Material Engineering and Manufacturing

文章题目 页数

作者: Mi Wang, Shu Chen Yang, Guo Long Lu
摘要: Continuous Roll Forming process (CRFP) is a newly developed technique applied to form 3D surface part with various transverse and longitudinal curvatures. In CRFP, the sheet metal is non-uniformly compressed in the roll gap between the upper and lower bendable rolls. The two bendable rolls rotate in opposite directions, and the sheet metal is bitten into the roll gap continuously. At the present, the deformation characteristics of the sheet metal in the deformation zoon (sheet metal between the upper and lower bendable roll) is discussed. The friction force in CRFP can be calculated according to the Coulomb friction law.
作者: Wei Xiao Du, Li Zhan, Feng Liu, Bao Zhen Shan, W. Hwang
摘要: Super hydrophobic surface has a good application prospect in industry, agriculture and daily life. By controlling the concentration and etching time of hydrochloric acid, different rough structures were prepared on the aluminum-matrix surface, and the relationship of roughness & CA were established to explore the influence of process parameters on the surface roughness and surface wettability. It is found that the concentration and time of hydrochloric acid significantly affect the surface roughness and contact angle (CA). When the concentration of hydrochloric acid is 1.5mol/L and the etching time is 90s, the surface roughness is the best and the maximum CA is obtained. After sodium hydroxide treatment, the hierarchical structure with micro and macro scale was formed, which significantly reduced the contact area between the water droplet and the surface, and the maximum roughness and CA was achieved. The relationship between surface roughness and CA shows that the roughness can amplify the hydrophile/hydrophobicity. Therefore, a better surface of superhydrophobic surface can be obtained by increasing the surface roughness.
作者: Wen Bo Li, Jing Wang
摘要: The paper studies the effects of different microstructures on the hydrogen resistance properties. Four kinds of microstructures were obtained by using four kinds of heat treatment processes for 45 steel materials. The mechanical properties of different microstructure materials were obtained by Vickers hardness test and internal residual stress test. The relationships between hardness and depth of four kinds of microstructures were obtained by stratified microhardness test. Static hydrogen resistance property of different microstructures was obtained by using the stripping method. Results show that the H2S corrosion layer of different microstructures is basically the same, and the depth and hardness distribution of the hydrogen embrittlement layer are quite different. More pearlite, lead to the weakness of hydrogen resistance property; quenched and tempered sorbite after the hydrogen corrosion is better than ferrite + pearlite structure, martensite has a good resistance to hydrogen permeability. Finally, the relationships between microhardness and depth of the hydrogen embrittlement layer with different microstructures were fitted.
作者: Zhong Ren, Xing Yuan Huang, Zhi Hua Xiong
摘要: The effects of four difference viscoelastic constitutive parameters, i.e., viscosity, relaxation time, ε and ξ on the extrudate swell of plastic micro-tubes were studied by using the numerical method. Numerical results show that the extrudate swell of plastic micro-tube increases with the increase of the relaxation time, but decreases with the increase of ε and ξ. In addition, the extrudate swell ratio of plastic micro-tube is not changed with the increase of the viscosity of melt. To ascertain the effect of four different viscoelastic constitutive parameters on the extrudate swell of plastic micro-tube, the physical field distributions, i.e., flow velocity, shear rate, shear stress, and first normal stress difference distributions of melt were obtained, respectively. Results show that the extrudate swell phenomenon of plastic micro-tube is closely dependent on the elastic energy storage of melt induced by the above mentioned physical field distributions, especially at the outlet of die.
作者: Jun Wei Wang, Yi Chen Zhang, Lei Zhang
摘要: Ionization source based on thruster of anode layer using on the spacecraft has been investigated greatly recently. Based on the principle and structure model of the ionization source, we introduce the Particle-In-Cell Monte-Carlo-Collision (PIC-MCC) plasma simulation method into the vacuum discharge process and study on the discharge characteristics of the ionization source. The comparison results show that the discharge characteristics of anode layer ionization source such as the beam energy, beam density change with the discharge voltage, working pressure and gas type. The discharge characteristics from simulation get a good agreement with experimental results. The simulation is instructive for further research on the optimization design and characteristics research of ionization source in the material modification process.
作者: Yan Yan Yan, Yi Fan Lv, Jun Li Liu
摘要: According to the removal mechanism of ductile regime machining of nanoZrO2 ceramics and the dynamic characteristics of ultrasonic vibration assisted diamond flying cutting (UVADFC), the model of the material removal rate (MRR) of nanoZrO2 ceramics under UVADFC and diamond flying cutting (DFC) have been proposed by infinitesimal method,. In this paper, the experiment of three factors and four levels was carried out to study the relationships between MRR and the machining parameters (cutting depth , spindle speed n and feed rate c). The results of the experiment shows that UVADFC is a cost-effective method which is applied to the machining of nanoZrO2 ceramics, and the MRR of nanoZrO2 ceramics under UVADFC is 1.3-2 times greater than that of DFC, and the degree of the factors significantly influence on the MRR of nanoZrO2 ceramics are feed rate, cutting depth, spindle speed in a sequence whether it is DFC or UVADFC. The results will shed more light on the material removal mechanism of UVADFC.
作者: Gang Cao, Yan Qiu Yang, Zhi Xun Wen, Zhu Feng Yue
摘要: Based on the crystal plasticity theory, numerical simulation is implemented to calculate the equivalent strain field, resolved shear stress and sectional area of the cooling film hole. The results indicate that plastic strain and the distribution of resolved shear stress caused by multi-hole interference varies with different crystal orientations. Orientation [001] indicates relatively larger deformation than rest orientations. In the case of orientation [001], deformation concentrated at resolved shear stress zone between the holes, while orientation [011] and [111] appeared at the top and bottom of holes. Under the condition of multi-hole, compared to the single hole, the sectional area has a significant increase for orientation [001]. The sectional area changes substantially similar for orientation [011] and [111], but the sectional area is smaller than that in the case of single hole, with a sharp contrast to the formation of orientation [001].
作者: Yu Yang Wang, Jing Wang, Xiao Yang Li, Xiao Liang Gao
摘要: In order to solve the problem that the mechanical properties of containers and pipelines are difficult to evaluate during service, this paper focuses on the quantitative expression of hardness and mechanical properties. Taking the X70 pipeline steel as the research object, with 12 welds of the tensile test and 192 times the hardness of indentation test, the establishment of a mathematical application suitable for engineering applications. The results shows: The hardness, indentation parameters and mechanical properties of the weld, base metal and heat affected zone did not change significantly with the pipe wall thickness, it is reasonable to test the hardness of the outer wall of the pipeline at the scene; Vickers hardness distribution can effectively explain the fracture of the specimen, hardness and plastic work was inversely proportional.
作者: Qiu Li, Peng Gao, Wei Qiu
摘要: In this paper, tensile mechanical properties of carbon nanotube (CNT) film under lateral loading are measured. Comparing with works before, it is found that elastic modulus of CNT film under lateral stretch is higher than that under longitudinal stretch, which is an interesting experimental result. With multi-scale experimental methods including SEM and micro-Raman spectroscopy, the change of CNT bundle network of the film under lateral stretch and axial elongation of CNTs in the loading direction are measured. Based on the experimental results, the control mechanism on difference of lateral and longitudinal mechanical properties of CNT film is analyzed.