299 results found
Pan R, Pirling T, Zheng J, et al., 2019, Quantification of thermal residual stresses relaxation in AA7xxx aluminium alloy through cold rolling, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, Vol: 264, Pages: 454-468, ISSN: 0924-0136
Lyu F, Li Y, Huang X, et al., 2019, An investigation of creep age forming of AA7B04 stiffened plates: Experiment and FE modelling, Journal of Manufacturing Processes, Vol: 37, Pages: 232-241, ISSN: 1526-6125
© 2018 Creep age forming (CAF) of aluminium alloy 7B04 (AA7B04) stiffened plates has been experimentally and numerically investigated in this study. Creep-ageing experiments of AA7B04-T651 were conducted under different tensile stress levels at 140 °C for up to 20 h, and a set of unified constitutive equations was calibrated based on the experimental results of the evolutions of creep strain, yield strength and precipitate size, which was implemented into ABAQUS for CAF process modelling. CAF experiments and corresponding simulations of AA7B04 stiffened plates were then carried out and the effect of stiffener height and die radius on springback and yield strength was studied. It was found that the springback percentage decreases with increasing stiffener height and decreasing forming die radius, and the yield strength is slightly lower in the stiffener than in the skin of the CAFed stiffened plates due to stress effect on ageing progression. A good agreement has been achieved between experimental and corresponding FE results, with maximum deviations of 6.7% and 3.3% respectively for springback and yield strength.
Shao Z, Jiang J, Lin J, 2018, Feasibility study on direct flame impingement heating applied for the solution heat treatment, forming and cold die quenching technique, JOURNAL OF MANUFACTURING PROCESSES, Vol: 36, Pages: 398-404, ISSN: 1526-6125
, 2018, Professor Trevor A. Dean and his contribution to the Journal, International Journal of Machine Tools and Manufacture, Vol: 133, Pages: 1-3, ISSN: 0890-6955
Kopec M, Wang K, Wang Y, et al., 2018, Feasibility study of a novel hot stamping process for Ti6Al4V alloy
© The Authors, published by EDP Sciences, 2018. To investigate the feasibility of a novel hot stamping process for the Ti6Al4V titanium alloy using low temperature forming tools, mechanical properties of the material were studied using hot tensile tests at a temperature range of 600 - 900°C with a constant strain rate of 1s-1. Hot stamping tests were carried out to verify the feasibility of this technology and identify the forming window for the material. Results show that when the deformation temperature was lower than 700°C, the amount of elongation was less than 20%, and it also had little change with the temperature. However, when the temperature was higher than 700°C, a good ductility of the material can be achieved. During the forming tests, parts failed at lower temperatures (600°C) due to the limited formability and also failed at higher temperatures (950°C) due to the phase transformation. The post-form hardness firstly decreased with the temperature increasing due to recovery and then increased due to the phase transformation. Qualified parts were formed successfully between temperatures of 750 - 850°C, which indicates that this new technology has a great potential in forming titanium alloys sheet components.
© The Authors, published by EDP Sciences, 2018. Application of a newly developed flexible forming tool to creep age forming (CAF) process has been investigated in this study. The flexible tool mainly consists of sparsely distributed forming pins, splines and elastomeric sheet. The effect of key factors related to the forming tool on the shape of the formed parts has been studied through various CAF experiments. The key factors investigated in this study include: the interval between forming pins, the arrangement of pins, the accuracy requirement of pin height and the material of splines. It has been found that reducing the interval between pins can efficiently smooth the shape of CAFed plates. The feasibility of asymmetric arrangement of pins has been proven, which can decrease the number of used pins, reduce tool weight, and increase efficiency. The forming results are very sensitive to the pin height, thus the experimental set-up error should be carefully controlled. Additionally, compared with mild steel, spring steel is more suitable as the spline material.
© The Authors, published by EDP Sciences, 2018. The evolution of mechanical properties of a third generation Al-Cu-Li alloy, AA2050, with different initial tempers (T34 and as-quenched (WQ)) during creep-ageing has been investigated and analysed in this study. A set of creep-ageing tests under 150 MPa at 155 °C for up to 24 h was carried out for both initial temper conditions and tensile tests were performed subsequently to acquire the main mechanical properties of the creep-aged alloys, including the yield strength, ultimate tensile strength (UTS) and uniform elongation. Precipitation behaviour of the T34 and WQ AA2050 alloys has been summarised and successfully explains the detailed evolutions of the obtained mechanical properties of the alloy with these two initial tempers during creep-ageing. The results indicate that the T34 alloy can be a better choice for creep age forming (CAF) process compared with WQ alloy, as it provides better yield strength and uniform elongation properties concurrently after creep-ageing. In addition, a work hardening rate analysis has been carried out for all the creep-aged alloys, helping to reveal the detailed dislocation/precipitates interaction mechanisms during plastic deformation in the creep-aged T34 and WQ AA2050 alloys.
Li Y, Shi Z, Lin J, et al., 2018, Effect of machining-induced residual stress on springback of creep age formed AA2050 plates with asymmetric creep-ageing behaviour, INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE, Vol: 132, Pages: 113-122, ISSN: 0890-6955
Shao Z, Lin J, Ganapathy M, et al., 2018, Experimental and modelling techniques for hot stamping applications, Procedia Manufacturing, Vol: 15, Pages: 6-13, ISSN: 2351-9789
Hot stamping techniques have been developed for the production of complex-shaped components since the 1970s, increasingly used for the automotive industry. The application of these techniques includes hot stamping of boron steel for critical automobile safety components, and solution heat treatment, forming and cold die quenching (HFQ®) for forming complex-shaped high strength aluminium panels of automobile bodies and chassis structures. The developed forming techniques need dedicated experimental testing methods to be improved for characterising the thermomechanical behaviour of materials at the hot stamping conditions, and advanced materials modelling techniques to be developed for hot stamping applications. In this paper, requirements for thermomechanical tests and difficulties for hot stamping applications are introduced and analysed. The viscoplastic modelling techniques have been developed for hot stamping applications. Improved experimental methods have been proposed and used in order to obtain accurate thermomechanical uniaxial tensile test data and determine forming limits of metallic materials under hot stamping conditions.
Li Y, Shi Z, Yang Y-L, et al., 2018, Experimental and numerical study of creep age forming of AA2050 plates with sparse multi-point flexible forming tool, Metal Forming 2018, 17th International Conference on Metal Forming, Publisher: Elsevier, Pages: 1016-1023, ISSN: 2351-9789
Creep age forming of an Al-Cu-Li alloy (AA2050-T34) with an asymmetric tension/compression creep-ageing behaviour has been experimentally and numerically investigated in this study. Creep age forming experiments of plates with different thicknesses have been carried out to form doubly curved shapes using a recently developed sparse multi-point flexible forming tool. Corresponding FE model for creep age forming, incorporating the material model that describes the stress-strain relation and asymmetric creep-ageing behaviour of the alloy, has been developed through PAM-STAMP. The flexible forming tool can generate various tool shapes for creep age forming and is ideal for innovative trials. Stress concentration was found in some forming pin areas of the loaded plate. With larger initial loaded plastic strain and higher creep strain generated in these local areas, bumps may occur in formed shapes after creep age forming under certain circumstances. It is shown that the FE model is able to predict the formed shape accurately for thicker plates and can be used for tool set-up optimisation.
Politis DJ, Politis NJ, Lin J, et al., 2018, A review of force reduction methods in precision forging axisymmetric shapes, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, Vol: 97, Pages: 2809-2833, ISSN: 0268-3768
Xiao W, Wang B, Zheng K, et al., 2018, A study of interfacial heat transfer and its effect on quenching when hot stamping AA7075, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, Vol: 18, Pages: 723-730, ISSN: 1644-9665
Zheng J-H, Lin J, Lee J, et al., 2018, A novel constitutive model for multi-step stress relaxation ageing of a pre-strained 7xxx series alloy, INTERNATIONAL JOURNAL OF PLASTICITY, Vol: 106, Pages: 31-47, ISSN: 0749-6419
Chung T-F, Yang Y-L, Hsiao C-N, et al., 2018, Morphological evolution of GP zones and nanometer-sized precipitates in the AA2050 aluminium alloy, International Journal of Lightweight Materials and Manufacture, ISSN: 2588-8404
Shao Z, Li N, Lin J, et al., 2018, Strain measurement and error analysis in thermo-mechanical tensile tests of sheet metals for hot stamping applications, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 232, Pages: 1994-2008, ISSN: 0954-4062
Pan R, Shi Z, Davies CM, et al., 2018, An integrated model to predict residual stress reduction by multiple cold forging operations in extra-large AA7050 T-section panels, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART B-JOURNAL OF ENGINEERING MANUFACTURE, Vol: 232, Pages: 1319-1330, ISSN: 0954-4054
Li Y, Shi Z, Lin J, et al., 2018, FE simulation of asymmetric creep-ageing behaviour of AA2050 and its application to creep age forming, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, Vol: 140, Pages: 228-240, ISSN: 0020-7403
Chung T-F, Yang Y-L, Huang B-M, et al., 2018, Transmission electron microscopy investigation of separated nucleation and in-situ nucleation in AA7050 aluminium alloy, ACTA MATERIALIA, Vol: 149, Pages: 377-387, ISSN: 1359-6454
Zheng K, Lin J, Wu G, et al., 2018, EXPERIMENTAL INVESTIGATION AND MODELLING OF HOT FORMING B4C/AA6O61 LOW VOLUME FRACTION REINFORCEMENT COMPOSITES, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, Vol: 56, Pages: 457-469, ISSN: 1429-2955
Zhou W, Lin J, Dean TA, et al., 2018, Analysis and modelling of a novel process for extruding curved metal alloy profiles, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, Vol: 138, Pages: 524-536, ISSN: 0020-7403
Chavoshi SZ, Jiang J, Wang Y, et al., 2018, Density-based constitutive modelling of P/M FGH96 for powder forging, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, Vol: 138, Pages: 110-121, ISSN: 0020-7403
Zheng K, Lee J, Xiao W, et al., 2018, Experimental Investigations of the In-Die Quenching Efficiency and Die Surface Temperature of Hot Stamping Aluminium Alloys, METALS, Vol: 8, ISSN: 2075-4701
Kopec M, Wang K, Politis DJ, et al., 2018, Formability and microstructure evolution mechanisms of Ti6Al4V alloy during a novel hot stamping process, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 719, Pages: 72-81, ISSN: 0921-5093
Zhou W, Lin J, Dean TA, et al., 2018, Feasibility studies of a novel extrusion process for curved profiles: Experimentation and modelling, International Journal of Machine Tools and Manufacture, Vol: 126, Pages: 27-43, ISSN: 0890-6955
© 2017 The work described in this paper concerns a novel method for directly forming curved profiles/sections from billets in one extrusion operation using two opposing punches. Its mechanics are based on internal differential material flow, and it has been given the acronym, differential velocity sideways extrusion (DVSE). A tool set enabling sideways extrusion to be performed using opposing punches moving with different velocities was used for a series of experiments in which punch velocity ratio and extrusion ratio were process parameters. Plasticine was used as a model work-piece material and a series of compression tests were undertaken, to determine its constitutive properties and gain an estimate of work-piece die friction for use in process simulation. Curvature of extrudate can be controlled and varied using a difference between the velocities of the two punches, defined by velocity ratio. Greater curvature is achieved with lower velocity ratio. Curvature is also dependent on extrusion ratio, an increase in which increases curvature, although curvature is less sensitive to it than to velocity ratio. The extent of work-piece flow velocity gradient across the die exit orifice, which causes curvature, has been identified. Severe plastic deformation of the extrudate occurs in a way similar to channel angular extrusion (CAE), thus a greatly promoted effective strain level is achieved, though it is not always uniform across a section. The inner bending region of an extrudate experiences maximum localised effective strain, which decreases with decrease in curvature. To the authors' knowledge this is the first publication in which extrudate curvature is deliberately induced using opposing punches with differential velocities. Although only fixed velocity ratio values have been used in the work described in this paper the ability to change during operation exists and the process has the potential for the production of a profile with different curvature along it
Zhou W, Shi Z, Lin J, 2018, Upper bound analysis of differential velocity sideways extrusion process for curved profiles using a fan-shaped flow line model, International Journal of Lightweight Materials and Manufacture, Vol: 1, Pages: 21-32, ISSN: 2588-8404
Shao Z, Bai Q, Li N, et al., 2018, Experimental investigation of forming limit curves and deformation features in warm forming of an aluminium alloy, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART B-JOURNAL OF ENGINEERING MANUFACTURE, Vol: 232, Pages: 465-474, ISSN: 0954-4054
Ganapathy M, Li N, Lin J, et al., 2018, A Novel Grip Design for High-Accuracy Thermo-Mechanical Tensile Testing of Boron Steel under Hot Stamping Conditions, EXPERIMENTAL MECHANICS, Vol: 58, Pages: 243-258, ISSN: 0014-4851
Zheng J-H, Pan R, Li C, et al., 2018, Experimental investigation of multi-step stress-relaxation-ageing of 7050 aluminium alloy for different pre-strained conditions, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 710, Pages: 111-120, ISSN: 0921-5093
Politis DJ, Politis NJ, Lin J, et al., 2018, An analysis of the tooth stress distribution of forged bi-metallic gears, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 232, Pages: 124-139, ISSN: 0954-4062
, 2018, Effect of the thickness reduction of specimens on the limit strains in thermomechanical tensile tests for hot-stamping studies, Manufacturing Review, Vol: 5
© C. Lane et al., Published by EDP Sciences 2018. Sheet metal formability under hot stamping conditions has been evaluated using a novel planar testing system developed previously, being used within a Gleeble machine. Nevertheless, the specimen design with the central recess was not standardised, and the thickness reduction was not applied to the dog-bone type of specimen for testing at the uniaxial straining state. In this paper, effect of thickness reduction of dog-bone specimens on limit strain measurement under hot stamping conditions is investigated, and two types of dog-bone specimens without and with central recess are presented. Thermomechanical uniaxial tensile tests were performed at various deformation temperatures and strain rates, ranging from 370-510 °C and 0.01-1/s, respectively, by using the developed biaxial testing system in the Gleeble. The distributions of temperature and axial strain along gauge region of the two types of specimen were measured and compared. The specimen with consistent thickness had a better uniformity of temperature and strain distributions, compared to that with thickenss reduction. Forming limits for both types of specimen were also determined using the section-based international standard method. It is found that the accuracy of the calculation of forming limits based on the use of specimen with thickness reduction was highly dependent on the selection of the stage of the deformation of the specimen.
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