本文選題：金屬體積成形 + 彈塑性大變形��； 參考：《湘潭大學》2016年碩士論文

【摘要】：金屬體積成形是目前加工金屬零件的一種重要手段,其成形過程為大變形過程,涉及幾何非線性和材料非線性問題,必須借助數(shù)值方法來求解。物質(zhì)點法作為一種新型無網(wǎng)格數(shù)值模擬方法,它即可以克服有限元法網(wǎng)格畸變問題,同時也有效地避免了傳統(tǒng)無網(wǎng)格法的計算量大、本質(zhì)邊界條件施加困難、質(zhì)點影響域搜索費時等不足。本文將物質(zhì)點法應用于三維金屬體積成形問題的數(shù)值模擬研究,分別對自由鐓粗和反向擠壓兩種金屬體積成形過程進行了數(shù)值模擬研究,并與有限元法及傳統(tǒng)無網(wǎng)格伽遼金法模擬結果進行了對比,探討了物質(zhì)點法在模擬金屬體積成形過程的可行性和有效性。具體內(nèi)容為:采用加權余量法推導了物質(zhì)點法控制方程的弱形式及其離散格式,給出了物質(zhì)點法的顯式計算流程;結合金屬彈塑性理論與物質(zhì)點法建立了金屬彈塑性物質(zhì)點法求解格式;利用Fortran語言編寫了相應的計算程序,通過算例驗證了彈塑性物質(zhì)點法和程序的正確性;從計算效率、計算精度以及不同離散質(zhì)點數(shù)下的計算結果等方面將物質(zhì)點法與有限元法、無網(wǎng)格伽遼金法進行了對比研究。結果表明物質(zhì)點法的計算精度和效率與有限元法相當,而高于無網(wǎng)格伽遼金法,并且在質(zhì)點數(shù)目發(fā)生改變時表現(xiàn)出了比無網(wǎng)格伽遼金法更高的穩(wěn)定性。基于物質(zhì)點法對金屬坯料自由鐓粗和反向擠壓的三維金屬體積成形過程進行了數(shù)值模擬研究。在自由鐓粗的模擬中,分別對無摩擦接觸及有摩擦接觸等情況進行了仿真分析,并與實驗、有限元法的結果進行了對比,結果吻合良好,表明了本文利用物質(zhì)點法計算三維金屬體積成形問題時的可行性和有效性。在反向擠壓成形模擬中,分別對不同壓下量時坯料變形流動規(guī)律以及等效應力和等效應變的變化規(guī)律進行研究,并與有限元法以及無網(wǎng)格伽遼金法進行了對比,結果表明,當壓下量較小時,物質(zhì)點法與有限元法均能較好地模擬成形過程,但當壓下量較大時有限元網(wǎng)格產(chǎn)生了嚴重的畸變而導致計算終止,而物質(zhì)點法計算不受影響,能一次完成整個過程的計算,并與無網(wǎng)格伽遼金法結果吻合,可見在模擬金屬體積成形大變形問題時,物質(zhì)點法相比于有限元法具有更大的優(yōu)勢。本文的研究為物質(zhì)點法應用于其它金屬體積成形過程的數(shù)值模擬研究提供一定的指導作用。
[Abstract]:Metal bulk forming is an important method for machining metal parts at present. Its forming process is a large deformation process, which involves geometric nonlinearity and material nonlinearity. It must be solved by numerical method. As a new meshless numerical simulation method, the material point method can not only overcome the mesh distortion problem of the finite element method, but also effectively avoid the complexity of the traditional meshless method and the difficulties imposed by the essential boundary conditions. Particle impact domain search time and other deficiencies. In this paper, the material point method is applied to the numerical simulation of three dimensional metal volume forming, and two kinds of metal volume forming processes, free upsetting and reverse extrusion, are numerically simulated, respectively. Compared with the finite element method and the traditional Galerkin meshless method, the feasibility and effectiveness of the material point method in simulating the metal bulk forming process are discussed. The main contents are as follows: the weak form and the discrete scheme of the control equation of the material point method are derived by using the weighted residual method, and the explicit calculation flow of the material point method is given. Combining the metal elastoplastic theory with the material point method, the solution format of the metal elastoplastic material point method is established, the corresponding calculation program is compiled by using Fortran language, and the correctness of the elastic-plastic material point method and the program is verified by an example. In terms of calculation accuracy and calculation results under different discrete particle numbers, the material point method is compared with the finite element method and the meshless Galerkin method. The results show that the computational accuracy and efficiency of the material point method are similar to that of the finite element method, but higher than that of the meshless Galerkin method, and it is more stable than the meshless Galerkin method when the particle number changes. Based on the material point method, the numerical simulation of three dimensional metal volume forming process of free upsetting and reverse extrusion of metal billet was carried out. In the simulation of free upsetting, the non-friction contact and the friction-free contact are simulated and analyzed, and the results of the finite element method are compared with the experimental results, and the results are in good agreement with each other. The feasibility and effectiveness of the material point method in the calculation of three-dimensional metal volume forming problem are demonstrated in this paper. In the simulation of reverse extrusion, the deformation flow law, equivalent stress and equivalent strain of the billet with different reduction are studied, and the results are compared with the finite element method and the Galerkin method without meshes. When the reduction is small, both the material point method and the finite element method can simulate the forming process well, but when the reduction is large, the finite element mesh has serious distortion, which leads to the termination of the calculation, but the material point method is not affected. The calculation of the whole process can be completed in one time, and the results are in agreement with the results of the meshless Galerkin method. It is shown that the material point method has more advantages than the finite element method in simulating the large deformation problem of metal bulk forming. The research in this paper provides some guidance for the application of material point method in the numerical simulation of other metal bulk forming processes.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG302

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