锻压技术

预变形对6011铝合金薄壁管高温均匀变形的影响

英文标题：Effect of pre-deformation on high temperature uniform deformation for AA6011 aluminum alloy thin-walled tubes

作者：杨松1 郑凯伦2 苑世剑1

分类号：TG316.8

出版年,卷(期):页码：2023,48(5):7-15

摘要：

研究了不同初始预变形量下高强铝合金管的高温均匀变形能力，以模拟实际复杂异形管件热气胀成形中预弯曲与预成形工序对后续气胀工序的影响。利用DIC测试手段，开展了不同初始预变形量下铝合金试样在温度为400和450 ℃、应变速率为0.01和0.1 s-1的典型热气胀工艺参数条件下的高温拉伸实验。获得的真实应力-真实应变曲线表明：初始预变形量的引入导致材料高温变形过程中发生明显的软化现象，流动应力下降趋势随着初始预变形量的增加而显著增加；利用Spatio-temporal方法对DIC获得的试样应变场进行处理，获得不同条件下的均匀应变值，均匀应变值由无初始预变形量时的0.28下降至初始预变形量为15%时的0.15；相比传统Nakajima方法，本方法能够准确获得厚度突变时刻的应变值，而断裂前时刻的均匀应变水平略低，获得的结果更保守。该研究能够为实际多工步热气胀的预成形提供初始预变形量设计边界，满足热气胀终成形零件的均匀变形要求。

The uniform deformation capacity at high temperature of high strength aluminum alloy tubes with different initial pre-deformation amounts was investigated to simulate the influence of pre-bending and pre-forming processes on the subsequent gas bulging process in the hot gas bulging forming of actual complex special shape tubes. The digital image correlation (DIC) testing method was used to conduct high temperature tensile tests on aluminum alloy specimens with different initial pre-deformation amounts under typical hot gas bulging process parameter conditions of the temperatures of 400 and 450 ℃ and the strain rates of 0.01 and 0.1 s-1. The obtained true stress-true strain curves show that the introduction of initial pre-deformation amount leads to a significant softening of materials during the high temperature deformation process and the decreasing trend of flow stress increases significantly with the increasing of initial pre-deformation amount. The strain field of the specimen obtained by DIC was processed using the Spatio-temporal method to obtain uniform strain values under different conditions, the uniform strain value decreased from 0.28 without initial pre-deformation amount to 0.15 with the initial pre-deformation amount of 15%. Compared to the traditional Nakajima method, this method is able to obtain accurate strain values at the moment of sudden change for thickness, and the uniform strain level at the moment before fracture is slightly lower, the obtained results are more conservative. This study can provide initial pre-deformation amount design boundaries for the preforming of practical multi-step hot gas bulging to meet the uniform deformation requirements of final formed parts by hot gas bulging.

基金项目：

国家自然科学基金资助项目（5200052525）

作者简介：杨松（1984-），男，博士，高级工程师，E-mail：20B909114@stu.hit.edu.cn

参考文献：

[1] Yuan S J. Fundamentals and processes of fluid pressure forming technology for complex thin-walled components [J]. Engineering,2021, 7(3):358-366.

[2] Sartkulvanich P, Li D, Crist E, et al. Influence of superplastic forming on reduction of yield strength property for Ti-6Al-4V fine grain sheet and Ti-6Al-4V standard[J]. Materials Science Forum, 2016, 838-839:171-176.

[3] Zheng K L, Zheng J H, He Z B, et al. Fundamentals, processes and equipment for hot medium pressure forming of light material tubular components [J]. International Journal of Lightweight Materials and Manufacture,2020, 3（1）:1-19.

[4] Dykstra W C, Pfaffmann G D, Wu X. Method of forming a tubular blank into a structural component and die therefor [P]. United States Patent:US7269986B2 ,2002-01-10.

[5] Wu X, Hao H, Liu Y, et al. Elevated temperature formability of some engineering metals for gas forming of automotive structures[J]. Journal of Materials and Manufacturing, 2001, 110: 1045-1056.

[6] Reuther F, Mosel A, Freytag P, et al. Numerical and experimental investigations for hot metal gas forming of stainless steel X2CrTiNb18 [J]. Procedia Manufacturing，2019, 27: 112-117.

[7] Paul A, Strano M. The influence of process variables on the gas forming and press hardening of steel tubes [J]. Journal of Materials Processing Technology，2016, 228:160-169.

[8] Yi H K, Pavlina E J, Van Tyne C J, et al. Application of a combined heating system for the warm hydroforming of lightweight alloy tubes [J]. Journal of Materials Processing Technology，2008, 203 (1-3): 532-536.

[9] Lee M Y, Sohn S M, Kang C Y, et al. Effects of pre-treatment conditions on warm hydroformability of 7075 aluminum tubes[J]. Journal of Materials Processing Technology,2004, 155-166: 1337-1343.

[10] Maeno T, Mori K, Unou C. Optimisation of condition in hot gas bulging of aluminium alloy tube using resistance heating set into dies [J]. Key Engineering Materials,2011, 473: 69-74.

[11] He Z B, Fan X B, Shao F, et al. Formability and microstructure of AA6061 Al alloy tube for hot metal gas forming at elevated temperature [J]. Transactions of Nonferrous Metals Society of China,2012, 22(2): 364-369.

[12] Zhang R Q, Shi Z S, Shao Z T, et al. An effective method for determining necking and fracture strains of sheet metals [J]. MethodsX, 2021, 8:101234.

[13] Li X J, Xu M, Zhang Z Q. Hot damage evolution in a high strength aluminum alloy during hot forming: A study using the Gurson-Tvergaard-Needleman model [J]. Journal of Materials Research and Technology,2021,14:1366-1376.

[14] Feng B, Gu B, Li S H. Cryogenic deformation behavior and failure mechanism of AA7075 alloy sheets tempered at different conditions [J]. Materials Science & Engineering A,2022, 848:143396.

[15] GB/T 24171.2—2009, 金属材料薄板和薄带成形极限曲线的测定第2部分: 实验室成形极限曲线的测定[S].

GB/T 24171.2—2009, Metallic materials—Sheet and strip—Determinations of forming limit curves—Part 2: Determinations of forming limit curves in laboratory[S].

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