發(fā)布時(shí)間：2022-11-12 09:08

　　眾所周知,零部件在循環(huán)疲勞載荷作用下,其疲勞失效通常起始于最表層應(yīng)力集中位置的裂紋區(qū)域。通過噴丸強(qiáng)化和激光沖擊強(qiáng)化等技術(shù)將殘余應(yīng)力引入材料的表層可以延緩疲勞裂紋萌生和擴(kuò)展,從而提高部件的疲勞壽命以及抗磨損和應(yīng)力腐蝕開裂（SCC）性能。激光沖擊過程中,由等離子沖擊破產(chǎn)生的塑性變形可以在材料表面誘導(dǎo)產(chǎn)生殘余應(yīng)力。由于AA2024-T351鋁合金在航空航天工業(yè)領(lǐng)域中重要作用,研究殘余應(yīng)力對(duì)該材料疲勞性能的影響,從而達(dá)到抑制疲勞失效,提高疲勞壽命的目的是有必要的。因此,本文的研究題目是激光沖擊強(qiáng)化（LSP）對(duì)AA2024-T351鋁合金殘余應(yīng)力分布和疲勞壽命的影響,創(chuàng)新性的提出了一種梯度式的掃描策略來優(yōu)化激光噴丸過程中脈沖掃描路徑。采用三維有限元分析（FEA）法模擬殘余應(yīng)力分布,并建立模擬和實(shí)驗(yàn)結(jié)果的關(guān)系。利用優(yōu)化的有限元模型預(yù)測了激光沖擊過程中,梯度式掃描策略和常規(guī)掃描策略對(duì)殘余應(yīng)力分布的影響,并通過實(shí)驗(yàn)進(jìn)行了驗(yàn)證。利用兩種掃描策略在“骨棒”試樣上進(jìn)行激光沖擊強(qiáng)化實(shí)驗(yàn),并將兩種激光沖擊試樣的疲勞壽命與未沖擊試樣進(jìn)行對(duì)比,結(jié)果表明激光沖擊強(qiáng)化可以提高材料的疲勞壽命。與未沖擊試樣相比,策略1試樣... 

【文章頁數(shù)】：148 頁

【學(xué)位級(jí)別】：博士

【文章目錄】：
ABSTRACT
摘要
DEDICATION
CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW
    1.1 Introduction
    1.2 Literature Review
        1.2.1 Severe plastic deformation(SPD)methods
        1.2.2 Laser shock peening and its processing parameters on metals materials
    1.3 Literature Summary
    1.4 Research Objectives
    1.5 Dissertation Outline
CHAPTER 2 EXPERIMENTAL MATERIAL AND METHODS
    2.1 Properties of Aluminum alloys(AA)
    2.2 Material Preparation
    2.3 Laser Shock Peening(LSP)
    2.4 Microhardness and specimen preparation
        2.4.1 Microhardness measurement
        2.4.2 Microhardness specimen preparation
        2.4.3 Scanning electron microscope(SEM)
        2.4.4 SEM specimen preparation
        2.4.5 Optical microscope(OM)
    2.5 Surface roughness and topography
    2.6 X-ray diffraction analysis
    2.7 Residual measurement
    2.8 Transmission electron microscope(TEM)
    2.9 Fatigue Test
    2.10 Tensile test
    2.11 LSP and simulation
    2.12 Modelling pressure loading and plastic deformation due to shockwaves
    2.13 Thin and thick geometry
    2.14 Material simulation model
    2.15 LSP and its processing parameters on AA2024-T351 aluminum alloy
CHAPTER 3 THE EFFECTS OF SCANNING PATH GRADIENT ON THE COMPRESSIVE RESIDUAL STRESS DISTRIBUTION AND FATIGUE LIFE BY LSP
    3.1 Introduction
    3.2 FE simulation and compressive residual stress distribution
        3.2.1 Strategy1:Scanning path gradient parallel to fatigue load
        3.2.2 Strategy2:Scanning path in advancing direction to fatigue load
    3.3 Results and discussion
    3.4 Residual stress distribution comparative to experimental and simulated results
        3.4.1 Strategy 1
        3.4.2 Strategy 2
    3.5 Fatigue life improvement
    3.6 Fatigue fracture
    3.7 SUMMARY
CHAPTER 4 THE EFFECTS OF LASER ENERGY ON FATIGUE BEHAVIOR INDUCED BY LASER SHOCK PEENED(LSP)ON AA2024-T351 ALUMINUM ALLOY
    4.1 Introduction
    4.2 Experimental details
    4.3 Results and discussion
        4.3.1 Effect of pulse energy on residual stress
        4.3.2 Effect pulse energy on microhardness
    4.4 Fatigue fracture analysis
    4.5 Fatigue crack behavior and microstructure on the fractured surfaces
    4.6 Fatigue life
    4.7 SUMMARY
CHAPTER 5 THE EFFECTS OF MULTIPLE PEENING ON FATIGUE LIFE AND SURFACE INTEGRITY ON AA2024-T351 ALUMINUM ALLOY WITH LSP
    5.1 Introduction
    5.2 Experimental materials and methods
    5.3 Results and discussion
        5.3.1 Tensile properties
        5.3.2 Fracture analysis
        5.3.3 TEM observation
    5.4 Effects of multiple LSP impacts on mechanical properties
        5.4.1 XRD diffraction and phase analysis
        5.4.2 Residual stress distribution
        5.4.3 Microhardness analysis
        5.4.4 Surface roughness analysis
    5.5 Fatigue life and fracture surfaces
        5.5.1 Fatigue life
        5.5.2 Fatigue fracture
    5.6 SUMMARY
CHAPTER 6 CONCLUSIONS AND RECOMMENDATION
    6.1 CONCLUSIONS
        6.1.1 The effects of scanning path gradient direction on residual stress distribution and fatigue life induced by LSP
        6.1.2 The effects of different laser energy of fatigue behavior and residual stress distribution induced by LSP
        6.1.3 The effects of multiple peening on fatigue life and surface integrity on AA2024-T351 aluminum alloy with LSP
    6.2 NOVELTY CONTRIBUTION
    6.3 FUTURE RESEARCH WORK
REFERENCES
ACKNOWLEDGEMENT
PUBLICATIONS


【參考文獻(xiàn)】：
期刊論文
[1]Numerical simulation of residual stress field induced by laser shock processing with square spot[J]. 曹子文,車志剛,鄒世坤,費(fèi)群星.  Journal of Shanghai University（English Edition）. 2011(06)
[2]約束層對(duì)激光驅(qū)動(dòng)沖擊波壓力影響機(jī)理的理論研究[J]. 顧永玉,張永康,張興權(quán),史建國.  物理學(xué)報(bào). 2006(11)
[3]激光沖擊處理降低鋁合金裂紋擴(kuò)展速率的研究[J]. 鄒世坤 ,王健 ,王華明 ,韓海軍 ,王春生.  航空制造技術(shù). 2002(09)



本文編號(hào)：3706091