Publications
136 results found
Li N, Politis D, Foster AD, et al., 2016, Prediction of thinning behavior for complex-shaped, lightweight alloy panelsformed through a hot stamping process*, 2nd International Conference on Advanced High Strength Steel and Press Hardening (ICHSU2015):, Publisher: World Scientific
This paper provides an overview of hot stamping of light alloys using a method known as HFQ®forming. We present a new method of forming complex shaped automotive components through theuse of a hot stamping process for high strength AA6082 alloy. In particular, the component selectedfor study is a complex automotive door inner component that could not be conventionally formedfrom such a strong alloy. The forming process is described and the post-formed thicknessdistribution is presented. An FE simulation is given to demonstrate the potential to predict theforming process and to provide guidance as to the final component thicknesses.
Yuan X, Zhou D, politis DENIS, et al., 2015, Tool-life prediction under multi-cycle loading during metal forming: a feasibility study, Manufacturing Review, Vol: 2, ISSN: 2265-4224
In the present research, the friction and wear behaviour of a hard coating were studied by using ball-on-disc tests to simulate the wear process of the coated tools for sheet metal forming process. The evolution of the friction coefficient followed a typical dual-plateau pattern, i.e. at the initial stage of sliding, the friction coefficient was relatively low, followed by a sharp increase due to the breakdown of the coatings after a certain number of cyclic dynamic loadings. This phenomenon was caused by the interactive response between the friction and wear from a coating tribo-system, which is often neglected by metal forming researchers, and constant friction coefficient values are normally used in the finite element (FE) simulations to represent the complex tribological nature at the contact interfaces. Meanwhile, most of the current FE simulations consider single-cycle loading processes, whereas many metal-forming operations are conducted in a form of multi-cycle loading. Therefore, a novel friction/wear interactive friction model was developed to, simultaneously, characterise the evolutions of friction coefficient and the remaining thickness of the coating layer, to enable the wear life of coated tooling to be predicted. The friction model was then implemented into the FE simulation of a sheet metal forming process for feasibility study.
Yang H, Liu L, Chen H, et al., 2015, Investigation on creep age forming of AA2219 Stiffened Structures, The 4th International Conference on New Forming Technology (ICNFT2015), Publisher: EDP Sciences, ISSN: 2261-236X
The research described in this paper is a study of CAF a 2219 aluminium alloy,which is used for fabricating the isogrid structure for fuel tanks of launch vehicles. Themain aim of the research is to develop a small scale CAF test rig, which was designed toanalyse the springback behaviour from CAF. The main objective of the experiment wasto investigate the potential proposals of creep age forming stiffened structures. Based onthe results of the experiment, a potential CAF process for forming 1/3 pieces of an isogridcylindrical assembly was proposed.
Mohamed M, Li N, Wang L, et al., 2015, An investigation of a new 2D CDM model in predicting failure in HFQing of an automotive panel, The 4th International Conference on New Forming Technology (ICNFT2015)
gao HAOXIANG, weng TIANXIN, li C, et al., 2015, Hot stamping of an Al-Li alloy: a feasibility study, The 4th International Conference on New Forming Technology (ICNFT2015), Publisher: EDP Sciences, ISSN: 2261-236X
liu JUN, Gao HAOXIANG, ElFakir OMER, et al., 2015, HFQ forming of AA6082 tailor welded blanks, The 4th International Conference on New Forming Technology (ICNFT2015)
liu X, Ji KANG, ElFakir OMAR, et al., 2015, Determination of the Interfacial Heat Transfer Coefficient in the Hot Stamping of AA7075, The 4th International Conference on New Forming Technology (ICNFT2015)
Ji K, Fakir OE, Gao H, et al., 2015, Determination of Heat Transfer Coefficient for Hot Stamping Process, Materials Today: Proceedings, Vol: 2, Pages: S434-S439, ISSN: 2214-7853
Gao H, Li N, Ho H, et al., 2015, Determination of a Set of Constitutive Equations for an Al-Li Alloy at SPF Conditions, Materials Today: Proceedings, Vol: 2, Pages: S408-S413, ISSN: 2214-7853
Liu J, Wang LL, Lee J, et al., 2015, Size-dependent mechanical properties in AA6082 tailor welded specimens, Journal of Materials Processing Technology, Vol: 224, Pages: 169-180, ISSN: 0924-0136
AA6082 tailor welded blanks (TWBs) produced using laser welding and friction stir welding were studiedin this paper. The nominal mechanical properties of welded AA6082 under uniaxial tension conditionswere characterised by evaluating the local properties of the base material, heat affected zone (HAZ) andweld zone. Tensile specimens were machined in the way that the weld line lies perpendicular to theloading axis. Three standard-sized specimens containing varying ratios of weld in the gauge region ofthe specimen were used to determine the size-dependent properties of welded AA6082 in the TWBs.A post-weld strength prediction (PWSP) model, based on the theories of plasticity, has been developedto estimate the post-weld properties of the tailor welded specimens. The model can be used to predictthe post-weld yield strength and the global tensile behaviour of welded AA6082 specimens. Good agreementsbetween the modelling and the experimental results have been obtained, with the yield strengthdeviation less than 6%. It was found that the yield strength increased with increasing dimensions of thetensile specimens. The size-dependent phenomenon was studied and the complex plastic deformationmechanisms have been found to cause the size-dependent phenomenon
Ma G, Wang L, Gao H, et al., 2015, The friction coefficient evolution of a TiN coated contact during sliding wear, Applied Surface Science, Vol: 345, Pages: 109-115, ISSN: 0169-4332
Yuan X, Zhou D, Politis DJ, et al., 2015, Tool life prediction under multi-cycle loading conditions: A feasibility study, 4th International Conference on New Forming Technology (ICNFT), Publisher: E D P SCIENCES, ISSN: 2261-236X
El Fakir O, Wang L, Balint D, et al., 2014, Numerical study of the solution heat treatment, forming, and in-die quenching (HFQ) process on AA5754, International Journal of Machine Tools and Manufacture, Vol: 87, Pages: 39-48, ISSN: 0890-6955
An FE model of the solution heat treatment, forming and in-die quenching (HFQ) process was developed. Good correlation with a deviation of less than 5% was achieved between the thickness distribution of the simulated and experimentally formed parts, verifying the model. Subsequently, the model was able to provide a more detailed understanding of the HFQ process, and was used to study the effects of forming temperature and speed on the thickness distribution of the HFQ formed part. It was found that a higher forming speed is beneficial for HFQ forming, as it led to less thinning and improved thickness homogeneity.
Raugei M, El Fakir O, Wang L, et al., 2014, Life cycle assessment of the potential environmental benefits of a novel hot forming process in automotive manufacturing, JOURNAL OF CLEANER PRODUCTION, Vol: 83, Pages: 80-86, ISSN: 0959-6526
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- Citations: 42
Das S, Barekar NS, El Fakir O, et al., 2014, Effect of melt conditioning on heat treatment and mechanical properties of AZ31 alloy strips produced by twin roll casting, Materials Science and Engineering: A, Vol: 620, Pages: 223-232, ISSN: 0921-5093
Sun C, Liu G, Zhang Q, et al., 2014, Determination of hot deformation behavior and processing maps of IN 028 alloy using isothermal hot compression test, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 595, Pages: 92-98, ISSN: 0921-5093
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- Citations: 46
El Fakir O, Das S, Stone I, et al., 2014, Solution heat treatment, forming and in-die quenching of a commercial sheet magnesium alloy into a complex-shaped component: Experimentation and FE simulation, Key Engineering Materials, Vol: 622-623, Pages: 596-602, ISSN: 1013-9826
Interest in lightweight materials, particularly magnesium alloys, has increased significantly with rising efficiency requirements in the automotive sector. Magnesium is the lightest available structural metal, with a density approximately 35% lower than that of aluminium. The potential is great for magnesium to become a primary material used in future low carbon vehicle structures; however, there are significant obstacles, namely low ductility and formability, particularly at room temperature. The aim of this work is to present the feasibility of using the solution Heat treatment, Forming, and in-die Quenching (HFQ) process to produce complex shapes from a sheet magnesium alloy, and to use the results to verify a simulation of the process developed using commercial FE software. Uniaxial tensile tests were initially conducted to establish the optimum parameters for forming the part. Stamping trials were then carried out using these parameters, and a simulation set up modelling the forming operation. It was shown that the HFQ process could be used to form a successful component from this alloy, and that a good match was achieved between the results of the forming experiments and the simulation.
El Fakir O, Wang L, Balint D, et al., 2014, Predicting effect of temperature, strain rate and strain path changes on forming limit of lightweight sheet metal alloys, 11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014, Vol: 81, Pages: 736-741, ISSN: 1877-7058
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- Citations: 18
Cai J, Wang Y, Wu D, et al., 2013, Potential applications of hybrid forming of aluminum alloys in aircraft, Proceedings of the International Astronautical Congress, IAC, Vol: 8, Pages: 6569-6575, ISSN: 0074-1795
A new forming process, the hybrid forming of aluminum alloys is introduced in this paper. The application of this forming process in the high-class vehicles is reviewed. In this process, the aluminum alloy sheet is formed and quenched simultaneously followed by a second stage precipitation period. The forming process has greatly improved the formability and strength of aluminum alloys. A much lighter and stronger component, with more complex geometry can be obtained. Advanced research on this process is presented in the paper. The potential applications of hybrid formed aluminum alloys components in aircrafts is discussed. Both advantage and disadvantage of this application is reviewed. Copyright © 2013 by the International Astronautical Federation.
Wang L, Lin J, El Fakir O, et al., 2013, HFQ forming: a novel lightweight sheet metal forming technology for mass-production, TTP2013 Tools and Technologies for Processing Ultra High Strength Materials
The legislative targets to develop more fuel-efficient vehicles, and thus to reduce energy consumption and air pollution, are a challenge for the automotive industry. Lightweighting is one of the most effective approaches to achieve these targets. A highly innovative forming technology to form lightweight aluminium panels (solution Heat treatment, Forming and in-die Quenching: HFQ) has been developed and patented by Imperial College London and is being commercialized by Impression Technologies Ltd. Four major benefits are realized by the HFQ technology: high formability, superior post-form strength, short processing time and low springback. Comprehensive studies and analysis on the formability, post-form strength and springback of the HFQ forming process are presented.
Das S, Ji S, El Fakir O, et al., 2013, Melt conditioned twin roll casting (MC-TRC) of thin Mg-alloy strips for direct stamping of Mg components, 6th International Light Metals Technology Conference, LMT 2013
In this paper we introduce a novel process for the production of thin-walled magnesium components by direct stamping of twin roll cast thin Mg strips. In this p rocess, the melt conditioned twin roll casting (MC-TRC) process is used to produce thin Mg strips (thickness <2 mm) which have a fine equiaxed grain structure and little basal texture and, more importantly, are free from centreline segregation. Such thin Mg strips can be used for thin-walled component production by direct stamping without any rolling. A major advantage of this process is that it circumvents the low formability problem inherently associated with Mg based alloys. In this paper, AZ31 alloy is used to demonstrate this new process. For both TRC and MC-TRC strips, we will analyze the microstructures, assess the mechanical performance at elevated temperatures and conduct hot stamping in the as-cast condition without any prior rolling.
El Fakir O, Chen S, Wang L, et al., 2013, Numerical Investigation on the Hot forming and Cold-Die Quenching of an Aluminium-Magnesium Alloy into a Complex Component, LIGHT METALS TECHNOLOGY 2013, Vol: 765, Pages: 368-372, ISSN: 0255-5476
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- Citations: 6
Chen S, El Fakir O, Wang L, et al., 2013, Experimental study of a novel electrical upsetting process, International Conference on Materials Processing Technology
In this paper, a novel electrical upsetting process was developed. The novel upsetting tests were conducted in a Gleeble 3800 thermomechanical simulator. The forming results showed that three key forming parameters played important roles in the electrical upsetting process. These parameters are heating rate, forming temperature and forming rate. A processing window was summarized to describe the domain of optimum forming parameters of electrical upsetting process.
Cai J, Wang Y, Wu D, et al., 2013, Potential applications of hybrid forming of aluminum alloys in aircraft, the International Astronautical Congress
Wang L, Yang H, 2012, Friction in aluminium extrusion-part 2: A review of friction models for aluminium extrusion, TRIBOLOGY INTERNATIONAL, Vol: 56, Pages: 99-106, ISSN: 0301-679X
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- Citations: 20
Wang L, Zhou J, Duszczyk J, et al., 2012, Friction in aluminium extrusion-Part 1: A review of friction testing techniques for aluminium extrusion, TRIBOLOGY INTERNATIONAL, Vol: 56, Pages: 89-98, ISSN: 0301-679X
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- Citations: 35
Li F, He ZB, Wang L, et al., 2012, Process analysis in mandrel extrusion of special-shaped aluminum alloys profile, Kovove Materialy, Vol: 50, Pages: 269-275, ISSN: 0023-432X
In order to reveal abnormal shaped aluminum alloy law of needle piercing extrusion formation, setting the missile empennage as an example, this paper adopts the non-linear finite element to conduct the three-dimensional thermal simulation of abnormal shaped material law of needle piercing extrusion formation process and analyses systematically the influence of process law on temperature change, additional tensile stress and forming load. The results show that, in the range of low-speed extrusion, the billet's highest peak temperature shows a decreasing trend, and with the extrusion speed increasing, the decrease of highest peak temperature decreases, while the axial extra tensile stress on the mouth of model increases accordingly; the axis part of the mold's mouth is a high-temperature zone in the forming process, and with the axis center distance increasing, the temperature decreases gradually; and with the pressing reduction's increase, the gradient of temperature decreasing trend slows down gradually. This provides a theoretical basis to technical design of abnormal shaped material needle piercing extrusion formation and the metal distortion flow control.
Wang L, Zhou J, Duszczyk J, et al., 2012, Identification of a friction model for the bearing channel of hot aluminium extrusion dies by using ball-on-disc tests, TRIBOLOGY INTERNATIONAL, Vol: 50, Pages: 66-75, ISSN: 0301-679X
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- Citations: 15
Li F, Li JH, Li C, et al., 2012, Research on the Deformation Mechanism and Failure Behavior of Punch Bonding Technology with Dissimilar Sheet Metals, JOM, Vol: 64, Pages: 600-606, ISSN: 1047-4838
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- Citations: 2
Li F, He ZB, Wang L, et al., 2012, Process analysis in mandrel extrusion of special-shaped aluminum alloys profile, KOVOVE MATERIALY-METALLIC MATERIALS, Vol: 50, Pages: 269-275, ISSN: 0023-432X
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