An analytical model for predicting sheet springback after V-bending

INTRODUCTION As an important manufacturing method, bending has been widely used in modern industries to produce stamping parts such as frames, channels, braces, brackets and other structural parts. The understanding and development of bending mechanics are aimed at achieving two kinds of information which are very important for industrial production. One is to predict springback for dies design and compensation in order to obtain high dimension accuracy of bending parts. The other is to …     

带凸缘圆筒件成形数值模拟

拉深成形中凸、凹模圆角半径一直都是成形的关键,严重影响成形的质量。以板料成形理论和abaqus软件为基础,探讨带凸缘圆筒件拉深成形过程中凸、凹模圆角半径的影响。结果表明：拉深成形过程中,板料最大应力主要集中在凸、凹模圆角半径处;在一定范围内拉深时采用较大的圆角半径,整形以后侧壁的厚度也较大;但凸、凹模圆角半径处的壁厚变化则刚好相反,随着首次拉深圆角半径的增大,壁厚逐渐变薄,甚至出现破裂和折叠;运用有限元数值模拟能很好地预测其成形缺陷,并可对计算参数进行优化。     

Microstructure and corrosion resistance of sputtered TiN coatings on surface of Zr-4 alloy

To improve the oxidation resistance and corrosion resistance of Zr-4 alloy, titanium nitride(TiN) coatings were prepared on the Zr-4 alloy with a TiN ceramic target with different ratios of N_2. Microstructure and high-temperature properties of the TiN coated samples were studied by scanning electron microscopy(SEM), energy dispersive spectrometer(EDS), X-ray diffraction meter(XRD), X-ray photoelectron spectroscopy(XPS), heat treatment furnace and autoclaves, respectively. The x value of the TiN coatings(TiN_x) ranges from 0.96 to 1.33. After the introduction of N_2, TiN coating exhibits a weak(200) plane and a preferred(111) orientation. The coating prepared with an N_2 flow ratio of 15% shows an optimal oxidation resistance in the atmospheric environment at 800 °C. In either 1 200 °C steam environment for one hour, or deionized water at 360 °C and a pressure of 18.6 Mpa for 16 d, the opitimized TiN coated samples have no delamination or spallation; and the gains in the masses of samples are much smaller than Zr-4 alloy. These results demonstrate the effectiveness of the optimized TiN coating as the protective coating on the Zr-4 alloy under extreme conditons.     

斜刃冲裁模的设计

在冲裁高强度材料或厚度大、周边长的工件时，由于冲裁力较大超过冲床负载，常常需要采取措施降低冲裁力。本文介绍一种较为实用的降低冲裁力的方法一斜刀冲裁法，并以温州华成电器公司的机壳落料模为例，介绍了斜刃冲裁模的基本结构设计及斜刃冲裁模冲裁力的计算方法。     

铝型材拉弯成形数值模拟及工艺优化

针对汽车行李架铝型材拉弯成型问题,运用ABAQUS 有限元分析软件,建立型材拉弯成形过程的有限元模型,通过对A6043 铝型材结构件进行拉弯成形正交数值试验,研究预拉量、包覆拉伸量、补拉量和摩擦系数等拉弯成形关键工艺参数对型材回弹量的影响规律,结果表明:在一定拉伸范围内,回弹量随预拉量、包覆拉伸量、补拉量的增大而减少,随摩擦系数的增大先减小后增大?工艺参数中包覆拉伸量对回弹结果的影响最大,达到3%,回弹量趋于稳定?当预拉量为1%、包覆拉伸量为3%、补拉量为1%、摩擦系数为0.1 的工艺参数下,不规则铝型材汽车行李架拉弯成形后的回弹量最小。     

冲裁件单边毛刺产生的原因及防止调整的措施

冲裁模上凸、凹模之间的间隙是影响制件质量的主要因素,然而要保持冲压生产时凸、凹模间隙的均匀,模具的设计、选材、加工和装配各个环节都至关重要。笔者在深入分析了冲压工件时出现单边毛刺的可能情况及原因,研究了凸、凹模间隙均匀的控制方法,并提出了模具使用后间隙变化的调整、修配措施,对冲压生产具有实际指导意义。     

基于PressCAD的FOX面板冲孔模设计

文章简要概述了国内冲压模具设计行业的现状,阐述了模具凸、凹模刃口尺寸确定的新方法,并以FOX面板冲孔模设计为例,介绍了基于PressCAD冲孔模设计的方法、步骤。同时对PressCAD的模具资料设定、模板绘制、模具组立图、模板分离等命令的功能和参数设置方法作了深入探讨.     

Temperature sensor based on a single-mode tapered optical fiber

A temperature sensor is demonstrated and fabricated by coating the single-mode tapered optical fiber with temperature-sensitive silicone rubber. It works on the change of the evanescent fields in the tapered optical fiber. Small changes in the refractive index of coating film greatly influence the power of evanescent fields, which modulate the transmission optical power in the waist region. The range of temperature measured is from 20°C to 70°C. The results show that the temperature sensor has high temperat...     

基于Dynaform横梁回弹分析与模具优化设计

回弹是模具设计中要考虑的关键因素,主要是在试模中予以修正的。本文基于Dynaform,针对匹卡车第一横梁改换材料后工件出现的尺寸变形,进行回弹有限元模拟,分析并讨论有关工艺参数的影响,为实际生产中的模具设计、修改提供切实可行的方案。     

Influence of hydroxypropyl methylcellulose edible coating on fresh-keeping and storability of tomato

The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20°C for up to 18 days. Firmness decreased as storage time increased in all treatments. However, application of HPMC edible coating delayed softening of tomatoes during 18 days of storage at 20°C. At days 7, 13 and 18, the firmness of tomatoes coated with HPMC was significantly (P≦0.05) greater than the firmness of uncoated tomatoes. The study also confirmed that HPMC coatings could significantly (P≦0.05) delay the changes in color of tomatoes stored at 20°C. The ripening of tomatoes from the pink stage to the red stage was successfully retarded. HPMC coating could extend the shelf life of fresh tomatoes. The retardation of the rate of loss of firmness could reduce the economic loss that would result from spoilage by mechanical injury during transportation of tomatoes. Project partly supported by the Centers for Disease Control and Prevention, U.S. Public Health Service     

Cross Cultural Differences in Online Learning Motivation

Globalization and technology are two of the many drivers that impact today’s education, locally and internationally. The purpose of the research study was to identify how online learners in Korea and the US perceived online learning motivation differently and what learner characteristics and cultural orientation affected the online learners’ learning motivation. Major findings revealed that there was a significant difference in learning motivation between the US and Korean online learners. The study also discusses how cultural orientation and learner characteristics affected the learning motivation of online learners for each country.

Différences interculturelles de la motivation de formation en ligne. La globalisation et la technologie représentent deux conducteurs qui ont l’impact sur l’éducation d’aujourd’hui localement et internationalement. Le but de cette étude de recherche était d’identifier comment les étudiants en Corée et aux Etats‐Unis perçoivent la motivation de formation en ligne différemment et comment les caractéristiques des étudiants et leur orientation culturelle affectent leur motivation de formation en ligne. Les conclusions principales révèlent qu’il y a une différence significante concernant la motivation de formation entre les étudiants en ligne des Etats‐Unis et de Corée. L’étude explique également comment l’orientation culturelle et les caractéristiques des étudiants affectent la motivation de formation des étudiants en ligne pour chaque pays.

Unterschiede zwischen verschiedenen Kulturen bei Online‐Lernmotivation. Globalisierung und Technik sind zwei der vielen Antriebe, die die heutige Bildung am Ort und international betreffen. Der Zweck der Forschungsstudie war, herauszufinden, wie Online‐Anfänger in Korea und den USA Online‐Lernmotivation unterschiedlich wahrnehmen, und wie die Anfängermerkmale und die kulturelle Orientierung die Lernmotivation der Online‐Anfänger beeinflussten. Die hauptsächlichen Befunde ergaben, dass es einen signifikanten Unterschied bei der Lernmotivation zwischen den US‐amerikanischen und koreanischen Online‐Anfängern gab. Die Studie erörtert auch, wie kulturelle Orientierung und Persönlichkeitsmerkmale die Lernmotivation von Online‐Lernern in jedem Land beeinflussen.     

Spatial strategies of oriented travel inCallicebus moloch andSaimiri sciureus

The behavior of 9 titi monkeys (Callicebus moloch) and 12 squirrel monkeys (Saimiri sciureus) was examined with respect to three categorical strategies of spatial orientation: direction, turn, and place strategies. Individual animals were initially trained to travel to a fixed location from a constant release point. Following the initial training, each animal was tested by releasing it a number of times from three other release points and analyzing its travel paths. During testing, most individual subjects tended to be highly consistent in their spatial behavior, typically following travel paths consistent with one of the three spatial strategies. No one spatial strategy, however, characterized the behavior of either species.     

精冲过程的数值模拟及工艺参数优化

精冲过程是典型的局部塑形大变形过程，基于其成形特点建立有限元数值仿真模型，对精冲工艺进行弹塑形大变形有限元仿真．模型采用网格重划分方法解决网格畸变情况严重时造成计算终止以及计算结果不收敛的问题，同时引入McClintock韧性断裂准则来预测裂纹出现和扩展的时间及位置．在此基础上，给出了剪切区内应力、应变的分布以及发展趋势，同时针对精冲过程中的工艺参数，如凸凹模间隙、刃口圆角、压边力、反顶力等，对精冲成形面质量的影响加以了分析，给出了工艺参数的影响规律，模拟结果与实际生产情况基本符合，可用于指导工艺参数优化．     

激光毛化板和喷丸板的摩擦行为研究

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形状近似的多件引线插脚级进模具设计

针对形状近似的多件引线插脚分别冲压成形时带来的效率低、成本高的问题,提出了有奈件的共用模设计方法。首先对共用模的前提条件作了界定,然后分析了共用级进模具的设计要点,并对该类型多工位级进模设计的排样、模具结构、主要零部件的设计与制造方法作了阐述。结果表明,这种类型的模具可以达到提高生产效率、节约材料和成本的效果。     

线切割在模具加工中的应用

加工的型腔。半预先加工穿丝孔,凹模穿丝空的切割进行摘要：线切割加工的特点,利用线切割进行典型凸模、凹模的分别加工和配做法,加工凹模型腔时穿丝孔的加工,新型的锥度加工及慢走丝的应用。     

探讨旅游市场营销的重要性

改革开放以后,我国经济得到了较快发展,人民的生活水平也有了很大改善,旅游已经成为我国人民休闲、度假的良好方式.我国的旅游事业蓬勃发展,旅游市场营销是发展旅游事业的重要问题.     

Impact of an educational development programme on teaching practice of academics at a research‐intensive university

Evidence of the impact of educational development (ED) programmes on faculty is often not gathered beyond ascertaining the immediate reactions of participants. This paper reports the results of a study to determine what level of impact an ED programme at a university has had on academics' teaching practice over time. Kirkpatrick's framework provided a useful approach to conceptualise how to examine critically the impact of ED efforts. A series of semi‐structured interviews with 14 programme participants and a subsequent questionnaire survey of 248 participants were undertaken. The programme resulted in high‐level impact when rated according to Kirkpatrick's framework, including changes to individual behaviour and organisational practice, benefits to academics and perceived benefits to their students. Change was reported up to seven years after participation. These results emphasise the role that a well‐designed ED programme can play in enhancing the quality of teaching and assessment practice at a research‐intensive university.

Bepaling van die impak van onderrigontwikkelingsprogramme op dosente word dikwels beperk tot die verkryging van die onmiddellike reaksies van deelnemers eerder as meer omvangryke bewyse. Hierdie artikel rapporteer die resultate van 'n studie wat dit ten doel gehad het om die vlak van impak van 'n onderrigontwikkelingsprogram by 'n universiteit op die onderrigpraktyke van akademici, oor 'n tyd heen, vas te stel. Kirkpatrick se raamwerk het 'n nuttige benadering verskaf vir die konseptualisering van 'n kritiese ondersoek na die impak van onderrigontwikkelingsaksies. 'n Reeks semi‐gestruktureerde onderhoude met 14 programdeelnemers en 'n daaropvolgende vraelysopname van 248 deelnemers is onderneem. Gemeet teen Kirkpatrick se raamwerk, het die program tot hoëvlak impak aanleiding gegee, insluitend veranderinge in individuele optrede, organisatoriese praktyk, voordele vir akademici en oënskynlike voordele vir hulle studente. Veranderinge is tot sewe jaar na deelname gerapporteer. Hierdie resultate beklemtoon die rol wat 'n weldeurdagte onderrigontwikkelingsprogram in die bevordering van onderrig‐ en assesseringspraktyk by 'n navorsingsintensiewe universiteit, kan speel.     

厚壁圆筒热冲击作用下的温度场

针对冲击的瞬时特性，在热冲击问题的边界条件中引入6函数，运用Laplace变换的方法求解了厚壁圆筒内部受热冲击作用时的温度场．探讨了温度场随时间和圆筒内外径比的变化．为研究管式反应器热冲击应力场奠定基础．     

小儿骶管下段形态及应用解剖的研究

应用135具出生后至7岁的小儿尸体,按身长分为三组。其中,75,5厘米以下为0～12个月,76例;95.1厘米以下为1～3岁,36例;116.2厘米以下为3～7岁,23例。对硬膜囊末端以下部位的骶管进行观察和测量。发现骶管弯度随年龄增加而变大.在骶管裂孔中央处,其长轴与皮肤之间的夹角分别为19.9°±2.53°,24.2°±3.29°、27.4°±3.40°.硬膜囊以下部位骶管长度分别为1.51±0.37厘米、2.10±0.22厘米、3.74±0.45厘米.髂嵴连线并骶角的垂直距离分别为3.83±0.91厘米、5.95±0.64厘米,7.32±0.96厘米.骶角至尾骨类的距离分别为1.85±0.40厘米、2.72±0.37厘米、3.71±0.57厘米.以上各数据在组间均有显著性差异(P<0.01)。硬膜囊末端平面的骶管管径和骶管下口的口径均以矢状较横径狭小.