Effect of strength matching on the reliability of welded pipe with circumferential surface crack

For different strength matching, the reliability index and failure probability of welded pressure pipe with circumferential surface crack were calculated using three dimensional stochastic finite element method. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The effects of external moment and the depth of the circumferential surface crack (a) on the reliability of pressure pipe were also calculated and discussed. The calculation results indicate that the strength matching has certain effect on the reliability of the welded pressure pipe with circumferential surface crack. The failure probability of welded pressure pipe with high strength matching is lower than that with low strength matching at the same conditions. The effects of strength matching on the failure probability and reliability index increased by adding external moment (M) and the depth of the circumferential surface crack (a).

A new step-cooling process for strength and toughness matching control of vanadium-containing railway wheels:effect of intragranular ferrite

To improve the competitive relationship between strength and toughness,the effect of low undercooling in austenite(γ)on the microstructure and mechanical properties of commercial vanadium-containing wheel steels was studied using an optical microscope(OM),a scanning electron microscope(SEM),a transmission electron microscope(TEM),and mechanical property tests.The results show that when the wheel steel is slightly cooled to an appropriate temperature above A c3 point for a short time after it has been austenitized at an elevated temperature,the solid-solved vanadium is pre-precipitated in the form of V(C,N)second phase semicoherent with the matrix in the originalγgrain.This phase hardly participates in matrix strengthening.Due to the small mismatch between V(C,N)and ferrite(α),during the subsequent-cooling phase transformation stage,the pre-precipitated second phase becomes theαnucleation point,causing granular and ellipsoidal intragranular ferrite(IGF,with an average size of 4-6μm)to nucleate in the originalγ.The IGF production and strength loss increases with the increasing undercooling degree.Based on this,Masteel Co.,Ltd.has developed a new heat-treatment step-cooling process that can promote the formation of IGF,considerably improving the level and uniformity of fracture toughness on the premise that the strength and hardness of the wheel are almost unchanged.

Effects of strength matching and crack depth on the fracture parameters for welded joints

Fracture parameters of welded joints with different strength matching and crack depth in weld metal are investigated by using the methods of elastoplastic finite element analysis and three point bend specimen test. The results show that for shallow crack, the plastic zone turns large in loading process, and the fracture toughness turns high. The extent of the plastic zone of overmatched joint is larger than that of undermatched joint because it will extends to parent metal from the weld metal in loading process for the same CTOD value. The plastic zone of undermatched joint is restricted within the weld, and the size of that is small. Overmatched joint shows the fracture behaviour of shallow crack may more easily than the undermatched joint, while the two sorts of joint specimens have the same crack depth. Therefore, the fracture-resistant capability of overmatched weld is better than that of undermatched weld. when the toughness of weld metals is similar for both overmatched and undermatched joints.

T23/P23钢高强匹配焊缝金属接头再热裂纹表征

综述了T23/P23钢高强匹配焊缝金属接头再热裂纹的特征。结果表明,T23/P23耐热钢高强匹配接头再热裂纹倾向明显,焊后状态高强匹配接头具有较高的强度和可以接受的塑性和韧性。接头显微组织中的HAZ粗晶区碳化物析出、晶界的滑移及晶界的脆化是再热裂纹产生的必要条件;影响HAZ组织的主要因素是母材中碳化物形成元素和残留元素的种类及含量。随接头拘束应力增大,再热温度升高时再热裂纹倾向增大。T23/P23钢接头中氢的行为是产生再热裂纹不可忽视的影响因素。生产中常用低应力化和低氢化综合工艺及参数,以及新型专用焊接材料等措施,使接头中的应力水平降低,氢含量最小化,控制再热裂纹形成条件,并获得了较满意的效果。

钢桥焊接接头强韧匹配现状分析

综述了国内钢桥焊接接头强韧性匹配情况。钢板及焊接材料试验数据表明:原材料的强度波动范围较大,给强度匹配带来较大的难度,需要在原材料标准中对其强度范围进行限制;某些项目规定的焊缝强度限制指标缺乏理论依据,需要进行专题研究制定合理的波动范围。

高强β钛合金的发展现状与强化方法

钛合金是比强度最高的金属材料之一,广泛应用在航空航天领域。随着材料技术的进步,人们对高强钛合金的研究与开发也逐渐深入。综述了国内外高强β钛合金的发展现状与主要的强化方式。重点介绍了Ti-13-11-3、Ti-l023、Ti-5553以及Ti-55531等典型高强钛β合金。梳理了高强β钛合金的设计思路,指出了限制高强β钛合金向更优性能发展的瓶颈并提出了可能的解决途径。总结了固溶强化、析出强化、加工硬化、细晶强化以及增材技术等高强β钛合金的强化方法,以期为进一步提高高强β钛合金的强度、优化高强β钛合金综合性能提供指导。

TC18钛合金大规格棒材热变形行为研究进展

近年来,随着自由锻造装备大型化的不断发展,航空航天关键结构件用锻件的大型化需求急剧增长,大规格棒材的制备成为了科研及工业化生产的重点工作。TC18钛合金作为一类高合金化、热变形参数敏感型高强高韧钛合金,已逐步成为航空航天关键装备的核心结构材料,因此,其棒材的大型化成为了近年来研究及生产的重点方向。本文梳理了近年来TC18钛合金大规格棒材(Φ300~Φ500 mm)生产技术概况,综述了TC18钛合金热变形数值模拟的相关研究,分析铸锭熔炼、锻造成型及热处理工艺的现状,总结大规格棒材现存问题及解决方法。最后,展望原材料制备过程今后一段时间的研究重点,结合使用单位对TC18钛合金棒材的使用需求,力争在未来打通原材料和成品锻件的全流程制造工艺,实现工艺个性化设计、组织性能定量调控。

A strength reduction method based on double reduction parameters and its application

In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent.Regarding this defect,a strength reduction method based on double reduction parameters,which adopts different reduction parameters,is proposed.The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles.This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle,described asη.With the increase in the slope angle,ηincreases;in particular,when the slope angle is 45°,ηis 1.0.Through the matching reduction principle,different safety margin factors can be calculated for the cohesion and friction angle.In combination with these two safety margin factors,a formula for calculating the overall safety factor of the slope is proposed,reflecting the different contributions of the cohesion and friction angle to the slope stability.Finally,it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method,but the calculation results are very close to those obtained by the limit equilibrium method.

基于稳定AP选择的动态室内定位方法

在室内复杂多变环境下,基于接收信号强度指示(Received Signal Strength Indication,RSSI)的位置指纹算法得到了广泛研究。其中,在线阶段的匹配算法通常采用加权K近邻(Weighted K-Nearest Neighbor,WKNN)算法,但该算法往往采用固定k值方法存在较大的定位误差,具有一定的局限性,并且离线阶段构建位置指纹数据库时并没有考虑到无线接入点(Access Point,AP)信号的波动性。因此,存在大量不同AP的冗余信息,对定位效果产生较大影响。针对上述问题,提出一种基于稳定AP选择的动态室内定位方法。首先,通过高斯滤波对RSSI值进行预处理,滤除随机干扰;然后,通过优选AP算法计算AP的稳定度,筛选出关键AP用于定位;最后,利用距离阈值动态调整k值,并对权重系数进行改善,实现了对WKNN算法的改进。实验结果表明,基于稳定AP选择的动态室内定位方法可以有效去除冗余AP信息,并实现动态k值方案,在定位精度上优于K近邻(K-Nearest Neighbors,KNN)算法、加权K近邻算法和改进的加权K近邻算法,平均定位误差分别降低了26.13%、21.29%和9.89%,定位误差在1.5 m内的累积分布概率达到了60.41%,分别提升了25%、16.66%和8.33%,定位效果提升明显。

高强度细晶粒结构钢焊接性影响因素综述

综述了涉及高强度细晶粒结构钢焊接性的影响因素。结果表明,高强度细晶粒结构钢焊接性主要问题是接头的冷裂纹敏感性、HAZ的软化和脆化倾向,以及再热裂纹敏感性。焊缝强度匹配对铁研试件裂纹形态的影响,涉及焊缝与母材的相变温度以及焊缝中氢的扩散方向等因素。焊接接头硬度分布中呈现的低硬度HAZ软化区与接头拉伸试件断口部位相一致,表明HAZ软化区是该接头的薄弱环节。热输入对接头力学性能的影响表现为随热输入增大,抗拉强度和屈服强度均被降低,焊缝和HAZ区的冲击吸收能量略有减小。激光焊接试样的较高疲劳寿命是激光焊接工艺特性所决定的。

基于工程应用的海洋结构用A517Q和A514Q钢焊接材料选用原则探讨

探讨了工程应用中A517Q和A514Q钢焊接材料的选用原则。结果表明,A517Q和A514Q钢焊接性的主要问题是接头的冷裂纹敏感性。在工程条件下该钢使用的焊接材料首推低强匹配方式,“焊缝低氢化工艺”可以明显改善钢的焊接性。该类钢焊接材料的成功应用中,焊接材料自身的高强、高韧性和超低氢化是必要条件,而焊接方法和工艺因素的低氢化则是充分条件。工程上实用的工艺方法和典型焊接材料各具特色,采用FCAW打底焊+各种方法填充焊的工艺优势明显。

辜鸿铭《论语》英译的文章翻译学解读

辜鸿铭英译《论语》是最有影响力的《论语》译本之一,为儒家思想的西传做出了卓越贡献。从文章翻译学的视角考察,辜译《论语》的成功主要源于三方面的因素:译者的经历和学识等为其《论语》翻译实践奠定基础,译者的翻译思想与严复的“信、达、雅”不谋而合,译者的语言表达从整体上保障了译文与原文的“义合”“体合”与“气合”。文章翻译学将“文章”的概念从一种语言和文化延伸到另外一种语言和文化,拓展了人们对翻译本质和翻译原则的理解。从文章翻译学角度解读辜译《论语》,可为中国文化典籍外译实践与研究提供重要启示。

高钢级管线环焊缝强度匹配的仪器化压痕法测试研究

为获得在役管线环焊缝强度及与母材的强度匹配情况,选用仪器化压痕法对高钢级管线环焊缝的强度及匹配情况进行检测。为验证仪器化压痕法检测结果的准确性,对经过压痕检测的环焊缝取常规拉伸试样进行检测并对比结果。两种强度测试方法的结果对比表明,压痕测试的屈服强度比拉伸测试结果高约6%、抗拉强度比拉伸测试高约16%。利用阵列硬度对焊缝及母材的硬度分布进行表征,发现焊缝内硬度分层分布、近外壁区域硬度较高,母材硬度相对均匀。仪器化压痕测试的材料为近外壁的高硬度区,拉伸测试的材料为管道壁厚的平均结果,材料性能的沿厚度方向的分布特征是压痕法测得结果偏高的原因之一。

红外热源辅助开放空间工业机器人熔融沉积成形装备设计与成形性能研究

针对开放空间工业机器人熔融沉积成形(FDM)的关键问题,研发了基于6轴关节型机器人的FDM设备及控制系统。自主设计了可辅助加热的打印头,开发了打印控制系统和机器人控制系统。通过提出打印头挤出速度和机器人运动的同步匹配方法,实现了机器人FDM装备的稳定工作。然后提出了红外热源辅助工业机器人FDM成形方法,通过工艺试验研究了辅助热源参数对制件宏观力学性能和表面粗糙度的影响规律,通过微观结构表征分析了增强机理。研究结果表明:在开放空间环境下,红外热源可有效提高基材温度,显著增强分子链在股线界面处的扩散缠结、提高界面结合强度,使得层间结合强度增大17.6%、制件表面粗糙度降低58%,验证了红外热源辅助开放空间工业机器人熔融沉积成形方法的可行性和高效性。

Mechanisms and experimental research of ion-matched waterflooding to enhance oil recovery in carbonate reservoirs: A case of Cretaceous limestone reservoirs in Halfaya Oilfield, Middle East

Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examined according to two classification standards,and the influence of behaviors of different ions on different mechanisms and oil displacement efficiency are investigated.Ionic strength is proposed to characterize the behavior differences of univalent and divalent ions,the relationships between ionic strength,effective concentration,and mechanisms are established to characterize the ion behavior behind various mechanisms,and evaluate the performance of ion-matched injection water.The mechanisms of enhancing oil recovery by ion-matched waterflooding include:(1)The ion-matched water can reduce the ion strength and match the ion composition of formation water,thereby reducing the difference between the effective concentration of univalent ions and divalent ions on the surface of carbonate rocks,and improving the effective concentration of potential determining ions(especially SO42-).(2)It can improve wettability,oil-water interface properties,pore structure and physical properties of the reservoir,and finally enable the establishment of a new ionic equilibrium conducive to waterflooding while breaking the original equilibrium.In this study,experiments such as relative permeability curve,interfacial tension,and core-flooding were carried out on carbonate core samples from the Cretaceous Mishrif Formation reservoirs in Halfaya Oilfield,Middle East,a method for injection water evaluation was established and the injection water suitable for these reservoirs was selected:6 times diluted seawater.Compared with ordinary seawater,oil displacement efficiency can be increased by more than 4.60%and compared with the optimum dilution of formation water,oil displacement efficiency can be increased by 3.14%.

基于有效受剪面积的节理面吻合度量化方法研究

节理粗糙度系数-节理抗压强度(JRC-JCS)模型为岩体节理面抗剪强度估算提供了很好的思路,但对于吻合度较差的节理岩体,该模型往往过高地估算其抗剪强度。节理粗糙度系数-节理吻合系数(JRC-JMC)模型进一步考虑节理吻合度对抗剪强度的影响,为吻合程度较差的节理面的抗剪强度估算提供了很好的思路,但目前节理吻合度的量化分析还存在困难。在以往研究基础上,采用重复剪切试验的方法制备了不同吻合度的节理岩体试样,综合节理面形貌特征和节理面抗剪性能变化规律分析,提出了节理吻合度的量化计算方法。研究结果表明:(1)在重复剪切作用下,岩体节理面的抗剪强度和节理面形貌参数呈现先陡后缓的降低趋势,节理面上下盘的吻合程度逐渐降低;(2)根据剪切前后节理面形貌特征的对比分析,确定了剪切过程节理面的有效接触区域,提出了节理吻合系数JMC的量化计算方法;(3)对比分析表明,与单独考虑JRC相比,将JRC和JMC综合在一起可以更好地反映节理形貌特征对其剪切性能的影响。相关研究方法和分析结果可为岩体节理面抗剪性能分析提供较好的参考。

X80钢不同强度匹配打底焊接头的冷裂敏感性

选用低强、等强和高强匹配的3种低氢型焊条,在80℃预热条件下分别对X80钢板进行U形坡口和斜Y形坡口打底焊,计算了接头断面裂纹率,并进行了维氏硬度测试,评价了等强和高强匹配焊条打底焊接头的冷裂敏感性。结果表明:焊条的冷裂纹敏感指数随强度等级提高而增大,但焊缝表面及断面均未发现裂纹,断面裂纹率为0,说明冷裂敏感性并未随焊条强度增大而增强。与低强匹配焊条打底焊相比,等强和高强匹配焊条打底焊后热影响区硬度未明显增大,即淬硬倾向未明显增大、冷裂敏感性未增强。等强和高强匹配焊条可用于X80钢的打底焊。

基于熵权-WRSR法的高水平女排比赛攻防综合实力评价研究

为认识和把握湖南省大学生高水平女排的攻防综合实力及实力格局分布,运用熵权-WRSR法以及文献资料、数理统计、录像观察等研究方法,对2022年湖南省第十二届大学生运动会大学组5支女子排球队进行分析.结果表明:进攻实力湖南师范大学WRSR值最高;防守实力中南大学WRSR值最高;攻防综合实力中南大学WRSR值最高.进攻WRSR值(r=0.942,P<0.05)与最终排名呈显著相关;防守(r=0.309,P>0.05)和攻防(r=0.832,P>0.05)WRSR值与最终排名呈不显著相关.实力格局分布上,进攻方面中南大学和湖南师范大学排在一档水平,湖南工业大学和中南林业大学排在二档水平,南华大学在三档水平;防守方面中南大学排在一档水平,湖南师范大学、湖南工业大学、中南林业大学和南华大学排在二档水平;攻防方面中南大学排在一档水平,湖南师范大学、湖南工业大学、中南林业大学和南华大学排在二档水平.

强度匹配对含裂纹缺陷X80钢管道断裂参量的影响

通过对埋地管道X80高强钢的断裂评定研究,为工程中埋地管道的安全设计提供参考。通过埋地管道的应力分析,用软件分别模拟了无裂纹管道和含裂纹缺陷管道的断裂参量,研究了管道极限承载的有限元算法,并分析了强度匹配对含裂纹缺陷X80钢管道断裂行为的影响规律,计算结果表明,在相同载荷作用下,高匹配的焊接接头比低匹配接头具有更好的抗断裂能力。

含裂纹缺陷X80钢的有限元分析与安全评价

X80钢是控轧控冷的低碳合金钢,具有良好的强韧性,在油气运输管线中广泛应用。近几年因焊接裂纹引发的失效事故多发,焊接接头服役安全问题备受关注,有关含裂纹缺陷X80钢焊接接头的安全评价意义重大。文中利用有限元模拟计算X80钢焊接接头在不同应力状态时的同一载荷下,裂纹位于不同位置和不同强度匹配下的断裂参量。结果表明,无论接头处于平面应力还是平面应变状态,高匹配还是低匹配,在同一载荷下,当裂纹位于热影响区HAZ(Heat affected zone)和熔合线时的J积分值比母材和焊缝的都大,且熔合线处的J积分最大,接头最危险。