發(fā)布時(shí)間：2023-05-28 10:50

　　粉末注射成形過程包括四個(gè)階段：混料、注射、脫脂和燒結(jié)。本論文主要對(duì)微注射成形和微波燒結(jié)兩個(gè)工藝過程展開研究：修正和補(bǔ)充了用于模擬注射填充過程的數(shù)值算法；實(shí)現(xiàn)表面張力效應(yīng)的計(jì)算與評(píng)估；以17-4PH不銹鋼粉末成形件為樣品進(jìn)行微波燒結(jié)實(shí)驗(yàn)研究；在微波加熱和熱傳導(dǎo)模擬的基礎(chǔ)上,補(bǔ)充粉末材料的燒結(jié)致密化模型,實(shí)現(xiàn)了微波燒結(jié)多物理場耦合現(xiàn)象的數(shù)值模擬。為提高注射成形過程數(shù)值模擬結(jié)果的準(zhǔn)確性,本論文修改和補(bǔ)充了用于注射填充過程的全矢量顯式模擬算法。針對(duì)填充流在復(fù)雜形狀模腔中流向失真的問題,本論文采用類似迎風(fēng)法的概念,修正了空氣流動(dòng)速度場對(duì)填料填充的不真實(shí)影響,有效抑制了填充流向的失真現(xiàn)象。建議了補(bǔ)充合理邊界條件的數(shù)值方法,修正不可壓縮流體在填充末段出現(xiàn)的非線性填充延遲現(xiàn)象,并驗(yàn)證了該方法的有效性。為了拓展研究組內(nèi)自行開發(fā)的有限元模擬軟件,使其適用于模擬微注射成形問題,本論文在原有注射成形模擬算法的基礎(chǔ)上,實(shí)現(xiàn)了表面張力計(jì)算和模擬功能。由于沒有針對(duì)有限元法的適當(dāng)算法,本文建議并實(shí)施了一種系統(tǒng)化操作的算法,實(shí)現(xiàn)了填充前沿面曲率的計(jì)算,進(jìn)而求解得到表面張力值。應(yīng)用植入表面張力功能的軟件,模擬了一系列典型...

【文章頁數(shù)】：157 頁

【學(xué)位級(jí)別】：博士

【文章目錄】：
摘要
Abstract
Resume
Glossary
Nomenclature
Introduction
Chapter 1 State of the art
    1.1 Brief introduction of PIM
    1.2 The advantages of PIM
    1.3 PIM development and market
    1.4 The principal research centers in PIM processing
    1.5 Researches on PIM process in France and in China
Chapter 2 Developments of modified algorithms for Mold Filling Process
    2.1 Modeling and Simulation of PIM injection
        2.1.1 General Definition
        2.1.2 Governing Equations
        2.1.3 Explicit algorithm for simulation
    2.2 Algorithm for improvement of wrongly adverted filling profile
        2.2.1 The source for distorted simulation results
        2.2.2 Modification of the solution procedure
        2.2.3 Validation of the modification scheme
        2.2.4 Conclusion
    2.3 The outlet condition in simulation of MIM injection to track the end of filling process
        2.3.1 The inexact result at the end of filling process
        2.3.2 Modification of the outlet boundary condition
        2.3.3 Validation of the modified algorithm
        2.3.4 Conclusion
Chapter 3 Numerical method and analysis for surface tension effects in micro-injectionprocess
    3.1 Mechanical modeling
    3.2 Surface tension force
    3.3 Implementation of Surface tension in FEM
        3.3.1 Surface curvature computation
        3.3.2 Surface tension force in computation
    3.4 Numerical investigation and discussion
    3.5 Conclusion
Chapter 4 Brief Introduction and Foundational Theories for Sintering
    4.1 Introduction of sintering
        4.1.1 Berif introduction of sintering
    4.2 Foundational Theories for Sintering
        4.2.1 Driving Forces of Sintering
        4.2.2 Sintering Mechanisms
        4.2.3 Stages of Sintering
    4.3 Models and Simulations of Sintering
        4.3.1 Simulation history
        4.3.2 Three sintering models
Chapter 5 Efficient sintering of 17-4PH stainless steel powder by microwave
    5.1 Research background
    5.2 Experimental procedure
    5.3 Results and discussion
        5.3.1 Specimen sizes after being injected, debinded and MW sintered
        5.3.2 The influence factors in MW sintering process
        5.3.3 Microstructure
        5.3.4 Distribution of the Vickers-hardness
        5.3.5 Comparison with the conventional sintering
        5.3.6 Conclusions
Chapter 6 Mathematical Modeling and Simulation of Microwave Sintering Process
    6.1 Research Background
    6.2 Mathematical model of microwave sintering
        6.2.1 Solve Maxwell equation to get electromagnetic fields in cavity of the furnace
        6.2.2 Solve for distribution of the heat generation in process of microwave sintering
        6.2.3 Solution of heat transfer equation to get temperature field in the sintered body
        6.2.4 Solve the governing equations of sintering densification to get the structural response of sintered body
        6.2.5 Coupling of the Maxwell equation, heat transfer equation and mechanic equations
    6.3 Numerical simulation of microwave sintering process
        6.3.1 Modeling of Microwave Sintering
        6.3.2 Numerical analysis
    6.4 Conclusion and outlook
Chapter 7 Conclusions and Perspectives
    7.1 Conclusions
    7.2 Future Work
Acknowledgement
References
Publications



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