氢及氢化物对锆合金疲劳裂纹扩展速率的影响及估算

采用紧凑拉伸（CT）试样．研究了不同氢含量的Zr-4及Zr-Sn-Nb合金在室温下疲劳加载裂纹扩展（dα/dN）行为．用扫描电镜观察了断口形貌。结果表明，氢含量对疲劳裂纹扩展速率影响微弱，疲劳断裂受通常的裂纹萌生、稳态扩展和瞬间断裂机制控制。根据疲劳裂纹扩展机理．导出了裂纹扩展门槛值△Kth的关系式．得出了一个描述疲劳裂纹扩展速率油（dα/dN）与材料性能常数之间的关系式，该关系式可用于预测材料的疲劳裂纹扩展速率。用锆合金实验数据对（dα/dN）预测表达式进行验证．结果表明，预测值与实验值吻合较好。     

FSP系统建模与仿真分析

FSP（fission surface power）是美国经过充分研究论证的一种空间堆。为研究FSP系统的瞬态特性,对FSP系统各部件进行建模,并编写相关程序。该程序对系统稳态工况进行仿真,计算结果和稳态设计值符合良好。该程序对反应性引入以及主泵停止后再启动工况进行了仿真,计算结果趋势合理,证明了模型、建模思想以及建模方法的正确性。结果表明反应性引入时功率以及温度参数的振荡和回路之间温度变化快慢不同有关,且主泵停止后再启动的时间间隔越小越好。该程序可为与FSP相类似的反应堆系统的瞬态分析和安全分析提供参考。     

温度对7A60铝合金材料的寿命影响的研究

新一代专用设备中,作为其关键的结构材料7A60铝合金的使用温度可能会提高到T1,为了研究升高温度对铝合金材料寿命的影响,开展了T2(T2T1)温度下铝合金材料的持久强度试验,蠕变试验以及断裂机理的分析研究,得出以下结论:(1)T2温度下铝合金材料10年的持久强度为σ1T20年(99%)=(1.58±0.17)σ0MPa;(2)在温度为T2,总变形量为1.5%时,7A60铝合金材料10年时的蠕变极限为:σ1T2.5%(10年)=1.51σ0MPa;(3)随着使用温度从T0升高到T2,铝合金材料10年时的持久强度和蠕变极限分别降低了18%和12.2%,降到1.41σ0和1.51σ0;(4)在温度为T2,不同应力水平下,铝合金材料的断裂机理相同,均在断口中部呈现台阶状的裂纹扩展区域。     

FSP系统建模与仿真分析

FSP(fission surface power)是美国经过充分研究论证的一种空间堆。为研究FSP系统的瞬态特性,对FSP系统各部件进行建模,并编写相关程序。该程序对系统稳态工况进行仿真,计算结果和稳态设计值符合良好。该程序对反应性引入以及主泵停止后再启动工况进行了仿真,计算结果趋势合理,证明了模型、建模思想以及建模方法的正确性。结果表明反应性引入时功率以及温度参数的振荡和回路之间温度变化快慢不同有关,且主泵停止后再启动的时间间隔越小越好。该程序可为与FSP相类似的反应堆系统的瞬态分析和安全分析提供参考。     

载荷分离法对国产A508-Ⅲ钢断裂韧性的适用性测试

利用载荷分离规则化方法对国产A508-Ⅲ钢1/2T-FFCT试样的断裂韧性进行了测试,得到了国产A508-Ⅲ钢的J-R阻力曲线及断裂韧性JQ值,并采用ASTM E1820及GB/T21143标准对结果进行了判定;同时对其中一个辐照后参考转变温度(T_0)测试的断裂韧性数据采用规则化法进行了处理,研究了载荷分离法对国产A508-Ⅲ钢的断裂韧性测试的适用性。     

5 MW 低温供热堆挤水器作用的数值分析

用三维CFD软件PHOENICS－3．3计算了取消挤水器后5MW低温供热堆（NHR－5）的稳态及非对称运行瞬态工况。分析研究了挤水器的设置在稳态及非对称瞬态工况下对一回路系统的影响，研究结果表明：设立挤水器对对称稳态工况影响不大，对非对称稳态及瞬态工况有较大影响。     

基于W型试样确定A508-Ⅲ钢参考温度T0的方法研究

在我国早期开发的W型试样的基础上,参考ASTM E1921标准,开发了基于W型试样的断裂韧性测试技术,建立了包括断裂韧性计算、数据有效性判定和参考温度T₀计算等在内的数据分析方法。在-100～-40 ℃下开展了国产A508-Ⅲ钢的W型试样和标准1C(T)试样的测试分析和试验数据的有效性评价。结果表明,基于W型试样可得到满足ASTM E1921标准的有效断裂韧性数据,W型试样数据点均在标准1C(T)试样master curve(主曲线)的置信区间内,基于W型试样确定的参考温度T₀与标准1C(T)试样的非常接近,W型试样可成为RPV辐照监督备选试样。     

基于主曲线法的核电主管道材料断裂韧性研究

核电工程的防脆断设计和在役缺陷评价主要应用线弹性断裂力学,并基于材料断裂韧性进行评价。材料断裂韧性需通过试验测定,首先采用落锤试验和V型缺口冲击试验共同确定参考温度,或采用主曲线法确定参考温度,然后将参考温度和材料温度作为变量建立关系式描述材料的断裂韧性。主曲线法能通过较少的试样试验得到材料的断裂韧性,并具有较高的置信度,因此在工程中已得到越来越多的应用。文中采用ASTM E1921标准,应用主曲线法测量了某核电厂主管道材料的参考温度,确定了材料的断裂韧性,并与ASME第Ⅺ卷附录G中的断裂韧性进行比较。结果表明,采用主曲线法得到的材料断裂韧性更高,工程应用中减少了保守裕度,提高了经济性。     

主管道用材中低加载速率下常温断裂性能研究

核电厂主管道在长期服役下,母材及焊接处可能出现裂纹,需要对主管道材料及焊接材料在中低加载速率下的断裂性能进行研究,避免主管道在强地震冲击下可能出现的双端剪切断裂。基于Instron VHS高速材料试验机,开发了一套材料在中低加载速率下的断裂性能测试方法,测量了核电厂主管道材料控氮00Cr17Ni12Mo2及焊接材料OK Tigrod 316L在0.5 m/s加载速率以内的常温断裂性能。结果表明,常温下核电厂主管道材料控氮00Cr17Ni12Mo2在0.5 m/s冲击速率以内并不启裂,焊接材料OK Tigrod 316L在0.5 m/s加载速率以内的断裂韧性并未出现明显的规律性变化。      

快堆燃料组件的子通道分析

开发了ＴＨＡＳ－ＰＣ２子通道分析微机程序，用于计算稳态和瞬态工况下快堆燃料组件的流量、温度和压力等参量分布。对ＥＦＲ燃料组件的稳态和瞬态计算结果如下：堆芯出口平均温度和温长分别为５５７℃和１５７℃，最高包壳表面温度为６０１℃，它发生在中心燃料棒上，最大冷却剂温度为５９３℃；主泵断电二次停堆事故作为瞬态计算，算得的最高冷却剂温度和最高包壳表面温度分别为６３０℃和６３７℃（当ｔ＝２ｓ时），它们都远低于     

Effect of prior crack growth on cleavage fracture of low toughness precracked Charpy specimens

Cleavage fracture of reactor pressure vessel steels in the upper ductile to brittle transition region generally occurs with prior significant ductile crack growth. For low upper shelf materials and using PreCracked Charpy v-notch (PCCv) specimens that can be obtained from conventional surveillance programs, the effect of prior crack growth could be particularly important. In practice, the shape of the Master Curve and the failure distribution could be affected by ductile crack growth. To quantify the effect in practical applications, the effect of prior ductile on cleavage is evaluated on PCCv specimen.The methodology use finite element calculations to grow a ductile crack and infer the brittle failure probability using the local approach to fracture. It is found that for very low upper shelf toughness materials, ductile crack growth enhances the failure probability, induces a steeper failure distribution and affects the shape of the Master Curve. However, for low toughness materials, the enhanced failure probability due to crack growth is compensated by loss of constraint.     

The influence of loading rate on fracture resistance of notched and precracked ISO-V-specimens

Higher loading rates are expected to have a disadvantageous influence on fracture parameters. This opinion derives probably from experience with ductile-cleavage transition whose temperature increases with increasing loading rate. As far as results on the influence of loading rate on crack resistance are published in the literature they show mostly increasing initiation values as well as increasing crack resistance with increasing loading rate.The paper deals with the influence of loading rate on fracture resistance of notched and precracked ISO-V-specimens measured on different materials. The crack resistance of notched specimens has been determined in analogy to that one of the precracked specimens. The influence of loading rate was separately investigated with regard to initiation as well as to tearing modulus.The results demonstrate that the ratio of dynamic to quasi-static values decreases with increasing toughness, the initiation values for dynamic loading may drop at high toughness below those for quasi-static loading, the slope of the crack resistance curve for dynamic loading is mostly larger than for quasi-static loading and the ISO-V-specimens fall well into line with the results of valid tests.     

Dynamic fracture toughness test and master curve method analysis of IAEA JRQ material

IAEA conducted a round-robin fracture test program to test and verify the Master Curve method. One of the materials selected for the round-robin is a A-533B1 plate designated as reference material JRQ. Unnotched Charpy-size specimens were fabricated and distributed to a number of testing laboratories. The three US Owners Groups received specimens for both Charpy impact and three-point bending tests to establish fracture toughness master curves. The B&W Owners Group elected to perform a dynamic fracture toughness test under a high loading rate using the JRQ specimens. The master curve method was successfully applied to numerous fracture toughness data sets of pressure vessel steels. Joyce [Small Specimens Test Technique, ASTM STP 1329, 1997, ASTM] applied this method to high loading rate fracture toughness data for A-515 steel and showed the applicability of this approach to dynamic fracture toughness data. This paper presents the data and the resulting reference temperature shift in the Master Curves from static to dynamic fracture data. Based on earlier PTS analyses performed in 1985, an appropriate T₀ shift value is selected for nuclear power plant applications. This shift in T₀ is compared with the temperature shift between K_Ic and K_Ia curves in ASME Boiler and Pressure Vessel Code.     

Influence of loading rate on the fracture toughness versus temperature curve

This paper presents recent experimental investigations on the influence of loading rate on the fracture toughness K_Ic for different structural steels. The loading rate in terms of increasing in stress intensity factor was changed from quasistatic up to dynamic conditions (

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). The results show significant differences in the amount of temperature shift between K_Ic -T curve obtained after static and dynamic loading for the materials investigated. Based on microscopic fracture criteria for cleavage fracture correlations were made between fracture toughness and yielding behaviour depending on temperature and strain rate. The experimental results were also compared with the predictions given by different models. The most promising results were achieved by a correlation between transition temperature shift in K_Ic caused by dynamic loading and strain rate sensitivity of steels.     

3D finite element and experimental study of the size requirements for measuring toughness on tempered martensitic steels

The fracture properties of the tempered martensitic steel Eurofer97, which is among the main candidates for fusion power plant structural applications, were studied with two sizes of pre-cracked compact specimens (0.35T C(T) and 0.87T C(T)). The fracture toughness behavior was characterized within the temperature range −80 to −40 °C. The ductile-to-brittle transition reference temperature, as defined in the ASTM standard E1921, was around T₀ ≈ −75 °C. At −60 °C, it was found that two sets of toughness data obtained with 0.35T and 0.87T C(T) specimens are not consistent with the size adjustments recommended in the ASTM standard. It was then shown that the underlying reason of this inconsistency is an inappropriate specimen size limit of the ASTM standard for this type of steel. From published fracture toughness data on the tempered martensitic steel F82H steel, similar results were also highlighted. 3D finite elements simulations of the compact specimens were performed to compare the stresses and deformations at the onset of fracture. A local approach model based on the attainment of a critical stress and a critical volume was used to study the constraint loss phenomenon. Within the framework of this model, the strong toughness increase by reducing the specimen size could be satisfactorily explained.     

Influence of loading rate on the crack resistance curve and the initiation temperature

This investigation is concerned with the influence of temperature and loading rate on elastic-plastic fracture in the range of ductile cleavage transition. Side-grooved three point bend specimens of a width of 200 mm and a thickness of 100 mm of two steels of the type 22 NiCrMo 37 of different toughness have been loaded with two deflection rates differing by a factor of 10⁵ in the range between initiation and upper shelf temperature. Due to dynamical loading the transition temperature of these steels has been increased by about 30 K. The slope of the crack resistance curve of the steel of lower toughness was increased considerable due to dynamical loading whereas the slope of the crack resistance curve of the steel of high toughness was increased only negligible. The results suggest that a conservative assessment of dynamically loaded components may be based on quasi-static crack resistance curves. However, in the case of dynamical loading stable crack growth can be supposed only at temperatures being considerable higher than for quasi-static loading.     

Beremin模型预测尺寸效应对A508-3钢断裂韧性的影响

断裂韧性是用于表征反应堆压力容器（RPV）钢脆性状态的重要指标。在开展相关研究时,由于辐照空间小等原因,一般采用小尺寸紧凑拉伸（CT）试样。为掌握CT试样尺寸变化对国产RPV钢断裂韧性测试结果的影响,对国产A508-3钢的不同尺寸CT试样进行了测试分析,采用Beremin模型方法研究了尺寸效应对断裂韧性数据的影响,并建立了不同尺寸CT试样的断裂韧性数据归一化模型（TSM）。结果表明,同一温度下实验测得的断裂韧性值随试样尺寸的减小逐渐增大,不同样品通过标准方法得到的归一化数据存在偏差,本文建立的TSM可有效减小换算数据偏差。     

Fracture assessment of shallow-flaw cruciform beams tested under uniaxial and biaxial loading conditions

A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure–temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J–Q formulation, the Dodds–Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate with the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states.     

Irradiation embrittlement characterization of the EUROFER 97 material

The paper summarizes original results of irradiation embrittlement study of EUROFER 97 material that has been proposed as one candidate of structural materials for future fusion energy systems and GEN IV.Test specimens were manufactured from base metal as well as from weld metal and tested in initial unirradiated condition and also after neutron irradiation.Irradiation embrittlement was characterized by testing of toughness properties at transition temperature region - static fracture toughness and dynamic fracture toughness properties, all in sub-size three-point bend specimens (27 × 4 × 3 mm³). Testing and evaluation was performed in accordance with ASTM and ESIS standards, fracture toughness K_JC and K_Jd data were also evaluated with the “Master curve” approach. Moreover, J-R dependencies were determined and analyzed.The paper compares unirradiated and irradiated properties as well as changes in transition temperature shifts of these material parameters. Discussion about the correlation between static and dynamic properties is also given.Results from irradiation of EUROFER 97 show that this steel - base metal as well as weld metal - is suitable as a structural material for reactor pressure vessels of innovative nuclear systems - fusion energy systems and GEN IV. Transition temperature shifts after neutron irradiation by 2.5 dpa dose show a good agreement in the case of EUROFER 97 base material for both static and dynamic fracture toughness tests. From the results it can be concluded that there is a low sensitivity of weld metal to neutron irradiation embrittlement in comparison with EUROFER 97 base metal.