螺杆数控机床加工中自动编程系统的研究

针对螺杆数控加工中关键的数控编程问题,这里通过对螺杆数控加工中编程方法的研究,提出了一种计算机辅助自动编程系统的设计方法,介绍了该方法的基本设计思想和一个自动编程系统的基本功能。     

汽轮机叶片数控加工中CAD技术的应用

针对汽轮机叶片型面在数控加工中遇到的数控编程问题 ,提出了应用CAD技术来实现数控辅助编程的思路。结合MDT软件 ,介绍了应用其曲面模块AutoSurf实现叶片汽道型面的曲面造型和数控辅助编程的方法     

钣金数控冲编程工艺分析与处理

钣金件的加工离不开数控冲技术,而数控冲技术中最重要的一环就是数控冲编程。数控冲编程的好坏对数控冲床的使用、生产效率、板材利用率及钣金件质量等都有着至关重要的影响。本文就数控冲编程中遇到的一些问题进行了工艺分析,并针对具体问题给出了相应的处理办法,总结出一些有效的数控冲编程方法。     

数控编程G指令使用的探讨

论述了数控编程中正确使用G指令的意义。以数控车工编程为例,指出了G指令使用中存在的几个问题,介绍了正确使用G指令的几点心得,供广大数控编程初学者共同探讨、借鉴。     

基于壳体典型特征的数控加工快速编程研究

基于特征进行编程是实现数控加工高效、快速编程的基础,针对这一问题,对基于壳体典型特征的数控加工快速编程进行了研究。通过分析壳体零件典型制造特征,将数控加工工步信息、刀具、切削参数通过用户化模板进行定制开发,形成壳体典型特征应用库,供不同用户进行数控加工编程时共享。在应用中,可以实现加工工艺信息的自动给定,通过简单设置便可完成数控加工编程,进而大幅提高数控加工编程效率。     

子程序数控铣削加工编程中的应用

数控编程作为数控加工和重要组成部分,为提高程序编写质量和加工精度,结合数控程序的简化编写方法,使用子程序在数控编程中可大大提高编程效率及使用宏程序简化编程可进一步提高编程序的简洁性,还可以扩展数控加工的范围,论文以实例的形式对子程序和宏程序的应用进行了简要的说明.希望为从事数控加工编程的相关人员提供帮助和借鉴.     

高速切削数控编程关键技术的研究

文中通过对高速切削现状和特点的研究,与传统的数控编程相比较,提出了新的数控加工编程策略,开发了高性能数控编程系统,促进和带动了高速切削数控编程技术的发展,对提高编程效率和编程质量,缩短加工调试时间,减少程序出错率等具有重要意义.     

汽轮机叶片数控加工中CAD技术的应用

针对汽轮机叶片型面在数控加工中遇到的数控编程问题,提出了应用ＣＡＤ技术来实现数控辅助编程的思路,结构ＭＤＴ软件,介绍了应用其曲面模块ＡｕｔｏＳｕｒｆ实现叶片汽道型面的曲面造型和数控辅助编程的方法。     

基于STEP-NC的高速加工数控编程

高速加工技术是近年来发展起来的一种集高效、优质和低耗于一身的先进制造技术，其中高速加工数控编程是高速加工技术中极为重要和非常复杂的技术。笔者在分析了传统数控编程接口局限性的基础上，提出基于新型数控编程接口STEP—NC的高速加工数控编程方法。分析和阐述了STEP—NC用于高速加工数控编程的主要特点，并给出了具体的加工实例。     

数控车削子程序典型零件案例分析

为了提高数控程序编写质量和编程效率,结合数控程序的简化编写方法,使用子程序在数控编程中既可大大提高编程效率和程序的简洁性,还可以扩展数控加工的范围。文中以实例的形式对子程序在数控车床上加工等宽槽、等宽不等距槽进行了简要的编程说明。可为从事数控加工编程的相关人员提供帮助和借鉴。     

Mice embryology: A microscopic overview

In this work, we studied the embryology of mice of 12, 14, and 18 days of gestation by gross observation, light microscopy, and scanning electron microscopy. Grossly, the embryos of 12 days were observed in C‐shaped region of the brain, eye pigmentation of the retina, first, second, and third pharyngeal arches gill pit nasal region on the fourth ventricle brain, cervical curvature, heart, liver, limb bud thoracic, spinal cord, tail, umbilical cord, and place of the mesonephric ridge. Microscopically, the liver, cardiovascular system and spinal cord were observed. In the embryo of 14 days, we observed structures that make up the liver and heart. At 18 days of gestation fetuses, it was noted the presence of eyes, mouth, and nose in the cephalic region, chest and pelvic region with the presence of well‐developed limbs, umbilical cord, and placenta. Scanning electron microscopy in 18 days of gestation fetuses evidenced head, eyes closed eyelids, nose, vibrissae, forelimb, heart, lung, kidney, liver, small bowel, diaphragm, and part of the spine. The results obtained in this work describe the internal and external morphology of mice, provided by an integration of techniques and review of the morphological knowledge of the embryonic development of this species, as this animal is of great importance to scientific studies. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Gait definition and successive gait-transition method based on energy consumption for a quadruped

In nature,to realize the smooth motion for different speeds,the continuous gait transition is usually required for the quadrupeds.Thus,the gait simulation of quadrupeds is a requisite step to obtain the stable and energy-efficient gait for the walking machines.In this paper,the definitions of the two gait parameters,phasic difference and duty factor are presented,which can determine the gait of the quadrupeds.Then,several typical gaits of the quadrupeds are analyzed such that the seven standard gaits and corresponding parameters are summarized.Additionally,the variance law of the two parameters,which determine the relationship of gait transition,is analyzed.Furthermore,the quadruped gait derivative spectrum (QGDS) is proposed and the gait definition of the quadrupeds is presented.To minimize the power consumption,the choice criterion of gait,the optimal gait in terms of the motion speed,duty factory,and power consumption for the walking machines,is developed.Last,the continuous variance of the gait is implemented by the simulation of the gait transition from walk to trot,which evaluate the choice criterion and transition of gait.     

过渡金属作用下的金刚石石墨化机理研究*

从电子和原子角度解释了过渡金属对金刚石石墨化催化作用的机理,即过渡金属具有空d轨道,并且在某一面上与金刚石(111)面原子符合对准原则。为了验证此结论,基于第一性原理建立铬、铁、钴、钛、铂、铝、铜原子与金刚石原子的作用模型,进行仿真计算,得到不同过渡金属对金刚石石墨化的影响规律。仿真结果表明：Cr、Fe、Co、Ti、Pt作用下的金刚石结构出现不同程度的石墨化现象,而Al、Cu作用下的金刚石无石墨化现象。不同金属作用下金刚石原子结构的平面度由小到大依次为铁、铬、钴、钛、铂、铝、铜;碳原子间方差由小到大依次为铁、铬、钴、铂、钛、铝、铜;系统能量变化由大到小的顺序依次为铁、铬、钴、铂、钛。通过比较,铁、铬、钴原子对金刚石石墨化具有明显的催化作用,铂、钛原子有一定的催化作用,而铝、铜原子则无催化作用。当金属具有空d轨道且与金刚石在一定面上符合对准原则,未配对电子越多,金属对金刚石石墨化的催化作用越强;反之,当金属价电子层无d轨道或d轨道电子是充满状态时,金属对金刚石石墨化无催化作用。该研究为利用金刚石石墨化机理刃磨金刚石刀具提供了理论基础。     

Subcommissural organ, cerebrospinal fluid circulation, and hydrocephalus

Under normal physiological conditions the cerebrospinal fluid (CSF) is secreted continuously, although this secretion undergoes circadian variations. Mechanisms operating at the vascular side of the choroidal cells involve a sympathetic and a cholinergic innervation, with the former inhibiting and the latter stimulating CSF secretion. There are also regulatory mechanisms operating at the ventricular side of the choroidal cells, where receptors for monoamines such as dopamine, serotonin, and melatonin, and for neuropeptides such as vasopressin, atrial natriuretic hormone, and angiotensin II, have been identified. These compounds, that are normally present in the CSF, participate in the regulation of CSF secretion. Although the mechanisms responsible for the CSF circulation are not fully understood, several factors are known to play a role. There is evidence that the subcommissural organ (SCO)--Reissner's fiber (RF) complex is one of the factors involved in the CSF circulation. In mammals, the predominant route of escape of CSF into blood is through the arachnoid villi. In lower vertebrates, the dilatation of the distal end of the central canal, known as terminal ventricle or ampulla caudalis, represents the main site of CSF escape into blood. Both the function and the ultrastructural arrangement of the ampulla caudalis suggest that it may be the ancestor structure of the mammalian arachnoid villi. RF-glycoproteins reaching the ampulla caudalis might play a role in the formation and maintenance of the route communicating the CSF and blood compartments. The SCO-RF complex may participate, under physiological conditions, in the circulation and reabsorption of CSF. Under pathological conditions, the SCO appears to be involved in the pathogeneses of congenital hydrocephalus. Changes in the SCO have been described in all species developing congenital hydrocephalus. In these reports, the important question whether the changes occurring in the SCO precede hydrocephalus, or are a consequence of the hydrocephalic state, has not been clarified. Recently, evidence has been obtained indicating that a primary defect of the SCO-RF complex may lead to hydrocephalus. Thus, a primary and selective immunoneutralization of the SCO-RF complex during the fetal and early postnatal life leads to absence of RF, aqueductal stenosis, increased CSF concentration of monoamines, and a moderate but sustained hydrocephalus.     

平接型双材料的载荷位移特征与界面失效机理研究

针对双材料界面强度不足与界面应力分布不均的问题,对双材料界面强度、界面应力分布不均、载荷位移曲线(LD)波动等方面进行了试验研究与理论分析,利用铝/聚乙烯(PE)、铝/聚丙烯(PP)、铝/聚甲醛(POM)双材料的实验结果,对材料的TS813粘结试样界面强度与Ergo5800粘结试样进行了比较分析,对弹性模量与PE、PP、POM材料的界面强度进行了对比,分析了载荷位移曲线与界面断口。研究结果表明:铝/非金属双材料界面抗拉强度随着弹性模量增大而减小,TS813试样界面强度为Ergo5800试样的4.44、2.17、2.89倍,铝/橡胶前者为后者76.47%;界面强度分布不均导致界面剥落情况不同与LD曲线中波动现象,同种材料试样与同种粘结剂试样,试样界面强度越低载荷波动越明显。     

Dynamic characteristics of a planetary gear system based on contact status of the tooth surface

Studies on the planetary gear have attracted considerable attention because of its advantages, such as compactness, large torque-to-weight ratio, vibrations, and high efficiency, which have resulted in its wide applications in industry, wind turbine, national defense, and aerospace fields. We have established a novel dynamic model of the planetary gear transmission by using Newton’s theory, in which some key factors such as time-variant meshing stiffness, phase relationships, and tooth contact characteristics are considered. The influences of gear axial tipping, operating conditions, and the meshing phase on the contact characteristics and the dynamic characteristics were researched systematically. It was found that the contact area of the tooth surface was moved due to the axial gear tipping, which obviously affected the meshing stiffness. With the increase in the inclination angle of the sun gear, the meshing stiffness decreases, which produces an evident influence on the high natural frequency in the planetary transmission system. In terms of the dynamic characteristics of the system, the component of rotating frequency appeared in the dynamic meshing force of the sun gear and the planetary gear. Moreover, the floating track of the center wheel varied significantly and exhibited an oval distribution as the inclination angle of the sun gear changed. When the inclination angle of the sun gear increased, the rotating frequency component increased significantly, but the other meshing frequency components remained unchanged; meanwhile, the deformation of the floating track also increased. If the inclination angle of the sun gear changes, the vibration state of the system and the collision impact could become more serious, and the lifetime of the planetary transmission system will reduce. Furthermore, when the load was increased, we found that the gear-tooth contact zone transformed from line contact to surface contact, the meshing stiffness increased, the effect of high natural frequency on the planetary transmission system became more evident, but its low-order natural frequency remained stable. With regard to the dynamic characteristics of the system, the components of the major frequency at the external gearing remained unchanged, but the rotation frequency of the sun gear and the meshing frequency amplitude increased linearly with the increase in load. In conclusion, the variation in the meshing stiffness of the planetary gear system had minor impact on the low-order natural frequency, but had a significant impact on the high natural frequency of the planetary transmission system due to the phase variation of the gear.     

多壁碳纳米管增强无石棉垫片性能研究

为了优化配方并提高无石棉垫片的性能,以加入多壁碳纳米管(MWCNTs)的无石棉垫片为研究对象,对MWCNTs和无石棉垫片的主要组成材料进行均匀配方设计,对制备的无石棉垫片材料进行拉伸强度、压缩率与回弹率、密度和老化系数的性能测试;采用多元线性回归分析建立垫片各项性能与材料配方之间的回归模型,并进行验证。结果表明:综合性能最优时的配方(按质量分数)如下:多壁碳纳米管2. 48%、QY棉18. 58%、矿物棉23. 22%、高岭土23. 22%、云母6. 19%、滑石粉13. 93%、纸浆12. 38%;得到的回归方程式可以用来预估垫片材料的各项性能;不同组分材料对垫片材料性能的影响不一样,其中MWCNTs的含量对垫片的各项性能影响最大,且MWCNTs的加入能改善复合垫片材料的老化性能;随着MWCNTs含量的增加,无石棉垫片的拉伸强度、回弹率、密度和老化系数都增大,但压缩率逐渐减少。因此,在保证垫片材料的压缩率满足要求的前提下,适当增加MWCNTs的含量能显著提高无石棉垫片的性能。     

1214Bi易切削钢冶炼连铸工艺优化

通过对1214Bi易切削钢采用:1.C、Mn、S等成分控制优化;2.稳定出钢终点C、降低出钢温度、出钢前渣面喷碳还原等冶炼工艺优化;3.优化冷却工艺、提高结晶器振动频率、降低拉速等连铸工艺优化。降低了成本,改善了铸坯质量,提高了铸坯可轧制性。     

微小型空间相机碳纤维整体式主框架轻量化设计

针对某微小型离轴空间相机结构紧凑、质量轻的设计要求,设计了一个高度轻量化的整体式碳纤维主框架。首先,根据空间相机具体功能的设计指标和光学系统,确定主框架的材料和结构形式,设计出碳纤维整体式主框架的基本构型。接着对铺层厚度参数化优化,并考虑碳纤维复合材料的制造约束,确定了主框架碳纤维铺层的厚度、比例。将参数化优化的结果进行离散化,进行碳纤维铺层顺序的优化,确定了最佳的堆叠次序,完成了碳纤维的铺层优化设计,实现了主框架的轻量化设计,解决了复杂碳纤维零件优化的问题。然后对设计完的碳纤维主框架结构代入整机有限元模型中,进行有限元仿真分析,验证主框架的性能指标。最后,将整机装配完成进行动力学试验,并与有限元分析结果进行对比验证。经过优化,碳纤维主框架的质量为4.5 kg,相机一阶频率为81 Hz,动力学试验得到的相机整机的一阶频率为78 Hz,仿真误差为3.7%,符合仿真结果,进一步说明了设计的合理性以及正确性。本文提出的空间相机碳纤维整体式主框架设计方法对微小型离轴三反式空间相机结构设计以及碳纤维零件的轻量化优化设计具有一定的借鉴意义。     

Standard deviations of composition measurements in atom probe analyses-Part II: 3D atom probe

In a companion paper [F. Danoix, G. Grancher, A. Bostel, D. Blavette, Surf. Interface Anal. this issue (previous paper).], the derivation of variances of the estimates of measured composition, and the underlying hypotheses, have been revisited in the the case of conventional one dimensional (1D) atom probes. In this second paper, we will concentrate on the analytical derivation of the variance when the estimate of composition is obtained from a 3D atom probe. As will be discussed, when the position information is available, compositions can be derived either from constant number of atoms, or from constant volume, blocks. The analytical treatment in the first case is identical to the one developed for conventional 1D instruments, and will not be discussed further in this paper. Conversely, in the second case, the analytical treatment is different, as well as the formula of the variance. In particular, it will be shown that the detection efficiency plays an important role in the determination of the variance.