Imperial College London

ProfessorJianguoLin

Faculty of EngineeringDepartment of Mechanical Engineering

Head/Professor in Mechanics of Materials Division
 
 
 
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Contact

 

+44 (0)20 7594 7082jianguo.lin

 
 
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Assistant

 

Miss Valerie Crawford +44 (0)20 7594 7083

 
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Location

 

524City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

256 results found

Liu J, Wang A, Gao H, El Fakir O, Luan X, Wang L, Lin Jet al., Studies on the Hot Forming and Cold-die Quenching of AA6082 TailorWelded Blanks, Key Engineering Materials, 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.

JOURNAL ARTICLE

Liu J, Wang A, Zheng Y, Liu X, Gandra J, Beamish K, Wang L, Lin Jet al., Hot stamping of AA6082 tailor welded blanks for automotive applications, International Conference on Technology of Plasticity 2017, Publisher: Elsevier, ISSN: 1877-7058

Friction stir welded (FSWed) AA6082 tailor welded blanks (TWBs), with gauges of 2-2.5 and 3-5 mm, have been prepared and successfully formed into automotive panel components (B-Pillar section parts). Experimental results indicated that the post-form strength, in terms of hardness, varied from location to location on the final parts. Moreover, the strength is found to be highly dependent on the blank gauges, with the average hardness values being HV 110 and HV 98 for the 2-2.5 mm and 3-5 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 during the forming process. A typical continuous cooling precipitation (CCP) diagram for AA6082 was implemented into the verified simulation data to assess the post-form strength of the TWB parts. 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. HFQ® is a registered trademark of Impression Technologies Ltd.

CONFERENCE PAPER

Pan R, Shi Z, Davies CM, Li C, Kaye M, Lin Jet al., 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, ISSN: 0954-4054

A finite element (FE) model has been developed to determine the effectiveness of acold compression technique to reduce the large residual stresses generated fromquenching solution heat treated T-Section components of aluminium alloy AA7050. Tocompress long components, a multi-step process is required with some amount ofoverlap. A parametric study has been performed to determine the effect of thecompression ratio, friction coefficient, length of overlap and length of the T-sectioncomponent on the residual stress distribution post quenching and after subsequent coldcompression. Generally a percentage reduction in the peak residual stress of over 90%was found. The optimal parameters for residual stress relief by cold compression havebeen suggested from the cases considered.

JOURNAL ARTICLE

Shao Z, Li N, Lin J, A New Damage Model for Predicting Forming Limits under Hot Stamping Conditions, PLASTICITY 2017

CONFERENCE PAPER

Shi Z, Wang Y, Lin J, Dean T, balint D, Stanton M, Watson Det al., An Investigation, Using Standard Experimental Techniques, to Determine FLCs at Elevated Temperature for Aluminium Alloys, The 3rd International Conference on New Forming Technology

An experimental procedure has been developedfor the determination of FLCs at elevated temperatures. TheGOM ARGUS system was employed for measuring surfacestrain based on pre-applied grids (pattern), and limit strains weredetermined according to the ISO 12004-2:2008 standard.Forming limit curves (FLCs) have been determined for AA5754under warm forming conditions in an isothermal environment.The tests were carried out at various temperatures up to 300oCand forming speeds ranging from 5 – 300 mm s-1. Results revealthe significant effect of both temperature and forming speed onFLCs of AA5754. Formability increases with increasingtemperature above 200oC. Formability also increases withdecreasing speed. The presented FLC results show that the bestformability exists at low forming speed and the high temperatureend of the warm forming range.

CONFERENCE PAPER

shao Z, Li N, lin JIANGUO, Continuum Damage Mechanics-Based Materail Models For Formability Prediction Of AA6082 Under Hot Stamping Conditions, Materials Modelling and Testing for Sheet Metal Forming IDDRG 2017

CONFERENCE PAPER

Bai Q, Mohamed M, Shi Z, Lin J, Dean Tet al., 2017, Application of a continuum damage mechanics (CDM)-based model for predicting formability of warm formed aluminium alloy, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, Vol: 88, Pages: 3437-3446, ISSN: 0268-3768

JOURNAL ARTICLE

Dong Y, Zheng K, Fernandez J, Li X, Dong H, Lin Jet al., 2017, Experimental investigations on hot forming of AA6082 using advanced plasma nitrocarburised and CAPVD WC: C coated tools, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, Vol: 240, Pages: 190-199, ISSN: 0924-0136

JOURNAL ARTICLE

Ganapathy M, Li N, Lin JG, Abspoel M, Bhattacharjee Det al., 2017, Test-Piece and Test-Rig Designs to Obtain High Accuracy Experimental Data for Boron Steel at Hot Stamping Conditions, 3rd International Conference on Advanced High Strength Steel and Press Hardening (ICHSU), Publisher: WORLD SCIENTIFIC PUBL CO PTE LTD, Pages: 109-113

CONFERENCE PAPER

Huo Y, Lin J, Bai Q, Wang B, Tang X, Ji Het al., 2017, Prediction of microstructure and ductile damage of a high-speed railway axle steel during cross wedge rolling, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, Vol: 239, Pages: 359-369, ISSN: 0924-0136

JOURNAL ARTICLE

Ji H, Liu J, Wang B, Tang X, Lin J, Huo Yet al., 2017, Microstructure evolution and constitutive equations for the high-temperature deformation of 5Cr21Mn9Ni4N heat-resistant steel, JOURNAL OF ALLOYS AND COMPOUNDS, Vol: 693, Pages: 674-687, ISSN: 0925-8388

JOURNAL ARTICLE

Kaye MC, Balint D, Lin J, Farrugia Det al., 2017, Test-piece design for experimental and numerical evaluation of damage in relation to spatial triaxial stress inversion, INTERNATIONAL JOURNAL OF DAMAGE MECHANICS, Vol: 26, Pages: 588-607, ISSN: 1056-7895

JOURNAL ARTICLE

Kong XX, Li N, O'Keeffe R, Lin JGet al., 2017, Experimental Investigation on the Accuracy of Uniaxial Tensile Data of AA6082 Under HFQ (R) Conditions, 3rd International Conference on Advanced High Strength Steel and Press Hardening (ICHSU), Publisher: WORLD SCIENTIFIC PUBL CO PTE LTD, Pages: 390-394

CONFERENCE PAPER

Li N, Zheng J, Zheng K, Lin J, Davies Cet al., 2017, A fast ageing method for stamped heat-treatable alloys, WO2017021742 A1

PATENT

Li Y, Shi Z, Lin J, Yang Y-L, Rong Qet al., 2017, Extended application of a unified creep-ageing constitutive model to multistep heat treatment of aluminium alloys, MATERIALS & DESIGN, Vol: 122, Pages: 422-432, ISSN: 0264-1275

JOURNAL ARTICLE

Li Y, Shi Z, Lin J, Yang Y-L, Rong Q, Huang B-M, Chung T-F, Tsao C-S, Yang J-R, Balint DSet al., 2017, A unified constitutive model for asymmetric tension and compression creep-ageing behaviour of naturally aged Al-Cu-Li alloy, INTERNATIONAL JOURNAL OF PLASTICITY, Vol: 89, Pages: 130-149, ISSN: 0749-6419

JOURNAL ARTICLE

Mohamed M, Lin J, Foster A, Dean T, Dear Jet al., 2017, Formability investigation using a new test design for hot stamping processes, International Journal of Materials and Product Technology, Vol: 54, Pages: 3-19, ISSN: 0268-1900

© 2017 Inderscience Enterprises Ltd. Hot stamping is widely used in the forming of lightweight automotive panel components. The process optimisation requires knowledge of constitutive relations of work-piece material but assessment of formability of materials in hot stamping conditions is exceptionally challenging. A testing method and corresponding specimen design are developed in this paper for evaluating formability of materials in hot stamping conditions. A series of tests have been carried out for AA6082 aluminium alloy, at different forming rates and failure modes have been analysed. A set of stress-state dependent damage equations for AA6082 is introduced and this has been input into the FE code, ABAQUS. An FE model is developed and validated from the experimental results. Failure modes at particular forming conditions are predicted and designed specimen shapes are optimised for different forming conditions. It is concluded that work-piece design is related to ductility for hot stamping conditions and recommendations for work-piece design are given.

JOURNAL ARTICLE

Mohamed M, Lin J, Foster A, Dean T, Dear Jet al., 2017, Formability investigation using a new test design for hot stamping processes, INTERNATIONAL JOURNAL OF MATERIALS & PRODUCT TECHNOLOGY, Vol: 54, Pages: 3-19, ISSN: 0268-1900

JOURNAL ARTICLE

Shao Z, Li N, Lin J, Dean Tet al., 2017, Formability evaluation for sheet metals under hot stamping conditions by a novel biaxial testing system and a new materials model, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, Vol: 120, Pages: 149-158, ISSN: 0020-7403

JOURNAL ARTICLE

Wang A, Zhong K, El Fakir O, Liu J, Sun C, Wang L-L, Lin J, Dean TAet al., 2017, Springback analysis of AA5754 after hot stamping: experiments and FE modelling, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, Vol: 89, Pages: 1339-1352, ISSN: 0268-3768

JOURNAL ARTICLE

Wang LL, Dean T, Lin JG, 2017, Innovation, Development and Implementation of the HFQ (R) Process, 3rd International Conference on Advanced High Strength Steel and Press Hardening (ICHSU), Publisher: WORLD SCIENTIFIC PUBL CO PTE LTD, Pages: 289-300

CONFERENCE PAPER

Wang S, Fang S, Shi Z, Jiang J, Zhou X, Lin Jet al., 2017, Direct powder forging of PM nickel-based superalloy: densification and recrystallisation, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, Vol: 88, Pages: 2661-2670, ISSN: 0268-3768

JOURNAL ARTICLE

Wu P, Wang B, Lin J, Zuo B, Li Z, Zhou Jet al., 2017, Investigation on metal flow and forming load of bi-metal gear hot forging process, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, Vol: 88, Pages: 2835-2847, ISSN: 0268-3768

JOURNAL ARTICLE

Zheng K, Lee J, Lin J, Dean TAet al., 2017, A buckling model for flange wrinkling in hot deep drawing aluminium alloys with macro-textured tool surfaces, INTERNATIONAL JOURNAL OF MACHINE TOOLS & MANUFACTURE, Vol: 114, Pages: 21-34, ISSN: 0890-6955

JOURNAL ARTICLE

Zheng K, Lee J, Politis DJ, Li N, Lin J, Dean TAet al., 2017, An analytical investigation on the wrinkling of aluminium alloys during stamping using macro-scale structural tooling surfaces, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, Vol: 92, Pages: 481-495, ISSN: 0268-3768

JOURNAL ARTICLE

Zheng K, Politis DJ, Lin J, Dean TAet al., 2017, An experimental and numerical investigation of the effect of macro-textured tool surfaces in hot stamping, International Journal of Material Forming, Vol: 10, Pages: 241-254, ISSN: 1960-6206

© 2015, The Author(s). This paper presents a method of increasing draw-ability of materials in hot stamping processes using forming tools with macro-scale textures on the tool surfaces. Firstly, a series of tool texture designs and orientations were presented and a test programme was designed for the experimental investigation. Top-hat shape drawing experiments in cold and hot stamping conditions were conducted to evaluate the effect of macro-scale tool surface textures on the material drawing. Texture directional and texture feature effects of the blankholders on the draw-ability of the material have been investigated. A finite element model of the top-hat drawing process with textured tool surfaces has been established and validated from experimental data. Further FE process modelling has been carried out and the effects of texture features and forming speed have been studied. The relationships between texture designs and material drawing results have been analysed. The developed FE model can provide a guide to design the geometry of tool textures and optimise the hot stamping process parameters.

JOURNAL ARTICLE

Zuo B, Wang B, Li Z, Li N, Lin Jet al., 2017, An investigation of involute and lead deflection in hot precision forging of gears, INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, Vol: 88, Pages: 3017-3030, ISSN: 0268-3768

JOURNAL ARTICLE

Fang S, Shi Z, Bai Q, Jiang J, Wang SY, Lin JGet al., 2016, An investigation of direct powder forging of nickel superalloy FGH96, Pages: 793-799, ISSN: 1013-9826

© 2016 Trans Tech Publications, Switzerland. Powder metallurgy (PM) nickel-based superalloy has been widely used in high temperature applications and is most commonly manufactured using hot isostatic pressing (HIP). However, HIP is an expensive process and takes a long time at high temperature which leads to the formation of networks of prior particle boundaries (PPBs). In this study, a recently developed processing method-direct powder forging (DPF) was employed to produce a PM nickel-based superalloy component, using a single acting hydraulic press under normal atmosphere. EBSD study has been conducted for its microstructure, grains size distribution, and grain boundary misorientation; and mechanical testing has been carried out for its hardness and tensile properties at room temperature and 650°C. It has been found that the DPFed material has reached full density in the whole component. Networks of PPBs have been broken in the direct powder forged FGH96 alloy. Compared with HIPed FGH96 alloy, the DPFed material has a substantially higher recystallisation nucleation degree and more recrystallised sub-grains. After heat treatment, the tensile properties of the direct powder forged FGH96 alloy match or surpass those of the material produced by HIP plus isothermal forging.

CONFERENCE PAPER

Feng J, Wang S, Guo Lin J, 2016, Multi-resolution material hardening law for CPFE micro-forming analysis, Pages: 232-239, ISSN: 1013-9826

© 2016 Trans Tech Publications, Switzerland. A new multi-resolution slip system-based material hardening law has been developed for micro-forming simulation using Crystal Plasticity Finite Element (CPFE) Approach. Material hardenings are formulated based on global and local hardening of dislocations for each slip system and defined with distinct physical meaning. Plasticity is assumed to arise solely from crystalline slip and the overall mechanical response with any crystallographic system, such as FCC, BCC, etc, can be addressed by a local hardening parameter, x, from 0 (pure anisotropic) to 1 (fully isotropic). No interaction matrix is necessary, since the latent hardening can be realized by the hardening factor , x , and the new dislocation density based hardening law can be implemented into existing FE software efficiently. The proposed equations are an extension of the existing hardening law from macro mechanics descriptions down to micro mechanics level, therefore unified constitutive equations had been established at multiscale resolution. Some features of the proposed hardening law will be demonstrated with a single cubic crystal under tension load.

CONFERENCE PAPER

Ji H, Liu J, Wang B, Lin J, Tang Xet al., 2016, The process parameters effect of ovality in cross wedge rolling for hollow valve without mandril

© The Authors, published by EDP Sciences, 2016. This paper presents the experimental and numerical results of the effect process parameters on ovality in cross wedge rolling (CWR) for hollow engine valve without mandrel. Numerical simulation model for ovality was established by means of the rigid-plastic finite element modeling (FEM) method for hollow engine valve. The experiments and numerical analyses suggest that the following parameters represent the best conditions for CWR of hollow engine valve: 30°-34° for the forming angle(α), 5°-7° for the stretching angle(β), 0.2-0.3mm for the mold void width(L), and 65%-70% for the area reduction(Ψ).

CONFERENCE PAPER

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