铸造奥氏体不锈钢的疲劳裂纹扩展

用紧凑拉伸试样研究了载荷比、单峰过载和两步高-低幅加载对Z3CN20-09M铸造奥氏体不锈钢疲劳裂纹扩展速率的影响。当应力强度因子范围相同时,疲劳裂纹扩展速率随载荷比的增大而增大。单峰过载使裂纹扩展速率先有短暂的增加后长距离的减速扩展,出现裂纹扩展迟滞现象。两步高-低幅加载时,若两步的最大载荷不同,第二步裂纹扩展也会出现迟滞现象。用两参数模型和Wheeler模型能够预测恒幅载荷和变幅载荷下的疲劳裂纹扩展行为。     

含氮奥氏体钢时效析出Cr2N的数值模拟

研究Fe-24Mn-18Cr-3Ni-0．6N高氮奥氏体钢在1023～1223K温度范围内时效过程中Cr2N的析出规律。根据析出相变热力学和动力学建立Cr2N析出的定量计算的数理模型。利用人工神经网络进行计算和验证,结果是满意的。该数学模型可用于高氮奥氏体钢时效Cr2N析出的计算设计和预测。     

高氮奥氏体钢的CVN低温冲击断裂研究

对Fe-24Mn-13Cr-1Ni-0．44N和Fe-24Mn-18Cr-3Ni-0．62N两种高氮奥氏体不锈钢分别进行了低温冲击断裂的试验研究．研究结果表明：随着氮的质量分数的提高,奥氏体不锈钢的低温冲击韧度快速降低,韧脆转变温度升高,两者的韧脆转变温度分别为140K和210K;高氮奥氏体不锈钢在83K时会产生层状剥离式的脆性断裂;高氮奥氏体不锈钢随温度的降低,断裂模式的变化规律为：拉长或等轴形韧窝→浅坑形韧窝→脆断刻面和韧窝混合型→脆断刻面为主,层状剥离出现．     

Effect of thermal aging on the fatigue crack growth behavior of cast duplex stainless steels

The effect of thermal aging on the fatigue crack growth (FCG) behavior of Z3CN20-09M cast duplex stainless steel with low ferrite content was investigated in this study. The crack surfaces and crack growth paths were analyzed to clarify the FCG mechanisms. The microstructure and micromechanical properties before and after thermal aging were also studied. Spinodal decomposition in the aged ferrite phase led to an increase in the hardness and a decrease in the plastic deformation capacity, whereas the hardness and plastic deformation capacity of the austenite phase were almost unchanged after thermal aging. The aged material exhibited a better FCG resistance than the unaged material in the near-threshold regime because of the increased roughness-induced crack closure associated with the tortuous crack path and rougher fracture surface; however, the tendency was reversed in the Paris regime because of the cleavage fracture in the aged ferrite phases.     

卷边C形截面不锈钢短柱承载力直接强度法

为了研究卷边C形截面不锈钢短柱承载力的计算方法,基于直接强度法,构建了轴心受压和两端受弯矩作用的不锈钢短柱承载力假定模型.结合已开展的38根卷边C形截面不锈钢短柱试验结果,通过参数化有限元分析,对98根轴心受压和94根偏心受压短柱试件进行了数值模拟分析,拟合出适用于卷边C形截面不锈钢短柱承载力的直接强度法计算公式.将拟合公式计算结果与试验结果进行对比分析,结果表明,拟合公式具有较高的精度,可以预测卷边C形截面不锈钢短柱的承载力.     

含氮不锈钢氮气增氮的实验及工艺

通过采用氮气增氮的实验,研究了钢液的化学成分、冶炼温度、表面活性元素和吹氮流量对钢液增氮的影响.研究结果表明:钢中的合金元素尤其是Mn、Cr等元素能够增大钢液氮的溶解度;冶炼温度提高,钢液的增氮速率增大;钢中的氧对钢液的增氮有很大的阻碍;吹氮流量增大则钢液的增氮速率相应增大.同时对含氮不锈钢采用吹入氮气增氮工艺进行了探讨,为含氮不锈钢的生产提供了参考.     

Fabrication of high nitrogen austenitic stainless steels with excellent mechanical and pitting corrosion properties

A series of high nitrogen austenitic stainless steels were successfully developed with a pressurized electroslag remelting furnace. Nitride additives and deoxidizer were packed into the stainless steel pipes, and then the stainless steel pipes were welded on the surface of an electrode with low nitrogen content to prepare a compound electrode. Using Si₃N₄ as a nitrogen alloying source, the silicon contents in the ingots were prone to be out of the specification range, the electric current fluctuated greatly and the surface qualities of the ingots were poor. The surface qualities of the ingots were improved with FeCrN as a nitrogen alloying source. The sound and compact macrostructure ingot with the maximum nitrogen content of 1.21wt% can be obtained. The 18Cr18Mn2Mo0.9N high nitrogen austenitic stainless steel exhibits high strength and good ductility at room temperature. The steel shows typical ductile-brittle transition behavior and excellent pitting corrosion resistance properties.     

充填体强度设计知识库模型

综合分析了国内外充填矿山的工程实践资料,并用分形维数来表征充填材料的级配特性,将矿体埋藏深度、矿体长度、矿体厚度、充填体暴露高度、充填体暴露面积及充填材料分形维数6个因素作为输入,充填体设计强度作为输出,建立了充填体强度设计的神经网络知识库模型.为了避免神经网络易陷入局部极小以及收敛速度慢等缺陷,采用遗传算法对神经网络进行优化,提高了神经网络学习效率.通过对知识库模型进行检验,发现其具有很高的计算精度.研究表明,随着开采深度的增大,充填体设计强度必须随之增大;充填体侧向暴露面积越大,所要求的充填体强度越高.将该模型应用于三山岛金矿,设计了合理的充填体强度.     

Effect of microstructure on the low temperature toughness of high strength pipeline steels

Microstructure observations and drop-weight tear test were performed to study the microstructures and mechanical properties of two kinds of industrial X70 and two kinds of industrial X80 grade pipeline steels. The effective grain size and the fraction of high angle grain boundaries in the pipeline steels were investigated by electron backscatter diffraction analysis. It is found that the low temperature toughness of the pipeline steels depends not only on the effective grain size, but also on other microstructural factors such as martensite-austenite (MA) constituents and precipitates. The morphology and size of MA constituents significantly affect the mechanical properties of the pipeline steels. Nubby MA constituents with large size have significant negative effects on the toughness, while smaller granular MA constituents have less harmful effects. Similarly, larger Ti-rich nitrides with sharp corners have a strongly negative effect on the toughness, while fine, spherical Nb-rich carbides have a less deleterious effect. The low temperature toughness of the steels is independent of the fraction of high angle grain boundaries.     

霉菌对超高强钢腐蚀行为的影响

采用扫描 Kelvin 探针测试技术,研究了300M 钢、Aermet100钢与超高强不锈钢在黄曲霉、黑曲霉、球毛壳霉、绳状青霉和杂色曲霉组成的混合霉菌菌种作用下的腐蚀行为.通过扫描电镜结合能谱分析对霉菌在三种超高强钢上的生长进行了观察和分析.300M 钢试样上霉菌呈现分散式堆积生长,数量逐渐增加;Aermet100钢试样上霉菌呈现分散式单个生长方式,数量逐渐增加;超高强不锈钢上霉菌呈现放射式网状生长方式,数量急剧增加,在钢表面形成一层生物膜.霉菌实验后,三种超高强钢表面都发生一定的腐蚀.300M 钢腐蚀最严重,蚀坑宽而浅;Aermet100钢次之,蚀坑窄而深;超高强不锈钢的耐蚀性最好.扫描 Kelvin 探针测试结果表明,霉菌一定程度上能促进300M 钢和 Aermet100钢的腐蚀,而对超高强度不锈钢的腐蚀行为有一定抑制作用.     

Influence of parameters on the microstructure of a duplex stainless steel joint welded by a GMAW welding process

Duplex stainless steels (DSSs) are widely used in industry for their desirable properties. Any fusion welding technique modifies the microstructure and, consequently, the properties of the material. This paper presents a parametric study of the variables that determine the energy contribution (current, voltage and welding speed) and the structural modifications produced during gas metal arc welding. The analysis comprises metallographic study, phase balance, dimensioning of the weld beads and tensile and hardness tests. The influence of the variables studied on the thermal cycles obtained (temperatures reached and cooling rate) was determined by using a finite element model. The results showed that, in addition to the indicated parameters, the parameter power transfer per volume (W/m³) and the geometry in the bead must be controlled due to their influence on the heat flow distribution and phase balance.     

工艺参数对凝胶注模成型不锈钢坯体强度和烧结密度的影响

为了制备高坯体强度和烧结密度的凝胶注模成型不锈钢制件,研究了凝胶注模工艺参数包括预混液单体含量和单体/交联剂比例、浆料固相含量及引发剂加入量等对坯体抗弯强度及烧结体密度的影响规律.结果表明,对于316L不锈钢的凝胶注模成型,可同时获得较好的坯体强度和烧结密度的工艺条件为:预混液单体质量分数18%～22%,单体/交联剂比例90∶1～240∶1;浆料固相体积分数52%～55%;引发剂用量约为单体质量的0.8%～1.4%.最终获得坯体强度高于30.0MPa、烧结密度高于97%的复杂形状烧结不锈钢零件,其烧结体力学性能略低于粉末注射成型时的性能,但远高于美国MPIF标准.     

High temperature strength and ductility of the (C+N) strengthening Fe-Cr-Mn(W,V) steels

Fe-Cr-Mn(W, V) austenite steels used as low radioactive structural materials in fusion reactor have been investigated. The resultsshow that the high temperature strength and the creep fracture life of Fe-Cr-Mn(W, V) steels can be effectively improved through (C+N) complex-strengthening, so can be the high temperature ductility. The strength and ductility of the steels are superior to that of SUS316 steels and JPCAS below 673K. The relationship between strength, ductility andthe formation temperature is related to the evolution of deformation microstructure. The fracture and microstructure observation above 673Kindicates that the main way to further improve ductility at high temperature is the control of carbide coarsening at the grain boundaries.     

圆柱壳体的强度优化设计理论研究

对在任意轴对称分布荷载作用下体积保持常数的变厚度圆柱壳的强度优化设计问题进行了研究 .采用阶梯折算法 ,用传递矩阵导出了变厚度圆柱壳的初参数解的显式表达式 .根据 Huber-Mises- Hencky强度准则 ,将变厚度圆柱壳的强度优化转化为极小化当量应力的非线性规划问题 ,并采用投影梯度法建立了问题的优化方法 .对几个典型问题进行了计算分析 ,取得了较好的结果 .     

多裂纹结构剩余强度的均匀设计研究

多部位损伤会造成工程结构剩余强度的大幅下降。为了更好地探索不同因素对工程结构剩余强度的影响能力,以均匀设计的实验设计和有限元分析方法,探索了连通距离、宽度和深度等三个因素对于结构剩余强度的影响,并用非线性拟合得到经验公式。研究结果表明:连通距离在10~20 mm范围内,剩余强度与连通距离成线性关系,在裂纹宽度10 mm、裂纹深度0.75 mm、连通距离从10 mm增大到20 mm时,剩余强度从352.8 MPa增加到388.6 MPa;剩余强度与裂纹宽度在5~10mm的范围内成线性关系,在连通距离20 mm、裂纹深度0.75 mm、裂纹宽度从5 mm增加到10 mm的过程中,剩余强度从360.8 MPa增加到388.6 MPa;剩余强度与裂纹深度成四次多项式关系,裂纹深度从0.25 mm增加到0.75 mm的过程中,剩余强度的降幅大于40 MPa,其影响能力明显大于前两者。研究结果对于工程结构剩余强度的评估提供了有价值的参考。     

稳健设计在梁柱外节点抗剪强度分析中的应用

介绍了稳健设计法的基本内容、一般步骤及其在梁柱外节点抗剪强度分析中的应用,引入信噪比。用软化桁架模型分析地震作用下钢筋混凝土梁柱外节点抗剪强度,并用稳健设计对影响钢筋混凝土梁柱外节点抗剪强度的因素进行分析,得出了各种影响因素的重要程度,其中竖向箍筋强度对外节点扰剪强度影响最为明显,混凝土标准抗压强度和水平箍筋屈服强度次之。为以后设计和施工提供了理论依据。     

二维流动模型用于喷射器关键结构设计分析

在试验验证了喷射器二维可压缩流动模型可行性和计算准确性的基础上,应用该模型对喷射器结构与性能和流场之间的变化关系进行了研究．试验结果表明,二维流动模型在没有引入经验参数的条件下,能够较好地预测喷射器的工作特性和性能指标．喷射器内流场直观地显示了混合室截面大小对喷射器性能的影响过程．     

利用Box-Behnken实验设计研究化学外加剂组分对水泥砂浆强度的影响

利用Box-Behnken实验设计(BBD)方法研究三乙醇胺、氯盐、还原糖和二元醇4种化学组分对水泥砂浆各养护龄期抗压强度的影响。通过Box-Behnken设计得出能反映化学组分掺量与水泥砂浆强度关系的二次方程。利用实验设计得到的帕雷托图对各化学组分影响水泥砂浆强度提升的有效性进行排序。结果表明:三乙醇胺在水泥砂浆养护3 d前对强度的贡献强于氯盐,而对于28 d强度贡献低于氯盐。还原糖的作用主要体现在3 d前,二元醇及其与三乙醇胺和氯盐的交互作用能显著提高水泥砂浆的28 d强度。     

联接螺栓静强度的模糊可靠性设计研究

应用信息熵理论,将联接螺栓的模糊静强度和模糊载荷分别等效为随机静强度和随机载荷,按联接螺栓安全等级确定其静强度的可靠指标,建立按可靠指标进行联接螺栓静强度设计的方法,得到联接螺栓静强度的可靠性安全系数。研究表明:1)对于安全等级为一般、比较重要和重要的联接螺栓,其屈服强度的可靠指标分别为0.815,1.920和3.819,抗拉强度的可靠指标分别为3.740,4.729和6.828;2)基于满足联接螺栓静强度的可靠指标,对于安全等级为一般、比较重要和重要的联接螺栓,在静载荷时,螺栓屈服强度的最小可靠性安全系数分别为1.10,1.25和1.45,抗拉强度的最小可靠性安全系数分别为1.35,1.50和1.75;在变载荷时,螺栓屈服强度的最小可靠性安全系数分别为1.15,1.35和1.60,抗拉强度的最小可靠性安全系数分别为1.60,1.80和2.20。     

螺旋滚筒选煤机滚圈强度设计方法的研究

介绍了螺旋滚筒选煤机的基本结构和滚圈的作用 ,分析了滚圈的受力 ,建立了力学模型 ,利用求解静不定问题的方法算出特殊截面的内力 ,进而算出滚圈的最大弯矩和截面尺 ,为滚圈设计提供了一种理论方法