Browsing by Author "Chen, Guangyu"
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Item Open Access Bead shape control using multi-energy source (mes) for wire-based directed energy deposition (ded) process.(Cranfield University, 2021-11) Chen, Guangyu; Ding, Jialuo; Williams, Stewart W.Independent control of layer width and height is essential to achieve a simultaneous high build rate with precision net shape and thermal control independent from deposition shape in the wire-based directed energy deposition (w-DED) process. Bead shape control using a multi-energy source (MES) method was studied to achieve independent control of layer width height of a bead for the w-DED process. This study was carried out in three stages: First, a plasma transfer arc (PTA) energy density measurement was conducted. A split anode calorimeter (SAC) was applied for the measurement of PTA energy density. A laser beam with a well-defined energy profile was used to calibrate the calorimeter without the complications of arc instability. An optimised centred grounded SAC device was introduced to reduce arc distortion. More symmetric arc profiles were obtained. The dynamic thermal characterisation of a scanning laser (SL) was then studied using both experimental and numerical approaches. SL experiments were conducted with different oscillation frequencies and laser beam sizes. An innovative solution dependent convection boundary (SDCB) method was introduced to reduce the element amount of the finite element (FE) model. Results show that the quasi-steady state SL can be applied as an equivalent stationary energy source. Finally, an SL-PTA MES system was introduced to study the MES bead shape control, a PTA was employed in the front to create an initial melt pool and melt the feedstock wire, and an SL was used behind the PTA to reshape the melt pool and precisely control the bead width. A bead shape control strategy was proposed by using the wire feeding rate to control the layer height and the scanning width to control the layer width. The experiment results verified that the SL-PTA MES has independent control of layer width and height.Item Open Access Control of meltpool shape in laser welding(Springer, 2024-03-05) Suder, Wojciech; Chen, Xin; Rico Sierra, David; Chen, Guangyu; Wainwright, James; Rajamudili, Kuladeep; Rodrigues Pardal, Goncalo; Williams, StewartIn laser welding, the achievement of high productivity and precision is a relatively easy task; however, it is not always obvious how to achieve sound welds without defects. The localised laser energy promotes narrow meltpools with steep thermal gradients, additionally agitated by the vapour plume, which can potentially lead to many instabilities and defects. In the past years, there have been many techniques demonstrated on how to improve the quality and tolerance of laser welding, such as wobble welding or hybrid processes, but to utilise the full potential of lasers, we need to understand how to tailor the laser energy to meet the process and material requirements. Understanding and controlling the melt flow is one of the most important aspects in laser welding. In this work, the outcome of an extensive research programme focused on the understanding of meltpool dynamics and control of bead shape in laser welding is discussed. The results of instrumented experimentation, supported by computational fluid dynamic modelling, give insight into the fundamental aspects of meltpool formation, flow direction, feedstock melting and the likelihood of defect formation in the material upon laser interaction. The work contributes to a better understanding of the existing processes, as well as the development of a new range of process regimes with higher process stability, improved efficiency and higher productivity than standard laser welding. Several examples including ultra-stable keyhole welding and wobble welding and a highly efficient laser wire melting are demonstrated. In addition, the authors present a new welding process, derived from a new concept of the meltpool flow and shape control by dynamic beam shaping. The new process has proven to have many potential advantages in welding, cladding and repair applications.Item Open Access Data supporting "A novel cold wire gas metal arc (CW-GMA) process for high productivity additive manufacturing"(Cranfield University, 2023-06-30 11:53) Wang, Chong; Wang, Jun; Bento, João; Ding, Jialuo; Rodrigues Pardal, Goncalo; Chen, Guangyu; Qin, Jian; Suder, Wojciech; Williams, StewartThis is a supplementary figure, showing the experimental setup for building the large-scale component with the CW-GMA process: (a) experiment setup, and (b) monitors for thermal camera and process camera.Item Open Access Data supporting: 'Multi-Energy Source (MES) Configuration for Bead Shape Control in Wire-based Directed Energy Deposition (w-DED)'(Cranfield University, 2022-08-31 15:42) Chen, Guangyu; Suder, Wojciech; Williams, Stewart; Ding, Jialuo; Wang, ChongVideo shows the the dynamic changing of the melt pool and highspeed scanning motion of the laser beam.Item Open Access Data supporting: 'Split anode calorimetry for plasma arc energy density measurement with laser calibration'(Cranfield University, 2022-11-23 15:46) Chen, Guangyu; Williams, Stewart; Ding, Jialuo; Suder, Wojciech; Wang, YipengVideo shows the accelarated thermal image when the laser beam traveled acrossed the copper anodes interface.Item Open Access Efficient reduced-order thermal modelling of scanning laser melting for additive manufacturing(Elsevier, 2023-10-02) Chen, Guangyu; Ding, Jialuo; Sun, Yongle; Chen, Xin; Wang, Chong; Rodrigues Pardal, Goncalo; Williams, StewartAdditive manufacturing (AM) with a scanning laser (SL) to independently control melt pool shape has the potential to achieve part building with high geometric accuracy and complexity. An innovative dynamic convection boundary (DCB) method is proposed to develop a reduced-order finite element (FE) model to accelerate the thermal analysis of a SL process for AM. The DCB method approximates the thermal conduction of the adjacent material around the bead region by using a convection boundary condition that can be dynamically adjusted during the numerical solution. Thereby, a smaller problem domain and fewer elements are involved in the reduced-order FE modelling. A non-oscillating equivalent bar-shaped heat source was also introduced as a simplified substitution for a high oscillation frequency SL heat source. The DCB-based reduced-order thermal model achieved over 99% accuracy compared to the full-scale model but reduced the element amount by 73% and the computational time by 58%. The use of the bar-shaped equivalent heat source can further enhance computational efficiency without compromising the prediction accuracy of a high oscillation frequency SL process. The DCB-based reduced-order thermal modelling method and equivalent heat source could be adopted to boost extensive parametric analysis and optimisation for novel AM processes. Study on large structures AM could also be facilitated by simplifying the computation at critical regions. This study can also enable efficient thermal analyses of different manufacturing processes, such as welding, cladding, and marking.Item Open Access Efficient reduced-order thermal modelling of scanning laser melting for additive manufacturing.(Cranfield University, 2023-09-25 16:20) Chen, Guangyu; Ding, Jialuo; Sun, Yongle; Chen, Xin; Wang, Chong; Rodrigues Pardal, Goncalo; Williams, StewartThermal videos show the dynamic changing of the scanning laser melt pools with different oscillation frequenciesItem Open Access Microstructure and mechanical properties of aluminum-steel dissimilar metal welded using arc and friction stir hybrid welding(Elsevier, 2022-12-21) Liu, Ji; Wu, Bintao; Wang, Ziran; Li, Chunwang; Chen, Guangyu; Miao, YugangIn this study, arc and friction stir hybrid welding (AFSHW) was proposed to weld aluminum-steel dissimilar metals in attempt to realize high quality joining. Firstly, an interlayer was produced on galvanized steel by using bypass current-metal inert gas welding (BC-MIG), and then an aluminium plate was jointed via Friction stir lap welding (FSLW). The effects of tool pin length and FSLW times on the microstructure and mechanical properties of dissimilar joints were fully investigated by means of Optical Microscopy (OM), Scanning Electron Microscope (SEM), Electron Backscatter Diffraction (EBSD), and mechanical testing. The results show that as pin length increased, joint strength tended to increase and then decrease, and the tensile failure partially occurred at aluminium base metal. However, with additional number of FSLW, joint strength would be reduced, which was attributed to attenuated dislocation density and strain concertation in dissimilar joint. The research outcomes will provide a new welding method to obtain sound Al-Fe dissimilar metal joint, and benefit to a better understanding of Al-Fe joining mechanism.Item Open Access Mitigation of thermal distortion in wire arc additively manufactured Ti6Al4V part using active interpass cooling(Maney Publishing, 2019-02-26) Wu, Bintao; Pan, Zengxi; Chen, Guangyu; Ding, Donghong; Yuan, Lei; Cuiuri, Dominic; Li, HuijunIn this study, active interpass cooling using compressed CO2 was innovatively employed in the wire arc additively manufactured Ti6Al4V process with the aim of mitigating part distortion. A comparative analysis between simulation and experimental results was performed to explore the effects of active interpass cooling on the thermal behaviours, geometric features and distortion levels of deposit. The results show that active interpass cooling with CO2 gas is an effective means of reducing Wire arc additive manufacturing (WAAM)-part distortion by increasing heat dissipation and reducing heat accumulation within the deposition. It can contribute to a maximum reduction of 81% in longitudinal distortion and 69% in transverse distortion for the wall structures produced in this study. Compared to the cooling gas flow rate, cooling time alternation is more effective in mitigating WAAM-part distortion due to more effective heat dissipation per unit time. The findings reveal that using active interpass cooling in WAAM can offer significant cost and build-time savings, as well as providing conditions for the improvement of WAAM-part quality.Item Open Access Multi-energy source (MES) configuration for bead shape control in wire-based directed energy deposition (w-DED)(Elsevier, 2022-03-09) Chen, Guangyu; Williams, Stewart; Ding, Jialuo; Wang, Chong; Suder, WojciechA multi-energy source (MES) method featuring a high-power scanning laser (SL) was used to achieve independent control of layer width and height in a wire-based directed energy deposition (w-DED) process. In the MES system, a plasma transferred arc (PTA) was employed to create an initial melt pool and melt the wire, and a SL was used to reshape the melt pool and precisely control the bead width. The distance between the SL and the PTA and different laser scanning strategies were investigated. Images of the melt pool with varying scanning widths were captured. A bead shape control strategy was demonstrated by using the wire feed speed to control layer height and the laser scanning width to control the layer width independent of each other. The advancing speed was adjusted in proportion to the scanning width to keep the same specific process energy of the SL. The experimental results demonstrated that the MES approach provides independent control of layer width and height. Some single-pass walls were built using the MES to show that MES can be used for w-DED additive manufacturing.Item Open Access A novel cold wire gas metal arc (CW-GMA) process for high productivity additive manufacturing(Elsevier, 2023-07-01) Wang, Chong; Wang, Jun; Bento, João; Ding, Jialuo; Rodrigues Pardal, Goncalo; Chen, Guangyu; Qin, Jian; Suder, Wojciech; Williams, StewartWire-arc directed energy deposition (DED) is suitable for depositing large-scale metallic components at high deposition rates. In order to further increase productivity and efficiency by reducing overall manufacturing time, higher deposition rates are desired. However, the conventional gas metal arc (GMA) based wire-arc DED, characterised by high energy input, normally results in high remelting and reheating at relatively high deposition rates, reducing the process efficiency and deteriorating the mechanical performance. In this study, a novel wire-arc DED process with the combination of a GMA and an external cold wire, namely cold wire-gas metal arc (CW-GMA), was proposed for achieving high deposition rate and low material remelting. The maximum deposition rates at different levels of energy input were investigated, with the highest deposition rate of 14 kg/h being achieved. An industrial-scale component weighing 280 kg was built with this process at a high deposition rate of around 10 kg/h, which demonstrated the capability of the process for high productivity application. It was also found that, due to the addition of the cold wire, the remelting was reduced significantly. The working envelope and geometric process model for the CW-GMA process was developed, which can be used to avoid defects in parameter selection and predict the geometry of single-pass wall structures. Moreover, the addition of the cold wire in the CW-GMA process reduced the specific energy density, leading to a reduction in both grain size and anisotropy, which improved the mechanical properties with increased strength and reduced anisotropy.Item Open Access On the composition gradient of steel/Invar functionally graded material manufactured by wire-based direct energy deposition(Elsevier, 2024-09-25) Wang, Jun; Biswal, Romali; Chen, Guangyu; Pardal, Goncalo Rodrigues; Lu, Yao; Ding, Jialuo; Williams, StewartThis study utilized double-wire plasma arc direct energy deposition to produce functionally graded materials (FGMs) with two transition designs, abrupt (AT) and gradual (GT), from Er90s steel to Invar. The study systematically compared the transition in chemical composition, microstructure, phase evolution, thermal stress, and mechanical performance. Both FGM types exhibited a band structure in the Er90s section and coarse columnar grains in the Invar section, with the AT deposit showing a 1 mm thick, defect-free interface and the GT deposit having an 18 mm thick transition region with distinct boundaries. It revealed diverse microstructures across the transition zones, including fine ferrite, martensite with minor retained austenite (RA), coarse columnar austenite with martensite dendrites, and single FCC austenite. The GT sample uniquely featured a microstructure of martensite laths inside prior austenite decorated by RA semicontinuous network, with a crack detected due to dilatational stresses from martensite transformation. Hardness was similar in both FGM types, with higher values at the interfaces, especially in the GT FGM. The GT FGM demonstrated higher strength but lower ductility compared to the AT FGM, with failure occurring in the Invar portion for both. Thermal stress modelling indicated smoother stress transitions in the GT sample but no significant performance differences between Er90s and Invar. This study showcases the effectiveness of double-wire plasma arc DED in producing steel/Invar FGMs with varying composition gradients. It also underscores the importance of selecting the right mixing ratio for Er90s/Invar FGM deposits to avoid cracking and deterioration of properties in the gradient area.Item Open Access Refining microstructure of medium-thick AA2219 aluminium alloy welded joint by ultrasonic frequency double-pulsed arc(Elsevier, 2023-02-14) Wang, Yipeng; Li, Hong; Li, Zhuoxin; Zhang, Yu; Qin, Jian; Chen, Guangyu; Qi, Bojin; Zeng, Caiyou; Cong, BaoqiangThe increasing demand for achieving high-efficiency and high-quality medium-thick aluminium alloy welded structures, especially for large scale aerospace components, presents an urgent challenge to the conventional TIG arc welding process. This work proposed a novel double-pulsed variable polarity tungsten inert gas (DP-VPTIG) arc, in which the variable polarity square wave current was simultaneously modulated into ultrasonic frequency (20–80 kHz) and low frequency (0.5–10 Hz) pulses. Full penetration welds of 6 mm thick AA2219 aluminum alloy were successfully obtained by using this process. The microstructure and mechanical properties of the weld produced by DP-VPTIG arc were investigated, taking the conventional VPTIG arc as a comparative study. Results show that the microstructure of weld zone by DP-VPTIG arc showed an alternating distribution of fine equiaxed grain band and slightly coarse equiaxed grain band. Compared to VPTIG arc, the grain structure was effectively refined in the weld zone with DP-VPTIG arc, showing a significant reduction of average grain size by 51.2% along transverse section and 61.3% along longitudinal section. The morphology of α-Al+θ-CuAl2 eutectics transformed from continuously distributed netlike shape to separately distributed granular shape, and segregation of Cu solute element was obviously improved. The average microhardness of weld zone was increased by about 8.7% and 5.6% along transverse section and along longitudinal section. The tensile properties of ultimate tensile strength, yield strength and elongation were increased by 6.6%, 10.6% and 20.5%, respectively. The results provide a valuable basis for improving welding efficiency and joint quality through a hybrid pulsed arc.Item Open Access A simplified modelling approach for thermal behaviour analysis in hybrid plasma arc-laser additive manufacturing(Elsevier, 2022-06-25) Wang, Chong; Sun, Yongle; Chen, Guangyu; Chen, Xin; Ding, Jialuo; Suder, Wojciech; Diao, Chenglei; Williams, StewartHybrid plasma transferred arc (PTA)-laser additive manufacturing (AM) has the potential to build large-scale metal components with high deposition rate and near-net shape. However, the process is complex with many parameters adjustable for process control, which determine the thermal behaviour and thus the final structure and properties of the deposited components. In this study, a three-dimensional steady-state finite element model with two independent circular surface heat sources was developed, validated, and used to analyse the thermal behaviour in hybrid PTA-laser AM of Ti-6Al-4V. Artificial conductivity in three orthogonal directions was applied in the melt pool to compensate for the melt pool convection effect. The predicted melt pool geometry, heat-affected zone and thermal cycles had good agreement with the corresponding experimental data. This model has advantages over the widely used volumetric heat source model, since it is more representative of the energy sources used, giving accurate thermal prediction for a wide range of process parameters. As the heat source parameters in this model are directly linked to the actual arc/laser size, it enables to capture heat source size effect on the hybrid process. In addition, it is easier to calibrate compared to the model with volumetric heat sources due to the fewer empirical parameters involved. It was found that in the investigated ranges of all the parameters, the melt pool geometry is more sensitive to laser power and travel speed compared to arc-laser separation distance and laser beam size. The full-field distributions of the cooling rate and temperature gradient in the hybrid process were obtained and the roles that different process parameters played on them were also studied, which provided useful thermal information for metallurgical analysis.Item Open Access Split anode calorimetry for plasma arc energy density measurement with laser calibration(Elsevier, 2022-04-16) Chen, Guangyu; Williams, Stewart; Ding, Jialuo; Wang, Yipeng; Suder, WojciechA split anode calorimeter (SAC) has been developed for the measurement of plasma transferred arc (PTA) energy density. A novel aspect is the use of a laser beam with a well-defined energy profile which was first measured using a commercial laser beam diagnosis system and was used to calibrate the SAC. The SAC temperature data generated profile showed the same profile measured by the laser diagnosis system. This confirmed the accuracy of the SAC method and its suitability for measuring the energy distribution of an electric arc if provided stably. The PTA energy profile was observed to be distorting when crossing over the split anode interface of the SAC. This was corrected by moving the ground wire from the side to the centre of the anode. Detailed analysis of 130A PTA energy density profiles generated from both the current density and the temperature distribution of the arc showed that the current data generated profile is narrower than that of the temperature data generated profile. This indicates that the effective energy distribution is wider than that of the width of the arc column due to other energy transfer processes such as convection and radiation. The energy absorption distribution matched well to a Gaussian distribution model with a radius of 7 mm. The arc energy absorption rate of the copper plate was measured and found to be about 56%.Item Open Access Video for Fig. 4b(Cranfield University, 2022-06-17 09:57) Wang, Chong; Sun, Yongle; Chen, Guangyu; Chen, Xin; Ding, Jialuo; Suder, Wojciech; Diao, Chenglei; Williams, StewartThis is a supplementary video for Fig 4b, showing the hybrid PTA-laser melting process with a laser leading configuration.