砂轮约束磨粒喷射精密光整加工有效性实验验证

通过实验验证了砂轮约束磨粒喷射精密光整加工方法的有效性,利用M7120平面磨床对Q235A进行了喷射加工实验,用TALYSURF5轮廓仪测量了加工后的微观几何参数值,用扫描电镜和金相显微镜观察了表面微观形貌和断面金相组织变化。实验结果表明,该加工方法在表面粗糙度得到减小的同时,能明显去除磨削加工过度塑性变形,减少表面层污染和磨削烧伤,改善表面形状精度,实验结果和理论分析吻合,验证了该工艺方法的正确性。     

生物结皮生长发育对黄绵土抗侵蚀性能的影响

[目的] 黄土高原退耕还林(草)工程驱动的生物结皮发育可显著抑制土壤侵蚀,为探明土壤抗侵蚀性能随生物结皮生长发育的变化特征及其响应机制。[方法] 设置藻结皮、藓结皮和自然演替结皮3个处理,培育176天,系统研究生物结皮不同发育阶段及其类型差异对黄绵土抗侵蚀性能的影响。[结果] (1)生物结皮盖度、厚度、生物量、叶绿素和粗糙度随生长时间均显著增加,培育初期藓结皮较高,培育末期自然演替结皮反而最高。(2)随生物结皮发育,土壤黏结力呈幂函数增强,较初期增加39.8%~60.3%;质量损失率呈指数函数减小,较初期降低45.6%~57.3%;饱和导水率变化趋势较为复杂,但培育末期均最低(0.08~0.12 mm/min)。(3)土壤黏结力随生物结皮盖度、厚度、叶绿素、生物量和表面粗糙度的增加呈幂函数增长,质量损失率随生物结皮盖度、厚度、叶绿素、生物量和表面粗糙度的增加呈指数函数下降。(4)土壤抗侵蚀综合指数(C_ser)可表示为盖度(Cov)、厚度(T)和生物量(B)的幂函数(C_ser=0.279 Cov^0.194 T^0.188 B^0.119, R²=0.73, p＜0.05)。[结论] 黄土高原生物结皮发育可显著提高黄绵土抗侵蚀性能,藓结皮效果最强。     

壁面粗糙度对轴流泵水力性能影响的研究

采用全三维雷诺时均Navier-Stokes方程和标准κ-ε湍流模型,数值模拟了包括叶轮、导叶、泵壳和轮毂等过流部件壁面粗糙度对轴流泵水力性能的影响。计算结果表明,壁面粗糙度对轴流泵的水力特性影响显著。通过机械抛光或表面处理等方法,降低过流表面的粗糙度,可有效地提高轴流泵的扬程和效率。水泵的效率对叶片表面的粗糙度更加敏感,应给予更多的关注。研究还发现,水泵出口断面轴向流速分布均匀度和速度加权平均偏流角也随壁面粗糙度改变而改变。     

坡耕地地表糙度的量测与计算

在回顾了地表糙度的测量和计算方法后,经实验证实,Brough D L,Linden D R和Van Doren D M等人提出的糙度测量和计算方法,均能满足黄土高原坡耕地人为耕作管理形成的微地形特征的研究需求。     

植被景观指数随复合地形因子分异的变化规律

为了探讨地表粗糙长度和地形起伏度空间分异对武夷山自然遗产地植被景观格局性质的影响,利用ArcGIS 9.0和景观指数软件分析各地表粗糙长度和起伏度带上的景观指数。结果表明：景观的面积、斑块数量、景观多样性指标、优势度指标随着地表粗糙长度指数的增加,而呈现“增加-减少-增加”的趋势,在粗糙长度为7的级别上达到最大值;破碎度指数、景观面积周长比分维数值随粗糙长度的增加,呈现先减少后增加的“U”型曲线;景观面积指标、景观斑块数量、景观破碎度、景观多样性指标、景观优势度随着起伏度的增加而呈递减趋势,只有景观斑块的面积周长比的分维数在800 m     

Experimental analysis of the abrasive belt follow-up grinding of Zirconium-4 alloys tubes and pipes

Abrasive belt grinding experiments of Zr-4 nuclear power tube are carried out by using three different abrasive belts with same size, and the interactive generating mechanism between abrasive and workpiece is analyzed, the main factors of material removal rate and surface roughness of Zr-4 alloys are obtained. With the help of the advanced test facilities, the abrasive grain abrasion and surface topography of the workpiece are observed. The metallographic structure and microhardness of the layer of burnt surface during Zr-4 alloys Grinding are analyzed. Some conclusions are given as follows: the material removal rate and surface roughness are mainly affected by the factors of belt speed, grinding pressure, hardness of the contact wheel and abrasive type, of which, the belt speed is the strongest factor. The adhesion wear of the Zirconium corundum and aluminium oxide abrasive grit is more serious, the most important wear form of silicon carbide is abrasion wear. With the onset of grinding burn, the mechanical properties of Zr-4 alloys are deteriorated obviously. The results provide a theoretical and experimental basis for technical optimization in the grinding of Zr-4 alloys with efficiency and high quality.     

Airfoil design using improved particle swarm optimization

Based on the theory of standard particle swarm optimization (PSO), an improved particle swarm optimization algorithm is presented, and it has a better optimized performance than standard PSO. A multi-objective wind turbine airfoil shape optimization model is established and 4 kinds of different thick wind turbine airfoils with better performance are designed by using the improved PSO algorithm. The aerodynamic performance of the CQU-A18 and CQU-A21 airfoils are analyzed in detail compared with the commonly used wind turbine airfoil with the same thickness. The results show that the new airfoils show very good aerodynamic characteristics, and they are found to be very insensitive to leading edge roughness. The new airfoils exhibit the higher lift coefficient and larger lift/drag ratio in both smooth condition and rough condition at the main angle of attacks. The performances of the new airfoils show a significant improvement compared with the typical airfoils.     

The impact of road geometry and surface roughness on fuel consumption of logging trucks

Fuel accounts for more than 35% of transport costs in Swedish forestry, and reduced fuel consumption would provide immediate economic and environmental benefits. The objective of this study was to quantify the effect of road gradient, curvature and surface roughness on fuel consumption of a conventional 60-ton logging truck. The study used a 320-km test track on both public and forest roads. The track was driven with various load weights in both dry summer and wet autumn conditions. Fuel consumption data were retrieved from the truck's CAN-bus system, and road data were measured with a profilograph. Average fuel consumption was 71.4?litres/100?km. A regression analysis showed that the most important factor was the interaction between vehicle weight and gradient, explaining the 86% increase between empty and fully loaded truck. In addition, the regression analysis quantified the individual effects of undulation, curvature and surface roughness, explaining the 107% increase in fuel consumption between the highest and lowest road class. Results from the proposed regression model (R² of 84% for a road section length of 1000?m) were consistent with predictions given by the European ARTEMIS model, and the proposed model can be used to improve cost estimation and route selection.     

3D-MOTIF Method and Its Application to Microscale Topography

The 2D motif method is a surface characterization method promising to separate roughness and waviness from a profile and is adopted by ISO,so is meaningful to extend this method to 3D.Vincent's watershed algorithm is employed for the generation of 3D-motif.A smallest area selecting criteria is proposed for the use of clearing the small motifs which are concerned as noise.As there are no manipulating factors as 2D-method,a multi-scale analysis is employed based on area and depth criteria,the use of depth criteria is to prevent the combination of two adjacent motifs if there is a significant peak on the border of them.Finally the surface of C(100) are analyzed by the presented method,the texture of this surface has been characterized.     

Nanometer Scale Surface Roughness Measurement Based on AFM

The datum line and mainly three profile height parameters of surface roughness are briefly introduced and the operation principle and system structure of AFM. IPC - 208B with high-resolution, which was successfully developed by Chongqing University, are described in detail, and the emphasis is laid on its application on the nanometer scale surface roughness. Taking stainless steel for example, its micro-structure was observed, and the surface data were analyzed and transacted by special evaluator and the values of three profile height parameters were obtained. Finally the experimental results are briefly analyzed.