bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimized dispatch of energy storage systems based on improved battery model
Authors: Zheng Wendi , Lei Kebo
Published: May 2022

Energy storage systems (ESS) are widely applied in power grids to absorb renewable energy sources, shift demands, and balance short-term electricity. However, the traditional dispatch methods ignore the battery's dynamic power limit and degradation characteristics, which leads to the mismatched power between ESS dispatch commands and the actual optimal responses, and shortened battery lifetime. This paper proposes a novel battery model to achieve an optimized dispatch of ESS. First, a model with a dynamic power limit is developed to vary the power limit with the state of charge. Second, a multi-factor degradation model is established to quantify the degradation of the battery during charging/discharging. However, the optimized model of ESS becomes nonconvex when the battery power and degradation characteristics are incorporated. In order to solve the nonconvex model with standard solvers, the proposed battery model is transformed into a nonlinear mapping function; then, a prediction–correction algorithm with a series of convex models is introduced to approximate the original nonconvex model. As shown in the case study, the proposed model achieves a more accurate allocation of ESS power and provides higher cost-effectiveness over the lifetime of ESS than the traditional one. Moreover, the introduced prediction–correction algorithm outperforms the heuristic algorithm in terms of computational time and global optimality.
Evaluation of virtual accreditation of medical specialist training sites for ophthalmology in Australia and New Zealand during the COVID-19 pandemic
Authors: Khanal Santosh , Gole Glen , Kaufman David
Published: May 2022

Objective To evaluate the suitability and acceptability of virtual training post accreditation visits conducted online for medical specialist training in ophthalmology in Australia and New Zealand. Methods A two-phase study (pilot and implementation) was conducted. In the pilot phase, an open-ended observation proforma was used by the authors to independently record their observations, which were later compared and discussed until consensus was achieved. All participants were asked to complete an online survey. A document analysis of accreditation documents was conducted. Observation data were broken down into themes and triangulated with online survey and document analysis results. In the implementation phase, the inspections were observed by one of the authors (SK) and the observation notes were discussed with other authors to obtain a contextual and consensual view. A document analysis of all accreditation-related documentation was undertaken. The documents included in the document analysis were planning and scheduling records, interview and inspection notes, training post inspection fact and document notices and accreditation reports. Finally, a post-inspection focus group of all inspectors was conducted. Results The accreditation interviews adequately addressed all relevant issues with high levels of robustness and reliability. Participants found it more difficult to discuss complex issues virtually compared with onsite visits. The virtual accreditation reports were not any different to what would be expected if a face-to-face accreditation visit had been conducted; however, it was not possible using the virtual inspection to determine the appropriateness of facilities and clinic layout to support and facilitate trainee learning and supervision. Conclusions Virtual accreditation of training posts in medical specialist training is viable in limited circumstances where there are no known complex training post-related issues and the site has not made substantial changes to clinic and theatre layout, equipment and facilities since the previous accreditation.
Process evaluation of chest camps for increased tuberculosis case finding in Punjab, Pakistan
Authors: Khan Muhammad Amir , Perveen Fouzia , Khan Muhammad Ahmar , Jameel Muhammad , Khan Nida , Tahir Zarfishan , Hadi Hussain , Khan Haroon Jehangir
Published: May 2022

Background To contribute to the World Health Organization’s End TB Strategy, the active tuberculosis (TB) case-finding approach has been proven effective. Methods A total of 66 chest camps were organised for patients in 15 selected districts in Punjab, Pakistan, in 2017. A mixed-method process evaluation was conducted in four randomly selected districts to evaluate the use of chest camps for active TB case finding to reach the maximum number of people with TB and to assess the implementation outcomes, such as effectiveness, feasibility, fidelity, and costs. Results Results indicated that 1458 attendees visited 24 chest camps in four selected districts. Among attendees, 297 presumptive cases were found and smear-tested; and 34 of the smear-tested were diagnosed as smear-positive TB patients. The prevalence of smear-positive TB patients among the chest camp participants was found to be 2.3%. The findings from interviews showed that preparation of chest camp activities, especially the involvement of community leaders, was found to be effective in achieving the desired level of attendance. The respondents found attending the chest camps for TB symptoms feasible and acceptable. The chest camp costs approximately US$280, including the pre-camp mobilisation events, whereas the cost per TB-positive patient was found to be US$197.64. Conclusions The higher number of attendees without TB symptoms, the low proportion of smear-negative case registrations; and relatively high unit cost (per patient detected) were the areas identified for further attention. The study supports the continuation of chest camp activity, with further attention required for quality and efficiency concerns.
The global potential for increased storage of carbon on land
Authors: Walker Wayne S. , Gorelik Seth R. , Cook-Patton Susan C. , Baccini Alessandro , Farina Mary K. , Solvik Kylen K. , Ellis Peter W. , Sanderman Jon , Houghton Richard A. , Leavitt Sara M. , Schwalm Christopher R. , Griscom Bronson W.
Published: May 2022

Significance

Despite increased interest in land-based carbon storage as a climate solution, there are physical limits on how much additional carbon can be incorporated into terrestrial ecosystems. To effectively determine where and how to act, jurisdictions need robust data illustrating the magnitude and distribution of opportunities to increase carbon storage, as well as information on the actions available to achieve that storage. Here, we provide globally consistent maps for directing additional carbon storage under current and future climate, as well as a framework for determining how that storage could be gained through restoration, improved management, or maintenance of woody biomass and soil organic matter. Our estimates provide an upper bound on how improved land stewardship can mitigate the climate crisis.
Theresentences in extreme southern Italy
Authors: De Angelis Alessandro , Bucci Giulia
Published: May 2022

Among the morpho-syntactic patterns by which Italo-Romance varieties codetheresentences, a peculiar structure surfaces in extreme southern varieties, particularly in Salento and in southern Calabria: this involves an invariable 3rd person form of the outcome ofhabēreas the copula, with no agreement with the postcopular nominal, the so-called pivot. Even though this pattern is attested in other Romance languages too, it proves, however, to be peculiar, insofar as it hosts top-ranking definite NPs (especially 1st and 2nd person pronouns), which are generally disallowed within ‘to have’theresentences in the Romance varieties. In the present paper, we infer that this pattern depends on the contact with Italo-Greek, which displays similar constructions, with an invariant 3rd sg. form of ‘to have’, the lack of the proform and the pivot marked as accusative. However, a diachronic investigation reveals that neither the extreme southern Italo-Romance varieties nor Italo-Greek displayed in their Medieval stage a similar construction, since both of them exhibited the definiteness effect. Sociolinguistic factors can account for how the two systems influenced each other by ruling out the definiteness effect from the respective patterns at the end of the interference process.
Enemies or obstacles?
Authors: Coll-Florit Marta , Climent Salvador
Published: May 2022

This study examines the use of metaphors of war and journey in a million-word corpus of Spanish-language blogs written by patients with severe mental disorders and by mental health professionals. Quantitative results indicate that both metaphors are more prevalent among patients than professionals, supporting the idea that they are mostly used in this context for communicating complex and emotionally intense experiences. From a qualitative perspective, our results show that patients use both metaphors to deal with exactly the same ontological elements of the situation (the disorder, symptoms, negative emotions, everyday problems, social prejudice, medical activity, people close to the patients and the patients themselves) but framing them differently. Further analysis shows that both metaphors have positive and negative uses in terms of emotions conveyed, empowerment and suitability for coping with the situation. In light of this, we conclude with a discussion of proposals promoting the positive uses of these metaphors.
Unconventional properties of engineered Au–Ag nanostructures
Authors: Saha Subham Kumar , Mondal Pritha , Vasudeva Navyashree , Mahadevu Rekha , Thapa Dev Kumar , Bhattacharyya Biswajit , Sharma Anand , Islam Saurav , Mahapatra Phanibhusan Singha , Phanindra Sai T , Channagiri Samartha A , Bellare Pavithra , Narayan Awadhesh , Ravishankar N , Patil Satish , Ghosh Arindam , Pandey Anshu
Published: May 2022

Au–Ag nanostructures comprising of ∼1 nm Ag nanoparticles embedded into an Au matrix show several unconventional optical, electric and magnetic properties. Here, we review progress made towards the preparation of these materials as well as analysis of their structure. Further, electrical and magnetic transitions in these materials are discussed. Finally, we review the properties of these materials as revealed from optical and electron microscopic probes.
Traversable wormhole solutions in the f (R) theories of gravity under the Karmarkar condition*
Authors: Malik Adnan , Mofarreh Fatemah , Zia Aqsa , Ali Akram
Published: May 2022

This paper examines traversable wormhole models in the

theories of gravity by applying the Karmarkar condition. For this purpose, we consider spherically symmetric space-time to examine the structure of wormholes. First, we investigate wormholes and their geometry using the redshift function under various conditions. Subsequently, we discuss the embedding diagram of the upper and lower universe using radial coordinates in two and three-dimensional Euclidean affine space. Three exclusive models are considered for the

theories of gravity, and the radial and tangential pressures are observed. Furthermore, by taking a definite shape function, we observe the behavior of energy conditions. We determine that energy conditions are violated, and their violation is generic and represents the presence of exotic matter. According to Einstein's field theory, the existence of wormholes is predicated on the occurrence of rare material. Hence, we conclude that our study is more realistic and stable.
Length Scale of Photospheric Granules in Solar Active Regions
Authors: Liu Yan-Xiao , Jiang Chao-Wei , Yuan Ding , Zuo Ping-Bing , Cao Wen-Da
Published: May 2022

Investigating the length scales of granules could help understand the dynamics of granules in the photosphere. In this work, we detected and identified granules in an active region near disk center observed at wavelength of TiO (7057 Å) by the 1.6 m Goode Solar Telescope (GST). By a detailed analysis of the size distribution and flatness of granules, we found a critical size that divides the granules in motions into two regimes: convection and turbulence. The length scales of granules with sizes larger than 600 km follow Gauss function and demonstrate “flat” in flatness, which reveal that these granules are dominated by convection. Those with sizes smaller than 600 km follow power-law function and behave power-law tendency in flatness, which indicate that the small granules are dominated by turbulence. Hence, for the granules in active regions, they are originally convective in large length scale, and directly become turbulent once their sizes turn to small, likely below the critical size of 600 km. Comparing with the granules in quiet regions, they evolve with the absence of the mixing motions of convection and turbulence. Such a difference is probably caused by the interaction between fluid motions and strong magnetic fields in active regions. The strong magnetic fields make high magnetic pressure which creates pressure walls and slows down the evolution of convective granules. Such walls cause convective granules extending to smaller sizes on one hand, and cause wide intergranular lanes on the other hand. The small granules isolated in such wide intergranular lanes are continually sheared, rotated by strong downflows in surroundings and hereby become turbulent.
Irregular Spatial Distributions of Spectral Line Parameters in the Middle Solar Chromosphere Revealed from Analysis of Solar Flash Mg i
b
2 Spectra
Authors: Jin Yuhang , Qu Zhongquan , Xu Zhi , Dun Guangtao , Chang Liang , Cheng Xiangming , Zhang Xiaoyu , Deng Linhua , Peng Yang
Published: May 2022

This paper presents the analytical results of solar Mg i
b
2 flash spectra, obtained by the prototype Fiber Arrayed Solar Optic Telescope in process of the 2013 Gabon total solar eclipse. The analysis reveals irregular distributions of the spectral line parameters like ratio of line source function to continuum one β, ratio of line emissivity to continuum emissivity ζ, ratio of the continuum opacity to the line opacity r
0, line center optical depth τ
0, the line width Δλ

D
, and the line-of-sight velocity v
los, while the approximately spherical symmetry can be found in the maps of integrated line intensity and continuum intensity. These irregular distributions originate from those of line profile features like the maximum intensity, the line width and line center wavelength. It is also found from the recovered line center optical depth τ
0 that in the middle chromosphere, the optical depth is not small due to non-ignorable absorption and the long light path along the line-of-sight. Finally, we show that the excessive broadening of spectral lines can be due to co-existence of multiple radiative sources with different line-of-sight velocities unresolved in one detector pixel.
Multitube monitors: a new-generation of neutron beam monitors
Authors: Lafont F. , Barkats D. , Buffet J.-C. , Cuccaro S. , Guerard B. , Lai C.-C. , Marchal J. , Pentenero J. , Sartor N. , Hall-Wilton R. , Kanaki K. , Robinson L. , Svensson P.-O.
Published: May 2022

With the renewal of many neutron science instruments and the
commissioning of new neutron facilities, there is a rising demand
for improved neutron beam monitoring systems with reduced beam
perturbations and higher counting rate capability. Fission chambers
are the most popular beam monitors; however, their use on some
instruments may be prevented by the background generated by fast
neutrons emitted during neutron captures in 235U and by
neutrons scattered in the material of the fission chamber. Multitube
detectors, on the other hand, offer a good alternative with minimum
beam perturbations. The purpose of this paper is to report and
analyse the results of the measurements performed with several
Multitubes used for beam monitoring. We show that the transparency
of Multitube beam monitors is 97.6 ± 0.4 %, and that their
detection efficiency is uniform, with a deviation from the mean
value <0.7 %. A counting rate reduction of 10 % due to pile-up
effects is measured at a rate of 550 kHz. In addition to neutron
beam intensity monitoring, the Multitube can be configured for
1-dimensional or 2-dimensional localisation. We present the
preliminary results of these additional functionalities.
Pandemics and the human-wildlife interface in Asia: land use change as a driver of zoonotic viral outbreaks
Authors: Goldstein Jenny E , Budiman Ibnu , Canny Anna , Dwipartidrisa Deborah
Published: May 2022

Pandemics have occurred with increasing frequency over the past century as global travel enables rapid cross-continental transmission of viral zoonoses such as coronaviruses and influenzas. Yet the prevalence of global pandemics is also attributable to an increase in the number of these infectious diseases originating in wildlife or domesticated animals in Asia that jump to human hosts. Through a review of scholarly literature, this article argues that three interrelated land use phenomena—biodiversity loss, urbanization, agricultural expansion and intensification—in southern China and Southeast Asia have enabled past viral zoonotic ‘spillover’ events from animals to humans and make future pandemics more likely. Furthermore, much recent scholarly literature on zoonotic disease adopts the One Health framework, which highlights interdependency between viruses, animals, ecosystems, and human health. As such, we review and critique the salience of the One Health framework for research on zoonotic disease in Asia. We suggest that to better understand land use changes enabling zoonotic disease emergence, future health-environment research could incorporate qualitative, cross-scalar political-economic and political ecological dynamics within which human-wildlife relations are embedded.
Carbon storage and sequestration rates of trees inside and outside forests in Great Britain
Authors: Zellweger Florian , Flack-Prain Sophie , Footring Joel , Wilebore Beccy , Willis Kathy J
Published: May 2022

Efforts to abate climate change heavily rely on carbon sequestration by trees. However, analyses of tree carbon dynamics often neglect trees outside of forests (TOFs) and spatially detailed information about tree carbon sequestration rates are largely missing. Here we describe a new method which combines remote sensing with forest inventory data from 127 358 sites to first estimate tree age and site productivity, which we then used to estimate carbon storage and sequestration rates for all trees inside and outside forests across Great Britain. Our models estimate carbon storage and sequestration rates with R
2 values of 0.86 and 0.56 (root-mean-square errors of 70 tCO2e ha−1 and 3.4 tCO2e ha−1 yr−1). They also reveal the important finding that 17% (165.6 MtCO2e) of the total carbon storage and 21% (3.4 MtCO2e yr−1) of the total carbon sequestration rate of all trees in Great Britain come from TOF, with particularly high contributions in England (24.3% and 34.1%), followed by Wales (12.5% and 17.6%) and Scotland (2.6% and 1.8%). Future estimates of carbon status and fluxes need to account for the significant contributions of TOF because these trees, often found in field margins and hedgerows are potentially an important carbon offset. Our novel approach enables carbon baseline assessments against which changes can be assessed at management relevant scales, improving the means to measure progress towards net zero emissions targets and associated environmental policies.
Model Analysis of Phase Transformation on Gadolinium-doped Yttrium Iron Garnet
Authors: Subawi H , Soepriyanto S , Korda A A , Prijamboedi B
Published: May 2022

The most suitable model to describe the yttrium iron garnet (YIG) sintering reaction has been evaluated in this study. The sintering reaction at the optimum temperature was predicted by the simulation method. When sintering takes place at a temperature of 1200°C, an intermediate compound of YIP is formed, then at a temperature of 1450°C the formation of YIG reaches a steady state. Sintering at 1450°C for 5 hours resulted in a YIG conversion of about 99.7%. The calculation of the activation energy value of the YIG sintering reaction was carried out based on linear regression technique using the Arrhenius plot. SCM modeling has a deviation tolerance of 0.923 and describes a two-step reaction. The SCM modeling was rated the best compared to other models, and was suitable for describing the true Gd-doped YIG sintering reaction. SCM modeling is considered to be able to describe the actual conditions of the YIG and Gd doped YIG sintering reaction.
Integrated Design and Analysis of Corrosion Rate Model on Tubular Pipe of Oil and Gas Production Well
Authors: Marbun B T H , Fadholi B Z , Sinaga S Z , Purbantanu B A
Published: May 2022

Corrosion occurrence in the oil and gas production system is an example of an unavoidable problem. This problem is caused by the presence of water and corrosive material fraction along with the produced hydrocarbon. On the way from the reservoir to the surface, the mixture between water fraction and the corrosive substance might adhere to the wall of conduit steel pipe (e.g. tubing, casing, and flowline) and can lead to corrosion on the wall. The corrosion problem can have a major impact on the economics of the production because the cost of production equipment is relatively expensive and workover operation is very costly. Therefore, planning and mitigation for a better production system need to be performed, so that the rate of corrosion can be controlled, and its economic impacts can be minimized. The purpose of this study was to create an integrated model of the corrosion rate calculation on the tubing by the Petroleum Engineering Study Program of Bandung Institute of Technology (ITB). Several terms related to the production process were considered in this model: the characteristics of the produced fluid, flow regimes, pressure and temperature conditions along the tubing, the trajectory of the well, the type of tubing material used, and the use of inhibitors. The model was developed from the model developed by C. de Waard, Liane Smith, and Mike Billingham. The corrosion rate calculation model was then validated using field data and the results were compared with the result from industrial commercial software, Electronic Corrosion Engineer (ECE®). The corrosion rate calculation model were able to predict the rate of corrosion in oil and gas wells accurately. A software-based system was created based on this integrated and accurate proven model. By using this software, the production system can be simulated and tested for various conditions, and then the result can be compared with each other to obtain the optimum fluid production rate with minimum corrosion rate. In addition, this software is capable to determine the most suitable tubing material which will be used in a given production environment and condition.
Resources Optimization in Underground Gold Mining Case Study the Kubang Cicau Gold Vein in Pongkor Area, West Java, Indonesia
Authors: Akmal M. , Widodo L.E. , Heriawan M.N. , Rosyid F.A. , Trilaksana A.R.
Published: May 2022

Mining activities are typically controlled by the smallest mining units (SMU). These SMUs comprise mining blocks with dimensions that are generally adjusted to the mining equipment used as well as various geotechnical factors. In addition to SMUs, the smallest mining decision unit (SMDU), which is a collection of several SMU blocks, is usually established. In this paper, the SMDU is represented by an underground (UG) mining panel. This paper presents the results of a study on the optimization of gold resource in SMU blocks within SMDU and cut-off grade (CoG) variations. The study focuses on how to design a panel as an SMDU that is based on a weekly production quota that defines an optimum weekly rate of production that meets processing and milling capacities. The UG mining scheme in this paper is realized using a level, a panel, and SMU blocks. The level represents the progress of the mining in a vertical direction, while the panel represents the progress of the mining in a horizontal direction. Acting as the objective functions are the ore tonnage and gold mass. In relation to the gold mass, the goal is to reach the optimum level within the SMDU and fulfill the constraint function through the number of SMU blocks within the SMDU and the range of CoG variations. The optimization process was conducted using a genetic algorithm scheme. Kubang Cicau Vein B at Pongkor Gold Mine Business Unit was selected for the case study.
Resource Assessment of Ungaran Geothermal Field Using Numerical model and Monte Carlo Simulation
Authors: Jatmiko Bambang Wahyu , Assiddiqy Muhamad Hasbi , Ediatmaja Prajamukti , Prabowo Ricky , Sutopo  , Pratama Heru Berian , Hamdani Muhamad Ridwan
Published: May 2022

A careful decision needs a comprehensive and effective way to estimate the subsurface condition and the possible resource contained in the geothermal system. Numerical model and simulation sum up the result of geoscience study and its correlation to the behavior of the subsurface fluid flows. A well-developed numerical simulation could give a thorough analysis of a geothermal system and be utilized as input parameters to apply the resource assessment method. This study applied the numerical simulation to the Ungaran geothermal field using TOUGH2 reservoir simulation software. Several parameters were referring to these simulation results and used as the input parameters to the resource assessment method using Monte Carlo simulation. The result shows that the resource value with the highest confidence is lower than the earlier resource estimation of the Ungaran Geothermal System, which is only based on geoscience study. This study gives a careful analysis to support decision-making, especially in a geothermal green field.
Petrophysics Analysis for Determination of Density Porosity and Neutron-Density Porosity on Carbonate Rock in East Java Basin
Authors: Julianti D , Fatkhan  , Dinanto E , Murtani A S
Published: May 2022

Indonesia has much potential in energy resources. The exploration and exploitation activities in Indonesia help to fulfill the energy needs in Indonesia. The exploration activities in Indonesia help to find the potential energy resources such oil and gas. Reservoir characterization with petrophysics can be applied to define the lithology, porosity, water saturation, and permeability the rock under the ground. One of the important aspect to define the reservoir is to understand the porosity of the targe reservoir. In this paper, the author will calculate the porosity in the reservoir using petrophysics analysis with density and neutron-density. The result is the neutron-density porosity giving better result than the density porosity.
Determination of Q-factor of Transmission Ground- Penetrating Radar Waves in Attenuating Media
Authors: Parnadi Wahyudi W.
Published: May 2022

Electromagnetic wave attenuation in a medium is the primary parameter for interpreting Ground-Penetrating Radar (GPR) data. This attenuation manifests in wave energy absorption and velocity dispersion, which have different behavior depending on the rock type. Knowledge of the attenuation behavior of GPR waves in distinct media is, therefore, a success key to distinguishing rock types. The Q that is inversely proportional to the absorption coefficient represents its attenuation behavior. To observe the attenuation behavior of rocks, we conducted two different stages. The first stage is simulated the attenuation behavior by creating synthetic traces as a convolution between the wavelet and the corresponding impulse response. A Q-constant model and Futterman's velocity dispersion were used for the impulse response calculation. In the second stage, Q was determined using three different Q determination methods: the amplitude decay method, the spectral ratio method, and the Equivalent Bandwidth (EBW) method. Our research shows that due to the absorption, the wave amplitude becomes lower with increasing distance at the same Q, while at the same distance, its wavelength is longer, and its amplitude becomes low. The longer the distance at the same Q value, the narrower is the bandwidth of the transmission signals. We got a similar result with a small Q at the same distance length. At the same time, its peak frequency shifted to lower frequencies. Moreover, the applicability of the three methods for the determination of Q was investigated and tested on field transmission data acquired at the test field in the Reiche-Zeche Mine Shaft near Freiberg in Germany. Our investigation result shows that the three Q-methods were successfully applied to field transmission data resulting in comparable Q values ranging from 31 to 36 for gneiss rocks.
Potential REE-Li resources in lateritic granite in Indonesian granitoid formations: A review
Authors: Syafrizal  , Rasma P , Hakim AYA
Published: May 2022

The long-term growth trajectory of numerous industries remains dependent on rare- earth elements and lithium (REE-Li) resources, even if China began restricting the supply of REE. As critical raw minerals, REE-Li resources have become a sensitive issue, with the preservation of reserves framed are concerns over protecting the country's sovereignty. REE-Li bearing minerals are surmised to have originated from granite parent rocks. The granite belt in Indonesia is extensive on the Bangka Belitung Islands, West Kalimantan, and West Sulawesi, areas associated with high levels of radioactivity. This study discusses a conceptual analysis on the presence of REE-Li in granitic rock and lateritic granite based on previous studies both in general and in the given area. The region is mineralized with REE-Li bearing minerals in granite, which are absorbed onto clay minerals from weathered granite.
Transient Hardening and R-value Behavior in Two-step Tension and Loading Reversal for DP980 Sheet
Authors: Kim M , Ha J , McNally J , Korkolis Y P
Published: May 2022

The present work deals with transient hardening and R-value behavior in two-step tension and loading reversal for an advanced high strength steel DP980. Mechanical properties under the loading paths were obtained through continuous tension-compression-tension, two-step tension and loading reversal experiments. The Yld2000-2d was employed to describe the initial yielding of DP980 1.0t through conducting monotonic tests. To characterize the transient behavior, a combined isotropic/non-linear kinematic hardening model, based on the 4-term Chaboche model, was selected. The Chaboche model was calibrated with the hardening curve in continuous tension–compression-tension loading. The transient behavior from the two-step tension and the loading reversal tests was then predicted by the model. The model performance was evaluated with the comparison of transient hardening and R-value from experiments and model predictions.
Non-Quadratic Pseudo Dual Potentials for Plastic Flow Modeling
Authors: Yang Seung-Yong , Sheng Jie , Tong Wei
Published: May 2022

The existence of dual flow potentials is well established in mathematical theory of plasticity since the seminal work by Hill in 1987. For a metal undergoing plastic flow, a flow stress potential is used to compute its plastic strain increments when the applied yield stress is known. On the other hand, the corresponding dual flow strain-rate potential is used to compute the stress on the flow surface when the plastic strain increments are given. This work examines some issues associated with plasticity modeling using non-quadratic dual flow potentials. Unlike the quadratic case where flow stress and strain-rate potentials are the exact dual to each other, it is often difficult if not impossible to obtain analytically the dual of a non-quadratic flow stress or strain-rate potential. The study instead focuses on formulating and assessing various non-quadratic pseudo dual flow potentials that approximate the actual flow surfaces in either stress or strain-rate space. The difference and connection between the yield surface and flow surface in non-associated plasticity are also investigated. Although only one of the dual flow potentials is actually needed for their applications in associated and non-associated plasticity modeling, the unique advantage of having both dual flow potentials on hand even in their pseudo forms is pointed out for new computational analyses.
Numerical analysis of AISI 321 alloy material parameters on rubber pad diaphragm forming
Authors: Barros P S , Otegi N , Galdós L , Argandoña E Sáenz de
Published: May 2022

Rubber pad diaphragm forming is a technology that uses a rigid die in conjunction with a flexible polyurethane tool and fluid pressure action in order to shape metal sheets. In this process, the action of the fluid forms a polyurethane tool, which forces the sheet to acquire the geometry of the die, being this process quite different from the classical stamping processes. The rubber tool is compatible with different die geometries, which allows a quick reconfiguration of the system, making it adequate for the production of small batches in the aeronautical sector. In this study, an advanced numerical model of the process is developed, in order to obtain a simulation that allows comprehensive understanding of the technology. An advanced characterization of the AISI 321 stainless steel is carried out, evaluating different yielding criteria. On the other side, the hyperelastic behaviour of the polyurethane rubber is taken into account. The main goal of the study has been to perform a sensitivity analysis of the sheet material parameters and to understand their influence on the final numerical results.
Die Concepts and formability for simultaneous forming of sheet metals and FRPs
Authors: Fang X F , Kloska T , Hajdarevic A
Published: May 2022

Fiber-reinforced plastics (FRPs) are increasingly being used to reinforce steel or aluminum (Al) automotive structure components. Currently, these multi-material applications are realized via three-stage manufacturing, which require the corresponding costs. Thus, a new hybrid forming technology has been developed and will be presented here. It is based on the principle of the hydro-mechanical sheet metal-forming technique and uses a heated thermoplastic FRP material (up to 280°C) in a half melting state as the pressure media to form steel or aluminum sheets. Since the sheet metals are pre-coated with an adhesion promoter, the FRPs are also joined with the sheet metal during this hybrid forming process. In this work, the die and especially the sealing concepts for hybrid forming will be introduced based on different part geometries. The formability of the sheet metals (Nakajima test) at different temperatures up to 280°C, for each two steel and Al alloys, will be presented. The hybrid formed parts were analyzed using optical method and section analysis. Good forming results were confirmed for both sheet metal and FRPs. A vehicle chassis component was successfully hybrid formed using CP-W800 steel and FRP, and a body component was produced using an Al5182 alloy and an FRP.
Investigation of the tensile response and the microstructural evolution during hot drawing of multi-layered, ultrafine-grained AA6014 sheets by thermomechanical analyzes
Authors: Zettl B , Merklein M
Published: May 2022

Mechanical strengthening of sheet material can be realized by accumulative roll bonding, which belongs to the severe plastic deformation processes. Beside fine-grain hardening also work and precipitation hardening is responsible for the rise of material strength. However, this is also accompanied by a significant decrease in ductility. Thus, the need for an enhancement of ductility is essential for a sufficient formability in later applications and was already introduced by tailored heat treatments. The challenge, however, is to realize a process temperature that leads to a degradation of dislocations and dissolution of MgSi-precipitations, without a recrystallization of the fine-grained microstructure to coarse grain sizes. In order to identify a suitable temperature range to avoid recrystallization, hot forming experiments are carried out at successive temperatures from 20 to 300°C. Tensile specimens are drawn with the thermomechanical simulator Gleeble 3500 (Dynamic Systems Inc.) aided by the strain measurement system Aramis (GOM GmbH). The aim is to investigate the dependence of the mechanical properties from the forming temperature in order to identify a temperature range, in which high strength with simultaneous enhanced ductility is maintained.
3D fracture modeling based on the coupling between damage criteria, phase field and crack propagation
Authors: Bouchard P-O , Eldahshan H , Pino Munoz D , Alves J , Perchat E
Published: May 2022

In addition to predicting the onset of fracture, some specific material forming processes require the modeling of crack propagation and the accurate prediction of the fracture surface. In such configurations, the use of the deletion element technique is not adapted since it suffers from major mesh dependency and spurious artificial volume loss. This work introduces a new alternative in which the phase field method is coupled to a 3D automatic crack initiation and propagation technique within the Forge® finite element software.
Formability of roll-formed carbon fibre reinforced metal hybrid components and its experimental validation
Authors: Hu X , Creighton C , Zhang P , Müller N , Reincke T , Taube R , Weiss M
Published: May 2022

Carbon Fibre Reinforced Metal Hybrid (CFRMH) materials that combine a sheet metal substrate with a reinforcing carbon fibre patch represent a promising solution to reduce weight while increasing the structural and crash performance of future automotive vehicles. CFRMHs cannot be formed with conventional stamping processes and at high volumes. This currently reduces their widespread application. Roll forming is increasingly used in the automobile industry for the forming of lightweight and high-strength metal structural components. The major deformation mode in roll forming is simple bending and this reduces interlaminar shear and compressive stresses that lead to fibre failure and delamination issues when stamping CFRMH sheet materials. This work analyses the potential of applying the conventional roll forming process for the manufacture of a simple top hat section shape from CFRMH sheet. For this, first, the material is produced in a hot press and then formed to shape in a laboratory roll forming facility at room temperature. Different layup sequences are tested, and component quality is analysed after roll forming by visual inspection. The results suggest that roll forming presents a promising manufacturing method for the production of automotive components from CFRMH sheets. The roll formed open shells are joined to produce crash box structure and tested in 3-point bending. The results show that depending on the fibre orientation a significant increase in weight specific strength is achieved.
Sheared edge formability characterization of cold-rolled advanced high strength steels for automotive applications
Authors: Lara A , Frómeta D , Parareda S , Casellas D , Larour P , Hinterdorfer J , Atzema E , Heuse M
Published: May 2022

Edge cracking has become a limiting factor in the use of some advanced high strength steels (AHSS) for high-performance automotive applications. This fact has motivated the development of a multitude of experimental tests for edge formability prediction over the last years. In this sense, the Hole Expansion Test (HET) according to ISO16630 has been established in the automotive industry as a standard procedure for edge cracking sensitivity ranking. However, whereas it may be useful for rapid material screening, the results are often not accurate and reliable enough. Consequently, alternative methods based on Digital Image Correlation (DIC) have been proposed aimed at improving the prediction of edge cracking occurrence during forming and obtaining useful strain data that can be implemented in forming simulations. This paper explores the applicability of different DIC-based methods, such as Half-Specimen Dome Tests, Sheared Edge Tensile Tests, and KWI hole expansion tests with a flat nosed punch, for characterizing the edge formability of three cold-rolled AHSS sheets. The results obtained from the different testing methods are compared and validated with a laboratory-scale demonstrator. Finally, the limitations and advantages of the different methods are discussed.
A Study of the Boundary Conditions in the ISO-16630 Hole Expansion Test
Authors: Barlo A , Sigvant M , Pérez L , Islam M S , Pilthammar J
Published: May 2022

As new and more advanced sheet metal materials are introduced to the market, more accurate techniques for determination of failure limits are needed. One area that needs attention is edge formability, where the ISO-16630 standardized Hole Expansion Test currently is used to express this through the Hole Expansion Ratio. Over the years, this standard has been criticized for producing a large scatter in repeated tests. This paper investigates a new setup for the Hole Expansion Test which introduces draw beads into the setup to ensure sufficient restraining of the specimen during the test in an effort to reduced the scatter. In total 62 tests of a DP800 steel alloy were executed, but a large scatter in the results were still seen. It was therefore concluded that a lack of restraining force in the Hole Expansion Test was not the primary cause of the reported scatter seen in other tests.
Modelling stamped edges in FEM breakage analyses of high-strength steel safety components
Authors: Lingbeek R A , Schalk-Kitting D , Gruschka P , Uurike M , Peetsalu P , Blome P
Published: May 2022

The development process for new safety components includes break load tests, where the component undergoes very large strains. Besides the mechanical properties of the steel, which are changed by the forming process, the break load depends on the quality of the stamped edges. Target of this paper is to investigate whether a hole-tensile test with a stamped hole can demonstrate the effects of stamped-edge quality on the load bearing capacity – and secondary, how such a test procedure can be reproduced with a multi-scale FEM procedure. A series of Hole Tensile Tests (HTT) has been performed with a HSLA steel grade. Here, only minor differences in break load and total elongation were found. The local strain just prior to breakage at the edge of the stamped hole shows remarkably high values, but little difference is found when comparing a machined sample to stamped samples. The multi-scale FEM approach was demonstrated using literature data for dual-phase steel, which is known to be more sensitive to edge cracks. Indeed, a stamped edge, which includes significant hardening and pre-damage, shows earlier fracture in this FEM calculation – however, the crack propagation, which is needed to capture the full breakage of the HTT sample, is not modelled correctly – this limits the application of the method on safety components.
Reduction of adhesive wear with use of tool coating reducing thermoelectric currents
Authors: Schrepfer A , Schott A , Tröber P , Keunecke M , Welm M , Steinlehner F , Golle R , Volk W
Published: May 2022

Blanking is one of the main processes in producing sheet metal components. The impact of adhesive wear of the blanking tools on the cost efficiency is high, especially when processing aluminum. As an influencing factor on adhesive wear in blanking, thermoelectric currents have been considered to a very small extent. Recent investigations have shown that thermoelectric currents occur in every blanking tool due to the rise of temperature in the shear zone in interaction with a difference of the material-specific Seebeck coefficients of tool and sheet metal. A reduction in the amount of wear was observed in case of a smaller difference of Seebeck coefficients and therefore lower levels of flowing thermoelectric currents. This paper follows the approach of adjusting the Seebeck coefficient of the tool material CF-H40S+ to the one of the sheet material by means of coating with CrAlN, in order to reduce the flowing thermoelectric currents and consequently adhesive wear. For this purpose, the effect of coating on the Seebeck coefficients, the thermoelectric currents during blanking as well as resulting wear quantities were investigated. Basic correlations could be revealed.
Prediction of sheared edge characteristics of advanced high strength steel
Authors: Sandin O , Hammarberg S , Parareda S , Frómeta D , Casellas D , Jonsén P
Published: May 2022

In the present work, numerical models are developed for the shearing and cutting process of advanced high strength steel-blanks which can predict the edge morphology in the shear effected zone. A damage model, based on the modified Mohr-Coulomb fracture surface, is calibrated. To increase the predictability of the numerical models, the fracture surface is fine-tuned in areas corresponding to the stress-state of cutting, a methodology called Local calibration of Fracture Surface (LCFS). Four cutting cases with varying clearance are simulated and verified with experimental tests, showing good agreement. It is thus found that the suggested methodology can simulate cutting with adequate accuracy. Furthermore, it is found that solely using plane-stress tensile specimens for calibrating the fracture surface is not enough to obtain numerical models with adequate accuracy.
Sheared Edge Formability Characterization of High Strength Aluminum Alloys at Room and Elevated Temperatures using Hole Expansion Tests
Authors: Narayanan A , George R , Cheong K , Mohamadizadeh A , Shi C , Long R , Boettcher E , Weinschenk A , Huhn S , Worswick M J , Butcher C
Published: May 2022

High strength 6000- and 7000-series aluminum alloys have significant potential for automotive light weighting due to their high strength-to-weight ratios. Alternate thermal processing routes and warm forming operations with rapid heating to 150 - 300°C are being explored to expand their forming process windows. While the constitutive and formability behavior of these alloys at elevated temperatures is an active area of research, limited data is available on their sheared edge stretchability, particularly under elevated temperature forming conditions. To this end, the influence of cutting clearance on the edge fracture limits of two precipitation hardening alloys, AA6013-T4 and AA7075-T6, and a non-heat treatable AA5182-O were first investigated at room temperature using the conical hole expansion test. A 12% clearance was found to be suitable for the three materials and used to process the hole expansion samples prior to warm forming. Microhardness tests were used to characterize the depth and severity of the shear affected zone (SAZ) for the AA7075-T6 before and after the warm forming cycle. The forming temperature was found to increase the hole expansion ratio by approximately 400%, 150%, and 520% for the AA5182-O, AA6013-T4, and AA7075-T6 respectively relative to the room temperature tests. The edge stretchability during W-temper forming of the AA6013 and AA7075 at room temperature was also assessed. It was observed that W-temper forming negatively influenced the hole expansion of AA6013 by approximately 30% relative to the T4 condition. Conversely, the hole expansion ratio for AA7075 when formed in W-temper increased by over 35% with respect to the T6 temper.