Browsing by Author "Wang, Yipeng"
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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 Enhancing microstructural and mechanical characteristics of laser welded NiTi SMA/304 SS lap joints with medium and high entropy alloy fillers(Springer, 2024-01-03) Wang, Yipeng; Zhang, Dongni; Li, Hong; Li, Zhuoxin; Yang, Zijia; Chen, Xin; Cong, BaoqiangThe demand for high-quality nickel-titanium (NiTi) shape memory alloy (SMA) and stainless steel (SS) welded structures has led to significant challenges in fusion welding technology, which is largely influenced by filler materials. This study explores the application of CoCrNi medium entropy alloy and CoCrNiFe high entropy alloy as filler materials for laser lap welding of NiTi SMA and 304 SS. A self-fusing joint was produced for comparison. The results demonstrate that the interface zone on the NiTi side was the weakest area regarding cracking defects in NiTi/304 SS lap joints. However, using CoCrNi and CoCrNiFe fillers effectively eliminated cracking defects by considerably suppressing the formation of brittle FeTi and Fe2Ti intermetallic compounds (IMCs). The average microhardness value of the weld zone without filler was higher than with CoCrNi and CoCrNiFe. Furthermore, the addition of CoCrNi and CoCrNiFe fillers to NiTi/304 SS lap joints resulted in a substantial increase in tensile properties, with tensile strength reaching 196 ± 39 MPa without filler, 319 ± 25 MPa with CoCrNi, and 377 ± 33 MPa with CoCrNiFe, respectively.Item Open Access Influence of low-pulsed frequency on arc profile and weld formation characteristics in double-pulsed VPTIG welding of aluminium alloys(Elsevier, 2020-09-21) Wang, Yipeng; Cong, Baoqiang; Qi, Bojin; Chen, Xin; Yin, Yuhuan; Lin, SanbaoAA2219 aluminium alloy plates were processed by double pulsed variable polarity tungsten inert gas (DP-VPTIG) welding, and the influence of low-pulsed frequency on arc profile, weld appearance and penetration characteristics were investigated. An image processing algorithm was proposed for arc edge extraction and arc feature sizes acquisition. The arc energy equations in low-frequency pulse peak stage (tp) and base stage (tb) were established based on the electrical parameters. The arc profile periodically expanded in tp and shrunk in tb, resulted from the difference in arc energy of the two stages. The pulsation effects in arc profile, weld appearance and penetration, caused by the pulsed arc were observed to exhibit a decreasing trend with the increase of low-pulsed frequency (fL). The pulsation effects were obvious when fL was 0.5 Hz, then became weak and tended to disappear as fL increased above 3 Hz. The empirical correlations between fL and the pulsation effects of arc profile, weld appearance and penetration were respectively developed. It is recommended to use fL in the range of 1–2 Hz to properly exert the low-frequency pulsation effect. The results provide a valuable basis for controlling and optimizing the DP-VPTIG process in the high efficiency welding of aluminum alloysItem Open Access Optimal droplet transfer mode maintenance for wire + arc additive manufacturing (WAAM) based on deep learning(Springer, 2022-07-24) Qin, Jian; Wang, Yipeng; Ding, Jialuo; Williams, StewartIn the last decade, wire + arc additive manufacturing (WAAM), which is one of the most promising metal additive manufacturing technologies, has been attracting high interest from both academia and industry. WAAM systems are increasingly employed in the industry and academia, but there are still several challenges and barriers to process stability control. The process stability is highly dependent on how the molten feed wire is added into the melt pool, which is known as the droplet transfer mode. To ensure a stable WAAM deposition process, it is essential to maintain the transfer mode in a suitable stable status. Without an effective transfer mode control method, the operators need to determine and control the transfer mode based on their experience using manual adjustment, which is difficult to achieve in a long period of production process. In this paper, a deep learning-based technology was proposed for the control of the droplet transfer mode based on the data collected from the WAAM process. A long short term memory neural network was applied as the core transfer mode classification model. A time-series data, arc voltage, was collected and statistical and frequency features were extracted, which included 11 relevant features, as the inputs of the classification model. Then, the distance between the melted wire and the melt pool was adjusted based on the determined transfer mode to keep a suitable stability of the process. A case study was used to evaluate the proposed approach and to show its merit. The proposed approach was compared to three commonly used machine learning algorithms, k-nearest neighbours, support vector machine, and decision tree. The proposed method obtained the highest accuracy in determining the transfer mode, which was over 91%. The performance of the proposed approach was also evaluated by the single-pass and oscillated wall building. The proposed deep learning based approach improved the process stability in real-time, which resulted in better deposition qualities, in terms of geometry size and processing cleanliness compared to without control. Furthermore, this data-driven method could be applied to other WAAM processes and materials.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 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 Thermal fluid dynamics of the effect of filler wire on deposition rate and bead formation intending plasma arc-based DED(Cranfield University, 2023-10-23 09:07) Chen, Xin; Wang, Chong; Ding, Jialuo; Qu, Rongdong; Wang, Yipeng; Rodrigues Pardal, Goncalo; Williams, StewartVideos of the simulations generated by this research.Item Open Access Thermal fluid dynamics of the effect of filler wire on deposition rate and bead formation intending plasma arc-based DED(Elsevier, 2023-10-22) Chen, Xin; Wang, Chong; Ding, Jialuo; Qu, Rongdong; Wang, Yipeng; Pardal, Goncalo; Williams, StewartThe influence of filler wire configuration, such as size and geometry, on the deposition rate (DR) and bead formation, has been studied in wire arc-based directed energy deposition (WADED), but the fundamental physics underlying its effect on wire melting and melt pool dynamics remains unclear. In this paper, a series of plasma arc-based DED (plasma-DED) experiments were conducted to investigate the impact of five different filler wire configurations on DR and bead dimensions. The coupling behaviours of wire melting, metal transfer and melt pool dynamics under the five filler wire configurations were also simulated numerically using the authors' recently developed wire-feeding model. The calculated wire melting and bead cross-sections are consistent with the experimental images and measurements. The results demonstrate that the filler wire significantly affects the highest DR by altering wire melting and metal transfer behaviours through changes in arc energy absorption. The filler wire with a rhombus geometry which is closer to a Gaussian-like arc distribution than the flat wire was shown to get higher DR and more stable metal transfer. Furthermore, different filler wire configurations lead to distinct melt pool behaviours, including temperature distribution and flow velocity, due to various metal transfer behaviours and arc shading effects. This study sheds light on the fundamental physics underlying the impact of filler wire on wire melting and bead formation for the first time. The methods and findings can guide improving DR and controlling bead shape in the plasma-DED process.