Design Principles of the Non-smooth Surface of Bionic Plow Moldboard

The diverse non-smooth body surfaces to reduce soil adhesion are the evolutional results for the soil animals to fit the adhesive and wet environment and can be used as a biological basis for the design of bionic plow moldboard. The model surfaces for bionic simulation should be taken from soil animal digging organs, on which the soil motion is similar to what is on the surface of moldboard. By analyzing the distribution of non-smooth units on the body surface of the ground beetle jaw and the soil moving stresses, the design principles of the bionic moldboard for the local and the whole moldboard were presented respectively. As well, the effect of soil moving speed on reducing adhesion, the dimensions relationship between soil particles and non-smooth convexes, the relationship between the enveloping surface of non-smooth convexes and the initial smooth surface of the plow body, and the convex types of the sphere coronal and the pangolin scales,etc.were discussed.

Non-Smooth Morphologies of Typical Plant Leaf Surfaces and Their Anti-Adhesion Effects

The micromorphologies of surfaces of several typical plant leaves were investigated by scanning electron microscopy（SEM）. Different non-smooth surface characteristics were described and classified. The hydrophobicity and anti-adhesion of non-smooth leaf surfaces were quantitatively measured. Results show that the morphology of epidermal cells and the morphology and distribution density of epicuticular wax directly affect the hydrophobicity and anti-adhesion. The surface with uniformly distributed convex units shows the best anti-adhesion, and the surface with regularly arranged trellis units displays better anti-adhesion. In contrast, the surface with randomly distributed hair units performs relatively bad anti-adheslon. The hydrophobic models of papilla-ciliary and fold-setal non-smooth surfaces were set up to determine the impacts of geometric parameters on the hydrophobicity. This study may provide an insight into surface machine molding and apparent morphology design for biomimetics engineering.

Effects of Methanol on Wettability of the Non-Smooth Surface on Butterfly Wing

The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electron microscopy, The influence of the scale micro- and ultra-structure on the wettability was investigated. Results show that the contact angle of distilled water on the wing surfaces varies from 134.0° to 159.2°. High hydrophobicity is found in six species with contact angles greater than 150°. The wing surfaces of some species are not only hydrophobic but also resist the wetting by methanol solution with 55% concentration. Only two species in Parnassius can not resist the wetting because the micro-structure （spindle-like shape） and ultra-structure （pinnule-like shape） of the wing scales are remarkably different from that of other species. The concentration of methanol solution for the occurrence of spreading/wetting on the wing surfaces of different species varies from 70% to 95%. After wetting by methanol solution for 10 min, the distilled water contact angle on the wing surface increases by 0.8°-2.1°, showing the promotion of capacity against wetting by distilled water.

The Mechanism of Drag Reduction around Bodies of Revolution Using Bionic Non-Smooth Surfaces

Bionic non-smooth surfaces （BNSS） can reduce drag. Much attention has been paid to the mechanism of shear stress reduction by riblets. The mechanism of pressure force reduction by bionic non-smooth surfaces on bodies of revolution has not been well investigated. In this work CFD simulation has revealed the mechanism of drag reduction by BNSS, which may work in three ways. First, BNSS on bodies of revolution may lower the surface velocity of the medium, which prevents the sudden speed up of air on the cross section. So the bottom pressure of the model would not be disturbed sharply, resulting in less energy loss and drag reduction. Second, the magnitude of vorticity induced by the bionic model becomes smaller because, due to the sculpturing, the growth of tiny air bubbles is avoided. Thus the large moment of inertia induced by large air bubble is reduced. The reduction of the vorticity could reduce the dissipation of the eddy. So the pressure force could also be reduced. Third, the thickness of the momentum layer on the model becomes less which, according to the relationship between the drag coefficient and the momentum thickness, reduces drag.

Friction and Wear Study on Friction Pairs with a Biomimetic Non-smooth Surface of 316L Relative to CF/PEEK under a Seawater Lubricated Condition

Current studies of a seawater axial piston pump mainly solve the problems of corrosion and wear in a slipper pair by selecting materials with corrosion resistance, self-lubrication, and wear resistance. In addition, an appropriate biomimetic non-smooth surface design for the slipper pair can further improve the tribological behavior. In this paper, 316 L stainless steel and CF/PEEK were selected to process the upper and bottom specimens, and the biomimetic non-smooth surface was introduced into the interface between the friction pair. The friction and wear tests were performed on a MMD-5 A tester at a rotation speed of 1000 r/min and load of 200 N under seawater lubricated condition. The results indicate that the main friction form of the smooth surface friction pair corresponds to abrasive wear and adhesive wear and that it exhibits a friction coe cient of 0.05–0.07, a specimen temperature of 56 ℃, a high wear rate, and surface roughness. Pits on the non-smooth surface friction pairs produced hydrodynamic lubrication and reduced abrasive wear, and thus the plowing e ect is their main friction form. The non-smooth surface friction pairs exhibit a friction coe cient of 0.03–0.04, a specimen temperature of 48 ℃, a low wear rate, and surface roughness. The study has important theoretical significance for enriching the lubrication, friction, and wear theory of a seawater axial piston pump, and economic significance and military significance for promoting the marine development and the national defense military.

Influence of Non-smooth Surface on Tribological Properties of Glass Fiber-epoxy Resin Composite Sliding against Stainless Steel under Natural Seawater Lubrication

With the development of bionics, the bionic non-smooth surfaces are introduced to the field of tribology. Although non-smooth surface has been studied widely, the studies of non-smooth surface under the natural seawater lubrication are still very fewer, especially experimental research. The influences of smooth and non-smooth surface on the frictional properties of the glass fiber-epoxy resin composite（GF/EPR） coupled with stainless steel 316 L are investigated under natural seawater lubrication in this paper. The tested non-smooth surfaces include the surfaces with semi-spherical pits, the conical pits, the cone-cylinder combined pits, the cylindrical pits and through holes. The friction and wear tests are performed using a ring-on-disc test rig under 60 N load and 1000 r/min rotational speed. The tests results show that GF/EPR with bionic non-smooth surface has quite lower friction coefficient and better wear resistance than GF/EPR with smooth surface without pits. The average friction coefficient of GF/EPR with semi-spherical pits is 0.088, which shows the largest reduction is approximately 63.18% of GF/EPR with smooth surface. In addition, the wear debris on the worn surfaces of GF/EPR are observed by a confocal scanning laser microscope. It is shown that the primary wear mechanism is the abrasive wear. The research results provide some design parameters for non-smooth surface, and the experiment results can serve as a beneficial supplement to non-smooth surface study.

Computer simulation of rolling wear on bionic non-smooth convex surfaces

The study of bionics has found that the skins of many burrow animals which live in soil and stone conditions have an anti wear function, and which is related to their body surfaces’non-smooth morphology. In the present study, bionic non-smooth surfaces are used in roll surface design, and roll models with convex non-smooth surfaces are developed. The rolling wear of non-smooth roll in steel rolling is simulated by the FEM software-ANSYS. The equivalent stress, the node friction stress, and the node contact pressure between the roll and the rolling piece are calculated; and the anti-wear mechanism is analyzed.

A Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

Adhesive forces exist between soil and the surfaces of soil-engaging components; they increase working resistance and energy consumption. This paper tries to find an approach to reduce the adhesion and resistance of bulldozing plate. A simplified mechanical model of adhesion and resistance between soil and a non-smooth bulldozing plate is proposed. The interaction force between moist soil and a non-smooth bulldozing plate is analyzed. The pressure and friction distribution on the bulldozing plate are computed, and the anti-adhesive effect of a corrugated bulldozing plate is simulated numerically. Numerical results show that the wavy bulldozing plate achieves an effective drag reduction in moist soil. The optimal wavy shape of the corrugated bulldozing plate with the minimal resistance is designed. The basic principle of reducing soil adhesion of the non-smooth surface is discovered.

Numerical Modeling and Analysis of Grooved Surface Applied to Film Cooling

In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were concerned. The modeling was per- formed using Fluent software with the adoption of Shear-Stress Transport （SST） k-ωmodel as the turbulence closure. The coolant was supplied by a single film cooling hole with an inclination angle of 30°. The Mach numbers for the coolant flow and the mainstream flow were fixed at 0 and 0.6, respectively. At three blowing ratios of 0.5, 1.0 and 1.5, the aerodynamic behaviour of the mixing process as well as the heat transfer performance of the film cooling were presented. The numerical results were validated using experimental data extracted from a benchmark test. Good agreements between numerical results and the ex- perimental data were observed. For the film cooling efficiency, it shows that both local and laterally averaged cooling effectiveness can be improved by the non-smooth surface at different blowing ratios. Using the grooved surface, the turbulence intensity upon the plate can be reduced notably, and the mixing between the two flows is weakened due to the reduced turbu lence level. The results indicate that the cooling effectiveness of film cooling can be enhanced by applying the grooved surface.

Hydrophobicity mechanism of non-smooth pattern on surface of butterfly wing

Twenty-nine species (24 genera, 6 families) of butterflies typical and common in northeast China were selected to make qualitative and quantitative studies on the pattern, hydrophobicity and hydrophobicity mechanism by means of scanning electron microscopy and contact angle measuring system. The scale surface is composed of submicro-class vertical gibbosities and horizontal links. The distance of scale is 48—91 μm, length 65—150 μm, and width 35—70 μm. The distance of submicro-class vertical gib-bosities on scale is 1.06—2.74 μm, height 200—900 nm, and width 200—840 nm. The better hydropho-bicity on the surface of butterfly wing (static contact angle 136.3°—156.6°) is contributed to the co-effects of micro-class scale and submicro-class vertical gibbosities on the wing surface. The Cassie equation was revised, and new mathematical models and equations were established.

Effects of bionic non-smooth surface on reducing soil resistance to disc ploughing

Past researches have shown that the non-smooth body surfaces of soil burrowing animals help to reduce soil resistance. In this research, this concept of bionic non-smooth surface was applied to disc ploughs and an experiment was conducted in an indoor soil bin to find out the effects of different bionic units on reducing soil resistance to disc ploughing. Horizontal force acting on the disc plough during soil deformation was measured using a 5 kN sensor. Convex and concave bionic units were used and the material used for making convex ones is ultra high molecular weight polyethylene (UHMWPE) which is hydrophobic. From the experiment results, higher or deeper bionic units always resulted in less soil resistance. Convex bionic units gave the highest resistance reduction reaching a maximum of 19% reduction (from 1715.36 N to 1383.65 N) compared to concave bi-onic units. Also, samples with a bionic unit density of 30% gave the highest resistance reduction compared to the other two, which were either plain or had 10% density. In conclusion, the concept of bionic non-smooth units can be applied to disc ploughs in order to reduce soil resistance.

Experimental Study on Influence of Dimples on Lubrication Performance of Glass Fiber-epoxy Resin Composite under Natural Seawater Lubrication

Bionic non-smooth surface is widely applied in metal and ceramics materials. In order to introduce this technology to high pressure seawater pump, the influence of bionic non-smooth surface on the engineering plastics used in pump should be investigated. The comparative tests are carried out with a ring-on-disc configuration under 800, 1000, 1200 and 1400 r/min in order to research the influence of the bionic non-smooth surface on glass fiber-epoxy resin composite（GF/EPR） under natural seawater lubrication. The disc surfaces are textured with five kinds of pits, which are semi-spherical, conical, cone-cylinder combined, cylindrical pits and through holes, respectively. A smooth surface is tested as reference. The results show that the lubrication performance of dimpled GF/EPR sample is much better than that of the smooth sample under all rotational speeds. The semi-spherical pits surface has more obvious friction reduction than the others, which shows that the least reduction is approximately 43.29% of smooth surface under 1200 r/rain. However, the wear level is only marginally influenced by dimples. The surface morphology investigations disclose severe modifications caused by abrasive wear primarily. The results are helpful to vary friction properties of GF/EPR by non-smooth surface, or provide references to the design of non-smooth surfaces under certain condition.

超音速火焰喷涂Cr3C2-NiCr涂层在NaOH溶液中的腐蚀及冲蚀腐蚀磨损性能

目的分析超音速火焰喷涂制备的Cr3C2-NiCr涂层在碱性环境中的腐蚀及冲蚀腐蚀磨损性能,揭示涂层腐蚀及冲蚀腐蚀磨损失效机制。方法利用超音速火焰喷涂技术在45#钢表面制备Cr3C2-NiCr金属陶瓷涂层,采用光学显微镜、显微硬度仪、碱性环境腐蚀性能试验台、电化学分析仪、冲蚀腐蚀磨损试验机、电子天平、扫描电子显微镜,分别对组织结构、显微硬度、碱性环境下耐蚀性能、耐冲蚀腐蚀磨损性能、冲蚀腐蚀磨损损失质量及表面形貌进行测试。结果Cr3C2-NiCr涂层呈典型层状结构,内部随机分布着孔隙及氧化物,涂层孔隙率及显微硬度平均值分别为1.3%和817HV0.1。在pH=11的NaOH溶液中,涂层的电化学腐蚀电位为-0.38V,腐蚀反应生成的氧化物可有效阻止腐蚀继续进行,长期浸泡过程中,腐蚀介质通过裂纹或穿透性孔隙渗入涂层内部直至基体表面,并发生腐蚀反应,形成的腐蚀产物逐渐累积并排出至涂层表面,最终形成体积较大且呈团絮状的腐蚀产物。在碱性腐蚀环境下,腐蚀介质加剧冲蚀磨损中的材料消耗。相同条件下,涂层腐蚀冲蚀磨损损失质量明显小于基体材料,涂层的冲蚀腐蚀磨损失效机制主要有腐蚀产物脱落、硬质颗粒剥落、粘结相磨耗、缺陷处因疲劳裂纹整体脱落。结论在碱性环境中,Cr3C2-NiCr涂层具有较强的耐腐蚀性能,腐蚀介质能加快涂层冲蚀磨损进程,磨损后表面为非光滑表面,使涂层具有较优的抗冲蚀磨损性能,故Cr3C2-NiCr涂层可显著改善基体表面的综合使用性能。

同时考虑张拉-剪切破坏的边坡稳定性分析

针对目前边坡稳定性分析的强度折减法中广泛采用的Mohr-Coulomb准则仅考虑剪切破坏会过高估计边坡土体的抗拉强度,与实际工程中常见的位于坡体后缘的拉裂缝不符的问题,引入土体的张拉-剪切复合屈服准则,分别采用Mohr-Coulomb准则、Rankine准则考虑剪切、张拉作用的影响;根据张拉-剪切复合屈服准则的非光滑性,通过将非光滑屈服面的塑性本构积分简化为混合互补问题,提出用于弹塑性本构积分的投影收缩算法。结果表明:在分析边坡的稳定性时,不考虑张拉破坏会过高估计边坡的安全性并且安全系数的差值随着坡角的增大而逐渐增大,最大差值达到20%;对于含软弱夹层的分层边坡,即使边坡的坡角较小,是否考虑张拉破坏的边坡后缘的破坏特征仍存在显著区别。

基于漏斗函数双电机伺服系统跟踪与同步控制

针对双电机驱动伺服系统具有未知非线性的问题,提出一种基于漏斗函数的跟踪与同步控制方案。首先,利用神经网络逼近和补偿复杂的非线性,在此基础上,引入滤波技术解决传统反步控制的“计算爆炸”问题,同时引入非光滑漏斗误差面确保系统的状态量被约束在预定义的漏斗边界内,结合改进的漏斗函数和反步设计技术设计了一种自适应量化漏斗跟踪控制方案。为了同时保证双电机的同步运行,同步控制器采用了平均偏差耦合策略,实现了双电机伺服系统的跟踪与同步控制。仿真结果表明,该方法可以实现对负载的跟踪以及双电机的同步。

基于Fluent的非光滑表面减阻仿真实验

该文基于有限元法构建了一套可用于非光滑表面减阻仿真的实验方案。将在ICEM中划分的非光滑表面模型网格导入ANSYS中的Fluent模块进行仿真计算,通过对比分析不同速度、不同展向间距圆锥微结构的减阻率评估减阻效果,并利用可视化功能观测速度、压力和湍动能云图,探究了由圆锥微结构构成的非光滑表面减阻规律,为减阻性能方面研究提供了一种新的思路。

农业触土机具仿生减阻抗磨特性研究进展

农业触土机具的减阻抗磨性能与其自身的工作效率和使用寿命密切相关。因此,降低土壤附着力、工作阻力和磨料磨损成为当今触土农具领域迫切需要解决的热点问题。仿生学理论创建以来,借鉴土壤生物独特的几何结构面、几何结构形状和特殊功能设计仿生农业触土机具,制备仿生结构复合涂层,实现从自然生物到人造功能表面仿生减阻抗磨已获得了广泛的关注和发展。从数值模拟、土槽试验和现场试验角度来重点介绍结构仿生、非光滑表面仿生和仿生结构复合涂层3种技术在农业触土机具的性能及其减阻抗磨机理,总结国内外研究进展,介绍仿生原理、特点、制备和研究过程,例举最新的科研成果以及应用效果,针对当前和更深入探索仿生土壤动物减阻抗磨研究提供更新、更全面的参考。最后,对现有农业触土机具仿生研究存在的仿真模拟土壤参数不真实、性能检测方法不完善、减阻抗磨机理分析较少、减阻抗磨综合研究较少等问题进行阐述。为了改善上述提到的机具阻力大和黏附导致的能耗严重,以及磨损较快导致机具失效情况加剧的问题,更好地适应农业触土机械高效、低损耗发展,农业触土机具仿生技术的未来应当从性能综合测试、多种技术多功能交叉仿生、智能仿生等方面发展。同时,采用先进制备技术结合仿生材料制备新型机具,进一步优化性能。

仿生鱼鳞结构对风管气流影响数值研究

基于RSM模型,通过数值模拟的方法研究鱼鳞结构在风管中的减阻特性。对比上凸型鱼鳞排布、上凸型单个鱼鳞排布及下凹型单个鱼鳞排布在风管中的减阻率。结果表明,上凸型鱼鳞排布与上凸型单个鱼鳞排布相比平滑风管,使风管内的阻力增大。而下凹型单个鱼鳞排布能够对风管减阻起到效果。当修改下凹形单个鱼鳞排布的深度h(h=1mm,3mm,5mm),排布间距L不变时,h=5mm时,减阻效果最佳,最大减阻率为2.5%。当修改下凹形单个鱼鳞结构的排布间距L(L=2cm,2.5cm,3cm),深度h不变时,当L=3cm时,对风管的减阻能力最佳,最大减阻率为2.8%。

非现场治超动态称重考虑动态荷载研究综述

在非现场治理超限超载系统执法过程中,动态称重传感器通过测量汽车驶过承载器时的轴重来计算车辆总重。但是由于路面非绝对平整,导致车辆在不规则路面行驶而产生耦合振动,因此导致实际测量的轴重受到静载与车辆垂直振动的共同影响。通过对路面平整度预测、车辆动态荷载研究和非现场治超动态称重研究进行综述,发现在非现场治理超限超载动态称重准确度方面,要充分考虑路面平整度造成的动态荷载带来的影响。

仿生非光滑表面脱附与减阻技术在工程上的应用

生活在自然界中的生物具有生物非光滑体表 ,根据大量的观察和试验 ,发现这种非光滑表面具有减粘降阻和脱附效应 ,这种仿生非光滑表面减阻脱附技术被应用到了空中、水中和土壤中 ,得到了很好的减粘降阻与脱附效果。但是目前 ,对生物的这种非光滑体表还只是被动的模仿阶段 ,对这种现象的机理没有形成系统的认识 ,针对这种情况 ,提出今后研究工作的重点与方向是 :集中研究不同非光滑表面与不同介质之间脱附与吸附的机理和对非光滑表面的量化描述。