ME researchers developed new alloys with ultrahigh strength and large ductility published in Nature Communications

Advanced structural materials with ultrahigh strength and excellent ductility are highly desirable for a wide variety of technological applications, including aerospace, transportation, and energy industries. However, ultrahigh-strength materials typically suffer from low tensile ductility, which severely limits their practical utility. Recently, a research team led by Dr JIAO Zengbao, assistant professor of PolyU Department of Mechanical Engineering, developed an innovative design concept for high-performance materials by engineering nanolamellar architectures, which leads to the development of new bulk nanostructured materials with an unprecedented combination of over 2 GPa yield strength and 16% uniform tensile ductility at ambient temperature. The extraordinary mechanical properties of the newly developed alloys offer tremendous potential for structural applications in aerospace, automotive, and energy industries. In addition, the fundamental concept of lamellar architecture engineering can be applied to many other metallic materials, including new-generation superalloys, titanium alloys, and advanced steels, to achieve enhanced properties for specific applications. This work has been recently published in Nature Communications [“Ultrahigh strength and ductility in newly developed materials with coherent nanolamellar architectures”, https://www.nature.com/articles/s41467-020-20109-z]. Mr FAN Lei, PolyU ME PhD student is the first author, and Dr JIAO Zengbao is one of the corresponding authors.

Benchmark advance in vehicle suspension control: Better vibration suppression & Less energy cost

PolyU research team led by Dr XJ Jing from the Laboratory of Nonlinear Dynamics, Vibration and Control, Department of Mechanical Engineering, takes further steps into critical industrial issues with benchmark advance achieved recently of increasing industrial impact. A series of benchmark results are recently developed and some of them have been accepted and published in: IEEE Transactions on Industrial Electronics (IF7.515, Rank 1/64 in Instrument and Instrumentation), which is a flagship journal in the area of industrial electronics and control: https://ieeexplore.ieee.org/abstract/document/9280376 IEEE Transactions on Cybernetics (IF11.079, Rank 1/63 in in Control and Automation), which is a flagship journal in the area of control theory and methods): https://ieeexplore.ieee.org/abstract/document/9013024   In the past several decades, suspension systems, as a critical part of vehicle chassis, which can perform significant influence on the ride comfort and vehicle manoeuvrability, obtained more and more popularity and attention in automotive industry. Compared with passive and semi-active suspension systems, an extra actuator is installed in an active suspension system to generate or dissipate energy; and thus, much better vibration isolation effect can be obtained. However, the energy cost and tough requirements on efficiency, robustness and reliability of actuation systems are becoming more and more critical issues in practical application (Figure 01). Traditional control methods usually only target at high performance without sufficient consideration on the energy cost, and thus have obvious limitation in various practical applications. To solve the problem, Dr Jing’s research team established a unique adaptive and robust control scheme for active suspension systems with neural networks, fuzzy logic and/or others. The new control scheme can intentionally employ inherent nonlinear dynamics of vehicle systems and address several critical engineering issues simultaneously, including energy efficiency, input delay/saturation, loading change, and/or unknown/uncertain dynamics etc, which are all challenging problems in engineering practices. The significant difference from most existing controllers lies in that, the designed controller can effectively utilize beneficial nonlinear stiffness and damping characteristics introduced by a novel bioinspired reference model (Figure 02), and thus purposely achieve superior vibration suppression and obvious energy-saving performance simultaneously. Theoretical analysis and experimental results vindicate that the proposed controller can effectively suppress vibration with much more improved control performance and considerably reduced control energy consumption up to or more than 44% (Figure 03, Table 01). This should be for the first time to reveal both in theory and experiments that a superior suspension performance is obtained with simultaneously an obvious control energy saving, by employing beneficial bioinspired nonlinear dynamics, compared to most traditional control methods. It also provides a unique insight into many other robust controller designs in various engineering issues. Table 01: RMS OF THE ENERGY CONSUMPTION WITH RESPECT TO DIFFERENT ROAD PROFILES (W) 　Controller 　Sinusoidal road profile 　Random road profile 　ESOT controller 　0.031 　0.0027 　Proposed controller 　0.0264(↓14.84%) 　0.0021(↓22.22%) 　Proposed tracking controller 　0.0125(↓59.68%) 　0.0015(↓44.44%)   The industrial potential will be further explored by collaborating with automobile companies from mainland of China, including the GAC Group, which is a Chinese automobile maker headquartered in Guangzhou, Guangdong, and a subsidiary of Guangzhou Automobile Industry Group. Detailed technical collaboration is under negotiation.

Nurturing Young Researchers in ME

The Department is one of the most research-active departments in the PolyU, excelling in a number of research areas of strategic importance germane to Hong Kong. We aspire to carry out high quality research of both fundamental and applied nature, nurturing researchers and striving for building up expertise in emerging areas. Around 250 research students or personnel led by 30 academic supervisors, ME researchers are dedicating themselves to a wide spectrum of research areas including Advanced Materials and Processing, Aerospace Engineering, Clean Energy and Energy Storage, Robotics and Control, Sound and Vibration, Thermofluids and Combustion. Every year, the Department organizes the Research Presentation Competition for the ME research students to share their research project insights with their peers and the PolyU community, and let their talents be known. In Nov 2020, two research students were awarded the Champions for their excellent research works and fabulous presentations in the 6th ME Research Presentation Competition. Research Stories of 2 Champions FANG Jieyichen PhD in Mechanical Engineering Supervisors: Dr JIAO Zengbao & Prof. FU Mingwang Research interest: High-temperature alloys Research work: High-entropy alloys (HEAs) are newly emerging advanced metallic materials with unique microstructure and excellent mechanical properties. In contrast to conventional alloys with one primary element and several minor alloying dopants, HEAs typically contain four or more multiple principal elements. Precipitation-hardened HEAs, especially those strengthened by coherent L12-nanoparticles, have enabled a new space for the development of advanced structural materials with superior mechanical properties at both room and high temperatures. From the application and processing points of view, there is a temperature-rise and down period which will affect the entropy contribution and solid solubility. Therefore, understanding phase stability and transformations at intermediate temperatures is crucial for tailoring microstructures and mechanical properties of L12-strengthened HEAs. In this study, the crystal structure, morphology, chemical composition of nanoscale precipitates and matrix of L12-strengthened HEAs at different temperatures were systematically investigated through scanning electron microscopy, X-ray diffraction, atom probe tomography, and thermodynamic calculations. Our results reveal that L12 precipitates can be formed at all the studied temperatures, but their morphology change as the aging temperatures decreases. In addition, the matrix structure changes from fcc-type to bcc-type upon long-term annealing at relatively low temperatures. The microstructural evolution and phase transformations of these alloys were discussed from the thermodynamic and kinetic points of view. This research not only sheds light on fundamentals of phase stability and transformations at intermediate temperatures but also provides guidance for microstructural control of L12-strengthened high-entropy alloys. SHI Xingyi PhD in Mechanical Engineering Supervisor: Dr AN Liang Research interest: Fuel cells Research work: In the last decade, the rising demand for the utilization of renewable energy has drawn more and more attention to energy conversion and storage systems. Among various energy conversion systems, direct liquid fuel cells (DLFCs) with their high energy density and facile fuel storage have received increasing attention. However, most of DLFCs must use noble metal catalysts for liquid fuel oxidation reactions, but yield limited fuel cell performance, greatly hindering their widespread application. Recently, an electrically rechargeable liquid fuel (e-fuel) system, typically consisting of an e-fuel charger for energy storage and an e-fuel cell for power generation, has attracted worldwide attention.1 Compared to the conventional alcoholic liquid fuels, this liquid e-fuel offers three major advantages including: i) good rechargeability, ii) high electrochemical reactivity even on carbon-based materials; and iii) good cost-effectiveness and durability. Here, we report a power generation system, direct liquid e-fuel cell,2 consisting of a catalyst-free graphite-felt anode and a conventional oxygen cathode separated by a proton exchange membrane, resulting in a maximum current density of 750 mA cm−2, a peak power density of 293 mW cm−2, and an energy efficiency of 42.3% at room temperature, which is much higher than the performances achieved by conventional direct liquid fuel cells, as shown in Fig. 1. This emerging technology, capable of fast recharging, could be a powerful, efficient, cost-effective, and durable power generation device, showing great potential for commercialization in the future fuel cell electric vehicle industry (Fig. 2).      

The 6th ME Research Presentation Competition 2020

The 6th PolyU Mechanical Engineering Research Presentation Competition was successfully held at the Lecture Theatre in the Jockey Club Innovation Tower, PolyU, on 19 Nov 2020. It is an annual event for research students to display their research project results and share knowledge with the PolyU community. This year, it was an unprecedented period to organize the event. Considering the social distancing measures on COVID-19, the function was confined to the competition participants and the department staff. It was not open to others. Instead of voting for the competition based on popularity, we formed a panel of judges by ME academic staff. Twenty-three research student participants each delivered a high-impact brief presentation within 3-minute. With their professional and animated presentation materials, most of the participants demonstrated good academic pitching skills. The panel of judges was impressed by the performance of the participants this year. After the oral presentations, participants interacted with the panel individually in the research posters exhibition. Displayed posters not only highlighted their research project results, but it was also an occasion for participants to convey their ideas, communicate with professionals, and let their talents be known. Congratulations to their fabulous presentations and excellent research work! Champion Student: Miss FANG Jieyichen Supervisor: Dr JIAO Zengbao Title: Stability of precipitation strengthened high-entropy alloys at intermediate temperatures Champion Student: Mr SHI Xingyi Supervisor: Dr AN Liang Title: Energizing Fuel Cells with an Electrically Rechargeable Liquid Fuel 2nd Runner-Up Student: Mr ZHAO Qingxiang Supervisor: Dr Henry CHU Title: A Soft Pipe-Climbing Robot Merit Student: Mr ARIF Muhammad Irsalan Supervisor: Dr Randolph LEUNG Title: Study of Passive Methods for Airfoil Tonal Noise Reduction using Fluid-Structure Interactions Merit Student: Mr WEN Weisong Supervisor: Prof. WEN Chih-Yung Title: 3D LiDAR Aided GNSS and Its Tightly Coupled Integration with INS Via Factor Graph Optimization Merit Student: Mr ZHOU Pengyu Supervisor: Prof. SU Zhongqing Title: An inkjet-printed, flexible, ultra-broadband nanocomposite film sensor for ultrasonics-based health monitoring More photos on PHOTO GALLERY

107th Departmental Advisory Committee Meeting

The 107th Departmental Advisory Committee (DAC) meeting was held online on 17 November 2020, under the chairmanship of Ir Dr Angus HW Cheung, Chief Executive Officer of Aerovision Technology Limited. We were grateful to have new committee members joining us. They were Mr Chan Hing Keung (Deputy General Manager – Train Services & Systems Engineering, MTR Corporation Limited), Mr Edmond Lai (Chief Digital Officer, Hong Kong Productivity Council), Dr Chengmao Xu (President of the Corporate Research Center, Midea Group) as well as one of the two student representatives, Mr Chan Yan Kit Jeffrey (full-time BEng student). It was a very fruitful meeting as members, with their wide range of expertise, had provided very valuable advices and constructive suggestions to the Department of its effort and proposals in the future developments in teaching and learning, research and consultancy, and strategic plans.

Impactful Technology Innovation for New Generation Vehicle Seats Addressing Comfort and Health Issues

The Nonlinear dynamics, Vibration, & Control (NDVC) research team in the ME department led by Dr XJ Jing has kept cutting-edge and pioneering R&D activities with industrial impact. A recent technology innovation project, addressing comfort and health issues of professional bus/truck drivers, is successfully conducted and now comes to its benchmark stage, which was secured with nearly HK$4 million funded by the Hong Kong ITF via the Automotive Platforms and Application Systems R&D Centre (ITF-APAS), with additional associated Postdoc and internship programs more than HK$2 million in early this year. The project has been implemented under a close collaboration with industrial sponsors from Hong Kong, Shenzhen and Guangzhou etc, which contribute with not only in-cash support about HK$450K but also facilities, materials and necessary equipment, under an ambitious commercialization plan, and now comes to a new stage with industrial prototypes done, top journal papers published, and patents filed or to be filed. Vehicle vibration can lead to serious occupational problems to professional bus/truck drivers, including lower back pain, muscle fatigue, spinal column disease, digestive system diseases and other cardiovascular system effects. The related occupational safety and health issues have therefore attracted many social attentions in recent years from trade unions, doctors and governmental departments (Fig01). The commonly-used practice for vibration suppression in most buses, trucks or coaches relies only on a built-in suspension system of vehicles when they were produced, and there is no any specific method for the healthcare issue. Although driver seats can be specially designed, most have no effective consideration on vibration suppression. Importantly, existing vibration isolation or suppression methods are often not working well due to a number of reasons (low performance or high cost), and this further creates a serious and challenging issue to the area of vibration control (Fig02). To solve these technical challenges and to address important social concerns, this project is to develop new generation vehicle seats, targeting effective and cost-efficient methods for improving occupational health of professional drivers (Fig03). New vehicle seats will be designed with an innovative award-winning bio-inspired nonlinear anti-vibration technology, which can achieve a special nonlinear stiffness beneficial to vibration control, and the novel anti-vibration mechanism is embedded in existing seat design which leads to no instalment and arrangement changes to existing seat structures. New vehicle seats can be adaptable to different payloads and would provide on-line alarming or assessment on historic and current sitting health. This project would provide a benchmark and unique product in this area solving the mentioned problems, and the developed anti-vibration technology in this project would also bring significant benefit to many other engineering areas for vibration isolation and suppression.

ME PhD Graduate Won Best Paper Award in 21st ILASS-Asia 2020

Dr Chengming He, a PhD graduate of PolyU Department of Mechanical Engineering, won the Best Paper Award in the 21st Annual Conference on Liquid Atomization and Spray System (ILASS-Asia 2020) held in Zhenjiang, China on 23-26 October 2020. He presented a paper “A computational study of spinning effects on bouncing and coalescence of head-on colliding droplets”. The corresponding author of the paper is his PhD supervisor, Dr Peng Zhang. ILASS-Asia, the Institute for Liquid Atomization and Spray Systems, Asia, was established in 1991 as an outgrowth of the International Conference on Liquid Atomization and Spray Systems (ICLASS). It was built for the mutual exchange of scientific and technical ideas in all field related to atomization and spray at Asia area. Dr Chengming He received his PhD degree under the supervision of Dr Peng Zhang in 2020. Currently, he is a Research Associate of State Key Laboratory of High Temperature Gas Dynamics, Institute of Mechanics, Chinese Academy of Sciences.

ME researchers awarded 2019 Highly Cited Review Paper of Applied Energy, Elsevier

The paper entitled “Recent advances in fuel cells based propulsion systems for unmanned aerial vehicles” collaborated by Prof. Chih-Yung Wen and Dr Liang An was awarded the 2019 Highly Cited Review Paper of Applied Energy, which is a peer-reviewed academic journal with an impact factor of 8.848 and a ranking of 6/143 (Top 3.8%) in “Engineering, Chemical” Subject Category in 2019 JCR Science Edition. This work provides a general description of the working principle of fuel cells and the category of unmanned aerial vehicles, introduces two types of propulsion systems that involve fuel cells, i.e., pure fuel cell system and hybrid system, describes the design methods and simulation cases, as well as summarizes the practical flight tests. Mr Zhefei Pan, a PhD student in the Department supervised by Dr An and Prof. Wen, is the first author. Read the full text at Sciencedirect The selection criterion for this award is based on the data source of Scopus, which is Elsevier’s abstract and citation database of peer-review literature, covering 50 million documents published in over 21,000 journals, book series and conference proceedings by some 5,000 publishers. The selection is limited to articles published in Applied Energy between 2018-2019. The most highly cited 30 research papers and 20 reviews published in respectively 2018 and 2019 have been selected (measured as total cites by 20th August 2020). The awards will be presented during the ICAE 2020 conference. Read more at Elsevier

ME Scholars ranked among the World’s Top 2% Scientists by Citation

The world-class research produced by ME scholars has been recognized in different global rankings.  According to an recent index compiled by Stanford University, 15 ME academics (10 of them are current ME members) of PolyU’s Department of Mechanical Engineering (ME) have been ranked among the world’s top 2% most-cited scientists in their main disciplines for career-long citation impact. Among them, Prof. Chen Guohua has been ranked among the top 20 scientists in the world in his respective fields.  The scholars were named in the “Updated science-wide author databases of standardized citation indicators” compiled by Stanford University. A research team, led by Professor John Ioannidis, created the database of more than 100,000 top scientists across the world on the basis of standardized citation indicators. They were grouped into 22 subject fields and 176 sub-fields using the indicators. The indicators included information on citations, an individual’s scientific research output, co-authorship and a composite indicator for career-long citation impact up to the end of 2019. The recognition reflects the significant influence and research excellence of the Department’s scientists, who are committed to furthering their knowledge for the benefit of the world. Congratulations to the following ME scholars who have been ranked among the top 2% of scientists in the world in their respective fields: Dr An Liang Prof. Chan Tat Leung Prof. Chen Guohua Prof. Cheng Li Prof. Cheung Chun Shun Prof. Fu Mingwang Dr Jing Xingjian Prof. Wallace Leung Prof. Shi Sanqiang Prof. Su Zhongqing Prof. Ronald So Ming Cho (Emeritus Professor) Prof. Woo Chung-Ho (Emeritus Professor) Prof.  (former staff) Prof. Zhou Limin (former staff) Prof. Zhou Yu (former staff) Data available at Elsevier Published: 8 October 2020 | Version 2 | DOI:10.17632/btchxktzyw.2 View the report

Dr An Liang received China’s Excellent Young Scientists Fund 2020

Four young researchers at The Hong Kong Polytechnic University (PolyU) have been awarded funding from China’s Excellent Young Scientists Fund 2020. Each researcher will receive RMB1.2 million to conduct pioneering research in Hong Kong over a period of three years. Dr An Liang, Associate Professor of Department of Mechanical Engineering, is one of the awardees. With his research titled “Flow and Heat/Mass Transfer in Electrochemical Energy Systems”, Dr An has systematically studied the characteristics of flow and mass transport in a complex microporous structure in which electrochemical reactions occur, and achieved a number of innovative results. The primary objective of this project is to investigate key issues related to flow and heat/mass transfer in electrochemical energy systems at different scales. Under the National Natural Science Foundation of China, China’s Excellent Young Scientists Fund has been extended to young scientists in Hong Kong and Macau for applications from eight designated universities since 2019. It aims to support young scientists (under 38 for male and under 40 for female) who have attained outstanding achievements in fundamental research to pursue innovative research in areas of their choice, fostering them to be internationally leading scholars in their respective fields. It is encouraging to see that young scientist from the Department is acclaimed by the Nation to further develop scientific research in cutting-edge technologies.