Prediction of Ductile Fracture Toughness for Neutron-Irradiated Reactor Pressure-Vessel Steels. Part 2

The influence of neutron irradiation on the critical strain in tensile testing of smooth cylindrical specimens and on the local critical strain in ductile fracture of cracked specimens is simulated for 15Kh2MFA reactor pressure-vessel steel. Based on a series of calculations, we have developed an engineering scheme for estimating the irradiation-induced decrease in the upper-shelf level of the KI _c (T ) function.     

Prediction of the Brittle Fracture Toughness of Neutron-Irradiated Reactor Pressure-Vessel Steels. Part 1

The irradiation effect on the temperature dependence of the brittle fracture toughness of reactor pressure-vessel steels is simulated using the probabilistic model for the fracture-toughness prediction, which was proposed by the authors earlier. The paper analyzes the irradiation effect on the parameters controlling the plastic deformation and brittle fracture of reactor pressure-vessel steels. We consider the mechanisms of microcrack nucleation in nonirradiated, irradiated, and post-irradiation-annealed reactor pressure-vessel steels.     

Prediction of the Brittle Fracture Toughness of Neutron-Irradiated Reactor Pressure Vessel Steels. Part 2

We apply the proposed model to study the effect of irradiation on the temperature dependence of brittle fracture toughness of 15Kh2MFA steel. We analyze also the influence of irradiation and the content of phosphorus and copper on the brittle fracture toughness. It is demonstrated that the probabilistic model, which is based on a new formulation of the brittle fracture criterion, allows an adequate prediction of the irradiation effect on the fracture toughness of reactor pressure vessel steels. Alternative models of prediction of fracture toughness are discussed.     

Temperature Dependence of Brittle Fracture Toughness of Reactor Pressure-Vessel Steels upon Ductile Crack Growth

The main mechanisms of brittle fracture upon ductile crack growth are studied on the basis of the probabilistic model of brittle fracture and the deterministic model of ductile fracture, which were put forward by the authors earlier. The investigations are carried out on the reactor pressure-vessel steel 15Kh2NMFAA in the initial and embrittled states. The dependences of brittle-fracture probability on the stress intensity factor and the value of ductile crack growth are calculated for various temperatures. The temperature dependence of brittle fracture toughness in the initial and embrittled states is predicted with and without regard for ductile crack growth. The authors analyze the main factors that govern the above-mentioned relationships. The calculated results are compared to test data for CT-type compact specimens.     

A New Engineering Method for Prediction of Fracture Toughness Temperature Dependence for Pressure-Vessel Steels

An engineering method called Unified Curve, which is similar to the Master Curve approach, is proposed for predicting the temperature dependence of the static fracture toughness for steels of various degrees of embrittlement (up to a very high one). The Unified Curve method has been extensively tested, and a comparison has been made between these two methods. The Master Curve is shown to be a particular case of the Unified Curve method.     

Prediction of Temperature Dependence of Fracture Toughness as a Function of Neutron Fluence for Pressure-Vessel Steels by Using the Unified Curve Method

Using the Unified Curve method as proposed by the authors earlier and a probabilistic model based on the local approach and physical background of the influence of impurities and carbide size on the local strength of material, a method has been elaborated for predicting a variation of the temperature dependence of fracture toughness with neutron fluence. The results calculated by this method are compared to the available experimental data.__________Translated from Problemy Prochnosti, No. 3, pp. 22 – 36, May – June, 2005.     

Modeling of Ductile Crack Growth in Reactor Pressure-Vessel Steels and Determination of JR Curves

A method is presented for predicting JR curves for reactor pressure-vessel steels. The authors propose a procedure for determining the ductile fracture model parameters from the test results for smooth and notched cylindrical specimens. The stress and strain fields at the tip of a stationary and propagating cracks are studied by the finite-element method. The predicted JR curves are compared to the experimental data obtained for the 2T-CT-type specimens of 15Kh2NMFA-A reactor pressure-vessel steel in the initial and embrittled state.     

Fatigue Fracture Toughness of Metals and Alloys. Part 1. Experimental Procedures and Materials and General Principles

The authors summarize the results of studies of fatigue fracture toughness of metals and alloys. Fatigue fracture toughness of materials under plane strain conditions is demonstrated to be much lower than the fracture toughness in static loading. A respective relationship is proposed to allow for this fact. The authors discus the main regularities in transition from stable to unstable fatigue crack propagation and substantiate a model for such transition.     

Q500钢焊接接头断裂韧性K_C与冲击功KV_2的相关性统计规律

采用深缺口宽板拉伸试验测定了4种板厚规格(20 mm、32 mm、40 mm和60 mm)Q500钢焊接接头在不同温度下的断裂韧性KC,对32组断裂韧性值及对应试验温度下的冲击功KV2值的相关性进行了统计分析,结果表明,断裂韧性KC与KV2/t近似呈线性关系,其拟合方程为KC=80.6+7.23·KV2/t。     

管线钢的延性断裂及焊接研究

主要介绍了高压输气管线延性断裂的特征、形成机制，以及我国在高强高韧性管线钢焊接材料、工艺及焊接性方面的一些研究工作。     

非线性路径下板料拉深成形过程中破裂预测

在优选模型参数和简化孔洞形核规律的基础上,采用Gurson-Tvergaard (GT) 多孔材料本构模型分析圆筒件拉深过程;根据金属成形工艺特点,综合考虑拉伸型和剪切型2种不同韧性断裂机制,提出一个统一的韧性断裂准则形式.对于未经过预变形和经过预变形的圆筒件拉深试验和数值模拟进行了比较,结果表明:相对于成形极限图,新的韧性断裂准则可以更加准确地预测非线性路径下圆筒件的拉深破裂.     

Modeling for fracture in materials under long-term static creep loading and neutron irradiation. Part 1. A physico-mechanical model

The paper presents a physico-mechanical model for predicting creep rupture in neutron-irradiated materials. The model is based on the approach whereby damage is described as voids on grain boundaries. The equations for void nucleation and growth which were proposed by the authors earlier are augmented to include neutron irradiation of material. Constitutive equations are derived to describe viscoplastic deformation of material including void propagation. A criterion for plastic stability of a unit cell is employed as a fracture criterion. __________ Translated from Problemy Prochnosti, No. 3, pp. 5–22, May–June, 2006.     

平面应变断裂韧性KIC的研究

综述了平面应变断裂韧性KIC的影响因素及提高断裂韧性的一般措施，并对断裂韧性KIC今后的研究方向进行了论述。     

压水堆核电站反应堆压力容器钢断裂韧性研究进展

反应堆压力容器(RPV)是压水堆核电站最为关键的设备之一,其恶劣的服役环境对RPV钢的材料性能提出了苛刻的要求.综述了RPV钢的低温脆化现象,详细介绍了RPV钢的无延性转变温度、修正无延性转变温度、线弹性断裂韧性要求、ASME曲线法及Master曲线法,最后展望了RPV结构完整性分析评价方法的发展方向.     

奥－贝球铁断裂与疲劳研究的新近进展

奥 -贝球铁具有很强的强度、塑性、韧性、疲劳强度和耐磨性等综合性能 ,应用日益广泛 ,已成为一种重要的工程材料。近年来对其断裂与疲劳的研究发展很快 ,得到不断的深入 ,本文详细介绍了其新近进展。     

Strength and Fracture Toughness of Ceramic Materials for Metal-Ceramic Prosthetic Dentistry

The strength in biaxial flexure and the fracture toughness on indentation of the specimens of ceramic materials for the coverage of metal-ceramic prostheses were studied. The strength was established to be mainly determined by their microstructure and sintering conditions. Comparative studies demonstrated that Ultropaline and VITA OMEGA 900 ceramic compositions exhibited more uniform distribution of leucite microcrystals and higher strength and fracture toughness than Duceram Plus and IPS Classic materials.__________Translated from Problemy Prochnosti, No. 3, pp. 128 – 139, May – June, 2005.     

Determination of the Fracture Toughness of a Low Alloy Steel by the Instrumented Charpy Impact Test

An attempt to establish a non-empirical relationship between the Charpy V-notch energy CVN and the fracture toughness K _Ic is presented. We focus our study on the lower shelf of fracture toughness and on the onset of the ductile-to-brittle transition of a A508 Cl.3 low alloy structural steel. The methodology employed is based on the `local approach'. Brittle cleavage fracture is modelled in terms of the Beremin (1983) model, whereas the ductile crack advance preceding cleavage in the transition region is accounted for with the GTN model (Gurson, 1977; Tvergaard, 1982; Tvergaard and Needleman, 1984. Mechanical testing at different strain rates and temperatures allowed the establishment of the constitutive equations of the material in a rate dependent formulation. Numerous fracture tests on different specimen geometries provided the large data set necessary for statistical evaluation. All specimen types were modelled with finite element analysis. Special consideration was taken in order to handle the dynamic effects in the Charpy impact test in an appropriate way. The fracture toughness could be predicted from Charpy impact test results, on the lower shelf, by applying the `local approach'. In the transition region the parameters of the Beremin model were found to deviate from those established on the lower shelf. Detailed fractographic investigations showed that the nature of `weak spots' inducing cleavage fracture changes with temperature. It is concluded that the Beremin model must be refined in order to be applicable in the ductile-to-brittle transition region.     

Al-Cu-Cr非稳定准晶及其类似相的断裂韧性

用雾化法制得的Al65 Cu20 Cr15准晶粉末与纯铝热压合成复合材料,在热压和热处理状态下复合材料中的颗粒为尺寸在35-160μm范围的Al-Cu-Cr二十面体准晶和十次准晶及其类似相.采用维氏压痕实验技术测试估算了Al-Cu-Cr准晶颗粒的断裂韧性.结果表明,热压状态下的Al-Cu-Cr二十面体准晶材料的断裂韧性约为0.82MPa·m1/2,经退火处理后得到的Al-Cu-Cr十次准晶及其类似相材料的断裂韧性约为1.07MPa·m1/2,与Al-Cu-Cr二十面体准晶材料相比有所提高.在退火和淬火两种状态下Al-Cu-Cr十次准晶及其类似相材料的断裂韧性无明显变化.     

Fatigue Fracture Toughness of Metals and Alloys. Part 2. The Influence of Service and Manufacturing Factors

The authors consider the influence of temperature, load cycle asymmetry, specimen size, plastic prestraining, and material damage in the course of low-cycle loading on the magnitude of fatigue fracture toughness of heat resistant, high-strength chrome-molybdenum and other steels. They analyze the degree of this influence depending on various factors varied in the process of investigation.     

陶瓷材料高温断裂韧性评价

采用四点弯曲实验方法，研究了高温下不同测试方法（ＣＮ法、ＳＥＮＢ法和ＳＥＰＢ法）对工业用重结晶ＳｉＣ陶瓷材料断裂韧性的影响。通过实验发现：在低温下（Ｔ〈８００℃）不同测试方法所获得的ＫＩＣ不同，ＣＮ法测得ＫＩＣ偏大，而ＳＥＰＢ法测得的ＫＩＣ则偏小，同时，三种测试方法获得的ＫＩＣ随温度的升高变化率都不明显。在高温下（Ｔ〉８００℃），不同的测试方法其ＫＩＣ随温度的和蔼同变化趋势不同，ＣＮ法ＫＩＣ随温度的升高而增大，ＳＥＮＢ法ＫＩＣ随温度的升高而减小，ＳＥＰＢ法ＫＩＣ随温度的升高则基本无变化。