IF鋼成形極限的研究
發(fā)布時間：2018-11-17 19:05
【摘要】：IF鋼作為第三代深沖鋼材因其優(yōu)異的塑性變形能力,被廣泛應用于汽車中的一些變形程度比較大的難成形零件。IF鋼的使用從某種程度上代表了一個國家的汽車工業(yè)水平的高低。我國汽車工業(yè)雖然已經(jīng)度過了發(fā)展最快的時期,但仍然處在一個高速發(fā)展的階段,對IF鋼的需求量很大。但一些汽車零部件廠并沒有對所使用板材的成形極限進行研究,致使工藝分析與模具設計缺少判據(jù)。因此,研究IF鋼的成形極限,充分利用其塑性成形性能,進而優(yōu)化成形工藝,提高汽車沖壓件質(zhì)量具有重要研究意義和價值。成形極限是板材塑性變形過程中在不失穩(wěn)的前提下達到最大應變的極限狀態(tài),是衡量板材成形性能的重要指標之一。通過實驗獲取成形極限圖國內(nèi)、外都指定由相應的標準,但從試樣設計、制備到實驗后的真實應變測量和數(shù)據(jù)處理都耗時費力,不便于應用。本文以DX54D+Z為例,通過成形極限的實驗研究、理論分析和數(shù)值模擬,探討用理論分析和成形模擬仿真方法快速獲取IF鋼成形極限圖的途徑。在實驗研究方面,根據(jù)《金屬薄板成形性能實驗-成形極限圖(FLD)實驗》的規(guī)定,制作了矩形與階梯形9組(27件)試樣,矩形試樣用于獲取“拉-拉區(qū)”的應變數(shù)據(jù),階梯形試樣用于獲取“拉-壓區(qū)”應變數(shù)據(jù);采用電化學腐蝕法在板材上印制網(wǎng)格;利用杯突試驗機完成成形實驗;利用GMASystem系統(tǒng)進行網(wǎng)格應變自動測量;最終完成實驗成形極限圖的繪制,為后續(xù)理論分析與成形模擬提供參考。在理論分析上,基于M-K凹槽理論,利用Logan-Hosford屈服準則和Rossard硬化方程,建立了板材成形極限預測數(shù)學模型,結(jié)合弦截法迭代求解,通過MATLAB軟件對DX54D+Z的成形極限圖進行了理論預測。在此基礎上,分析了不同屈服準則、應變強化指數(shù)、應變速率敏感系數(shù)和厚度不均值對理論預測的影響。在成形模擬方面,應用DYNAFORM軟件對標準埃里克森杯突實驗過程進行成形模擬。但由于有限元軟件沒有失穩(wěn)判據(jù)判斷材料破壞或是虛擬實驗停止的時間節(jié)點,本文在分析應力應變狀態(tài)的基礎上,提出極限狀態(tài)的判據(jù),對比分析了不同判據(jù)的使用范圍,并預測了IF鋼的成形極限圖,討論了實驗工藝參數(shù)對基于成形模擬預測結(jié)果的影響。最后,將理論和成形模擬成形極限圖與實驗成形極限圖進行對比,驗證了理論和模擬方法的可行性和結(jié)果的正確性,為零部件廠商在實際生產(chǎn)中快速獲取成形極限圖提供了新的途徑。
[Abstract]:As the third generation deep drawing steel, IF steel has excellent plastic deformation ability. The use of IF steel represents the level of automobile industry in a country to a certain extent. Although the automobile industry of our country has passed the period of the fastest development, it is still in a stage of high speed development, and the demand for IF steel is very large. However, some automobile parts factories do not study the forming limit of the sheet metal used, which leads to the lack of criteria for process analysis and die design. Therefore, it is of great significance and value to study the forming limit of IF steel, make full use of its plastic formability, optimize the forming process and improve the quality of automotive stamping parts. Forming limit is the limit state of the maximum strain in the process of sheet metal plastic deformation, and it is one of the important indexes to evaluate the forming performance of sheet metal. At home and abroad, the corresponding standard is assigned to obtain the forming limit diagram by experiment. However, from sample design, preparation to the real strain measurement and data processing after experiment, it is time-consuming and difficult to apply. In this paper, taking DX54D Z as an example, through the experimental study, theoretical analysis and numerical simulation of the forming limit, the way to obtain the forming limit diagram of IF steel quickly by theoretical analysis and simulation method is discussed. In the aspect of experimental study, according to the rule of "sheet metal formability experiment-forming limit diagram (FLD) experiment", 9 groups of rectangular and stepped specimens (27 pieces) were made. The rectangular specimen was used to obtain the strain data of "pull-pull zone". The step specimen is used to obtain the strain data of "tension and compression zone"; The electrochemical etching method is used to print the mesh on the sheet metal, the forming experiment is completed by the cupping test machine, and the mesh strain is measured automatically by GMASystem system. Finally, the drawing of the experimental forming limit diagram is completed, which provides a reference for the subsequent theoretical analysis and forming simulation. Based on M-K grooves theory and Logan-Hosford yield criterion and Rossard hardening equation, a mathematical model of sheet metal forming limit prediction is established. The forming limit diagram of DX54D Z is predicted by MATLAB software. On this basis, the effects of different yield criteria, strain strengthening exponent, strain rate sensitivity coefficient and thickness non-mean on the theoretical prediction are analyzed. In the aspect of forming simulation, DYNAFORM software is used to simulate the standard Eriksson cupping process. But because the finite element software does not have the instability criterion to judge the time node of material failure or virtual experiment stop, based on the analysis of stress-strain state, the criterion of limit state is put forward, and the application range of different criterion is compared and analyzed. The forming limit diagram of IF steel is predicted and the influence of experimental process parameters on the prediction results based on forming simulation is discussed. Finally, the theoretical and simulated forming limit diagrams are compared with the experimental forming limit diagrams to verify the feasibility of the theory and simulation methods and the correctness of the results. It provides a new way for parts manufacturers to obtain rapid forming limit diagram in actual production.
【學位授予單位】：武漢理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG301;TG142.1
本文編號：2338776
[Abstract]:As the third generation deep drawing steel, IF steel has excellent plastic deformation ability. The use of IF steel represents the level of automobile industry in a country to a certain extent. Although the automobile industry of our country has passed the period of the fastest development, it is still in a stage of high speed development, and the demand for IF steel is very large. However, some automobile parts factories do not study the forming limit of the sheet metal used, which leads to the lack of criteria for process analysis and die design. Therefore, it is of great significance and value to study the forming limit of IF steel, make full use of its plastic formability, optimize the forming process and improve the quality of automotive stamping parts. Forming limit is the limit state of the maximum strain in the process of sheet metal plastic deformation, and it is one of the important indexes to evaluate the forming performance of sheet metal. At home and abroad, the corresponding standard is assigned to obtain the forming limit diagram by experiment. However, from sample design, preparation to the real strain measurement and data processing after experiment, it is time-consuming and difficult to apply. In this paper, taking DX54D Z as an example, through the experimental study, theoretical analysis and numerical simulation of the forming limit, the way to obtain the forming limit diagram of IF steel quickly by theoretical analysis and simulation method is discussed. In the aspect of experimental study, according to the rule of "sheet metal formability experiment-forming limit diagram (FLD) experiment", 9 groups of rectangular and stepped specimens (27 pieces) were made. The rectangular specimen was used to obtain the strain data of "pull-pull zone". The step specimen is used to obtain the strain data of "tension and compression zone"; The electrochemical etching method is used to print the mesh on the sheet metal, the forming experiment is completed by the cupping test machine, and the mesh strain is measured automatically by GMASystem system. Finally, the drawing of the experimental forming limit diagram is completed, which provides a reference for the subsequent theoretical analysis and forming simulation. Based on M-K grooves theory and Logan-Hosford yield criterion and Rossard hardening equation, a mathematical model of sheet metal forming limit prediction is established. The forming limit diagram of DX54D Z is predicted by MATLAB software. On this basis, the effects of different yield criteria, strain strengthening exponent, strain rate sensitivity coefficient and thickness non-mean on the theoretical prediction are analyzed. In the aspect of forming simulation, DYNAFORM software is used to simulate the standard Eriksson cupping process. But because the finite element software does not have the instability criterion to judge the time node of material failure or virtual experiment stop, based on the analysis of stress-strain state, the criterion of limit state is put forward, and the application range of different criterion is compared and analyzed. The forming limit diagram of IF steel is predicted and the influence of experimental process parameters on the prediction results based on forming simulation is discussed. Finally, the theoretical and simulated forming limit diagrams are compared with the experimental forming limit diagrams to verify the feasibility of the theory and simulation methods and the correctness of the results. It provides a new way for parts manufacturers to obtain rapid forming limit diagram in actual production.
【學位授予單位】：武漢理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG301;TG142.1
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