鋁合金由于具有密度低、耐腐蝕高、比強(qiáng)度高等特點(diǎn)，近來(lái)作為重要的輕質(zhì)材料在汽車(chē)制造中被廣泛使用。破裂、起皺和回彈是板料沖壓成形中的三大主要質(zhì)量缺陷。鋁合金和鋼板相比，總伸長(zhǎng)率更小，在室溫下鋁合金的成形性比鋼板的差，更容易出現(xiàn)破裂現(xiàn)象。準(zhǔn)確模擬板料成形過(guò)程中的破裂現(xiàn)象，對(duì)成形工藝和模具設(shè)計(jì)具有重要意義，金屬材料的斷裂主要可以分為脆性斷裂和韌性斷裂，多數(shù)鋁合金屬于韌性斷裂。韌性斷裂準(zhǔn)則從細(xì)觀損傷力學(xué)角度出發(fā)，認(rèn)為材料內(nèi)部孔洞的缺陷在外力作用下不斷地形核、長(zhǎng)大并聚合,終引起了材料的損傷，可以較好地預(yù)測(cè)塑性差的板料成形性能。
Aluminum alloy is widely used in automobile manufacturing as an important lightweight material because of its low density, high corrosion resistance and high specific strength. Cracking, wrinkling and springback are the three main quality defects in sheet metal stamping. The total elongation of aluminum alloy is smaller than that of steel plate. At room temperature, the formability of aluminum alloy is worse than that of steel plate, and it is more prone to fracture. Accurately simulating the fracture phenomenon in the sheet metal forming process is of great significance to the forming process and die design. The fracture of metal materials can be divided into brittle fracture and ductile fracture, and most aluminum alloys belong to ductile fracture. From the perspective of meso damage mechanics, the ductile fracture criterion considers that the defects of holes in the material continuously nucleate, grow and aggregate under the action of external force, and finally cause the damage of the material, which can better predict the formability of sheet metal with poor plasticity.
一、影響韌性斷裂的因素很多，主要可以分為兩大類(lèi)。
1、 There are many factors affecting ductile fracture, which can be divided into two categories.
1.一類(lèi)與材料相關(guān)，如應(yīng)變硬化水平、空穴體積分?jǐn)?shù)和相粒子組成等；
1. One is related to materials, such as strain hardening level, hole volume fraction and phase particle composition;
2.二類(lèi)與工藝相關(guān)，如應(yīng)變速率、摩擦和成形溫度等。
2. Class II is process related, such as strain rate, friction and forming temperature.

二、鋁合金拉伸試樣斷口兩種類(lèi)型的韌窩
2、 Two types of dimples on the fracture surface of aluminum alloy tensile specimens
1.一種韌窩的外形大而深，說(shuō)明5052鋁合金屬于韌性斷裂；
1. The shape of a dimple is large and deep, indicating that 5052 aluminum alloy belongs to ductile fracture;
2.二種韌窩外形較小，在韌窩的底部和四周分布著一定量的球形顆粒，說(shuō)明5052鋁合金有部分脆性斷裂。由于二種韌窩比例較少，因此5052鋁合金的主要斷裂機(jī)制屬于韌性斷裂。
2. The shape of the two dimples is small, and a certain amount of spherical particles are distributed at the bottom and around the dimple, indicating that 5052 aluminum alloy has partial brittle fracture. Due to the small proportion of the two dimples, the main fracture mechanism of 5052 aluminum alloy belongs to ductile fracture.
三、鋁合金球頭脹形仿真與試驗(yàn)結(jié)果
3、 Simulation and experimental results of aluminum alloy ball joint bulging
板料在成形至斷裂的過(guò)程中出現(xiàn)了明顯的頸縮，宏觀斷口表現(xiàn)為沿著與厚度方向成45°方向斷裂，開(kāi)裂部位斷口比較平整，沒(méi)有出現(xiàn)不規(guī)則的起伏，板料厚度在刃口附近出現(xiàn)了明顯的減薄。有限元仿真結(jié)果與試驗(yàn)結(jié)果較吻合，板料開(kāi)裂處裂紋的位置和形狀大小與試驗(yàn)結(jié)果接近。
During the process from forming to fracture, the sheet metal has obvious necking. The macro fracture is broken along the 45 ° direction with the thickness direction. The fracture of the cracked part is relatively flat without irregular fluctuation. The sheet metal thickness has obvious thinning near the edge. The finite element simulation results are in good agreement with the experimental results, and the location, shape and size of the crack at the plate crack are close to the experimental results.
四、鋁板成型開(kāi)裂結(jié)論
4、 Aluminum sheet forming cracking conclusion
1)對(duì)鋁合金板進(jìn)行了單向拉伸試驗(yàn)，使用Voce模型對(duì)試驗(yàn)應(yīng)力應(yīng)變曲線(xiàn)進(jìn)行了擬合。將Cockcroft-Latham韌性斷裂準(zhǔn)則引入到單向拉伸有限元模型中，結(jié)合試驗(yàn)結(jié)果，反求了5052鋁合金材料失效參數(shù)。
1) The uniaxial tensile test of aluminum alloy plate was carried out, and the test stress-strain curve was fitted by voce model. The Cockcroft Latham ductile fracture criterion is introduced into the unidirectional tensile finite element model. Combined with the test results, the failure parameters of 5052 aluminum alloy are inversely calculated.
2)采用擬合的Voce模型參數(shù)和韌性斷裂準(zhǔn)則參數(shù)對(duì)5052鋁合金板料球頭脹形開(kāi)裂進(jìn)行了仿真預(yù)測(cè)，并進(jìn)行試驗(yàn)驗(yàn)證，結(jié)果表明仿真預(yù)測(cè)板料開(kāi)裂位置及裂口形狀與試驗(yàn)結(jié)果吻合。
2) The bulging cracking of 5052 aluminum alloy sheet metal ball joint is simulated and predicted by using the fitted voce model parameters and ductile fracture criterion parameters, and the experimental verification is carried out. The results show that the simulation prediction of sheet metal cracking position and crack shape are consistent with the experimental results.
3)使用該方法進(jìn)行鋁合金板料的成形開(kāi)裂極限預(yù)測(cè)具有材料參數(shù)求解方便，計(jì)算精度高的優(yōu)點(diǎn)，可為相關(guān)研究提供參考。
3) Using this method to predict the forming cracking limit of aluminum alloy sheet has the advantages of convenient solution of material parameters and high calculation accuracy, which can provide reference for relevant research.