Institute of Fundamental Technological Research
Polish Academy of Sciences

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Yaoqi Wang

Beijing Aeronautical Manufacturing Technology Research Institute (CN)


Recent publications
1.  Liu X., Kopeć M., Fakir O., Qu H., Wang Y., Wang L., Li Z., Characterisation of the interfacial heat transfer coefficient in hot stamping of titanium alloys, International Communications in Heat and Mass Transfer, ISSN: 0735-1933, DOI: 10.1016/j.icheatmasstransfer.2020.104535, Vol.113, pp.104535-1-14, 2020

Abstract:
The interfacial heat transfer coefficient (IHTC) for titanium alloys is an important parameter in non-isothermal hot stamping processes to determine the temperature field as well as temperature-dependent material behaviours that consequently affect the post-form properties of the formed components. However, the IHTC for titanium alloys in hot stamping processes has seldom been studied before. In the present research, the effects of contact pressure, lubricant, surface roughness, tooling material and initial blank temperature on the IHTC for the titanium alloy Ti-6Al-4V were studied and modelled to characterise the IHTC values under various hot stamping conditions as well as identify the functional mechanisms affecting the IHTC. Furthermore, the results of hot stamping of Ti-6Al4V wing stiffener components were used to verify the simulation results of the temperature field of the formed component with an error of less than 5%.

Keywords:
interfacial heat transfer coefficient (IHTC), Ti-6Al-4V, hot stamping, experimental validation

Affiliations:
Liu X. - other affiliation
Kopeć M. - IPPT PAN
Fakir O. - other affiliation
Qu H. - AVIC Manufacturing Technology Institute (CN)
Wang Y. - Beijing Aeronautical Manufacturing Technology Research Institute (CN)
Wang L. - Imperial College London (GB)
Li Z. - AVIC Manufacturing Technology Institute (CN)
2.  Wang Y., Melikhov Y., Meydan T., Yang Z., Wu D., Wu B., He C., Liu X., Stress-dependent magnetic flux leakage: finite element modelling simulations versus experiments, JOURNAL OF NONDESTRUCTIVE EVALUATION, ISSN: 0195-9298, DOI: 10.1007/s10921-019-0643-0, Vol.39, pp.1-1-9, 2020

Abstract:
Assessing the effect of defect induced stresses on magnetic flux leakage (MFL) signals is a complicated task due to nonlinear magnetomechanical coupling. To facilitate the analysis, a multi-physics finite elemental simulation model is proposed based on magnetomechanical theory. The model works by quasi-statically computing the stress distribution in the specimen, which is then inherited to solve the nonlinear magnetic problem dynamically. The converged solution allows identification and extraction of the MFL signal induced by the defect along the sensor scanning line. Experiments are conducted on an AISI 1045 steel specimen, i.e. a dog-bone shaped rod with a cylindrical square-notch defect. The experiments confirm the validity of the proposed model that predicted a linear dependency of the peak-to-peak amplitude of the normalized MFL signal on applied stress. Besides identifying the effect of stress on the induced MFL signal, the proposed model is also suitable for solving the inverse problem of sizing the defects when stress is involved.

Keywords:
magnetic flux leakage, magnetomechanics, Jiles–Atherton model, non-destructive testing, finite element method, multiphysics numerical simulation

Affiliations:
Wang Y. - Beijing Aeronautical Manufacturing Technology Research Institute (CN)
Melikhov Y. - other affiliation
Meydan T. - Cardiff University (GB)
Yang Z. - other affiliation
Wu D. - other affiliation
Wu B. - other affiliation
He C. - other affiliation
Liu X. - other affiliation
3.  Li Z., Qu H., Chen F., Wang Y., Tan Z., Kopeć M., Wang K., Zheng K., Deformation behavior and microstructural evolution during hot stamping of TA15 sheets: experimentation and modelling, Materials, ISSN: 1996-1944, DOI: 10.3390/ma12020223, Vol.12, No.2, pp.223-1-14, 2019

Abstract:
Near-α titanium alloys have extensive applications in high temperature structural components of aircrafts. To manufacture complex-shaped titanium alloy panel parts with desired microstructure and good properties, an innovative low-cost hot stamping process for titanium alloy was studied in this paper. Firstly, a series of hot tensile tests and Scanning Electron Microscope (SEM) observations were performed to investigate hot deformation characteristics and identify typical microstructural evolutions. The optimal forming temperature range is determined to be from 750 °C to 900 °C for hot stamping of TA15. In addition, a unified mechanisms-based material model for TA15 titanium alloy based on the softening mechanisms of recrystallization and damage was established, which enables to precisely predict stress-strain behaviors and potentially to be implemented into Finite Element (FE) simulations for designing the reasonable processing window of structural parts for the aerospace industry.

Keywords:
TA15, hot stamping, phase evolution, deformation, modelling

Affiliations:
Li Z. - AVIC Manufacturing Technology Institute (CN)
Qu H. - AVIC Manufacturing Technology Institute (CN)
Chen F. - AVIC Manufacturing Technology Institute (CN)
Wang Y. - Beijing Aeronautical Manufacturing Technology Research Institute (CN)
Tan Z. - Imperial College London (GB)
Kopeć M. - IPPT PAN
Wang K. - Imperial College London (GB)
Zheng K. - Imperial College London (GB)
4.  Kopeć M., Wang K., Politis D.J., Wang Y., Wang L., Lin J., 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, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.038, Vol.719, pp.72-81, 2018

Abstract:
A novel hot stamping process for Ti6Al4V alloy using cold forming tools and a hot blank was presented in this paper. The formability of the material was studied through uniaxial tensile tests at temperatures ranging from 600 to 900 °C and strain rates ranging from 0.1 to 5 s-1. An elongation ranging from 30% to 60% could be achieved at temperatures ranging from 750 to 900°C respectively. The main microstructure evolution mechanisms varied with the deformation temperature, including recovery, phase transformation and recrystallization. The hardness of the material after deformation first decreased with the temperature due to recovery, and subsequently increased mainly due to the phase transformation. During the hot stamping tests, qualified parts could be formed successfully at heating temperatures ranging from 750 to 850°C. The forming failed at lower temperatures due to the limited ductility of the material. At temperatures higher than 900°C, extensive phase transformation of α to β occurred during the heating. During the transfer and forming, the temperature dropped significantly which led to the formation of transformed β, reduction of the formability and subsequent failure. The post-form hardness distribution demonstrated the same tendency as that after uniaxial tensile tests.

Keywords:
titanium alloys, Ti6Al4V, hot stamping, microstructure

Affiliations:
Kopeć M. - IPPT PAN
Wang K. - Imperial College London (GB)
Politis D.J. - Imperial College London (GB)
Wang Y. - Beijing Aeronautical Manufacturing Technology Research Institute (CN)
Wang L. - Imperial College London (GB)
Lin J. - Imperial College London (GB)
5.  Kopeć M., Wang K., Wang Y., Wang L., Lin J., Feasibility study of a novel hot stamping process for Ti6Al4V alloy, MATEC Web of Conferences, ISSN: 2261-236X, DOI: 10.1051/matecconf/201819008001, Vol.190, pp.1-5, 2018

Abstract:
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.

Keywords:
titanium, hot stamping, metal forming

Affiliations:
Kopeć M. - IPPT PAN
Wang K. - Imperial College London (GB)
Wang Y. - Beijing Aeronautical Manufacturing Technology Research Institute (CN)
Wang L. - Imperial College London (GB)
Lin J. - Imperial College London (GB)

Conference abstracts
1.  Wang K., Kopeć M., Qu H., Wang Y., Wang L., Lin J., Li Z., A unified constitutive model for two-phase titanium alloys under hot stamping condition, ICNFT 2018, 5th International Conference on New Forming Technology, 2018-08-18/08-21, Bremen (DE), pp.1, 2018

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