Digital twin (DT) is an emerging concept that is gaining attention in various industries. It refers to the ability to clone a physical object (PO) into a software counterpart. The softwarized object, ...termed logical object, reflects all the important properties and characteristics of the original object within a specific application context. To fully determine the expected properties of the DT, this article surveys the state-of-the-art starting from the original definition within the manufacturing industry. It takes into account related proposals emerging in other fields, namely augmented and virtual reality (e.g., avatars), multiagent systems, and virtualization. This survey thereby allows for the identification of an extensive set of DT features that point to the "softwarization" of POs. To properly consolidate a shared DT definition, a set of foundational properties is identified and proposed as a common ground outlining the essential characteristics (must-haves) of a DT. Once the DT definition has been consolidated, its technical and business value is discussed in terms of applicability and opportunities. Four application scenarios illustrate how the DT concept can be used and how some industries are applying it. The scenarios also lead to a generic DT architectural model. This analysis is then complemented by the identification of software architecture models and guidelines in order to present a general functional framework for the DT. This article, eventually, analyses a set of possible evolution paths for the DT considering its possible usage as a major enabler for the softwarization process.
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In this study, a novel virtual fields method (VFM) based on the finite element (FE) scheme, namely FE-VFM, is proposed as an inverse method for identifying the parameters of ...constitutive models. In the FE-VFM, experimentally measured full-field displacements are mapped onto FE meshes using global and local shape functions, and the internal virtual work is integrated using the Gauss quadrature rule. To validate the new method, a well-designed sensitivity study is conducted using the ideal deformation obtained from FE simulations for anisotropic linear elastic and isotropic plastic materials. In the case of anisotropic elasticity, the residuals of the internal and external virtual work are not significantly affected by the order and size of FE meshes, but the order of the numerical integration has a marginal effect on the quality of the results. Conversely, substantial impacts are obtained for the plastic case, in which the size and order of the FE meshes and the order of the numerical integration are all critical to the accuracy of identification owing to large, localized deformation. Furthermore, the concept of a pseudo-real deformation field is newly proposed as a virtual field, which improves the accuracy of the FE-VFM for optimizing the constitutive parameters of the plastic material. Finally, the inverse identification of the plastic hardening law for press-hardened steel is conducted using the FE-VFM with real experimental data. The results show that the FE-VFM can successfully reproduce the full-field displacements even with relatively low-quality full-field data if an optimum FE mesh is adopted. In addition, the simulated load–displacement curve of notch tension with FE-VFM identified hardening is in good agreement with the experimental results.
2D materials, such as graphene, exhibit great potential as functional materials for numerous novel applications due to their excellent properties. The grafting of conventional micropatterning ...techniques on new types of electronic devices is required to fully utilize the unique nature of graphene. However, the conventional lithography and polymer‐supported transfer methods often induce the contamination and damage of the graphene surface due to polymer residues and harsh wet‐transfer conditions. Herein, a novel strategy to obtain micropatterned graphene on polymer substrates using a direct curing process is demonstrated. Employing this method, entirely flexible, transparent, well‐defined self‐activated graphene sensor arrays, capable of gas discrimination without external heating, are fabricated on 4 in. wafer‐scale substrates. Finite element method simulations show the potential of this patterning technique to maximize the performance of the sensor devices when the active channels of the 2D material are suspended and nanoscaled. This study contributes considerably to the development of flexible functional electronic devices based on 2D materials.
A strategy to micropattern 2D materials on large‐scale flexible substrates using a direct polymer curing transfer method is demonstrated. Graphene microchannels on polymer substrates exhibit ultrahigh effective self‐heating under an applied bias voltage of less than 10 V. An entirely flexible and transparent chemical sensor array based on graphene micropatterns successfully discriminates gas species under the self‐activated state without external heating.
The General Data Protection Regulation (GDPR) gives control of personal data back to the owners by appointing higher requirements and obligations on service providers who manage and process personal ...data. As the verification of GDPR-compliance, handled by a supervisory authority, is irregularly conducted; it is challenging to be certified that a service provider has been continuously adhering to the GDPR. Furthermore, it is beyond the data owner's capability to perceive whether a service provider complies with the GDPR and effectively protects her personal data. This motivates us to envision a design concept for developing a GDPR-compliant personal data management platform leveraging the emerging blockchain and smart contract technologies. The goals of the platform are to provide decentralised mechanisms to both service providers and data owners for processing personal data; meanwhile, empower data provenance and transparency by leveraging advanced features of the blockchain technology. The platform enables data owners to impose data usage consent, ensures only designated parties can process personal data, and logs all data activities in an immutable distributed ledger using smart contract and cryptography techniques. By honestly participating in the platform, a service provider can be endorsed by the blockchain network that it is fully GDPR-compliant; otherwise, any violation is immutably recorded and is easily figured out by associated parties. We then demonstrate the feasibility and efficiency of the proposed design concept by developing a profile management platform implemented on top of the Hyperledger Fabric permissioned blockchain framework, following by valuable analysis and discussion.
Advanced Issues in springback Wagoner, Robert H.; Lim, Hojun; Lee, Myoung-Gyu
International journal of plasticity,
06/2013, Volume:
45
Journal Article
Peer reviewed
► Plastic constitutive equations. ► Variable Young’s modulus. ► Through-thickness integration of stress. ► Magnesium. ► Advanced high strength steels (AHSS).
For purposes of this review, springback ...is the elastically driven change of shape of a metal sheet during unloading and following forming. Scientific advances related to this topic have accelerated dramatically over roughly the last decade, since the publication of two reviews in the 2004–2006 timeframe (Wagoner, 2004; Wagoner et al., 2006). The current review focuses on the period following those publications, and on work in the first author’s laboratory. Much of this recent work can be categorized into five main topics.(1)Plastic constitutive equations(2)Variable Young’s modulus(3)Through-thickness integration of stress(4)Magnesium(5)Advanced high strength steels (AHSS)
The first two subjects are related to accurate material representation, the third to numerical procedures, and the last two to particular classes of sheet materials. The principal contributions in these areas were summarized and put into context.
The crystal plasticity finite element (CPFE) method was used to predict forming limit strains of hexagonal close‒packed (HCP) polycrystalline magnesium alloy sheets, namely AZ31 and ZE10, under an ...isothermal temperature condition. The strain rate‒dependent uniaxial tensile test data along various loading directions and an initial texture were used to determine the constitutive parameters of the crystal plasticity model. A hybrid representative volume element approach, which combines the CPFE and the Marciniak–Kuczynski model, was developed to obtain the forming limit diagram of the magnesium alloys. The predicted forming limits were in excellent agreement with the Nakazima test results. Moreover, the microscopic responses such as slip/twin activation and deformation texture changes during various loading paths from uniaxial tension to the balanced biaxial tension were comprehensively analyzed and discussed from the CPFE results to understand the underlying micro‒mechanism for the macro‒mechanical responses.
•Constitutive modeling of two Mg alloys is conducted using crystal plasticity.•A multi-scale forming limit diagram prediction scheme for HCP metals is developed.•Marciniak-Kuczynski model is coupled with crystal plasticity finite element.•Significant evolution of plastic anisotropy for Mg alloys is observed.•Forming limit diagrams of Mg alloys are reproduced by proposed modeling scheme.
•Formability and springback in cold forming of peak-aged 7075 aluminum alloy sheets.•Anisotropic hardening under loading path changes were modeled.•Improved formability and lowered springback with ...heat-treated 7075 aluminum alloy sheets.•The analysis on Formability prediction using MK model by considering serrated flow.
High strength aluminum alloys have drawn much attention as the requirement for lightweight vehicle design increases in the automotive industry. However, inferior formability due to higher strength poses a technical hurdle against successful application of high strength aluminum sheets in automotive components. In this study, the mechanical properties of 7075 aluminum alloy sheet after W-temper heat treatment, which consists of solution heat treatment and subsequent quenching, are investigated. Detailed experimental and numerical studies are conducted on the anisotropy, non-proportional deformation behavior, and corresponding constitutive modeling in comparison with the corresponding characteristics of peak aged T6 heat-treated as-received alloy sheets. Based on the experimentally characterized mechanical properties and associated constitutive laws, the formability and springback of the W-tempered sheet are analyzed using the Marciniak–Kuczyinski forming limit diagram and U-draw bending springback simulations, respectively, by employing the Yld2000-2d anisotropic yield function and distortional hardening-based homogeneous anisotropic hardening model. Additionally, the improved constitutive modeling of the W-tempered 7075 aluminum sheets due to the effect of serrated flow characteristics on the hardening and frictional behaviors is discussed.
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In this study, a U-shaped channel formed using a double drawing process (double stage U-draw bending) was proposed to reduce the amount of springback in the AHSS sheets. The performance of the double ...stage U-draw bending process in reducing the amount of springback was compared with that of the conventional U-draw bending process. The process was simulated using a finite element (FE) analysis with two different types of anisotropic hardening models, namely, isotropic-kinematic and distortional models, to describe the Bauschinger effect and associated anisotropic hardening transients during the strain-path changes. Moreover, plastic anisotropy, captured by different yield functions, and the degradation of the elastic modulus were taken into account. In addition to the basic mechanical characterization tests conducted to identify the material coefficients, in-plane compression–tension experiments were conducted. The experimental and FE simulated results of the double stage U-draw bending process were compared and analyzed to understand the effect of anisotropic hardening on the springback under non-proportional loading.
•LDR and fracture cup height was experimentally evaluated for different sheet materials.•Necking and fracture limits were theoretically estimated using MK and BW model.•LDR, thinning profile ...estimated using MK model incorporating anisotropy yield theory.•Anisotropic BW curve was used into GISSMO platform to predict fracture cup height.•PEPS based failure limits used to identify necking and fracture of pre-strained sheet.
In this study, experimental and numerical investigations were conducted to predict the formability and fracture behavior of as-received and pre-strained sheet materials during deep drawing process. In this context, various laboratory scale experimental setups were developed to impart different types and amounts of pre-strain such as 5% and 10% equi-biaxial pre-strains (5% EBP and 10% EBP), 10% plane strain pre-strain (10% PSP), and 10% uni-axial pre-strain (10% UP) on the extra deep drawing (EDD) steel and aluminum alloy (AA5052) sheets of 1.2 mm thickness. Further, all the pre-strained sheet samples were deformed using a cylindrical deep drawing setup. The forming limit diagrams (FLDs) of as-received sheets were predicted by the Marciniak–Kuczyński (MK) model incorporating different anisotropic yield functions such as Hill48 models identified based on r-values (Hill48-r), and yield stresses (Hill48-σ), and the non-quadratic plane stress Yld2000-2d model. Also, the Bao–Wierzbicki (BW) fracture curve was calibrated using different anisotropic yield functions. Subsequently, the formability in terms of limiting drawing ratio (LDR) was predicted using the MK-FLD. The BW fracture curve was incorporated into the generalized incremental stress state dependent damage model (GISSMO) platform in LS-Dyna software and the fracture behavior was predicted in terms of failure location and cup height at the onset of fracture. It was also found that the incorporation of Barlat Yld2000-2d yield function into the FE simulation efficiently predicted the necking and fracture behavior of as-received sheets. Furthermore, the concept of path independent polar effective plastic strain (PEPS) based failure model was used to predict LDR, thinning profile and fracture cup height of all the different pre-strained sheets. Finally, the strain paths and experimental fracture strains were plotted in 3D fracture locus to get insight into the deformation behavior during the deep drawing experiments.
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The effects of the stress state and temperature on the martensitic phase transformation behavior in a TRIP-assisted steel (TRIP780) were investigated using multi-axial experimental techniques. For ...this purpose, five different stress states were considered; i.e., uniaxial tension, uniaxial compression, equi-biaxial tension, plane strain tension and simple shear. A range of temperatures from room to 100°C for each stress state condition except the simple shear test were investigated. In particular, for the equi-biaxial tension data in warm conditions, a specially designed hydraulic bulge experiment was adopted. In situ magnetic measurements were performed to monitor the evolution of the martensitic content throughout each experiment. A stress state and temperature dependent transformation kinetics law was proposed, which incorporates a non-linear function of the stress triaxiality, Lode angle parameter and temperature. This new model captures the measured martensitic phase transformation kinetics of TRIP780 steel over a wide range of stress states and temperature reasonably well.
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