梯形波纹腹板焊接梁疲劳寿命分析

针对梯形波纹腹板焊接梁结构,分别基于不同的表征应力方法(名义应力法、热点应力法、等效结构应力法)建立梁结构的有限元模型,研究焊缝处各表征应力的分布规律,分析裂纹产生的位置,计算疲劳寿命,比较不同表征应力的评定效果.结果表明,名义应力和热点应力的分布曲线相似,存在一定的波纹特性,但根据波纹变化无法准确判断裂纹产生位置及预测疲劳寿命;等效结构应力分布曲线的波纹变化特性十分显著,可较好地预测裂纹产生位置并较准确地估算疲劳寿命.因此建议采用等效结构应力作为梯形波纹腹板焊接梁结构的寿命控制参量.     

焊接结构模态结构应力法程序开发及工程应用

主S-N曲线法作为疲劳计算的新方法在焊接结构疲劳分析中被广泛采用.为了实现该方法在试验载荷下基于稳态动力学计算结果开展焊接结构疲劳寿命预测,首先引入台架模型作为边界条件,实现将试验载荷作为仿真分析的输入,基于模态叠加法的稳态动力学理论获得较准确的焊缝动态响应.其次在主S-N曲线法的准静态计算流程基础上,扩展其内涵,提出基于模态结构应力叠加的动态结构应力计算方法,该方法将稳态动力学计算的模态坐标与焊缝的模态结构应力进行叠加,实现动态结构应力计算及动态等效结构应力计算,再采用主S-N曲线进行寿命评估预测.进一步开发了焊接结构模态结构应力法疲劳评估软件,基于该软件开展了车体疲劳评估和疲劳试验对比.结果表明,该方法比传统方法更能有效地识别出动态加载下车体的疲劳破坏部位,验证了该方法在试验动态载荷加载下开展焊接结构疲劳评估的有效性和优越性,为研究焊接结构疲劳寿命评估理论和拓展主S-N曲线法提供了技术基础.     

焊缝余高对焊接接头疲劳寿命影响的有限元分析

使用Pro/E软件建立3种不同焊缝余高的焊接接头的几何模型,使用Hypermesh软件对接头进行网格划分,使用ABAQUS软件进行应力模拟分析,根据IIW标准,进行了基于名义应力法和热点应力法的接头疲劳寿命预测;使用ANSYS FE-SAFE软件进行基于网格不敏感结构应力法的疲劳寿命预测。结果表明:焊缝余高的存在降低了焊接接头的疲劳强度,且焊缝余高越大,疲劳寿命越差。     

基于Battelle结构应力法的对接接头应力集中系数回归分析

以12 mm厚的S355J2W+N耐候钢板对接焊接接头为研究对象,进行不同应力水平下的疲劳试验,将试验结果与Battelle结构应力法的主S-N曲线进行对比,验证了Battelle结构应力法在预测焊接结构寿命方面的准确性;采用有限元方法,以焊缝宽度和焊缝余高为变量,探究几何尺寸变化对焊趾部位结构应力集中系数的影响规律,并通过回归分析得出该试验条件下焊趾处结构应力集中系数的经验方程;利用该方程可快速通过接头尺寸计算得出焊趾部位的结构应力,进而对接头疲劳寿命进行大致预测,可为同类对接接头疲劳试验提供参考。     

焊缝余高对焊接接头疲劳性能影响的定量分析

为了研究焊缝余高对焊接接头疲劳性能的影响,采用名义应力法对含有焊缝余高的焊接结构连接件进行了有限元分析及寿命预测.结果发现:结构的疲劳寿命受焊缝坡度影响,随着焊缝坡度的增大,接头疲劳寿命先增大后减小,呈抛物线变化趋势.焊缝余高的变化也影响着结构疲劳性能,当焊缝余高为0.4mm、焊缝坡度为65°时,焊接接头疲劳寿命最大.     

不锈钢车体点焊接头疲劳特性分析

为获取不锈钢车体点焊结构的疲劳特性，提出了一种用于点焊疲劳寿命评估的S-N曲线和P-S-N曲线. 首先，对点焊试件进行拉剪疲劳试验，得到点焊试件的疲劳寿命. 然后，建立点焊试件体单元和壳单元有限元模型，并将仿真结果与准静态试验结果对比，验证了壳单元有限元模型的准确性. 之后，基于Rupp法得到点焊试件的等效结构应力，并根据等效结构应力和试验寿命得到点焊试件在不同应力比下的S-N曲线. 为了消除应力比对S-N曲线的影响，基于Goodman修正法将非对称循环下的结构应力当量为对称循环下的结构应力，得到了点焊试件的基本S-N曲线. 最后，根据三种方法绘制出了点焊的P-S-N曲线，对比得到基于破坏率的方法一和基于等效寿命的方法三能够较为准确地预测点焊的真实寿命，为点焊结构的设计及寿命预测提供一定的参考.     

结构有限寿命设计法——名义应力法

介绍了一种结构有限寿命设计方法——名义应力法。阐述了名义应力有限寿命设计法的一般步骤,并对设计方法中的几个关键问题如应力谱的简化处理、疲劳寿命的预测等做了详细的介绍。以线性累积损伤法则和应力-寿命曲线为依据,推导出适用于变幅载荷下的有限寿命设计公式。最后通过算例说明采用此方法的优越性。     

基于ANSYS的斗齿疲劳寿命预测

疲劳破坏是斗轮堆取料机用斗齿在实际工况下主要的失效形式之一。通过有限元分析软件ANSYS建立斗齿的有限元模型,对其进行静力强度计算,得出斗齿在服役中的应力最大节点和应力集中区域。通过名义应力法并且结合ZGMn 13材料的S-N曲线,利用ANSYS中的Fatigue模块进行斗齿结构的疲劳寿命计算,预测其疲劳寿命,为斗齿的可靠性设计和结构优化提供依据。     

超高强钢焊点的强度与寿命研究

以超高强钢22Mn B5搭接型点焊结构为研究对象,通过建立与试验一样的点焊结构力学模型,在ANSYS中进行数值仿真,得到塑性环是点焊结构的强度和疲劳寿命的破坏初始点。同时,分析了不同参量变化对点焊结构强度的影响。又通过名义应力法和等效结构应力法对焊点的强度进行计算,前者算法精度相对较高,也得到塑性环是点焊结构失效的起裂处,并使用名义应力法,得到点焊结构的参量变化对疲劳寿命的影响程度,为点焊结构的设计提供参考。     

基于工业CT的材料疲劳寿命预测

在分析材料的工业CT图像基础上,提出了一种疲劳寿命预测方法。在该方法中,首先将裂纹的萌生、扩展过程分为显微尺度细观裂纹、CT尺度裂纹和宏观裂纹三个阶段;然后采用不同的裂纹萌生、扩展标准对材料疲劳寿命进行预测;最后相加各阶段预测寿命,得到材料疲劳寿命。与疲劳累积损伤理论法、名义应力法等相比,该方法预测的材料疲劳寿命具有较高的精度。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.