圆环面刀具五坐标数复杂曲面刀位算法分析

对圆环面刀具五坐标数控加工复杂曲面编程方法进行了综述，指出大多数算法仍采用仅适用于点接触加工的以局部微分几何为基础的刀位算法。本文证明了这些算法的缺陷，提出了一种针对圆环面刀具的五坐标数控宽行加工复杂曲面的刀位计算的思想。     

基于离散模型的内超环面齿轮干涉检验方法

针对内超环面齿轮齿面加工局部和全局干涉现象,提出一种干涉检验方法,有效地避免了加工干涉。通过干涉检验面簇的引入和干涉检验线簇的构造,将内超环面齿轮齿面和刀具扫掠体离散化。运用内超环面齿轮齿面和刀具扫掠体离散模型,通过截平面处刀具中心的求解,确定内超环面齿轮齿面加工局部和全局干涉区域。通过实例分析进一步验证了内超环面齿轮齿面加工干涉检验方法的可行性。     

圆环面刀具五坐标数控加工复杂曲面刀位算法分析

对圆环面刀具五坐标数控加工复杂曲面编程方法进行了综述 ,指出大多数算法仍采用仅适用于点接触加工的以局部微分几何为基础的刀位算法。本文证明了这些算法的缺陷 ,提出了一种针对圆环面刀具的五坐标数控宽行加工复杂曲面的刀位计算的思想。     

加工直廓环面蜗杆的切刀盘的设计

<正>环面蜗杆是一个分度曲面为圆环的蜗杆,具有传动副体积小、承载能力大、传动效率高等特点,按形成蜗杆的母线的形状可分为直线环面蜗杆和包络环面蜗杆两种类型。直线环面蜗杆的轴向齿廓为直线,其制造工艺和所用刀具的刀齿型面比较简单,应用更为广泛。     

圆环面刀具五坐标数控加工复杂曲面优化刀位算法

本文分析了圆环面刀具的特点 ,提出了一种针对圆环面刀具的五坐标数控宽行加工复杂曲面的刀位计算方法。该算法把曲面离散为点 ,从宏观范围考察瞬时刀位下刀具和型面的接触误差分布 ,并按宏观曲率吻合原则对刀位进行调整优化 ,实现了宽行线接触加工。通过对叶片曲面试算证明了该算法准确。用本算法对UGⅡ软件给出的刀位进行了评估 ,证明其刀位不是优化的     

直廓环面蜗杆的变参数修型理论

从理论上推导了直廓环面蜗杆修型前后的曲面空间数学表达式,并从两方面对直廓环面蜗杆的对称修型进行具体的探讨和计算,使蜗轮齿面的动压油膜面增加,蜗杆传动性能大为改善.     

渐开面包络环面蜗杆特征建模研究

渐开面环面蜗杆的三维构建属复杂曲面造型,文章在环面蜗杆螺旋线参数方程建模的基础上,分析讨论了其与渐开面环面蜗杆螺旋齿面方程的对应关系,建立了渐开面包络环面蜗杆产型齿的特征模型。按此模型在MDT6.0三维绘图软件环境中实现了渐开面环面蜗杆的三维实体造型,并在进一步完成的"渐开面二次包络环面蜗杆副的虚拟实体"中,以断面图检验了其良好的啮合状态。所生成的实体模型具有给定参数的数字信息,可用于齿廓形状及特性分析,推动此类环面蜗杆的开发与应用研究。     

基于齿面网格的超环面行星蜗杆传动系统实体建模

超环面行星蜗杆传动系统中的关键零件——中心蜗杆和内超环面齿轮的齿面是一种复杂的空间曲面,中心蜗杆和内超环面齿轮实体模型的精确性直接影响到数控加工的精度。研究了中心蜗杆数字化建模问题,根据中心蜗杆的数学模型,对其螺旋齿面进行网格划分,提出基于齿面网格的超环面行星蜗杆传动系统精确实体建模方法,并通过数控加工进行了验证。     

斜平面二次包络环面蜗轮齿面的数字化与仿真

在空间啮合理论基础上,合理选择斜平面二次包络环面蜗杆副标架,分析原始型斜平面二次包络环面蜗轮的曲面结构,运用MATLAB进行曲面构造,实现了蜗轮曲面的数字化模型;应用Pro/E三维实体造型软件进行斜平面二次包络环面蜗轮的实体仿真和运动仿真,并对仿真的结果做了进一步的分析和验证。     

平面2次包络环面蜗轮副三坐标测量的数据处理

在综合分析了几种曲线，曲面测量方法的基础上，实现平面2次包络环面蜗轮副的三坐标测量实践，探讨采用“三点共圆法”进行测量数据的处理的方法，实现对测量数据进行闭戏补偿研究，并对数据处理精度进行了分析，获得平面2次包络环面蜗轮副的啮合面数据矩阵，为平面2次包络环面蜗轮副的重构及误差分析打下基础。     

平面二次包络环面蜗杆传动的实体建模研究

对平面二次包络环面蜗杆传动的三维建模进行了深入的研究,推导出了平面二次包络环面蜗杆螺旋线方程,并利用螺旋线方程进行了建模,建模过程简单,容易进行参数化,为该类型的蜗杆传动提供了较好的建模方法.     

圆环面砂轮磨削复杂形状刀具前刀面的分析研究

对复杂形状刀具前刀面数控磨削常用磨削方式的磨削过程进行了深入的研究，在此基础上，提出了采用圆环面砂轮进行复杂形状刀具前刀面数控磨削的磨削方式，并对其磨削过程进行了3维仿真分析研究。采用这种磨削方式进行复杂形状刀具前刀面的磨削加工，可精确保证刀具设计所要求的前角，得到理想的前刀面，并且具有砂轮制造及修整简单、适用范围广、刀位计算简洁等优点，具有很强的实用性。     

环形刀宽行加工圆弧过渡区域算法的研究

基于广域曲率吻合原则,研究了利用环形刀侧铣加工组合曲面圆弧过渡区域的新方法。首先建立环形刀的几何模型,通过调整刀具姿态角,使刀具表面和工件表面在不发生干涉的条件下实现密切接触。通过迭代判断使下行刀轨的驱动线和当前刀轨在精度范围内搭接,实现刀轨的合理编排。最后,以某航空发动机叶片为例计算了刀轨。结果表明,该算法能够精确地加工出圆弧过渡曲面,刀轨之间的没有明显的残高,加工效率较球头刀提高了5倍。     

A tentative explanation for the tribochemical effects in fretting wear

In many fretting investigations, tribochemical reactions have been reported to critically determine the wear and friction behavior, however, different and contradictory assessments of the importance of mechanical and thermal effects on these reactions have been suggested. Since fretting is characterized by relatively slow sliding speeds, high temperatures are not generated over the entire nominal contact area. However, evidence for phase transformations, which are typical of high temperatures, have been observed many times in fretting experiments. In other words, there exists a discrepancy between the macro- and micro-scale observations. In our previous experimental and theoretical work, the tribochemical transformations of steel and ceramics were extensively investigated and the presence of very high flash contact temperatures under gross slip fretting was confirmed. In this paper we present a tentative explanation of the mechanism for the observed tribochemical changes under selected fretting conditions, which can also explain the discrepancy in the results from macro- and micro-scale studies. The proposed wear mechanism considers the tribochemical transformations at the asperity spot-to-spot contacts due to high flash temperatures, while the heat generation and dissipation at apparent contact area remain significantly lower. The observed overall wear transition occurs due to gradual accumulation of the transformed material, which in “closed” fretting contacts remains in great part within the contact.     

Determination of parent orientation maps in advanced titanium-based alloys

In the past few years, reconstruction methods have been developed and applied successfully to restore the β microtexture in titanium alloys. This contribution shows how these methods are extended to other transformations often encountered in advanced titanium alloys: the α (hcp)→γ (tetragonal) and the β (bcc)→O (orthorhombic) transformation. The efficiency of the restitution depends on specific crystallographic features of the investigated phase transformations. Therefore, the paper outlines these crystallographic specificities for some advanced titanium alloys. To illustrate the capability of the method to reconstruct the parent phase, different restored parent microtextures of these alloys are presented. The results show that the reconstruction methods are an efficient tool to study the microstructure and texture modifications induced by these phase transformations.     

Analytic solutions of flowfields inside a rolling deformed torus

The flowfields inside a deformed rolling torus are analyzed in the limit where the cross-sectional diameter is small in comparison to the torus diameter. The geometric domain consists of a torus whose cross-section is circular except in the footprint region where the cross-section is flattened. Analytic formulas for the flow velocities and pressures are derived and followed by a coordinate transformation. Results for the pressure fields are presented with the Poiseuille flow limit.     

论成人高等教育变革中的观念转变

我国成人高等教育当前正面临着由传统的注重学历文凭教育，向倡导终身学习、注重成人发展转型。要实现这一转型，必须从观念的转变入手，在教育目的观、价值观上，实现从“成材”到“成人”的转变；在师生观、教学观上，实现从“重教”到“重学”的转变；在学习观上，实现从“学会”到“会学”的转变。这三方面观念的转变相互联系，相互影响，逐层递进。     

高炉余压回收透平机静叶和球形环的补焊

针对高炉炉顶余压透平机静叶和球形环的损坏原因进行了详细分析,阐述其相应的处理措施,介绍了透平机静叶和球形环的修复及补焊的方法。     

Vortical flow structures behind a torus with an aspect ratio of three

A torus could replace an orifice flow meter with the benefit of a lower pressure loss. The flow structure of a torus with an aspect ratio of three was scrutinized in a wind tunnel. This study details the vortical structures at 5, 7, 10 and 15 core diameters downstream of the torus. This paper also studied the drag coefficient of the torus. The Reynolds numbers based on core diameter and free stream velocity are 9 × 10³, 1.2 × 10⁴ and 1.5 × 10⁴. Of particular interest is the resulting Strouhal number through the opening. This was evaluated through detailed flow turbulence characterization.