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Hui Long - One of the best experts on this subject based on the ideXlab platform.
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A review on material fracture mechanism in incremental Sheet Forming
The International Journal of Advanced Manufacturing Technology, 2019Co-Authors: Sheng Ai, Hui LongAbstract:In incremental Sheet Forming (ISF), including single point incremental Forming (SPIF) and double side incremental Forming (DSIF), the material formability can be significantly enhanced when compared with conventional Sheet Forming processes. The material deformation in ISF is far more complicated because of the combined material deformation under stretching, bending, shearing, and cyclic loading, with an additional effect of compression in DSIF. Despite extensive investigation on material deformation during ISF, no theory has yet been widely agreed to explain different types of the material fracture behavior observed in ISF experiments. This paper presents a comprehensive review on the formability enhancement in ISF and proposes possible fracture mechanisms explaining the different types of fracture behavior observed in the experimental investigations. Discussions are presented to outline the current research progress and possible solutions to overcome the current ISF process limitations because of the material processing failure due to fracture.
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Thickness control in a new flexible hybrid incremental Sheet Forming process
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2017Co-Authors: Huan Zhang, J. Chen, Feng Sule, Hui LongAbstract:Incremental Sheet Forming is a cost-effective process for rapid manufacturing of Sheet metal products. However, incremental Sheet Forming also has some limitations such as severe Sheet thinning and long processing time. These limitations hamper the Forming part quality and production efficiency, thus restricting the incremental Sheet Forming application in industrial practice. To overcome the problem of Sheet thinning, a variety of processes, such as multi-step incremental Sheet Forming, have been proposed to improve the material flow and thickness distribution. In this work, a new process has been developed by introducing multi-point Forming as preForming step before conducting incremental Sheet Forming processing. Employing an established hybrid Sheet Forming system and the corresponding thickness prediction model, the preform shape can be optimized by employing a two-step optimization approach to improve the Sheet thickness distribution. In total, two case study examples, including a hemisphere part and an aerospace cowling part, are fabricated using the developed hybrid flexible process in this study. The experimental results show that the hybrid flexible Forming process with the optimal preform design could achieve Sheet parts with more uniform thickness distribution and reduced Forming time.
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A study of incremental Sheet Forming by using water jet
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: M. W. Mohamed Bazeer, J. Chen, J. F. Cao, Hui LongAbstract:In this work, a variant of the incremental Sheet Forming (ISF) process, namely the incremental Sheet Forming by using water jet (ISF-WJ), was studied. In the investigation, an ISF-WJ prototype machine was designed and developed. Different design concepts of the water jet nozzle were proposed and evaluated to achieve the maximum Forming pressure by perForming computational fluid dynamic (CFD) simulations. Based on the Forming pressure distribution modeled by CFD simulations, finite element (FE) models were developed to study the Sheet deformation behavior under the ISF-WJ process condition. Based on the understanding gained from the numerical study, experiments were conducted to validate the ISF-WJ process and the developed prototype machine. The results suggest that ISF-WJ is a feasible process to achieve improved surface finish of thin Sheet parts. In addition, this study has found that water jet pressure plays an important role in preventing Sheet wrinkling and obtaining an accurate geometry of formed parts.
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development of novel tools for electricity assisted incremental Sheet Forming of titanium alloy
The International Journal of Advanced Manufacturing Technology, 2016Co-Authors: J. Chen, Hengan Ou, Bin Lu, Dongkai Xu, Fei Chen, Hui LongAbstract:As a new flexible Forming method, the electricity-assisted incremental Sheet Forming (E-ISF) provides concentrated local heating to improve the formability and can further expand the application of the incremental Sheet Forming (ISF) process on conventional “hard-to-form” materials such as titanium alloy. However, E-ISF process is questioned by rough surface integrity of the formed part and severe tool wear. Driven by these challenges, several novel tools have been designed by employing inner water cooling system and rolling tool end design, and the performances were validated by Forming Ti6Al4V Sheet. Experimental results suggest that the tool with rolling ball end and inner water cooling reduces the surface wear on the tool tip and improves the surface finish of the formed part.
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Investigation of the deformation stability in the incremental Sheet Forming process
MATEC Web of Conferences, 2015Co-Authors: Hui Long, J. ChenAbstract:Incremental Sheet Forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex Sheet metal parts. One of the unique characters of the ISF process is the improved formability comparing to conventional Sheet Forming process. This may be due to the localized deformation nature, which increases the deformation stability in the ISF process. Although many hypotheses have been proposed, there is no direct modelling and calculation of the ISF deformation stability. Aiming to obtain a better understanding of the ISF process, an analytical model was developed to investigate and analyse the material deformation stability in this work. Based on the analytical evaluation of stress variations and force equilibrium, a mathematical relationship between the maximum Forming angle and the process stability condition was established. To validate the developed model, experiments were carried out by Forming a hyperbolic part made of AA1100 material. The maximum Forming angle, as an indicator to the ISF formability, was employed compare the analytical evaluation and experimental result. It was found that the ISF deformation stability is one of the key factors that affect the ISF formability.
Julian M. Allwood - One of the best experts on this subject based on the ideXlab platform.
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Constrained design of Sheet Forming processes
MATEC Web of Conferences, 2016Co-Authors: Evripides G. Loukaides, Julian M. AllwoodAbstract:New Forming machines are typically incremental improvements on existing designs. Frequently tedious simulation and testing are required for insights on those possible improvements. A method for inventing features of flexible Sheet Forming processes is explored here. The inverse problem is solved by starting with a desired geometry, and “un-Forming” the part while applying a selection of kinematic constraints and minimizing the plastic work on the workpiece. The resulting deformation reveals the required forces on the part and hence can inform machine design.
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The mechanics of incremental Sheet Forming
Journal of Materials Processing Technology, 2009Co-Authors: Kathryn Jackson, Julian M. AllwoodAbstract:The deformation mechanism of incremental Sheet Forming (ISF) is examined experimentally through Forming specially prepared copper Sheets. Strain distributions through the thickness of the Sheets are measured for two configurations of ISF: two-point incremental Forming (TPIF) and single-point incremental Forming (SPIF), and a comparison is made to pressing. The measurements show that the deformation mechanisms of both SPIF and TPIF are stretching and shear in the plane perpendicular to the tool direction, with shear in the plane parallel to the tool direction. Strain components increase on successive laps, and the most significant component of strain is shear parallel to the tool direction. Increasing stretching and shear perpendicular to the tool direction account for differences between the sine law prediction and measured wall thickness for both SPIF and TPIF. The observed mechanisms of SPIF and TPIF differ from a mechanism of pure shear that has previously been assumed.
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The Increased Forming Limits of Incremental Sheet Forming Processes
Key Engineering Materials, 2007Co-Authors: Julian M. Allwood, D.r. Shouler, A. Erman TekkayaAbstract:Incremental Sheet Forming is known to give higher Forming limits than conventional Sheet Forming processes, but investigation of this effect has been impeded by the computational cost of process models which include detailed predictions of through thickness behaviour. Here, a simplified process is used to gain insight into the mechanics of a broad class of incremental Forming processes. The simplified process is described and shown to give increases in Forming limits compared to a conventional process with the same geometry. A model of the process is set up with a commercial finite element package, validated, and used to trace the history of a ‘pin’ inserted perpendicularly into the workpiece. The history of the deformation of the ‘pin’ demonstrates significant through thickness shear occurring in the direction parallel to tool motion. This insight is used to modify an existing analysis used to predict Forming limit curves. The analysis shows that for a Sheet with uniform proportional loading, the Forming limit is increased when through thickness shear is present, and this is proposed as an explanation for the increased Forming limits of incremental Sheet Forming processes.
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The Design of an Incremental Sheet Forming Machine
Advanced Materials Research, 2005Co-Authors: Julian M. Allwood, N.e. Houghton, Kathryn JacksonAbstract:A new incremental Sheet Forming machine has been built in Cambridge and was commissioned in October 2004. The basis for the machine design is described, including estimates of tool forces, the need for access to the reverse side of the workpiece, and the need to cope with high horizontal loads at the tool tip. The tool-mounting has been designed to rotate freely but passively, and to allow for simple exchange of tool tips. The workpiece is mounted on a set of load cells providing a six degree of freedom constraint without moment loading of the cells. The initial operation of the machine is briefly described.
Ying Zhang - One of the best experts on this subject based on the ideXlab platform.
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An efficient force prediction strategy for single point incremental Sheet Forming
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: Jyhwen Wang, Mahesh Nair, Ying ZhangAbstract:Incremental Sheet Forming is a flexible Forming process where a tool is programmed to follow predetermined tool paths to create Sheet metal parts. It is ideal for rapid prototyping and low-volume production. Modeling incremental Sheet Forming and predicting Forming forces can significantly benefit product design and process development. Existing force prediction methods are either inaccurate or too time consuming. The goal of this research is to identify an efficient force prediction strategy based on experimental observations of Forming forces. It was found that by creating a near-finished part geometry as a starting point of numerical simulation, Forming forces can be predicted with satisfactory accuracy and efficiency. The proposed strategy was validated and further demonstrated in Forming of parts having different geometries. As the simulation strategy can be completed in a fraction of the full simulation time, it can be adopted to guide the development of incremental Sheet Forming parts.
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An Efficient Force Prediction Strategy in Single Point Incremental Sheet Forming
Procedia Manufacturing, 2016Co-Authors: Jyhwen Wang, Mahesh Nair, Ying ZhangAbstract:Incremental Sheet Forming is a flexible Forming process where a tool is programmed to follow predetermined tool paths to create Sheet metal parts. It is ideal for rapid prototyping and low-volume production. Modeling incremental Sheet Forming and predicting Forming forces can significantly benefit product design and process development. Existing force prediction methods are either inaccurate or too time consuming. The goal of this research is to identify an efficient force prediction strategy based on experimental observations of Forming forces. It was found that by creating a near-finished part geometry as a starting point of numerical simulation, Forming forces can be predicted with satisfactory accuracy and efficiency. The proposed strategy was validated and further demonstrated in Forming of parts having different geometries. As the simulation strategy can be completed in a fraction of the full simulation time, it can be adopted to guide the development of incremental Sheet Forming parts.
P.a.f. Martins - One of the best experts on this subject based on the ideXlab platform.
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3.02 – Incremental Sheet Forming
Comprehensive Materials Processing, 2014Co-Authors: M.b. Silva, P.a.f. MartinsAbstract:Recent advances in incremental Forming of Sheets have led to the development of new manufacturing processes with high flexibility and potential economic payoff for rapid prototyping and small-quantity production. Incremental Forming of Sheets not only provides significant savings in material and energy requirements, but also enables the production of different parts with the same tooling system. This chapter begins with a state-of-the-art review of incremental Sheet Forming, continues with an overview of the most commonly used materials, and ends with a comprehensive presentation of the analytical, numerical, and experimental modeling of benchmark and industrial parts made with metals and polymers.
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On the relative performance of hole-flanging by incremental Sheet Forming and conventional press-working
Proceedings of the Institution of Mechanical Engineers Part L: Journal of Materials: Design and Applications, 2013Co-Authors: Luciana Montanari, M.b. Silva, V.a.m. Cristino, P.a.f. MartinsAbstract:The purpose of this article is to provide readers with a broad understanding on the deformation mechanics of hole-flanging by incremental Sheet Forming that will enable them to identify the major operating parameters, to determine the process formability window and to successfully design hole-flanged Sheet metal parts. The methodology draws upon the utilization of circle grid analysis, measurement of the gauge length strains at the onset of fracture in a wide range of Sheet formability tests, determination of the failure limits by necking and fracture and evaluation of the relative performance of hole-flanging by incremental Sheet Forming and conventional press-working. The presentation is illustrated with selected test cases obtained from a comprehensive experimental investigation. The overall content of this article widens and enhances previous research work by the authors in the understanding of the deformation mechanics and failure in hole-flanging by incremental Sheet Forming and includes new experim...
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On the formability of hole-flanging by incremental Sheet Forming
Proceedings of the Institution of Mechanical Engineers Part L: Journal of Materials: Design and Applications, 2013Co-Authors: M.b. Silva, Pedro Teixeira, Ana Reis, P.a.f. MartinsAbstract:Hole-flanging by incremental Sheet Forming is developing as an innovative metal Forming technology for flexible small batch-production of cylindrical or conical flanges in blanks with pre-cut holes. The process is seen as an alternative to hole-flanging by conventional press-working due to significant cost savings through the replacement of complex press-tools by simple dieless Forming apparatuses and to widespread belief that the limiting Forming ratio of hole-flanging by incremental Sheet Forming is always higher than that of hole-flanging by conventional press-working. This article focuses on the aforementioned assumption and investigates the influence of material failure by necking and fracture on the limiting Forming ratio. The experimental work is performed in a CNC machining center and a hydraulic press equipped with apparatuses for multi-stage single point incremental Forming and conventional press-tooling, and the strain loading paths resulting from each Forming process are determined by circle g...
Fei Han - One of the best experts on this subject based on the ideXlab platform.
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Method of closed loop springback compensation for incremental Sheet Forming process
Journal of Central South University, 2011Co-Authors: Fei Han, Pan GongAbstract:The closed loop control model was built up for compensating the springback and enhancing the work piece precision. A coupled closed loop algorithm and a finite element method were developed to simulate and correct the springback of incremental Sheet Forming. A three-dimensional finite element model was established for simulation of springback in incremental Sheet Forming process. The closed loop algorithm of trajectory profile for the incremental Sheet Forming based on the wavelet transform combined with fast Fourier transform was constructed. The profile of processing tool path of shallow dishing with spherical surface was designed on the basis of the profile correction algorithm. The result shows that the algorithm can predict an ideal profile of processing track, and the springback error of incremental Sheet Forming is eliminated effectively. It has good convergence efficiency, and can improve the workpiece dimensional accuracy greatly.
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Studies on the Springback Mechanism of Incremental Sheet Forming Based on FEM Simulation
Advanced Materials Research, 2010Co-Authors: Fei Han, Xiao Hui Cui, Zai Lin WangAbstract:Incremental Sheet Forming (ISF) is an innovative and highly flexible Sheet metal Forming process for small batch production and prototyping, but springback is a very important factor to influence the quality of incremental Sheet Forming. This paper investigates the springback mechanism of incremental Sheet Forming using numerical method. A three-dimensional elasto-plastic finite element model was established for the simulation of the incremental Sheet Forming process. In this model, the combination of dynamic explicit algorithm and the static implicit algorithm was proposed to calculate the whole Forming process including springback. The results of numerical simulation, such as, the strain history and distribution, the stress state and distribution, etc., are discussed in details. Moreover, the results confirm that residual stress has been releasing during Forming process, which reveal the peculiar springback characteristic of incremental Sheet Forming process.
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Numerical Simulation and Experimental Investigation of Incremental Sheet Forming Process
Journal of Central South University of Technology, 2008Co-Authors: Fei HanAbstract:In order to investigate the process of incremental Sheet Forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those of experiment. The results of numerical simulations, such as the strain history and distribution, the stress state and distribution, Sheet thickness distribution, etc, were discussed in details, and the influences of process parameters on these results were also analyzed. The simulated results of the radial strain and the thickness distribution are in good agreement with experimental results. The simulations reveal that the deformation is localized around the tool and constantly remains close to a plane strain state. With decreasing depth step, increasing tool diameter and wall inclination angle, the axial stress reduces, leading to less thinning and more homogeneous plastic strain and thickness distribution. During ISF, the plastic strain increases stepwise under the action of the tool. Each increase in plastic strain is accompanied by hydrostatic pressure, which explains why obtainable deformation using ISF exceeds the Forming limits of conventional Sheet Forming.
