發(fā)布時(shí)間：2018-06-23 08:48

  本文選題：2198鋁鋰合金板材 + 成形極限圖(FLD)��； 參考：《南昌航空大學(xué)》2015年碩士論文

【摘要】：2198鋁鋰合金作為第三代鋁鋰合金,具有很高的比強(qiáng)度、比剛度和質(zhì)量輕,同時(shí)具有較好的抗腐蝕性和抗疲勞性以及適宜的延展性,受到了航空工業(yè)的廣泛關(guān)注。然而,該合金板材在變形過(guò)程中,變形抗力對(duì)變形溫度和變形速率很敏感,室溫成形性能差,導(dǎo)致成形困難。研究2198鋁鋰合金板材在溫?zé)釕B(tài)的成形性能,并建立其成形極限圖,對(duì)我國(guó)新型航空材料板材的研究和應(yīng)用都有重要意義。成形極限圖(Forming Limit Diagram)也稱成形極限曲線(Forming Limit Curves),通常用FLD或FLC表示。FLD或FLC是評(píng)判板材成形性能最為簡(jiǎn)便和直觀的方法,可以用來(lái)預(yù)測(cè)和判斷板材沖壓工藝的成敗,協(xié)助制定沖壓工藝的參數(shù),是有效解決沖壓工藝問(wèn)題的一種工具。成形極限曲線位置的高低反映了材料在各種應(yīng)力狀態(tài)下局部極限變形能力的大小,其位置越高則材料的成形性能越好。最近幾年,FLD被國(guó)內(nèi)外學(xué)者廣泛應(yīng)用于第一代和第二代鋁鋰合金板材綜合成形性能評(píng)價(jià)。而對(duì)第三代鋁鋰合金板材FLD研究還較少。因此本文通過(guò)FLD試驗(yàn)的方法研究第三代鋁鋰合金2198鋁鋰合金在溫?zé)釥顟B(tài)下的成形極限。采用北航研制的板料熱成形機(jī)BCS-50AR以及網(wǎng)格應(yīng)變自動(dòng)測(cè)量系統(tǒng)VIALUX Guto Grid,在25℃~350℃溫度范圍內(nèi)進(jìn)行2198鋁鋰合金板材的成形極限試驗(yàn),研究成形溫度、凸模速度、應(yīng)力狀態(tài)對(duì)2198鋁鋰合金板材的成形性能的影響;借助OM、SEM、TEM等微觀手段對(duì)分析2198鋁鋰合金板材在相應(yīng)溫度下的成形后的微觀組織形態(tài)和變化進(jìn)行了表述。研究表明成形溫度對(duì)2198鋁鋰合金板材成形極限圖影響很大,成形極限曲線的高度隨成形溫度的升高而提高,板材的塑性顯著提高。在25℃時(shí),凸模速度對(duì)2198鋁鋰合金板材成形性能影響很小,但受應(yīng)力狀態(tài)的影響很大;然而在300℃~350℃溫度和凸模速度對(duì)2198鋁鋰合金板材成形性能影響增大,而受應(yīng)力狀態(tài)影響減小。微觀組織分析表明,2198鋁鋰合金板材在25℃下成形時(shí)斷口有明顯的分層斷裂的特征,并帶有少量韌窩。在350℃下成形時(shí)2198鋁鋰合金板材斷口有大量孔洞,孔洞隨著變形時(shí)間的延長(zhǎng)不斷增大,同時(shí)在高溫下2198鋁鋰合金板材會(huì)出現(xiàn)動(dòng)態(tài)再結(jié)晶�；诔尚螛O限試驗(yàn),以M-K理論為基礎(chǔ),結(jié)合Swift和Hill兩種屈服準(zhǔn)則成功預(yù)測(cè)了2198鋁鋰合金板材在溫?zé)岘h(huán)境中的成形極限圖,通過(guò)對(duì)比得到不同溫度下基于這兩種屈服準(zhǔn)則進(jìn)行的2198鋁鋰合金板材成形極限圖預(yù)測(cè)較為理想的屈服參數(shù),獲得2198鋁鋰合金板材在不同溫度下較為理想的成形極限圖理論計(jì)算模型,對(duì)促進(jìn)2198鋁鋰合金板材在實(shí)際生產(chǎn)工藝規(guī)范的制定提供理論支持。
[Abstract]:As the third generation Al-Li alloy, 2198 Al-Li alloy has high specific strength, light specific stiffness and mass, good corrosion resistance, fatigue resistance and suitable ductility. However, during deformation, the deformation resistance of the alloy sheet is sensitive to the deformation temperature and the deformation rate, and the forming performance is poor at room temperature, which leads to the difficulty of forming. It is of great significance for the research and application of new aeronautical material sheet in China to study the formability of 2198 Al-Li alloy sheet in warm state and to establish its forming limit diagram. Forming limit Diagram is also called forming limit Curves. It is usually expressed by FLD or FLC. FLD or FLC is the most convenient and intuitionistic method to evaluate sheet metal formability, which can be used to predict and judge the success or failure of sheet metal stamping process. To assist in the development of stamping process parameters, is an effective solution to stamping process problems. The position of the forming limit curve reflects the local ultimate deformation ability of the material under various stress conditions, and the higher the position, the better the formability of the material. In recent years, FLD has been widely used by scholars at home and abroad to evaluate the comprehensive forming properties of the first and second generation Al-Li alloy sheet. But the third generation aluminum lithium alloy sheet FLD research is still less. In this paper, the forming limit of the third generation Al-Li alloy 2198 is studied by means of FLD test. Using BCS-50AR and VIALUX Guto griddle, the forming limit test of 2198 Al-Li alloy sheet was carried out in the temperature range of 25 鈩，

本文編號(hào)：2056560