本文選題：熔融沉積成型 + 熱傳導(dǎo)方程組�。� 參考：《昆明理工大學(xué)》2017年碩士論文

【摘要】：熔融沉積成型(FDM)技術(shù)是近幾十年來在國內(nèi)外應(yīng)用逐漸廣泛的一種快速原型制造技術(shù),可以較好地適應(yīng)制造領(lǐng)域競爭的全球化,用戶需求的個性化和多樣化,降低生產(chǎn)成本,提高生產(chǎn)效率,快速響應(yīng)市場的變化需求。熔融沉積成型技術(shù)是基于離散/堆積原理,由二維截面逐層成型三維實體,易產(chǎn)生階梯效應(yīng),產(chǎn)生翹曲變形等缺陷。成型過程中溫度場的變化情況與應(yīng)力場及應(yīng)變場等直接相關(guān),對翹曲變形等缺陷有重要影響,成型過程的傳熱分析是非常有必要的。成型過程中,表面換熱系數(shù)是傳熱分析研究的一個必不可少的邊界條件。目前,對熔融沉積成型過程中表面換熱系數(shù)的研究較為匱乏,而不準確的換熱系數(shù)嚴重地影響傳熱過程的分析研究,進而嚴重地影響各種缺陷的分析研究。熔融沉積成型過程中表面換熱系數(shù)的研究已經(jīng)勢在必行。本文基于熱力學(xué)第一定律和能量守恒定律以及其他相關(guān)理論,對熔融沉積成型過程傳熱問題進行分析研究,建立了相關(guān)的數(shù)學(xué)模型,基于有限差分法和傳熱學(xué)等相關(guān)理論,考慮了材料熱物理性能參數(shù)變化以及內(nèi)熱源和性態(tài)轉(zhuǎn)變潛熱的影響,推導(dǎo)出熔融沉積成型過程的傳熱控制方程組。本文對傳熱控制方程組進行有限差分格式替代,結(jié)合非線性迭代估算原理,提出了熔融沉積成型過程表面換熱系數(shù)的反問題求解思路,利用MATLAB軟件編寫出熔融沉積成型過程表面換熱系數(shù)的反求程序,求解出表面換熱系數(shù)隨時間和溫度的變化規(guī)律,以及有限差分劃分不同節(jié)點處溫度隨時間的變化值。在成型實驗過程中,利用溫度采集系統(tǒng)測出成型件一些節(jié)點位置的溫度值,通過比對驗證與反求程序中相同節(jié)點處溫度計算值與實測值之間的關(guān)系,得出反求程序的合理性和有效性。本文通過對熔融沉積過程成型特點的分析,提出合理假設(shè),建立有限元模型,對熔融沉積成型過程進行傳熱分析。利用ANSYS有限元分析軟件中“生死單元”技術(shù),結(jié)合成型實驗過程中實際的掃描方式和掃描速度,通過APDL參數(shù)化設(shè)計語言進行編程,并將求解得到的表面換熱系數(shù)作為邊界條件代入,求解出模型的溫度場變化情況,不同時刻的溫度梯度分布圖,以及不同節(jié)點處溫度隨時間變化情況,對應(yīng)力場和應(yīng)變場等提供了一定的理論依據(jù)。模擬結(jié)果與實際情況較為相符,表明所求表面換熱系數(shù)有效。
[Abstract]:Fused deposition molding (FDM) is a kind of rapid prototyping technology which has been widely used in recent decades. It can adapt to the globalization of manufacturing competition, the individuation and diversification of user demand, and reduce the production cost. Improve production efficiency and respond quickly to changing market demands. The melt deposition technology is based on the discrete / stacking principle. The 3D solid is formed by two dimensional cross section layer by layer. It is easy to produce step effect and warp deformation and so on. The variation of temperature field is directly related to the stress field and strain field, and has an important effect on the warping and deformation. It is necessary to analyze the heat transfer during the molding process. The surface heat transfer coefficient is an essential boundary condition for heat transfer analysis. At present, the study of surface heat transfer coefficient in the process of melt deposition molding is relatively scarce, but the inaccurate heat transfer coefficient seriously affects the analysis and research of heat transfer process, and then seriously affects the analysis and study of various defects. It is imperative to study the surface heat transfer coefficient in the process of melt deposition forming. Based on the first law of thermodynamics, the law of conservation of energy and other relevant theories, this paper analyzes and studies the heat transfer in the process of melt deposition molding, and establishes the relevant mathematical model, which is based on the theory of finite difference method and heat transfer, etc. The heat transfer control equations of the melt deposition molding process are derived considering the change of the material thermal physical properties parameters and the effects of the internal heat source and the latent heat transfer of the property state. In this paper, the finite difference scheme is used to replace the heat transfer control equations. Combining with the nonlinear iterative estimation principle, the inverse problem of surface heat transfer coefficient in the process of melt deposition molding is proposed. The inverse program of surface heat transfer coefficient in melt deposition molding process is compiled by using MATLAB software. The variation law of surface heat transfer coefficient with time and temperature and the variation value of temperature with time at different nodes are solved. In the process of forming experiment, the temperature values of some nodes are measured by the temperature acquisition system, and the relationship between the calculated and measured values at the same node in the program is verified by comparison. The rationality and validity of the reverse procedure are obtained. Based on the analysis of the forming characteristics of the melt deposition process, a reasonable hypothesis is put forward and a finite element model is established to analyze the heat transfer of the melt deposition forming process. Using the technology of "birth and death element" in ANSYS finite element analysis software, combined with the actual scanning mode and scanning speed in the process of forming experiment, the programming is carried out by APDL parameterized design language. The calculated surface heat transfer coefficient is used as boundary condition to calculate the temperature field of the model, the temperature gradient distribution at different time, and the temperature variation at different nodes with time. The corresponding force field and strain field provide some theoretical basis. The simulation results are in good agreement with the actual situation and show that the calculated surface heat transfer coefficient is effective.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TH16

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