含银纹的高聚物裂纹扩展

根据已有的实验结果,考虑银纹损伤演变规律,假设裂尖银纹模型,导出Ⅰ型裂纹准静态下裂纹尖端银纹增长的微分方向和稳态扩展的方程,研究了裂纹长度及其扩展速度随时间的演变规律,初步分析了银纹损伤区平均,应力的变化,对含Ⅰ型裂纹ＰＭＭＡ的寿命进行了探讨。     

脆性高聚物的银纹化增韧设计

银纹化是脆性高聚物的一种典型的非线性变形方式。银纹在其引发、生长和断裂过程中消耗大量能量 ,对高聚物的增韧设计十分重要。考虑银纹细观结构特征的银纹生长和断裂规律是研究银纹增韧机制的核心内容。根据国内外近期的若干研究进展 ,基于对承载高聚物中的银纹断裂及其与裂纹扩展的相互作用等问题的分析 ,从理论上探讨将材料断裂韧性与其微观控制参数 (如分子量 ,缠结密度等 )联系起来 ,寻求对脆性高聚物进行微观增韧设计的途径和方法     

高聚物银纹断裂的研究现状

银纹化是高聚物的一种非线性变形方式，对高聚物的增韧设计十分重要。考虑银纹细观结构特征的银纹生长和断裂规律是研究银纹增韧机制的核心内容。结合国内外最新的研究进展，对承载高聚物中的银纹断裂及其与裂纹扩展的相互作用等问题作了较全面的总结和分析，并对今后的研究重点和趋势作了简要展望。     

聚丙烯内聚区银纹断裂时间的预测

文中拟定的聚丙烯(PP)银纹断裂分离标准是根据银纹拉伸产生变形热引起内聚区熔融层的形成和增厚提出的。内聚区分离的数值模拟是基于活性层附近的银纹区和本体区内的非线性热传导和热对流,并伴随均一轴向银纹的力学拉伸。聚丙烯银纹断裂时间的预测是在假定常银纹增厚速率和常内聚力的条件下实现的。研究表明,活性层温度相同时PP材料银纹区和本体区的温度分布不同,前者的热传导较后者快得多。随着应力或拉伸速率增大,无论是银纹区还是本体区的温度分布均呈减小的趋势。随着应力增加或银纹增厚速率的增加,PP的银纹断裂时间呈递减的趋势。实验结果的比对证实了通过热反内聚模型的数值模拟程序可预测聚丙烯的银纹断裂时间。     

脆性高聚物的银纹化增韧设计

银纹化是脆性高聚物的一种典型的非线性变形方式。银纹在其引发、生长和断裂过程中消耗大量能量，对高聚物的增韧设计十分重要。考虑银纹细观结构特征的银纹生长和断裂规律是研究银纹增韧机制的核心内容。根据国内外近期的若干进展，基于对承载高聚物中的银纹断裂及其与裂纹扩展的相互作用等问题的分析，从理论上探讨将材料断裂韧性与其微观控制参数（如分子量，缠结密度等）联系起来，寻求脆性高聚物进行微观增韧设计的途径和方法。     

用单轴拉伸实验研究HIPS的银纹增韧现象

高抗冲聚苯乙烯 (HIPS)是通过颗粒填充进行改性以提高其力学性能的工程塑料 ,通过单轴拉伸实验对其银纹损伤及增韧现象做初步探讨 ,发现银纹增韧机理是橡胶增韧中主导因素 ,分析得到受拉HIPS的弹塑性损伤本构方程的一般形式 .     

防辐射含钆有机玻璃的断裂韧性研究

利用紧凑拉伸实验方法,测定含钆有机玻璃的平面应变断裂韧性KIC,并对紧凑拉伸试样的断面形貌进行分析。利用环境扫描电子显微镜原位拉伸测试技术,分析含钆有机玻璃在拉伸应力下的断裂过程,认为用裂尖银纹-裂纹模型和次级破裂模型分别解释含钆有机玻璃的慢速裂纹扩展和快速裂纹扩展过程是合适的。     

用应变片法确定混凝土动态起裂时间的研究

在混凝土等准脆性材料的动态起裂韧度K_(1d)测试中,准确确定试件裂尖的起裂时间是测试工作的关键。采用分离式霍普金森压杆系统,对圆孔裂纹平台巴西圆盘混凝土试件进行动态径向冲击试验,通过在裂尖粘贴应变片的方法来确定起裂时间。讨论了应变片在裂纹尖端的粘贴位置、粘贴方向等因素对起裂时间测试值的影响,结果表明裂尖应变片的最佳粘贴方式是:在裂纹延长线上或在裂尖并与裂纹垂直的线上,都距离裂尖3 mm左右,且粘贴方向与裂纹延长线垂直。给出了考虑贴片位置和试件厚度的起裂时间计算公式。     

基于材料低周疲劳的裂纹扩展预测模型

该文基于疲劳裂纹尖端循环应力-应变场, 定义了基于应变幅的平均单位循环损伤参量D, 并引入Miner累积损伤率, 从而从理论上建立起材料低周疲劳性能和疲劳裂纹扩展行为之间的联系。以裂尖扩展方向上的单调塑性区尺寸作为疲劳过程区大小, 并提出了基于弹塑性应变疲劳累积损伤的疲劳裂纹扩展预测模型。模型改进了前人提出的疲劳裂纹扩展预测模型, 考虑了单调塑性区内所有材料的弹塑性应变疲劳损伤贡献;模型中参数均有物理意义, 不需要人为调试。基于完成的Cr2Ni2MoV 材料的低周疲劳结果所建立的该文新模型对该材料裂纹扩展速率的预测结果与实验结果有良好一致性。并且, 借助手册数据, 在TC4钛合金材料上进一步得到了验证。     

动态界面裂纹扩展行为的分形描述

本文以无限弹性体中具有自相似分形几何结构的含裂纹界面研究对象，借助分形几何概念对分形界面裂纹的动态扩展行为即对界面裂尖应力场，界面裂纹扩展速度，加速度，裂尖复合应力强度因子，动态能量释放率，双材料不匹配参数，界面裂纹的分维以及它们之间的关系进行描述，给出了界面裂纹扩展行为的分形动力学模式。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

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.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

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.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

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.