13SiMNiCrMov钢切口疲劳裂纹萌生门槛值

本文研究在１３ＳｉＭｎＮｉＣｒＭｏＶ结构钢中用尖裂纹的应力强度因子来反映三点弯曲缺口试样的疲劳裂纹萌生规律。当Ｒ＝０．１ｆ＝１００Ｈｚ，试样尺寸Ｂ＊Ｗ＊Ｌ＝１２．５＊２５＊１１７ｍｍ时，缺口名义应力幅的门槛值为△σｔｈ＝３３１５ρ＾０．３５２ＭＰａ，０．５ｍｍ≤ρ≤５ｍｍ，△Ｋｔｈ＝２５０ρ０．３５２ＭＰａｍ门槛值与ρ有关。同时得到缺口裂纹萌生的循环次数Ｎｉ与名义应力幅△σ，缺口曲率半径ρ的定量关     

钠钙玻璃的缺口弯曲强度

钠钙玻璃的缺日弯曲强度与试样的应力集中系数K_t成反比;而缺口根部断裂应力与K_t无关．如弯曲强度服从Weibull分布,其模量m是材料常数,而标度因子σ₀与K_t成反比．如弯曲强度服从正态分布,其平均值及标准差均与K_t成反比,而变异系数为常数．     

开环歧化交联聚双环戊二烯材料的力学性能及断面形态分析

采用钨系双组分催化剂ＷＣｌ６／Ｅｔ２ＡｌＣｌ进行双环戊二烯开环歧化聚合反应制得交联聚双环戊二烯,测定了其拉伸强度,屈服强度、弯曲强度及缺口冲击强度等力学性能。用Ｘ射线衍法研究了聚合物的结晶性,采用扫描电镜研究了聚合物的缺口冲击断面、拉伸断面及脆断面的断裂形态。     

反分析法确定钢纤维水泥砂浆拉应力与裂缝张开位移关系

在数值模拟钢纤维混凝土结构或构件和用基于断裂力学理论的设计方法设计钢纤维混凝土结构或构件时,钢纤维混凝土材料σ-w关系是一个重要的材料参数。该文根据三点弯曲缺口梁的荷载与裂缝张开位移(CMOD)曲线用反分析法确定了钢纤维水泥砂浆的σ-w关系。试验制作了五种不同体积含量的钢纤维水泥砂浆单轴拉伸试件、圆柱体压缩试件和梁试件,钢纤维体积含量分别为0.5%、1.0%、1.5%、2.0%和2.5%。试验发现,当钢纤维体积含量较小时,三点弯曲缺口梁的荷载与裂缝张开位移曲线呈现CMOD软化特性;而当钢纤维体积含量较大时,三点弯曲缺口梁的荷载与裂缝张开位移曲线呈现CMOD强化特性。对有CMOD软化特性的钢纤维水泥砂浆,可用三折线软化模型来模拟钢纤维水泥砂浆的σ-w关系;对有CMOD强化特性的钢纤维水泥砂浆,可用应力跌落-常残余强度模型来拟合。     

水泥基管材力学性能评价方法

水泥基管材已广泛应用于市政、工业、能源等领域,准确的力学性能评价对管材构件的结构性能评估和质量控制至关重要。为解决水泥基管材力学性能难以评价的技术难题,针对缺口环和闭口环两种样品形式,基于材料力学理论推导了缺口环法与闭口环法测量管材弹性模量和弯曲强度的计算公式。利用缺口环法、闭口环法与三点弯曲法分别测得了硫铝酸盐水泥砂浆缺口环试样、闭口环试样与梁试样的弹性模量和弯曲强度。结果表明:三种方法所测得的弹性模量值与弯曲强度值均相近,由此证明缺口环法与闭口环法可以准确有效地测得管材试样的弹性模量和弯曲强度。     

一种工业氧化铝的疲劳特性

利用光滑和缺口试件研究了一种工业氧化铝陶瓷的动疲劳特性，给出了一种预测疲劳强度的简便方法，当加载速率σ〈σｃ时（σ≈２０ＭＰａ）试件的动疲劳强度σＤＦ随σ增大而升高，当σ〉σｃ，趋势出现逆转，对于应力集中系数Ｋ１不同试件，σＤＦ－σ关系曲线相互平行，并可用参量Ｋ１σＤＦ归一化。统计分析显示，疲劳强度有可能遵从正态分布或对正态分布，采用本文定义的等效应力，可获得光滑及接口试件的统一ＳＰＴ（Ｓｔｒｅｎ     

高锰奥氏体低温钢晶界断裂应力的测定

采用７７Ｋ低温四点弯曲缺口试验造成高锰奥氏体低温钢的沿晶界断裂，利用有限元对缺口塑性区应力分布的分析结果，同试样在纯弯曲载荷下断裂时缺口处的应力集中系数Ｑ，进而求出材料的晶界断裂应力。     

钢解理断裂应力的测量和物理意义

用二维平面应变有限元计算了不同尺寸四点弯曲（4PB）缺口试样缺口前的应力分布。通过测量解理起裂源的位置，精确测定了一种钢的细观解理断裂应力和σ1和宏观理解断裂应力σF。结果表明，σF的测量比σf更简单和方便，σf的值可以用σF估计。随试样尺寸的增加，σF和σf的值基本不变，σF的分散性不于σf。稳定的σF和σf的下限值可以用比Griffit-Owen试样尺寸大的试样测得。σf可精确用于细观解理断裂机理的分析，并表征了钢的本质韧性。建议σF作为一个潜在的工程参数，用于钢的理解断裂韧性评价和结构安全设计。     

ISO 9080中一个统计推断问题的探讨

1 问题的提出本文所讨论的是ＩＳＯ/ＤＩＳ 90 80 :1 997(以下简称为ＩＳＯ90 80 )中的一个统计推断问题。ＩＳＯ 90 80为用外推法对塑料管材的长期静液压强度作推定的一个标准。这个标准对塑料压力管的对数寿命关于温度和静液压环应力建立统计回归模型 ,在此基础上 ,根据短时间内的试验数据对回归模型作参数估计 ,进而对塑料管材的长时间寿命进行外推预测。具体地说 ,设ｔ为塑料管材的寿命 (破坏时间 ) ,Ｔ为使用温度 ,σ为静液压环应力 ,ＩＳＯ 90 80中采用下面的模型来刻画ｔ(ｈ) ,Ｔ(Ｋ)和σ(ＭＰａ)之间的关系 :ｌｏｇ10 ｔ=ｃ1 ｃ21Ｔ…     

幂硬化材料缺口试样应力应变场的弹塑性分析及其应用

四点弯曲缺口试样在微观断裂机理研究中经常采用。解理断裂应力的测定和解理断裂判据的建立,均以试样中的应力提升系数 R=σ_(1max)/σ_y 的准确确定和缺口顶端应力场的准确分析为前提。目前这方面的工作普遍利用 Griffiths 等~([1])按线性硬化假定得到的有限元计算结果。但多数结构钢具有幂硬化特性,且不同钢种具有不同的硬化指数 n,     

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.     

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.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to