本文選題：修正函數(shù) + 屈服準(zhǔn)則��； 參考：《北方工業(yè)大學(xué)》2015年碩士論文

【摘要】：現(xiàn)有的屈服準(zhǔn)則基本上都是應(yīng)力的全局變量函數(shù),在對屈服軌跡預(yù)測時(shí)不同加載路徑間會相互影響,為了提高預(yù)測的準(zhǔn)確性現(xiàn)有屈服準(zhǔn)則都是通過在原有屈服準(zhǔn)則的基礎(chǔ)上進(jìn)行變換,或采用高次的沒有物理意義的函數(shù)形式來使計(jì)算結(jié)果更加逼近試驗(yàn)點(diǎn)。本課題在八面體剪應(yīng)力與加載路徑有關(guān)的規(guī)律基礎(chǔ)上對初始屈服軌跡進(jìn)行分片處理,然后基于隨動(dòng)強(qiáng)化思想對Hi1148屈服準(zhǔn)則在二維主應(yīng)力空間閉合的屈服軌跡進(jìn)行分片上的修正建模,以得到新的屈服軌跡,并通過常用的單向拉伸實(shí)驗(yàn)和雙向拉伸實(shí)驗(yàn)來獲得屈服準(zhǔn)則的參數(shù)值,是建立各向異性屈服準(zhǔn)則的一類新思路。 針對新屈服準(zhǔn)則中修正函數(shù)系數(shù)的求解設(shè)計(jì)了單向加載試件(單向拉伸和平面應(yīng)變)、雙向拉伸試件及其對應(yīng)的加載方向與軋制方向成一定角度的實(shí)驗(yàn)方案,且所有實(shí)驗(yàn)方案在現(xiàn)有的實(shí)驗(yàn)條件下都可以較容易的完成。對于其他不容易得到的實(shí)驗(yàn)數(shù)據(jù)進(jìn)行了合理假設(shè)或通過其他屈服模型計(jì)算得到。 為了驗(yàn)證所提出的新屈服準(zhǔn)則的可靠性和普遍適用性,本課題選取了拉壓對稱情況下常用的鋁合金材料2024-o和5754M以及兩種鋼板SPEN和BH220；拉壓不對稱情況下的三種常見晶體金屬板料：密排六方晶體(HCP)的AZ31B Mg合金、體心立方晶體(BCC)的中碳低合金鋼、面心立方晶體(FCC)的2090T3鋁合金,將新屈服函數(shù)計(jì)算結(jié)果與實(shí)驗(yàn)數(shù)據(jù)進(jìn)行比較。為了研究與現(xiàn)有各向異性屈服準(zhǔn)則預(yù)測結(jié)果的差異,選取了Barlat2000、Hosford針對AA6022T4、090T3、Al-2.5wt%Mg等拉壓對稱材料進(jìn)行了計(jì)算結(jié)果的比較,選取了公認(rèn)比較準(zhǔn)確的CPB06ex02模型對AZ31B、中碳低合金鋼等材料的屈服軌跡計(jì)算結(jié)果與新屈服函數(shù)計(jì)算結(jié)果進(jìn)行了比較。結(jié)果表明：新屈服準(zhǔn)則對上述材料的屈服軌跡預(yù)測結(jié)果都有較高的準(zhǔn)確性,即滿足可靠性和適用性,且與其他現(xiàn)有屈服準(zhǔn)則的計(jì)算結(jié)果具有較高的一致性。 在實(shí)際板料成形過程中,板料經(jīng)常處于含有剪切應(yīng)力的復(fù)雜應(yīng)力狀態(tài)中,即主應(yīng)力方向與軋制方向不重合,所以在二維主應(yīng)力空間中建立的屈服準(zhǔn)則不能對該種情況進(jìn)行描述,對此將所需的用于求解分片上修正函數(shù)系數(shù)的特征點(diǎn)實(shí)驗(yàn)值寫成主應(yīng)力方向與軋制方向所成角度的傅里葉函數(shù),并將這種方法對各向異性參數(shù)的描述能力與Hi1148和Barlat89的計(jì)算結(jié)果進(jìn)行了比較。 將提出的新屈服準(zhǔn)則編寫成用戶材料子程序(UMAT),嵌入到有限元仿真軟件ABAQUS中,對雙向加載比例分別為4：1和4：4的雙拉試驗(yàn)進(jìn)行仿真,并與實(shí)驗(yàn)結(jié)果進(jìn)行比較,發(fā)現(xiàn)新屈服準(zhǔn)則成功嵌入到有限元軟件ABAQUS中,且計(jì)算結(jié)果較為準(zhǔn)確、子程序運(yùn)行穩(wěn)定。
[Abstract]:The existing yield criterion is basically a global variable function of stress, and the different loading paths will affect each other in predicting the yield trajectory. In order to improve the accuracy of prediction, the existing yield criteria are based on the original yield criteria, or the higher order function without physical meaning is used to make the calculation results closer to the test point. Based on the law of octahedron shear stress and loading path, the initial yield trajectory is processed in pieces. Then, based on the following strengthening theory, the Hi1148 yield criterion is modified on the closed yield trajectory in the two-dimensional principal stress space to obtain a new yield trajectory. The parameter values of yield criterion are obtained by uniaxial and biaxial tensile tests, which is a new way to establish anisotropic yield criterion. Aiming at the solution of the modified function coefficient in the new yield criterion, the experimental scheme of unidirectional loading specimen (uniaxial tension and plane strain), biaxial tensile specimen and its corresponding loading direction and rolling direction are designed. And all the experimental schemes can be easily completed under the existing experimental conditions. Other experimental data which are not easily obtained are reasonably assumed or calculated by other yield models. In order to verify the reliability and universal applicability of the proposed new yield criterion, The AZ31B mg alloy of aluminum alloy materials 2024-o and 5754M, two kinds of steel plates SPEN and BH220, and three kinds of common crystal metal sheet: dense hexagonal crystal (HCP), are selected in this paper, which are commonly used in the case of tension and compression symmetry, such as 2024-o and 5754M, and two kinds of steel plates, such as SPEN and BH220. The new yield function calculation results of 2090T3 aluminum alloy of BCC medium carbon low alloy steel and face centered cubic crystal FCCs are compared with experimental data. In order to study the difference between the prediction results of anisotropic yield criterion and that of existing anisotropic yield criteria, Barlat200n Hosford was selected to compare the calculated results for AA6022T4090T3 / Al-2.5wtMg and other tensile and compression symmetric materials. The calculated results of yield trajectories of AZ31B and medium carbon low alloy steels are compared with the results of the new yield function. The results show that the new yield criterion has a high accuracy in predicting the yield trajectories of the materials mentioned above, that is, it satisfies the reliability and applicability, and is in good agreement with the calculated results of other existing yield criteria. In the actual sheet metal forming process, the sheet metal is often in the complex stress state with shear stress, that is, the principal stress direction does not coincide with the rolling direction, so the yield criterion established in the two-dimensional principal stress space can not describe this kind of situation. For this reason, the experimental results of the characteristic points used to solve the coefficients of the correction function on the chip are written as Fourier functions of the angle between the principal stress direction and the rolling direction. The ability of describing anisotropic parameters by this method is compared with that of Hi1148 and Barlat89. The new yield criterion is programmed into user material subprogram and embedded into the finite element simulation software ABAQUS. The double tension test with bidirectional loading ratio of 4:1 and 4:4 is simulated, and the results are compared with the experimental results. It is found that the new yield criterion is successfully embedded in the finite element software ABAQUS, and the calculation results are more accurate and the subprogram runs stably.
【學(xué)位授予單位】：北方工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG381

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