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| 1 | Micro/nano-structured TiO2 surface with dual-functional antibacterial effects for biomedical applications显示文摘Implant-associated infections are generally difficult to cure owing to the bacterial antibiotic resistance which is attributed to the widespread usage of antibiotics.Given the global threat and increasing influence of antibiotic resistance,there is an urgent demand to explore novel antibacterial strategies other than using antibiotics.Recently,using a certain surface topography to provide a more persistent antibacterial solution attracts more and more attention.However,the clinical application of biomimetic nano-pillar array is not satisfactory,mainly because its antibacterial ability against Gram-positive strain is not good enough.Thus,the pillar array should be equipped with other antibacterial agents to fulfill the bacteriostatic and bactericidal requirements of clinical application.Here,we designed a novel model substrate which was a combination of periodic micro/nano-pillar array and TiO2 for basically understanding the topographical bacteriostatic effects of periodic micro/nano-pillar array and the photocatalytic bactericidal activity of TiO2.Such innovation may potentially exert the synergistic effects by integrating the persistent topographical antibacterial activity and the non-invasive X-ray induced photocatalytic antibacterial property of TiO2 to combat against antibiotic-resistant implant-associated infections.First,to separately verify the topographical antibacterial activity of TiO2 periodic micro/nano-pillar array,we systematically investigated its effects on bacterial adhesion,growth,proliferation,and viability in the dark without involving the photocatalysis of TiO2.The pillar array with sub-micron motif size can significantly inhibit the adhesion,growth,and proliferation of Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli).Such antibacterial ability is mainly attributed to a spatial confinement size-effect and limited contact area availability generated by the special topography of pillar array.Moreover,the pillar array is not lethal to S.aureus and E.coli in 24 h.Then,the X-ray induced photocatalytic antibacterial property of TiO2 periodic micro/nano-pillar array in vitro and in vivo will be systematically studied in a future work.This study could shed light on the direction of surface topography design for future medical implants to combat against antibiotic-resistant implant-associated infections without using antibiotics. | Xiang Ge Chengzu Ren Yonghui Ding Guang Chen Xiong Lu Kefeng Wang Fuzeng Ren Meng Yang Zhuochen Wang Junlan Li Xinxin An Bao Qian Yang Leng | 2019 | Bioactive Materials2019，4，1： | 8 |
| 2 | Effect of cooling strategies on performance and mechanism of helical milling of CFRP/Ti-6Al-4V stacks显示文摘Hole-making for Carbon Fiber Reinforced Plastics(CFRP)/Ti-6Al-4V stacks is crucial for the assembling strength of aircraft structure parts.This work carried out experimental work for helical milling(HM)of the stacks with sustainable cooling/lubrication(dry,MQL and cryogenic)conditions.Cutting forces and temperatures at the CFRP layer,Ti-6Al-4V layer and the interface of stacks were obtained by a developed measuring system.The temperatures in CFRP machining at cryogenic condition varied from-167℃to-94℃,which were much lower than those at dry and MQL conditions.The maximum temperature near the interface of stacks for the ninth hole was higher than 240℃due to heat conduction from Ti-6Al-4V layer.The hole quality,hole diameter and tool wear mechanism at different cooling/lubrication conditions were presented and discussed.MQL condition generated mainly extrusion fracture for the fibers,due to the reduced friction effect compared with dry condition.MQL was helpful to reduce the feed mark at the hole surface of Ti-6Al-4V alloy.The flank wear of cutting edge at MQL condition was better than those at dry and cryogenic conditions.Cryogenic cooling contributed to better CFRP surface with smaller delamination and hole entrance damage due to the increased resin strength and fiber brittleness.The damage near the entrance of CFRP were analyzed by the contact state of cutting edges and fibers.Additionally,hole diameters near the exit of CFPR layer were larger than other test positions.This work provided feasible processes for improving hole quality and tool life in hole-making of CFRP/Ti-6Al-4V stacks. | Jiaying GE Guang CHEN Yongxiang SU Yunhe ZOU Chengzu REN Xuda QIN Guofeng WANG | 2022 | Chinese Journal of Aeronautics2022，35，2： | 4 |
| 3 | Constitutive Modeling for Ti-6Al-4V Alloy Machining Based on the SHPB Tests and Simulation显示文摘A constitutive model is critical for the prediction accuracy of a metal cutting simulation. The highest strain rate involved in the cutting process can be in the range of 10~4–10~6 s^(–1). Flow stresses at high strain rates are close to that of cutting are difficult to test via experiments. Split Hopkinson compression bar(SHPB) technology is used to study the deformation behavior of Ti-6Al-4V alloy at strain rates of 10^(–4)–10~4s^(–1). The Johnson Cook(JC) model was applied to characterize the flow stresses of the SHPB tests at various conditions. The parameters of the JC model are optimized by using a genetic algorithm technology. The JC plastic model and the energy density-based ductile failure criteria are adopted in the proposed SHPB finite element simulation model. The simulated flow stresses and the failure characteristics, such as the cracks along the adiabatic shear bands agree well with the experimental results. Afterwards, the SHPB simulation is used to simulate higher strain rate(approximately 3×10~4 s^(–1)) conditions by minimizing the size of the specimen. The JC model parameters covering higher strain rate conditions which are close to the deformation condition in cutting were calculated based on the flow stresses obtained by using the SHPB tests(10^(–4)–10~4 s^(–1)) and simulation(up to 3×10~4 s^(–1)). The cutting simulation using the constitutive parameters is validated by the measured forces and chip morphology. The constitutive model and parameters for high strain rate conditions that are identical to those of cutting were obtained based on the SHPB tests and simulation. | CHEN Guang KE Zhihong REN Chengzu LI Jun | 2016 | Chinese Journal of Mechanical Engineering2016，29，5： | 3 |
| 4 | Prediction of cutting forces in helical milling process显示文摘 | Haiyan Wang Xuda Qin Chengzu Ren Qi Wang | 2012 | The International Journal of Advanced Manufacturing Technology2012，，9： | 2 |
| 5 | Application of genetic algorithms for optimizing the Johnson:Cook constitutive model parameters when simulating the titanium alloy Ti-6A1-4V machining process显示文摘 | CHEN Guang REN Chengzu YU Wei | 2012 | Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture2012，226，8： | 1 |
| 6 | Finite element simulation of high-speed machining of titanium alloy(Ti-6Al-4V) based on ductile failure model显示文摘 | Chen Guang Ren Chengzu Yang Xiaoyong | 2011 | The International Journal of Advanced Manufacturing Technology2011，225，6： | 1 |
| 7 | Measurement and finite element simulation of micro-cutting temperatures of tool tip and workpiece显示文摘 | CHEN Guang REN Chengzu ZHANG Pan | 2013 | International Journal of Machine Tools and Manufacture2013，75，： | 1 |
| 8 | An accurate method for calculating the contact subsurface stress field of hybrid ceramic ball bearing显示文摘 | WANG Cheng YU Wei REN Chengzu | 2011 | Application of Diamond and Related Materials2011，175，： | 1 |
| 9 | Finite ele- ment simulation of high-speed machining of titanium alloy (Ti6A14V) based on ductile failure model 显示文摘 | Guang Chen Chengzu Ren Xiaoyong Yang | 2011 | Int J Adv Manuf Technol2011，56，： | 1 |
| 10 | Experimental Study of ELID Grinding Based on the Active Con- trol of Oxide Layer显示文摘 | Yang Lijian Ren Chengzu Jin Xinmin | 2010 | Journal of Materials Pro eessing Teehnology2010，210，： | 1 |
| 11 | A Design of the New Typed Shape Modification Processing Model for Ce- ramic Ball Blank显示文摘 | Ren Chengzu Wang Chunjie | 2012 | Journal of Machine Design2012，19，4： | 1 |
| 12 | Precision internal grinding of bearing steel based on the state control of oxide layer with electrolytic in-process dressing显示文摘 | Zhang Kaifei Ren Chengzu Yang Lijian | 2012 | Journal of Material ProcessingTechnology2012，212，7： | 1 |
| 13 | Measurement and Finite Element simulation of micro - cutting temperatures of tool tip and work- piece显示文摘 | Chen Guang Ren Chengzu Zhang Pan | 2013 | International Journal of Machine Tools & Manufacture2013，，75： | 1 |
| 14 | Pre- diction of Cutting Forces in Helical Milling Process 显示文摘 | Wang Haiyan Qin Xuda Ren Chengzu | 2012 | International Journal of Advanced Manufactur- ing Technology2012，58，： | 1 |
| 15 | Precision internal grinding of bearing steel based on the state control of oxide layer with electrolytic in-process dressing显示文摘 | Zhang Kaifei Ren Chengzu Yang Lijian | 2012 | Journal of Material Processing Technology2012，212，7： | 1 |
| 16 | Finite element simulation of high speed machining of titanium alloy (Ti-6A1-4V) based on ductile failure model显示文摘 | CHEN Guang REN Chengzu YANG Xiaoyong | 2011 | International Journal of Advanced Manufacturing Technology2011，56，9： | 1 |
| 17 | Temperature dependent work hardening in Ti-6A1-4V alloy over large temperature and strain rate ranges: Experiments and constitutive modeling显示文摘 | CHEN Guang REN Chengzu Q1N Xuda | 2015 | Materials & Design2015，83，： | 1 |
| 18 | ECCENTRIC CIRCULAR GROOVE LAPPING TECHNIQUE FOR CERAMIC BALLS显示文摘ECCENTRICCIRCULARGROOVELAP-PINGTECHNIQUEFORCERAMICBALLSECCENTRICCIRCULARGROOVELAP-PINGTECHNIQUEFORCERAMICBALLSRenChengzu,XuYa... | Ren Chengzu,Xu Yanshan, Lin Bin, Guo Hongqi , Peng Zemin (Tianjin University) | 1996 | Chinese Journal of Mechanical Engineering1996，9，1： | 0 |
| 19 | A theoretical and deep learning hybrid model for predicting surface roughness of diamond-turned polycrystalline materials显示文摘Polycrystalline materials are extensively employed in industry.Its surface roughness significantly affects the working performance.Material defects,particularly grain boundaries,have a great impact on the achieved surface roughness of polycrystalline materials.However,it is difficult to establish a purely theoretical model for surface roughness with consideration of the grain boundary effect using conventional analytical methods.In this work,a theoretical and deep learning hybrid model for predicting the surface roughness of diamond-turned polycrystalline materials is proposed.The kinematic–dynamic roughness component in relation to the tool profile duplication effect,work material plastic side flow,relative vibration between the diamond tool and workpiece,etc,is theoretically calculated.The material-defect roughness component is modeled with a cascade forward neural network.In the neural network,the ratio of maximum undeformed chip thickness to cutting edge radius RT S,work material properties(misorientation angle θ_(g) and grain size d_(g)),and spindle rotation speed n s are configured as input variables.The material-defect roughness component is set as the output variable.To validate the developed model,polycrystalline copper with a gradient distribution of grains prepared by friction stir processing is machined with various processing parameters and different diamond tools.Compared with the previously developed model,obvious improvement in the prediction accuracy is observed with this hybrid prediction model.Based on this model,the influences of different factors on the surface roughness of polycrystalline materials are discussed.The influencing mechanism of the misorientation angle and grain size is quantitatively analyzed.Two fracture modes,including transcrystalline and intercrystalline fractures at different RTS values,are observed.Meanwhile,optimal processing parameters are obtained with a simulated annealing algorithm.Cutting experiments are performed with the optimal parameters,and a flat surface finish with Sa 1.314 nm is finally achieved.The developed model and corresponding new findings in this work are beneficial for accurately predicting the surface roughness of polycrystalline materials and understanding the impacting mechanism of material defects in diamond turning. | Chunlei He Jiwang Yan Shuqi Wang Shuo Zhang Guang Chen Chengzu Ren | 2023 | International Journal of Extreme Manufacturing2023，5，3： | 0 |
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