bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Q-factor of Transmission Ground- Penetrating Radar Waves in Attenuating Media
Authors: Parnadi Wahyudi W. 
Published: May 2022

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractIn 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractHigh 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.
Prediction of forming limit curve for AA6061-T6 at room and elevated temperatures
Authors: Kacem Ahmed , Laurent Hervé , Thuillier Sandrine 
Published: May 2022

Abstract
Forming Limit Curve (FLC) has been widely adopted as a practical criterion for evaluating the formability of sheet metals. Predicting a reliable FLC by a virtual methodology could lead to robust process optimization before expensive tool manufacturing. In order to increase the predictive capabilities of the virtual forming tools, an accurate modeling of the forming limit curve should be considered at room and elevated temperatures. In this work, the isothermal forming limit curves of 6000 series aluminum alloy sheet metal are predicted by performing numerical simulations of Nakajima test. A stress triaxiality and Lode angle based ductile fracture criterion is used to determine the forming limit curve. Also, the ductile fracture criterion is extended to add the impact of temperature on ductile fracture prediction. The hybrid experimental-numerical approach is used to calibrate the ductile fracture criterion. The forming limit curve of AA6061-T6 sheet metal, with a thickness of 1 mm, is predicted using the calibrated ductile fracture criterion at room and elevated temperatures. Numerical simulations are performed in 3D with the finite element code Abaqus. The limit strains are determined for specimens undergoing deformation under different strain paths. Influence of temperature on the predicted forming limit curve is discussed.
An alternative time-based strategy for the evaluation of forming limits using optical experimental measurements
Authors: Karadogan Celalettin , Görz Marcel , Liewald Mathias , Bühler Marco 
Published: May 2022

Abstract
Optical measuring systems allow to observe the sheet metal instability more precisely. The section method was first standardised and made available in commercial measurement systems in order to evaluate the forming limit curves almost automatically. The insignificant contribution of the necking area to the evaluated critical strains compared to the neighbouring volume of material led to alternative approaches such as the time-based evaluation criteria. The majority of these criteria take into account the strain evolution at the material necking location and are also suitable for evaluating other types of limits such as edge-crack sensitivity. Some advanced high-strength steels typically exhibit very short deformation after the onset of instability, which complicates the application of time-based approaches because they require sufficient amount of deformation after necking. The proposed approach is an attempt to reduce the dependence of the time-based approaches on the amount of deformation after necking by taking into account the local characteristics of the measurement curves. The approach is applied to some advanced high-strength steels to evaluate the forming instability and edge-crack sensitivity. The superiority of this identification approach is demonstrated in this paper by comparison with classical time-based approaches.