筒形件强力旋压变形机理的有限元分析

本文通过建立筒形件强力旋压的力学模型,运用三维弹塑性有限元对强力旋压过程进行了计算,得到了旋压过程的应力场和应变场分布。在此基础上,对筒形件强力旋压的变形机理进行了分析,并将计算结果与实测结果进行了比较,两者吻合较好     

简形件强力旋压发展过程及其现状分析

通过对筒形件强力旋压发展过程的回顾和国内外技术现状的分析。进一步加深了对该加工工艺的了解并探寻新的发展方向。目前．普通简彤件强力旋压工艺已经相当成熟，而带有纵向内筋的筒形件强力旋压工艺还相对落后。因此，进一步深入开展带内筋筒形件强力旋压工艺成形机理和变形特点的研究，有着重要的理论意义和实际应用价值。     

铝合金强力旋压变形区温度变化规律

建立了铝合金薄壁精密筒形件三旋轮强力旋压变形区温度变化数学模型,计算并分析了变形区温度变化规律及其对旋压工艺的影响。研究结果表明:多道次强力旋压时,变形区温度最高升温约160℃,变形区金属的变形抗力明显降低约40 MPa;在分析变形区温度变化对壁厚减薄率影响规律的基础上,提出了壁厚减薄率一致性的概念,为薄壁高精度铝合金筒形件旋压提供了理论参考。旋压变形区温度变化导致旋压坯料在厚度方向上产生热膨胀,最大热膨胀量达85μm,名义减薄率与实际减薄率不一致,壁厚减薄误差率达12%。     

筒形件强力旋压的有限元模拟

现代旋压技术是广泛应用于航空、航天、军工等金属精密加工技术领域的一种先进塑性成形工艺。强力旋压是旋压技术的一个重要组成部分,对强力旋压的受力状态进行深入研究将有助于了解旋压工艺的特点和可能出现的缺陷。本文用弹塑性有限元法对强力旋压过程进行了模拟,获得了强力旋压稳定状态下应力应变的分布规律,解释了强力旋压的变形机理和隆起等缺陷产生的原因。     

旋压变形数值模拟中局部加载卸载问题的处理

此文介绍了旋压加工数值模拟中遇到的局部加载卸载问题的处理方法，并对筒形件强力旋压过程进行了数值模拟，求得了变形区应变的分布，理论计算结果与变形实际和实测结果完全吻合。     

筒形件强力旋压的刚塑性有限元分析

筒形件强力旋压是当代的一种重要生产工艺过程。本文建立了筒形件强力旋压的平面变形力学模型，通过刚塑性有限元分析，获得了正旋工艺和反旋工艺的塑性流动速度场，以及应变和应变速率的分布。塑性流动模型与网格实验结果在趋势上得到较好的吻合。     

筒形件强力旋压发展过程及其现状分析

通过对筒形件强力旋压发展过程的回顾和国内外技术现状的分析,进一步加深了对该加工工艺的了解并探寻新的发展方向。目前,普通筒形件强力旋压工艺已经相当成熟,而带有纵向内筋的筒形件强力旋压工艺还相对落后。因此,进一步深入开展带内筋筒形件强力旋压工艺成形机理和变形特点的研究,有着重要的理论意义和实际应用价值。     

基于数值模拟的小应变差筒形件旋压成形方法研究

为了获得变形均匀的筒形件,提出采用有限元数值模拟方法对错距旋压、等距旋压和对轮旋压三种强力旋压成形工艺方案进行分析,介绍了三种强力旋压成形工艺方法及其原理,并制定了相应的成形工艺方案。以20钢筒形件为研究对象,采用MSC.MARC有限元软件,对三种不同的强力旋压成形过程进行了数值模拟。结果表明,旋压成形后工件的内外表面存在一定的应力及应变差;采用对轮旋压所获得筒形件内外表面应力应变差远小于错距旋压及等距旋压,采用等距旋压成形时筒形件内外表面应力应变差最大。     

金属筒形件强力反旋变形过程的数值模拟分析

为了确定更为符合实际的筒形件强力旋压工艺参数的选用原则,利用有限元软件Abaqus/Explicit准静态模块,对一次减薄成形的工艺,不同工艺参数下筒形件两旋轮反旋旋压过程进行了动态模拟、变形以及应力应变的分析.分析表明:强力旋压毛坯件的变形流动主要是轴向变形,影响成形质量的因素主要是成形过程中的径向变形和切向变形.当旋轮圆角半径r=15mm,旋轮工作角α=30°时,金属旋压件的径向变形和切向变形比较合理,既容易顺利进行旋压成形又不易引起失稳现象,为实际加工旋轮的参数选择提供了依据.     

难变形薄壁筒形件强力旋压组织演化研究进展

难变形材料薄壁筒形件强力旋压是一个涉及多场、多因素和多道次的复杂成形过程,导致材料在成形过程中微观组织演化历程复杂,而筒形件的微观组织决定了其服役性能。因此,研究难变形材料薄壁筒形件强力旋压微观组织演变机制与调控对实现该薄壁件组织性能一体化控制具有重要意义。从试验、宏观和微观尺度仿真和缺陷分析等方面,综述难变形材料筒形件强力旋压成形微观组织演变的国内外研究现状,并阐述目前存在的问题和发展方向。     

挤压AZ31B镁合金板材中温轧制变形中的组织变化

在220℃的温度条件下,对AZ31B挤压板材进行单道次轧制变形,通过光学显微镜(OM)和扫描电镜(SEM)观察了中温变形AZ31B微观组织演变。结果表明,在中温变形的初始阶段,孪生为主要的变形机制,随变形量的增加,变形畸变能的积聚以及孪晶间的相互作用,导致了动态再结晶的形核与长大,在大的变形量条件下,孪生、形变带和动态再结晶共同作用,使变形得以进行。     

Deformation resistance of Fe-Mn-V-N alloy under different deformation processes

The deformation resistance of Fe-Mn-V-N alloy under different deformation conditions was investigated by hot compression method on thermal simulator.Effects of deformation degree, deformation temperature,and strain rate on deformation resistance were analyzed.The results show that when other conditions are constant,the deformation resistance increases with the increase in deformation degree and strain rate and decreases with the increase in deformation temperature. At the same time, the mathematical model of deformation resistance for Fe-MnV-N alloy was established by 1 stOpt software using the Levenberg-Marquardt optimization algorithm carried out on the fitting of regression coefficients, which has higher fitting precision.     

Subtransus deformation mechanisms of TC11 titanium alloy with lamellar structure

Isothermal compression tests are applied to study the deformation mechanisms of TC11 titanium alloy with lamellar structure under the deformation temperature range of 890-995 oC and strain rate range of 0.01-10 s-1.According to the flow stress data obtained by compression tests,the deformation activations are calculated based on kinetics analysis of high temperature deformation,which are then used for deformation mechanism analysis combined with microstructure investigation.The results show that deformation mechanisms vary with deformation conditions:at low strain rate range,the deformation mechanism is mainly dislocation slip;at low temperature and high strain rate range,twinning is the main mechanism;at high temperature and high strain rate range,the deformation is mainly controlled by diffusion of β phase.     

冷拉珠光体钢丝的组织演变及性能变化

研究了冷拉70钢的组织演变和性能变化。结果表明，随应变量的提高，70钢的抗拉强度和硬度均提高。抗拉强度、硬度与真应变之间呈线性关系。利用场发射扫描电镜（FEM）对70钢冷拉变形过程中的组织演变进行了分析。变形过程中珠光体团发生转动，取向与拉拔轴线趋于一致，渗碳体经历了弯曲、剪切、拉伸等变形，形变量较大时渗碳体大量溶解。     

冷拉珠光体钢丝的组织演变及性能变化

研究了冷拉70钢的组织演变和性能变化。结果表明,随应变量的提高,70钢的抗拉强度和硬度均提高,抗拉强度、硬度与真应变之间呈线性关系。利用场发射扫描电镜(FEM)对70钢冷拉变形过程中的组织演变进行了分析。变形过程中珠光体团发生转动,取向与拉拔轴线趋于一致,渗碳体经历了弯曲、剪切、拉伸等变形,形变量较大时渗碳体大量溶解。     

Hot deformation behavior of rare earth magnesium alloy without pre-homogenization treatment

The behavior and structure evolvement of as-cast Mg-Gd-Y-Nd-Zr magnesium alloy during the hot deformation process were discussed.The flow stress behavior of magnesium alloy over the strain rate range of 0.002-1 s~(-1) and the temperature range of 573-723 K was researched on Gleeble-1500D hot simulator under the maximum deformation degree of 60%.The experimental results show that the relationship between stress and strain is obviously affected by the strain rate and deformation temperature.The important s...     

关于焊接应力变形两个问题的进一步探讨

讨论了焊缝是否存在压缩塑性变形问题和拉达伊D应力应变原理图存在的问题。指出刚刚经历熔化—凝固过程的焊缝不存在压缩塑性变形 ,一直承受拉伸塑伸变形。拉伸塑性变形区的范围要比拉达伊D的原理图上给出的大得多 ,对拉达伊D的原理图进行全面修改 ,提出新的焊接热应力应变原理图。在新原理图中 ,三组曲线分别是升温—降温、压缩—拉伸和拉伸弹性—塑性变形的分界线。将等温线所处的温度明确为熔点 ,它包围的区域为熔池。取消弹性卸载区的提法 ,改为弹性变形区。整个焊接板由弹性变形区、压缩塑性变形区、拉伸塑性变形区和熔池组成。     

Deformation characteristic of semi-solid ZCuSn10 copper alloy during isothermal compression

The compression tests were carried out by Gleeble-1500 thermo-mechanical simulator with samples of semi-solid ZCuSn10 alloy prepared by strain-induced melt activation(SIMA) process. The original microstructure and the deformation temperature of semi-solid ZCuSn10 alloy are different. The strain is 0.2, and the strain rate is 1 s~(-1) for the compression test. The results show that when the semi-solid ZCuSn10 alloy was prepared by SIMA process, the liquid fraction of semi-solid microstructure increases, and the solid grain is smaller,more uniform and more inclined to be round as the rolling pre-deformation increasing. The results also indicate that the deformation resistance of ZCuSn10 alloy in semi-solid state decreases with the deformation temperature increasing or the solid fraction of original microstructure decreasing. The stress–strain curves of the isothermal compression can be divided into quasi-elastic deformation stage and plastic deformation stage, and there are three deformation zones in the samples after isothermal compression, namely the difficult deformation zone, the large deformation zone and the free deformation zone. In the three deformation zones, the main deformation mechanism is flow of liquid incorporating solid particles(FLS)mechanism, plastic deformation of solid particles(PDS)mechanism and liquid flow(LF) combining with FLS mechanism, respectively.     

Inference of plastic deformation in weldment with parallel cracks from infrared thermography

Tensile tests are carried out by using the welded plate with two parallel cracks. The effects of the residual stress, the hardened zone by welding and the interaction between cracks on the plastic deformation near cracks and the crack opening displacement are examined by the experiment as well as the elasto plastic finite element analysis. A new technique for evaluating nondestructively the plastic deformation near cracks by using the infrared thermography is proposed. The heated region and the temperature rise measured by the thermography are compared with the plastic zone and the work of plastic deformation obtained by the analysis. The validity and the limitations of the application of the infrared thermography to the evaluation of the plastic deformation are discussed.     

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借助非线性有限元软件Marc,采用弹塑性有限元方法对十八辊轧机辊系进行了模拟,计算模型对辊系的弹性变形与带钢的弹塑性变形按照接触问题进行耦合分析。利用此模型,得出了轧制力对辊系弯曲变形的影响以及辊系弯曲变形沿轧件宽度方向的分布,并分析了轧机工作辊的不同方向弯曲变形情况,由对计算结果的分析可以为该轧机的辊系设计提供理论依据。