共查询到19条相似文献,搜索用时 234 毫秒
1.
粉末多孔体烧结材料闭式模锻塑性成形致密研究 总被引:3,自引:3,他引:0
通过对粉末冶金预成彤烧结坯闭式模锻塑性成形实验,研究了不同初始相对密度、不同高径比、不同摩擦等条件对成形致密的影响规律,探讨了粉末锻造镦粗、复压两阶段对成形致密的不同作用,同时对实验结果进行分析与比较.结果表明:闭式模锻成形时延长镦粗阶段,有利于提高致密化效果,但镦粗并不能使预成形坯完全致密;复压比镦粗阶段致密困难,但致密化速率却明显提高,能至近全致密. 相似文献
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不同初始条件下粉末锻造镦粗成形致密过程的数值模拟 总被引:1,自引:1,他引:0
运用有限元软件MSC.MARC对多孔体粉末烧结材料锻造镦粗成形致密过程进行了数值模拟,研究了不同初始条件(相对密度、高径比、摩擦因子)对粉末锻造成形致密规律及致密机制的影响,并对其结果进行了分析,为预成形坯和模具的优化设计提供理论依据. 相似文献
3.
运用粉末冶金成形技术对高纯钼粉材料进行制备、烧结,对钼粉未烧结体进行镦粗成形,研究了在不同初始条件(相对密度、高径比、摩擦条件)下钼粉末烧结体成形致密规律和变形特性,为钼传统的制备技术的改良、预成形坯和模具的优化设计提供大量实验数据. 相似文献
4.
徐平姣 《锻压装备与制造技术》2003,38(3):43-45
选择典型的镦粗工艺对粉末烧结坯的致密与成形行为和规律进行了研究,提出了多孔材料的致密模型并简要介绍了多孔材料的塑性理论。然后,采用有限元法模拟了不同镦粗压下量的烧结坯的致密与成形过程。密度与等效应变分布的一致性表明,烧结坯的致密强烈依赖于材料的塑性变形。 相似文献
5.
基于微观组织优化的锻造工艺预成形及毛坯形状优化设计 总被引:3,自引:0,他引:3
以锻件晶粒尺寸细小均匀为目标,以预成形形状设计为对象,提出了锻造成形过程微观组织优化设计方法,构建了晶粒尺寸、锻件形状子目标函数以及无量纲化的总目标函数,确定了预成形形状作为优化过程的设计变量;给出了优化设计的具体步骤,采用微观遗传算法和有限元模拟方法开发了基于预成形设计的锻造过程微观组织优化程序;并对典型的圆柱体镦粗进行了面向微观组织优化的预成形设计,给出了能够获得具有良好微观组织的镦粗成形预成形模具型腔形状。通过分析不同高径比的初始毛坯形状对微观组织优化目标函数值的影响,给出了较为合理的初始毛坯形状高径比取值范围。 相似文献
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邱媛媛 《锻压装备与制造技术》2022,(5):90-93
在金属塑性成形过程中,摩擦广泛存在,摩擦对零件的变形均匀程度和热量产生有极其重要的影响。本文建立了热-力耦合的镦粗有限元模型,并着重分析了不同高径比下不同摩擦系数对坯料镦粗鼓的影响规律。结果表明:摩擦系数会显著影响不同高径比坯料镦粗鼓的大小。 相似文献
10.
齿轮粉末锻造的变形力分析及其过程数值模拟 总被引:1,自引:1,他引:0
应用粉末烧结材料广义塑性理论,分析和计算了齿轮粉末锻造成形镦粗、复压的变形力和密度,运用MARC有限元数值模拟了粉末锻造齿轮的成形过程,讨论了数值模拟和理论计算结果。 相似文献
11.
X. Q. Zhang Y. H. Peng X. Y. Ruan M. Q. Li S. C. Wu 《Journal of Materials Engineering and Performance》2000,9(2):164-169
Workability limits must be considered when designing powder metallurgy (PM) forging processes. This research successfully
applied the general upsetting experiment method to the deformation of porous materials. Based on the plastic theory of porous
materials, the compressible rigid plastic finite element method is used to simulate the deformation processes of cold upsetting
of disks and rings for porous metal materials with a full account of contact friction boundary conditions, the height-to-diameter
ratio, the initial relative density, and the die and workpiece geometry. Furthermore, a successful analysis of the cold forging
process results in the prediction of the stress, the strain, and the density field. By coupling with the ductile fracture
criterion, which is a strain-based criterion obtained by Lee and Kuhn, possible defects leading to material failure have been
checked. This research reveals that larger height to diameter and a lesser friction factor can delay the local strain locus
to intersect with the Lee and Kuhn’s fracture line and restrain formation of the surface crack. Meanwhile, it reveals that
the initial relative density has only a very small influence on the strain to fracture in compression, and it shows the forming
behavior of the ring and disk with the curved die. According to Lee and Kuhn’s results, the calculated results agree well
with the experimental results. 相似文献
12.
粉末烧结材料闭式模锻充满过程实验研究 总被引:1,自引:0,他引:1
通过烧结紫铜圆柱体试样闭式模锻实验,研究了充满模腔过程的变形与致密规律。得出了烧结紫铜闭式模锻充满模膜过程中,轴向应变与相对密度呈线性关系,模锻变形力与相对密度呈幂函数关系,为粉末烧结材料闭式模锻工艺设计提供了实验依据。 相似文献
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1.~nonNUInericalmodellingbythefiniteelement(FE)methodhasbecomeaneffectiveandeconomyicmeansforsimulatingmetalfoeingprocesses.However,accuratemodellingdemandsthecorrectdefinitionandinputsofthedataforthethermalandphysicalpIDPertiesoftheworkpieceandtoolmaterials,theboUndaryconditionsattheworkpiece--toolinterfaceandinotherareas,inadditiontoappropriatemeshgenerationandnumericalsolutions.Althoughmostofthematerialdataareavailable,thedataforinterfacialheattransferandfrictionconditions,Whichhavesubst… 相似文献
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In the present paper cold forging of cylindrical specimens is studied. Tree types of Cr-Ni steels were used for failure limit diagrams determination. The different specimen geometries were tested with different friction conditions between tools and specimen involving concentrically grooved tool platens and smooth platens to generate different deformation conditions at the equatorial surface of specimens. Specimens with v-shaped axial notches with different depths were used.
Experimentally determined strain paths at free surface and at notches were used for theoretical calculations of the stress state at the free surface and notch, void growth in the material and failure limit. These calculations were based on a crack initiation model and void growth model which takes both the influence of state of stress and effective strain into account.
A satisfactory agreement was found between experimental determined failure limits and theoretical calculations based on experimental strain paths. 相似文献
16.
针对钼的变形抗力大、韧性差、脆性明显以及高温氧化等特点,本文采用了等温锻造与粉末包套锻造相结合的工艺来提高钼制品的性能。运用DEFORM-2D软件对钼粉烧结体近等温包套镦粗成形过程进行数值模拟,研究不同工艺参数对坯料致密度、变形均匀性和表面平整度的影响规律。近等温包套锻造工艺对钼粉烧结体有较好的致密效果,锻后坯料接近全致密,且密度分布较均匀。随锻造温度的升高,坯料的平均相对密度差异较小,密度分布均匀性逐渐变好。变形速度对坯料变形的影响不显著。随摩擦系数的增加坯料平均相对密度逐渐增大,密度分布均匀性变差,且坯料的平整度降低,外观质量变差。通过正交试验分析得知,锻造温度对平均相对密度和变形均匀性影响最显著,摩擦系数是影响坯料平整度的主要因素。 相似文献
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Wogaso Desalegn M. J. Davidson A. K. Khanra 《Journal of Materials Engineering and Performance》2014,23(8):3058-3068
In this study, ring compression tests and finite element (FE) simulations have been utilized to evaluate the friction factor, m, under different lubricating conditions for powder metallurgical (P/M) Al-4%Cu preforms. A series of ring compression tests were carried out to obtain friction factor (m) for a number of lubricating conditions, including zinc stearate, graphite, molybdenum disulfide powder, and unlubricated condition. FE simulations were used to analyze materials deformation, densification, and geometric changes, and to derive the friction calibration curves. The friction factor has been determined for various initial relative densities and different lubricating conditions, and a proper lubricant for cold forging of P/M Al-4%Cu preforms is found. Studies show that the use of lubricants has reduced the friction. However, increase in the number of pores in the preforms leads to excessive friction. The FE simulation results demonstrate a shift in the neutral plane distance from the axis of ring specimen, which occurred due to variations in the frictional conditions and initial relative densities. The load requirement for deformation, effective stress, and effective strain induced, and bulging phenomena obtained by FE simulations have a good agreement with the experimental data. 相似文献
18.
Deformation characteristics and fracture mechanisms during the cold forging of metal powder preforms
《International Journal of Machine Tool Design and Research》1986,26(4):369-384
The paper reports on an investigation into the various aspects of cold forging of iron powder preforms which have been compacted and sintered from atomised iron powder. The influence of particle size, compacting pressure, sintering temperature and forging parameters on relative density of the preform was investigated. Experiments were conducted and measurements were made on the development of barrelling and strain variations at the free surface. Cracks were also observed at the free surface of the perform. The deformation characteristics and fracture mechanism is discussed critically to illustrate the interaction of various parameters involved and the results are presented graphically. 相似文献
19.
D. Shahriari A. Amiri M. H. Sadeghi 《Journal of Materials Engineering and Performance》2010,19(5):633-642
In hot forging of Nimonic 115, it is desirable to determine friction coefficients. Changing magnitudes of temperature and
type of lubricant at the surface of the workpiece and dies influence friction coefficient. This paper describes an experimental
investigation of friction under hot forging conditions using the ring compression test. The 3D FEM simulations were used to
derive the friction calibration curves and to evaluate material deformation, geometric changes, and load-displacement results.
A series of ring compression tests were carried out to obtain friction coefficients for a number of lubricants including mica
plate, glass powder, graphite powder, and dry condition. The experiments show how the variations in temperature at the interface
affected frictional behavior. On the basis of these results, mica is recommended for hot forging of Nimonic 115 and its friction
coefficient is approximately 0.3. 相似文献