Finite Element Simulation of Flexible Roll Forming with Supplemented Material Data and the Experimental Verification

Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

FEM simulation and experimental verification of roll forming and springback process under complex contact conditions

The application of advanced high strength steel(AHSS) has an important significance in the development of the lightweight of automobile,but the parts made of AHSS usually have defects,such as fracture and large amount of springback,etc.In this paper,a model of multi-pass roll forming and springback process of AHSS is established with finite element software ABAQUS.Then a roll forming experiment is performed,and simulation and experimental results have been compared and analyzed.The model is established under complex contact conditions,including self-contact condition.The results shows that during the process of sheet bending,large Mises stresses appear at bending corners.The smaller the bending radius is,the larger the Mises stress and strain are.Thickness of sheet metal changes differendy if the bending radius is different.When the bending radius exceeds a certain limit,the change tendency of the sheet thickness turns from increase to decrease.

Preparation of AZ91D Slurries for Semi-Solid Forming Using Al8 ( Mn, Fe) 5 Precipitates

During the solidification of the AZ91D-alloys, the Al8(Mn, Fe)5 phase is generally precipitated in the melt in advance of the precipitation of the primary α-Mg. The basic principle for manufacturing AZ91D-alloy slurries for semi solid forming is to use the Al8(Mn, Fe)5 precipitates as the heterogeneous nucleation sites for primary α-Mg phases. Microscopic analysis for the location of the Al8(Mn, Fe)5 precipitate explains that the Al8(Mn, Fe)5 precipitate is the effective heterogeneous nucleation site for the primary α-Mg phase. It was also observed that increase of the Mn content in the melt and the cooling rate below to the solid/liquid two-phase region resulted in smaller and more globular primary α-Mg due to the increase of heterogeneous nucleation sites. It was found that the average α-Mg diameter grew as a function of t0.278, where t is the holding time at the solid/liquid two-phase region. This would be attributed to the Ostwald type ripening and coalescence between primary α-Mg phases. The cooling rate below to the solid/liquid two-phase region, Mn content in AZ91D alloy, and the holding time and temperature affected on the quality of slurry.

Structure of miniature components from steel produced by forming in semi-solid state

To obtain new unconventional structures with specific mechanical and physical properties is possible not only by the development of new types of materials but also by treatment of conventional materials using unconventional innovative technological procedures.One of these technologies is the forming in semi-solid state involving rapid solidification of miniature components from steels.Production of such components is complicated by a number of technical problems.To explain phenomena of the process and structure development,the production of miniature components from the tool steel X210Cr12 difficult to form was experimentally tested.The structure of this originally ledeburite steel consisted of 95 % of metastable austenite after the treatment.Metastable austenite was located particularly in globular and polygonal grains while the remaining interspaces were filled by lamellar network.The detected high stability of extremely high fraction of metastable austenite was tested under different conditions of thermal exposition and mechanical loading.

Abnormal mechanical property evolution induced by heat treatment for a semi-solid forming hypereutectic Al-Fe base alloy

In the present study, Al-5.5Fe-4Cu-2Zn-0.4Mg-0.5Mn al oy samples were prepared by electromagnetic stirring and semi-solid forming processing, and then the effects of T6 and T1 heat treatments on the microstructures and mechanical properties of the semi-solid forming samples were investigated. The results indicate that after semi-solid forming, the mechanical properties of the sample improved significantly compared to that of the merely electromagnetically stirred sample. The grains of semi-solid forming alloy became almost fine equiaxed; big long strip-shaped Al3 Fe phases became short rod-like morphology and distributed uniformly in the matrix. However, the mechanical properties of the T6-treated semi-solid forming sample decreased significantly instead of increasing and, with solution temperature rising, the tensile strength of the al oy decreased further. The results of EDS show that after high temperature solid-solution treatment, the Cu element in the semi-solid forming alloy sample is mainly concentrated at the boundaries of the Al3 Fe phases instead of being dissolved in the matrix. At the same time, the grains of the semi-solid forming sample grew slightly after solid-solution treatment. Therefore, the growth of the grains and the accumulation of Cu element at Al3 Fe phase boundaries during solution treatment of the semi-solid forming alloy were the main reasons for the mechanical properties decreasing after T6 treatment. The mechanical properties of the alloy were improved after T1 heat treatment due to aging strengthening phase being precipitated in the matrix.

Semi-solid Forming of a Damper Housing with Dendritic and Non-dendritic Al-Si-Mg Alloy

A motorcycle component of damper housing was made by semi-solid forming process. This was used to investigate the effect of microstructures of feedstock on the formability of semisolid process. The soundness and microstructures of casting parts made by dendritic and non-dendritic feedstock were investigated. Separating of liquid phase was found in the casting produced by dendritic feedstock, which might result in defects of porosity, while uniform microstructures were found in the casting produced by no...

Double⁃Shear Experiments of Cold⁃Formed Steel Stud⁃to⁃Sheathing Connections at Elevated Temperatures

The behavior of cold⁃formed steel(CFS)stud⁃to⁃sheathing connections at elevated temperatures is an important parameter for the fire resistance design and modeling of mid⁃rise CFS structures.In this paper,three kinds of sheathings,namely,medium⁃and low⁃density calcium⁃silicate boards and oriented strand board,were selected for double⁃shear experiments on the mechanical properties of 253 screw connections at ambient and elevated temperatures.The effects of the shear direction,screw edge distance and the number of screws on the behavior of the connections were studied.The results showed that the shear direction and the screw edge distance more significantly influenced the peak deformation,while their impacts on the peak load varied with the type of sheathings.Compared with the single⁃screw connections,the peak loads of the specimens with double⁃screw connections obviously increased but did not double.Finally,a simplified load⁃displacement curve model of stud⁃to⁃sheathing connections at elevated temperature was generated first by establishing the prediction formula for characteristic parameters,such as the peak load,the peak deformation and the elastic stiffness,and then by considering whether the curves corresponded to stiffness increase phenomena.The present investigation provides basic data for future studies on the numerical modeling of CFS structures under fire conditions.

Isothermal grain growth of reactive spray formed 7075 alloys in semi-solid state

The grain growth behavior in reactive spray formed 7075+2.91 vol percent TiCAl alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. Theeffects of in-situ TiC particles on the microstructure of spray formed 7075 Al alloy were alsoinvestigated. The specimens were heat-treated isothermally at various temperatures between thesolidus and liquidus of 7075 Al alloy for times in the range of 10-60 min, then quenched in water.The microstructure of reheated specimens was characterized using scanning electron microscopy andoptical microscopy. The grain size was measured using a mean linear intercept method. Results showthat the in-situ TiC particles can effectively retard grain growth and refine the grain at a limitedsize. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates thatthe in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solidstate.

Structural evolution of spray-formed Al-70wt.%Si alloys during iso-thermal holding in the semi-solid state

The grain growth behavior of spray-formed Al-70wt.%Si alloys was studied in the semi-solid state. The specimens were isothermally heat-treated at various temperatures between the solidus and liquidus of Al-Si alloys and then quenched in water. The microstructure of reheated specimens was characterized using optical and scanning electron microscopies. The isothermal holding experiment was carried out to investigate grain growth behavior as a function of holding time and temperature in the semi-solid state. The coarsening mechanism and the effect of porosity on microstructure were also studied.

卤水表面附近盐岩结晶特征研究

【目的】为了弥补现代盐湖沉积考察中丢失的信息,获取盐岩动态结晶过程,指导古盐湖沉积研究。【方法】借助室内石盐蒸发实验,观察卤水蒸发过程中氯化钠结晶特征,分析石盐结晶与沉积环境之间的关系,为盐湖沉积模式建立提供参考。【结果与结论】石盐沉积位置受结晶习性影响,晶体可以在卤水界面之上沉积,其形成的动力除了蒸发泵作用外,还受空气湿度和石盐潮解共同控制;人字晶一般形成于漏斗晶基础之上,在发育空间受限时,绕不同漏斗晶核生长的纹层斜交后形成人字晶纹,两种晶型可以同时沉积于水面之上;盐湖干涸之前,可能经历岩层封锁水面的现象,并可能对临层的碎屑沉积物产生影响。

新版、新形态、新亮点——《有机化学实验(第六版)》简介

新形态出版的大连理工大学《有机化学实验(第六版)》融合了纸质版教材和网上数字资源,整合了第五版书附教学光盘、网站资源及新建数字资源,优化为新版数字资源作为纸质版教材的支撑和拓展。第六版教材参考了国内外实验教学论文,编著了反应机理证明、可视化制备、黄鸣龙还原及烯烃交互置换专题下14个基本性实验;编著了天然肉桂醛提取及羟醛缩合、脯氨酸催化不对称合成和LED光催化发光体制备等3个综合性实验;编著了费舍尔酯化法合成工业香料羧酸酯的设计性实验与优化微波辅助威廉森法制备4-硝基苯乙醚反应条件的研究性实验。第六版教材搭建了个性化学习平台,有助于提升学生实验能力,培养学生严谨创新的学风。

福建本地山药高山栽培对比试验

以福建省内收集的9种本地山药为材料进行栽培对比试验,通过对该9种山药生长期与采收期形态、产量等数据测定,比较各山药品种特征,筛选出适宜闽东高山地区栽培的优良山药品种。

吕晓东论治肺结节经验撷菁

总结吕晓东教授运用中医药治疗肺结节的临床经验和学术思想。吕晓东教授基于阳化气,阴成形的两个基本生理功能观,考察肺结节的发生、发展的病理环节,认为肺结节形成之机理复杂,病因纷繁,为阴分邪气积聚为肺,但病性基础变化总体以阳虚为关键,病理以气滞痰瘀胶着于肺络为核心。在肺络病的指导原则下,运用扶阳抑阴、通补肺络的手段,恢复阳主阴从,一气周流,肺络调和的生理状态,从而调复肺脏的异常功能状态、消弭肺结节的病理改变,恢复身心健康的目的,临床每获良效,具有推广应用的价值。

白话诗的“新”逻辑--闻一多新格律诗理论及意义重估

闻一多是中国现代新诗的一个醒目存在,学界对其新格律诗理论的认知却始终存在一些模糊认识。回到历史现场,重新认识闻一多对新诗发展所做的努力,有不少新的发现。闻一多新格律诗理论回应了新诗对于白话诗“新”质的发展要求,在诗形和诗质两个方面展开了积极探索,将民族性与时代性、诗形与诗质、听觉美学与视觉美学糅合在一起,奠定了现代诗歌接受由听觉美学向视觉美学转换的理论基础,拓宽了新诗的审美空间。他扎根民族土壤思考新诗发展的努力,开启了中国现代诗歌思考中国经验的阀门。

马鞍形蒙皮拉形工艺参数仿真优化与试验验证

对某马鞍形蒙皮零件在拉形过程中的起皱和破裂现象进行了研究,以得到消除缺陷的方法。采用作图法,对该蒙皮零件进行了工艺性分析,确定了工艺参数的范围,用正交试验方法设计了数值模拟方案,利用AI-FORM软件拉形模块进行了模拟仿真,并对仿真结果进行了评估,确定了一种最优的方案,并再次进行了有限元仿真验证,最后在拉形机上进行了拉形试验。发现试验结果与有限元仿真结果吻合很好,消除了起皱和破裂等缺陷,提高了零件的成形质量。结果表明,对此蒙皮零件,拉形轨迹前部分采用较大伸长率,拉伸到4.9%,后部分采用较小伸长率,最终拉伸到7%,有利于避免起皱和破裂。另外,相较于FormCAM,AI-FORM在起皱模拟方面具有明显优势。

肖长江基于形、气、神治疗不寐经验

肖长江认为,不寐发病多因情志失调、过度思虑、饮食不节、体虚劳倦等引起形、气、神改变,导致心神不安、心神失养,治疗不寐应以形、气、神为切入点,以饮食、运动之法调摄有形之体,以方药调畅脏腑气机,原创“话疗”疗法以养心神,从形、气、神同治不寐,疗效显著。本文总结肖长江基于形、气、神治疗不寐经验,附验案一则。

基于“阳化气,阴成形”理论探析陈永灿辨治慢性萎缩性胃炎伴肠上皮化生经验

慢性萎缩性胃炎伴肠上皮化生是慢性胃炎发展到胃癌的必经阶段。陈永灿认为,“阳化气,阴成形”理论可诠释慢性萎缩性胃炎伴肠上皮化生的发展及诊疗过程。“阳化气”不足导致“阴成形”太过,使脾胃生理机能改变,从而发展为慢性萎缩性胃炎伴肠上皮化生的病理过程。通过“阳化气,阴成形”理论对本病的病机进行探析,临床治疗首先辨别阴阳状态,提出扶阳气、祛阴浊的治疗原则,以标本兼治。

致密砂岩储层不同成藏环境下气水分布研究——以东胜气田十里加汗气区下石盒子组为例

中国致密砂岩气资源丰富,勘探开发潜力广阔,但已有的开发实践证明致密砂岩气藏的开发仍然面临巨大挑战,其中气水分布的精细认识是目前的主要挑战之一。为了深入揭示致密砂岩储层在不同成藏环境下的气水分布规律,本文以东胜气田十里加汗气区上古生界气藏下石盒子组1段和2+3段储层为例,在相似准则的基础上,建立宏观物理模拟实验,研究了一口水平井底部位置成藏过程中的不同充注方式、不同充注动力、不同岩心类型条件下的气水分布规律。结果表明:与连续充注相比,幂式充注下储层中的含气饱和度更高,平均比连续充注高7.95%,阶段性的充注方式使得注入气在停住期间可以进行饱和度场再分布,增大波及体积,气水分布类型主要以气水同层或含气水层为主,无边底水;充注动力研究发现,连续充注条件下强充注动力会加剧不均匀充注程度,降低充注气体的波及效率,导致致密储层中上部的大量地层水被封存,而幂式充注条件下强充注动力可以改善不均匀充注程度,改善波及区域的驱替效率,提高储层的含气饱和度;岩心类型实验显示,储层露头岩样由于其更强的非均质性,充注气体在低物性区域会绕行或充注不彻底,断裂带沟通或远离充注位置区域,充注气体未波及,形成不同规模水体。本次物理模拟实验结果与研究区测井解释结果趋于一致,研究结果对该区块不同成藏过程气水分布特征的认识具有参考意义。

人类文明新形态与中国竞技体育发展的耦合机制研究

人类文明新形态对中国共产党百年工作成就高度概括,向世界展现了社会主义发展的光明前景和中华民族的独有贡献,中国竞技体育发展与中国共产党创建人类文明新形态一脉相承,为世界竞技体育发展贡献中国经验和方案。运用文献资料、逻辑分析等研究方法,基于人类文明新形态内涵,梳理中国竞技体育在经济文明、政治文明、精神文明、社会文明和生态文明的实践,分析中国竞技体育发展与人类文明新形态理论耦合机制过程,两者在发展理念的创新性、发展方式的协调性、发展内容的绿色性、发展过程的开放性、发展成果的共享性等方面呈现出高度一致性,进而推动创立人类文明新形态历程。

科研实验融入材料成型及控制工程专业教学实践——双金属复合材料制备及分析

设计了一个基于双金属固-液熔铸法的钆/铜功能复合材料制备实验,并采用现代材料分析技术对钆/铜界面结合形貌进行观测和分析。通过将科研项目实验融入专业实践应用教学,学生可以锻炼材料制备成型和分析的能力,熟悉稀土金属钆和铜的反应特性,掌握熔铸复合成型设备、扫描电镜和金相显微镜的使用和分析方法,获得具有良好结合界面的双金属功能复合材料及其工艺参数,巩固所学专业知识,了解科学前沿,培养工匠精神,提升综合应用能力和科学素养。