發(fā)布時間：2018-01-22 00:56

  本文關(guān)鍵詞： 液壓成形 沖擊 本構(gòu)關(guān)系 遺傳算法 有限元模擬　出處：《桂林電子科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：基于輕量化和一體化特征開發(fā)的管材液壓成形技術(shù)(THF),具有成本低、成形零件質(zhì)量好、節(jié)約材料等優(yōu)點(diǎn),正獲得快速發(fā)展。然而,在實際生產(chǎn)應(yīng)用中發(fā)現(xiàn),THF存在制造過程繁瑣、成形難度大、成形效率較低等缺點(diǎn)。沖擊液壓成形(Liquid Impact Forming,LIF)是在液壓脹形和沖壓成形基礎(chǔ)上發(fā)展起來的一種新型復(fù)合成形技術(shù),它利用壓力機(jī)上下模具閉合時的徑向壓管運(yùn)動,使管材內(nèi)部液體自發(fā)產(chǎn)生內(nèi)壓力而快速填充模具型腔,完成脹形過程,以此甩掉復(fù)雜的液壓系統(tǒng)而大幅降低管材成形的成本和周期。高精度的管材塑性本構(gòu)關(guān)系不僅對管材成形機(jī)理的分析具有重要影響,而且是有限元數(shù)值模擬的重要前提。因此,本文對沖擊液壓載荷作用下管材的動態(tài)塑性本構(gòu)關(guān)系進(jìn)行研究具有重要意義。本文研究的主要內(nèi)容包括:(1)分析本構(gòu)關(guān)系的基礎(chǔ)理論和材料的應(yīng)變速率響應(yīng),根據(jù)管材沖擊液壓成形的受力條件,選定管材沖擊液壓成形的動態(tài)塑性本構(gòu)模型。(2)對SS304不銹鋼管材進(jìn)行不同速度的沖擊液壓成形試驗,通過應(yīng)變在線測量系統(tǒng)對管材脹形區(qū)的動態(tài)變化數(shù)據(jù)進(jìn)行在線測量,根據(jù)試驗數(shù)據(jù)計算輪廓上的軸向曲率半徑和周向半徑。(3)基于上述試驗變形數(shù)據(jù),先用一般線性回歸法,求解兩種本構(gòu)模型的參數(shù);然后研究根據(jù)遺傳算法的收斂特點(diǎn),求解管材沖擊液壓條件下的兩種塑性本構(gòu)關(guān)系。(4)基于DYNAFORM和ANSYS Workbench聯(lián)合仿真,建立管材沖擊液壓成形的有限元模型,分別將線性回歸法和遺傳算法得到的管材塑性本構(gòu)關(guān)系作為材料模型,對管材沖擊液壓成形過程分別進(jìn)行有限元模擬,通過試驗結(jié)果與模擬結(jié)果的對比,來檢驗所構(gòu)建出沖擊液壓成形條件下管材的動態(tài)塑性本構(gòu)關(guān)系的精度。研究表明:(1)本文提出的動態(tài)塑性本構(gòu)關(guān)系,從應(yīng)變速率角度研究沖擊載荷作用下金屬薄壁管準(zhǔn)確的塑性本構(gòu)關(guān)系。通過模擬結(jié)果與試驗結(jié)果對比,表明本文構(gòu)建的動態(tài)塑性本構(gòu)關(guān)系具有較高的精度。(2)根據(jù)模擬結(jié)果的最大脹形高度與試驗的結(jié)果對比,可以定量地得出J-C本構(gòu)模型最大誤差范圍在7.43%以內(nèi),F-B本構(gòu)模型最大誤差范圍在8.65%以內(nèi),表明J-C本構(gòu)模型更適合描述管材沖擊液壓脹形時的塑性硬化關(guān)系。(3)根據(jù)驗證結(jié)果,線型回歸法確定的本構(gòu)模型誤差均大于遺傳算法確定的本構(gòu)模型的誤差,表明遺傳算法具有穩(wěn)定且快速收斂的優(yōu)點(diǎn),能夠在變量空間中找出包含最優(yōu)解和極值的單峰值區(qū)域并搜索最優(yōu)解,在擬合復(fù)雜目標(biāo)函數(shù)時具有明顯優(yōu)勢。(4)隨著沖擊速度的提高,仿真結(jié)果的誤差逐漸減小,表明本文確定的動態(tài)塑性本構(gòu)關(guān)系適應(yīng)于沖擊速度較大的管材液壓成形。本課題研究成果提供了一種沖擊液壓載荷作用下管材動態(tài)塑性本構(gòu)關(guān)系的構(gòu)建方法,對LIF的其他研究和有限元模擬具有一定的借鑒和指導(dǎo)作用。
[Abstract]:The tube hydroforming technology based on lightweight and integrated features is developing rapidly, which has the advantages of low cost, good quality of forming parts and saving materials. It is found that the manufacturing process is cumbersome, the forming is difficult and the forming efficiency is low in the practical application. The impact hydroforming is liquid Impact Forming. Lif is a new compound forming technology developed on the basis of hydraulic bulging and stamping forming. It utilizes the radial pressure tube movement of the upper and lower die closure of the press. The liquid inside the tube spontaneously produces the internal pressure and fills the mold cavity quickly to complete the bulging process. In this way, the cost and cycle of tube forming can be greatly reduced by getting rid of the complicated hydraulic system. The high precision plastic constitutive relation of pipe not only has an important influence on the analysis of forming mechanism of pipe. And it is an important premise of finite element numerical simulation. In this paper, it is of great significance to study the dynamic plastic constitutive relations of pipes under hydraulic impact loading. The main contents of this paper include: 1). The basic theory of constitutive relation and the strain rate response of materials are analyzed. According to the stress condition of pipe impact hydroforming, the dynamic plastic constitutive model of pipe impact hydroforming was selected. The dynamic change data of tube bulging region are measured online by the strain on-line measurement system. Based on the experimental data, the axial curvature radius and circumferential radius on the profile are calculated. (3) based on the above experimental deformation data. First, the general linear regression method is used to solve the parameters of the two constitutive models. Then according to the convergence characteristics of genetic algorithm. The two kinds of plastic constitutive relation under hydraulic pressure condition of pipe impingement are solved. The simulation is based on DYNAFORM and ANSYS Workbench. The finite element model of tube impact hydroforming is established. The plastic constitutive relation of pipe obtained by linear regression method and genetic algorithm is taken as the material model, respectively, and the process of tube impact hydroforming is simulated by finite element method. By comparing the experimental results with the simulation results, the accuracy of the dynamic plastic constitutive relationship of the pipe under the condition of impact hydroforming is tested. The study shows that the dynamic plastic constitutive relation proposed in this paper is the first. The accurate plastic constitutive relationship of metal thin-walled tubes under impact loading is studied from the strain rate angle. The simulation results are compared with the experimental results. It is shown that the dynamic plastic constitutive relationship constructed in this paper has a high accuracy. (2) the maximum bulging height of the simulation results is compared with the experimental results. The maximum error range of J-C constitutive model is within 7.43% and the maximum error range of F-B constitutive model is 8.65%. The results show that J-C constitutive model is more suitable to describe the plastic hardening relationship of pipe under hydraulic bulging. The error of constitutive model determined by linear regression method is larger than that of constitutive model determined by genetic algorithm, which indicates that genetic algorithm has the advantages of stable and fast convergence. The region of single peak value including the optimal solution and extreme value can be found in the variable space and the optimal solution can be searched. It has obvious advantage in fitting the complex objective function with the increase of the impact velocity. The error of simulation results decreases gradually. The results show that the dynamic plastic constitutive relationship is suitable for the tube hydroforming with high impact speed. This paper provides a method to construct the dynamic plastic constitutive relationship of the pipe under the impact hydraulic load. It can be used for reference and guidance to other LIF research and finite element simulation.
【學(xué)位授予單位】：桂林電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG306

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