本文選題：高強度鋼 + 熱成形��； 參考：《吉林大學》2017年碩士論文

【摘要】：材料沖壓成形CAE仿真模擬時通常采用成形極限圖(FLD)來評價。高強度鋼熱成性技術(shù)的發(fā)展決定了研究高溫成形極限圖的必要性。國際標準所規(guī)定的獲取成形極限圖的方法都是針對冷成型而言的,目前尚缺乏熱成形標準。熱成形延用沖壓形式的冷成形試驗標準,模具材料潤滑度均受到限制。除此之外,高溫下材料的成形性能與溫度和應(yīng)變率均相關(guān),一條成形極限曲線FLC是無法評價的,需要多條成形極限曲線才能進行成形性能分析。本文提出了一種獲取高溫成形極限圖新的試驗方法—雙向拉伸試驗方法。設(shè)計了一種可以將單向拉伸轉(zhuǎn)變?yōu)殡p向拉伸的裝置,并且提出了一種適合高溫操作環(huán)境下連接處轉(zhuǎn)動的絕緣方案。本文引入損傷因子作為評判失效的參數(shù),建立自定義材料模型,利用LS-DYNA有限元模擬拉伸過程,分別設(shè)計了獲取左右兩側(cè)成形極限曲線試件形狀。再利用對試件關(guān)鍵尺寸的設(shè)計,改變拉伸時主次應(yīng)變方向材料的流動狀態(tài),進而改變應(yīng)變路徑,最終設(shè)計出一組試件,可以獲取不同應(yīng)變路徑下的成形極限點。通過雙向拉伸試驗得到了700℃和800℃兩個溫度下成形極限圖中等軸雙向拉伸應(yīng)變狀態(tài)、平面應(yīng)變狀態(tài)、過渡應(yīng)變狀態(tài)等5個試驗點,同時驗證了新試驗方法的正確性。建立了基于粘塑性損傷力學22Mn B5高溫雙軸損傷本構(gòu)模型,利用遺傳算法擬合方程中材料參數(shù),確定了FLD預(yù)測模型。并且通過與試驗數(shù)據(jù)對比,驗證了FLD預(yù)測模型的有效性。本文利用FLD預(yù)測模型預(yù)測了22Mn B5在應(yīng)變率為0.1/s時,600℃、650℃、700℃、750℃、800℃、850℃的成形極限曲線,預(yù)測了22Mn B5在溫度為800℃下,應(yīng)變率分別為0.01/s,0.1/s,1/s的成形極限曲線。隨著溫度的升高和應(yīng)變率的降低,成形極限圖FLD的位置升高,即22Mn B5板料的成形性能隨溫度的升高和應(yīng)變率的降低而提高。
[Abstract]:Forming limit Diagram (FLD) is usually used to evaluate material forming CAE simulation. The development of high strength steel thermogenicity technology determines the necessity of studying high temperature forming limit diagram. The method of obtaining forming limit diagram stipulated by international standard is for cold forming, but there is no hot forming standard at present. The cold forming test standard for hot forming, the lubrication degree of die material is limited. In addition, the formability of materials at high temperature is related to temperature and strain rate. One forming limit curve (FLC) can not be evaluated, and many forming limit curves are needed to analyze the formability. In this paper, a new test method for obtaining the high temperature forming limit diagram, the biaxial tensile test method, is presented. A device is designed to convert uniaxial tension to biaxial tension, and an insulation scheme suitable for rotation of joints under high temperature operating conditions is proposed. In this paper, the damage factor is introduced as the parameter to evaluate the failure, and the self-defined material model is established. The tensile process is simulated by LS-DYNA finite element method, and the shape of the specimen obtained from the left and right sides of the forming limit curve is designed respectively. By designing the key dimensions of the specimen, the flow state of the material in the direction of primary and secondary strain is changed, and the strain path is changed. Finally, a set of specimens are designed to obtain the forming limit points under different strain paths. Through the biaxial tensile test, five test points such as biaxial tensile strain state, plane strain state and transition strain state in the forming limit diagram at 700 鈩，

本文編號：1940702