基于二维双正交小波变换的贝壳表面形貌评定

研究表明海洋贝壳表面形貌与防污性能存在一定的关系。为评定贝壳表面形貌,探讨贝壳表面形貌与其防污性能关系,采用接触式表面轮廓测量仪对贝壳的表面形貌进行测量;运用二维双正交小波变换消除贝壳表面形貌测量数据中的形状误差,计算常用的表面特征参数。结果表明:运用二维双正交小波变换将贝壳表面形貌测量数据中的形状误差消除后,可得到更加合理的表面特征参数评定结果,可用于贝壳表面形貌的评定。     

燃机曲折型迷宫密封的泄漏特性研究

以F级燃气轮机中曲折型迷宫密封为研究对象,对其内部流场和泄漏特性进行数值模拟,研究密封间隙、压比对迷宫密封泄漏特性的影响。结果表明：在相同密封间隙下,泄漏量随着压比的提高而增加;相同压比下,泄漏量随着密封间隙的减小而减少。基于数值计算结果,对现有迷宫密封泄漏量计算公式进行修正,建立曲折型迷宫密封的泄漏量计算公式。该公式计算结果与CFD数值模拟结果吻合很好,和同类公式相比,能够更为精确地计算该类型密封结构的泄漏量。     

燃气机曲折型迷宫密封的泄漏特性

以F级燃气轮机中曲折型迷宫密封为研究对象,对其内部流场和泄漏特性进行数值模拟,研究密封间隙、压比对迷宫密封泄漏特性的影响。结果表明:在相同密封间隙下,泄漏量随着压比的提高而增加;相同压比下,泄漏量随着密封间隙的减小而减少。基于数值计算结果,对现有迷宫密封泄漏量计算公式进行修正,建立曲折型迷宫密封的泄漏量计算公式。该公式计算结果与CFD数值模拟结果吻合很好,和同类公式相比,能够更为精确地计算该类型密封结构的泄漏量。     

基于有限元的三维随机形貌结合面接触分析

机加工结合面表面形貌是三维的、随机的,传统的基于微凸体的接触模型由于进行了大量假设,其结论只能在较为苛刻的条件下成立。据结合面三维形貌测量得到的数据,重构出不同材料、加工方式的表面,采用有限元法建立了随机表面的接触模型,通过接触分析来获得了下结合面法向变形量随外载荷的变化规律,并推导出单位面积上结合面法向刚度系数的表达式。结果表明,结合面法向变形量与法向载荷基本符合幂指数函数关系;表面加工方式的不同对于结合面接触性能的影响较大,磨削表面的法向变形量明显小于铣削表面;除铸铁铣削表面外,其他结合面的法向刚度系数趋于稳定,彼此之间相差不大。     

铣削钛合金加工表面形貌特征参数的预测

钛合金在铣削过程中受迫振动明显,刀—工接触关系不断变化,加工表面形貌特征参数难以预测,已成为制约加工表面质量进一步提高的瓶颈。针对铣削振动与加工表面形貌的非线性随机变化特性进行了切削钛合金试验,采用高斯过程回归法构建铣削振动作用下的加工表面形貌高斯过程模型。分析刀齿误差和铣削振动对加工表面形貌特征参数的影响规律,为以加工表面质量分布一致性为前提的铣削钛合金工艺设计提供参考依据。     

斜盘式轴向柱塞泵泄漏量的分析与计算

通过对斜盘式轴向柱塞泵泄漏途径的分析研究,得到了奇偶数泵的泄漏量计算公式,并对泵在不同参数下的泄漏量进行了仿真分析,为进一步研究泄漏量对奇偶数斜盘式轴向柱塞泵实际流量及脉动系数的影响提供了较好的理论依据。     

机械结合面微观接触模型及接触特性研究

通过原子力显微镜(AFM)实测得到机械结合面的真实三维微观表面形貌,同时基于分形理论模拟仿真得到了机械结合面三维微观表面形貌,分析结果表明,分形模拟表面形貌能较好地模拟机械结合面的真实微观表面形貌。进一步分别以实测的结合面表面形貌和基于分形理论模拟的表面微观形貌建立结合面的三维表面微观接触模型,运用有限元法进行接触仿真分析,研究真实微观表面之间的微观弹性及弹塑性接触特性,通过仿真分析得到Z向位移、接触面积和接触压力与接触载荷间的关系曲线。结果表明,基于分形理论建立的机械结合面分形模拟微观接触模型可以替代实测真实微观接触模型进行仿真分析。本研究能为深入开展结合面微观作用机理的研究提供理论依据。     

复杂曲面表面形貌的评定及其应力集中分析

为合理评定圆棒试样缺口底部复杂曲面的表面加工质量,提出小波变换并结合摄动法对其进行定量分析的方法。对测量的原始表面形貌进行小波变换提取出表面粗糙度信息,并进行表面粗糙度参数分析。采用摄动法对提取出的表面粗糙度信息进行应力集中分析,提出计算复杂曲面表面应力集中系数和表面相对应力梯度的方法。使用NPFLEX白光干涉仪测量平板试样和圆棒试样缺口底部复杂曲面的表面形貌。针对平板试样的表面形貌,使用所提方法对其表面形貌进行评定,验证该方法的准确性。对圆棒试样缺口底部复杂曲面的表面形貌进行评定及应力集中分析,为圆棒试样缺口底部复杂曲面表面加工质量的评定提供参考方法。     

机件端盖油液泄漏的机理分析

机件端盖油液泄漏是设备常见的问题，通过对密封结合面的微观模型的研究，发现密封垫的表面粗糙度与泄漏量之间存在很大的关系。减小密封垫的表面粗糙度可以大大减小机体端盖的泄漏。     

管道不可压缩流体泄漏量与压力变化的关系研究

实际工程中,大多数的石油运输管道只允许安装压力传感器检测泄漏情况,流量计仅安装在收费口处,而且对于不可压缩流体无法通过临界压力条件计算泄漏量。基于应力应变公式,通过研究管道的微元体受压时管壁的径向位移与管内压强的关系,得出管道体积随管道压力的应变响应。以管道容积膨胀的改变量表征管道中不可压缩流体的泄漏量,得到不可压缩流体的泄漏量计算模型。建立管道受压膨胀的COMSOL模型进行仿真验证,仿真结果和推导公式均表明管道的体积应变与管道压力呈二次抛物线关系,但当管道内压力变化不大时,二者之间可近似为线性关系。此外,建立实验平台得到了压力为0 MPa~0.8 MPa时的泄漏量,验证了不可压缩流体与压力变化之间的线性关系。理论和实验结果为管道内不可压缩流体泄漏量的计算提供了理论依据。     

超声滚压对铝合金表面质量和耐磨性影响研究

使用多珠平面滚压加工刀具对叉车举升液压缸表面实施滚压加工和超声滚压加工。通过激光共聚焦显微镜、光学显微镜和显微硬度仪对加工后的试样进行表面三维形貌、金相组织和硬度表征的研究。开发相应的分子动力学模型并对加工前后的试样进行干摩擦试验,对比研究超声滚压对液压缸铝合金表面摩擦磨损性能的影响。试验结果表明,与滚压加工相比,超声滚压加工进一步降低了表面粗糙度。磨损结果表明,超声滚压加工改变了试样表面的微观结构,改变了试样的磨损机制,提升了试样的抗磨损性能,可有效提高液压缸使用寿命,降低泄漏量。     

A numeric investigation of friction behaviors along tool/chip interface in nanometric machining of a single crystal copper structure

The interaction between the tool rake face and the chip is critical to chip morphology, cutting forces, surface quality, and other phenomena in machining. A large body of existing literature on nanometric machining or nano-scratching only considers the overall friction behavior by simply regarding the total force along tool movement direction as the friction force, which is not suitable for describing the intriguing friction phenomena along the tool/chip interface. In this study, the molecular dynamic (MD) simulation is used to model the nanometric machining process of single crystal copper with diamond tools. The effects of three factors, namely, tool rake angle, depth of cut, and tool travel distance, are considered. The simulation results reveal that the normal force and friction force distributions along tool/chip interface for all cases investigated are similarly shaped. It is found that the normal force consistently increases along the entire tool/chip interface when a more negative rake angle tool is used. However, the friction force increases as the rake angle becomes more negative only in the contact area close to the tool tip, and it reverses the trend in the middle of tool/chip interface. Meanwhile, the increase of depth of cut overall increases the normal force along the tool/chip interface, but the friction force does not necessarily increase. Also, the progress of tool into the work material does not change the patterns of normal force, friction force, or friction coefficient distributions to a great extent. More importantly, it is discovered that the traditional sliding model with a constant friction coefficient can be used to approximate the later section of friction distributions. However, no friction model for traditional machining is appropriate to describe the first section of friction distributions obtained from the MD simulation.     

Influence of machining parameters on surface roughness in finish cut of WEDM

Surface roughness is significant to the finish cut of wire electrical discharge machining (WEDM). This paper describes the influence of the machining parameters (including pulse duration, discharge current, sustained pulse time, pulse interval time, polarity effect, material and dielectric) on surface roughness in the finish cut of WEDM. Experiments proved that the surface roughness can be improved by decreasing both pulse duration and discharge current. When the pulse energy per discharge is constant, short pulses and long pulses will result in the same surface roughness but dissimilar surface morphology and different material removal rates. The removal rate when a short pulse duration is used is much higher than when the pulse duration is long. Moreover, from the single discharge experiments, we found that a long pulse duration combined with a low peak value could not produce craters on the workpiece surface any more when the pulse energy was reduced to a certain value. However, the condition of short pulse duration with high peak value still could produce clear craters on the workpiece surface. This indicates that a short pulse duration combined with a high peak value can generate better surface roughness, which cannot be achieved with long pulses. In the study, it was also found that reversed polarity machining with the appropriate pulse energy can improve the machined surface roughness somewhat better compared with normal polarity in finish machining, but some copper from the wire electrode is accreted on the machined surface.     

砂轮约束磨粒喷射精密光整加工表面微观形貌的研究

对砂轮约束磨粒喷射精密光整加工表面微观形貌进行分析，研究了工件表面尖峰去除机理和均化及改善波纹度机理。利用平面磨床M7120对精磨后的Q235A工件材料进行喷射加工实验，采用TALSURF5轮廓仪测量加工后表面的微观几何参数值，用扫描电镜观察表面微观形貌变化，用金相显微镜观察磨削烧伤。实验结果表明，随着加工循环次数的增加，表面微观形貌由方向一致的沟槽过渡到随机的、无方向性的微细凹坑，表面粗糙度值明显降低，喷射加工能减轻或消除磨削烧伤。     

精密深孔复合刀具设计及加工技术

发动机气门导管孔和气门座圈的加工是发动机缸盖加工的关键工艺之一,针对气门导管孔与气门座圈的精密加工,设计制造了专用的复合深孔加工刀具,介绍了该刀具的结构与加工原理,并在试验的基础上优选了加工刀片材料,设计了加工刀片的结构参数。通过生产试验研究了使用该刀具时切削参数对加工质量的影响规律,得出了最优加工工艺参数,试验证明该刀具在保证加工质量的基础上能够有效提高加工效率。     

Topography and microstructure of the cutting surface machined with abrasive waterjet

Abrasive waterjet (AWJ) technology has been widely used for cutting materials in precision machining. The present paper reports the surface topography and microstructure of the cutting surfaces machined by AWJ. Four different kinds of ductile metallic materials were used for preparation of specimens. With the AWJ processing technique, smooth surfaces were easily obtained with a lower surface roughness about 2 to 3 μm. By comparing the microhardness of the specimens with the control surface sample obtained by wire electrodischarge machining, it is found that there is no heat-affected zone on the cutting surfaces machined by AWJ. By observing the surface morphology and microstructure, the features of friction and wear marks are revealed. The results show that a smooth cutting surface is more easily obtained on hard materials, while erosions on soft material surfaces are more serious. All scratches have a clear consistent direction, under the action of mechanical abrasive wear.     

基于工件弹性变形的薄型非球曲面(玻璃)零件加工方法研究

针对传统非球曲面加工技术存在对设备依赖度高及加工效率较低等问题,研究了薄型非球曲面零件的弹性变形加工法,并基于材料弹性变形特性,将非球曲面加工转变为平面加工。通过理论计算及ABAQUS有限元仿真确定了平板玻璃工件在均匀压力及周边简支条件下的弹性变形面型,并对工件进行了弹性变形加工实验;加工面型与理论面型误差的最小均方根、峰谷值分别为1.66μm与2.80μm,验证了使用弹性变形加工方法进行薄型非球曲面零件加工的有效性。     

混粉电火花镜面加工试验研究

利用自行研制的混粉电火花镜面加工装置，对混粉电火花镜面加工影响因素、加工表面性能等进行了深入研究，找出了粉末特性、工件材料、粉末浓度及放电参数等对混粉电火花镜面加工后表面质量的影响规律，给出了合理的混粉电火花镜面加工工艺条件。以文中确定的加工工艺条件进行锻造和压铸模具的混粉电火花镜面加工应用，结果表明，混粉电火花镜面加工技术能够提高模具制造质量、降低工人劳动强度和缩短模具制造周期。     

Effects of machined cavity texture on ejection force in micro injection molding

The friction force developed in the demolding phase of the micro injection molding process is mainly determined by mold surface finish, which affects the tribological phenomena occurring at the polymer–tool interface. In this work, the effects on the ejection force of two cavity surfaces machined with different technologies (viz. micro milling and micro electro discharge machining), but with similar value of Ra, were investigated. The relations between different surface topography parameters and the ejection force were then analyzed, in order to identify the parameters that most appropriately describe the friction at the polymer–tool interface. The experimental results showed the strong interactions between the mold surface texture and the micro injection molding process parameters that promote the replication, such as mold temperature and holding pressure. The different machining technologies generated two mold textures that have a similar value of Ra, but their influence on friction can be properly described only using several other surface topography parameters.     

脉冲电解和直流电解磨削加工的对比实验和研究

通过脉冲电解和直流电解磨削加工的工艺对比实验 ,其分析结果表明 ,脉冲电解磨削加工的工件尺寸精度高、表面质量好。同时还得到了电解参数对工件尺寸精度和表面粗糙度值的影响规律。选择脉冲电解磨削的电参数非常重要 ,其中电流密度有一个相对最佳的选择值