本文選題：鈦合金棒材　切入點：有限元模擬　出處：《太原科技大學(xué)》2017年碩士論文

【摘要】：鈦合金棒材產(chǎn)品是國民經(jīng)濟(jì)領(lǐng)域中的關(guān)鍵工程材料,具有高的機(jī)械強(qiáng)度和韌性,同時具備良好的冷加工工藝性能,以滿足后續(xù)加工的要求。然而,由于目前鈦合金產(chǎn)品生產(chǎn)過程中存在裂紋或者斷裂的缺陷,使得產(chǎn)品成材率較低,本文通過損傷分析對裂紋的產(chǎn)生進(jìn)行了預(yù)測,從而降低了鈦合金生產(chǎn)過程中的損耗率。本文制定了合理的三輥連軋TC4棒材的工藝制度,用有限元軟件模擬棒材損傷值,對連軋過程中裂紋敏感區(qū)進(jìn)行預(yù)測,并研究不同工藝參數(shù)對棒材最大損傷值的影響。改進(jìn)了連軋孔型系統(tǒng),在三輥熱連軋機(jī)組上進(jìn)行了相關(guān)試驗,獲得了幾何尺寸精確、表面質(zhì)量好的試樣,隨后進(jìn)行了微觀組織觀察。具體研究內(nèi)容如下:(1)利用Deform有限元模擬技術(shù),對棒材三輥熱連軋過程中的損傷值分布進(jìn)行了模擬,通過對比,確定了損傷值最大的區(qū)域,即與軋輥接觸的區(qū)域,此區(qū)域金屬變形最大;比較了軋輥偏角、摩擦因數(shù)、溫度對棒材最大損傷值的影響,為后續(xù)參數(shù)優(yōu)化提供理論基礎(chǔ);采用CA模型,線性擬合了位錯密度模型、動態(tài)再結(jié)晶模型等,進(jìn)一步模擬了最大損傷區(qū)域晶粒的組織演變。(2)基于斷裂力學(xué)理論,對適用于低溫與等溫的Ayada損傷模型進(jìn)行了優(yōu)化,考慮了軋制溫度(850℃、900℃、950℃、1000℃)、應(yīng)變速率(0.01 s-1、0.1s-1、1s-1)的影響,推導(dǎo)了TC4鈦合金高溫累積損傷值的數(shù)學(xué)模型;并比較了模擬損傷值與計算損傷值的計算偏差,最大偏差值為9%。(3)孔型連軋穩(wěn)定是實現(xiàn)產(chǎn)品順利變形的關(guān)鍵,在傳統(tǒng)孔型基礎(chǔ)上,采用正交分析法與有限元模擬,以降低棒材橫截面溫度梯度、減小表面裂紋為目標(biāo),優(yōu)化了“多線段三角—圓”孔型系統(tǒng),確定了第一道次、第三道次凸起軋槽的最佳幾何尺寸,即,第一道次長軸長4.30mm,短軸長0.80mm,第二道次長軸長3.34mm,短軸長0.80mm。(4)在三輥熱連軋機(jī)組上進(jìn)行了TC4棒材軋制試驗,獲得了幾何尺寸精確、表面質(zhì)量好的試樣,進(jìn)一步確認(rèn)了新型孔型的優(yōu)越性;隨后微觀組織觀察發(fā)現(xiàn),在軋制第三道次,棒材組織開始發(fā)生組織轉(zhuǎn)變,即由細(xì)條狀逐漸轉(zhuǎn)變?yōu)榈容S狀,這與有限元模擬結(jié)果相吻合。說明本文制定的工藝參數(shù)、設(shè)備參數(shù)是合理的,從而為同類金屬材料軋制提供可靠的技術(shù)依據(jù)。
[Abstract]:Titanium alloy bar is a key engineering material in the field of national economy. It has high mechanical strength and toughness, and has good cold processing performance to meet the requirements of subsequent processing. Due to the defects of crack or fracture in the process of titanium alloy production at present, the yield of finished product is low. In this paper, the production of crack is predicted by damage analysis. In order to reduce the loss rate of titanium alloy in the process of production, a reasonable process system of three-roll continuous rolling TC4 bar is established in this paper. The damage value of the bar is simulated by finite element software, and the crack sensitive zone in continuous rolling process is predicted. The influence of different process parameters on the maximum damage value of the bar was studied. The pass system of continuous rolling was improved, and the related tests were carried out on the three high hot strip mill. The samples with accurate geometry and good surface quality were obtained. Then the microstructure was observed. The specific research contents are as follows: (1) using Deform finite element simulation technology, the damage value distribution in the process of three-roll hot continuous rolling of bar is simulated. By comparison, the region with the largest damage value is determined. The influence of roll angle, friction coefficient and temperature on the maximum damage value of the bar is compared, which provides the theoretical basis for the optimization of the following parameters. The dislocation density model and dynamic recrystallization model are fitted linearly, and the microstructure evolution of grain in the maximum damage region is further simulated. Based on the theory of fracture mechanics, the Ayada damage model suitable for low temperature and isothermal temperature is optimized. Considering the influence of rolling temperature (850 鈩，

本文編號：1654909