Accuracy test of five-axis CNC machine tool with 3D probe–ball. Part I: design and modeling

The error model of CNC machine tool describes the relationship between the individual error source and its effects on the overall position errors. A practical problem in applying this technique to five-axis machine tool is that the predicted position errors cannot be justified. This paper, the first in a set of two, presents a new measurement device, the probe–ball, which can be used to measure the overall position errors of five-axis machine tools directly. To perform the accuracy test, a three-degree-of-freedom (3D) measuring probe is installed in the main spindle and a base plate is fixed on the turntable. The kinematic chain of the five-axis machine tool is then closed through connecting the central ball on the base plate with the extension bar of the probe. To generate simultaneous axes motion under the condition of closed kinematic chain, the central ball is defined as origin of the workpiece coordinate frame and the probe is driven along a path on a spherical test surface with the central ball as center. The overall position errors are measured with the 3D measuring probe. A theoretical model is derived to explain the nature of the probe–ball error measurements.     

一种并行工程信息集成框架的构建

本文针对现有的并行工程信息集成框架对并行工程只提供消极支持的问题展开讨论，通过技术域，支撑域，管理域三个域的建立与分析，特别是对ＣＦ积极支持方法进行探讨，提出一种推拉式的建模思想，实现对并行设计的监督和控制。并依此思想建立了一个ＣＥ信息集成框架。     

新型镍基粉末高温合金动态再结晶的数学模型

采用Gleeble 15 0 0热模拟试验机对新型镍基粉末高温合金在 10 70℃～ 1170℃ ,应变速率为 5× 10 - 4s- 1～2× 10 - 1s- 1的条件下进行了轴向压缩试验。通过加工硬化率和应变的关系曲线确定稳态应变εs,并绘制了该合金的动态再结晶图。结果表明 ,Zener Hollomon参数变化对动态再结晶的临界应变量影响较小 ,对稳态应变量影响较大 ,并建立了该合金的动态再结晶动力学模型和晶粒尺寸模型     

脆硬材料加工机理的研究

为了了解脆硬材料的加工情况，本文采用扫描电镜和高速摄影机对典型的脆硬材料，玻璃的磨削过程，静态，动态地进行了细致的观察和分析，提出了脆理材料的磨削模型，该模型全面地反映出整个加工过程中所发生的现象，对脆硬材料的加工有指导意义。     

Numerical simulation of microstructure formation ofAZ91 using mCA method

A stochastic model for simulating the microstructure formation of Mg alloy AZ91 during solidification was developed based on the finite element method（FEM） for macroscopic model of heat transfer calculation and a modified Cellular Automaton （mCA） for microscopic modeling of nucleation, growth of crystal. In this model, the effect of solute redistribution, interface curvature and preferred orientation was considered. A numerical simulation was developed with C＋＋ program language. The computation was carded out to understand the effect of varying processing parameters, such as nucleation parameters and heat transfer coefficient, on the microstructure formation of AZ91. The result of simulation was displayed on screen.     

高压粉末制样-X射线荧光光谱法测定海洋沉积物中28种组分

常规粉末压片制样是一种简单、高效的绿色环保制样技术,但是应用于某些沉积物样品制备存在样片表面粗糙和粉末容易脱落的问题。实验采用高于常规的压力进行样品制备,建立了X射线荧光光谱法(XRF)分析海洋沉积物样品中包括硫、氧化钠、氧化镁、三氧化二铝、二氧化硅、五氧化二磷、氧化钾、氧化钙、二氧化钛、氧化锰、三氧化二铁、钴、镍、铜、锌、钒、铬、镓、铌、锆、钇、锶、铷、铅、钡、镧、钕和铪在内的28种主、微量组分的方法。探讨了压力为300 kN和1 600 kN时的制样效果,并尝试引入BP神经网络模型利用其非线性拟合能力校正主量组分的基体效应。结果表明,采用1 600 kN压力制备的样片,表面致密、光滑、不龟裂和不掉粉,制样重复性和测试精密度也有较大提高。以55个有证标准物质中17种组分的数据集为训练样本,建立了海洋沉积物样品中主、微量组分的遗传算法-BP神经网络预测模型。按照实验方法对各组分含量相对较低的实际样品连续测试12次,计算得方法的检出限在 0.63～634 μg/g之间;精密度试验结果表明,各组分测定值的相对标准偏差(RSD, n=7)为0.16%～25.1%。方法用于海洋沉积物实际样品分析,其分析结果与国标法的测定结果吻合,能够满足海洋沉积物样品中多种组分准确分析的要求。     

反求工程的产品几何建模技术研究

分析了目前在反求工程产品几何建模中广泛应用的曲面模型的局限性，指出反求工程为实现创新功能必须采用产品特征模型，提出了基于实体造型的特征建模方法。这种方法可以避免曲面模型的缺陷，拓宽反求工程的应用范围，是实现三维重构的新方法。探讨了有关的理论和关键技术。     

数控机床铣削等距型面轴的理论研究

提出了在数控机床上铣削等距型面轴的新方法。通过建立和分析等距曲面及其加工中有关问题的数学模型，得到了数控铣削等距型面轴时确定自适应步长的算法以及行距、残留高度等重要理论问题的计算公式，为等距型面轴数控加工的实验研究奠定了理论基础。     

Flattening and solidification of thermally sprayed particles

In this article, molybdenum particles were plasma sprayed on copper, zirconia, and glass substrates. The impact of the molten particles was monitored using a fast two-color optical fiber pyrometer focused on a small spot on the substrate surface. The apparent duration of the flattening process and the cooling speed, both determined from the pyrometer signals, were found to depend on the substrate conditions and to vary with coating thickness. The substrate material and its roughness were also found to influence the texture in the sprayed coatings. Furthermore, a transient thermal flow numerical model was used to compute reliable thermal histories of the impinging particles and the underlying lamellae, the interfacial thermal resistance being determined by comparison of experimental thermograms with computed ones.