Structural Design and Optimization of the Crossbeam of a Computer Numerical Controlled Milling-Machine Tool Using Sensitivity Theory and NSGA-II Algorithm

Xueguang Li,Chongqing Li,Penghui Li,Huizhong Hu,Xiansheng Sui 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.2

The crossbeam plays a vital role in computer numerical controlled milling machines, especially in machines with a gantry structure, as it directly influences the machining precision. In this study, a machine tool crossbeam was designed, and the modal frequency of the crossbeam was analyzed using the finite element model (FEM) analysis. In the improved structure obtained through FEM analysis, the X-type structure of the internal unit of the crossbeam was replaced by an O-type structure. The specific structure dimensions were further optimized using a neural-network algorithm and a nondominated sorting genetic algorithm. Finally, we calculated the effect of each crossbeam dimension on the mass, deformation, and frequency in a sensitivity analysis. After optimizing the crossbeam dimensions with respect to deformation, modal frequency, and mass, the structural characteristics of the original and optimized crossbeams were compared. After optimization, the mass and deformation were reduced by 7.45% and 3.08%, respectively, and the modal frequency was increased by 0.42%. These results confirm that the optimization improved the performance of the crossbeam structure.

Contact modeling and stiffness of a rough surface under mixed lubrication condition

Ling Li,Litai Sun,Jingjing Wang,Benshuai He,Chongqing Fan,Lixia Li,Miaoxia Xie 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.2

A method of using a quadratic function of rotary asperities to be equivalent to asperity is established based on a measurement experiment on rough surface topography. A micro-contact model of a rough surface that includes elastic, elastic-plastic, and pure plastic deformation states is re-derived using the theory of contact mechanics and the method of probability statistics. A rough surface contact stiffness model under mixed lubrication is proposed in accordance with the rough surface contact stiffness, which consists of solid surface and lubrication medium contact stiffness. The influence of the lubrication medium, solid material, and asperity size parameters on contact stiffness is analyzed. Results show that elastic modulus, acoustic impedance, and the size parameters of the asperities of the solid part are the main factors that affect the contact stiffness of the solid part. The acoustic impedance of the lubricating medium mainly affects the contact stiffness of the lubrication part. The contact stiffness of the rough surface under mixed lubrication is a superposition of the solid and lubrication parts, and it is greater than that without the lubrication medium. The model established in this study fully considers the deformation state in practical engineering, which includes asperities and the lubrication state of rough surfaces. It provides a reference for the performance prediction of mechanical surfaces.

Effect of Vacuum Carburizing Time on Microstructure and Mechanical Properties of Tantalum Carbide Layer

Chongqing Di,Xiaodong Yan,Xuming Lv,Chao Yan,Wei Ye,Defu Li 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

A (TaC/Ta2C) carbide bilayer is obtained by vacuum carburizing technology on the surface of Ta substrate at 1673 K for 4,8, and 12 h. XRD, SEM and EBSD are utilized to investigated phase composition and the microstructure. The mechanicalproperties of the Ta and tantalum carburized materials are studied with Vicker’s hardness tester and nanoindenter, adhesionautomatic scratch tester, reciprocating friction and wear testing machine. The results show that the outside surface phasecomposition of the carbide bilayer is all the TaC phase. With the increase of the carburizing time from 4 to 12 h, the averagegrain size from approximately 500 nm to 10 μm, the thickness of the carbide bilayer is from 11 to 20 μm. The microhardnessincreases from 104.1 to 322.5 HV, and the elastic modulus are from 466.6 to 615.3 GPa. Adhesive strength is best at 8 h,49.1 N, compared to 19 N at 4 h and 36.5 N at 12 h. The friction and wear coefficient of Ta fluctuates significantly between0.6 and 1.0, after carburizing treatment, the friction and wear coefficient fluctuates smoothly, and the wear resistance is wellimproved.

Iron-loaded carbon derived from separated microplastics for heterogeneous Fenton degradation of tetracycline hydrochloride

Liu Hongwen,Li Xingyang,Li Guosheng,Yasser Vasseghian,Wang Chongqing 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.12

Microplastics are gaining growing research interest due to their significant potential threats to ecosystems and public health. Physical techniques have been proposed as a promising strategy for removing microplastics from the environment. This work innovatively proposes a process of microplastic removal by froth flotation and subsequent carbonization for synthesis of heterogeneous Fenton catalyst. The feasibility of separating different microplastics from water was verified by froth flotation, and iron-loaded carbon derived from separated microplastics was fabricated as catalyst. Carbon material was obtained by carbonization of microplastics, and iron loading was conducted to improve catalytic ability. The catalyst of iron-loaded iron was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The degradation of tetracycline hydrochloride in the heterogeneous Fenton system was evaluated by single factor experiment and kinetic analysis. The catalytic performance was mainly influenced by H2O2 concentration, solution pH, and co-existing ions. Under the conditions of catalyst 20 mg/L, H2O2 concentration 0.99 mmol/L, initial tetracycline hydrochloride concentration 20 mg/L, pH 4.0, and temperature 25 °C, the removal rate of tetracycline hydrochloride within 15 min reached 81.6%, and the rate constant was 0.138min−1. The catalytic mechanism dominated by hydroxyl radical was verified for the degradation of tetracycline hydrochloride. This work offers insights into the management of microplastics and sustainable treatment of antibiotic wastewater.

Ordinal Optimization Theory Based Planning for Clustered Wind Farms Considering the Capacity Credit

Yi Wang,Ning Zhang,Chongqing Kang,Qianyao Xu,Hui Li,Jinyu Xiao,Zhidong Wang,Rui Shi,Shuai Wang 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.5

Wind power planning aims to locate and size wind farms optimally. Traditionally, wind power planners tend to choose the wind farms with the richest wind resources to maximize the energy benefit. However, the capacity benefit of wind power should also be considered in large-scale clustered wind farm planning because the correlation among the wind farms exerts an obvious influence on the capacity benefit brought about by the combined wind power. This paper proposes a planning model considering both the energy and the capacity benefit of the wind farms. The capacity benefit is evaluated by the wind power capacity credit. The Ordinal Optimization (OO) Theory, capable of handling problems with non-analytical forms, is applied to address the model. To verify the feasibility and advantages of the model, the proposed model is compared with a widely used genetic algorithm (GA) via a modified IEEE RTS-79 system and the real world case of Ningxia, China. The results show that the diversity of the wind farm enhances the capacity credit of wind power.

Ordinal Optimization Theory Based Planning for Clustered Wind Farms Considering the Capacity Credit

Wang, Yi,Zhang, Ning,Kang, Chongqing,Xu, Qianyao,Li, Hui,Xiao, Jinyu,Wang, Zhidong,Shi, Rui,Wang, Shuai The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.5

Wind power planning aims to locate and size wind farms optimally. Traditionally, wind power planners tend to choose the wind farms with the richest wind resources to maximize the energy benefit. However, the capacity benefit of wind power should also be considered in large-scale clustered wind farm planning because the correlation among the wind farms exerts an obvious influence on the capacity benefit brought about by the combined wind power. This paper proposes a planning model considering both the energy and the capacity benefit of the wind farms. The capacity benefit is evaluated by the wind power capacity credit. The Ordinal Optimization (OO) Theory, capable of handling problems with non-analytical forms, is applied to address the model. To verify the feasibility and advantages of the model, the proposed model is compared with a widely used genetic algorithm (GA) via a modified IEEE RTS-79 system and the real world case of Ningxia, China. The results show that the diversity of the wind farm enhances the capacity credit of wind power.