CTOD试验方法与转子材料的延性断裂性能

对国标GB/T 21143—2007和美标ASTM E1820-08a中的CTOD(crack tip opening displacement)计算公式和阻力曲线评定方法进行对比研究,采用柔度法完成汽轮机转子材料Cr2Ni2MoV钢的CTOD试验,并分别根据两个标准对试验结果进行分析。结果表明,GB/T 21143—2007中的CTOD计算公式和钝化线方程存在不合理的表达,对其进行相应修正;根据ASTM E1820-08a得到的CTOD值通常稍低于由GB/T 21143—2007得到的结果;钝化线方程的选取对启裂CTOD临界值的确定影响显著。     

基于试验数据的焊缝试样C*参量估算

针对焊缝和母材蠕变性能不相同的带焊缝CT试样,提出了一个等效均质材料模型,建立了焊缝中心裂纹、焊缝界面裂纹和非对称焊缝裂纹情况下由试验数据确定C*参量的修正式。采用ABAQUS软件进行了带焊缝CT试样C*参量的有限元分析。有限元数值解与修正式的预测值比较表明：与均质材料CT试样相比,低匹配焊缝会导致CT试样的hw因子增大,高匹配焊缝会导致hw因子值降低,采用ASTM E1457提供的公式在低匹配情况下会过低估算C*参量,在高匹配情况下会过高估算C*参量。无论是低匹配(M<1)焊缝还是高匹配(M >1)焊缝,修正后CT试样的C*参量计算式都可给出与有限元解非常接近的估算结果,可用于焊缝蠕变裂纹行为预测。     

铁素体钢的无塑性转变温度落锤试验方法

本标准足根据(84)国标发232号文,参照采用国外先进标准ASTM:E208,在充分分析了国内外大量资枓的基础上结合国内多年来的试验研究和实践经验制定的。该标准适用于铁素体钢无塑性转变温度的测定。基本条款和ASTM:E208是一致的。根据实际工程的需要主要增加了P_4、P_5、和P_6三型辅助试样和焊接接头落锤试样作为附录参考使用。还对某些内容进行了必要的增删和修改。     

某台国产压水堆压力容器锻件材料断裂韧性韧脆转变的参考温度

摘要：采用紧凑拉伸c（T）试样测试了某台国产反应堆压力容器用508-Ⅲ锻件的主曲线参考温度死。为了方便今后在热室中进行辐照材料的断裂韧性试验,专门修改了c（T）试样的前端面设计。有限元分析和采用修改、未经修改的C（T）试样的试验结果均表明,对试样的修改不会影响断裂韧性试验。发现C（T）试样测得的瓦值与前期采用三点弯曲SE（B）试样确定的％值仅相差约1℃。为此详细探讨了ASTME1921标准第1．3和5．7条款有关试样形式对％的影响,试验结果印证了这些条款的阐述,所测得的r,n试验值接近材料的％平均值。     

断裂韧性J_(IC)及J_R阻力曲线的试验研究(二)——对我国几种压力容器用钢及其焊缝区的J_(IC)和J_R曲线测定

本文参考ASTM标准E1152—87、E813—89、R/H/R6修正三版(1986)中附录1及我国GB2038—91等J积分断裂韧性测试标准,对我国几种压力容器用钢及其焊缝区进行了J_(IC)和J_R曲线的测定。由试验结果,对各种材料及其焊缝区的断裂性能进行了比较与分析。最后,对确定断裂韧性J_(IC)的方法进行了讨论。     

国内外金属材料低周疲劳试验标准对比

为评价材料抵抗疲劳失效的能力,必须进行低周疲劳性能试验。目前,国内外都制定了金属材料低周疲劳试验标准。选取国内低周疲劳试验常用标准ASTM E606—2012和GB/T 15248—2008,以及参考ISO国际标准建立的GB/T26077—2010,归纳总结了这些标准之间的差异及特点。发现GB/T 15248—2008和GB/T 26077—2010在试样要求、设备要求、试验程序及试验报告等方面差异不大,建议考虑合并两项标准,形成一个统一的轴向应变控制疲劳试验标准。     

影响夏比冲击试验结果的主要因素

针对影响夏比冲击试验结果准确性的因素,从材料本身、试样的切取和制备、试样的形状尺寸分析、对冲击试验机的要求,以及温度的控制等几个主要因素进行简要的论述。通过试验方法的标准化,各种影响夏比冲击试验结果的因素才得以限定,试验结果也才具有准确性和可比性。     

管螺纹攻丝前钻孔直径的确定

我公司的产品是应用于各种领域的离心泵,大小管路的连接全部使用管螺纹,执行GB/T 73 0 6 1～73 0 6 2—2 0 0 1《55°密封管螺纹》、GB/T 73 0 7—2 0 0 1《55°非密封管螺纹》三项标准。但三项标准中均缺少保证管螺纹尺寸的关键标准———螺纹底孔尺寸标准。为此,我们结合工作实际,参考有关标准,制定了《常用管螺纹攻丝前钻孔用麻花钻直径》的企业标准,在此与大家共同探讨。根据上述三项管螺纹标准,首先计算出内螺纹小径的最大值,再根据GB/T 1 4 3 8—1 996《锥柄麻花钻》,确定合适的钻头规格。例如:GB/T 73 0 6 1中公称直径为1 / …     

921A钢的延性断裂韧性测试研究

以GB/T 21143的柔度法及美国标准ASTM E1820-11推荐规则化数据还原技术为基准,对921A钢试样进行预制疲劳裂纹、收集试验数据、试验数据后处理、有效性评估等几个方面的试验研究。研究结果表明:通过采用规则化数据还原技术以及柔度法对所有试样进行数据处理,两种数据处理方法得到的J—Δa曲线以及启裂韧度JQ均较为接近,且试验预测的最终裂纹长度与光学显微镜实测裂纹长度吻合。说明了采用GB/T 21143可以有效测定高强度塑性材料的延性断裂韧性。     

汽车覆盖件采用变形铝合金材料的研究

阐述为了解决汽车轻量化,选用"ASTM E 6156"变形铝合金材料作为汽车覆盖件材料的研究。运用现代固体力学和当今先进的测试设备,对该材料进行拉伸试验及平面应力断裂韧性测试,并利用透射电镜和扫描电镜对合金的微观组织及断口形貌进行观察。结果表明:时效工艺对6156铝合金的平面应力断裂韧性影响很大,其中T4处理的合金断裂韧性最好。尽管试验证明"平面应力断裂韧性K_c具有各向异性",但在T4时效状态下K_c的T-L取向与L-T取向的数值大小基本一致。最后确定"ASTM E 6156"变形铝合金完全可以满足汽车覆盖件材料的技术要求;同时,"ASTM E 6156"变形铝合薄板仍然可用冷压工艺低成本、高效率生产。     

Correction of constraint loss in fracture toughness measurement of PCVN specimens based on fracture toughness diagram

The aim of this paper is to suggest an approach to generate master curves by using miniature specimens, especially pre-cracked Charpy V-notched (PCVN) specimen, made of SA508 carbon steel. Firstly, fracture toughness diagram is derived from comparing finite element analyses results with the fixed mesh size at crack tip between standard compact tension and PCVN specimens. To compensate the constraint effects from different geometry, further examination based on the fracture toughness diagram was performed. In this context, a scale factor to deal with specimen size effects is proposed by statistically manipulating the numerical analysis data. Finally, the proposed scale factor is applied to calculate reference temperature which affects on the master curve. We expect that the approach can be applicable to compensate the geometrical constraint effects on fracture toughness of SA508 carbon steel when the PCVN specimen is used.     

A533B-1钢韧脆转变区断裂韧度预测的约束评估法

分析A533B-1压力容器钢韧脆转变温度区的断裂韧度、温度以及裂纹尖端约束效应之间的关系.根据实验数据,给出从浅裂纹到深裂纹,不同裂纹长度时单边裂纹弯曲试件(single edge notched bend specimens)的主曲线(mastercurve).用有限元分析相应试件裂纹尖端区域的应力场,采用J-A2双参数方法对裂纹尖端的三轴约束水平进行评估,并给出约束参数A2与主曲线参考温度T0之间的关系.由此,建立A533B-1钢断裂韧度KJC与温度T和约束参数A2之间的关系.为利用实验室数据对工程中不同裂纹构件的断裂评估提供一种经济、可行的方法.     

Recent development in low-constraint fracture toughness testing for structural integrity assessment of pipelines

Fracture toughness measurement is an integral part of structural integrity assessment of pipelines. Traditionally, a single-edge-notched bend (SE(B)) specimen with a deep crack is recommended in many existing pipeline structural integrity assessment procedures. Such a test provides high constraint and therefore conservative fracture toughness results. However, for girth welds in service, defects are usually subjected to primarily tensile loading where the constraint is usually much lower than in the three-point bend case. Moreover, there is increasing use of strain-based design of pipelines that allows applied strains above yield. Low-constraint toughness tests represent more realistic loading conditions for girth weld defects, and the corresponding increased toughness can minimize unnecessary conservatism in assessments. In this review, we present recent developments in low-constraint fracture toughness testing, specifically using single-edge-notched tension specimens, SENT or SE(T). We focus our review on the test procedure development and automation, round-robin test results and some common concerns such as the effect of crack tip, crack size monitoring techniques, and testing at low temperatures. Examples are also given of the integration of fracture toughness data from SE(T) tests into structural integrity assessment.     

Traceable pico-meter level step height metrology

The atomic force microscope (AFM) increasingly being used as a metrology tool in the semiconductor industry where the features measured are at the nanometer level and continue to decrease. Usually the height sensors of the AFM are calibrated using step height specimens ranging from 8 nm to a few μm, however there are no calibration standards at the sub-nanometer level. Recently we have explored the use of stepped silicon single atom specimens as sub-nanometer height calibration artifacts. We have also developed a calibrated atomic force microscope (C-AFM), an AFM with direct traceability to the definition of length to calibrate standards for other AFMs. Earlier, we evaluated the step height of silicon single atomic steps along the (1 1 1) direction (with native oxide) using the C-AFM and obtained a value 304 ± 8 pm (k = 2). To validate the utility of these specimens and the applicability of our analysis technique, we conducted an industry comparison to determine the reproducibility of results obtained when using our procedure. The comparison included AFM vendors and semiconductor device manufacturers. The average standard deviation was 6 pm, and indicates that these specimens and our procedure could be used for sub-nanometer height calibrations.In this paper we will present our evaluation procedure, results of the comparison, and derivation of a value for Si(1 1 1) step height. We will also explore the trends in each participant's data, its effect on the calculation of the mean value, and implications on the reproducibility of our technique. Finally, we will outline the procedure for use of these specimens.     

Simulation of electron energy loss near-edge structure at the Al and N K edges and Al L(23) edge in cubic aluminium nitride

Calculations of electron energy near edge structures (ELNES) are compared with experimental data obtained in a high-resolution transmission electron microscope. This study concerns small precipitates of aluminium nitride in low carbon steel. The ELNES technique allows to clearly establish that these precipitates crystallize in a cubic rather than in a hexagonal crystallographic cell. The influence on simulated spectra of different parameters are investigated: the size of the atomic shell and its relation with the electron inelastic mean free path. We also examine the influence of the core hole and the sensitivity to cell parameters. We particularly examine the Al L(23) near edge structure and features relating to the different transition channels (A(1g), E(g) and T(2g)). Results of a multiple scattering and band structure calculations using ICXANES and WIEN97 codes, respectively, are compared in the region from 0 to 30 eV above the edge onsets. Both calculations are in a rather good agreement.     

材料断裂韧度测试中的厚度效应

在以往的材料断裂韧度测试中，只考虑了对平面应变状态下试件厚度的限制（Ｂ≥２．５（ＫＩＣ／σＳ）２）；而对于非平面应变状态下材料断裂韧度测试中均没有考虑试件厚度的限制。本文从与厚度效应密切相关的应力三轴约束入手，导出了与应力三轴约束ＴＺ相关的裂纹扩展能量释效率Ｇ的表达式，进而得出了相应的测试材料断裂韧度的修正Ｒ曲线法。最后结合３０ＣｒＭｎＳｉＮｉ２Ａ钢断裂韧度的实测结果校验了理论分析结果。     

恒幅载荷16MnR钢疲劳裂纹扩展统计特性分析

通过21个紧凑拉伸试件的疲劳试验，进行16MnR钢疲劳裂纹扩展统计特性研究。研究给定裂纹尺寸条件下疲劳寿命的分布规律，给定寿命条件下裂纹尺寸的分布规律，给定裂纹尺寸下疲劳裂纹扩展速率的分布规律；为16MnR钢疲劳可靠性评估提供基础数据。     

Enamel erosion and prevention efficacy characterized by confocal laser scanning microscope

The aim of this study was to evaluate the erosion‐inhibiting effect of two toothpastes on the development of erosion‐like lesions, by a confocal laser scanning microscope (CLSM). Forty human enamel blocks were divided into five groups (n = 8), in accordance to evaluate the GC MI Paste Plus and Oral B with stannous fluoride, applied as slurries and associated with toothbrush. Specimens were submitted to an erosion challenge from citric acid (0.5%, pH = 2.8), for 5 min, six times a day, alternating in artificial saliva immersions. Reference group was not exposed to treatment. Part of specimens (Groups 02 and 03) was exposed twice daily just to slurries, for 2 min, therefore specimens from Groups 04 and 05 were also abraded, for 30 s. The enamel surfaces were morphological characterized using CLSM images, with mineral loss being measured using the resulting 3D images referenced to an un‐challenged portion of the sample. Step values were compared using the one‐way ANOVA test. CLSM was shown to be a viable, noncontact, and simple technique to characterize eroded surfaces. The statistical difference in the step size was significant between the groups (P = 0.001) and using multiple comparisons a statistically significant protective effect of toothpastes was shown when these were applied as slurries. Although groups submitted to tooth brush showed mineral loss similar to reference control group, due to the damages of abrasion associated. Microsc. Res. Tech. 77:439–445, 2014. © 2014 Wiley Periodicals, Inc.     

A procedure and criterion for bone cement fracture toughness tests

Nowadays, two procedures, based on the recommendation of two American standards (ASTM E399 and ASTM D5045), are used to determine the fracture toughness, KIc, of bone cement. However, there is a lack of knowledge about the equivalence of the two testing methods applied to bone cement. Additionally, in spite of the recommendation of several authors to introduce a rejection criterion for specimens based on the size of defects found in the fracture surface, no data are available about the effect of porosity within the material on the KIc of bone cement. The aims of this study were to verify whether the KIc values calculated for bone cement using the two procedures are comparable and whether macroporosity within the tested samples affects the KIc value of bone cement, and, if so, to establish a rejection criterion for specimen selection. Samples of pure polymethyl methacrylate (PMMA) were tested by both procedures. Additionally, samples showing defects (macroporosity) of different sizes and located in different positions within the specimen were tested. The KIc value determined following the ASTM E399 procedure was 13 per cent lower than that calculated following the ASTM D5045 procedure. In the first series a lower data scatter was observed. Also, the presence of macroporosity on the fracture surface of the specimen affected the KIc value of bone cement. Therefore, the mechanical behaviour of samples was affected by defects within the material. Since it is possible to mould specimens without macroporosity, it seems recommendable to reject specimens with macroporosity on the fracture surface before calculating the KIc value of bone cement.