of material properties and process parameters. Simulation results are validated by measurement reports from series production. Results presented show strong fit in characteristics of springback variation between stochastic simulation and series measurement reports. In future, stochastic simulation results can be fed back into component engineering, making die manufacturing and following joining and assembly processes more effective.
Thalamocortical Mechanisms Regulating the Relationship between Transient Beta Events and Human Tactile Perception
Authors: Law Robert G , Pugliese Sarah , Shin Hyeyoung , Sliva Danielle D , Lee Shane , Neymotin Samuel , Moore Christopher , Jones Stephanie R
Published: June 2021

Transient neocortical events with high spectral power in the 15–29 Hz beta band are among the most reliable predictors of sensory perception. Prestimulus beta event rates in primary somatosensory cortex correlate with sensory suppression, most effectively 100–300 ms before stimulus onset. However, the neural mechanisms underlying this perceptual association are unknown. We combined human magnetoencephalography (MEG) measurements with biophysical neural modeling to test potential cellular and circuit mechanisms that underlie observed correlations between prestimulus beta events and tactile detection. Extending prior studies, we found that simulated bursts from higher-order, nonlemniscal thalamus were sufficient to drive beta event generation and to recruit slow supragranular inhibition acting on a 300 ms timescale to suppress sensory information. Further analysis showed that the same beta-generating mechanism can lead to facilitated perception for a brief period when beta events occur simultaneously with tactile stimulation before inhibition is recruited. These findings were supported by close agreement between model-derived predictions and empirical MEG data. The postevent suppressive mechanism explains an array of studies that associate beta with decreased processing, whereas the during-event facilitatory mechanism may demand a reinterpretation of the role of beta events in the context of coincident timing.
Evaluation of Chiral Liquid Chromatographic Method for Separation and Quantification of Isomers of Brivaracetam
Authors: Choppari Thirupathi , Gunnam Srinivasu , Chennuru Lakshmi Narayana , Cherla Parameswara Murthy , Talluri M V N Kumar
Published: June 2021

A selective, sensitive and robust chiral analytical method was developed for the quantification of Brivaracetam (BRV) and its three isomers. Systematic chiral chromatographic elution process was executed in different modes on chiral columns of polysaccharide based to attain the finest condition. The analytical method was developed by utilizing immobilized polysaccharide chiral column (CHIRALPAK IG-U) with reversed phase under isocratic condition containing acetonitrile and 10 mM ammonium bicarbonate in the proportion of 40:60 (v/v). The mobile phase flow rate and column temperature were monitored at 0.3 mLmin−1 and 25°C with a resolution of more than 2.0. The eluted components from the column were processed at 212 nm UV detection. The limit of detection and limit of quantification values of BRV, 2R, 4S-Isomer, 2R, 4R-Isomer and 2S, 4S-Isomers were found to be 0.0066/0.02, 0.0035/0.0107, 0.0036/0.0109 and 0.005/0.0152 µgml−1 respectively. Precision, linearity, accuracy and robustness were conducted according to ICH guidelines and the findings were within the acceptable limits. The proposed analytical method was found to be precise, accurate and specific for the quantification of enantiomer and its diastereomers for drug product and drug substance of BRV.
Bacterial and Viral Respiratory Tract Microbiota and Host Characteristics in Adults With Lower Respiratory Tract Infections: A Case-Control Study
Authors: Haak Bastiaan W , Brands Xanthe , Davids Mark , Peters-Sengers Hessel , Kullberg Robert F J , van Houdt Robin , Hugenholtz Floor , Faber Daniël R , Zaaijer Hans L , Scicluna Brendon P , van der Poll Tom , Joost Wiersinga W
Published: June 2021

Background

Viruses and bacteria from the nasopharynx are capable of causing community-acquired pneumonia (CAP), which can be difficult to diagnose. We aimed to investigate whether shifts in the composition of these nasopharyngeal microbial communities can be used as diagnostic biomarkers for CAP in adults.

Methods

We collected nasopharyngeal swabs from adult CAP patients and controls without infection in a prospective multicenter case-control study design. We generated bacterial and viral profiles using 16S ribosomal RNA gene sequencing and multiplex polymerase chain reaction (PCR), respectively. Bacterial, viral, and clinical data were subsequently used as inputs for extremely randomized trees classification models aiming to distinguish subjects with CAP from healthy controls.

Results

We enrolled 117 cases and 48 control subjects. Cases displayed significant beta diversity differences in nasopharyngeal microbiota (P = .016, R2 = .01) compared to healthy controls. Our extremely randomized trees classification models accurately discriminated CAP caused by bacteria (area under the curve [AUC] .83), viruses (AUC .95) or mixed origin (AUC .81) from healthy control subjects. We validated this approach using a dataset of nasopharyngeal samples from 140 influenza patients and 38 controls, which yielded highly accurate (AUC .93) separation between cases and controls.

Conclusions

Relative proportions of different bacteria and viruses in the nasopharynx can be leveraged to diagnose CAP and identify etiologic agent(s) in adult patients. Such data can inform the development of a microbiota-based diagnostic panel used to identify CAP patients and causative agents from nasopharyngeal samples, potentially improving diagnostic specificity, efficiency, and antimicrobial stewardship practices.
What to make of the Kaldor-Verdoorn law?
Authors: Basu Deepankar , Budhiraja Manya
Published: June 2021

The Kaldor-Verdoorn law refers to a positive but less than one-for-one causal relationship between the growth rates of output and labour productivity. While empirical research has found that the Kaldor-Verdoorn coefficient lies between 0 and 1, the interpretation of this finding remains unclear. In this paper, we present a model to derive the Kaldor-Verdoorn law. Our results show that the Kaldor-Verdoorn coefficient is jointly determined by the elasticity of factor substitution, labour supply elasticity, the profit share and the increasing returns to scale (or demand-induced technical change) parameter. Hence, estimated Kaldor-Verdoorn coefficients cannot be used, on their own, to infer the presence of aggregate increasing returns to scale—with the exception of the benchmark case of Leontief Production technology (and steady-state analysis coupled with the assumption of Cobb-Douglas production technology). We also report a surprising result: an economy without aggregate increasing returns to scale (or without any demand-induced technical progress) can generate a Kaldor-Verdoorn coefficient that lies between 0 and 1.
Advanced lipoprotein parameters could better explain atheromatosis in non-diabetic chronic kidney disease patients
Authors: Bermudez-Lopez Marcelino , Perpiñan Hector , Amigo Nuria , Castro Eva , Alonso Nuria , Mauricio Didac , Fernandez Elvira , Valdivielso Jose M
Published: June 2021

Background

Chronic kidney disease (CKD) patients have a high burden of atheromatous cardiovascular disease (ASCVD) not fully explained by traditional lipid parameters. Lipoprotein composition and subclass particle number information could improve ASCVD risk assessment. The objective of this study is to investigate the association of advanced lipoprotein parameters with the risk of atheromatosis in a subpopulation of the NEFRONA study.

Methods

This was a cross-sectional study in 395 non-diabetic individuals (209 CKD and 186 non-diabetic and non-CKD) without statin therapy. Vascular ultrasound examination assessing 10 territories was combined with advanced lipoprotein testing performed by nuclear magnetic resonance spectroscopy. Logistic regression was used to estimate adjusted odds ratios (ORs) per 1 standard deviation increment.

Results

Atheromatosis was more prevalent in CKD patients (33.9% versus 64.6%). After adjusting for age, gender, smoking habit and CKD stage, the amount of triglycerides (TGs) within low-density lipoprotein (LDL) lipoproteins was independently and positively associated with atheromatosis [OR 1.33; 95% confidence interval (CI) 1.03–1.74; P = 0.03]. Similarly, total and medium LDL particles (LDL-Ps) showed a positive association (OR 1.29; 95% CI 1.00–1.68; P = 0.05 and OR 1.34; 95% CI 1.04–1.75; P = 0.03, respectively). TG-loaded medium LDL-Ps were higher in CKD patients compared with controls and showed an adjusted OR of 1.40 (95% CI 1.09–1.82; P = 0.01) in non-diabetic patients (CKD and non-CKD individuals). In contrast, non-diabetic CKD patients showed a similar coefficient but the significance was lost (OR 1.2; 95% CI 0.8–1.7; P = 0.359).

Conclusions

Non-diabetic CKD patients showed a higher amount of TG-loaded medium LDL-Ps compared with controls. These particles were independently associated with atheromatosis in non-diabetic patients.