用光弹性法测定复合型裂纹应力强度因子K_ⅠK_Ⅱ

本文提出了用光弹性法测定复合型裂纹应力强度因子 K_1、K_(1f)的原理和方法.通过对单边上具有不同角度贯穿斜裂纹的矩形截面板进行拉伸和弯曲试验,得到复合型裂纹应力强度因子 K_1、K_(?)的实验值。与数值解比较其误差在8%以内.     

H2S分压对N80油套管钢CO2环境下应力腐蚀开裂的影响

利用U形弯试样浸泡试验和电化学技术研究了N80钢在不同H2S分压的CO2环境下的应力腐蚀开裂(SCC)行为与机理。结果表明：N80油套管钢在CO2-H2S环境下存在一定的应力腐蚀敏感性;随H2S分压的升高,N80钢的腐蚀电流和应力腐蚀敏感性都先增大后减小,H2S分压为0.2MPa时,应力腐蚀敏感性最大;N80钢在CO2-H2S环境下裂纹初期以沿晶开裂(IGSCC)为主,随裂纹扩展转变为沿晶开裂与穿晶开裂混合(TGSCC)的扩展模式,SCC机制为阳极溶解(AD)与氢脆(HE)协同机制。     

含缺陷Q345R钢焊接接头在湿硫化氢环境下的慢应变速率应力腐蚀试验研究

采用缺口棒状试样模拟焊接缺陷表面气孔,通过慢应变速率(SSRT)应力腐蚀试验研究含有该缺陷的Q345R钢焊接接头在湿硫化氢环境中的应力腐蚀行为.结果表明:缺陷试样在拉伸过程中,受到应力集中和硫化氢溶液的协同作用,断裂时间和延伸率较无缺口试样都有明显下降,应力腐蚀敏感性大于无缺陷试样.含缺陷试样在湿硫化氢环境下的应力腐蚀敏感性随硫化氢质量分数的增加而增加,质量分数为200×10-6 H2S环境下断口呈现明显的应力腐蚀断裂特征.     

904L 在甲乙酮生产装置中开裂原因分析

在6 MPa 、155 ℃, pH 值为3～ 7 , 使用氢型树脂催化剂生产甲乙酮的环境中, 对904L 制水帽筛网网丝开裂失效进行了现场调研和腐蚀形态观测。通过904L 合金元素质量分数、腐蚀介质的测定和材料内部夹杂物、网丝残余应力来源、裂纹形态等分析与观察认为网丝开裂属于应力腐蚀开裂。阐述了材料内Ni 、Mo 、Cu 合金元素用量不足、C 含量超标、内部夹杂物多和残余应力高, 以及安装、运输过程中损伤钝化表面是应力腐蚀开裂失效的主要原因。说明了发生应力腐蚀开裂的过程是:催化剂与网丝表面形成缝隙, 缝隙内急速酸化, 当pH值降到904L 去钝化要求的值时, 缝隙内发生钝化膜全面的还原性破坏。构成了由缝隙内金属表面(活性区)-电解质溶液-缝隙外金属表面(钝化区)组成的宏观腐蚀电池。当缝隙内达到一定腐蚀深度时产生应力集中引发裂纹, 发生应力腐蚀开裂。裂纹垂直于网丝圆周方向并沿网丝径向发展, 达到网丝中性面时裂纹消失, 中性面内压应力区没有裂纹。因此, 网丝外表面深度较大的腐蚀坑内看不到裂纹。     

激光预制裂纹槽的断裂分析

进行了单边激光加工裂纹槽试样轴向拉伸试验。试样取自用高碳微合金非调质钢(C70S6)锻造的连杆。分析了激光预制裂纹槽对材料断裂的影响,并与线切割和拉削加工裂纹槽拉伸断裂试样进行了断口分析和断裂载荷的对比。结果表明:采用激光预制裂纹槽试样的断口具有最小的裂尖塑性变形区域,与有相同裂纹槽深度的线切割和拉削加工裂纹槽试样相比,其拉伸断裂载荷分别小20%和30%左右。在试验结果基础上确定了激光加工裂纹槽的等效临界应力强度因子为25.51 MPa.m1/2。本文结果可用于激光预制裂纹槽的连杆裂解载荷参数计算。     

四点弯疲劳试验尺寸效应及MA760疲劳特性研究

考虑到四点弯疲劳试验在疲劳裂纹启裂及早期扩展行为研究中的优点，本文设计并使用了一个四点湾疲劳加载装置。在不同的内跨距／试样厚度比值（d／H）及外跨距／内跨比值（L／d）下，经有限元计算结果表明：纯弯曲段内的表面应力分布并不是均匀的。计算结果有效地解释了本文及有关文献中的实验结果，文中据此给出了四点弯疲劳试样的推荐尺寸。在室温及高温（750℃）下，对锦基超强合金MA760进行四点弯疲劳试验结果表明：该材料具有很好的抗疲劳裂纹启裂能力，但其抗裂纹扩展能力很差；该材料对内部夹杂物的敏感性与环境温度及试样相对厚度密切相关。     

316L不锈钢应力腐蚀敏感性指数计算与回归分析

通过慢应变速率拉伸腐蚀试验(SSRT),计算了316L不锈钢在湿硫化氢环境中的应力腐蚀敏感性指数.在环境因素中,主要考虑了H2S浓度、Cl-浓度、温度和pH值等介质参数单独或交互作用对应力腐蚀敏感性的影响.通过试验数据的逐步回归分析,得到了应力腐蚀敏感性指数随介质参数变化的数学模型,并指出了各介质参数影响的显著性.     

新鮮牛股骨压縮试验的声发射及股骨压縮的力学性质

骨骼压縮时的声发射 1.骨骼声发射机理骨骼受载荷作用将产生应力和应变,在其薄弱处(松质骨、病变骨、滋养动脉血管等)材料发生开裂或破碎,部份变形能以应力波的形式释放出来,被声发射仪测到,这就是声发射。由于变形能的释放,应力从新分布达到新的稳定状态,声发射停止。载荷继续增加,裂纹由稳定状态变成不稳定状态而扩展,或骨骼在另外部位发生新的开裂和破碎,声发射又发生。骨骼声发射事件是骨骼开裂或裂纹扩展及破碎形成的。这在我们所作的牛股骨三点弯曲试验及压缩试验中均观测到并得到证实。 2.Kaiser(卡塞尔)效应问题     

碳化塔阴极保护中氢脆问题的研究

采用阴极充氢恒应力拉伸试验、恒应变三点弯曲试验、吸氢量分析和氢脆系数法研究了低碳钢在磁化氨水介质中的氢脆行为,发现低碳钢在上述介质中的氢脆敏感性很小.当碳化塔在正常负荷下,阴极保护电位不超过-1600mv时,不会发生氢脆破坏.     

环境介质和应变速率对 ABS 拉伸行为的影响

本文研究了ＡＢＳ树脂在环境介质中的慢应变率拉伸行为。结果表明：慢应变率拉伸试验可用于快速评价ＡＢＳ的耐环境应力开裂。     

Hydrogen-induced cracking and its anisotropy of a PZT ferroelectric ceramics

The physical properties of ceramics will be degraded by charging and restored by outgassing at 650℃[1,2]. This means that atomic hydrogen can enter into ceramics through diffusion during charging. The electrical properties of the integrated PZT capacitors will be deteriorated by an-nealing in low pressure hydrogen, and the inter-layer dielectric or top electrode adhesion will be destroyed in high pressure hydrogen[3]. For an aluminum ceramics, hydrogen-induced cracking (HIC) or delayed fail…     

冷轧带肋钢筋焊接网混凝土板抗弯性能试验

为研究冷轧带肋钢筋焊接网混凝土板的抗弯性能,通过拉伸试验,获得了CRB600H与CRB550冷轧带肋钢筋的力学性能指标;进行了32块冷轧带肋钢筋焊接网混凝土板的受弯性能试验,测定了试验板的开裂弯矩、裂缝分布情况、变形发展规律和正截面承载力.研究结果表明:焊点未对CRB600H与CRB550冷轧带肋钢筋的力学性能产生影响;横向钢筋对试验板的开裂弯矩、裂缝间距和裂缝宽度无明显影响.建立了这类板的短期刚度计算公式,与普通混凝土板相比,这类板的抗弯刚度高约10%.根据配置CRB600H和CRB550钢筋网试验板的破坏模式,提出了这两种板正截面承载力的计算方法.     

Hydrogen-enhanced dislocation emission, motion and nucleation of hydrogen-induced cracking for steel

The change in dislocation configuration ahead of a loaded crack tip before and after charging with hydrogen was in situ investigated in TEM using a special constant deflection loading device The results showed that hydrogen could facilitate dislocation emission, multiplication and motion The change in displacement field ahead of a loaded notch tip for a bulk specimen before and after charging with hydrogen was in situ measured by the laser moire interferometer technique. The results showed that hydrogen could enlarge the plastic zone and increase the plastic strain The in situ observation in TEM showed that when hydrogen-enhanced dislocation emission and motion reached a critical condition, a nanocrack of hydrogen-induced cracking ( HIC) would nucleate in the dislocation-free zone (DFZ) or at the main crack tip. The reasons for hydrogen-enhanced dislocation emission, multiplication and motion, and the mechanisms of nucleation of HIC have been discussed     

Hydrogen induced cracking of X80 pipeline steel

The hydrogen-induced cracking (HIC) behavior of X80 pipeline steel was studied by means of electrochemical charging, hydrogen permeation tests, tension test, and scanning electron microscopy (SEM). The experimental results indicate that the increase of charging time and charging current density or the decrease of the solution pH value leads to an increase of the hydrogen content in X80 steel, which plays a key role in the initiation and propagation of HIC. It is found that the majority of macro-inclusions w...     

氢蚀对Cr-Mo钢断裂韧性和裂纹行为的影响

选用经４００℃，２０ＭＰａ，１０５ｈ氢暴露后的Ｃｒ－Ｍｏ钢进行了拉伸试验、疲劳试验和断裂韧性试验。结果表明，氢蚀使Ｃｒ－Ｍｏ钢强度、塑性和断裂韧性均降低，也使断裂机制由韧窝型转变为解理脆性，氢蚀使疲劳裂纹扩展速率增加，门槛值降低。Ｃｒ－Ｍｏ钢氢蚀后，随应力比Ｒ的增加，疲劳裂纹扩展门槛值大幅度降低。     

基于超短栓钉的钢-超薄UHPC组合桥面性能

为了满足对自重敏感的大跨桥梁钢桥面的翻修与加固需求,提出采用超短栓钉作为连接件的钢-超薄UHPC轻型组合桥面结构（简称“新超薄体系”）. 通过钢-超薄UHPC组合板负弯矩试验,研究关键设计参数对超薄UHPC层抗裂性能的影响. 试验结果表明：当UHPC最大裂缝宽度小于0.15 mm时,裂缝宽度的增长近似呈线性,在钢筋屈服以后,裂缝宽度迅速增大;配筋率和钢筋直径对名义开裂应力的影响较大. 基于试验结果,分析已有的裂缝宽度计算公式,确定钢-超薄UHPC组合板裂缝宽度的建议计算公式. 以某特大跨径悬索桥为工程背景,进行整体和局部有限元分析,论证了方案应用于实际工程的可行性. 计算结果表明：钢-超薄UHPC组合桥面的自重与常规60 mm厚的钢桥面铺装基本持平,主缆和吊索内力变化小于3.0%;钢桥面（OSD）各典型疲劳细节的应力幅值降低了10.1%~52.0%,且均小于200万次疲劳强度;UHPC层中最大拉应力为8.4 MPa,远小于试验得到的名义开裂应力.     

TEM Study on Hydrogen-Induced Cracking of Fe3Al Alloy

Hydrogen-induced cracking (HIC) of Fe3AI alloy was studied by in silo transmission electron microscope (TEM). Electron transparent specimens were moaned onto a constant displacement device. Stress was applied to the specimen by using a bolt through the device. The results showed that hydrogen enhanced the dislocation emission and motion in Fe3Al alloy. A dislocation free zone (DFZ) was formed following the dislocation emission. Microcrack initiated in the DFZ or at the main crack tip when the emission reached a critical extension. Hydrogen played an important role in the process of brittle fracture of Fe,AI alloy.     

氢腐蚀分层对换热器筒体承载能力的影响

为了解换热器筒体发生氢腐蚀分层后,其简体局部材料的性能发生的变化及对换热器运行中的承载能力带来的影响,采用化学成分分析、硬度测试、拉伸试验、夏比V口冲击韧性试验等方法对换热器简体材料的性能进行了分析;运用有限元分析方法计算了筒体分层处的应力分布,并探讨了裂纹尖端应力强度冈子的变化情况．研究结果表明：材料化学成分中除Mn元素的含量偏低外,其它元素含量符合国家标准;材料的硬度符合要求,材料的强度极限降低。屈强比上升．韧性明显降低．氢腐蚀分层使换热器简体材料局部劣化,破坏了材料的均匀性和连续性,破坏了简体的薄膜应力状态,产生了较大的局部应力．使换热器简体承载能力下降．     

Experimental and numerical study on loading rate effects of rock-like material specimens containing two unparallel fissures

A series of laboratory experiments and PFC numerical simulations for rock-like material specimens containing two unparallel fissures were carried out.On the basis of experimental and numerical results,the stress-strain curves,mechanical properties,AE events,cracking behavior and energy characteristics were analyzed to reveal the macro-mechanical behavior and meso-mechanism of pre-fissured specimens under different loading rates.Investigated results show that:1)When the loading rate is relatively low,the stress-strain curves show a brittle response.When the loading rate is relatively high,the curve shows a more ductile response.Both of the peak strength and elastic mudulus increase with the increase of loading rate,which can be expressed as power functions.2)Four crack types are identified,i.e.,tensile crack,shear crack,far-field crack and surface spalling.Moreover,the tensile crack,far-field crack and surface spalling are under tensile mechanism,while the shear crack is under shear mechanism.3)The drops of the stress-strain curves all correspond to the crack initiation or coalescence,which is also linked to a sudden increasing in the accumulated micro-crack curve.4)Both of the maximum bond force and energy have the similar trend with the increase of loading rate to peak strength,which indicates that the trend of peak strength can be explained by the meso-mechanics and energy.     

The role of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement of type 304L stainless steel

The role of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement in slow strain rate tensile tests and hydrogen-induced delayed cracking (HIC) in sustained load tests for type 304 L stainless steel was quantitatively studied. The results indicated that hydrogen-induced martensites formed when hydrogen concentration C0 exceeded 30 ppm, and increased with an increase in C0, i.e. M(vol%) =62-82.5exp( - C0/102). The relative plasticity loss caused by the marten-sites increased linearly with increasing amount of the martensites, i.e. Iδ(M),% = 0.45M(vol %) = 27.9-37.1 exp( -C0/102). The plasticity loss caused by atomic hydrogen Iδ(H) increased with an increase in C0 and reached a saturation value Iδ(H)max = 40% when C0 > 100 ppm. Iδ( H) decreased with an increase in strain rate E , i.e. Iδ (H), % = - 21.9 - 9. 9(?), and was zero when (?)≥(?)c = 0.032/ s. HIC under sustained load was due to atomic hydrogen, and the threshold stress intensity for HIC decreased linearly with lnC0, i.e