面向航天器装配现场技术问题的知识挖掘和推荐方法

针对航天器研制型生产特点导致的装配现场技术问题难预测、现有知识推荐方法难适用的问题，对技术问题的场景、关键因素等进行了深入研究，提出一种面向航天器装配现场技术问题的知识推荐方法。首先提出了技术问题知识实例和问题场景的组织模型，实现了技术知识的规范化表达。然后使用主题模型对问题场景进行主题特征提取，并基于场景主题向量对技术问题的关键属性进行筛选，实现对技术问题的量化表征。最后通过对当前问题场景特征的识别，利用检索算法实现知识推荐。通过在企业实际数据集上的实验，验证了该方法的有效性。     

工业设备安装技术的应用要点分析

在对工业设备进行管理的过程中，经常会产生像技术问题、质量问题、安全问题、资金问题等，且在进行工作的过程中，有一些工作人员没有遵守相应的规章制度，不仅无视领导的管理，缺乏相应的合作意识，还会出现一些不符合当前规章制度的行为。很多的工业企业也没有及时对安全设施进行完善，没有对工业设备进行维修保养，从而导致工业设备出现一些问题，而工作人员也会在防护措施不到位的情况下受伤。因此，本文对于工业设备安装技术的应用要点进行分析，仅供参考。     

关于商誉若干问题的探讨

随着企业改制、购并、资产重组和股份制事作等经济业务的不断发展，如何正确认识企业商誉，已日益成为实务界和学术界关注的问题。本就是在商誉的概念、本质及形成原因的基础上，对商誉若干问题进行思考。通过对这些问题探讨，加深对商誉这种无形资产的认识。     

小电流接地系统接地检测工程应用分析

针对目前小电流接地系统的接地选线装置现场选线的准确性差、投入率不高的问题，根据系统的特点，时问题进行了工程应用上的分析，经过对小电流接地系统的理论分析、选线设备原理、采样误差等方面对问题进行剖析，提出了减小综合测量误差，提高选线准确性、可靠性的措施。     

浅谈灭火器监管现状及工作对策

灭火器作为社会公共安全产品，由于其结构简单、轻便灵活、易操作的特点，被广泛使用于各类场所。合理配置灭火器对扑救初起火灾，减少火灾损失，保护人身和财产安全提供了可靠保障。笔者结合灭火器日常监督管理工作，对工作中灭火器检查常见的问题进行了总结，对存在问题的原因进行了分析，并针对问题原因提出下一步工作对策，提出改进监管对策。     

复杂布局设计问题的算法

复杂布局设计问题在理论上属带性能约束的装填布局问题、NPC问题、方案设计问题，具有广泛的应用领域。着重介绍了对复杂布局设计问题的求解算法和应用，讨论了其存在的问题及发展趋势。     

航空发动机供油管裂纹失效分析

某航空发动机供油管在使用过程中出现了裂纹失效问题，为明确问题的性质和原因，通过观察供油管外观、裂纹断口分析、金相组织检测、硬度试验、强度计算等工作对问题原因进行分析。最终结论为：导管裂纹处为疲劳裂纹，导管活动接嘴处焊接变形量较大，与相邻导管进行插入式装配后会导致两导管未对中装配，从而引入装配应力，管路长时间工作后，受振动应力作用，焊缝处强度薄弱环节产生疲劳裂纹，最终造成供油管开裂。文中对导管接头焊缝处采用自动焊，减少打磨次数，控制焊接变形量，为保证插入式连接处有充分的轴向活动空间，避免对导管造成附加应力，建议插入式连接尽量保证活动接头在中间位置，以避免此类问题再次发生。     

ETA2000-1维修过招（下）

上一期说到ETA2000-1走时不足的问题，通过零件清洗、对部分零件进行特殊处理、组装自动系、目测、条盒的检查等方法能有效解决这一问题。本期将对ETA2000—1走时不准的问题进行分析，针对此问题给出解决方案。     

浅谈农民工的社会保障问题

当前，农民工的社会保障仍然存在许多的问题，包括农民工社会保障程度低、社会保障法规执行力度不够等诸多问题，这些问题的解决关系到社会经济的可持续发展，关系到和谐社会的建设。文章对福建省农民工的社会保障现状、存在的问题及原因进行了分析，同时针对问题和原因提出了一些完善农民工社会保障的对策建议。     

国务院出台质量管理新规定

为进一步提高产品质量，国务院最近出台了5条质量管理新措施。1．经国家监督抽查一次不合格的产品，进行通报批评；问题严重的，发“黄牌”警告。2．对抽查不合格的企业，按产品质量问题的严重程度，以压产停产等方式进行限期整改。3．企业整改后，复查产品仍不合格的，国有企业要免去厂长职务，不得易地担任领导职务，乡镇、个体企业，由工商部门暂停或吊销营业执照．4．对质量问题严重、影响大、关系到人民群众生命安全的产品，予以揭四，公开曝光．5．对因产品质量问题造成严重损失、触犯刑律的，追求刑事责任。国务院出台质量管理新规定…     

ELID镜面磨削砂轮氧化膜生成机理

采用铸铁结合剂微细超硬磨料砂轮进行在线电解修整磨削时,ＥＬＩＤ砂轮表面产生的氧化膜起着极其重要的作用。研究了ＥＬＩＤ砂轮电解氧化膜的粘附强度、硬度、致密性、导电性、生成速度与砂轮结合剂成分、磨削液成分和电解参数的关系。     

磨削过程模拟及磨削机理研究（上）

在前人磨削理论基础上对砂轮结构做了更接实际的随机性假设,应用计算机数字模拟技术对磨削全过程进行了模拟,获得了磨削过程和磨削表面的许多重要数据和结果,给出了砂轮表层的磨料中中切削的磨粒数目和切屑的长度、厚度和体积。在研究砂轮结构的基础上得出砂轮磨粒分布的随机性是磨削加工能产生表面低粗糙度的重要因素。对砂轮磨料粒度及砂轮修整的定量研究表面,要获得超低粗糙度值磨削表面不仅需要选择较细磨粒,而且需要对砂轮     

Modeling and simulation of grinding surface topography considering wheel vibration

Grinding is an important means of realizing precision and ultra-precision machining. Vibration caused by an unbalanced grinding wheel in grinding process has a significant impact on the quality of workpiece surface. However, the effect of wheel surface topography and/or the relative vibration between grinding wheel and workpiece are not considered in most researches. Taking the relative vibration between grinding wheel and workpiece into account, alongside the abrasive grain trajectory equation, a new analysis and simulation model for surface topography of the grinding process is established. The model for the topography of the grinding wheel surface is first studied, and subsequently, a new simulation model for surface topography of the grinding process is proposed. Case studies are performed at the end, and the influence of grinding wheel vibration amplitude, wheel grit number, as well as grinding parameters on the surface waviness and roughness is discussed. The simulation results could be used to optimize the actual grinding process to improve the ground surface quality or predict the surface topography by given grinding parameters.     

Coolant flow in surface grinding with non-porous wheels

A parameter that is often used in the assessment of cooling efficiency in grinding is the amount of fluid that flows through the grinding zone. This paper shows that when grinding with wheels possessing no bulk porosity, only a portion of the flow through the grinding zone is effective. Even at the highest wheel speeds employed, it is observed that ample fluid travels on the wheel surface and is re-directed into the grinding zone — a phenomenon that may adversely affect cooling and wheel cleaning. Therefore fluid rejection off the wheel is important. A theoretical model for fluid rejection is proposed, that describes the drop formation process, presents the operating instabilities, identifies characteristic time and length scales, and predicts the amount of rejected fluid. Although the surface roughness of the wheel is important in quantifying coolant flow rates, a smooth wheel is employed in this work to study first order effects. Preliminary experimental results obtained for a rough grinding wheel are in conformance with those for a smooth wheel.     

磨削表面白层厚度影响因素的实验研究

通过淬硬轴承钢GCrl5的磨削实验,研究了砂轮速度、工件速度、磨削深度以及冷却方式等磨削参数对白层厚度的影响规律.实验表明:白层是由磨削过程中工件快速升温和快速冷却以及强烈的塑性变形引起的,白层厚度的变化是磨削加工过程中各种参数共同作用的结果,而其中磨削深度是主要原因,其次是砂轮速度和工件速度;白层厚度随砂轮速度和磨削深度的增大而增大;低的砂轮速度和磨削深度以及良好的冷却条件能有效抑制白层的产生.根据实验统计结果提出了预测磨削白层厚度的经验公式.     

Experimental study of wheel wear in electrolytic in-process dressing and grinding

Profile accuracy of components ground with ultra-precision machine tools is primarily dependent on wheel wear. Quantitative analysis of wheel wear is therefore an important aspect for precision grinding with electrolytic in-process dressing (ELID). In this paper, wheel wear is measured from ELID grinding experiments with different dressing and machining parameters. The grinding forces and dressing current characteristics of the experiments are also compared. Based on the results, a benchmark function is defined for wheel wear rate. A relation for identifying insufficient dressing from sufficient dressing for particular machining conditions is also identified. It is found that insufficient dressing produces pitting and/or arcing on the wheel surface, and wheel wear can be linearly correlated to ELID grinding conditions when the wheels are sufficiently dressed.     

基于砂轮法向跟踪的回转曲面磨削研究

在回转曲面的磨削中,采取小直径平行砂轮代替圆弧砂轮的方法,保证曲面磨削点的法向始终与砂轮表面垂直,实现砂轮法向跟踪磨削.根据磨削轨迹,建立了磨削表面残留高度模型,分析了砂轮半径、工件曲率和进给速度对残留高度的影响.并进行磨削试验,得出了砂轮半径、工件曲率及进给速度对表面粗糙度的影响曲线,其变化规律与残留高度的变化规律基本一致,证明在回转曲面磨削中,可以通过控制残留高度的大小来改善磨削表面粗糙度.     

Evaluation of grinding wheel loading phenomena by using acoustic emission signals

In the industrial manufacturing field, machining is a major process. Machining operations involve grinding, drilling, milling, turning, pressing, molding, and so on. Among these operations, grinding is the most precise and complicated process. The surface condition of the grinding wheel plays an important role in grinding performance, and the identification of grinding wheel loading phenomena during the grinding process is critical. Accordingly, this present study describes a measurement method based on the acoustic emission (AE) technique to characterize the loading phenomena of a Si₂O₃ grinding wheel for the grinding mass production process. The proposed measurement method combines the process-integrated measurement of AE signals, offline digital image processing, and surface roughness measurement of the ground workpieces for the evaluation of grinding wheel loading phenomena. The experimental results show that the proposed measurement method provides a quantitative index from the AE signals to evaluate the grinding wheel loading phenomena online for the grinding mass production process, and this quantitative index is determined via some experiments in advance in the same grinding environment to help the monitoring and controlling of the grinding process.     

3D metal removal simulation to determine uncut chip thickness, contact length, and surface finish in grinding

The two most important geometric parameters that describe the mechanics of grinding are the uncut chip thickness and the contact length. Currently, analytical approaches are used to estimate these parameters. The accuracy of these approaches, however, is limited because they do not take into account the random shape, size, and protrusion height and placement of the abrasive grains around the circumference of the grinding wheel. In this paper, a simulation technique was used to gain new insight into the effect of the stochastic nature of grinding wheels on the geometric properties of the grinding process. The simulator was used to calculate the number of active grains, uncut chip thickness, and contact length for a stochastic wheel model of Radiac Abrasive’s WRA-60-J5-V1 grinding wheel. These values were then mapped to every grain on the grinding wheel and used to determine the instantaneous material removal rate of the wheel and workpiece surface finish. There was excellent agreement between the predicted and experimentally measured surface topology of the workpiece. The results suggest that only 10–25 % of the grains on the grinding wheel are active and that the average grinding chip may be as much as ten times thicker and ten times shorter than would be produced by a grinding wheel with a regular arrangement of cutting edges as assumed by existing analytical approaches.     

Simulation of elliptical patterns based on grinding with wheel dressed by elliptical tool

Dressing is a sharpening operation aimed to produce a specific groove shape on the active surface of the wheel. The preparation of grinding tools in special way is the most important enabling factor in the grinding process. It greatly influences the subsequent geometry of the workpiece. As the groove shape of the wheel surface determines the shape of the surface patterns, therefore, it is essential to produce desired groove on the wheel cutting surface before grinding. Therefore, an elliptical groove surface pattern model is proposed based on grinding with dressed wheel. An elliptical tip tool is used for the dressing process to make grooves on the wheel instead of sharp tip tool or rounded tip tool in the previous work. The dressing tool passes helically over the surface of the grinding wheel for making grooves. After that, the grooved wheel passes over the flat surface to generate elliptical patterns. The results showed the three-dimensional geometry of the surface patterns with elliptical groove which are uniformly distributed on the workpiece. An experiment is carried out for the verification of the simulation results and it is revealed that the simulation results agreed well with the experiment.