Arc Envelope Grinding of Sapphire Steep Aspheric Surface with SiC-Reinforced Resin-Bonded Diamond Wheel

Jinhu Wang,Qingliang Zhao,Chunyu Zhang,Bing Guo,Julong Yuan 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4

In order to improve the grinding wheel wear during the sapphire steep aspheric surface grinding process, a SiC-reinforced resin-bonded hemispherical diamond wheel was used and the arc envelope grinding performance was investigated. Firstly, the mapping relationship between the contours of the grinding wheel and the aspheric surface was established based on the grinding conditions. The wear of the hemispherical diamond wheel was modelled, and the result indicates that the maximum wear occurred at the edge of the hemisphere, decreases along the generatrix and increases near the center. Then, the formtrued diamond wheel was used for grinding the sapphire steep aspheric surface. The concave and convex surface form error obtained at the central part of Φ 50 mm are 2.5 μm and 1.3 μm, respectively. The surface roughness R a is 230–450 nm, which is affected by the material removal rate and the sapphire crystal anisotropy. The SiC-reinforced resin-bonded diamond wheel possesses favorable self-sharpening ability and sufficient diamond grain retention capacity for sapphire grinding. The wear distribution shows that the most severe wear parts of the grinding wheel are at the edge and the center of the grinding zone, which is consistent with the model-predicted results.

Concurrent topology optimization of composite macrostructure and microstructure under uncertain dynamic loads

Jinhu Cai,Zhijie Yang,Chunjie Wang,Jianzhong Ding 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.3

Multiscale structure has attracted significant interest due to its high stiffness/strength to weight ratios and multifunctional performance. However, most of the existing concurrent topology optimization works are carried out under deterministic load conditions. Hence, this paper proposes a robust concurrent topology optimization method based on the bidirectional evolutionary structural optimization (BESO) method for the design of structures composed of periodic microstructures subjected to uncertain dynamic loads. The robust objective function is defined as the weighted sum of the mean and standard deviation of the module of dynamic structural compliance with constraints are imposed to both macro- and microscale structure volume fractions. The polynomial chaos expansion (PCE) method is used to quantify and propagate load uncertainty to evaluate the objective function. The effective properties of microstructure is evaluated by the numerical homogenization method. To release the computation burden, the decoupled sensitivity analysis method is proposed for microscale design variables. The proposed method is a non-intrusive method, and it can be conveniently extended to many topology optimization problems with other distributions. Several numerical examples are used to validate the effectiveness of the proposed robust concurrent topology optimization method.

Experimental studies on gasification of the Shenmu coal char with CO2 at elevated pressures

Wang Mingmin,Zhang Jiansheng,Zhang Shouyu,Wu Jinhu,Yue Guangxi 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6

The gasification rates of Shenmu coal chars with CO2 were experimentally studied with a pressurized thermo- gravimetric analyzer (PTGA). Shenmu coal is a typical Chinese coal, and the coal char was prepared by a fixedbed reactor in nitrogen at 900 oC. The experiments were carried out in the dynamic heating segments from 750 oC to 1,000 oC, and the reaction pressure increased from 0.1MPa to 3.1MPa with pure CO2. The external diffusion resistances were minimized by increasing the flow rates and decreasing the thickness of sample layer before the test, to ensure the reactions were under kinetic control. The results show that the gasification rates increase proportionally to the 0.1 power of the CO2 partial pressure. The unreacted-core shrinking model was applied to predict the reaction rate by changing the molar fraction of CO2 at 0.6Mpa and 1.6Mpa total pressures, which showed a good match with experimental data.

Distribution Rules of Nutrients in Orobanche Aegyptiaca-Tomato Parasitic System

Jinhu Zhi,Jinfeng Chen,Qiangqing Zheng,Shuzhen Zhao,Desheng Wang 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.3

The research put forward the concept of parasitic system for the first time and studied distribution rules of N, P and K nutrients of different soil areas and different plant tissues in the system along with changes in the tomato growth period, as well as relevance between rhizosphere soil and nutrient contents in different plant tissues. It is found in the results that when Orobanche aegyptiaca was parasitized in tomatoes and joined nutrient transmission via a certain channel, the nutrients in tomato rhizosphere soil would firstly be transported into aboveground parts and Orobanche aegyptiaca by its transfusion tissue; content changes of rapidly-available N, P and K in Orobanche aegyptiaca rhizosphere soil, tomato rhizosphere soil and non-rhizosphere soil showed certain high-low complementarity; content changing trends of N, P and K in different organs of tomatoes and Orobanche aegyptiaca had certain relations, but would differ along with variation of tomato growth period; contents of rapidly-available N and K in Orobanche aegyptiaca rhizosphere soil showed significant correlation with total contents of N and K in organs of tomato and Orobanche aegyptiaca.

Robust concurrent topology optimization of multiscale structure under load position uncertainty

Jinhu Cai,Chunjie Wang 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.4

Concurrent topology optimization of macrostructure and microstructure has attracted significant interest due to its high structural performance. However, most of the existing works are carried out under deterministic conditions, the obtained design may be vulnerable or even cause catastrophic failure when the load position exists uncertainty. Therefore, it is necessary to take load position uncertainty into consideration in structural design. This paper presents a computational method for robust concurrent topology optimization with consideration of load position uncertainty. The weighted sum of the mean and standard deviation of the structural compliance is defined as the objective function with constraints are imposed to both macro- and micro-scale structure volume fractions. The Bivariate Dimension Reduction method and Gauss-type quadrature (BDRGQ) are used to quantify and propagate load uncertainty to calculate the objective function. The effective properties of microstructure are evaluated by the numerical homogenization method. To release the computation burden, the decoupled sensitivity analysis method is proposed for microscale design variables. The bi-directional evolutionary structural optimization (BESO) method is used to obtain the black-and-white designs. Several 2D and 3D examples are presented to validate the effectiveness of the proposed robust concurrent topology optimization method.

Effects of Salt Water Drip Irrigation on Jujube Roots Soil Available Nitrogen Distribution : A Security Assurance Perspective

Xingpeng Wang,Tiecheng Bai,Jinhu Zhi,Zhaoyang Li 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.2

Field experiment was used in this research to study influences brought by salt water with different degrees of mineralization to distribution characteristics of soil available nitrogen and nitrate nitrogen in red jujube root zones when the salt water drip irrigation was carried out to jujubes. It is shown in the results that the distribution content of soil available nitrogen in jujube tree root zones tended to gradually decrease from top to bottom in the soil profile at different growth stages. The soil available nitrogen contents at different growth stages exceeded initial values. The mineralization degrees of salt water which influenced the available nitrogen were successively 3 g/L>4 g/L>2 g/L>CK, wherein the salt water with mineralization degree of 3g/L brought largest influences to transformation and utilization of available nitrogen in jujube tree root zones; with regard to different growth stages, the available nitrogen content was high in the soil layer with depth of 0-20 cm in the jujube root zone, and the content was small in the soil layer with depth o 30-50 cm; during drip irrigation with the mineralization degree of over 3g/L, the nitrate nitrogen content in soil layers of the jujube tree root zone exceeded the content under fresh water irrigation treatment as a whole.

Aerodynamic design and optimization of a multi-stage axial flow turbine using a one-dimensional method

Xinyang Yin,Hanqiong Wang,Jinguang Yang,Yan Liu,Yang Zhao,Jinhu Yang Techno-Press 2023 Advances in aircraft and spacecraft science Vol.10 No.3

In order to improve aerodynamic performance of multi-stage axial flow turbines used in aircraft engines, a one-dimensional aerodynamic design and optimization framework is constructed. In the method, flow path is generated by solving mass continuation and energy conservation with loss computed by the Craig & Cox model; Also real gas properties has been taken into consideration. To obtain an optimal result, a multi-objective genetic algorithm is used to optimize the efficiencies and determine values of various design variables; Final design can be selected from obtained Pareto optimal solution sets. A three-stage axial turbine is used to verify the effectiveness of the developed optimization framework, and designs are checked by three-dimensional CFD simulation. Results show that the aerodynamic performance of the optimized turbine has been significantly improved at design point, with the total-to-total efficiency increased by 1.17% and the total-to-static efficiency increased by 1.48%. As for the off-design performance, the optimized one is improved at all working points except those at small mass flow.

Effect of surface quality on hydrogen/helium irradiation behavior in tungsten

Hongyu Chen,Qiu Xu,Jiahuan Wang,Peng Li,Julong Yuan,Binghai Lyu,Jinhu Wang,Kazutoshi Tokunaga,Gang Yao,Laima Luo,Yucheng Wu 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6

As the plasma facing material in the nuclear fusion reactor, tungsten has to bear the irradiation impact ofhigh energy particles. The surface quality of tungsten may affect its irradiation resistance, and even affectthe service life of fusion reactor. In this paper, tungsten samples with different surface quality werepolished by mechanical processing, subsequently conducted by D2þ implantation and thermal desorption. D2þ implantation was performed at room temperature (RT) with the irradiation dose of 1 1021D2þ/m2 by 5 keV D2þ ions, and thermal desorption spectroscopy measurements were done from RT to900 K. In addition, He irradiation was also performed by 50 eV Heþ ions energy with the fluxes of5.5 1021 m2s1 and 1.5 1022 m2s1, respectively. Results reveal that the hydrogen/helium irradiation behavior are both related to surface quality. Samples with high surface quality has superior D2þretention behavior with less D2 retained after implantation. However, such samples are more likely togenerate fuzzes on the surface after helium irradiation. Different morphologies (smooth, wavy, pyramids)after helium irradiati