Imperial College London

DrNanLi

Faculty of EngineeringDyson School of Design Engineering

Lecturer
 
 
 
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Contact

 

n.li09

 
 
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Location

 

City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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36 results found

Ganapathy M, Li N, Lin J, Abspoel M, Bhattacharjee Det al., 2017, A Novel Grip Design for High-Accuracy Thermo-Mechanical Tensile Testing of Boron Steel under Hot Stamping Conditions, Experimental Mechanics, Pages: 1-16, ISSN: 0014-4851

© 2017 The Author(s) Achieving uniform temperature within the effective gauge length in thermo-mechanical testing is crucial for obtaining accurate material data under hot stamping conditions. A new grip design for the Gleeble Materials-Simulator has been developed to reduce the long-standing problem of temperature gradient along a test-piece during thermo-mechanical tensile testing. The grip design process comprised two parts. For the first part, the new design concept was analysed with the help of Abaqus coupled Thermal-Electric Finite element simulation through the user defined feedback control subroutine. The second part was Gleeble thermo-mechanical experiments using a dog-bone test-piece with both new and conventional grips. The temperature and strain distributions of the new design were compared with those obtained using the conventional system within the effective gauge length of 40 mm. Temperature difference from centre to edge of effective gauge length (temperature gradient) was reduced by 56% during soaking and reduced by 100% at 700 °C. Consequently, the strain gradient also reduced by 95%, and thus facilitated homogeneous deformation. Finally to correlate the design parameters of the electrical conductor used in the new grip design with the geometry and material of test-piece, an analytical relationship has been derived between the test-piece and electrical conductor.

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

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

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

Shao Z, Li N, Lin J, Dean TAet al., 2017, 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, Pages: 095440621771401-095440621771401, ISSN: 0954-4062

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

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

Li N, Lin J, Balint DS, Dean TAet al., 2016, Experimental characterisation of the effects of thermal conditions on austenite formation for hot stamping of boron steel, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, Vol: 231, Pages: 254-264, ISSN: 0924-0136

JOURNAL ARTICLE

Li N, Lin J, Balint DS, Dean TAet al., 2016, Modelling of austenite formation during heating in boron steel hot stamping processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, Vol: 237, Pages: 394-401, ISSN: 0924-0136

JOURNAL ARTICLE

Li N, Politis D, Foster AD, Lin J, Wang L, Szegda Det 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.

CONFERENCE PAPER

Li N, Shao Z, Lin J, Dean TAet al., 2016, Investigation of uniaxial tensile properties of AA6082 under HFQ® Conditions, Key Engineering Materials, Vol: 716, Pages: 337-344, ISSN: 1013-9826

© 2016 Trans Tech Publications, Switzerland. For a metal forming process, the uniaxial tensile properties of a material are the most fundamental and important properties to investigate. Solution heat treatment, forming and in-die quenching (HFQ®) is a patented process to form complex shape panel components using aluminium alloys at high efficiency and low cost. A Gleeble materials thermo-mechanical simulator was used to conduct uniaxial tensile testing of AA6082 under HFQ® conditions. A set of grips were specially designed to reduce the heat loss of specimen during testing in a Gleeble and allow the strain measurement by using digital image correlation (DIC) system. A large dog-bone specimen with parallel length of 80mm was designed to minimise the temperature gradient along the gauge section. Temperature gradient was measured and uniaxial tensile tests were conducted at the range of deformation temperature of350-535 °C and the range of strain rate of 0.1-4/s. The uniaxial tensile properties of AA6082 at different temperatures and strain rates under HFQ® conditions were summarised and the viscoplastic response of the material was discussed.

JOURNAL ARTICLE

Li N, Sun C, Guo N, Mohamed M, Lin J, Matsumoto T, Liu Cet al., 2016, Experimental investigation of boron steel at hot stamping conditions, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, Vol: 228, Pages: 2-10, ISSN: 0924-0136

JOURNAL ARTICLE

Lin J, Zheng K, Wang L, Li N, El-Fakir O, Dean T, Foster A, Adam Get al., 2016, Material and Process for Preparing and Forming an Aluminium Alloy Material, WO/2016/067045

PATENT

Matsumoto T, Li N, Shi X, Lin Jet al., 2016, An Investigation of Deformation Effects on Phase Transformation in Hot Stamping Processes, SAE INTERNATIONAL JOURNAL OF MATERIALS AND MANUFACTURING, Vol: 9, Pages: 501-505, ISSN: 1946-3979

JOURNAL ARTICLE

Shao Z, Bai Q, Li N, Lin J, Shi Z, Stanton M, Watson D, Dean Tet al., 2016, 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, ISSN: 0954-4054

JOURNAL ARTICLE

Shao Z, Li N, Lin J, Dean TAet al., 2016, Development of a New Biaxial Testing System for Generating Forming Limit Diagrams for Sheet Metals Under Hot Stamping Conditions, EXPERIMENTAL MECHANICS, Vol: 56, Pages: 1489-1500, ISSN: 0014-4851

JOURNAL ARTICLE

Shao Z, Li N, Politis D, Bai Q, Lin Jet al., 2016, A Review on of Forming Limit Prediction and Determination at Elevated Temperatures, 2nd International Conference on Advanced High Strength Steel and Press Hardening (ICHSU2015), Publisher: World Scientific

The evaluation of the formability of sheet material is of great importance for forming complex-shapecomponents in automotive applications. However, for hot and warming forming conditions, thisusually requires formability tests with specialist devices and testing procedures and is difficult toobtain accurate and comparable results due to the lack of testing standards. In this paper, the conceptand development of strain-based forming limit diagram (FLD) are introduced. The testing methodsto experimentally determine the FLD, classified into formability tests and planar tensile tests, arewidely reviewed. The applications of both types to obtain FLD at elevated temperatures for differentforming processes are introduced, and the advantages and disadvantages of the methods areanalysed.

CONFERENCE PAPER

Yang L, Li N, Wang B, Lin J, Zhao H, Ma Wet al., 2016, Unified constitutive modelling for two-phase lamellar titanium alloys at hot forming conditions, MANUFACTURING REVIEW, Vol: 3, ISSN: 2265-4224

JOURNAL ARTICLE

Ganapathy M, Li N, Lin J, Abspoel M, Guido H, Bhattacharjee Det al., 2015, Analysis of new Gleeble tensile specimen design for hot stamping application, 4th International Conference on New Forming Technology (ICNFT), Publisher: E D P SCIENCES, ISSN: 2261-236X

CONFERENCE PAPER

Gao H, Li N, Ho H, Zhang Y, Zhang N, Wang L, Lin Jet al., 2015, Determination of a set of constitutive equations for an Al-Li alloy at SPF conditions, MATERIALS TODAY-PROCEEDINGS, Vol: 2, Pages: 408-413, ISSN: 2214-7853

JOURNAL ARTICLE

Li N, Lin JG, Dean TA, 2015, Development of Unified Viscoplastic-Damage Model for Crashworthiness Analysis of Boron Steel Safety Components with Tailored Microstructures, Applied Mechanics and Materials, Vol: 784, Pages: 427-434

JOURNAL ARTICLE

Li N, Zheng J, Zhang C, Zheng K, Lin J, Dean TAet al., 2015, Investigation on fast and energy-efficient heat treatments of AA6082 in HFQ processes for automotive applications, 4th International Conference on New Forming Technology (ICNFT), Publisher: E D P SCIENCES, ISSN: 2261-236X

CONFERENCE PAPER

Li X, Li N, Zhu Q, Li B, Zhu G, Liu G, Luo J, Lin Jet al., 2015, A Testing System and Method to Generate Forming Limit Diagrams at Elevated Temperatures, CN102749253 B

PATENT

Mohamed M, Li N, Wang L, El Fakir O, Lin J, Dean T, Dear Jet al., 2015, An investigation of a new 2D CDM model in predicting failure in HFQing of an automotive panel, 4th International Conference on New Forming Technology (ICNFT), Publisher: E D P SCIENCES, ISSN: 2261-236X

CONFERENCE PAPER

Li N, Lin J, Dean TA, Dry D, Balint Det al., 2014, Concept validation for selective heating and press hardening of automotive safety components with tailored properties, Key Engineering Materials, Vol: 622-623, Pages: 1124-1131, ISSN: 1013-9826

© (2014) Trans Tech Publications, Switzerland. A new strategy termed selective heating and press hardening, for hot stamping of boron steel parts with tailored properties is proposed in this paper. Feasibility studies were carried out through a specially designed experimental programme. The main aim was to validate the strategy and demonstrate its potential for structural optimisation. In the work, a lab-scale demonstrator part was designed, and relevant manufacturing and property-assessment processes were defined. A heating technique and selective-heating rigs were designed to enable certain microstructural distributions in blanks to be obtained. A hot stamping tool set was designed for forming and quenching the parts. Demonstrator parts of full martensite phase, full initial phase, and differentially graded microstructures have been formed with high dimensional quality. Hardness testing and three point bending tests were conducted to assess the microstructure distribution and load bearing performance of the as-formed parts, respectively. The feasibility of the concept has been validated by the testing results.

JOURNAL ARTICLE

Li N, Lin J, Dean TA, Dry D, Balint Det al., 2014, Materials modelling for selective heating and press hardening of boron steel panels with graded microstructures, 11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014, Vol: 81, Pages: 1675-1681, ISSN: 1877-7058

JOURNAL ARTICLE

Li N, Sun C, Guo N, Mohamed M, Lin J, Takeki Met al., 2014, Damage investigation of boron steel at hot stamping conditions, 11TH INTERNATIONAL CONFERENCE ON TECHNOLOGY OF PLASTICITY, ICTP 2014, Vol: 81, Pages: 1744-1749, ISSN: 1877-7058

JOURNAL ARTICLE

Li N, Gao W, Tang X, Du H, Wang D, Ye Pet al., 2013, A Tool Design and Method for Forming Automotive Metal Panel Components, CN103182452 A

PATENT

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