二次喷丸诱导应力及变形工程预测方法

为建立二次喷丸的等效分析方法,在单次喷丸诱导应力及饱和度已知的情况下,进行金属零件二次喷丸的诱导应力和变形的工程预测.以单次喷丸的饱和度曲线为分析基础,讨论了二次喷丸饱和度与喷丸时间的变化规律.用正弦函数的形式表达喷丸诱导应力,并建立了零件的平均诱导应力和饱和度之间的关系.结果表明:针对弹丸尺寸不同的二次喷丸过程,进行了基于多弹丸随机喷丸技术的有限元仿真,得到的喷丸诱导应力与理论结果相差5％左右;针对喷丸压力不同的二次喷丸过程,使用标准阿尔门试片进行了喷丸试验,试片变形与理论结果相差3％左右.仿真和试验结果均表明提出的预测方法有效、准确,可较好地预测二次喷丸后零件的残余应力和变形.     

超声波喷丸成形工艺参数优化及弧高值预测

超声波喷丸成形弧高值是多个工艺参数共同作用的结果,成形工艺参数的选择及对弧高值的准确预测成为难点.本文结合正交试验法和有限元分析软件ABAQUS对不同超声波喷丸工艺参数条件下的喷丸成形过程进行数值模拟分析,研究撞针速度、撞针直径、成形轨迹间矩、喷丸区域宽度对带筋板喷丸成形弧高值的影响.对试验结果进行极差分析,探讨了喷丸工艺参数对喷丸成形弧高值的影响程度,得到较优的超声波喷丸成形工艺参数组合方案.利用正交试验得到的数据作为神经网络的训练样本,建立输入为带筋板超声波喷丸成形工艺参数,输出为成形弧高值的BP人工神经网络模型,对喷丸成形弧高值进行预测.通过样本检验该BP网络模型的准确性,实验结果数据与预测数据之间的最大误差为4.69%,从而BP神经网络能够有效代替数值模拟方法预测其弧高值,缩短工艺设计时间,提高设计效率.     

一种测定空化水喷丸工艺中冲击压力场分布规律的方法

空化水喷丸是用于金属材料表面改性的一项新技术,它依靠自身的技术特点和优势,在金属表面改性技术领域中引起许多学者的广泛关注。该工艺中的空化行为涉及高速、高压、多相、相变、湍流、非定常特性等复杂多变情况,对该工艺中的冲击压力场分布规律的求解和测量一直是该领域的难题。本研究使用FUJIFILM压敏纸对空化水喷丸工艺中冲击压力场的分布规律进行实验测定,同时利用X射线衍射仪对该工艺诱导残余应力分布规律进行了实验测定,结果表明利用压敏纸测定空化水喷丸工艺中冲击压力场分布规律的可靠性,同时也表明该工艺可以诱导金属材料的表层形成残余压应力。     

水下平面爆炸冲击作用下空化区域形成及其特征

在水下平面冲击波基本理论基础上,导出在弱冲击波条件下,平面冲击波的空化深度和空化区域高度计算模型.利用LS-DYNA有限元程序对空化区域的密度和速度等特征进行了数值模拟分析.     

由爆炸引起的隧道衬砌与土体相互作用机制的数值模拟分析

为探究爆炸引起的隧道衬砌与土体相互作用机制,基于埋深15 m、含有全饱和颗粒土的单个圆形混凝土线弹性管片组成的隧道模型,对隧道内的管片衬砌与土体在中等幅值的爆破压力脉冲引起的动态变形进行了数值模拟分析.利用有限元程序Abaqus/Standard并结合二维平面应变理论进行建模,同时考虑绝对孔隙压力为零时孔隙水空化,通过精细化单元空间离散,分析了管片衬砌和土体中的应力和变形.研究结果表明:孔隙水空化引起的强非线性对土体性能具有重要影响.具体表现为:孔隙水空化能够显著降低土体的体积模量,并导致大空化带的形成,使得孔隙水从非空化状态向空化状态转变,或从空化状态向非空化状态转变,导致压缩-拉伸过程中土体的应变-应力关系呈现高度非线性,在气蚀区收缩和最终关闭期间,该非线性会在水气混合物溶液中产生高梯度和奇点.     

表面粗糙度对喷丸残余应力场的影响

为定性研究表面粗糙度对喷丸残余应力场的影响,采用余弦曲线模拟靶材粗糙表面,建立喷丸二维有限元模型,采用ABAQUS/EXPLICIT求解器对喷丸过程进行数值模拟,研究了表面粗糙度喷丸残余应力场的影响规律,分析了同一粗糙度下弹丸尺寸和喷射速度对喷丸残余应力场的影响规律,并与表面理想光滑时的情况进行了对比.结果表明,表面粗糙度的增加使残余压应力区变浅变薄,甚至使靶材表面产生残余拉应力,不利于喷丸强化件抗疲劳性能的提高,喷丸件表面应尽可能光滑以改善喷丸效果.     

300M钢多弹丸喷丸强化的有限元模拟

过去,结合喷丸气压和弹丸动能进行数值模拟研究喷丸强化效果的报道不多。采用ABAQUS/Explicit有限元软件对300M钢喷丸强化过程进行数值模拟,在喷丸气压和动能相等的条件下,通过改变弹丸直径确定不同工艺参数对金属靶材进行喷丸处理,对比分析了金属靶材表面残余应力场变化曲线、表面法向位移变化曲线以及表面等效塑性应变。结果表明:不同的喷丸工艺下均可使金属靶材表面获得一定深度的残余压应力场,靶材表面的能残余压应力场强度随弹丸直径增加而增加;对靶材金属施加相同弹丸动能输入时,不同喷丸工艺喷丸效果差距不明显,这为相同喷丸强化要求条件下选取不同喷丸工艺参数提供了理论依据。     

单丸粒撞击金属靶材的有限元分析

本文应用商用有限元软件ABAQUS对单个丸粒撞击金属靶材进行了三维有限元分析,建立模拟弹丸撞击靶材的有限元模型。首先将单个丸粒撞击靶材产生残余应力的模拟结果与Meguid等人用ANSYS软件所模拟的结果进行对比,从而来验证本文模拟结果的可靠性。然后本文系统地研究了不同弹丸参数对于残余应力场分布规律的影响。模拟结果表明,弹丸参数对于喷丸残余应力场分布规律的影响各不相同。但是,无论这些参数如何变化,靶材次表层的最大残余压应力值所处的位置基本保持不变,始终位于靶材表面以下25%dshot处。根据有限元模拟的结果,可对喷丸强化工艺参数进行优化控制,提高喷丸强化的加工工艺水平,以实现更好的喷丸效果。     

诱导轮空化流场数值计算及实验研究

诱导轮是一种经过特殊设计的轴流泵叶轮,在航天运载系统和能源领域中有广泛的应用。诱导轮的抽吸性能很大程度上受流场空化的影响。涡轮泵的外特性参数与诱导轮内空化密切相关,诱导轮内空化的产生及变化是涡轮泵扬程下降的根源所在。以某低温液体火箭发动机诱导轮为研究对象,采用数值计算和可视化试验手段揭示了诱导轮内空化产生和变化的规律,及其与涡轮泵外特性参数的对应关系,从微观角度解释了诱导轮内空化模式与涡轮泵宏观外特性曲线的定量对应关系。对空化流场的数值计算方法和可视化试验台的搭建及测试手段进行了详细的介绍,数值计算结果与可视化试验结果吻合良好,表明实际的数值方法对诱导轮空化流场计算实用可行。     

轴流泵叶顶泄漏涡空化的数值模拟与可视化实验研究

该文以某一等比例缩放模型泵为研究对象,采用修正的SST k-ω湍流模型和空化模型,对额定工况下轴流泵叶顶泄漏涡空化流进行了数值模拟,并与高速摄影结果进行了对比分析。探讨了叶顶区域泄漏涡空化流场结构,揭示了不同空化数下空化发生位置和空泡形态演变过程。研究结果表明,改进的数值模拟方法准确计算了叶顶区域空化流场的流动结构;轴流泵的初生空化为叶顶间隙空化和叶顶泄漏涡空化,随着空化数σ降低,叶顶泄漏涡卷吸区也出现了剪切层空化;在空化数较小工况下,沿着叶片吸力面在轴向形成空泡云,并在叶片尾缘存在周期性的空泡脱落和爆破过程,破坏了流动稳定性,并诱导产生空化噪声。     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.