淬火回火低碳合金钢的疲劳形变与断裂的电镜观察

应用透射电子显微术研究了淬火并400℃和600℃回火钢中疲劳位错结构随循环加载周数的增加所发生的变化。钢中出现具有循环显微硬化与循环显微软化的位错结构形式。前者主要是形成位错缠结,后者主要是粗大疲劳变形带的萌生和扩展,在扩展过程中萌生显微疲劳裂纹。     

试样温度对螺纹钢筋拉伸性能的影响

通过对试样加热后在热状态下进行拉伸，加热 温度下，钢材的屈服强度和抗拉强度有明显变化，在低温范围内随温度升高屈服强度和抗拉强度明显降低。     

A CRITERION FOR INTERGRANULAR BRITTLE FRACTURE OF A LOW ALLOY STEEL

Abstract— The intergranular brittle fracture behaviour of a A533 B Cl 1 steel was investigated by applying a temper embrittlement heat treatment to simulate the presence of local brittle zones (ghost lines) in the as-received material. This heat treatment produced an embrittled material that failed by an intergranular mode at low temperature. An increase in the Charpy transition temperature and a significant decrease in fracture toughness were observed in the embrittled steel as compared to the as-received material. Tensile tests on smooth specimens and on notched bars were carried out to determine the critical stress corresponding to brittle intergranular fracture and to investigate the scatter in the results. It is shown that the mean value of the critical stress seems to be an increasing function of temperature. A statistical model, the Beremin model, initially proposed to describe brittle cleavage fracture was applied to intergranular fracture. Modifications are introduced in this model to take into account the temperature dependence of the critical stress. It is shown that this modified model is able to predict the temperature dependence of fracture toughness and the scatter in the experimental results.     

THE CRACK INITIATION TOUGHNESS FOR BRITTLE FRACTURE OF SUPER DUPLEX STAINLESS STEEL

Abstract— The occurrence of brittle stable crack growth before unstable fracture was demonstrated with the aid of heat-tinting, for a ferritic matrix super duplex stainless steel which had been age-hardened at 475°C. The critical crack tip opening displacement for stable crack growth, i.e. the crack initiation toughness, was measured using the direct-current-potential drop crack monitoring technique. A quantitative model for the effect of temperature and age-hardening on the brittle crack initiation toughness is described.     

热轧中宽钢带拉伸试验测量不确定度分析

根据GUM和JJF1059-1999标准,分析计算了热轧中宽钢带试样拉伸试验中的不确定度行为,得到Urel（Rel）=1．6％,Uerl（Rm）=1．4％,Urel（A）=0．5％。结果表明,热轧中宽钢带试样拉伸试验中不确定度的水平与GB228标准附录J预测水平相当,检测过程受控正常。     

钢绞线拉伸试验的夹具及引伸计的改造应用

钢绞线强度高,缺口敏感性大,拉伸试样长,对它进行拉伸试验,必须具备特制的夹具和大标距引伸计,本文介绍了改造后夹具与引伸计在钢绞线上试验中应用的成功经验.     

35CrMo钢的缺口拉伸试验

通过对３５ＣｒＭｏ钢的三种不同热处理工艺下缺口拉伸及缺口偏斜拉伸试验，表明不同热处理工艺下，材料的缺口敏感性不同，调质热处理较其它两种处理工艺具有更好的使用性能。     

THE EFFECT OF STRAIN RATE ON THE TENSILE AND FRACTURE PROPERTIES OF BS 4360 'A' GRADE SHIP STEEL

Abstract— The results of high rate tensile and compact tension fracture toughness tests conducted on BS 4360 'A' grade ship steel are presented. Tensile results are reported for strain rates within the range 10–^2–10³/s and fracture toughness values at rates of increase of J integral within the range 10^3–10⁶ N/mm/s. The tensile properties of upper yield, lower yield and UTS are shown to be linearly dependent on the logarithm of strain rate whilst fracture toughness is shown to decrease with increasing loading rate prior to approaching a minimum value. The decrease in fracture toughness with increasing test rate is shown to be related to a change in the micro-mechanism of fracture.     

螺纹钢脆断分析

20MnSi螺纹钢筋在弯曲过程中发生断裂.采用化学成分分析、力学性能检测等方法,对断裂钢筋及对其经不同热处理工艺处理后的显微组织进行了对比分析.结果表明,钢中硅和锰含量严重超标,使组织中出现大量的贝氏体组织,铁素体含量降低,造成了钢的塑性下降,导致钢筋在弯曲时发生脆断.     

铸钢拉伸试样的几种断口分析

对塑、韧性低的铸钢拉伸试样断口进行了宏、微观形貌观察，叙述了石状断口、贝壳状断口和结晶状断口的形貌、成因及影响材料塑、韧性的原因。     

FATIGUE CRACK GROWTH LAWS FOR BRITTLE AND DUCTILE MATERIALS INCLUDING THE EFFECTS OF STATIC MODES AND ELASTIC-PLASTIC DEFORMATION

A fatigue crack growth damage accumulation model is used to derive laws for the fatigue crack growth rates of brittle and ductile materials. The damage accumulated during cyclic loading is assumed to be proportional to the cyclic change in the plastic displacement in the crack tip yielded zone. The static mode contribution to the fatigue damage is assumed to be proportional to some power of the crack tip displacement. The laws are applicable in either the small or large scale yielding regimes provided that the stress ratio remains positive. Static modes are assumed to be controlled by the fracture toughness value in brittle materials, and by the gradient of the crack growth resistance curve in ductile materials. In the analysis of ductile materials it is assumed that the crack growth resistance of the material is not significantly altered by fatigue crack growth.
The growth rate equations are expressed in terms of the near field value of the J -integral, i.e. the value which would be calculated from assuming the material deformed in a non-linear elastic manner during the increasing load part of the fatigue cycle. Examples are given of the predictions of the growth law for ductile materials. It is predicted that after the initiation of stable tearing the crack growth rate, when expressed in terms of the cyclic change in the stress intensity factor, depends on both the structural geometry and the degree of crack tip plastic deformation. In both brittle and ductile materials the fatigue crack growth rate is predicted to accelerate as the failure criteria relevant to static crack instability are approached.     

平均应力对45钢P-S-N曲线的影响

根据金属材料试验统计分析方法,求出了45钢棒材的P-S-N曲线,在此基础上对不同平均应力条件下的试验数据进行了可靠性分析比较,探讨了中值S-N曲线和99.9%可靠度S-N曲线的变化规律。研究结果表明,可以恰当地考虑平均应力的影响,便于结构可靠性设计。     

金属材料拉伸试验的缺口效应

通过拉伸试验研究了在缺口效应影响下塑性金属材料试样不同截面处的塑性变形规律及其他常规力学性能指标。结果表明：试验金属材料缺口拉伸中试样的塑性变形主要集中在缺口附近局部区域,同时探讨了增加缺口塑性这一新的性能指标及建立相关试验标准的必要性。     

钢结构构件在高应力集中区脆性破坏倾向性

含高应力集中钢结构构件的厚度是影响其发生脆性破坏的一个重要因素，它的影响是和其应力集中区的复杂应力状态相联系的。本文介绍含缺口的受拉钢构件应力应变关系在不同厚度和缺口曲率半径情况下的变化及其对构件发生脆性破坏可能性的影响。     

X70管线钢焊缝金属弯曲脆断分析

用光学显微镜、扫描电镜和能谱仪分析了X70管线钢焊缝金属弯曲脆断的原因。结果表明，焊缝金属中存在的非金属夹杂物，在低应力作用下形成微裂纹成为裂源，加之焊缝组织中存在大量的M-A结构群，从而发生焊缝金属在室温下的解理断裂。     

一种钢板材料动态拉伸本构方程确定以及试件尺度效应研究

采用数值模拟方法,优化设计了Hopkinson拉伸实验中,QP980CR钢的片状试件尺度。对所设计的试件,在MTS(810材料试验机)上进行了准静态拉伸试验,在Hopkinson拉杆装置上进行了不同应变率及不同温度的动态拉伸试验。由准静态及动态拉伸试验结果,确定了试件材料的J-C型动态拉伸本构方程。基于确定的试件动态拉伸本构方程,采用数值模拟方法,研究了Hopkinson拉伸试验中,试件的形状和尺度对测试结果的影响。     

STATISTICAL MODELLING OF INTERGRANULAR BRITTLE FRACTURE IN A LOW ALLOY STEEL

The intergranular brittle fracture (IBF) behaviour of a low alloy steel 16MND5 (A508 Cl. 3) was investigated. A temper embrittlement heat treatment was applied to the material to simulate the effect of local brittle zones (ghost lines) which can be found in the as-received material condition. An increase in the Charpy V toughness transition temperature and a significant decrease in the fracture toughness measured on CT-type specimens were observed in the embrittled material, as compared to the reference material which was submitted to the same austenitizing and tempering heat treatment, but which was not subjected to the temper embrittlement treatment. Tensile tests on notched specimens were carried out to measure the Weibull stress and scatter in the results. A statistical model, the Beremin model, originally proposed for brittle cleavage fracture was applied to IBF. It is shown that this model is not able to fully account for the results, in particular for the existence of two slopes in a Weibull plot. Systematic fractographic observations showed that the low slope regime in this representation was associated with the existence of MnS inclusions initiating brittle fracture, while the larger slope was related to microstructural defects. Initiation of IBF from MnS inclusions can occur when the material is still elastically deformed while the second population of microstructural defects is active in the plastic regime. A modified statistical model based on the Beremin model and taking into account these specific aspects is proposed in the framework of the weakest link theory. The parameters of this model are identified from test results on notched specimens. It is shown that this model is able to predict the temperature dependence of fracture toughness and the scatter in the experimental results.     

爆轰处理对20CrMo 钢氢脆敏感性的影响

本文研究了爆轰处理对不同组织和强度水平的20CrMo 钢氢脆敏感性的影响。结果发现爆轰处理加高温时效可显著降低钢的氢脆敏感性。对屈服强度分别为830MPa 和620MPa 的均相珠光体组织、爆轰处理对其氢脆敏感性没有或略有影响。爆轰处理显著增加了屈服强度为680MPa,组织为铁素体加珠光体材料的氢脆敏感性系数,同时显著降低它对不可逆氢脆的敏感性系数。     

预应力钢绞线高温力学性能试验研究

该文采用非接触式应变视频测量系统,开展了冷拉1860级钢绞线高温力学性能试验研究。基于试验测试的钢绞线高温应力-应变全过程曲线,建议了预应力钢结构用钢绞线的比例极限、弹性模量、名义屈服强度、断裂强度的高温折减系数以及高温应力-应变函数关系。试验结果表明,高强冷拉钢绞线高温下应力-应变全过程具有显著的应力强化阶段和颈缩阶段,1.25%应变下的高温名义屈服强度适用于高强冷拉钢绞线,钢绞线在高温下的捻度松弛效应对其高温力学性能存在影响。该研究成果进一步完善了预应力张拉钢结构用冷拉高强钢绞线高温下基本力学性能指标体系。     

控轧控冷对低碳Mn-Nb-Cu钢拉伸力学性能的影响

研究了不同终轧温度及轧后冷却速度对低碳Mn-Nb-Cu钢的力学性能(σs，σb和δ5)的影响。研究结果表明，对控轧低碳Mn-Nb-Cu钢的力学性能的影响主要决定于钢的碳当量；随轧后冷却速度的提高，σs和σb提高，δ5降低；在奥氏体未再结晶区进行轧制，终轧温度对铁素体晶粒尺寸的影响较小。