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1.
Superplasticity is the phenomenon observed in certain materials that deform on the order of 300 to 500% under very low flow
stress, high temperature, and fine grain structure. Superplastically formed parts find application as both structural and
nonstructural components in simple and complex shapes. Mathematical models that describe the forming process with optimum
strain rate and tool geometry as input and pressure-time and thickness as output are essential for successful forming. This
article describes the deformation of a generalized cup assuming uniform thinning in the unsupported region. Closed form equations
are developed relating process parameters like pressure-time loading and thickness distribution to the shape of the cup and
material properties. The generalized cup formulation is applicable to the superplastic forming of domes, right circular cylinders,
deep slanted cups, and cones. 相似文献
2.
Grain structure and microtexture evolution during superplastic forming of a high strength AlZnMgCu alloy 总被引:2,自引:0,他引:2
Grain structure and microstructure evolution during superplastic forming were studied on an unrecrystallized sheet of a modified 7050 superplastic alloy. A SEM-based local orientation technique was used to cover a large number of (sub)grain boundaries in combination with other metallographic techniques. The gradual boundary misorientation and microtexture evolution during superplastic forming (SPF) confirmed that a continuous evolutionary process was occurring. There was no evidence of dynamic recrystallization at the stress maximum. The fraction of high angle boundaries increased rapidly once the mean misorientation reached a critical value. These and other results suggest that both grain boundary sliding (GBS) and dislocation slip were operative initially until the stress maximum was approached, beyond which GBS was predominant. The results of quantitative orientation distribution function (ODF) analyses suggest that grain rotation, which resulted in texture randomization, became important from slightly beyond the stress maximum through most of the stress-strain curve. 相似文献
3.
Firas S. Jarrar Mathias Liewald Philipp Schmid Alexander Fortanier 《Journal of Materials Engineering and Performance》2014,23(4):1313-1320
The superplastic forming process is used to form light weight components with complex features in one manufacturing step. However, the non-uniformity of the produced part thickness and the possibility of severe thinning are among its major disadvantages. The goal of this parametric study was to investigate feasible geometries for triangular channels to be manufactured by superplastic forming. The channels considered had sharp radii and served as secondary features extending along a circular path at the base of a shallow cup. An axisymmetric finite element model in ABAQUS? was used to simulate the forming process. Effects of the aspect ratios of both the cup and the triangular channel on the thickness distribution and the pressure profiles were investigated. An experimental setup was used for validating the simulation results for AA5083 at 500 °C. 相似文献
4.
回顾了王仲仁教授在超塑性研究领域的一系列重要研究成果。Sn-Pb共晶超塑性材料薄壁管复合加载实验表明,在复杂应力状态下超塑材料遵守Mises屈服准则,并与Tresca屈服准则也接近,给出了超塑材料在应变速率强化条件下的屈服轨迹;研究了超塑变形过程中晶粒和孔洞的长大规律及其对变形中流动应力的影响,导出了包含晶粒长大和孔洞长大影响的超塑性本构关系;提出了测定超塑材料摩擦系数的理论校准曲线和应变速率敏感性指数的变截面拉伸试验法;开发了带有动凸模的微机控制的1000kN超塑成形机,研制了当时国内最大的微机控制的5000kN超塑成形机;在模具型腔超塑成形研究方面,成功挤压了130型汽车连杆锻模,是迄今为止尺寸最大的超塑成形模具钢型腔。 相似文献
5.
MODELINGOFSUPERPLASTICFORMINGPROCESSFORALUMINUMALLOYSWITHSTRAINHARDENINGEFFECTY.N.KwonandY.-W.Chang(CenterforAdvancedAerospac... 相似文献
6.
Qizhen Li 《JOM Journal of the Minerals, Metals and Materials Society》2010,62(5):25-27
Superplastic forming is an appealing and affordable technique for manufacturing titanium-based structural parts. In this work,
circular samples with uniform initial thickness were formed superplastically using finite element modeling (FEM) and the formed
domes are analyzed to investigate their thickness distributions. The results indicate that the dome thickness is not uniform
and decreases from the apex to the periphery for each formed dome. The increase of the formed dome height results in the increased
thinning of the samples, and the increase of the ratio between the thickness at the dome apex and that at the dome periphery.
The predicted thickness distribution based on the Enikeev and Kruglov (E-K) model has a good agreement with the FEM result
for the formed domes with a large apex height, while it deviates from the FEM result for the formed domes with a small apex
height. A possible reason is the neglecting of the body force from the sample weight in the analytical E-K model. The obtained
knowledge will help guide the initial thickness design for the plate samples to realize the expected final thickness distributions. 相似文献
7.
8.
Pin-Hou Sun Horng-Yu Wu Hsin-Han Tsai Chih-Chao Huang Ming-Da Tzou 《Journal of Materials Processing Technology》2010,210(12):1673-1679
The deformation characteristics of a 0.6 mm-thick, fine-grained AZ31B Mg alloy sheet were investigated with the intention of reducing forming time during gas blow forming. The sheets were successfully deformed into hemispherical domes at 300, 370, and 420 °C under various pressurization profiles. The results show that the proposed pressurization profiles could achieve the goal of reducing forming time. A stepwise pressurization profile may be a suitable process at lower temperatures, whereas a constant or near constant pressure imposed during forming is a better method at higher temperatures. The pressurization profiles used in this study were not restricted to providing the optimum constant strain rate, which is often used in the traditional superplastic forming. Under the proposed pressurization profiles, maximum stress in the range of 23.5–45.6 MPa and resultant average strain rate in the range of 6.63 × 10−3 to 1.56 × 10−2 s−1 were imposed on the deforming sheet at the apex of the dome. The pressurization profile might not be one of the major factors influencing formability at the same forming temperature but it can significantly affect the forming time. Deviation of the bulged shape from the perfect sphere shape increased with increasing forming temperature. 相似文献
9.
An innovative method has been developed that replaces argon as the pressure source for superplastic forming. In this new process,
several solid materials are placed in a closed system to generate pressure and are capable of forming superplastic alloy plates
at specific temperatures. In the present study, the total pressures for the decomposition of ( CaCO3+ C) and MgCO3 have been theoretically calculated from thermodynamics. The results show that a pressure range of 40 to 396 psi can be obtained
for the ( CaCO3 + C) system between 850 and 1000 °, which is suitable for the superplastic forming of Ti-6Al-4V and Superdux 64 ( Nippon
Yakin Kogy Co., Ltd., Sanei Bridge, Kyobasi 1-5-8, Chyuoku, Tokyo 104, Japan) stainless steel. The pressure for MgCO3 system between 480 and 515 ° ranges from 78 to 160 psi, which is suitable for the superplastic forming of 8090 Al-Li and
7475 Al-Zn-Mg alloys. The calculated temperature dependence of pressure is consistent with the experimentally measured results.
Furthermore, the forming rates, wall thickness distributions, tensile properties, and microstructures of the four alloys after
forming have been shown to be very similar to those of conventional superplastic forming by argon pressurization. 相似文献
10.
Yingbing Luo Craig Miller George Luckey Peter Friedman Yinghong Peng 《Journal of Materials Engineering and Performance》2007,16(3):274-283
In this paper, the superplastic forming (SPF) potential of two fine-grained 5083 aluminum alloys were studied under various
stress states with the use of both high temperature tensile testing and pneumatic bulge testing. Experiments with the pneumatic
bulge test were performed at temperatures ranging from 475 to 525 °C under three different strain paths ranging from equi-biaxial
to approaching plane strain. The effects of temperature on total elongation, m-value, final thickness distribution, dome height, and cavitation were investigated for the case of uniaxial and equi-biaxial
stretching. Increased temperature in bulge forming was found to improve the thickness distribution in the formed parts, but
did not have a significant effect on dome height. The shape of the forming limit diagram (FLD) was found to be significantly
different than that of FLDs commonly used in room temperature stamping. Results indicate that determination of forming limits
in SPF cannot be represented with a simple FLD and additional metrics such as external thinning and internal cavitation need
to be considered to determine a material’s SPF potential.
This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati,
OH, October 15-19, 2006. 相似文献
11.
Jens Kappes Mathias Liewald Simon Jupp Christoph Pirchl Roman Herstelle 《Production Engineering》2012,6(3):219-228
Relatively low tooling costs, high design complexity coupled with low forming speeds make the superplastic sheet metal forming process attractive, especially for smaller lot sizes. Due to the relatively small lot size, the effort and budget for designing superplastic forming processes is usually limited (Kappes and Liewald in J Mater Sci Eng B1:472?C478, 2011). For this reason the tool design and corresponding pressure profiles in superplastic forming processes are often based on trial and error (Franchitti et al. in 11th international Esaform conference on material forming, 2008; Barnes in J Mater Eng Perform 4:440?C454, 2007). Consequently a process chain should be established to design superplastic forming processes accurately and efficiently. This paper deals with the process chain to form an aluminium part superplastically. At the beginning of the process chain, there is a new, developmental aluminium alloy sheet (AA5456, s0?=?1.6?mm) designed for superplastic forming supplied by Hydro Aluminium Rolled Products GmbH. The relevant material parameters of this sheet are then determined via pneumatic bulge testing with and without in situ measurement of strains. Using these experimentally determined parameters superplastic forming process can be simulated by FE modelling (PAM-STAMP 2G). Due to in situ measurement of strains during pneumatic bulging, the comparison of experiment and FE-simulation results over the whole pneumatic bulging process could be done. This comparison shows good correlation for the observed conditions. Furthermore a cylindrical cup was simulated, evaluated via determined isobar Superplastic Forming Limit Curve (at fracture) and finally formed by pneumatic bulging. Material characterisation of the bottom of this cup showed that excessive cavitation was observed as a result of the iron-silicon particles. Superplastic forming of a bracket usually formed out of AA5083 was also simulated using material parameters of AA5456. The simulation was able to show that this part is not able to be manufactured out of AA5456 under these forming conditions, which was confirmed by forming trials performed at ALU-SPF AG. 相似文献
12.
Deformation characteristics and cavitation during multiaxial blow forming in superplastic 8090 alloy
Horng-yu Wu Jiin-her Hwang Chui-hung Chiu 《Journal of Materials Processing Technology》2009,209(4):1654-1661
This work examined the effect of multiaxial stress on deformation characteristics of a superplastic aluminum alloy 8090 by deforming the sheet into a die with a cylindrical cavity. Several interrupted tests were performed to bulge the sheets to various depths for different strain rates, the formed parts were utilized to evaluate the deformation status, thickness distribution, local strain states, and cavitation. It was found that evolution of cavity volume fraction with forming time could be related to the thinning behavior of the deformed sheet during forming. Decrease in cavity volume fraction at the central region was observed in the later stage of forming as the thickness of the deformed sheet remained constant for all test forming rates. 相似文献
13.
Pin-hou Sun Horng-yu Wu Wei-song Lee Shyh-hung Shis Jau-yuean Perng Shyong Lee 《International Journal of Machine Tools and Manufacture》2009,49(1):13-19
Despite its importance for industrial applications, the effect of lubrication on the cavitation behavior of superplastic materials has been given little attention. In this paper, a series of experiments were performed regarding bulging superplastic 5083 Al alloy sheet into dies with a cylindrical (cup) and rectangular (pan) die cavity for forming with and without lubrication, the formed parts were then evaluated to determine the effect of lubrication on the cavitation level evolution, thickness distribution, and void distribution. It was found that void shrinkage took place in the overlaid region for both forming with and without lubrication. The maximum void volume fraction could be effectively reduced for forming with lubrication; however, reductions in the maximum void volume fractions for cup forming were less significant than those for pan forming. 相似文献
14.
J. M. Boileau P. A. Friedman D. Q. Houston S. G. Luckey 《Journal of Materials Engineering and Performance》2010,19(4):467-480
Magnesium sheet is typically produced for commercial applications with the traditional DC-ingot casting method. As a result
of the hexagonal close-packed crystallographic structure in magnesium, multiple rolling passes and annealing steps are required
to reduce the thickness of the ingots. Thus, high fabrication costs characterize the creation of magnesium sheet suitable
for common forming operations. Recently, continuous casting (CC) technology, where molten metal is solidified directly into
sheet form, has been applied to magnesium alloys; this method has shown the potential to significantly reduce the cost of
fabricating magnesium sheet alloys. In order to understand the viability of the CC process, a study was conducted to investigate
the superplastic potential of alloys produced by this method. This study focused on AZ31B Mg that was continuously-cast on
twin-roll casters from three different suppliers. These three materials were compared with a production DC-cast AZ31B alloy
in terms of microstructure, elevated-temperature tensile properties, and superplastic forming response. The data from this
study found that microstructural features such as grain size and segregation can significantly affect the forming response.
Additionally, the CC alloys can have equivalent or superior SPF response compared to DC-cast alloys, as demonstrated in both
elevated temperature tensile tests and superplastic forming trials using a rectangular pan die. 相似文献
15.
Mohammad A. Nazzal Marwan K. Khraisheh 《Journal of Materials Engineering and Performance》2007,16(2):200-207
The current available models describing superplastic deformation do not account for a number of important characteristics,
leading to the current limited predictive capabilities of deformation and failure. In this work, the effects of cavitation
and stress state on deformation stability during superplastic forming are investigated using Finite Element simulations. The
simulations are performed using constant strain rate forming and using a proposed optimization approach based on a multiscale
failure criterion that accounts for stress state, geometrical necking, and microstructural evolution including grain growth
and cavitation. The simulations are conducted for the superplastic copper-based alloy Coronze-638 and the superplastic aluminum
alloy Al-5083 which are known to develop significant cavitation during deformation. The results clearly show the importance
of accounting for microstructural evolution during superplastic forming, especially when the state of stress is biaxial. Furthermore,
the results highlight the effectiveness of the proposed optimization technique in reducing the forming time and maintaining
the integrity of the formed parts.
This article was presented at the AeroMat Conference, International Symposium on Superplasticity and Superplastic Forming
(SPF) held in Seattle, WA, June 6-9, 2005. 相似文献
16.
17.
Y. -M. Hwang H. S. Lay J. C. Huang 《International Journal of Machine Tools and Manufacture》2002,42(12)
The purpose of this paper is to explore the plastic deformation behavior of the sheet during blow-forming of a superplastic sheet into an ellip-cylindrical closed-die by the finite element method. A finite element commercial code “DEFORM” is used to carry out the simulations and calculate the pressurization profile and sheet thickness distribution during the blow-forming process. A pressure control algorithm is proposed to keep the maximum strain rate in the deformation zone of the sheet equal to the target value, which corresponds to the highest m value of the material being superplastically formed. The effects of various forming conditions, such as the friction coefficient between the sheet and die and the aspect ratio of the die, on the forming pressure and thickness distribution of the product are discussed. Experiments using 8090 Al–Li sheets on superplastic blow-forming in an ellip-cylindrical closed-die are also carried out. The theoretical predictions of thickness distribution of the product are compared with experimental results. 相似文献
18.
壁厚分布对薄壁构件的结构性能有重要影响。本文研究超塑成形件壁厚分布的预测技术,实现了超塑成形过程的有限元数值模拟的成形件厚度分布曲线的自动预测,以半球壳和矩形盒成形为例,为自由胀形和约束胀表两种情形形件厚度变化进行了分析,预测结果与实验数据吻合。 相似文献
19.
In a previous work, an optimization approach for superplastic forming based on a multiscale stability criterion, and yielding
a variable strain rate loading path instead of the commonly used constant strain rate one, was presented. The approach was
experimentally validated using the AZ31 magnesium alloy, where it was proven effective in reducing forming time without sacrificing
the uniformity of deformation. In this work, the validation process is taken to a different level, where the post-superplastic
forming mechanical properties, often ignored in superplasticity, become the criteria. The material is first superplastically
deformed under uniaxial loading at an elevated temperature, following both loading paths; constant strain rate versus optimized
variable strain rate. Thereafter, specimens extracted from the deformed material are tested at room temperature to evaluate
the changes in mechanical properties, in reference to those of the as-received material. The results emphasize on the necessity
of a combined forming and post-forming analysis in optimizing the superplastic forming process.
This article was presented at the AeroMat Conference, International Symposium on Superplasticity and Superplastic Forming
(SPF) held in Baltimore, MD, June 25-28, 2007. 相似文献
20.
钛合金激光焊缝是非理想的针状组织,对其超塑性变形机理的研究可进一步推进钛合金LBW/SPF技术的实际应用,也对材料成形机理的发展具有一定意义.研究结果表明,TC4钛合金激光焊接试样具有良好的超塑性变形能力,在变形过程中,焊缝发生两次重要的组织转变,即针状组织片层化和片层组织等轴化的组织转变.片层组织在应力作用下,通过断裂、解体和等轴化的过程而转变成等轴晶粒.片层断裂的主要机制是动态再结晶和应力挤压作用;片层解体的主要机制是晶界滑动和转动作用,接头组织的塑性流动机理为晶粒滚动和晶界滑动机理. 相似文献