Publications
143 results found
Liu X, Elfakir O, Meng L, et al., 2017, Effects of lubricant on the IHTC during the hot stamping of AA6082 aluminium alloy: experimental and modelling studies, Journal of Materials Processing Technology, Vol: 255, Pages: 175-183, ISSN: 0924-0136
In this paper, the IHTC evolutions between a hot AA6082 specimen and cold P20 tools were quantitatively studied as a function of contact pressure, specimen thickness and lubricant, using the inverse FE simulation method. A novel interactive model was developed to predict IHTC evolutions with diminutions of different lubricants as a function of sliding distance (or time) at different contact pressures and sliding speeds. It was deduced that the interaction between the lubricant and the IHTC consists of three stages; namely stage I (excessive stage), in which the lubricant is applied excessively and the IHTC is plateaued, stage II (consumption stage), in which the lubricant diminishes during sliding and the IHTC decreases rapidly, and stage III (breakdown stage), in which lubricant breakdown occurs and the IHTC is equal to its values under dry conditions.
Shi Z, Wang L, Mohamed M, et al., 2017, A new design of friction test rig and determination of friction coefficient when warm forming an aluminium alloy, International Conference on the Technology of Plasticity, ICTP 2017, Publisher: Elsevier, Pages: 2274-2279, ISSN: 1877-7058
To facilitate reduced fuel consumption and increase environmental friendliness, in recent years, demands for lightweight vehicles have been increasing, and interest in hot or warm forming of sheet aluminium alloys for use in vehicle body structures, has grown. For better understanding and optimisation of the forming processes, knowledge of friction coefficient between tooling and work-piece, at elevated temperature, is critical. However, because of difficulties with measurement at elevated temperature, most studies on friction are limited to room temperature. In this study, a friction rig was designed for isothermal tests at elevated temperature. The test rig enables pure sliding between pins (made of a tool steel) and a metal sheet. The friction behaviour of Forge Ease 278, a water based solid lubricant pre-applied to aluminium alloy AA5754, was investigated, under isothermal warm forming conditions, using the test rig. The effects of testing temperature, sliding speed and applied pressure on the friction coefficient were studied. It was found that Forge Ease produced a low friction coefficient of around 0.05, above room temperature and below 250 °C. The lubricant performance degrades at 350 °C and the friction coefficient increases markedly. Both sliding speed (up to 150 mm s -1 ) and applied pressure (up to 12.8 MPa) had no significant effect on friction coefficient of Forge Ease.
Zhou W, Lin J, Dean TA, et al., 2017, A novel application of sideways extrusion to produce curved aluminium profiles: Feasibility study, International Conference on the Technology of Plasticity, ICTP 2017, Pages: 2304-2309
© 2017 The Authors. Published by Elsevier Ltd. Conventional curved aluminium alloy profile forming methods which depend on apparatus, additional to extrusion tooling, to bend extruded, straight sections inevitably decrease manufacturing efficiency and have to deal with springback and cross-sectional distortion. In this article, a novel energy-efficient forming method based on internal differential material flow, differential velocity sideways extrusion (DVSE), is proposed, which can directly form billets into curved profiles/sections by extrusion alone, using two opposing punches. A detailed study has been conducted and cold extrusion/bending of round bars and tubes was examined. It was found that curved profiles/sections with no distortion are formed, and adjustable profile curvature can be achieved by changing the velocity ratio of a slower lower punch to a faster upper punch and also extrusion ratio. Lower velocity ratio and larger extrusion ratio tend to increase the material flow velocity gradient at the die exit and lead to greater curvature. Effect of velocity ratio is greater than that of extrusion ratio, especially when velocity ratio is less than 1/3. Effect of the extrusion ratio is small when velocity ratio is greater than 0.5, after which the effect of extrusion ratio becomes more significant as velocity ratio decreases.
Liu J, Wang A, Zheng Y, et al., 2017, Hot stamping of AA6082 tailor welded blanks for automotive applications, Procedia Engineering, Vol: 207, Pages: 729-734, ISSN: 1877-7058
Friction stir welded (FSWed) AA6082 tailor welded blanks (TWBs), with gauge combinations of 2.0-2.5 and 3.0-5.0 mm, have been prepared and successfully formed into automotive panel components. Experimental results indicated that the post-form strength, in terms of hardness, varied from location to location on the final parts. The strength is highly dependent on the blank gauges, with the average hardness values being HV 110 and HV 98 for the 2.0-2.5 and 3.0-5.0 mm TWB parts, respectively. Conventional FE simulation was built in PAM-STAMP and the prediction results were validated from experimental data in terms of strain distribution and temperature evolution. A typical continuous cooling precipitation (CCP) diagram for AA6082 was implemented into the verified simulation data to explain the strength variations. It is deemed that the temperature history during the stamping and quenching stages has played a major role on the post-form strength of the final parts.
Liu X, Gharbi MM, Manassib O, et al., 2017, Determination of the interfacial heat transfer coefficient between AA7075 and different forming tools in hot stamping processes, Procedia Engineering, Vol: 207, Pages: 717-722, ISSN: 1877-7058
The interfacial heat transfer coefficient (IHTC) is an important thermo-physical parameter in hot stamping processes, for achieving the desired post-form mechanical strength of formed components. In the present study, the temperature evolutions of specimens under hot stamping conditions were measured using a novel IHTC test facility. The effects of contact pressure and tool material on the IHTC were subsequently investigated between the hot AA7075 specimens and different forming tools. In order to predict the IHTC evolutions, a mechanism based IHTC model was developed to represent the effects of contact pressure and tool material on the IHTC.
liu J, Wang L, 2017, Effect of porosities on tensile properties of laser-welded Al-Li alloy: an experimental and modelling study, International Journal of Advanced Manufacturing Technology, Vol: 95, Pages: 659-671, ISSN: 0268-3768
Aluminium–lithium (Al-Li) alloys are very attractive for aerospace applications due to their outstanding properties, such as high specific strength, high rigidity and good resistance to corrosion and fatigue, compared to conventional aluminium alloys. The butt joints of Al-Li 2A97-T3 alloy sheet produced by fibre laser welding with ER2319 filler wire were investigated in this paper. Uniaxial tensile tests have been performed to determine the nominal mechanical properties of the joints with and without porosities. In addition, a defect zone was defined in the welded specimens to investigate the effects of porosity on the joint tensile behaviour. The post-weld strength prediction (PWSP) model in a previous study has been extended by including the effects of the porosity in the welds to predict the overall response of the butt joints. The experimental and the modelling results show a good agreement, with the yield strength having a deviation lower than 5%. Both the yield strength and the ductility of the tensile specimens were observed to have decreased with the presence of porosities. The porosities aggravated the inhomogeneous deformation in the weld zone. Higher strain rate was found in the defect area than the remaining weld zone during plastic deformation, as the porosity in the specimen caused inhomogeneous deformation. It was found that this accelerated the failure of the specimen and lowered the global ductility significantly.
Wang K, Liu G, politis, et al., 2017, Correlation between softening mechanisms and deformation non-uniformity of laser-welded titanium alloy tube during gas bulging process, Materials Characterization, Vol: 133, Pages: 196-205, ISSN: 1044-5803
In this paper, post-weld annealing was carried out to adjust the flow stress difference between weld seam and base material (BM). Deformation non-uniformity of laser-welded titanium alloy tubes before and after annealing was evaluated by gas bulging at 800 °C. Results show that after double annealing (950 °C/2 h, air cooling + 600 °C / 2 h, air cooling), weld seam and BM had similar peak stress at first during tensile test at 800 °C, 0.001 s− 1, then the flow stress difference between them changed dynamically due to different softening rates. The maximum flow stress difference ratio was reduced from 36% to 17% after annealing. Deformation uniformity of the bulged tube was improved by 24.6% after annealing, but the higher softening rate of BM during gas bulging confined its further improvement. At early stage of gas bulging of the annealed tube, the main softening mechanism for weld seam was dynamic recovery and that for BM was globularization of secondary α and phase transformation of α to β. At middle-late stage of gas bulging, the main softening mechanism for weld seam was partial globularization of lamella α and that for BM was wide dynamic recrystallization.
Wang K, Liu G, Huang K, et al., 2017, Effect of Recrystallization on Hot Deformation Mechanism of TA15 Titanium Alloy under Uniaxial Tension and Biaxial Gas Bulging Conditions, Materials Science and Engineering: A, Vol: 708, Pages: 149-158, ISSN: 0921-5093
To investigate the effect of recrystallization on hot deformation mechanism of TA15 titaniumalloy, rolled sheet and laser-welded tubes before and after recrystallization annealing were tested byuniaxial tensile tests and biaxial gas bulging respectively. The results show that both of the initial rolledsheet and the as-welded tube consisted of equiaxed α microstructure with high initial dislocationdensity. During uniaxial tensile tests, a quasi-steady flow state was achieved at 800o C, 0.001 s-1, whichdemonstrated the best formability with a maximum elongation of 536%. Significant recrystallizationoccurred at the early stage of tensile deformation and the grain size was found to decrease first and thenincrease. Significant recrystallization also occurred at the early stage of the biaxial gas bulging of theas-welded tube. During the bulging of the annealed tube consisting of equiaxed α with low initialdislocation density, dynamic recrystallization (DRX) was the main microstructure evolutioncharacteristic, but most of the DRX occurred at the middle-late stage. The relatively coarse equiaxed αand increasing fraction of low angle grain boundaries during deformation may restrict the occurrenceof grain boundary sliding (GBS), which resulted in the relatively worse formability of the annealedtube. However, recrystallization which happened widely at the early stage, increased the fraction ofhigh angle grain boundaries, refined the microstructure, promoted the occurrence of GBS and enhancedthe formability of the initial rolled sheet and as-welded tube. It was also found that the stress state hadno effect on the DRX mechanism for TA15 at 800o C, which was confirmed to be discontinuousdynamic recrystallization under both uniaxial tension and biaxial gas bulging conditions.
Wang L, 2017, Forming limit prediction for AA7075 alloys under hot stamping conditions, IDDRG 2017
Gao H, elFakir O, Wang L, et al., 2017, Forming limit prediction for hot stamping processes featuring non-isothermal and complex loading conditions, International Journal of Mechanical Sciences, Vol: 131-132, Pages: 792-810, ISSN: 0020-7403
An intrinsic feature of the hot stamping process, in which a hot blank is quenched and formed between water cooled dies, is the severe thermo-mechanical deformation that the blank experiences under the combined influences of non-isothermal and non-proportional loadings. This results in challenges for conventional forming limit prediction models to accurately predict material behavior. In this paper, a novel viscoplastic-Hosford-MK model was developed to predict the forming limits of an Al-Li alloy under hot stamping conditions. The effectiveness of the developed model was verified by the demonstration of accurate responses to cold die quenching, strain rate and loading path changes, enabling the developed model to reveal a realistic critical material response under complex deformation conditions. Finally, by applying the developed model to the hot stamping of an AA2060 component, its accuracy was successfully validated. It was indicated that the onset of necking during hot stamping of the component did not necessarily occur at the maximum thinning region, and this was due to the comprehensive effects of varying loading path, strain rate and temperature. A detailed mathematical analysis of the developed M-K model was also conducted, and it was found that the incremental work per unit volume ratio (View the MathML source) between Zone b (where a thickness inhomogeneity exists) and Zone a (the remainder of the material) was a significant parameter that determined the formability of AA2060 under hot stamping conditions.
wang A, liu JUN, gao H, et al., 2017, Hot stamping of AA6082 tailor welded blanks: experiments and knowledge based cloud FE (KBC-FE) simulation, Journal of Materials Processing Technology, Vol: 250, Pages: 228-238, ISSN: 0924-0136
A novel hot stamping technique known as ‘Solution Heat treatment, Forming and in-die Quenching (HFQ®)’ was employed to manufacture lightweight structural components from AA6082 tailor-welded blanks (TWBs) of different thickness combinations: 1.5–1.5 and 2.0–1.0 mm. A finite element (FE) model was built to study the deformation characteristics during the hot stamping process. The FE model was successfully validated by comparing simulation results with experimental ones. Subsequently, the verified simulation results were analysed through a novel multi-objective FE platform known as ‘Knowledge-Based Cloud – Finite Element (KBC-FE)’. KBC-FE operates in a cloud environment and offers various advanced unique functions via functional modules. The ‘formability’ module was implemented in the current study to predict the limiting dome height and failure mode during the hot stamping process. Good agreements were achieved between the predicted and experimental results, from which studies were extended to predict the forming features of 2.0–1.5 mm TWBs. The ‘formability’ module has successfully captured the complex nature of a hot stamping process, featuring a non-isothermal and non-linear loading path. The formability of TWBs was found to be dependent on forming speed and blank thickness, out of which the latter has a dominant effect.
Gao H, politis D, luan X, et al., 2017, Forming limit prediction for AA7075 alloys under hot stamping conditions, International Deep Drawing Research Group (IDDRG), Publisher: Institute of Physics (IoP), ISSN: 1742-6588
He M, Zhuo H, Chen W, et al., 2017, Sequence stratigraphy and depositional architecture of the Pearl River Delta system, northern South China Sea: An interactive response to sea level, tectonics and paleoceanography, MARINE AND PETROLEUM GEOLOGY, Vol: 84, Pages: 76-101, ISSN: 0264-8172
Liu X, Ji K, El Fakir O, et al., 2017, Determination of the interfacial heat transfer coefficient for a hot aluminium stamping process, Journal of Materials Processing Technology, Vol: 247, Pages: 158-170, ISSN: 1873-4774
The interfacial heat transfer coefficient (IHTC) is an important thermophysical parameter in hot stamping processes and must be identified not only to retain the full mechanical strength of formed components, but also to optimise the production rate. In this work, a novel experimental facility was developed and applied to measure the temperature evolutions of the specimens and tools in stamping processes. Simulated temperature evolutions obtained using the FE software PAM-STAMP were then fit to this data. The IHTC values between AA7075 and three different tool materials were characterized at different contact pressures under both dry and lubricated conditions. In addition, a mechanism based IHTC model was developed and validated as a function of contact pressure, tool material and lubricant thickness to predict the IHTC values under different conditions.
Wang L, Zhou D, Gao H, et al., 2016, Knowledge based cloud FE simulation of sheet metal forming processes, Journal of Visualized Experiments, Vol: 118, ISSN: 1940-087X
The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancingthe efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focuson the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need tosimulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their highstrength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to formthem. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating suchbehavior is computationally very expensive using conventional FE simulation techniques.This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction modelswith conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. Theapplication of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hotstamping conditions, and the tool life prediction under multi-cycle loading conditions.
Wang L, Politis DJ, Masen MA, 2016, Development of an interactive friction model for the prediction of lubricant breakdown behaviour during sliding wear, Tribology International, Vol: 110, Pages: 370-377, ISSN: 1879-2464
In this paper, a novel interactive friction-lubricant thickness model was developed to predict the evolution of coefficient of friction and the useful life of lubricant film. The developed model was calibrated by experimental results determined from pin-on-disc tests. For these experiments, a grease lubricant was applied on a Tungsten Carbide ball which slides against a disc made from AA6082 Aluminium alloy. In the pin-on-disc tests, the lubricant film thickness decreased with time during single path sliding leading to a rapid increase in the coefficient of friction. The breakdown of lubricant was divided into three stages, namely, the Stage I low and stable coefficient of friction region, Stage II region in which the coefficient of friction sees a rapid rise, and Stage III in which the coefficient of friction reaches a plateau with a value similar to that of dry sliding. In order to characterise the evolution of coefficient of friction throughout these stages, a novel interactive friction model was developed combining the effects of sliding distance, sliding speed, contact pressure and initial lubricant amount on the evolution of the coefficient of friction. This interactive friction model can be applied to situations involving lubricant breakdown in a dynamic environment such as the metal forming industry, where the use of traditional constant coefficient of friction values present limits in predictive accuracy.
Ji K, Liu X, El Fakir O, et al., 2016, Determination of the Interfacial Heat Transfer Coefficient in the Hot Stamping of AA7075, MANUFACTURING REVIEW, Vol: 3, ISSN: 2265-4224
Luan X, El Fakir O, Gao H, et al., 2016, Formability of AA6082-T6 at warm and hot stamping conditions, Key Engineering Materials, Vol: 716, Pages: 107-113, ISSN: 1013-9826
Forming limit diagrams (FLDs) of AA6082 at warm/hot stamping conditions weredetermined by using a specially designed test rig. The tests were carried out at various temperaturesfrom 300°Cto 450°C and forming speeds ranging from 75 mm/s to 400 mm/s. The strain wasvisualized and measured using ARGUS software provided by GOM. The results clearly show thatthe formability of AA6082-T6 sheet metal, in terms of the limit major strain, increased by 38.9%when the forming temperature was increased from 300°C to 450°C at a speed of 250 mm/s, andincreased by 42.4% when the forming speed was decreased from 400 mm/s to 75 mm/s at atemperature of 400°C. It was verified that hot stamping is a promising technology formanufacturing complex-shaped components.
Liu J, Wang A, Gao H, et al., 2016, Studies on the Hot Forming and Cold-die Quenching of AA6082 TailorWelded Blanks, Key Engineering Materials, Vol: 716, Pages: 941-947, ISSN: 1013-9826
An advanced forming process involving hot forming and cold-die quenching, also knownas HFQ®, has been employed to form AA6082 tailor welded blanks (TWBs). The HFQ® processcombines both forming and heat treatment in a single operation, whereby upon heating the TWB, itis stamped and held between cold tools to quench the component to room temperature. The materialtherefore undergoes temperature, strain rate or strain path changes during the operation. In thispaper, a finite element model (FEM) was developed to investigate the formability and deformationcharacteristics of the TWBs under HFQ® conditions. Experimental results, i.e. strain distribution,were used to compare and validate the simulation results. A good agreement between theexperiment and simulation has been achieved. The developed temperature, strain rate and strainpath dependent forming limit prediction model has been implemented into FE simulation to capturethe complicated failure features of the HFQ® formed TWBs. It is found from both experiment andsimulation that the forming speed has important effects on the occurrence of failure position, wherethe failure mode for the 1.5-2 mm TWBs may change from localised circumferential necking toparallel weld necking.HFQ® is a registered trademark of Impression Technologies Ltd.
Zhang Q, Ji K, El Fakir O, et al., 2016, Determination of processing windows for the hot stamping of AA7075, Key Engineering Materials, Vol: 716, Pages: 402-412, ISSN: 1013-9826
Hot stamping of aluminium alloys is a tailored forming process, with the assignedprocessing windows determining the quality ofeachhot stampedcomponent in terms of its post-formstrength. In this work, a processing window calculator, ‘Tailor’, was developed in order to define theoptimal processing parameters that should be used in a production line to successfully produce acomponent with the desired post-form strength using hot stamping. ‘Tailor’ was developed using theresults of forming tests, air-cooling tests and multi-stage artificial ageing tests,which providedguidance on the values for the die closing force, transfer time and artificial ageing time to be used inthehot stamping process. The effectiveness of ‘Tailor’ was demonstrated in two case studies.
Wang A, Zheng Y, Liu J, et al., 2016, Knowledge Based Cloud FE simulation – data-driven material characterization guidelines for the hot stamping of aluminium alloys, 10th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes, Numisheet 2016, Publisher: IOP Publishing, Pages: 032042-032042, ISSN: 1742-6588
The Knowledge Based Cloud FEA (KBC-FEA) simulation technique allows multi-objective FE simulations to be conducted on a cloud-computing environment, which effectively reduces computation time and expands the capability of FE simulation software. In this paper, a novel functional module was developed for the data mining of experimentally verified FE simulation results for metal forming processes obtained from KBC-FE. Through this functional module, the thermo-mechanical characteristics of a metal forming process were deduced, enabling a systematic and data-driven guideline for mechanical property characterization to be developed, which will directly guide the material tests for a metal forming process towards the most efficient and effective scheme. Successful application of this data-driven guideline would reduce the efforts for material characterization, leading to the development of more accurate material models, which in turn enhance the accuracy of FE simulations.
Luan X, Liu X, Fang H, et al., 2016, Characterization of the interfacial heat transfer coefficient for hot stamping processes, The 10th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes, Numisheet 2016, Publisher: IOP Publishing, Pages: 032079-032079, ISSN: 1742-6588
In hot stamping processes, the interfacial heat transfer coefficient (IHTC) between the forming tools and hot blank is an essential parameter which determines the quenching rate of the process and hence the resulting material microstructure. The present work focuses on the characterization of the IHTC between an aluminium alloy 7075-T6 blank and two different die materials, cast iron (G3500) and H13 die steel, at various contact pressures. It was found that the IHTC between AA7075 and cast iron had values 78.6% higher than that obtained between AA7075 and H13 die steel. Die materials and contact pressures had pronounced effects on the IHTC, suggesting that the IHTC can be used to guide the selection of stamping tool materials and the precise control of processing parameters.
Chan TY, Hu Y, Gharbi MM, et al., 2016, The friction coefficient evolution of a MoS2/WC multi-layer coating system during sliding wear, The 10th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes, Numisheet 2016, Publisher: IOP Publishing: Conference Series, Pages: 032081-032081, ISSN: 1742-6588
This paper discusses the evolution of friction coefficient for the multi-layered Molybdenum Disulphide (MoS2) and WC coated substrate during sliding against Aluminium AA 6082 material. A soft MoS2 coating was prepared over a hard WC coated G3500 cast iron tool substrate and underwent friction test using a pin-on-disc tribometer. The lifetime of the coating was reduced with increasing load while the Aluminium debris accumulated on the WC hard coating surfaces, accelerated the breakdown of the coatings. The lifetime of the coating was represented by the friction coefficient and the sliding distance before MoS2 coating breakdown and was found to be affected by the load applied and the wear mechanism.
Sun C, Wang B, Politis DJ, et al., 2016, Prediction of earing in TWIP steel sheets based on coupled twinning crystal plasticity model, International Journal of Advanced Manufacturing Technology, ISSN: 0268-3768
By combining the nonlinear finite element analysis techniques and crystal plasticity theory, the macroscopic mechanical behaviour of crystalline material, the texture evolution and earing type characteristics are simulated accurately. In this work, a crystal plasticity model exhibiting deformation twinning is introduced based on the crystal plasticity theory and saturation-type hardening laws for FCC metal Fe-22Mn-0.6C twinning-induced plasticity (TWIP) steel. Based on the crystal plasticity finite element (CPFE) model and parameters which have been determined for TWIP steel, a simplified finite element model for deep drawing process is promoted by using crystal plasticity constitutive model. The earing characteristics in typical deep drawing process are well simulated. Further, the earing profile and drawing forces are calculated and compared with the experimental results from the references. Meanwhile, the impacts of drawing coefficient and initial texture on the earing characteristics are investigated for controlling the earing. According to the result of the simulation, earing rate manifests a downward trend with the drawing coefficient increasing, and two different earing types of 6-0°/60° and 4-0°/90° occur with the brass, cube and gauss type of initial texture. [Figure not available: see fulltext.]
Wang L, Dean T, Lin J, 2016, Innovation, Development and Implementation of the HFQ® Process, Third International Conference on Advanced High Strength Steel and Press Hardening(ICHSU 2016), Publisher: World Scientific
Wang A, Zhong K, El Fakir O, et al., 2016, Springback analysis of AA5754 after hot stamping: experiments and FE modelling, International Journal of Advanced Manufacturing Technology, Vol: 89, Pages: 1339-1352, ISSN: 1433-3015
In this paper, the springback of the aluminium alloyAA5754 under hot stamping conditions was characterised understretch and pure bending conditions. It was found thatelevated temperature stamping was beneficial for springbackreduction, particularly when using hot dies. Using cold dies,the flange springback angle decreased by 9.7 % when theblank temperature was increased from 20 to 450 °C, comparedto the 44.1 % springback reduction when hot dies were used.Various other forming conditions were also tested, the resultsof which were used to verify finite element (FE) simulationsof the processes in order to consolidate the knowledge ofspringback. By analysing the tangential stress distributionsalong the formed part in the FE models, it was found thatthe springback angle is a linear function of the averagethrough-thickness stress gradient, regardless of the formingconditions used.
Luan X, Zhang Q, El Fakir O, et al., 2016, Uni-Form: a pilot production line for hot/warm sheet metal forming integrated in a cloud based SMARTFORMING platform, The 3rd International Conference on Advanced High Strength Steel and Press Hardening (ICHSU2016), Publisher: World Scientific
Warm/hot stamping is a promising technology for manufacturing high-strength, lightweight, complexshaped components from high strength aluminum alloys. It is well known that the formability and highpost-form strength of aluminum alloys are highly temperature sensitive, i.e. manufacturing operationsconducted at elevated temperatures could affect their microstructures, leading to variations in thestrength of final products. Therefore, the processing routes including forming operations, secondaryfabrications, room temperature storage and high temperature curing cycles must be plannedstrategically to ensure the quality of final products. In the present research, a novel processing routeplanning system has been finalized and integrated to an online multi-objective platformSMARTFORMING, enabling processing route optimization on a cloud computing environment. Thesystem consists of two major functional modules: ‘Tailor’ (processing route optimization) and ‘UniForm’(a pilot production line controlled on a cloud based platform for verifying the effectiveness andefficiency of the processing routes).
Hu Y, Zheng Y, Wang L, et al., 2016, Investigation of galling behaviours between an aluminium alloy and metal forming tool, The 3rd International Conference on Advanced High Strength Steel and Press Hardening, ICHSU 2016, Publisher: World Scientific
Hot stamping of Aluminium alloys is a process receiving increased interest from the automotive industry. However, during this process, galling, which has been recognized as one of the major drawbacks, limits the tool life and restricts the complexity and quality of the product. In order to improve the feasibility of this forming technology, an understanding of the mechanism of galling is necessary. The aim of the present study is to investigate the galling behaviours between AA6082 and two advanced anti-wear coatings, CrN and AlCrN. The study was conducted with pin-on-disc experiments at an elevated temperature. The main focus of the study is on the quantitatively measurement of galling and identifying the material transfer mechanisms between Aluminium and tool surface.
Zheng Y, Hu Y, Gharbi MM, et al., 2016, Development of coating design guidelines for a sheet metal forming tool – a feasibility study, The 10th International Tooling Conference, Tool 2016
The application of hard coatings to metal forming tools is essential in order to obtain lower interfacial friction coefficient and extended tool life. By considering friction and wear as interactive responses from a coating tribo-system, an interactive friction model developed recently has enabled the prediction of the friction coefficient evolution and the coating breakdown. In the present research, the interactive friction model was implemented in the FE simulation of a sheet metal forming process, via a multi-objective cloud FEA system. The wear distribution on the punch, die and blank holder has been visualised, which has shown that wear is strongly dependent on the forming parameters, such as blank holding force. Based on these simulation results, predictions can be made for the remaining coating thicknesses. Moreover, preliminary guidelines are presented on the coating design to enable an optimised coating thickness distribution.
Wang A, Zheng Y, Liu J, et al., 2016, Knowledge based cloud FE simulation a multi-objective FEA system for advanced FE simulation of hot stamping process, The 10th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes, Numisheet 2016, Publisher: IOP Publishing, ISSN: 1742-6588
. A knowledge Based Cloud (KBC) FE simulation technique has been developed to enable advanced, efficient and multi-objective finite element analyses (FEA), which operates on a cloud computing environment. The core FE simulation is conducted using a commercial FE code, e.g. PAM-STAMP, and its capability is enhanced through the implementation of advanced functional modules instead of user defined sub-routines. KBC-FE simulation offers great flexibility and variability to engineers as modules could be used collectively or individually. In this paper, case studies were conducted for the hot stamping of tailor welded blanks. Multi-objective FE simulations were performed for ‘Forming Limit’ prediction under non-isothermal and non-linear loading conditions. In addition, ‘Tool-life’ prediction was conducted under multi-cycle loading conditions.
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