J.I.V. Sena, R.J. Alves de Sousa and R.A.F. Valente
Incremental sheet forming represents a promising process in the manufacturing of metallic components, particularly its variant known as single point incremental forming (SPIF)…
Abstract
Purpose
Incremental sheet forming represents a promising process in the manufacturing of metallic components, particularly its variant known as single point incremental forming (SPIF). The purpose of this paper is to test and validate the results coming from numerical simulation of SPIF processes using the reduced enhanced solid‐shell formulation, when compared to the solid finite elements available in ABAQUS software. The use of SPIF techniques in the production of small batch components has a potential wide application in fields such as rapid prototyping and biomechanical devices.
Design/methodology/approach
Incremental forming processes differ from conventional stamping by not using a press and by requiring a lower number of tools, since no dedicated punches and dies are necessary, which lowers the overall production costs. In addition, it shows relative simplicity and flexible setup for complex parts, when compared with conventional technologies. However, the low speed of production and low‐dimensional accuracy levels are still the main obstacles for a wider application of this technique in the context of large production batches.
Findings
In this sense, the use of numerical simulation tools based on the finite element method (FEM) can provide a better understanding of the process' peculiarities. However, there are differences on using distinct finite element formulations, regarding accuracy as well as CPU times during simulations, which can be prohibitive in some cases.
Originality/value
Aiming to provide sounding improvements in these two fields (robustness and cost effectiveness of FEM solutions), the present work encloses a preliminary study about some relevant parameters in the FEM simulation of SPIF. Special focus is given to the use of solid‐shell and solid finite elements, for the sake of generality in modelling, as well as implicit solution schemes for the sake of accuracy. Finally, results coming from both experimental data and commercial FEM packages are compared to those obtained by a reliable and cost‐effective solid‐shell finite element formulation developed and implemented by the authors.
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José I.V. Sena, Cedric Lequesne, L Duchene, Anne-Marie Habraken, Robertt A.F. Valente and Ricardo J Alves de Sousa
Numerical simulation of the single point incremental forming (SPIF) processes can be very demanding and time consuming due to the constantly changing contact conditions between…
Abstract
Purpose
Numerical simulation of the single point incremental forming (SPIF) processes can be very demanding and time consuming due to the constantly changing contact conditions between the tool and the sheet surface, as well as the nonlinear material behaviour combined with non-monotonic strain paths. The purpose of this paper is to propose an adaptive remeshing technique implemented in the in-house implicit finite element code LAGAMINE, to reduce the simulation time. This remeshing technique automatically refines only a portion of the sheet mesh in vicinity of the tool, therefore following the tool motion. As a result, refined meshes are avoided and consequently the total CPU time can be drastically reduced.
Design/methodology/approach
SPIF is a dieless manufacturing process in which a sheet is deformed by using a tool with a spherical tip. This dieless feature makes the process appropriate for rapid-prototyping and allows for an innovative possibility to reduce overall costs for small batches, since the process can be performed in a rapid and economic way without expensive tooling. As a consequence, research interest related to SPIF process has been growing over the last years.
Findings
In this work, the proposed automatic refinement technique is applied within a reduced enhanced solid-shell framework to further improve numerical efficiency. In this sense, the use of a hexahedral finite element allows the possibility to use general 3D constitutive laws. Additionally, a direct consideration of thickness variations, double-sided contact conditions and evaluation of all components of the stress field are available with solid-shell and not with shell elements. Additionally, validations by means of benchmarks are carried out, with comparisons against experimental results.
Originality/value
It is worth noting that no previous work has been carried out using remeshing strategies combined with hexahedral elements in order to improve the computational efficiency resorting to an implicit scheme, which makes this work innovative. Finally, it has been shown that it is possible to perform accurate and efficient finite element simulations of SPIF process, resorting to implicit analysis and continuum elements. This is definitively a step-forward on the state-of-art in this field.
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Abdessalem Hajlaoui, Elouni Chebbi, Mondher Wali and Fakhreddine Dammak
This paper aims to study the static behavior of carbon nanotubes (CNTs) reinforced functionally graded shells using an efficient solid-shell element with parabolic transverse…
Abstract
Purpose
This paper aims to study the static behavior of carbon nanotubes (CNTs) reinforced functionally graded shells using an efficient solid-shell element with parabolic transverse shear strain. Four different types of reinforcement along the thickness are considered.
Design/methodology/approach
Furthermore, the developed solid-shell element allows an efficient and accurate analysis of CNT-reinforced functionally graded shells under linear static conditions.
Findings
The validity and accuracy of the developed solid-shell element are illustrated through the solution of deflection and stress distribution problems of shell structures taken from the literature. The influences of some geometrical and material parameters on the static behavior of shell structures are discussed.
Originality/value
The finite element formulation is based on a modified first-order enhanced solid-shell element formulation with an imposed parabolic shear strain distribution through the shell thickness in the compatible strain part. This formulation guarantees a zero transverse shear stress on the top and bottom surfaces of the shell and the shear correction factors is no longer needed.
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Usman Tariq, Ranjit Joy, Sung-Heng Wu, Muhammad Arif Mahmood, Asad Waqar Malik and Frank Liou
This study aims to discuss the state-of-the-art digital factory (DF) development combining digital twins (DTs), sensing devices, laser additive manufacturing (LAM) and subtractive…
Abstract
Purpose
This study aims to discuss the state-of-the-art digital factory (DF) development combining digital twins (DTs), sensing devices, laser additive manufacturing (LAM) and subtractive manufacturing (SM) processes. The current shortcomings and outlook of the DF also have been highlighted. A DF is a state-of-the-art manufacturing facility that uses innovative technologies, including automation, artificial intelligence (AI), the Internet of Things, additive manufacturing (AM), SM, hybrid manufacturing (HM), sensors for real-time feedback and control, and a DT, to streamline and improve manufacturing operations.
Design/methodology/approach
This study presents a novel perspective on DF development using laser-based AM, SM, sensors and DTs. Recent developments in laser-based AM, SM, sensors and DTs have been compiled. This study has been developed using systematic reviews and meta-analyses (PRISMA) guidelines, discussing literature on the DTs for laser-based AM, particularly laser powder bed fusion and direct energy deposition, in-situ monitoring and control equipment, SM and HM. The principal goal of this study is to highlight the aspects of DF and its development using existing techniques.
Findings
A comprehensive literature review finds a substantial lack of complete techniques that incorporate cyber-physical systems, advanced data analytics, AI, standardized interoperability, human–machine cooperation and scalable adaptability. The suggested DF effectively fills this void by integrating cyber-physical system components, including DT, AM, SM and sensors into the manufacturing process. Using sophisticated data analytics and AI algorithms, the DF facilitates real-time data analysis, predictive maintenance, quality control and optimal resource allocation. In addition, the suggested DF ensures interoperability between diverse devices and systems by emphasizing standardized communication protocols and interfaces. The modular and adaptable architecture of the DF enables scalability and adaptation, allowing for rapid reaction to market conditions.
Originality/value
Based on the need of DF, this review presents a comprehensive approach to DF development using DTs, sensing devices, LAM and SM processes and provides current progress in this domain.
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Qing Xie, Yucai Hu, Yexin Zhou and Wanshui Han
Poor bending response is a major shortcoming of lower-order elements due to excessive representation of shear stress/strain field. Advanced finite element (FE) formulations for…
Abstract
Purpose
Poor bending response is a major shortcoming of lower-order elements due to excessive representation of shear stress/strain field. Advanced finite element (FE) formulations for classical elasticity enhance the bending response by either nullifying or filtering some of the symmetric shear stress/strain modes. Nevertheless, the stress/strain field in Cosserat elasticity is asymmetric; consequently any attempt to nullify or filter the anti-symmetric shear stress/strain modes may lead to failure in the constant couple-stress patch test where the anti-symmetric shear stress/strain field is linear. This paper aims at enhancing the bending response of lower-order elements for Cosserat elasticity problems.
Design/methodology/approach
A four-node quadrilateral and an eight-node hexahedron are formulated by hybrid-stress approach. The symmetric stress is assumed as those of Pian and Sumihara and Pian and Tong. The anti-symmetric stress components are first assumed to be completely linear in order to pass the constant couple-stress patch test. The linear modes are then constrained with respect to the prescribed body-couple via the equilibrium conditions.
Findings
Numerical tests show that the hybrid elements can strictly pass the constant couple-stress patch test and are markedly more accurate than the conventional elements as well as the incompatible elements for bending problems in Cosserat elasticity.
Originality/value
This paper proposes a hybrid FE formulation to improve the bending response of four-node quadrilateral and eight-node hexahedral elements for Cosserat elasticity problems without compromising the constant couple-stress patch test.
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Claire Sinnema, Alan J. Daly, Joelle Rodway, Darren Hannah, Rachel Cann and Yi-Hwa Liou
Business sustainability urges firms to simultaneously address economic, ecological, and social concerns. It innately combines different potentially competing organizational…
Abstract
Business sustainability urges firms to simultaneously address economic, ecological, and social concerns. It innately combines different potentially competing organizational elements. Therefore, sustainability represents a suitable context for the study and practice of hybridity. Based on an understanding of hybridity as a continuum, in this chapter, the author distinguish between four different forms of hybridity for business sustainability, depending on the degree of integration and autonomy of sustainability initiatives in business organizations. With ceremonial hybridity, businesses only leave the impression to pursue business and sustainability goals but focus their practices on conventional business priorities. Contingent hybridity denotes an approach where ecological and social concerns are only pursued to the extent that they align with business goals. With peripheral hybridity, firms pursue sustainability initiatives in their own right but do not integrate them with core business activities. Full hybridity puts both business as well as sustainability at the core of the organization without emphasizing one over the other. These different forms of hybridity in business sustainability are illustrated with examples from various business organizations. By characterizing different degrees of hybridity in business sustainability, the argument and the examples highlight how organizational hybridity and business sustainability can fruitfully inform one another. The author develop research opportunities for using business sustainability as a context for studying different degrees as well as the dynamics of hybrid organizing and for using different degrees of hybridity for achieving a better understanding of different pathways toward substantive business contributions to sustainable development.
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Panayiotis F. Diamandis, Anastassios A. Drakos and Georgios P. Kouretas
The purpose of this paper is to provide an extensive review of the monetary model of exchange rate determination which is the main theoretical framework on analyzing exchange rate…
Abstract
Purpose
The purpose of this paper is to provide an extensive review of the monetary model of exchange rate determination which is the main theoretical framework on analyzing exchange rate behavior over the last 40 years. Furthermore, we test the flexible price monetarist variant and the sticky price Keynesian variant of the monetary model. We conduct our analysis employing a sample of 14 advanced economies using annual data spanning the period 1880–2012.
Design/methodology/approach
The theoretical background of the paper relies on the monetary model to the exchange rate determination. We provide a thorough econometric analysis using a battery of unit root and cointegration testing techniques. We test the price-flexible monetarist version and the sticky-price version of the model using annual data from 1880 to 2012 for a group of industrialized countries.
Findings
We provide strong evidence of the existence of a nonlinear relationship between exchange rates and fundamentals. Therefore, we model the time-varying nature of this relationship by allowing for Markov regime switches for the exchange rate regimes. Modeling exchange rates within this context can be motivated by the fact that the change in regime should be considered as a random event and not predictable. These results show that linearity is rejected in favor of an MS-VECM specification which forms statistically an adequate representation of the data. Two regimes are implied by the model; the one of the estimated regimes describes the monetary model whereas the other matches in most cases the constant coefficient model with wrong signs. Furthermore it is shown that depending on the nominal exchange rate regime in operation, the adjustment to the long run implied by the monetary model of the exchange rate determination came either from the exchange rate or from the monetary fundamentals. Moreover, based on a Regime Classification Measure, we showed that our chosen Markov-switching specification performed well in distinguishing between the two regimes for all cases. Finally, it is shown that fundamentals are not only significant within each regime but are also significant for the switches between the two regimes.
Practical implications
The results are of interest to practitioners and policy makers since understanding the evolution and determination of exchange rates is of crucial importance. Furthermore, our results are linked to forecasting performance of exchange rate models.
Originality/value
The present analysis extends previous analyses on exchange rate determination and it provides further support in favor of the monetary model as a long-run framework to understand the evolution of exchange rates.