Formability and strengthening mechanism of AA6061 tubular components under solid granule medium internal high pressure forming

A new technological process of tube forming was developed, namely solution treatment → granule medium internal high pressure forming → artificial aging. During this process, the mechanical properties of AA6061 tube can be adjusted by heat treatment to satisfy the process requirements and the processing method can also be realized by granule medium internal high pressure forming technology with the features of convenient implementation, low requirement to equipment and flexible design in product. Results show that, at a solution temperature of 560 ℃ and time of 120 min, the elongation of AA6061 increases by 313%, but the strength and the hardness dramatically decrease. At an aging temperature of 180 ℃ and time of 360 min, the strength and hardness of AA6061 alloy are recovered to the values of the as-received alloy. The maximum expansion ratio（MER） of AA6061 tube increases by 25.5% and the material properties of formed tube reach the performances of raw material.

Heat treatment and granule medium internal highpressure forming of AA6061 tube

The new forming process of AA6061 alloy tube, including solution treatment, granule medium internal high-pressure forming and aging treatment, was developed. The AA6061 alloy tube via heat treatment satisfied the forming requirement, and the granule medium internal high pressure forming method for AA6061 alloy tube was also realized by using convenient implementation with low requirement of equipment and flexible design of product. At a solution temperature of 560℃ and time of 120 min, the elongation of the AA6061 extruded tube increases by 300% and the strength and the hardness dramatically decrease too. Therefore, the AA6061 alloy tube meets the requirement of internal high-pressure forming because of the improvement of formability. The experiments shows that the strength and hardness of AA6061 alloy workpiece recover to that of the as-received alloy at an aging temperature of 180℃ and time of 360 min, and the strength of AA6061 alloy workpiece is equal to the base alloy. The typical parts of convex ring tube, stepped shaft tube and hexagonal tube were successfully produced in lab by using the present forming method. The forming tests show that the maximum expansion ratio(MER) of the AA6061 extruded tube increases by 25.5% and the material properties of formed AA6061 alloy tube reached the performance of as-received alloy.

Closed-form internal impedance model and characterization of mixed carbon nanotube bundles for three-dimensional integrated circuits

Based on the complex effective conductivity method, a closed-form expression for the internal impedance of mixed carbon nanotube （CNT） bundles, in which the number of CNTs for a given diameter follows a Gaussian distribution, is proposed in this paper. It can appropriately capture the skin effect as well as the temperature effect of mixed CNT bundles. The results of the closed-form expression and the numerical calculation are compared with various mean diameters, standard deviations, and temperatures. It is shown that the proposed model has very high accuracy in the whole frequency range considered, with maximum errors of 1% and 2.3% for the resistance and the internal inductance, respectively. Moreover, by using the proposed model, the high-frequency electrical characteristics of mixed CNT bundles are deeply analyzed to provide helpful design guidelines for their application in future high-performance three-dimensional integrated circuits.

Numerical Simulation and Experiments of Hydroforming of Rectangular-section Tubular Component

In order to reduce high calibration pressure in hydroforming of components with too small radii, a method wasproposed to manufacture automotive hollow components with rectangular shape by relatively lower pressure. Theprocess is simulated and analyzed. It is thought that the friction force between the die surface and tube is a mainreason that high pressure is needed to form small radii. Using the method proposed in this paper, a petal-like sectionshape is first preformed so that the central zones of the four sides of the preform section do not contact with the diesides, thus the tube metal is easy to flow into the transition radii area in calibration stage. Moreover, a positive forcealong the sides is produced by the internal pressure, which is beneficial to overcome the friction force and push thematerial into the radii. Therefore, the pressure for forming the transition radii is greatly reduced and the componentswith small radii can be formed with relatively lower pressure. For the experimental case conducted in this paper, theforming pressure is reduced by about 28.6% than the estimated forming pressure.

1∶2 INTERNAL RESONANCE OF COUPLED DYNAMIC SYSTEM WITH QUADRATIC AND CUBIC NONLINEARITIES

The 1:2 internal resonance of coupled dynamic system with quadratic and cubic nonlinearities is studied. The normal forms of this system in 1 :2 internal resonance were derived by using the direct method of normal form. In the normal,forms, quadratic and cubic nonlinearities were remained. Based on a new convenient transformation technique, the 4-dimension bifurcation equations were reduced to 3-dimension. A bifurcation equation with one-dimension was obtained. Then the bifurcation behaviors of a universal unfolding were studied by using the singularity theory. The method of this paper can be applied to analyze the bifurcation behavior in strong internal resonance on 4-dimension center manifolds.

Influence of Axial Feeding on Hydroforming of Aluminum Alloy Tubular Part with Rectangular Section

The hydroforming experiment of aluminum tubular part with rectangular section was carried out to investigate influence of axial feeding on thickness distribution and calibration pressure of the corner.Thickness distribution and relation between corner radius and internal pressure were analyzed.The influence of lubricant was discussed.Microstructure and hardness of different region were observed.It is shown that thickness reduction in the transition region between the corner and center region is the biggest.Friction condition has influence both on the thickness distribution and calibration pressure of the corner.As the increase of the axial feeding,the calibration pressure is decreased.There is only little change for the microstructure,but the hardness is increased by 23.3% for the transition region.

Morphology and internal architecture of a banner bank off Chengshan Headland, Shandong Peninsula

A banner bank off the north coast of the Chengshan Headland, Shandong Peninsula, has been described on the basis of echo sounder bathymetry, side-scan sonar and high-resolution seismic data sets. The bank is in NWW direction, approximately parallel to the coastline. The bank consists of sandy silt or clayed silt. Sand waves and megaripples are observed on the north side, which result from strong tidal currents around the headland and storm waves in winter. These bed forms indicate that the bank is influenced by the modern hydrodynamics. The bank is separated from the coast and Holocene subaqueous clinoform around the Shandong Peninsula in its east part. High-resolution seismic profiles reveal that the bank was formed during two periods： the earlier seismic unit Ua, and later seismic units Ub and Uc which overlays Ua with erosional surfaces on its south side and north side, respectively. As comparing with the clinoform, the bank has a different internal architecture. In the west of the bank, however, topography and surface sediment characteristics suggest that the bank links to the clinoform. The authors propose that seismic Ua is a residual part of early clinoform deposit. After the sediments in the north and south of Ua were eroded by strong currents, the Ub and Uc started to deposit probably by a complex hydrodynamic process. These results provide new insights into the evolution of the bank and its relation with the Holocene subqueous clinoform.

Effect of wrinkles on formability in hydroforming a double-diameter aluminum alloy tubular part

An experiment was conducted on hydroforming a double-diameter aluminum alloy tubular part.The influence of loading paths,i.e.the relation between internal pressure and axial feeding,on the forming results was emphasized with fixed total axial feeding length.The loading paths were analyzed together with the corresponding diagram of stress and strain.Two kinds of bursting phenomenon occurred in the experiment.Sound part can be formed whether there are wrinkles or not.It is indicated by the experiment results that the loading path has great effect on the distribution of material during axial feeding.The thickness distribution is more even for the part formed with wrinkles than that without wrinkles.

中国锂矿的多旋回深循环内外生一体化成矿理论及其找矿应用

中国锂资源的分布具有卤水型与硬岩型相伴相随、若即若离的特点。“多旋回深循环内外生一体化”成锂理论,在多年三稀金属矿产找矿实践和理论研究的基础上不断丰富完善。中国锂矿的形成与“多旋回”构造运动密切相关,从前寒武纪到新生代均有成矿潜力,可构成一个完整的多旋回成矿谱系。锂的“深循环”,一是锂深度参与成岩成矿的物质循环;二是需要一个“圈闭”的构造背景将锂“捕获”以避免其过度分散,锂从开始加入到岩浆与最终定位的深度之差,是硬岩型锂矿成矿的关键之一,压差越大越有利于伟晶岩型锂矿的形成。大量锂矿实例显示锂的物质循环是“内外生一体化”的统一过程,高海拔地区(山上)的含锂地质体(花岗岩类甚至直接就是含锂矿床)经风化剥蚀之后,可能成为沉积型锂矿的物质来源之一;而富含锂的沉积岩经过埋藏、变质、深熔也可以形成含锂的岩浆岩、伟晶岩。我国西部塔里木盆地、四川盆地、扎布耶盆地及东部的江汉盆地、吉泰盆地、周田盆地等大小不一的盆地均含锂,而其周边造山带中也不同程度发育硬岩型锂矿,这就为区域找矿指明了方向。“多旋回深循环内外生一体化”成锂理论是三稀矿产成矿理论的重要组成部分,为我国锂矿找矿工作提供了指导和借鉴,在甲基卡、可尔因、阿尔金、幕阜山等锂矿矿集区的找矿实践中发挥了积极作用。

国际大石油公司敏捷型组织变革及启示——以bp、埃克森美孚为例

敏捷型组织是企业组织由封闭向开放转变的一种高级形式,属于客户价值型、利益相关者价值型的组织形态,其特征包括构建分布式价值创造模式、建立赋能式团队、形成快速决策和学习的循环模式、激活员工和加速技术迭代。传统石油公司的组织管理模式已经不能适应复杂多变的环境、多元化业务协同发展、以客户需求为导向的价值创造模式的改变等,快速、敏捷和高效的组织形式变得至关重要。bp公司的“事业部+集成管理”模式和埃克森美孚“低结构性成本”模式是向敏捷组织转变的积极探索。中国石油企业传统的直线型、职能型管理模式已经不能适应新的发展要求,需要从管理理念到实践上对企业组织体系进行敏捷化变革,包括树立敏捷型的组织管理理念、加快组织机构敏捷化转变、加强敏捷性领导力培育。

柱脚不同连接形式钢框架-摇摆墙结构抗震性能对比分析

增设摇摆墙后框架结构地震下柱脚仍会发生一定程度的塑性损伤,将柱脚设置为铰接或提离后有望减轻上述缺陷。以三层、六层和九层钢框架为基准模型,分别建立柱脚固接、铰接及提离三种框架-摇摆墙结构模型并进行动力弹塑性时程分析,对比各结构最大侧向位移、层间位移角、峰值加速度、层间剪力、墙体剪力和弯矩等;进一步建立耗能连梁固接和铰接的对比模型,研究连梁连接方式对结构抗震性能的影响。结果表明:三层模型中柱脚固接时侧向位移、层间位移角、加速度、层间剪力及摇摆墙墙体剪力的控制效果最优,六层、九层模型中分别对应柱脚提离和柱脚铰接效果最好;摇摆墙墙体剪力图和弯矩图分别呈现“C形”和“反C形”,柱脚固接时墙体弯矩均为最小,与层数无关。柱脚固接耗能连梁两端采用固接最优,柱脚铰接和柱脚提离时耗能连梁两端采用铰接形式效果更优。此分析可为框架-摇摆墙结构进一步推广应用提供参考。

内孤立波作用下缓波形立管动力特性研究

我国南海活跃着大量内孤立波,严重威胁海洋工程作业的安全。本文采用向量式有限元方法分析内孤立波作用下深海缓波形钢悬链立管动力特性,建立考虑触地段土反力和内孤立波载荷的缓波形钢悬链立管动力模型,根据mKdV方程求解内孤立波载荷,基于向量式有限元梁单元编制Fortran计算程序。分析不同入射角内孤立波作用下立管的位移极值、张力及弯矩变化趋势,并比较缓波形立管与简单钢悬链立管在内孤立波作用下的动力特性。结果表明:内孤立波作用下,缓波形钢悬链立管会有较大的位移响应,特别是顶部悬垂段会有较大的水平位移;缓波形立管比简单钢悬链立管有更显著的张力变化幅值,有更加复杂的弯矩变化趋势。

基于规培研究生与实习生“一对一”带教下的形成性评价模式探索

目的:探索规培研究生与实习生“一对一”带教下的形成性评价模式于中医学实习过程中的应用效果。方法:选取2020年6月-2021年5月于我院实习的63名五年制中医学专业医学生作为研究对象,在实习过程中采用规培研究生与实习生“一对一”带教,并进行形成性评价,最终采取OSCE考核对临床实践效果进行对比。结果:实验组OSCE评分较对照组有所提高,其中实验组中医操作、中医临床答辩、体格检查、西医操作等项目差异具有统计学意义(P<0.05)。结论:基于规培研究生与实习生“一对一”带教下的形成性评价模式可有效提高医学实习生临床实践能力。

置信专业活动在神经内科住培模式构建中的研究与实践

第三代医学教育改革的特点是强调以胜任力为导向的医学教育,但仍存在着无法忽视的不足,因此文章引入了置信专业活动这一概念。置信专业活动是指在临床环境中监督者通过观察和衡量后可以信任并委托给学员的专业活动,这一活动可以高效并且可靠地帮助监督者判断住培学员的能力,并促进住培学员能力的提升。目前为止,我国神经内科现有形成性评价体系仍不全面,无法有效地评价住院医师规范化培训(以下简称“住培”)学员在临床工作中的能力,国内也没有神经内科住培相关的置信专业活动。文章立足2020—2023年国内外临床医学教育相关研究,借鉴国际经验并结合我国实践经验分析置信专业活动的发展起源、现状、阻碍和前景,为我国神经内科住培模式构建的研究与实践提供思路及方向。

基于国际化卓越人才培养的中医内科学双语教学探索与实践

中医内科学蕴含着丰富的原创中医思维和独特诊疗思路,对中医学术的传承发展和推广应用具有基础性的关键作用。双语教学是指以两种语言作为教学媒介,达到学习学科知识和打破语言障碍的双重目的。以培养国际化卓越人才为目标,在高等中医药院校开展中英文双语的中医内科学教学,可以使学生提高中医药专业英语的表达与运用能力,拓展其临床与学术的交流领域,获得更大的发展潜力。文章提出开展中医内科学双语教学能提高中医药学国际认可度、加强中西医学交流合作、传播中华民族特色文化、吸引国外人才来华访问学习。通过探索与实践中医内科学双语教学,努力达到创新教学理念、改革教学方法、开展形成性评价等,有利于提升高等中医药院校中医学专业国际化教学水平与学术影响力。

轻质高强异形管件充液压制成形技术

目的针对轻质高强异形管状构件的迫切需求,研发了充液压制成形技术,以在低载荷下成形出具有高强度、大尺寸、小圆角等特征的异形空心薄壁管状构件。方法给出了充液压制成形的力学原理,建立了成形过程压制力计算模型与临界支撑内压理论模型,分析了充液压制成形过程失稳屈曲/起皱规律、圆角充填机理与壁厚分布规律。结果当管材充液压制过程所需的支撑内压为内高压成形压力的1/10~1/20时,就可以避免管坯发生失稳屈曲与起皱,同时使压制力大幅降低。在弯曲与压缩应力复合作用下对管坯进行圆角充填,充液压制成形得到的管件壁厚减薄非常小。结论利用小吨位合模压力机在超低压条件下可以充液压制成形出具有小圆角与均匀壁厚的轻质高强异形管件,解决了传统内高压成形压力高、易发生开裂等难题。

内高压成形液压机缸筒环缝埋弧焊焊剂防脱装置研制与应用

【目的】对传统埋弧焊接焊剂的单向防脱落机构进行改进,以提高小直径的筒体焊接效率。【方法】通过剖析小管径产品焊接缺陷,在埋弧焊机枪侧增加焊剂防脱装置,设计并应用了一个具有自动张开挡板、旋转更换不同直径的侧板机构,以及左右支撑板宽度调节机构,形成一个围挡机构,以实现不同直径、不同坡口的筒体焊接,确保在焊接过程中焊剂有效供给,从而提高缸筒焊接质量。【结果】优化后的焊剂防脱装置应用于实践,产品焊接质量提高20%,焊接质量更加稳定。【结论】可以有效扩展埋弧焊接应用范围,提高不同管径的焊接效率,给曲面型焊接的应用提供借鉴。

Characteristics of High-Pressure Spray of a Gasoline Direct Injection Injector Under Non-Flash Boiling and Flash Boiling Conditions

The increasingly stringent emission regulations and fuel consumption requirements have elevated the demands of internal combustion engines with higher fuel efficiency and lower emissions.It has been widely demonstrated that fash boiling spray can generate shorter and wider spray with improved atomization and evaporation to promote a better air-fuel mixing process.In this study,macroscopic(far-field)spray morphologies and primary breakup(near-field)characteristics of a two-hole gasoline direct injection injector are investigated under non-flash boiling and flash boiling conditions.High speed macroscopic and microscopic imaging was used to capture the overall spray structure and near-field characteristics,respectively.N-Hexane is used as the test fuel with the injection pressure ranging from 10 MPa up to 40 MPa.For sub-cooled liquid fuel sprays,increasing fuel pressure contributes to enhanced fuel atomization and evaporation.Evident collapses occurred under fare flash boiling conditions,and higher injection pressure weakened this phenomenon since the spray cone angle decreased due to a higher injection velocity.

轻合金矩形管件充液压制成形缺陷及横截面尺寸控制

管材充液压制是一种先进的低载荷液压成形工艺,可用于整体成形复杂薄壁管状构件。与内高压成形不同,充液压制过程中内压只起支撑作用避免失稳屈曲,主要通过模具压制获得管件外形轮廓。压制过程管坯厚向存在拉-压应力梯度,导致卸载后管件截面易产生回弹,影响尺寸精度。本研究通过对5052、AZ31B和TA1三种管材进行充液压制成形实验,分析了支撑内压和环向压缩率对矩形管件横截面尺寸的影响规律。结果表明:当支撑内压为0.6p_(s)~0.8p_(s)时,管件截面的回弹最小,此时最大回弹量小于1.5 mm,对应回弹率小于5.2%,上、下圆角半径相差小于0.1 mm。通过控制环向压缩率可减小管件回弹,截面尺寸与设计尺寸相差小于0.2 mm,尺寸偏差小于0.7%。对于5052-H、5052-O、AZ31B-M和TA1-Y矩形管件,其控制尺寸精度所需的环向临界压缩率分别为1.8%、1.7%、1.9%和1.8%。

装配式复合模壳剪力墙体系结构性能分析

装配式复合模壳剪力墙体系是近年来快速发展的一项新技术,可在剪力墙、梁、柱等构件中应用。以实际项目为例,采用三种不同的建模方法,研究模壳剪力墙体系与现浇剪力墙在结构刚度、基底剪力、构件内力等方面的差异,并对模壳剪力墙体系进行大震弹塑性损伤分析。研究结果表明,模壳剪力墙体系的结构性能稍优于现浇剪力墙体系,安全冗余度较好。同时,通过对钢筋混凝土材料自重及周期折减系数等参数的调整,提出合理、可行的模壳剪力墙体系设计方法,为类似项目提供参考。