A CTOD equation based on the rigid rotational factor with the consideration of crack tip blunting due to strain hardening for SEN(B)

Crack tip opening displacement (CTOD) from national and international standards was shown to give different values. This paper investigates the feasibility of CTOD determined based on the concept of rigid rotational factor in single‐edge notched bend (SENB) specimens. Based on validated modelling methods, finite element (FE) models were simulated for crack ratios 0.3 ≤ a₀/W ≤ 0.7 and yield‐to‐tensile ratio 0.44 ≤ σ_ys/σ_uts ≤ 0.98. This covers cases of shallow to deeply cracked specimens and a wide range of strain hardening properties. CTOD obtained from the FE models was used as the basis of a newly implemented strain hardening corrected rotational factor, which considers the effects of crack tip blunting due to strain hardening, r_{p sh}. An improved equation considering strain hardening was implemented based on the r_{p sh}. The equation gives accurate estimation of CTOD from the FE models compared with the equation from BS 7448‐1, ASTM E1820, and WES 1180.     

Modified transformation formulae between fracture toughness and CTOD of ductile metals considering pre-deformation effects

Strengthening action and degrading action are proposed to describe influences of plastic deformation on fracture toughness in ductile metals. Strengthening effect represents the shield operation of dislocation from crack and degrading effect displays the emergence of damage. In order to demonstrate two effects, the existing transform equation between fracture toughness and crack-tip opening displacement is modified based on a novel damage variable. The modified transform formulae can help to find the maximum of fracture toughness for metals and keep safer performance for structural components.     

铁路钢轨钢材三点弯曲试样的弹塑性有限元分析

对铁路钢轨钢材标准三点弯曲试样的弹塑性断裂性能进行了系统研究与分析。通过有限元计算结果与试验结果进行对比,验证了钢轨钢材的脆性破坏特征。采用普通单元和奇异单元的网格计算应力和位移进行了分析。并对裂纹尖端CTOD值进行了计算分析,CTOD值沿试样厚度方向的变化很小,裂纹尖端始终处于三向拉伸应力状态。而三向拉应力状态将使裂纹尖端处的塑性变形受到很大限制,破坏时的塑性变形很小,更容易发生脆性破坏。     

9％Ni钢焊接技术研究

以典型的9%Ni钢——ASTM A553TYPEⅠ钢板为研究对象,分析其焊接特点,采用SMAW、SAW、GTAW三种焊接方法进行了试板焊接试验,并采用V型缺口-196℃夏比冲击试验和-163℃ CTOD试验,辅助以金相试验进行了焊接接头低温韧性分析,焊接接头试验表明,其低温冲击功和焊缝CTOD值均优于相关的国际标准。     

低温下结构钢材裂纹尖端张开位移的变化规律

裂纹尖端张开位移 (CTOD)是材料断裂分析的重要判据指标。在GB T 2 35 8- 94金属材料裂纹尖端张开位移试验方法中 ,根据加载曲线的不同形式可以获得 5种不同的特征CTOD值。随着温度的降低 ,结构钢材的韧性降低 ,试验曲线的形状变化 ,可测得的特征CTOD值也不相同。本文在三种结构钢材低温下裂纹尖端张开位移试验的基础上 ,分析了各特征CTOD值随温度降低的变化规律     

强度匹配对焊接钢管断裂韧性影响的有限元分析

为了研究焊接过程中强度匹配对焊接接头断裂韧性的影响,以弹塑性断裂力学理论为基础,基于细观塑性损伤模型,应用ABAQUS软件对大范围屈服条件下的全周向内裂纹管采用轴对称模型及基于小范围屈服的修正边界层模型（MBL）分别进行有限元模拟分析计算。研究结果表明:高配且匹配系数越高,焊接接头的断裂韧性及阻力曲线越高;随匹配系数增加,失配约束M减小,管子的断裂韧性增大;不同强度匹配引起的失配约束差异随裂纹扩展而增大。     

高强船体钢双丝埋弧焊焊接接头CTOD试验研究

根据GB／T2358—1994标准,对16ram厚的高强船体钢焊接接头的焊缝中心-40℃的裂纹尖端张开位移（CTOD）进行测试,绝大部分试样的断裂韧性值是有效合格的,其CTOD值大于0．15mm,符合DNV验收标准。试验结果表明,在给定的双丝埋弧焊接工艺下,该钢种焊缝低温韧性好。该钢种中等厚度双丝埋弧焊焊接接头可以在不进行焊后热处理的情况下使用。     

电子束焊GH4169合金高温裂纹尖端张开位移试验

根据国标GB／T2358-94,对GH4169合金电子束焊接接头的高温（650℃）裂纹尖端张开位移（CTOD）进行了测试。取SE（B）试样进行三点弯曲试验,然后由所得到的650℃下母材和焊缝的P-V曲线来计算CTOD值,并对试验结果进行了讨论和总结。     

CTOD WITH SLOW STABLE CRACK GROWTH: ANALYSIS OF THE ELASTIC COMPONENT

Abstract— The errors made during calculations for the "elastic" component of CTOD, δ_e, under slow stable crack growth conditions are analyzed and a model that considers this situation is proposed. Some examples are shown in which important errors occur in the CTOD value as a consequence of not having considered slow stable crack growth. This analysis complements previous work where an adaptation of the Plastic Hinge Model was made in order to consider corrections in the plastic component of CTOD due to rotation and stable crack growth.
The errors in Schwalbe's CTOD term, δ₅, which relate to a lack of alignment to the average crack front are also studied. Since the absolute value of this inexactitude is not known, bounds are set to this error.